multidecadal internal variability: Topics by Science.gov

NAO and its relationship with the Northern Hemisphere mean surface temperature in CMIP5 simulations

NASA Astrophysics Data System (ADS)

Wang, Xiaofan; Li, Jianping; Sun, Cheng; Liu, Ting

2017-04-01

The North Atlantic Oscillation (NAO) is one of the most prominent teleconnection patterns in the Northern Hemisphere and has recently been found to be both an internal source and useful predictor of the multidecadal variability of the Northern Hemisphere mean surface temperature (NHT). In this study, we examine how well the variability of the NAO and NHT are reproduced in historical simulations generated by the 40 models that constitute Phase 5 of the Coupled Model Intercomparison Project (CMIP5). All of the models are able to capture the basic characteristics of the interannual NAO pattern reasonably well, whereas the simulated decadal NAO patterns show less consistency with the observations. The NAO fluctuations over multidecadal time scales are underestimated by almost all models. Regarding the NHT multidecadal variability, the models generally represent the externally forced variations well but tend to underestimate the internal NHT. With respect to the performance of the models in reproducing the NAO-NHT relationship, 14 models capture the observed decadal lead of the NAO, and model discrepancies in the representation of this linkage are derived mainly from their different interpretation of the underlying physical processes associated with the Atlantic Multidecadal Oscillation (AMO) and the Atlantic meridional overturning circulation (AMOC). This study suggests that one way to improve the simulation of the multidecadal variability of the internal NHT lies in better simulation of the multidecadal variability of the NAO and its delayed effect on the NHT variability via slow ocean processes.
Forced Atlantic Multidecadal Variability Over the Past Millennium

NASA Astrophysics Data System (ADS)

Halloran, P. R.; Reynolds, D.; Scourse, J. D.; Hall, I. R.

2016-02-01

Paul R. Halloran, David J. Reynolds, Ian R. Hall and James D. Scourse Multidecadal variability in Atlantic sea surface temperatures (SSTs) plays a first order role in determining regional atmospheric circulation and moisture transport, with major climatic consequences. These regional climate impacts range from drought in the Sahel and South America, though increased hurricane activity and temperature extremes, to modified monsoonal rainfall. Multidecadal Atlantic SST variability could arise through internal variability in the Atlantic Meridional Overturning Circulation (AMOC) (e.g., Knight et al., 2006), or through externally forced change (e.g. Booth et al., 2012). It is critical that we know whether internal or external forcing dominates if we are to provide useful near-term climate projections in the Atlantic region. A persuasive argument that internal variability plays an important role in Atlantic Multidecadal Variability is that periodic SST variability has been observed throughout much of the last millennium (Mann et al., 2009), and the hypothesized external forcing of historical Atlantic Multidecadal Variability (Booth et al., 2012) is largely anthropogenic in origin. Here we combine the first annually-resolved millennial marine reconstruction with multi-model analysis, to show that the Atlantic SST variability of the last millennium can be explained by a combination of direct volcanic forcing, and indirect, forced, AMOC variability. Our results indicate that whilst climate models capture the timing of both the directly forced SST and forced AMOC-mediated SST variability, the models fail to capture the magnitude of the forced AMOC change. Does this mean that models underestimate the 21st century reduction in AMOC strength? J. Knight, C. Folland and A. Scaife., Climate impacts of the Atlantic Multidecadal Oscillation, GRL, 2006 B.B.B Booth, N. Dunstone, P.R. Halloran et al., Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability, Nature, 2012 M.E. Mann, Z. Zhang, S. Rutherford et al., Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly, Science, 2009
Inability of CMIP5 Climate Models to Simulate Recent Multi-decadal Climate Change in the Tropical Pacific.

NASA Astrophysics Data System (ADS)

Power, S.; Delage, F.; Kociuba, G.; Wang, G.; Smith, I.

2017-12-01

Observed 15-year surface temperature trends beginning 1998 or later have attracted a great deal of interest because of an apparent slowdown in the rate of global warming, and contrasts between climate model simulations and observations of such trends. Many studies have addressed the statistical significance of these relatively short trends, whether they indicate a possible bias in models and the implications for global warming generally. Here we analyse historical and projected changes in 38 CMIP5 climate models. All of the models simulate multi-decadal warming in the Pacific over the past half-century that exceeds observed values. This stark difference cannot be fully explained by observed, internal multi-decadal climate variability, even if allowance is made for an apparent tendency for models to underestimate internal multi-decadal variability in the Pacific. We also show that CMIP5 models are not able to simulate the magnitude of the strengthening of the Walker Circulation over the past thirty years. Some of the reasons for these major shortcomings in the ability of models to simulate multi-decadal variability in the Pacific, and the impact these findings have on our confidence in global 21st century projections, will be discussed.
Pronounced differences between observed and CMIP5-simulated multidecadal climate variability in the twentieth century

NASA Astrophysics Data System (ADS)

Kravtsov, Sergey

2017-06-01

Identification and dynamical attribution of multidecadal climate undulations to either variations in external forcings or to internal sources is one of the most important topics of modern climate science, especially in conjunction with the issue of human-induced global warming. Here we utilize ensembles of twentieth century climate simulations to isolate the forced signal and residual internal variability in a network of observed and modeled climate indices. The observed internal variability so estimated exhibits a pronounced multidecadal mode with a distinctive spatiotemporal signature, which is altogether absent in model simulations. This single mode explains a major fraction of model-data differences over the entire climate index network considered; it may reflect either biases in the models' forced response or models' lack of requisite internal dynamics, or a combination of both.Plain Language SummaryGlobal and regional warming trends over the course of the twentieth century have been nonuniform, with decadal and longer periods of faster or slower warming, or even cooling. Here we show that state-of-the-art global models used to predict climate fail to adequately reproduce such multidecadal climate variations. In particular, the models underestimate the magnitude of the observed variability and misrepresent its spatial pattern. Therefore, our ability to interpret the observed climate change using these models is limited. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53D2286S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53D2286S">Internally Generated and Externally Forced Multidecadal Oceanic Modes and their Influence on the Summer Rainfall over East Asia</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Si, D.; Hu, A. 2017-12-01 The interdecadal oceanic variabilities can be generated from both internal and external processes, and these variabilities can significantly modulate our climate on global and regional scale, such as the warming slowdown in the early 21st century, and the rainfall in East Asia. By analyzing simulations from a unique Community Earth System Model (CESM) Large Ensemble (CESM_LE) project, we show that the Interdecadal Pacific Oscillation (IPO) is primarily an internally generated oceanic variability, while the Atlantic Multidecadal Oscillation (AMO) may be an oceanic variability generated by internal oceanic processes and modulated by external forcings in the 20th century. Although the observed relationship between IPO and the Yangtze-Huaihe River valley (YHRV) summer rainfall in China is well simulated in both the preindustrial control and 20th century ensemble, none of the 20th century ensemble members can reproduce the observed time evolution of both IPO and YHRV due to the unpredictable nature of IPO on multidecade timescale. On the other hand, although CESM_LE cannot reproduce the observed relationship between AMO and Huanghe River valley (HRV) summer rainfall of China in the preindustrial control simulation, this relationship in the 20th century simulations is well reproduced, and the chance to reproduce the observed time evolution of both AMO and HRV rainfall is about 30%, indicating the important role of the interaction between the internal processes and the external forcing to realistically simulate the AMO and HRV rainfall. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23345448','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23345448">Using data to attribute episodes of warming and cooling in instrumental records.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tung, Ka-Kit; Zhou, Jiansong 2013-02-05 The observed global-warming rate has been nonuniform, and the cause of each episode of slowing in the expected warming rate is the subject of intense debate. To explain this, nonrecurrent events have commonly been invoked for each episode separately. After reviewing evidence in both the latest global data (HadCRUT4) and the longest instrumental record, Central England Temperature, a revised picture is emerging that gives a consistent attribution for each multidecadal episode of warming and cooling in recent history, and suggests that the anthropogenic global warming trends might have been overestimated by a factor of two in the second half of the 20th century. A recurrent multidecadal oscillation is found to extend to the preindustrial era in the 353-y Central England Temperature and is likely an internal variability related to the Atlantic Multidecadal Oscillation (AMO), possibly caused by the thermohaline circulation variability. The perspective of a long record helps in quantifying the contribution from internal variability, especially one with a period so long that it is often confused with secular trends in shorter records. Solar contribution is found to be minimal for the second half of the 20th century and less than 10% for the first half. The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07-0.08 °C/decade, with superimposed AMO-related ups and downs that included the early 20th century warming, the cooling of the 1960s and 1970s, the accelerated warming of the 1980s and 1990s, and the recent slowing of the warming rates. Quantitatively, the recurrent multidecadal internal variability, often underestimated in attribution studies, accounts for 40% of the observed recent 50-y warming trend. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3568361','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3568361">Using data to attribute episodes of warming and cooling in instrumental records</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Tung, Ka-Kit; Zhou, Jiansong 2013-01-01 The observed global-warming rate has been nonuniform, and the cause of each episode of slowing in the expected warming rate is the subject of intense debate. To explain this, nonrecurrent events have commonly been invoked for each episode separately. After reviewing evidence in both the latest global data (HadCRUT4) and the longest instrumental record, Central England Temperature, a revised picture is emerging that gives a consistent attribution for each multidecadal episode of warming and cooling in recent history, and suggests that the anthropogenic global warming trends might have been overestimated by a factor of two in the second half of the 20th century. A recurrent multidecadal oscillation is found to extend to the preindustrial era in the 353-y Central England Temperature and is likely an internal variability related to the Atlantic Multidecadal Oscillation (AMO), possibly caused by the thermohaline circulation variability. The perspective of a long record helps in quantifying the contribution from internal variability, especially one with a period so long that it is often confused with secular trends in shorter records. Solar contribution is found to be minimal for the second half of the 20th century and less than 10% for the first half. The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07–0.08 °C/decade, with superimposed AMO-related ups and downs that included the early 20th century warming, the cooling of the 1960s and 1970s, the accelerated warming of the 1980s and 1990s, and the recent slowing of the warming rates. Quantitatively, the recurrent multidecadal internal variability, often underestimated in attribution studies, accounts for 40% of the observed recent 50-y warming trend. PMID:23345448 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5141387','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5141387">Prospects for a prolonged slowdown in global warming in the early 21st century</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Knutson, Thomas R.; Zhang, Rong; Horowitz, Larry W. 2016-01-01 Global mean temperature over 1998 to 2015 increased at a slower rate (0.1 K decade−1) compared with the ensemble mean (forced) warming rate projected by Coupled Model Intercomparison Project 5 (CMIP5) models (0.2 K decade−1). Here we investigate the prospects for this slower rate to persist for a decade or more. The slower rate could persist if the transient climate response is overestimated by CMIP5 models by a factor of two, as suggested by recent low-end estimates. Alternatively, using CMIP5 models' warming rate, the slower rate could still persist due to strong multidecadal internal variability cooling. Combining the CMIP5 ensemble warming rate with internal variability episodes from a single climate model—having the strongest multidecadal variability among CMIP5 models—we estimate that the warming slowdown (<0.1 K decade−1 trend beginning in 1998) could persist, due to internal variability cooling, through 2020, 2025 or 2030 with probabilities 16%, 11% and 6%, respectively. PMID:27901045 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.2487W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.2487W">Disentangling Global Warming, Multidecadal Variability, and El Niño in Pacific Temperatures</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wills, Robert C.; Schneider, Tapio; Wallace, John M.; Battisti, David S.; Hartmann, Dennis L. 2018-03-01 A key challenge in climate science is to separate observed temperature changes into components due to internal variability and responses to external forcing. Extended integrations of forced and unforced climate models are often used for this purpose. Here we demonstrate a novel method to separate modes of internal variability from global warming based on differences in time scale and spatial pattern, without relying on climate models. We identify uncorrelated components of Pacific sea surface temperature variability due to global warming, the Pacific Decadal Oscillation (PDO), and the El Niño-Southern Oscillation (ENSO). Our results give statistical representations of PDO and ENSO that are consistent with their being separate processes, operating on different time scales, but are otherwise consistent with canonical definitions. We isolate the multidecadal variability of the PDO and find that it is confined to midlatitudes; tropical sea surface temperatures and their teleconnections mix in higher-frequency variability. This implies that midlatitude PDO anomalies are more persistent than previously thought. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A21B0034B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A21B0034B">Interactive influence of the Atlantic and Pacific climates and their contribution to the multidecadal variations of global temperature and precipitation.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barcikowska, M. J.; Knutson, T. R.; Zhang, R. 2016-12-01 This study investigates mechanisms and global-scale climate impacts of multidecadal climate variability. Here we show, using observations and CSIRO-Mk3.6.0 model control run, that multidecadal variability of the Atlantic Meridional Overturning Circulation (AMOC) may have a profound impact on the thermal- and hydro-climatic changes over the Pacific region. In our model-based analysis we propose a mechanism, which comprises a coupled ocean-atmosphere teleconnection, established through the atmospheric overturning circulation cell between the tropical North Atlantic and tropical Pacific. For example, warming SSTs over the tropical North Atlantic intensify local convection and reinforce subsidence, low-level divergence in the eastern tropical Pacific. This is also accompanied with an intensification of trade winds, cooling and drying anomalies in the tropical central-east Pacific. The derived multidecadal changes, associated with the AMOC, contribute remarkably to the global temperature and precipitation variations. This highlights its potential predictive value. Shown here results suggest a possibility that: 1) recently observed slowdown in global warming may partly originate from internal variability, 2) climate system may be undergoing a transition to a cold AMO phase which could prolong the global slowdown. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS23D..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS23D..01H">Multi-decadal trend and space-time variability of sea level over the Indian Ocean since the 1950s: impact of decadal climate modes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Han, W.; Stammer, D.; Meehl, G. A.; Hu, A.; Sienz, F. 2016-12-01 Sea level varies on decadal and multi-decadal timescales over the Indian Ocean. The variations are not spatially uniform, and can deviate considerably from the global mean sea level rise (SLR) due to various geophysical processes. One of these processes is the change of ocean circulation, which can be partly attributed to natural internal modes of climate variability. Over the Indian Ocean, the most influential climate modes on decadal and multi-decadal timescales are the Interdecadal Pacific Oscillation (IPO) and decadal variability of the Indian Ocean dipole (IOD). Here, we first analyze observational datasets to investigate the impacts of IPO and IOD on spatial patterns of decadal and interdecadal (hereafter decal) sea level variability & multi-decadal trend over the Indian Ocean since the 1950s, using a new statistical approach of Bayesian Dynamical Linear regression Model (DLM). The Bayesian DLM overcomes the limitation of "time-constant (static)" regression coefficients in conventional multiple linear regression model, by allowing the coefficients to vary with time and therefore measuring "time-evolving (dynamical)" relationship between climate modes and sea level. For the multi-decadal sea level trend since the 1950s, our results show that climate modes and non-climate modes (the part that cannot be explained by climate modes) have comparable contributions in magnitudes but with different spatial patterns, with each dominating different regions of the Indian Ocean. For decadal variability, climate modes are the major contributors for sea level variations over most region of the tropical Indian Ocean. The relative importance of IPO and decadal variability of IOD, however, varies spatially. For example, while IOD decadal variability dominates IPO in the eastern equatorial basin (85E-100E, 5S-5N), IPO dominates IOD in causing sea level variations in the tropical southwest Indian Ocean (45E-65E, 12S-2S). To help decipher the possible contribution of external forcing to the multi-decadal sea level trend and decadal variability, we also analyze the model outputs from NCAR's Community Earth System Model (CESM) Large Ensemble Experiments, and compare the results with our observational analyses. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4438Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4438Y">Observations of Local Positive Low Cloud Feedback Patterns and Their Role in Internal Variability and Climate Sensitivity</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yuan, Tianle; Oreopoulos, Lazaros; Platnick, Steven E.; Meyer, Kerry 2018-05-01 Modeling studies have shown that cloud feedbacks are sensitive to the spatial pattern of sea surface temperature (SST) anomalies, while cloud feedbacks themselves strongly influence the magnitude of SST anomalies. Observational counterparts to such patterned interactions are still needed. Here we show that distinct large-scale patterns of SST and low-cloud cover (LCC) emerge naturally from objective analyses of observations and demonstrate their close coupling in a positive local SST-LCC feedback loop that may be important for both internal variability and climate change. The two patterns that explain the maximum amount of covariance between SST and LCC correspond to the Interdecadal Pacific Oscillation and the Atlantic Multidecadal Oscillation, leading modes of multidecadal internal variability. Spatial patterns and time series of SST and LCC anomalies associated with both modes point to a strong positive local SST-LCC feedback. In many current climate models, our analyses suggest that SST-LCC feedback strength is too weak compared to observations. Modeled local SST-LCC feedback strength affects simulated internal variability so that stronger feedback produces more intense and more realistic patterns of internal variability. To the extent that the physics of the local positive SST-LCC feedback inferred from observed climate variability applies to future greenhouse warming, we anticipate significant amount of delayed warming because of SST-LCC feedback when anthropogenic SST warming eventually overwhelm the effects of internal variability that may mute anthropogenic warming over parts of the ocean. We postulate that many climate models may be underestimating both future warming and the magnitude of modeled internal variability because of their weak SST-LCC feedback. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51L..03T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51L..03T">Forced and Internal Multi-Decadal Variability in the North Atlantic and their Climate Impacts</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ting, M. 2017-12-01 Atlantic Multidecadal Variability (AMV), a basin-wide North Atlantic sea surface temperature warming or cooling pattern varying on decadal and longer time scales, is one of the most important climate variations in the Atlantic basin. The AMV has shown to be associated with significant climate impacts regionally and globally, from Atlantic hurricane activities, frequency and severity of droughts across North America, as well as rainfall anomalies across the African Sahel and northeast Brazil. Despite the important impacts of the AMV, its mechanisms are not completely understood. In particular, it is not clear how much of the historical Atlantic SST fluctuations were forced by anthropogenic sources such as greenhouse warming and aerosol cooling, versus driven internally by changes in the coupled ocean-atmosphere processes in the Atlantic. Using climate models such as the NCAR large ensemble simulations, we were able to successfully separate the forced and internally generated North Atlantic sea surface temperature anomalies through a signal-to-noise maximizing Empirical Orthogonal Function (S/N EOF) analysis method. Two forced modes were identified with one representing a hemispherical symmetric mode and one asymmetric mode. The symmetric mode largely represents the greenhouse forced component while the asymmetric mode resembles the anthropogenic aerosol forcing. When statistically removing both of the forced modes, the residual multidecadal Atlantic SST variability shows a very similar structure as the AMV in the preindustrial simulation. The distinct climate impacts of each of these modes are also identified and the implications and challenges for decadal climate prediction will be discussed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=246635&Lab=NHEERL&keyword=oceanography&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=246635&Lab=NHEERL&keyword=oceanography&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Ecosystem Effects of the Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Multidecadal variability in the Atlantic Ocean and its importance to the Earth’s climate system has been the subject of study in the physical oceanography field for decades. Only recently, however, has the importance of this variability, termed the Atlantic Multidecadal Oscillati... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037464','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037464">Evidence of multidecadal climate variability and the Atlantic Multidecadal Oscillation from a Gulf of Mexico sea-surface temperature-proxy record</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Poore, R.Z.; DeLong, K.L.; Richey, J.N.; Quinn, T.M. 2009-01-01 A comparison of a Mg/Ca-based sea-surface temperature (SST)-anomaly record from the northern Gulf of Mexico, a calculated index of variability in observed North Atlantic SST known as the Atlantic Multidecadal Oscillation (AMO), and a tree-ring reconstruction of the AMO contain similar patterns of variation over the last 110 years. Thus, the multidecadal variability observed in the instrumental record is present in the tree-ring and Mg/Ca proxy data. Frequency analysis of the Gulf of Mexico SST record and the tree-ring AMO reconstruction from 1550 to 1990 found similar multidecadal-scale periodicities (???30-60 years). This multidecadal periodicity is about half the observed (60-80 years) variability identified in the AMO for the 20th century. The historical records of hurricane landfalls reveal increased landfalls in the Gulf Coast region during time intervals when the AMO index is positive (warmer SST), and decreased landfalls when the AMO index is negative (cooler SST). Thus, we conclude that alternating intervals of high and low hurricane landfall occurrences may continue on multidecadal timescales along the northern Gulf Coast. However, given the short length of the instrumental record, the actual frequency and stability of the AMO are uncertain, and additional AMO proxy records are needed to establish the character of multidecadal-scale SST variability in the North Atlantic. ?? 2009 US Government. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918288S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918288S">A propagating freshwater mode in the Arctic Ocean with multidecadal time scale</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schmith, Torben; Malskær Olsen, Steffen; Margrethe Ringgaard, Ida 2017-04-01 We apply Principal Oscillatory Pattern analysis to the Arctic Ocean fresh water content as simulated in a 500 year long control run with constant preindustrial forcing with the EC-Earth global climate model. Two modes emerge from this analysis. One mode is a standing mode with decadal time scale describing accumulation and release of fresh water in the Beaufort Gyre, known in the literature as the Beaufort Gyre flywheel. In addition, we identify a propagating mode with a time scale around 80 years, propagating along the rim of the Canadian Basin. This mode has maximum variability of the fresh water content in the Transpolar Drift and represents the bulk of the total variability of the fresh water content in the Arctic Ocean and also projects on the fresh water through the Fram Strait. Therefore, potentially, it can introduce a multidecadal variability to the Atlantic meridional overturning circulation. We will discuss the physical origin of this propagating mode. This include planetary-scale internal Rossby waves with multidecadal time scale, due to the slow variation of the Coriolis parameter at these high latitudes, as well as topographic steering of these Rossby waves. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53D2279K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53D2279K">Western tropical Pacific multidecadal variability forced by the Atlantic multidecadal oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kucharski, F.; Sun, C.; Li, J.; Jin, F. F.; Kang, I. S.; Ding, R. 2017-12-01 Observational analysis suggests that the western tropical Pacific (WTP) sea surface temperature (SST) shows predominant variability over multidecadal time scales, which is unlikely to be explained by the Interdecadal Pacific Oscillation. Here we show that this variability is largely explained by the remote Atlantic multidecadal oscillation (AMO). A suite of Atlantic Pacemaker experiments successfully reproduces the WTP multidecadal variability and the AMO-WTP SST connection. The AMO warm SST anomaly generates an atmospheric teleconnection to the North Pacific, which weakens the Aleutian low and subtropical North Pacific westerlies. The wind changes induce a subtropical North Pacific SST warming through wind-evaporation-SST effect, and in response to this warming, the surface winds converge towards the subtropical North Pacific from the tropics, leading to anomalous cyclonic circulation and low pressure over the WTP region. The warm SST anomaly further develops due to the SST-sea level pressure-cloud-longwave radiation positive feedback. Our findings suggest that the Atlantic Ocean acts as a key pacemaker for the western Pacific decadal climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5504304','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5504304">Western tropical Pacific multidecadal variability forced by the Atlantic multidecadal oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Sun, Cheng; Kucharski, Fred; Li, Jianping; Jin, Fei-Fei; Kang, In-Sik; Ding, Ruiqiang 2017-01-01 Observational analysis suggests that the western tropical Pacific (WTP) sea surface temperature (SST) shows predominant variability over multidecadal time scales, which is unlikely to be explained by the Interdecadal Pacific Oscillation. Here we show that this variability is largely explained by the remote Atlantic multidecadal oscillation (AMO). A suite of Atlantic Pacemaker experiments successfully reproduces the WTP multidecadal variability and the AMO–WTP SST connection. The AMO warm SST anomaly generates an atmospheric teleconnection to the North Pacific, which weakens the Aleutian low and subtropical North Pacific westerlies. The wind changes induce a subtropical North Pacific SST warming through wind–evaporation–SST effect, and in response to this warming, the surface winds converge towards the subtropical North Pacific from the tropics, leading to anomalous cyclonic circulation and low pressure over the WTP region. The warm SST anomaly further develops due to the SST–sea level pressure–cloud–longwave radiation positive feedback. Our findings suggest that the Atlantic Ocean acts as a key pacemaker for the western Pacific decadal climate variability. PMID:28685765 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...815998S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...815998S">Western tropical Pacific multidecadal variability forced by the Atlantic multidecadal oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sun, Cheng; Kucharski, Fred; Li, Jianping; Jin, Fei-Fei; Kang, In-Sik; Ding, Ruiqiang 2017-07-01 Observational analysis suggests that the western tropical Pacific (WTP) sea surface temperature (SST) shows predominant variability over multidecadal time scales, which is unlikely to be explained by the Interdecadal Pacific Oscillation. Here we show that this variability is largely explained by the remote Atlantic multidecadal oscillation (AMO). A suite of Atlantic Pacemaker experiments successfully reproduces the WTP multidecadal variability and the AMO-WTP SST connection. The AMO warm SST anomaly generates an atmospheric teleconnection to the North Pacific, which weakens the Aleutian low and subtropical North Pacific westerlies. The wind changes induce a subtropical North Pacific SST warming through wind-evaporation-SST effect, and in response to this warming, the surface winds converge towards the subtropical North Pacific from the tropics, leading to anomalous cyclonic circulation and low pressure over the WTP region. The warm SST anomaly further develops due to the SST-sea level pressure-cloud-longwave radiation positive feedback. Our findings suggest that the Atlantic Ocean acts as a key pacemaker for the western Pacific decadal climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC41A0993T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC41A0993T">Early 20th Century Arctic Warming Intensified by Pacific and Atlantic Multidecadal Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tokinaga, H.; Xie, S. P.; Mukougawa, H. 2017-12-01 We investigate the influence of Pacific and Atlantic multidecadal variability on the Arctic temperature, with a particular focus on the early 20th century Arctic warming. Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing than at present. We find that the concurrent phase shift of Pacific and Atlantic multidecadal variability is the major driver for the early 20th century Arctic warming. Atmospheric model simulations reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early Arctic warming is associated with the cold-to-warm phase shifts of Atlantic and Pacific multidecadal variability modes, a SST pattern reminiscent of the positive phase of the Pacific decadal and Atlantic multidecadal oscillations. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. The equatorial Pacific warming deepens the Aleutian low, advecting warm air to the North American Arctic. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, cold-to-warm phase shift of the Pacific and Atlantic multidecadal variability. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li class="active">1</li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_2" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="21"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5987L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5987L">A Decadal-scale Air-sea Interaction Theory for North Atlantic Multidecadal Variability: the NAT-NAO-AMOC-AMO Coupled Mode and Its Remote Influences</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, Jianping; Sun, Cheng; Jin, Fei-Fei 2017-04-01 ABSTRACT North Atlantic region shows prominent multidecadal variability. Observational analysis shows that the North Atlantic Oscillation (NAO) leads the oceanic Atlantic Multidecadal Oscillation (AMO) by 15-20 years and the latter also leads the former by around 15 years. The mechanisms are investigated using simulations from a fully coupled model, and a NATNAO-AMOC-AMO Coupled Mode is proposed to explain the multidecadal variability in North Atlantic region. The NAT-NAO-AMO-AMOC coupled mode has important remote influences on regional climates. Observational analysis identifies a significant in-phase relationship between the AMV and Siberian warm season (May to October) precipitation. The physical mechanism for this relationship is investigated using both observations and numerical simulations. North Atlantic sea surface temperature (SST) warming associated with the positive AMV phase can excite an eastward propagating wave train response across the entire Eurasian continent, which includes an east-west dipole structure over Siberia. The dipole then leads to anomalous southerly winds bringing moisture northward to Siberia; the precipitation increases correspondingly. Furthermore, a prominent teleconnection pattern of multidecadal variability of cold season (November to April) upper-level atmospheric circulation over North Africa and Eurasia (NA-EA) is revealed by empirical orthogonal function analysis of the Twentieth Century Reanalysis data, and this teleconnection pattern is referred to as the Africa-Asia multidecadal teleconnection pattern (AAMT). A strong inphase relationship is observed between the AAMT and Atlantic multidecadal variability (AMV) and this connection is mainly due to Rossby wave dynamics. The AAMT acts as an atmospheric bridge conveying the influence of AMV onto the downstream multidecadal climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028074','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028074">Multidecadal climate variability of global lands and oceans</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> McCabe, G.J.; Palecki, M.A. 2006-01-01 Principal components analysis (PCA) and singular value decomposition (SVD) are used to identify the primary modes of decadal and multidecadal variability in annual global Palmer Drought Severity Index (PDSI) values and sea-surface temperature (SSTs). The PDSI and SST data for 1925-2003 were detrended and smoothed (with a 10-year moving average) to isolate the decadal and multidecadal variability. The first two principal components (PCs) of the PDSI PCA explained almost 38% of the decadal and multidecadal variance in the detrended and smoothed global annual PDSI data. The first two PCs of detrended and smoothed global annual SSTs explained nearly 56% of the decadal variability in global SSTs. The PDSI PCs and the SST PCs are directly correlated in a pairwise fashion. The first PDSI and SST PCs reflect variability of the detrended and smoothed annual Pacific Decadal Oscillation (PDO), as well as detrended and smoothed annual Indian Ocean SSTs. The second set of PCs is strongly associated with the Atlantic Multidecadal Oscillation (AMO). The SVD analysis of the cross-covariance of the PDSI and SST data confirmed the close link between the PDSI and SST modes of decadal and multidecadal variation and provided a verification of the PCA results. These findings indicate that the major modes of multidecadal variations in SSTs and land-surface climate conditions are highly interrelated through a small number of spatially complex but slowly varying teleconnections. Therefore, these relations may be adaptable to providing improved baseline conditions for seasonal climate forecasting. Published in 2006 by John Wiley & Sons, Ltd. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP41D..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP41D..07S">Evolution of multidecadal variability in the West African monsoon during the last deglaciation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shanahan, T. M.; McKay, N. 2017-12-01 The West African monsoon system is strongly linked to changes in Atlantic variability on multidecadal to millennial timescales. Understanding the nature of these linkages thus provides important insights into the susceptibility of West African precipitation to past and future changes in Atlantic circulation. Here, we use an annually-resolved record of lamination thickness variations from Lake Bosumtwi, Ghana to generate an unprecedented record of changes in the West African monsoon spanning the last deglaciation ( 12.8-24 ka BP) and the latest Holocene (0-2.6 ka BP). Millennial-scale variability in varve thickness is consistent with published data from hydrogen isotopes in leaf waxes, showing a dramatic and sustained shift to drier conditions during HS1, a rapid recovery at the onset of the Bølling-Allerød and a gradual shift towards drier conditions following the end of the African Humid Period. The varve thickness record also indicates the presence of significant multidecadal ( 40- 80 years) West African monsoon variability throughout much of the record, disappearing only during the later portion of HS1 ( 14.8-16 ka BP). Previous studies have linked multidecadal variability in the West African monsoon to the Atlantic Multidecadal Oscillation (AMO), a low frequency mode of North Atlantic sea surface temperature variability that is hypothesized to be controlled by changes in North Atlantic heat transport via the Atlantic Meridional Overturning Circulation (AMOC). Our reconstruction indicates that this mode of multidecadal variability was active not only throughout the late Holocene but during the Last Glacial Maximum and much of the deglaciation, including the first half of HS1. The later result is unexpected in that it suggests that the AMO remained active even as the Atlantic overturning circulation collapsed and the African monsoon weakened during the initial phase of HS1. The decoupling of multidecadal and millennial scale variability suggests either a complex, time-transgressive Atlantic circulation response to changing conditions during HS1 or that the driver of multidecadal variability resides in some process other than the AMOC. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010NatGe...3..688O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010NatGe...3..688O">External forcing as a metronome for Atlantic multidecadal variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Otterå, Odd Helge; Bentsen, Mats; Drange, Helge; Suo, Lingling 2010-10-01 Instrumental records, proxy data and climate modelling show that multidecadal variability is a dominant feature of North Atlantic sea-surface temperature variations, with potential impacts on regional climate. To understand the observed variability and to gauge any potential for climate predictions it is essential to identify the physical mechanisms that lead to this variability, and to explore the spatial and temporal characteristics of multidecadal variability modes. Here we use a coupled ocean-atmosphere general circulation model to show that the phasing of the multidecadal fluctuations in the North Atlantic during the past 600 years is, to a large degree, governed by changes in the external solar and volcanic forcings. We find that volcanoes play a particularly important part in the phasing of the multidecadal variability through their direct influence on tropical sea-surface temperatures, on the leading mode of northern-hemisphere atmosphere circulation and on the Atlantic thermohaline circulation. We suggest that the implications of our findings for decadal climate prediction are twofold: because volcanic eruptions cannot be predicted a decade in advance, longer-term climate predictability may prove challenging, whereas the systematic post-eruption changes in ocean and atmosphere may hold promise for shorter-term climate prediction. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/biblio/1328543-spatial-patterns-sea-level-variability-associated-natural-internal-climate-modes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1328543-spatial-patterns-sea-level-variability-associated-natural-internal-climate-modes">Spatial Patterns of Sea Level Variability Associated with Natural Internal Climate Modes</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Han, Weiqing; Meehl, Gerald A.; Stammer, Detlef Sea level rise (SLR) can exert significant stress on highly populated coastal societies and low-lying island countries around the world. Because of this, there is huge societal demand for improved decadal predictions and future projections of SLR, particularly on a local scale along coastlines. Regionally, sea level variations can deviate considerably from the global mean due to various geophysical processes. These include changes of ocean circulations, which partially can be attributed to natural, internal modes of variability in the complex Earth’s climate system. Anthropogenic influence may also contribute to regional sea level variations. Separating the effects of natural climate modesmore » and anthropogenic forcing, however, remains a challenge and requires identification of the imprint of specific climate modes in observed sea level change patterns. In this article, we review our current state of knowledge about spatial patterns of sea level variability associated with natural climate modes on interannual-to-multidecadal timescales, with particular focus on decadal-to-multidecadal variability. Relevant climate modes and our current state of understanding their associated sea level patterns and driving mechanisms are elaborated separately for the Pacific, the Indian, the Atlantic, and the Arctic and Southern Oceans. We also discuss the issues, challenges and future outlooks for understanding the regional sea level patterns associated with climate modes. Effects of these internal modes have to be taken into account in order to achieve more reliable near-term predictions and future projections of regional SLR.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1328543-spatial-patterns-sea-level-variability-associated-natural-internal-climate-modes','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1328543-spatial-patterns-sea-level-variability-associated-natural-internal-climate-modes">Spatial Patterns of Sea Level Variability Associated with Natural Internal Climate Modes</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Han, Weiqing; Meehl, Gerald A.; Stammer, Detlef; ... 2016-10-04 Sea level rise (SLR) can exert significant stress on highly populated coastal societies and low-lying island countries around the world. Because of this, there is huge societal demand for improved decadal predictions and future projections of SLR, particularly on a local scale along coastlines. Regionally, sea level variations can deviate considerably from the global mean due to various geophysical processes. These include changes of ocean circulations, which partially can be attributed to natural, internal modes of variability in the complex Earth’s climate system. Anthropogenic influence may also contribute to regional sea level variations. Separating the effects of natural climate modesmore » and anthropogenic forcing, however, remains a challenge and requires identification of the imprint of specific climate modes in observed sea level change patterns. In this article, we review our current state of knowledge about spatial patterns of sea level variability associated with natural climate modes on interannual-to-multidecadal timescales, with particular focus on decadal-to-multidecadal variability. Relevant climate modes and our current state of understanding their associated sea level patterns and driving mechanisms are elaborated separately for the Pacific, the Indian, the Atlantic, and the Arctic and Southern Oceans. We also discuss the issues, challenges and future outlooks for understanding the regional sea level patterns associated with climate modes. Effects of these internal modes have to be taken into account in order to achieve more reliable near-term predictions and future projections of regional SLR.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SGeo...38..217H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SGeo...38..217H">Spatial Patterns of Sea Level Variability Associated with Natural Internal Climate Modes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Han, Weiqing; Meehl, Gerald A.; Stammer, Detlef; Hu, Aixue; Hamlington, Benjamin; Kenigson, Jessica; Palanisamy, Hindumathi; Thompson, Philip 2017-01-01 Sea level rise (SLR) can exert significant stress on highly populated coastal societies and low-lying island countries around the world. Because of this, there is huge societal demand for improved decadal predictions and future projections of SLR, particularly on a local scale along coastlines. Regionally, sea level variations can deviate considerably from the global mean due to various geophysical processes. These include changes of ocean circulations, which partially can be attributed to natural, internal modes of variability in the complex Earth's climate system. Anthropogenic influence may also contribute to regional sea level variations. Separating the effects of natural climate modes and anthropogenic forcing, however, remains a challenge and requires identification of the imprint of specific climate modes in observed sea level change patterns. In this paper, we review our current state of knowledge about spatial patterns of sea level variability associated with natural climate modes on interannual-to-multidecadal timescales, with particular focus on decadal-to-multidecadal variability. Relevant climate modes and our current state of understanding their associated sea level patterns and driving mechanisms are elaborated separately for the Pacific, the Indian, the Atlantic, and the Arctic and Southern Oceans. We also discuss the issues, challenges and future outlooks for understanding the regional sea level patterns associated with climate modes. Effects of these internal modes have to be taken into account in order to achieve more reliable near-term predictions and future projections of regional SLR. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP42B..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP42B..07C">The Primacy of Multidecadal to Centennial Variability Over Late Holocene Forced Change of the Asian Monsoon on the Southern Tibetan Plateau</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Conroy, J. L.; Hudson, A. M.; Overpeck, J. T.; Liu, K. B.; Luo, W.; Cole, J. E. 2016-12-01 The nature of multidecadal to centennial variability of the Asian monsoon remains largely unknown. Here we use the sediment record from a closed-basin lake in southern Tibet, Ngamring Tso, to assess summer monsoon precipitation from 4100 cal yr BP to present. The first principal component of the Ngamring Tso grain size record correlates significantly with observed June-September precipitation. From CE 1940-2007, grain size decreased with increasing summer precipitation and increased with decreasing summer precipitation. Satellite images of Ngamring Tso suggest precipitation-induced changes in lake depth or area likely govern grain size variability. Prolonged periods of weak summer monsoon precipitation occurred from 2800-2600 cal yr BP, 2500-2300 cal yr BP, and 1600-400 cal yr BP. A trend toward increased summer precipitation began around 1000 cal yr BP, with above-average summer precipitation from 400 cal yr BP to present, peaking between 200-100 cal yr BP. Dry and wet periods are coincident with dry and wet periods in other south-central Tibetan lake sediment records and with regional proxies of the ISM and EASM, indicating south-central Tibet is influenced by both monsoon subsystems. 20th century precipitation variability in southern Tibet falls within the range of natural variability in the last 4100 years, and does not show a clear trend of increasing precipitation as projected by models. Instead, it appears that poorly understood internal modes of monsoon variability remained influential throughout the last 4100 years. Substantial multidecadal to centennial-scale variability will thus complicate our ability to project future anthropogenic changes in the region's monsoon precipitation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3144934','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3144934">Imprint of the Atlantic Multidecadal Oscillation on Tree-Ring Widths in Northeastern Asia since 1568</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wang, Xiaochun; Brown, Peter M.; Zhang, Yanni; Song, Laiping 2011-01-01 We present a new tree-ring reconstruction of the Atlantic Multidecadal Oscillation (AMO) spanning 1568–2007 CE from northeast Asia. Comparison of the instrumental AMO index, an existing tree-ring based AMO reconstruction, and this new record show strongly similar annual to multidecadal patterns of variation over the last 440 years. Warm phases of the AMO are related to increases in growth of Scots pine trees and moisture availability in northeast China and central eastern Siberia. Multi-tape method (MTM) and cross-wavelet analyses indicate that robust multidecadal (∼64–128 years) variability is present throughout the new proxy record. Our results have important implications concerning the influence of North Atlantic sea surface temperatures on East Asian climate, and provide support for the possibility of an AMO signature on global multidecadal climate variability. PMID:21818380 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48.3903S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48.3903S">Cold season Africa-Asia multidecadal teleconnection pattern and its relation to the Atlantic multidecadal variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sun, Cheng; Li, Jianping; Ding, Ruiqiang; Jin, Ze 2017-06-01 A prominent teleconnection pattern of multidecadal variability of cold season (November to April) upper-level atmospheric circulation over North Africa and Eurasia (NA-EA) is revealed by empirical orthogonal function analysis of the Twentieth Century Reanalysis data. This teleconnection pattern is characterized by an eastward propagating wave train with a zonal wavenumber of 5-6 between 20° and 40°N, extending from the northwest coast of Africa to East Asia, and thus is referred to as the Africa-Asia multidecadal teleconnection pattern (AAMT). One-point correlation maps show that the teleconnectivity of AAMT is strong and further demonstrate the existence of the AAMT. The AAMT shapes the spatial structure of multidecadal change in atmospheric circulation over the NA-EA region, and in particular the AAMT pattern and associated fields show similar structures to the change occurring around the early 1960s. A strong in-phase relationship is observed between the AAMT and Atlantic multidecadal variability (AMV) and this connection is mainly due to Rossby wave dynamics. Barotropic modeling results suggest that the upper-level Rossby wave source generated by the AMV can excite the AAMT wave train, and Rossby wave ray tracing analysis further highlights the role of the Asian jet stream in guiding the wave train to East Asia. The AAMT acts as an atmospheric bridge conveying the influence of AMV onto the downstream multidecadal climate variability. The AMV is closely related to the coordinated change in surface and tropospheric air temperatures over Northwest Africa, the Arabian Peninsula and Central China, which may result from the adiabatic expansion/compression of air associated with the AAMT. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26930402','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26930402">Internal Variability-Generated Uncertainty in East Asian Climate Projections Estimated with 40 CCSM3 Ensembles.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yao, Shuai-Lei; Luo, Jing-Jia; Huang, Gang 2016-01-01 Regional climate projections are challenging because of large uncertainty particularly stemming from unpredictable, internal variability of the climate system. Here, we examine the internal variability-induced uncertainty in precipitation and surface air temperature (SAT) trends during 2005-2055 over East Asia based on 40 member ensemble projections of the Community Climate System Model Version 3 (CCSM3). The model ensembles are generated from a suite of different atmospheric initial conditions using the same SRES A1B greenhouse gas scenario. We find that projected precipitation trends are subject to considerably larger internal uncertainty and hence have lower confidence, compared to the projected SAT trends in both the boreal winter and summer. Projected SAT trends in winter have relatively higher uncertainty than those in summer. Besides, the lower-level atmospheric circulation has larger uncertainty than that in the mid-level. Based on k-means cluster analysis, we demonstrate that a substantial portion of internally-induced precipitation and SAT trends arises from internal large-scale atmospheric circulation variability. These results highlight the importance of internal climate variability in affecting regional climate projections on multi-decadal timescales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ERL....13b4016F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ERL....13b4016F">Synchronous multi-decadal climate variability of the whole Pacific areas revealed in tree rings since 1567</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fang, Keyan; Cook, Edward; Guo, Zhengtang; Chen, Deliang; Ou, Tinghai; Zhao, Yan 2018-02-01 Oceanic and atmospheric patterns play a crucial role in modulating climate variability from interannual to multi-decadal timescales by causing large-scale co-varying climate changes. The brevity of the existing instrumental records hinders the ability to recognize climate patterns before the industrial era, which can be alleviated using proxies. Unfortunately, proxy based reconstructions of oceanic and atmospheric modes of the past millennia often have modest agreements with each other before the instrumental period, raising questions about the robustness of the reconstructions. To ensure the stability of climate signals in proxy data through time, we first identified tree-ring datasets from distant regions containing coherent variations in Asia and North America, and then interpreted their climate information. We found that the multi-decadal covarying climate patterns of the middle and high latitudinal regions around the northern Pacific Ocean agreed quite well with the climate reconstructions of the tropical and southern Pacific areas. This indicates a synchronous variability at the multi-decadal timescale of the past 430 years for the entire Pacific Ocean. This pattern is closely linked to the dominant mode of the Pacific sea surface temperature (SST) after removing the warming trend. This Pacific multi-decadal SST variability resembles the Interdecadal Pacific Oscillation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70000159','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70000159">Associations of multi-decadal sea-surface temperature variability with US drought</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> McCabe, G.J.; Betancourt, J.L.; Gray, S.T.; Palecki, M.A.; Hidalgo, H.G. 2008-01-01 Recent research suggests a link between drought occurrence in the conterminous United States (US) and sea surface temperature (SST) variability in both the tropical Pacific and North Atlantic Oceans on decadal to multidecadal (D2M) time scales. Results show that the Atlantic Multidecadal Oscillation (AMO) is the most consistent indicator of D2M drought variability in the conterminous US during the 20th century, but during the 19th century the tropical Pacific is a more consistent indicator of D2 M drought. The interaction between El Nin??o-Southern Oscillation (ENSO) and the AMO explain a large part of the D2M drought variability in the conterminous US. More modeling studies are needed to reveal possible mechanisms linking low-frequency ENSO variability and the AMO with drought in the conterminous US. ?? 2007 Elsevier Ltd and INQUA. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26975331','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26975331">The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yamamoto, Ayako; Palter, Jaime B 2016-03-15 Northern Hemisphere climate responds sensitively to multidecadal variability in North Atlantic sea surface temperature (SST). It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe's climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. Here we trace the cause of this missing imprint to a dynamic anomaly of the atmospheric circulation that masks its thermodynamic response to SST anomalies. Specifically, differences in the pathways Lagrangian particles take to Europe during anomalous SST winters suppress the expected fluctuations in air-sea heat exchange accumulated along those trajectories. Because decadal variability in North Atlantic-average SST may be driven partly by the Atlantic Meridional Overturning Circulation (AMOC), the atmosphere's dynamical adjustment to this mode of variability may have important implications for the European wintertime temperature response to a projected twenty-first century AMOC decline. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS31B2016S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS31B2016S">Identifying Decadal to Multi-decadal Variability in the Pacific by Empirical Mode Decomposition</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sommers, L. A.; Hamlington, B.; Cheon, S. H. 2016-12-01 Large scale climate variability in the Pacific Ocean like that associated with ENSO and the Pacific Decadal Oscillation (PDO) has been shown to have a significant impact on climate and sea level across a range of timescales. The changes related to these climate signals have worldwide impacts on fisheries, weather, and precipitation patterns among others. Understanding these inter-annual to multi-decadal oscillations is imperative to longer term climate forecasts and understanding how climate will behave, and its effect on changes in sea level. With a 110-year reconstruction of sea level, we examine decadal to multi-decadal variability seen in the sea level fluctuations in the Pacific Ocean. Using empirical mode decomposition (EMD), we break down regional sea level into a series of intrinsic mode functions (IMFs) and attempt attribution of these IMFs to specific climate modes of variability. In particular, and not unexpectedly, we identify IMFs associated with the PDO, finding correlations between the PDO Index and IMFs in the Pacific Ocean upwards of 0.6-0.8 over the 110-year reconstructed record. Perhaps more significantly, we also find evidence of a longer multi-decadal signal ( 50-60 years) in the higher order IMFs. This lower frequency variability has been suggested in previous literature as influencing GMSL, but here we find a regional pattern associated with this multi-decadal signal. By identifying and separating these periodic climate signals, we can gain a better understanding of how the sea level variability associated with these modes can impact sea level on short timescales and serve to exacerbate the effects of long-term sea level change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005GeoRL..3216712S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005GeoRL..3216712S">Variable solar irradiance as a plausible agent for multidecadal variations in the Arctic-wide surface air temperature record of the past 130 years</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Soon, Willie W.-H. 2005-08-01 This letter offers new evidence motivating a more serious consideration of the potential Arctic temperature responses as a consequence of the decadal, multidecadal and longer-term persistent forcing by the ever-changing solar irradiance both in terms of total solar irradiance (TSI, i.e., integrated over all wavelengths) and the related UV irradiance. The support for such a solar modulator can be minimally derived from the large (>75%) explained variance for the decadally-smoothed Arctic surface air temperatures (SATs) by TSI and from the time-frequency structures of the TSI and Arctic SAT variability as examined by wavelet analyses. The reconstructed Arctic SAT time series based on the inverse wavelet transform, which includes decadal (5-15 years) and multidecadal (40-80 years) variations and a longer-term trend, contains nonstationary but persistent features that are highly correlated with the Sun's intrinsic magnetic variability especially on multidecadal time scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.4246B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.4246B">Role of internal variability in recent decadal to multidecadal tropical Pacific climate changes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bordbar, Mohammad Hadi; Martin, Thomas; Latif, Mojib; Park, Wonsun 2017-05-01 While the Earth's surface has considerably warmed over the past two decades, the tropical Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds, the surface component of the Pacific Walker Circulation (PWC). Previous studies show that this decadal trend in the trade winds is generally beyond the range of decadal trends simulated by climate models when forced by historical radiative forcing. There is still a debate on the origin of and the potential role that internal variability may have played in the recent decadal surface wind trend. Using a number of long control (unforced) integrations of global climate models and several observational data sets, we address the question as to whether the recent decadal to multidecadal trends are robustly classified as an unusual event or the persistent response to external forcing. The observed trends in the tropical Pacific surface climate are still within the range of the long-term internal variability spanned by the models but represent an extreme realization of this variability. Thus, the recent observed decadal trends in the tropical Pacific, though highly unusual, could be of natural origin. We note that the long-term trends in the selected PWC indices exhibit a large observational uncertainty, even hindering definitive statements about the sign of the trends.<abstract type="synopsis"><title type="main">Plain Language SummaryWhile the Earth's surface has considerably warmed over the past two decades, the tropical Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds. Here we show that climate models simulate a high level of internal variability, so that the recent changes in the tropical Pacific could still be due to natural processes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70170271','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70170271">Late Holocene sea level variability and Atlantic Meridional Overturning Circulation</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Cronin, Thomas M.; Farmer, Jesse R.; Marzen, R. E.; Thomas, E.; Varekamp, J.C. 2014-01-01 Pre-twentieth century sea level (SL) variability remains poorly understood due to limits of tide gauge records, low temporal resolution of tidal marsh records, and regional anomalies caused by dynamic ocean processes, notably multidecadal changes in Atlantic Meridional Overturning Circulation (AMOC). We examined SL and AMOC variability along the eastern United States over the last 2000 years, using a SL curve constructed from proxy sea surface temperature (SST) records from Chesapeake Bay, and twentieth century SL-sea surface temperature (SST) relations derived from tide gauges and instrumental SST. The SL curve shows multidecadal-scale variability (20–30 years) during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), as well as the twentieth century. During these SL oscillations, short-term rates ranged from 2 to 4 mm yr−1, roughly similar to those of the last few decades. These oscillations likely represent internal modes of climate variability related to AMOC variability and originating at high latitudes, although the exact mechanisms remain unclear. Results imply that dynamic ocean changes, in addition to thermosteric, glacio-eustatic, or glacio-isostatic processes are an inherent part of SL variability in coastal regions, even during millennial-scale climate oscillations such as the MCA and LIA and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea level rise. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CliPa..14..157S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CliPa..14..157S">Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Singh, Hansi K. A.; Hakim, Gregory J.; Tardif, Robert; Emile-Geay, Julien; Noone, David C. 2018-02-01 The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0-2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO) index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50- to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4796317','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4796317">The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Yamamoto, Ayako; Palter, Jaime B. 2016-01-01 Northern Hemisphere climate responds sensitively to multidecadal variability in North Atlantic sea surface temperature (SST). It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe's climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. Here we trace the cause of this missing imprint to a dynamic anomaly of the atmospheric circulation that masks its thermodynamic response to SST anomalies. Specifically, differences in the pathways Lagrangian particles take to Europe during anomalous SST winters suppress the expected fluctuations in air–sea heat exchange accumulated along those trajectories. Because decadal variability in North Atlantic-average SST may be driven partly by the Atlantic Meridional Overturning Circulation (AMOC), the atmosphere's dynamical adjustment to this mode of variability may have important implications for the European wintertime temperature response to a projected twenty-first century AMOC decline. PMID:26975331 </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC41A1006Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC41A1006Z">Tropical rainforests dominate multi-decadal variability of the global carbon cycle</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, X.; Wang, Y. P.; Peng, S.; Rayner, P. J.; Silver, J.; Ciais, P.; Piao, S.; Zhu, Z.; Lu, X.; Zheng, X. 2017-12-01 Recent studies find that inter-annual variability of global atmosphere-to-land CO2 uptake (NBP) is dominated by semi-arid ecosystems. However, the NBP variations at decadal to multi-decadal timescales are still not known. By developing a basic theory for the role of net primary production (NPP) and heterotrophic respiration (Rh) on NBP and applying it to 100-year simulations of terrestrial ecosystem models forced by observational climate, we find that tropical rainforests dominate the multi-decadal variability of global NBP (48%) rather than the semi-arid lands (35%). The NBP variation at inter-annual timescales is almost 90% contributed by NPP, but across longer timescales is progressively controlled by Rh that constitutes the response from the NPP-derived soil carbon input (40%) and the response of soil carbon turnover rates to climate variability (60%). The NBP variations of tropical rainforests is modulated by the ENSO and the PDO through their significant influences on temperature and precipitation at timescales of 2.5-7 and 25-50 years, respectively. This study highlights the importance of tropical rainforests on the multi-decadal variability of global carbon cycle, suggesting that we need to carefully differentiate the effect of NBP long-term fluctuations associated with ocean-related climate modes on the long-term trend in land sink. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950047289&hterms=temperature+variability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtemperature%2Bvariability','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047289&hterms=temperature+variability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtemperature%2Bvariability">Decadal variability of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mehta, Vikram M.; Delworth, Thomas 1995-01-01 Sea surface temperature (SST) variability was investigated in a 200-yr integration of a global model of the coupled oceanic and atmospheric general circulations developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The second 100 yr of SST in the coupled model's tropical Atlantic region were analyzed with a variety of techniques. Analyses of SST time series, averaged over approximately the same subregions as the Global Ocean Surface Temperature Atlas (GOSTA) time series, showed that the GFDL SST anomalies also undergo pronounced quasi-oscillatory decadal and multidecadal variability but at somewhat shorter timescales than the GOSTA SST anomalies. Further analyses of the horizontal structures of the decadal timescale variability in the GFDL coupled model showed the existence of two types of variability in general agreement with results of the GOSTA SST time series analyses. One type, characterized by timescales between 8 and 11 yr, has high spatial coherence within each hemisphere but not between the two hemispheres of the tropical Atlantic. A second type, characterized by timescales between 12 and 20 yr, has high spatial coherence between the two hemispheres. The second type of variability is considerably weaker than the first. As in the GOSTA time series, the multidecadal variability in the GFDL SST time series has approximately opposite phases between the tropical North and South Atlantic Oceans. Empirical orthogonal function analyses of the tropical Atlantic SST anomalies revealed a north-south bipolar pattern as the dominant pattern of decadal variability. It is suggested that the bipolar pattern can be interpreted as decadal variability of the interhemispheric gradient of SST anomalies. The decadal and multidecadal timescale variability of the tropical Atlantic SST, both in the actual and in the GFDL model, stands out significantly above the background 'red noise' and is coherent within each of the time series, suggesting that specific sets of processes may be responsible for the choice of the decadal and multidecadal timescales. Finally, it must be emphasized that the GFDL coupled ocean-atmosphere model generates the decadal and multidecadal timescale variability without any externally applied force, solar or lunar, at those timescales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMNH51B1610G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMNH51B1610G">Non-stationarity of extreme weather events in a changing climate - an application to long-term droughts in the US Southwest</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Grossmann, I. 2013-12-01 Return periods of many extreme weather events are not stationary over time, given increasing risks due to global warming and multidecadal variability resulting from large scale climate patterns. This is problematic as extreme weather events and long-term climate risks such as droughts are typically conceptualized via measures such as return periods that implicitly assume non-stationarity. I briefly review these problems and present an application to the non-stationarity of droughts in the US Southwest. The US Southwest relies on annual precipitation maxima during winter and the North American Monsoon (NAM), both of which vary with large-scale climate patterns, in particular ENSO, the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). The latter two exhibit variability on longer (multi-decadal) time scales in addition to short-term variations. The region is also part of the subtropical belt projected to become more arid in a warming climate. The possible multidecadal impacts of the PDO on precipitation in the study region are analyzed with a focus on Arizona and New Mexico, using GPCC and CRU data since 1900. The projected impacts of the PDO on annual precipitation during the next three decades with GPCC data are similar in scale to the impacts of global warming on precipitation according to the A1B scenario and the CMIP2 multi-model means, while the combined impact of the PDO and AMO is about 19% larger. The effects according to the CRU dataset are about half as large as the projected global warming impacts. Given the magnitude of the projected impacts from both multidecadal variability and global warming, water management needs to explicitly incorporate both of these trends into long-term planning. Multi-decadal variability could be incorporated into the concept of return periods by presenting return periods as time-varying or as conditional on the respective 'phase' of relevant multidecadal patterns and on global warming. Problems in detecting the PDO signal and potential solutions are also discussed. We find that the long-term effect of the PDO can be more clearly separated from short-term variability by considering return periods of multi-year drought measures rather than return periods of simple drought measures that are more affected by short-term variations. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70035622','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70035622">Joint spatiotemporal variability of global sea surface temperatures and global Palmer drought severity index values</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Apipattanavis, S.; McCabe, G.J.; Rajagopalan, B.; Gangopadhyay, S. 2009-01-01 Dominant modes of individual and joint variability in global sea surface temperatures (SST) and global Palmer drought severity index (PDSI) values for the twentieth century are identified through a multivariate frequency domain singular value decomposition. This analysis indicates that a secular trend and variability related to the El Niño–Southern Oscillation (ENSO) are the dominant modes of variance shared among the global datasets. For the SST data the secular trend corresponds to a positive trend in Indian Ocean and South Atlantic SSTs, and a negative trend in North Pacific and North Atlantic SSTs. The ENSO reconstruction shows a strong signal in the tropical Pacific, North Pacific, and Indian Ocean regions. For the PDSI data, the secular trend reconstruction shows high amplitudes over central Africa including the Sahel, whereas the regions with strong ENSO amplitudes in PDSI are the southwestern and northwestern United States, South Africa, northeastern Brazil, central Africa, the Indian subcontinent, and Australia. An additional significant frequency, multidecadal variability, is identified for the Northern Hemisphere. This multidecadal frequency appears to be related to the Atlantic multidecadal oscillation (AMO). The multidecadal frequency is statistically significant in the Northern Hemisphere SST data, but is statistically nonsignificant in the PDSI data. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PolSc..10..199T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PolSc..10..199T">Relationship between the Arctic oscillation and surface air temperature in multi-decadal time-scale</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tanaka, Hiroshi L.; Tamura, Mina 2016-09-01 In this study, a simple energy balance model (EBM) was integrated in time, considering a hypothetical long-term variability in ice-albedo feedback mimicking the observed multi-decadal temperature variability. A natural variability was superimposed on a linear warming trend due to the increasing radiative forcing of CO2. The result demonstrates that the superposition of the natural variability and the background linear trend can offset with each other to show the warming hiatus for some period. It is also stressed that the rapid warming during 1970-2000 can be explained by the superposition of the natural variability and the background linear trend at least within the simple model. The key process of the fluctuating planetary albedo in multi-decadal time scale is investigated using the JRA-55 reanalysis data. It is found that the planetary albedo increased for 1958-1970, decreased for 1970-2000, and increased for 2000-2012, as expected by the simple EBM experiments. The multi-decadal variability in the planetary albedo is compared with the time series of the AO mode and Barents Sea mode of surface air temperature. It is shown that the recent AO negative pattern showing warm Arctic and cold mid-latitudes is in good agreement with planetary albedo change indicating negative anomaly in high latitudes and positive anomaly in mid-latitudes. Moreover, the Barents Sea mode with the warm Barents Sea and cold mid-latitudes shows long-term variability similar to planetary albedo change. Although further studies are needed, the natural variabilities of both the AO mode and Barents Sea mode indicate some possible link to the planetary albedo as suggested by the simple EBM to cause the warming hiatus in recent years. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC32B..01O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC32B..01O">Increasing Megadrought Risk at the Intersection of Decadal to Centennial Variability and Climate Change</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Overpeck, J. T.; Parsons, L. A.; Loope, G. R.; Ault, T.; Cole, J. E.; Otto-Bliesner, B. L.; Buckle, N.; Stevenson, S.; Fasullo, J. 2016-12-01 Even more than the 1930's U.S. Dust Bowl Drought, the 20th century Sahel drought stands out as the most unprecedented drought of the instrumental era, in part because it extended over multiple decades. Paleoclimatic evidence makes it clear that this Sahel drought was nonetheless not really unprecedented - droughts many decades long have occurred in sub-Saharan Africa regularly over the last several thousand years, and these constitute what is now increasingly referred to as "megadrought." Paleoclimatic evidence also makes it clear that all drought-prone semi-arid and arid regions of the globe, including southwestern North America, southeastern Australia, and the Mediterranean/Middle Eastern region likely experienced multiple such multidecadal megadroughts in recent pre-Anthropocene Earth history. In other regions of the globe, including parts of South Asia and Amazonia, short but devastating droughts of the last 50-150 years, were also eclipsed in recent Earth history by much more serious megadrought, although these megadroughts were shorter than the multidecadal droughts of Africa or SW North America. In the past, megadroughts have occurred for reasons that are increasingly well understood in terms of ocean-atmosphere dynamics that led to unusually persistent precipitation deficits. Many of these same dynamics are well simulated in state-of-the-art Earth System Models, and yet comparisons between simulated and observed paleohydroclimatic variability suggests the models generally underestimate the risk of megadrought. Paleohydroclimatic records in some cases overestimate drought persistence, but there appear to be other issues at play that need to be better understood and simulated: positive land-atmosphere feedbacks, overly energetic interannual (i.e., ENSO) modes of variability, and insufficient internal multidecadal to centennial coupled climate system variability. Taking these issues and the impact of anthropogenic climate change into account means that the risk of megadrought is increasing significantly in many regions of the globe as the planet warms - tools, including critical paleoclimatic data, are being developed to help anticipate and adapt to this growing challenge. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP51C1086N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP51C1086N">Internal Climatic Influences From Secular To Multi-decadal Scales: Comparison Of NAO Reconstructions.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nicolle, M.; Debret, M.; Massei, N.; de Vernal, A. 2017-12-01 In the Northern Hemisphere, the North Atlantic Oscillation (NAO) is the major dominant mode of variability in winter atmospheric circulation, with large impacts on temperature, precipitation and storm tracks in the North Atlantic sector. To understand the role of this internal climatic oscillations on the past climate variability, several proxy-based reconstructions of the NAO were published during the last decades. Two of them are available during the past 1,200 years: a first NAO reconstruction published by Trouet et al. (2009) and a second proposed by Ortega et al. (2015). The major discrepancy between the two reconstructions concerns the transition period between the Medieval Climate Anomaly (MCA) and the Little Ice Age. The first NAO reconstruction shows persistent positive phases during the MCA (AD 1000-1300) but this dominant trend is not highlighted in the reconstruction proposed by Ortega et al. (2015), asking the question of the influence of predictors used to reconstruct the NAO signal during the last millennia. In these study, we compare the two NAO reconstructions in order to determine the effect of bi-proxy or multi-proxy approach on the signal reconstructed. Using statistical and wavelet analysis methods, we conclude that the number of predictors used do not have impact on the signal reconstruct. The two reconstructions signals are characterized by similar variabilities expressed from multi-decadal to multi-secular scales. The major trend difference seems to be link to the type of the predictor and particularly the use of Greenland ice cores in the reconstruction proposed in 2015. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=302477','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=302477">Intra- to Multi-Decadal Temperature Variability over the Continental United States: 1896-2012</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=302555','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=302555">Optimal ranking regime analysis of intra- to multidecadal U.S. climate variability. Part I: Temperature</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51L..06W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51L..06W">The Oceanic Contribution to Atlantic Multi-Decadal Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wills, R. C.; Armour, K.; Battisti, D. S.; Hartmann, D. L. 2017-12-01 Atlantic multi-decadal variability (AMV) is typically associated with variability in ocean heat transport (OHT) by the Atlantic Meridional Overturning Circulation (AMOC). However, recent work has cast doubt on this connection by showing that slab-ocean climate models, in which OHT cannot vary, exhibit similar variability. Here, we apply low-frequency component analysis to isolate the variability of Atlantic sea-surface temperatures (SSTs) that occurs on decadal and longer time scales. In observations and in pre-industrial control simulations of comprehensive climate models, we find that AMV is confined to the extratropics, with the strongest temperature anomalies in the North Atlantic subpolar gyre. We show that warm subpolar temperatures are associated with a strengthened AMOC, increased poleward OHT, and local heat fluxes from the ocean into the atmosphere. In contrast, the traditional index of AMV based on the basin-averaged SST anomaly shows warm temperatures preceded by heat fluxes from the atmosphere into the ocean, consistent with the atmosphere driving this variability, and shows a weak relationship with AMOC. The autocorrelation time of the basin-averaged SST index is 1 year compared to an autocorrelation time of 5 years for the variability of subpolar temperatures. This shows that multi-decadal variability of Atlantic SSTs is sustained by OHT variability associated with AMOC, while atmosphere-driven SST variability, such as exists in slab-ocean models, contributes primarily on interannual time scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29167451','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29167451">The role of Atlantic overturning circulation in the recent decline of Atlantic major hurricane frequency.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yan, Xiaoqin; Zhang, Rong; Knutson, Thomas R 2017-11-22 Observed Atlantic major hurricane frequency has exhibited pronounced multidecadal variability since the 1940s. However, the cause of this variability is debated. Using observations and a coupled earth system model (GFDL-ESM2G), here we show that the decline of the Atlantic major hurricane frequency during 2005-2015 is associated with a weakening of the Atlantic Meridional Overturning Circulation (AMOC) inferred from ocean observations. Directly observed North Atlantic sulfate aerosol optical depth has not increased (but shows a modest decline) over this period, suggesting the decline of the Atlantic major hurricane frequency during 2005-2015 is not likely due to recent changes in anthropogenic sulfate aerosols. Instead, we find coherent multidecadal variations involving the inferred AMOC and Atlantic major hurricane frequency, along with indices of Atlantic Multidecadal Variability and inverted vertical wind shear. Our results provide evidence for an important role of the AMOC in the recent decline of Atlantic major hurricane frequency. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PrOce.159...86K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PrOce.159...86K">Multidecadal, centennial, and millennial variability in sardine and anchovy abundances in the western North Pacific and climate-fish linkages during the late Holocene</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kuwae, Michinobu; Yamamoto, Masanobu; Sagawa, Takuya; Ikehara, Ken; Irino, Tomohisa; Takemura, Keiji; Takeoka, Hidetaka; Sugimoto, Takashige 2017-12-01 Paleorecords of pelagic fish abundance could better define the nature of fishery productivity dynamics and help understand responses of pelagic fish stocks to long-term climate changes. We report a high-resolution record of sardine and anchovy scale deposition rates (SDRs) from Beppu Bay, Southwest Japan, showing multidecadal and centennial variability in the abundance of Japanese sardine and Japanese anchovy during the last 2850 years. Variations in the sardine SDR showed periodicities at ∼50, ∼100, and ∼300 yr, while variations in the anchovy SDR showed periodicities at ∼30 and ∼260 yr. Comparisons between and correlation analyses of the time series of the sardine and anchovy SDRs demonstrate that there is not a consistent out-of-phase relationship during the last 2850 years. This indicates that the multidecadal alternations in the sardine and anchovy populations commonly seen in the 20th century did not necessarily occur during earlier periods. The Japanese sardine SDR record shows a long-term decreasing trend in the amplitudes of the multidecadal to centennial fluctuations. This decreasing trend may have resulted from an increasing trend in the winter sea surface temperature in the western North Pacific. The multicentennial variability in sardine abundance during the last millennium is consistent with the variabilities in the abnormal snow index in East Asia and the American tree ring-based Pacific Decadal Oscillation index, suggesting a basin-wide or regional climate-marine ecosystem linkage. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdAtS..35..317S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdAtS..35..317S">Asymmetric variations in the tropical ascending branches of Hadley circulations and the associated mechanisms and effects</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sun, Bo 2018-03-01 This study investigates the variations in the tropical ascending branches (TABs) of Hadley circulations (HCs) during past decades, using a variety of reanalysis datasets. The northern tropical ascending branch (NTAB) and the southern tropical ascending branch (STAB), which are defined as the ascending branches of the Northern Hemisphere HC and Southern Hemisphere HC, respectively, are identified and analyzed regarding their trends and variability. The reanalysis datasets consistently show a persistent increase in STAB during past decades, whereas they show less consistency in NTAB regarding its decadalto multidecadal variability, which generally features a decreasing trend. These asymmetric trends in STAB and NTAB are attributed to asymmetric trends in the tropical SSTs. The relationship between STAB/NTAB and tropical SSTs is further examined regarding their interannual and decadal- to multidecadal variability. On the interannual time scale, the STAB and NTAB are essentially modulated by the eastern-Pacific type of ENSO, with a strengthened (weakened) STAB (NTAB) under an El Niño condition. On the decadal- to multidecadal time scale, the variability of STAB and NTAB is closely related to the southern tropical SSTs and the meridional asymmetry of global tropical SSTs, respectively. The tropical eastern Pacific SSTs (southern tropical SSTs) dominate the tropical SST-NTAB/STAB relationship on the interannual (decadal- to multidecadal) scale, whereas the NTAB is a passive factor in this relationship. Moreover, a cross-hemispheric relationship between the NTAB/STAB and the HC upper-level meridional winds is revealed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS11B..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS11B..06M">Indo-Pacific sea level variability at multidecadal time scales</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Merrifield, M. A.; Thompson, P. R. 2016-12-01 Long tide gauge and atmospheric pressure measurements are used to infer multidecadal fluctuations in trade wind forcing and the associated Indo-Pacific sea level response along coastal and equatorial waveguides. The trade wind variations are marked by a weakening beginning with the late 1970s climate shift and a subsequent return to mean conditions since the early 1990s. These fluctuations covary with multidecadal wind changes at mid-latitudes, as measured by the Pacific Decadal Oscillation or the North Pacific indices; however, the mid-latitude multidecadal variations prior to 1970 or noticeably absent in the inferred trade wind record. The different behavior of tropical and mid-latitude winds support the notion that multidecadal climate variations in the Pacific result from a combination of processes and not a single coherent mode spanning the basin. In particular, the two-decade long satellite altimeter record represents a period of apparent connection between the two regions that was not exhibited earlier in the century. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51L..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51L..02D">Role of the North Atlantic Ocean in Low Frequency Climate Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Danabasoglu, G.; Yeager, S. G.; Kim, W. M.; Castruccio, F. S. 2017-12-01 The Atlantic Ocean is a unique basin with its extensive, North - South overturning circulation, referred to as the Atlantic meridional overturning circulation (AMOC). AMOC is thought to represent the dynamical memory of the climate system, playing an important role in decadal and longer time scale climate variability as well as prediction of the earth's future climate on these time scales via its large heat and salt transports. This oceanic memory is communicated to the atmosphere primarily through the influence of persistent sea surface temperature (SST) variations. Indeed, many modeling studies suggest that ocean circulation, i.e., AMOC, is largely responsible for the creation of coherent SST variability in the North Atlantic, referred to as Atlantic Multidecadal Variability (AMV). AMV has been linked to many (multi)decadal climate variations in, e.g., Sahel and Brazilian rainfall, Atlantic hurricane activity, and Arctic sea-ice extent. In the absence of long, continuous observations, much of the evidence for the ocean's role in (multi)decadal variability comes from model simulations. Although models tend to agree on the role of the North Atlantic Oscillation in creating the density anomalies that proceed the changes in ocean circulation, model fidelity in representing variability characteristics, mechanisms, and air-sea interactions remains a serious concern. In particular, there is increasing evidence that models significantly underestimate low frequency variability in the North Atlantic compared to available observations. Such model deficiencies can amplify the relative influence of external or stochastic atmospheric forcing in generating (multi)decadal variability, i.e., AMV, at the expense of ocean dynamics. Here, a succinct overview of the current understanding of the (North) Atlantic Ocean's role on the regional and global climate, including some outstanding questions, will be presented. In addition, a few examples of the climate impacts of the AMV via atmospheric teleconnections from a set of coupled simulations, also considering the relative roles of its tropical and extratropical components, will be highlighted. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..379M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..379M">Statistical link between external climate forcings and modes of ocean variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Malik, Abdul; Brönnimann, Stefan; Perona, Paolo 2017-07-01 In this study we investigate statistical link between external climate forcings and modes of ocean variability on inter-annual (3-year) to centennial (100-year) timescales using de-trended semi-partial-cross-correlation analysis technique. To investigate this link we employ observations (AD 1854-1999), climate proxies (AD 1600-1999), and coupled Atmosphere-Ocean-Chemistry Climate Model simulations with SOCOL-MPIOM (AD 1600-1999). We find robust statistical evidence that Atlantic multi-decadal oscillation (AMO) has intrinsic positive correlation with solar activity in all datasets employed. The strength of the relationship between AMO and solar activity is modulated by volcanic eruptions and complex interaction among modes of ocean variability. The observational dataset reveals that El Niño southern oscillation (ENSO) has statistically significant negative intrinsic correlation with solar activity on decadal to multi-decadal timescales (16-27-year) whereas there is no evidence of a link on a typical ENSO timescale (2-7-year). In the observational dataset, the volcanic eruptions do not have a link with AMO on a typical AMO timescale (55-80-year) however the long-term datasets (proxies and SOCOL-MPIOM output) show that volcanic eruptions have intrinsic negative correlation with AMO on inter-annual to multi-decadal timescales. The Pacific decadal oscillation has no link with solar activity, however, it has positive intrinsic correlation with volcanic eruptions on multi-decadal timescales (47-54-year) in reconstruction and decadal to multi-decadal timescales (16-32-year) in climate model simulations. We also find evidence of a link between volcanic eruptions and ENSO, however, the sign of relationship is not consistent between observations/proxies and climate model simulations. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...31M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...31M">On the spectral characteristics of the Atlantic multidecadal variability in an ensemble of multi-century simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mavilia, Irene; Bellucci, Alessio; J. Athanasiadis, Panos; Gualdi, Silvio; Msadek, Rym; Ruprich-Robert, Yohan 2018-01-01 The Atlantic multidecadal variability (AMV) is a coherent pattern of variability of the North Atlantic sea surface temperature field affecting several components of the climate system in the Atlantic region and the surrounding areas. The relatively short observational record severely limits our understanding of the physical mechanisms leading to the AMV. The present study shows that the spatial and temporal characteristics of the AMV, as assessed from the historical records, should also be considered as highly uncertain. Using 11 multi-century preindustrial climate simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) database, we show that the AMV characteristics are not constant along the simulation when assessed from different 200-year-long periods to match the observed period length. An objective method is proposed to test whether the variations of the AMV characteristics are consistent with stochastic internal variability. For 7 out of the 11 models analysed, the results indicate a non-stationary behaviour for the AMV time series. However, the possibility that the non-stationarity arises from sampling errors can be excluded with high confidence only for one of the 7 models. Therefore, longer time series are needed to robustly assess the AMV characteristics. In addition to any changes imposed to the AMV by external forcings, the detected dependence on the time interval identified in most models suggests that the character of the observed AMV may undergo significant changes in the future. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51L..01F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51L..01F">The influence of the North Atlantic Ocean variability on the atmosphere in the cold season at seasonal to multidecadal time scales</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Frankignoul, C. 2017-12-01 Observational evidence of an atmospheric response to the North Atlantic horseshoe SST anomalies has been accumulating since the late 90's, suggesting that it drives a negative NAO response during late fall/early winter. The North Atlantic horseshoe SST anomaly is in part stochastically driven by the atmosphere, but at low frequency it is correlated with the Atlantic Multidecadal Oscillation (AMO). Correspondingly, an atmospheric response to the AMO has been detected at low frequency in winter, with a positive AMO phase leading a negative NAO-like pattern, consistent with sensitivity studies with atmospheric general circulation models. Both the subpolar and tropical components of the AMO seem to contribute to its influence on the atmosphere. As North Atlantic SST changes reflects internally-generated SST fluctuations as well the response to anthropogenic and other external forcing, the AMO is sensitive to the way the forced SST signal is removed; estimates of the natural variability of the AMO vary by as much as a factor of two between estimation methods, leading to possible biases in its alleged impacts. Since an intensification of the Atlantic meridional overturning circulation (AMOC) leads the AMO and drives a negative NAO in many climate models, albeit with different lead times, the relation between AMO and AMOC will be discussed, as well as possible links with the North Pacific and sea ice variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7071F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7071F">Reconstructing the leading mode of multi-decadal North Atlantic variability over the last two millenia using functional paleoclimate networks</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Franke, Jasper G.; Werner, Johannes; Donner, Reik V. 2017-04-01 The increasing availability of high-resolution North Atlantic paleoclimate proxies allows to not only study local climate variations in time, but also temporal changes in spatial variability patterns across the entire region possibly controlled by large-scale coherent variability modes such as the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation. In this study, we use functional paleoclimate network analysis [1,2] to investigate changes in the statistical similarity patterns among an ensemble of high-resolution terrestrial paleoclimate records from Northern Europe included in the Arctic 2k data base. Specifically, we construct complex networks capturing the mutual statistical similarity of inter-annual temperature variability recorded in tree ring records, ice cores and lake sediments for multidecadal time windows covering the last two millenia. The observed patterns of co-variability are ultimately connected to the North Atlantic atmospheric circulation and most prominently to multidecadal variations of the NAO. Based on the inferred networks, we study the dynamical similarity between regional clusters of archives defined according to present-day inter-annual temperature variations across the study region. This analysis identifies those time-dependent inter-regional linkages that are most informative about the leading-order North Atlantic climate variability according to a recent NAO reconstruction for the last millenium [3]. Based on these linkages, we extend the existing reconstruction to obtain qualitative information on multidecadal to centennial scale North Atlantic climate variability over the last two millenia. In general, we find a tendency towards a dominating positive NAO phase interrupted by pronounced and extended intervals of negative NAO. Relatively rapid transitions between both types of behaviour are present during distinct periods including the Little Ice Age, the Medieval Climate Anomaly and for the Dark Ages Little Ice Age. [1] K. Rehfeld, N. Marwan, S.F.M. Breitenbach, J. Kurths: Late Holocene Asian summer monsoon dynamics from small but complex networks of paleoclimate data. Climate Dynamics 41, 3-19, 2013 [2] J.L. Oster, N.P. Kelley: Tracking regional and global teleconnections recorded by western North American speleothem records. Quaternary Science Reviews 149, 18-33, 2016 [3] P. Ortega, F. Lehner, D. Swingedouw, V. Masson-Delmotte, C.C. Raible, M. Casado, P. Yiou: A model-tested North Atlantic Oscillation reconstruction for the past millenium. Nature 523, 71-74, 2015 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017099','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017099">Megadroughts in Southwestern North America in ECHO-G Millennial Simulations and Their Comparison to Proxy Drought Reconstructions</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Coats, Sloan; Smerdon, Jason E.; Seager, Richard; Cook, Benjamin I.; Gozalez-Rouco, J. F. 2013-01-01 Simulated hydroclimate variability in millennium-length forced transient and control simulations from the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled atmosphere-ocean general circulation model (AOGCM) is analyzed and compared to 1000 years of reconstructed Palmer drought severity index (PDSI) variability from the North American Drought Atlas (NADA). The ability of the model to simulate megadroughts in the North American southwest is evaluated. (NASW: 25deg42.5degN, 125deg-105degW). Megadroughts in the ECHO-G AOGCM are found to be similar in duration and magnitude to those estimated from the NADA. The droughts in the forced simulation are not, however, temporally synchronous with those in the paleoclimate record, nor are there significant differences between the drought features simulated in the forced and control runs. These results indicate that model-simulated megadroughts can result from internal variability of the modeled climate system rather than as a response to changes in exogenous forcings. Although the ECHO-G AOGCM is capable of simulating megadroughts through persistent La Nina-like conditions in the tropical Pacific, other mechanisms can produce similarly extreme NASW moisture anomalies in the model. In particular, the lack of low-frequency coherence between NASW soil moisture and simulated modes of climate variability like the El Nino-Southern Oscillation, Pacific decadal oscillation, and Atlantic multidecadal oscillation during identified drought periods suggests that stochastic atmospheric variability can contribute significantly to the occurrence of simulated megadroughts in the NASW. These findings indicate that either an expanded paradigm is needed to understand multidecadal hydroclimate variability in the NASW or AOGCMs may incorrectly simulate the strength and/or dynamics of the connection between NASW hydroclimate variability and the tropical Pacific. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29780186','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29780186">Internal ocean-atmosphere variability drives megadroughts in Western North America.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Coats, S; Smerdon, J E; Cook, B I; Seager, R; Cook, E R; Anchukaitis, K J 2016-09-28 Multidecadal droughts that occurred during the Medieval Climate Anomaly represent an important target for validating the ability of climate models to adequately characterize drought risk over the near-term future. A prominent hypothesis is that these megadroughts were driven by a centuries-long radiatively forced shift in the mean state of the tropical Pacific Ocean. Here we use a novel combination of spatiotemporal tree-ring reconstructions of Northern Hemisphere hydroclimate to infer the atmosphere-ocean dynamics that coincide with megadroughts over the American West, and find that these features are consistently associated with ten-to-thirty year periods of frequent cold El Niño Southern Oscillation conditions and not a centuries-long shift in the mean of the tropical Pacific Ocean. These results suggest an important role for internal variability in driving past megadroughts. State-of-the art climate models from the Coupled Model Intercomparison Project phase 5, however, do not simulate a consistent association between megadroughts and internal variability of the tropical Pacific Ocean, with implications for our confidence in megadrought risk projections. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023617','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023617">Atmospheric Blocking and Atlantic Multi-Decadal Ocean Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Haekkinen, Sirpa; Rhines, Peter B.; Worthlen, Denise L. 2011-01-01 Based on the 20th century atmospheric reanalysis, winters with more frequent blocking, in a band of blocked latitudes from Greenland to Western Europe, are found to persist over several decades and correspond to a warm North Atlantic Ocean, in-phase with Atlantic multi-decadal ocean variability. Atmospheric blocking over the northern North Atlantic, which involves isolation of large regions of air from the westerly circulation for 5 days or more, influences fundamentally the ocean circulation and upper ocean properties by impacting wind patterns. Winters with clusters of more frequent blocking between Greenland and western Europe correspond to a warmer, more saline subpolar ocean. The correspondence between blocked westerly winds and warm ocean holds in recent decadal episodes (especially, 1996-2010). It also describes much longer-timescale Atlantic multidecadal ocean variability (AMV), including the extreme, pre-greenhouse-gas, northern warming of the 1930s-1960s. The space-time structure of the wind forcing associated with a blocked regime leads to weaker ocean gyres and weaker heat-exchange, both of which contribute to the warm phase of AMV. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A11L0169S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A11L0169S">Evidence of the Atlantic Multidecadal Oscillation driving multi-decadal variability of summertime surface air quality in the eastern United States: Implications for air quality management in the coming decades</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shen, L.; Mickley, L. J. 2016-12-01 Atlantic sea surface temperatures have a significant influence on the summertime meteorology and air quality in the eastern United States. In this study, we investigate the effect of the Atlantic Multidecadal Oscillation (AMO) on two key air pollutants, surface ozone and PM2.5, over the eastern United States. The shift of AMO from cold to warm phase increases surface air temperatures by 0.5 K across the East and reduces precipitation, resulting in a warmer and drier summer. By applying observed, present-day relationships between these pollutants and meteorological variables to a variety of observations and historical reanalysis datasets, we calculate the impacts of AMO on U.S. air quality. Our study reveals a multidecadal variability in mean summertime (JJA) maximum daily 8-hour (MDA8) ozone and surface PM2.5 concentrations in the eastern United States. In one-half cycle ( 30 years) of the AMO from negative to positive phase with constant anthropogenic emissions, JJA MDA8 ozone concentrations increase by 1-3 ppbv in the Northeast and 2-5 ppbv in the Great Plains; JJA PM2.5 concentrations increase by 0.8-1.2 μg m-3 in the Northeast and Southeast. The resulting impact on mortality rates is 4000 excess deaths per half cycle of AMO. We suggest that a complete picture of air quality management in coming decades requires consideration of the AMO influence. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP23C1424M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP23C1424M">Holocene Decadal to Multidecadal Hydrologic Variability in the Everglades: Climate and Implications for Ecosystem Management</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Moses, C. S.; Anderson, W. T.; Saunders, C.; Rebenack, C. 2009-12-01 The Florida Everglades are a complex, unique ecosystem. Adding to the complexity, a system of canals and gates control the flow of waters from central Florida southward into the Everglades, and ultimately Florida Bay and the Gulf of Mexico. With south Florida’s distinct wet and dry seasons, the hydrology has driven ecosystem evolution over the last 4-5 kya. However, since the 1920s the water content of the Everglades has largely been anthropogenically modulated, with the exception of the natural variability of evaporation and precipitation over the large area south of the Tamiami Trail. Because of the incredibly flat nature of the Everglades, small changes in the freshwater balance have substantial impacts on the diversity and distribution of organisms. Decadal and multidecadal variability in precipitation, hurricane incidence, and sea level rise all have important effects on the ecosystem. During the instrumental record, the natural precipitation across south Florida has been strongly influenced by combinations of the Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation, and ENSO. Here we discuss evidence of natural climate variability impacts on the ecosystem beyond the anthropogenic hydrological controls. Proxy environmental data from seeds, charcoal, and trees, plus the sparse, but available, instrumental records provide evidence of changes in the ecosystem over the Holocene, and suggest considerations for future management. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..813A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..813A">Regional influence of decadal to multidecadal Atlantic Oscillations during the last two millennia in Morocco, inferred from two high resolution δ18O speleothem records</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ait Brahim, Yassine; Sifeddine, Abdelfettah; Khodri, Myriam; Bouchaou, Lhoussaine; Cruz, Francisco W.; Pérez-Zanón, Núria; Wassenburg, Jasper A.; Cheng, Hai 2017-04-01 Climate projections predict substantial increase of extreme heats and drought occurrences during the coming decades in Morocco. It is however not clear what can be attributed to natural climate variability and to anthropogenic forcing, as hydroclimate variations observed in areas such as Morocco are highly influenced by the Atlantic climate modes. Since observational data sets are too short to resolve properly natural modes of variability acting on decadal to multidecadal timescales, high resolution paleoclimate reconstructions are the only alternative to reconstruct climate variability in the remote past. Herein, we present two high resolution and well dated speleothems oxygen isotope (δ18O) records sampled from Chaara and Ifoulki caves (located in Northeastern and Southwestern Morocco respectively) to investigate hydroclimate variations during the last 2000 years. Our results are supported by a monitoring network of δ18O in precipitation from 17 stations in Morocco. The new paleoclimate records are discussed in the light of existing continental and marine paleoclimate proxies in Morocco to identify significant correlations at various lead times with the main reconstructed oceanic and atmospheric variability modes and possible climate teleconnections that have potentially influenced the climate during the last two millennia in Morocco. The results reveal substantial decadal to multidecadal swings between dry and humid periods, consistent with regional paleorecords. Evidence of dry conditions exist during the Medieval Climate Anomaly (MCA) period and the Climate Warm Period (CWP) and humid conditions during the Little Ice Age (LIA) period. Statistical analyses suggest that the climate of southwestern Morocco remained under the combined influence of both the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO) over the last two millennia. Interestingly, the generally warmer MCA and colder LIA at longer multidecadal timescales probably influenced the regional climate in North Africa through the influence on Sahara Low which weakened and strengthened the mean moisture inflow from the Atlantic Ocean during the MCA and LIA respectively. Keywords: Speleothems, δ18O, Morocco, Hydroclimate, AMO, NAO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPC54A2232M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPC54A2232M">Toward a Reconstruction of the Atlantic Multidecadal Oscillation Using Shell-based Records from Coastal Northern Norway</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mette, M.; Wanamaker, A. D.; Carroll, M.; Ambrose, W. G., Jr.; Retelle, M. 2016-02-01 North Atlantic sea surface temperatures over the past 150 years have exhibited multidecadal variability, switching between relatively warm and cool periods, described by the Atlantic Multidecadal Oscillation (AMO). The influence, persistence, and causes of the AMO, however, are debated because instrumental records of North Atlantic sea surface temperatures only capture 2 cycles of this 60 to 80 year mode. Thus far, AMO reconstructions have been largely based on terrestrial archives despite the fact that the AMO is an oceanic mode. Proxy records from the marine realm are therefore necessary to better understand the behavior of the AMO over recent centuries. We present continuous, annual shell-based records of oxygen isotopes and growth from the long-lived marine bivalve Arctica islandica from coastal northern Norway (71 °N) from 1900-2012 that strongly relate to the instrumental AMO record (r = -0.59, p < 0.01). We performed calibration/verification analysis in order to assess the potential for these records to contribute to AMO reconstructions. We also compare our record with other proxy reconstructions of AMO variability over the past century. Our results show that extending shell-based records to past centuries will provide valuable information about AMO variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A22B..01D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A22B..01D">New Perspectives on the Role of Internal Variability in Regional Climate Change and Climate Model Evaluation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Deser, C. 2017-12-01 Natural climate variability occurs over a wide range of time and space scales as a result of processes intrinsic to the atmosphere, the ocean, and their coupled interactions. Such internally generated climate fluctuations pose significant challenges for the identification of externally forced climate signals such as those driven by volcanic eruptions or anthropogenic increases in greenhouse gases. This challenge is exacerbated for regional climate responses evaluated from short (< 50 years) data records. The limited duration of the observations also places strong constraints on how well the spatial and temporal characteristics of natural climate variability are known, especially on multi-decadal time scales. The observational constraints, in turn, pose challenges for evaluation of climate models, including their representation of internal variability and assessing the accuracy of their responses to natural and anthropogenic radiative forcings. A promising new approach to climate model assessment is the advent of large (10-100 member) "initial-condition" ensembles of climate change simulations with individual models. Such ensembles allow for accurate determination, and straightforward separation, of externally forced climate signals and internal climate variability on regional scales. The range of climate trajectories in a given model ensemble results from the fact that each simulation represents a particular sequence of internal variability superimposed upon a common forced response. This makes clear that nature's single realization is only one of many that could have unfolded. This perspective leads to a rethinking of approaches to climate model evaluation that incorporate observational uncertainty due to limited sampling of internal variability. Illustrative examples across a range of well-known climate phenomena including ENSO, volcanic eruptions, and anthropogenic climate change will be discussed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1228364','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1228364">Detection of Historical and Future Precipitation Variations and Extremes Over the Continental United States</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Anderson, Bruce T. 2015-12-11 Problem: The overall goal of this proposal is to detect observed seasonal-mean precipitation variations and extreme event occurrences over the United States. Detection, e.g. the process of demonstrating that an observed change in climate is unusual, first requires some means of estimating the range of internal variability absent any external drivers. Ideally, the internal variability would be derived from the observations themselves, however generally the observed variability is a confluence of both internal variability and variability in response to external drivers. Further, numerical climate models—the standard tool for detection studies—have their own estimates of intrinsic variability, which may differ substantiallymore » from that found in the observed system as well as other model systems. These problems are further compounded for weather and climate extremes, which as singular events are particularly ill-suited for detection studies because of their infrequent occurrence, limited spatial range, and underestimation within global and even regional numerical models. Rationale: As a basis for this research we will show how stochastic daily-precipitation models—models in which the simulated interannual-to-multidecadal precipitation variance is purely the result of the random evolution of daily precipitation events within a given time period—can be used to address many of these issues simultaneously. Through the novel application of these well-established models, we can first estimate the changes/trends in various means and extremes that can occur even with fixed daily-precipitation characteristics, e.g. that can occur simply as a result of the stochastic evolution of daily weather events within a given climate. Detection of a change in the observed climate—either naturally or anthropogenically forced—can then be defined as any change relative to this stochastic variability, e.g. as changes/trends in the means and extremes that could only have occurred through a change in the underlying climate. As such, this method is capable of detecting “hot spot” regions—as well as “flare ups” within the hot spot regions—that have experienced interannual to multi-decadal scale variations and trends in seasonal-mean precipitation and extreme events. Further by applying the same methods to numerical climate models we can discern the fidelity of the current-generation climate models in representing detectability within the observed climate system. In this way, we can objectively determine the utility of these model systems for performing detection studies of historical and future climate change.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1180C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1180C">On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Couldrey, Matthew; Oliver, Kevin; Yool, Andrew; Halloran, Paul; Achterberg, Eric 2016-04-01 The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2concentration gradient, ΔpCO2, and the temperature and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GBioC..30..787C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GBioC..30..787C">On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Couldrey, Matthew P.; Oliver, Kevin I. C.; Yool, Andrew; Halloran, Paul R.; Achterberg, Eric P. 2016-05-01 The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ΔpCO2, and the temperature- and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2 and k both contribute significantly to interannual F variability but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2, and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of nonseasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer-term flux variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSAH23A..06C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSAH23A..06C">On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Couldrey, M.; Oliver, K. I. C.; Yool, A.; Halloran, P. R.; Achterberg, E. P. 2016-02-01 The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ΔpCO2, and the temperature and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2 and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2 and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.1527W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.1527W">Evidence for multidecadal variability in US extreme sea level records</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wahl, Thomas; Chambers, Don P. 2015-03-01 We analyze a set of 20 tide gauge records covering the contiguous United States (US) coastline and the period from 1929 to 2013 to identify long-term trends and multidecadal variations in extreme sea levels (ESLs) relative to changes in mean sea level (MSL). Different data sampling and analysis techniques are applied to test the robustness of the results against the selected methodology. Significant but small long-term trends in ESLs above/below MSL are found at individual sites along most coastline stretches, but are mostly confined to the southeast coast and the winter season when storm surges are primarily driven by extratropical cyclones. We identify six regions with broadly coherent and considerable multidecadal ESL variations unrelated to MSL changes. Using a quasi-nonstationary extreme value analysis, we show that the latter would have caused variations in design relevant return water levels (50-200 year return periods) ranging from ˜10 cm to as much as 110 cm across the six regions. The results raise questions as to the applicability of the "MSL offset method," assuming that ESL changes are primarily driven by changes in MSL without allowing for distinct long-term trends or low-frequency variations. Identifying the coherent multidecadal ESL variability is crucial in order to understand the physical driving factors. Ultimately, this information must be included into coastal design and adaptation processes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP54A..02E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP54A..02E">Testing the Reconstruction Potential for North Pacific Circulation Anomalies inside the TraCE-21ka Paleoclimate Simulation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Elison Timm, O.; Flamholtz, W. M.; Li, S.; Massa, C.; Beilman, D. W. 2016-12-01 The motivation for this study was sparked by the idea that paleoclimate temperature and precipitation proxies provide sufficient information to make inferences about extratropical atmospheric circulation changes over the North Pacific during the Holocene. Typical targets for the circulation reconstruction problem include the strength and position of the Aleutian Low and the storm tracks. The reconstruction problem was investigated under idealized conditions using model simulation results from the TraCE-21ka transient climate simulation (http://www.cgd.ucar.edu/ccr/TraCE/), which covers the Last Glacial Maximum to present. It is demonstrated that modes of variability found on interannual to multidecadal timescales during the preindustrial era provide inadequate pattern for reconstructing long-term mean changes during the past 22,000 years. Our circulation reconstruction target was the geopotential height field at 500hPa (Z500) over the North Pacific Ocean during winter. We applied a field reconstruction method using Maximum Covariance Analysis (MCA). The MCA was applied to Z500 and surface temperatures as predictor information. The MCA was given model data containing interannual to multidecadal variability from the pre-industrial climate (1000BP-900BP). We worked with ten leading MCA modes in the reconstruction, which can reproduce about 90% of the covariability during the preindustrial period. Within the model simulation, we validated the field reconstructions against the model's circulation states over the last 22,000 years. Spatial skill scores show that the reconstruction skill drops significantly prior to the late Holocene. Reasons for the loss of reconstruction skill are due to the fact that externally forced climate changes do not resemble the internal modes of variability and that covariance between circulation and temperatures on interannual-multidecadal time scales changes with the background climate state. However, the reconstruction can be improved by including data from the early Holocene and the LGM era in the MCA. Based on these results, we advocate that paleoclimate model simulation results should be used define a set of first-guess pattern for the reconstruction of circulation anomalies from sparse and noisy proxy data. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ClDy...40.2801O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ClDy...40.2801O">Multidecadal simulation of coastal fog with a regional climate model</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> O'Brien, Travis A.; Sloan, Lisa C.; Chuang, Patrick Y.; Faloona, Ian C.; Johnstone, James A. 2013-06-01 In order to model stratocumulus clouds and coastal fog, we have coupled the University of Washington boundary layer model to the regional climate model, RegCM (RegCM-UW). By comparing fog occurrences observed at various coastal airports in the western United States, we show that RegCM-UW has success at modeling the spatial and temporal (diurnal, seasonal, and interannual) climatology of northern California coastal fog. The quality of the modeled fog estimate depends on whether coast-adjacent ocean or land grid cells are used; for the model runs shown here, the oceanic grid cells seem to be most appropriate. The interannual variability of oceanic northern California summertime fog, from a multi-decadal simulation, has a high and statistically significant correlation with the observed interannual variability ( r = 0.72), which indicates that RegCM-UW is capable of investigating the response of fog to long-term climatological forcing. While RegCM-UW has a number of aspects that would benefit from further investigation and development, RegCM-UW is a new tool for investigating the climatology of coastal fog and the physical processes that govern it. We expect that with appropriate physical parameterizations and moderate horizontal resolution, other climate models should be capable of simulating coastal fog. The source code for RegCM-UW is publicly available, under the GNU license, through the International Centre for Theoretical Physics. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...43.1357H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...43.1357H">Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Han, Weiqing; Meehl, Gerald A.; Hu, Aixue; Alexander, Michael A.; Yamagata, Toshio; Yuan, Dongliang; Ishii, Masayoshi; Pegion, Philip; Zheng, Jian; Hamlington, Benjamin D.; Quan, Xiao-Wei; Leben, Robert R. 2014-09-01 Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10-20 years) and multidecadal (>20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the "out of phase" relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces "in phase" effects on the WTP sea level variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS33D..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS33D..03R">Understanding multidecadal variability in ENSO amplitude</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Russell, A.; Gnanadesikan, A. 2013-12-01 Sea surface temperatures (SSTs) in the tropical Pacific vary as a result of the coupling between the ocean and atmosphere driven largely by the El Niño - Southern Oscillation (ENSO). ENSO has a large impact on the local climate and hydrology of the tropical Pacific, as well as broad-reaching effects on global climate. ENSO amplitude is known to vary on long timescales, which makes it very difficult to quantify its response to climate change and constrain the physical processes that drive it. In order to assess the extent of unforced multidecadal changes in ENSO variability, a linear regression of local SST changes is applied to the GFDL CM2.1 model 4000-yr pre-industrial control run. The resulting regression coefficient strengths, which represent the sensitivity of SST changes to thermocline depth and zonal wind stress, vary by up to a factor of 2 on multi-decadal time scales. This long-term modulation in ocean-atmosphere coupling is highly correlated with ENSO variability, but do not explain the reasons for such variability. Variation in the relationship between SST changes and wind stress points to a role for changing stratification in the central equatorial Pacific in modulating ENSO amplitudes with stronger stratification reducing the response to winds. The main driving mechanism we have identified for higher ENSO variance are changes in the response of zonal winds to SST anomalies. The shifting convection and precipitation patterns associated with the changing state of the atmosphere also contribute to the variability of the regression coefficients. These mechanisms drive much of the variability in ENSO amplitude and hence ocean-atmosphere coupling in the tropical Pacific. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ERL....12d4007M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ERL....12d4007M">Influence of internal variability on population exposure to hydroclimatic changes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mankin, Justin S.; Viviroli, Daniel; Mekonnen, Mesfin M.; Hoekstra, Arjen Y.; Horton, Radley M.; E Smerdon, Jason; Diffenbaugh, Noah S. 2017-04-01 Future freshwater supply, human water demand, and people’s exposure to water stress are subject to multiple sources of uncertainty, including unknown future pathways of fossil fuel and water consumption, and ‘irreducible’ uncertainty arising from internal climate system variability. Such internal variability can conceal forced hydroclimatic changes on multi-decadal timescales and near-continental spatial-scales. Using three projections of population growth, a large ensemble from a single Earth system model, and assuming stationary per capita water consumption, we quantify the likelihoods of future population exposure to increased hydroclimatic deficits, which we define as the average duration and magnitude by which evapotranspiration exceeds precipitation in a basin. We calculate that by 2060, ∽31%-35% of the global population will be exposed to >50% probability of hydroclimatic deficit increases that exceed existing hydrological storage, with up to 9% of people exposed to >90% probability. However, internal variability, which is an irreducible uncertainty in climate model predictions that is under-sampled in water resource projections, creates substantial uncertainty in predicted exposure: ∽86%-91% of people will reside where irreducible uncertainty spans the potential for both increases and decreases in sub-annual water deficits. In one population scenario, changes in exposure to large hydroclimate deficits vary from -3% to +6% of global population, a range arising entirely from internal variability. The uncertainty in risk arising from irreducible uncertainty in the precise pattern of hydroclimatic change, which is typically conflated with other uncertainties in projections, is critical for climate risk management that seeks to optimize adaptations that are robust to the full set of potential real-world outcomes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1291212-isolating-anthropogenic-component-arctic-warming','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1291212-isolating-anthropogenic-component-arctic-warming">Isolating the anthropogenic component of Arctic warming</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Chylek, Petr; Hengartner, Nicholas; Lesins, Glen; ... 2014-05-28 Structural equation modeling is used in statistical applications as both confirmatory and exploratory modeling to test models and to suggest the most plausible explanation for a relationship between the independent and the dependent variables. Although structural analysis cannot prove causation, it can suggest the most plausible set of factors that influence the observed variable. Here, we apply structural model analysis to the annual mean Arctic surface air temperature from 1900 to 2012 to find the most effective set of predictors and to isolate the anthropogenic component of the recent Arctic warming by subtracting the effects of natural forcing and variabilitymore » from the observed temperature. We also find that anthropogenic greenhouse gases and aerosols radiative forcing and the Atlantic Multidecadal Oscillation internal mode dominate Arctic temperature variability. Finally, our structural model analysis of observational data suggests that about half of the recent Arctic warming of 0.64 K/decade may have anthropogenic causes.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NatGe...6..362K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NatGe...6..362K">Caribbean coral growth influenced by anthropogenic aerosol emissions</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kwiatkowski, Lester; Cox, Peter M.; Economou, Theo; Halloran, Paul R.; Mumby, Peter J.; Booth, Ben B. B.; Carilli, Jessica; Guzman, Hector M. 2013-05-01 Coral growth rates are highly dependent on environmental variables such as sea surface temperature and solar irradiance. Multi-decadal variability in coral growth rates has been documented throughout the Caribbean over the past 150-200 years, and linked to variations in Atlantic sea surface temperatures. Multi-decadal variability in sea surface temperatures in the North Atlantic, in turn, has been linked to volcanic and anthropogenic aerosol forcing. Here, we examine the drivers of changes in coral growth rates in the western Caribbean between 1880 and 2000, using previously published coral growth chronologies from two sites in the region, and a numerical model. Changes in coral growth rates over this period coincided with variations in sea surface temperature and incoming short-wave radiation. Our model simulations show that variations in the concentration of anthropogenic aerosols caused variations in sea surface temperature and incoming radiation in the second half of the twentieth century. Before this, variations in volcanic aerosols may have played a more important role. With the exception of extreme mass bleaching events, we suggest that neither climate change from greenhouse-gas emissions nor ocean acidification is necessarily the driver of multi-decadal variations in growth rates at some Caribbean locations. Rather, the cause may be regional climate change due to volcanic and anthropogenic aerosol emissions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160004955&hterms=moderation+research&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmoderation%2Bresearch','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160004955&hterms=moderation+research&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmoderation%2Bresearch">North American Megadroughts in the Common Era: Reconstructions and Simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Cook, Benjamin I.; Cook, Edward R.; Smerdon, Jason E.; Seager, Richard; Williams, A. Park; Coats, Sloan; Stahle, David W.; Villanueva Diaz, Jose 2016-01-01 During the Medieval Climate Anomaly (MCA), Western North America experienced episodes of intense aridity that persisted for multiple decades or longer. These megadroughts are well documented in many proxy records, but the causal mechanisms are poorly understood. General circulation models (GCMs) simulate megadroughts, but do not reproduce the temporal clustering of events during the MCA, suggesting they are not caused by the time history of volcanic or solar forcing. Instead, GCMs generate megadroughts through (1) internal atmospheric variability, (2) sea-surface temperatures, and (3) land surface and dust aerosol feedbacks. While no hypothesis has been definitively rejected, and no GCM has accurately reproduced all features (e.g., timing, duration, and extent) of any specific megadrought, their persistence suggests a role for processes that impart memory to the climate system (land surface and ocean dynamics). Over the 21st century, GCMs project an increase in the risk of megadrought occurrence through greenhouse gas forced reductions in precipitation and increases in evaporative demand. This drying is robust across models and multiple drought indicators, but major uncertainties still need to be resolved. These include the potential moderation of vegetation evaporative losses at higher atmospheric [CO2], variations in land surface model complexity, and decadal to multidecadal modes of natural climate variability that could delay or advance onset of aridification over the the next several decades. Because future droughts will arise from both natural variability and greenhouse gas forced trends in hydroclimate, improving our understanding of the natural drivers of persistent multidecadal megadroughts should be a major research priority. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CliPD...8.5455K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CliPD...8.5455K">On the origin of multi-decadal to centennial Greenland temperature anomalies over the past 800 yr</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kobashi, T.; Shindell, D. T.; Kodera, K.; Box, J. E.; Nakaegawa, T.; Kawamura, K. 2012-11-01 The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies associated with accelerating sea level rise. However, the causes of multi-decadal-to-centennial temperature changes in Greenland are not well understood, largely owing to short observational records. To examine the causes of the Greenland temperature variability, we calculated the Greenland temperature anomalies (GTA(G-NH)) over the past 800 yr by subtracting the standardised NH temperature from the standardised Greenland temperature. It decomposes the Greenland temperature variation into background climate (NH); Polar amplification; and Regional variability (GTA(G-NH)). The Central Greenland polar amplification factor as expressed by the variance ratio = Greenland/NH is 2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The GTA explains 31-35% of the variation of Greenland temperature in the multi-decadal-to-centennial time scale over the past 800 yr. Another orthogonal component of the Greenland and NH temperatures, GTP(G+NH) (Greenland temperature plus = standardized Greenland temperature + standardized NH temperature) exhibited the multi-decadal variations that were likely induced by large volcanic eruptions, increasing greenhouse gasses, and internal variation of climate. We found that the GTA(G-NH) has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modelling indicates that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and to associated changes in northward oceanic heat transport. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP23A2288L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP23A2288L">The Global Warming Hiatus Tied to the North Atlantic Oscillation and Its Prediction</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, J.; Sun, C. 2015-12-01 The twentieth century Northern Hemisphere mean surface temperature (NHT) is characterized by a multidecadal warming-cooling-warming pattern followed by a flat trend since about 2000 (recent warming hiatus). Here we demonstrate that the multidcadal variability in NHT including the recent warming hiatus is tied to the North Atlantic Oscillation (NAO) and the NAO is implicated as a useful predictor of NHT multidecadal variability. Observational analysis shows that the NAO leads both the detrended NHT and oceanic Atlantic Multidecadal Oscillation (AMO) by 15-20 years. Theoretical analysis illuminates that the NAO precedes NHT multidecadal variability through its delayed effect on the AMO due to the large thermal inertia associated with slow oceanic processes. The CCSM4 model is employed to investigate possible physical mechanisms. The positive NAO forces the strengthening of the Atlantic meridional overturning circulation (AMOC) and induces a basin-wide uniform sea surface temperature (SST) warming that corresponds to the AMO. The SST field exhibits a delayed response to the preceding enhanced AMOC, and shows a pattern similar to the North Atlantic tripole (NAT), with SST warming in the northern North Atlantic and cooling in the southern part. This SST pattern (negative NAT phase) may lead to an atmospheric response that resembles the negative NAO phase, and subsequently the oscillation proceeds, but in the opposite sense. Based on these mechanisms, a simple delayed oscillator model is established to explain the quasi-periodic multidecadal variability of the NAO. The magnitude of the NAO forcing of the AMOC/AMO and the time delay of the AMOC/AMO feedback are two key parameters of the delayed oscillator. For a given set of parameters, the quasi 60-year cycle of the NAO can be well predicted. This delayed oscillator model is useful for understanding of the oscillatory mechanism of the NAO, which has potential for decadal predictions as well as the interpretation of proxy data records. An NAO-based linear model is therefore established to predict the NHT, which gives an excellent hindcast for NHT in 1971-2011 with the recent flat trend well predicted. NHT in 2012-2027 is predicted to fall slightly over the next decades, due to the recent NAO decadal weakening that temporarily offsets the anthropogenically induced warming. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC42B..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC42B..01C">The role of clouds in driving North Atlantic multi-decadal climate variability in observations and models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Clement, A. C.; Bellomo, K.; Murphy, L. 2013-12-01 Large scale warming and cooling periods of the North Atlantic is known as the Atlantic Multidecadal Oscillation (AMO). The pattern of warming and cooling in the North Atlantic Ocean over the 20th century that has a characteristic spatial structure with maximum warming in the mid-latitudes and subtropics. This has been most often attributed to changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC), which in turn affects poleward heat transport. A recent modeling study by Booth et al. (2012), however, suggested that aerosols can explain both the spatial pattern and temporal history of Atlantic SST through indirect effects of aerosols on cloud cover; although this idea is controversial (Zhang et al., 2013). We have found observational evidence that changes in cloud amount can drive SST changes on multi-decadal timescale. We hypothesize that a positive local feedback between SST and cloud radiative effect amplifies SST and gives rise to the observed pattern of SST change. During cool North Atlantic periods, a southward shift of the ITCZ strengthens the trade winds in the tropical North Atlantic and increases low-level cloud cover, which acts to amplify the SST cooling in the North Atlantic. During warm periods in the North Atlantic, the opposite response occurs. We are testing whether the amplitude of this feedback is realistically simulated in the CMIP5 models, and whether inter-model differences in the amplitude of the feedback can explain differences in model simulations of Atlantic multi-decadal variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JCli...30.5265S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JCli...30.5265S">Indo-Pacific Variability on Seasonal to Multidecadal Time Scales. Part I: Intrinsic SST Modes in Models and Observations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Slawinska, Joanna; Giannakis, Dimitrios 2017-07-01 The variability of Indo-Pacific SST on seasonal to multidecadal timescales is investigated using a recently introduced technique called nonlinear Laplacian spectral analysis (NLSA). Through this technique, drawbacks associated with ad hoc pre-filtering of the input data are avoided, enabling recovery of low-frequency and intermittent modes not previously accessible via classical approaches. Here, a multiscale hierarchy of spatiotemporal modes is identified for Indo-Pacific SST in millennial control runs of CCSM4 and CM3 and in HadISST data. On interannual timescales, a mode with spatiotemporal patterns corresponding to the fundamental component of ENSO emerges, along with ENSO-modulated annual modes consistent with combination mode theory. The ENSO combination modes also feature prominent activity in the Indian Ocean, explaining significant fraction of the SST variance in regions associated with the Indian Ocean dipole. A pattern resembling the tropospheric biennial oscillation emerges in addition to ENSO and the associated combination modes. On multidecadal timescales, the dominant NLSA mode in the model data is predominantly active in the western tropical Pacific. The interdecadal Pacific oscillation also emerges as a distinct NLSA mode, though with smaller explained variance than the western Pacific multidecadal mode. Analogous modes on interannual and decadal timescales are also identified in HadISST data for the industrial era, as well as in model data of comparable timespan, though decadal modes are either absent or of degraded quality in these datasets. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1245323-grace-era-terrestrial-water-trends-driven-anthropogenic-climate-change','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1245323-grace-era-terrestrial-water-trends-driven-anthropogenic-climate-change">Are GRACE-era terrestrial water trends driven by anthropogenic climate change?</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Fasullo, J. T.; Lawrence, D. M.; Swenson, S. C. 2016-01-01 To provide context for observed trends in terrestrial water storage (TWS) during GRACE (2003–2014), trends and variability in the CESM1-CAM5 Large Ensemble (LE) are examined. Motivated in part by the anomalous nature of climate variability during GRACE, the characteristics of both forced change and internal modes are quantified and their influences on observations are estimated. Trends during the GRACE era in the LE are dominated by internal variability rather than by the forced response, with TWS anomalies in much of the Americas, eastern Australia, Africa, and southwestern Eurasia largely attributable to the negative phases of the Pacific Decadal Oscillation (PDO)more » and Atlantic Multidecadal Oscillation (AMO). While similarities between observed trends and the model-inferred forced response also exist, it is inappropriate to attribute such trends mainly to anthropogenic forcing. For several key river basins, trends in the mean state and interannual variability and the time at which the forced response exceeds background variability are also estimated while aspects of global mean TWS, including changes in its annual amplitude and decadal trends, are quantified. Lastly, the findings highlight the challenge of detecting anthropogenic climate change in temporally finite satellite datasets and underscore the benefit of utilizing models in the interpretation of the observed record.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/biblio/1245323-grace-era-terrestrial-water-trends-driven-anthropogenic-climate-change','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1245323-grace-era-terrestrial-water-trends-driven-anthropogenic-climate-change">Are GRACE-era terrestrial water trends driven by anthropogenic climate change?</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fasullo, J. T.; Lawrence, D. M.; Swenson, S. C. To provide context for observed trends in terrestrial water storage (TWS) during GRACE (2003–2014), trends and variability in the CESM1-CAM5 Large Ensemble (LE) are examined. Motivated in part by the anomalous nature of climate variability during GRACE, the characteristics of both forced change and internal modes are quantified and their influences on observations are estimated. Trends during the GRACE era in the LE are dominated by internal variability rather than by the forced response, with TWS anomalies in much of the Americas, eastern Australia, Africa, and southwestern Eurasia largely attributable to the negative phases of the Pacific Decadal Oscillation (PDO)more » and Atlantic Multidecadal Oscillation (AMO). While similarities between observed trends and the model-inferred forced response also exist, it is inappropriate to attribute such trends mainly to anthropogenic forcing. For several key river basins, trends in the mean state and interannual variability and the time at which the forced response exceeds background variability are also estimated while aspects of global mean TWS, including changes in its annual amplitude and decadal trends, are quantified. Lastly, the findings highlight the challenge of detecting anthropogenic climate change in temporally finite satellite datasets and underscore the benefit of utilizing models in the interpretation of the observed record.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GPC...151...92Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GPC...151...92Z">Atlantic multi-decadal oscillation influence on weather regimes over Europe and the Mediterranean in spring and summer</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zampieri, M.; Toreti, A.; Schindler, A.; Scoccimarro, E.; Gualdi, S. 2017-04-01 We analyze the influence of the Atlantic sea surface temperature multi-decadal variability on the day-by-day sequence of large-scale atmospheric circulation patterns (i.e. the ;weather regimes;) over the Euro-Atlantic region. In particular, we examine of occurrence of weather regimes from 1871 to present. This analysis is conducted by applying a clustering technique on the daily mean sea level pressure field provided by the 20th Century Reanalysis project, which was successfully applied in other studies focused on the Atlantic Multi-decadal Oscillation (AMO). In spring and summer, results show significant changes in the frequencies of certain weather regimes associated with the phase shifts of the AMO. These changes are consistent with the seasonal surface pressure, precipitation, and temperature anomalies associated with the AMO shifts in Europe. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP31A1269S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP31A1269S">Precipitation, temperature, and teleconnection signals across the combined North American, Monsoon Asia, and Old World Drought Atlases</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Smerdon, J. E.; Baek, S. H.; Coats, S.; Williams, P.; Cook, B.; Cook, E. R.; Seager, R. 2017-12-01 The tree-ring-based North American Drought Atlas (NADA), Monsoon Asia Drought Atlas (MADA), and Old World Drought Atlas (OWDA) collectively yield a near-hemispheric gridded reconstruction of hydroclimate variability over the last millennium. To test the robustness of the large-scale representation of hydroclimate variability across the drought atlases, the joint expression of seasonal climate variability and teleconnections in the NADA, MADA, and OWDA are compared against two global, observation-based PDSI products. Predominantly positive (negative) correlations are determined between seasonal precipitation (surface air temperature) and collocated tree-ring-based PDSI, with average Pearson's correlation coefficients increasing in magnitude from boreal winter to summer. For precipitation, these correlations tend to be stronger in the boreal winter and summer when calculated for the observed PDSI record, while remaining similar for temperature. Notwithstanding these differences, the drought atlases robustly express teleconnection patterns associated with the El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). These expressions exist in the drought atlas estimates of boreal summer PDSI despite the fact that these modes of climate variability are dominant in boreal winter, with the exception of the Atlantic Multidecadal Oscillation. ENSO and NAO teleconnection patterns in the drought atlases are particularly consistent with their well-known dominant expressions in boreal winter and over the OWDA domain, respectively. Collectively, our findings confirm that the joint Northern Hemisphere drought atlases robustly reflect large-scale patterns of hydroclimate variability on seasonal to multidecadal timescales over the 20th century and are likely to provide similarly robust estimates of hydroclimate variability prior to the existence of widespread instrumental data. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1306152','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1306152"></a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Elliott, Elizabeth J.; Yu, Sungduk; Kooperman, Gabriel J. The sensitivities of simulated mesoscale convective systems (MCSs) in the central U.S. to microphysics and grid configuration are evaluated here in a global climate model (GCM) that also permits global-scale feedbacks and variability. Since conventional GCMs do not simulate MCSs, studying their sensitivities in a global framework useful for climate change simulations has not previously been possible. To date, MCS sensitivity experiments have relied on controlled cloud resolving model (CRM) studies with limited domains, which avoid internal variability and neglect feedbacks between local convection and larger-scale dynamics. However, recent work with superparameterized (SP) GCMs has shown that eastward propagating MCS-likemore » events are captured when embedded CRMs replace convective parameterizations. This study uses a SP version of the Community Atmosphere Model version 5 (SP-CAM5) to evaluate MCS sensitivities, applying an objective empirical orthogonal function algorithm to identify MCS-like events, and harmonizing composite storms to account for seasonal and spatial heterogeneity. A five-summer control simulation is used to assess the magnitude of internal and interannual variability relative to 10 sensitivity experiments with varied CRM parameters, including ice fall speed, one-moment and two-moment microphysics, and grid spacing. MCS sensitivities were found to be subtle with respect to internal variability, and indicate that ensembles of over 100 storms may be necessary to detect robust differences in SP-GCMs. Furthermore, these results emphasize that the properties of MCSs can vary widely across individual events, and improving their representation in global simulations with significant internal variability may require comparison to long (multidecadal) time series of observed events rather than single season field campaigns.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CliPa..14..101N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CliPa..14..101N">Climate variability in the subarctic area for the last 2 millennia</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nicolle, Marie; Debret, Maxime; Massei, Nicolas; Colin, Christophe; deVernal, Anne; Divine, Dmitry; Werner, Johannes P.; Hormes, Anne; Korhola, Atte; Linderholm, Hans W. 2018-01-01 To put recent climate change in perspective, it is necessary to extend the instrumental climate records with proxy data from paleoclimate archives. Arctic climate variability for the last 2 millennia has been investigated using statistical and signal analyses from three regionally averaged records from the North Atlantic, Siberia and Alaska based on many types of proxy data archived in the Arctic 2k database v1.1.1. In the North Atlantic and Alaska, the major climatic trend is characterized by long-term cooling interrupted by recent warming that started at the beginning of the 19th century. This cooling is visible in the Siberian region at two sites, warming at the others. The cooling of the Little Ice Age (LIA) was identified from the individual series, but it is characterized by wide-range spatial and temporal expression of climate variability, in contrary to the Medieval Climate Anomaly. The LIA started at the earliest by around AD 1200 and ended at the latest in the middle of the 20th century. The widespread temporal coverage of the LIA did not show regional consistency or particular spatial distribution and did not show a relationship with archive or proxy type either. A focus on the last 2 centuries shows a recent warming characterized by a well-marked warming trend parallel with increasing greenhouse gas emissions. It also shows a multidecadal variability likely due to natural processes acting on the internal climate system on a regional scale. A ˜ 16-30-year cycle is found in Alaska and seems to be linked to the Pacific Decadal Oscillation, whereas ˜ 20-30- and ˜ 50-90-year periodicities characterize the North Atlantic climate variability, likely in relation with the Atlantic Multidecadal Oscillation. These regional features are probably linked to the sea ice cover fluctuations through ice-temperature positive feedback. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008410','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008410">Atmospheric Blocking and Atlantic Multi-Decadal Ocean Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L. 2011-01-01 Atmospheric blocking over the northern North Atlantic involves isolation of large regions of air from the westerly circulation for 5-14 days or more. From a recent 20th century atmospheric reanalysis (1,2) winters with more frequent blocking persist over several decades and correspond to a warm North Atlantic Ocean, in-phase with Atlantic multi-decadal ocean variability (AMV). Ocean circulation is forced by wind-stress curl and related air/sea heat exchange, and we find that their space-time structure is associated with dominant blocking patterns: weaker ocean gyres and weaker heat exchange contribute to the warm phase of AMV. Increased blocking activity extending from Greenland to British Isles is evident when winter blocking days of the cold years (1900-1929) are subtracted from those of the warm years (1939-1968). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28892858','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28892858">Spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhang, Min; Zhang, Yuanling; Shu, Qi; Zhao, Chang; Wang, Gang; Wu, Zhaohua; Qiao, Fangli 2018-01-15 Analyses of the chlorophyll a concentration (chla) from satellite ocean color products have suggested the decadal-scale variability of chla linked to the climate change. The decadal-scale variability in chla is both spatially and temporally non-uniform. We need to understand the spatiotemporal evolution of chla in decadal or multi-decadal timescales to better evaluate its linkage to climate variability. Here, the spatiotemporal evolution of the chla trend in the North Atlantic Ocean for the period 1997-2016 is analyzed using the multidimensional ensemble empirical mode decomposition method. We find that this variable trend signal of chla shows a dipole pattern between the subpolar gyre and along the Gulf Stream path, and propagation along the opposite direction of the North Atlantic Current. This propagation signal has an overlapping variability of approximately twenty years. Our findings suggest that the spatiotemporal evolution of chla during the two most recent decades is part of the multidecadal variations and possibly regulated by the changes of Atlantic Meridional Overturning Circulation, whereas the mechanisms of such evolution patterns still need to be explored. Copyright © 2017 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP24B..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP24B..07K">A Zonal Mode in the Indian Ocean over the Past Millennium? Isotopic Evidence from Continental Climate Archives and Model Simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Konecky, B.; Russell, J. M.; Vuille, M.; Rodysill, J. R.; Cohen, L. R.; Chuman, A. F.; Huang, Y. 2011-12-01 We present new evidence for multi-decadal to millennial scale hydro-climatic change in the continental Indian Ocean region over the past two millennia. We assess regional hydrological variability using new records of the δD of terrestrial plant waxes from the sediments of several lakes in tropical East Africa and Indonesia. We compare these new data to previous δ18O and δD records from the region and interpret these results in light of an isotope-enabled climate model simulation of the past 130 years. Long-term trends in our data support a southward migration of the Intertropical Convergence Zone (ITCZ)'s mean position over the past millennium, bringing progressively wetter conditions and D-depleted waxes to our southernmost site (~8°S) starting around 950 C.E. while maintaining overall wet conditions at our northernmost site (~0°N) until the end of the 19th century. Superimposed on this long-term trend are a series of pronounced, multi-decadal to centennial scale isotopic excursions that are of the same timing but in opposite directions on the two sides of the Indian Ocean. These zonally asymmetric isotopic fluctuations become progressively more pronounced beginning around 1400 C.E., with the onset of Little Ice Age cool conditions recorded in sea surface temperature reconstructions from the Northern Hemisphere and the Indo-Pacific Warm Pool (IPWP). Previous work in the IPWP region suggests cooler SST, reduced boreal summer Asian monsoon intensity, and less ENSO-like activity during the Little Ice Age [Oppo et al., 2009, Nature 460:1113, and references therein], although recent paleolimnological reconstructions from Java indicate punctuated droughts during this time [Rodysill et al., 2010, Eos Trans. AGU, 91(52), Fall Meet. Suppl., Abstract PP51B-04]. Our records suggest that multi-decadal to centennial precipitation variability was in fact enhanced during this time period in parts of equatorial East Africa and western Indonesia. The direction of isotopic excursions in our records resembles the variations associated with the negative mode of the Indian Ocean Zonal Mode (IOZM) observed in modern seasonal data. To investigate the potential for an IOZM-like mode to explain multi-decadal phenomena over the past millennium, we compare the variations in our records and in other previously published δ18O and δD records from the region to a model simulation of the past 130 years by the Stable Water Isotope INtercomparison Group (SWING). We find significant multi-decadal isotopic variability associated with the IOZM in the SWING experiment. We analyze the isotopic signature associated with both the IOZM and ENSO and use these findings to help interpret the multi-decadal variability evident in continental paleoclimate archives over the past millennium in the Indian Ocean region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.2472M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.2472M">The role of historical forcings in simulating the observed Atlantic multidecadal oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Murphy, Lisa N.; Bellomo, Katinka; Cane, Mark; Clement, Amy 2017-03-01 We analyze the Atlantic multidecadal oscillation (AMO) in the preindustrial (PI) and historical (HIST) simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to assess the drivers of the observed AMO from 1865 to 2005. We draw 141 year samples from the 41 CMIP5 model's PI runs and compare the correlation and variance between the observed AMO and the simulated PI and HIST AMO. The correlation coefficients in 38 forced (HIST) models are above the 90% confidence level and explain up to 56% of the observed variance. The probability that any of the unforced (PI) models do as well is less than 3% in 31 models. Multidecadal variability is larger in 39 CMIP5 HIST simulations and in all HIST members of the Community Earth System Model Large Ensemble than their corresponding PI. We conclude that there is an essential role for external forcing in driving the observed AMO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP23A1823W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP23A1823W">A Tropical View of Atlantic Multidecadal SST Variability over the Last Two Millennia</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wurtzel, J. B.; Black, D. E.; Thunell, R.; Peterson, L. C.; Tappa, E. J.; Rahman, S. 2011-12-01 Instrumental and proxy-reconstructions show the existence of a 60-80 year periodicity in Atlantic sea surface temperature (SST), known as the Atlantic Multidecadal Oscillation (AMO). The AMO is correlated with circum-tropical Atlantic climate phenomena such as Sahel and Nordeste rainfall, as well as Atlantic hurricane patterns. Though it has been suggested that the AMO is controlled by thermohaline circulation, much debate exists as to whether the SST fluctuations are a result of anthropogenic forcing or natural climate variability. Our ability to address this issue has been limited by instrumental SST records that rarely extend back more than 50-100 years and proxy reconstructions that are largely terrestrial-based. Here we present a high-resolution marine sediment-derived reconstruction of seasonal tropical Atlantic SSTs from the Cariaco Basin spanning the past two millennia that is correlated with instrumental SSTs and the AMO for the period of overlap. The full record demonstrates that seasonality is largely controlled by variations in winter/spring SST. Wavelet analysis of the proxy data suggest that variability in the 60-80 year band evolved 250 years ago, while 40-60 year periodicities dominate earlier parts of the record. At least over the last millennia, multidecadal- and centennial- scale SST variability in the tropical Atlantic appears related to Atlantic meridional overturning circulation (AMOC) fluctuations and its associated northward heat transport that in turn may be driven by solar variability. An inverse correlation between the tropical proxy annual average SST record and Δ14C indicates that the tropics experienced positive SST anomalies during times of reduced solar activity, possibly as a result of decreased AMOC strength (Figure 1). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ClDy...39.1431S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ClDy...39.1431S">Pacific and Atlantic influences on Mesoamerican climate over the past millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stahle, D. W.; Burnette, D. J.; Diaz, J. Villanueva; Heim, R. R.; Fye, F. K.; Paredes, J. Cerano; Soto, R. Acuna; Cleaveland, M. K. 2012-09-01 A new tree-ring reconstruction of the Palmer Drought Severity Index (PDSI) for Mesoamerica from AD 771 to 2008 identifies megadroughts more severe and sustained than any witnessed during the twentieth century. Correlation analyses indicate strong forcing of instrumental and reconstructed June PDSI over Mesoamerica from the El Niño/Southern Oscillation (ENSO). Spectral analyses of the 1,238-year reconstruction indicate significant concentrations of variance at ENSO, sub-decadal, bi-decadal, and multidecadal timescales. Instrumental and model-based analyses indicate that the Atlantic Multidecadal Oscillation is important to warm season climate variability over Mexico. Ocean-atmospheric variability in the Atlantic is not strongly correlated with the June PDSI reconstruction during the instrumental era, but may be responsible for the strong multidecadal variance detected in the reconstruction episodically over the past millennium. June drought indices in Mesoamerica are negatively correlated with gridded June PDSI over the United States from 1950 to 2005, based on both instrumental and reconstructed data. Interannual variability in this latitudinal moisture gradient is due in part to ENSO forcing, where warm events favor wet June PDSI conditions over the southern US and northern Mexico, but dryness over central and southern Mexico (Mesoamerica). Strong anti-phasing between multidecadal regimes of tree-ring reconstructed June PDSI over Mesoamerica and reconstructed summer (JJA) PDSI over the Southwest has also been detected episodically over the past millennium, including the 1950-1960s when La Niña and warm Atlantic SSTs prevailed, and the 1980-1990s when El Niño and cold Atlantic SSTs prevailed. Several Mesoamerican megadroughts are reconstructed when wetness prevailed over the Southwest, including the early tenth century Terminal Classic Drought, implicating El Niño and Atlantic SSTs in this intense and widespread drought that may have contributed to social changes in ancient Mexico. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.476...34D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.476...34D">Improved spectral comparisons of paleoclimate models and observations via proxy system modeling: Implications for multi-decadal variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dee, S. G.; Parsons, L. A.; Loope, G. R.; Overpeck, J. T.; Ault, T. R.; Emile-Geay, J. 2017-10-01 The spectral characteristics of paleoclimate observations spanning the last millennium suggest the presence of significant low-frequency (multi-decadal to centennial scale) variability in the climate system. Since this low-frequency climate variability is critical for climate predictions on societally-relevant scales, it is essential to establish whether General Circulation models (GCMs) are able to simulate it faithfully. Recent studies find large discrepancies between models and paleoclimate data at low frequencies, prompting concerns surrounding the ability of GCMs to predict long-term, high-magnitude variability under greenhouse forcing (Laepple and Huybers, 2014a, 2014b). However, efforts to ground climate model simulations directly in paleoclimate observations are impeded by fundamental differences between models and the proxy data: proxy systems often record a multivariate and/or nonlinear response to climate, precluding a direct comparison to GCM output. In this paper we bridge this gap via a forward proxy modeling approach, coupled to an isotope-enabled GCM. This allows us to disentangle the various contributions to signals embedded in ice cores, speleothem calcite, coral aragonite, tree-ring width, and tree-ring cellulose. The paper addresses the following questions: (1) do forward-modeled ;pseudoproxies; exhibit variability comparable to proxy data? (2) if not, which processes alter the shape of the spectrum of simulated climate variability, and are these processes broadly distinguishable from climate? We apply our method to representative case studies, and broaden these insights with an analysis of the PAGES2k database (PAGES2K Consortium, 2013). We find that current proxy system models (PSMs) can help resolve model-data discrepancies on interannual to decadal timescales, but cannot account for the mismatch in variance on multi-decadal to centennial timescales. We conclude that, specific to this set of PSMs and isotope-enabled model, the paleoclimate record may exhibit larger low-frequency variability than GCMs currently simulate, indicative of incomplete physics and/or forcings. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8985005','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8985005">Predictability of North Atlantic Multidecadal Climate Variability</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Griffies; Bryan 1997-01-10 Atmospheric weather systems become unpredictable beyond a few weeks, but climate variations can be predictable over much longer periods because of the coupling of the ocean and atmosphere. With the use of a global coupled ocean-atmosphere model, it is shown that the North Atlantic may have climatic predictability on the order of a decade or longer. These results suggest that variations of the dominant multidecadal sea surface temperature patterns in the North Atlantic, which have been associated with changes in climate over Eurasia, can be predicted if an adequate and sustainable system for monitoring the Atlantic Ocean exists. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP22A..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP22A..04Z">Model simulations and proxy-based reconstructions for the European region in the past millennium (Invited)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zorita, E. 2009-12-01 One of the objectives when comparing simulations of past climates to proxy-based climate reconstructions is to asses the skill of climate models to simulate climate change. This comparison may accomplished at large spatial scales, for instance the evolution of simulated and reconstructed Northern Hemisphere annual temperature, or at regional or point scales. In both approaches a 'fair' comparison has to take into account different aspects that affect the inevitable uncertainties and biases in the simulations and in the reconstructions. These efforts face a trade-off: climate models are believed to be more skillful at large hemispheric scales, but climate reconstructions are these scales are burdened by the spatial distribution of available proxies and by methodological issues surrounding the statistical method used to translate the proxy information into large-spatial averages. Furthermore, the internal climatic noise at large hemispheric scales is low, so that the sampling uncertainty tends to be also low. On the other hand, the skill of climate models at regional scales is limited by the coarse spatial resolution, which hinders a faithful representation of aspects important for the regional climate. At small spatial scales, the reconstruction of past climate probably faces less methodological problems if information from different proxies is available. The internal climatic variability at regional scales is, however, high. In this contribution some examples of the different issues faced when comparing simulation and reconstructions at small spatial scales in the past millennium are discussed. These examples comprise reconstructions from dendrochronological data and from historical documentary data in Europe and climate simulations with global and regional models. These examples indicate that the centennial climate variations can offer a reasonable target to assess the skill of global climate models and of proxy-based reconstructions, even at small spatial scales. However, as the focus shifts towards higher frequency variability, decadal or multidecadal, the need for larger simulation ensembles becomes more evident. Nevertheless,the comparison at these time scales may expose some lines of research on the origin of multidecadal regional climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2308Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2308Y">On climate prediction: how much can we expect from climate memory?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yuan, Naiming; Huang, Yan; Duan, Jianping; Zhu, Congwen; Xoplaki, Elena; Luterbacher, Jürg 2018-03-01 Slowing variability in climate system is an important source of climate predictability. However, it is still challenging for current dynamical models to fully capture the variability as well as its impacts on future climate. In this study, instead of simulating the internal multi-scale oscillations in dynamical models, we discussed the effects of internal variability in terms of climate memory. By decomposing climate state x(t) at a certain time point t into memory part M(t) and non-memory part ɛ (t) , climate memory effects from the past 30 years on climate prediction are quantified. For variables with strong climate memory, high variance (over 20% ) in x(t) is explained by the memory part M(t), and the effects of climate memory are non-negligible for most climate variables, but the precipitation. Regarding of multi-steps climate prediction, a power law decay of the explained variance was found, indicating long-lasting climate memory effects. The explained variances by climate memory can remain to be higher than 10% for more than 10 time steps. Accordingly, past climate conditions can affect both short (monthly) and long-term (interannual, decadal, or even multidecadal) climate predictions. With the memory part M(t) precisely calculated from Fractional Integral Statistical Model, one only needs to focus on the non-memory part ɛ (t) , which is an important quantity that determines climate predictive skills. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A41N..04H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A41N..04H">Observed and simulated changes in Antarctic sea ice and sea level pressure: anthropogenic or natural variability? (Invited)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hobbs, W. R. 2013-12-01 Statistically-significant changes in Antarctic sea ice cover and the overlying atmosphere have been observed over the last 30 years, but there is an open question of whether these changes are due to multi-decadal natural variability or an anthropogenically-forced response. A number of recent papers have shown that the slight increase in total sea ice cover is within the bounds of internal variability exhibited by coupled climate models in the CMIP5 suite. Modelled changes for the same time period generally show a decrease, but again with a magnitude that is within internal variability. However, in contrast to the Arctic, sea ice tends in the Antarctic are spatially highly heterogeneous, and consideration of the total ice cover may mask important regional signals. In this work, a robust ';fingerprinting' approach is used to show that the observed spatial pattern of sea ice trends is in fact outside simulated natural variability in west Antarctic, and furthermore that the CMIP5 models consistently show decreased ice cover in the Ross and Weddell Seas, sectors which in fact have an observed increase in cover. As a first step towards understanding the disagreement between models and observations, modelled sea level pressure trends are analysed using and optimal fingerprinting approach, to identify whether atmospheric deficiencies in the models can explain the model-observation discrepancy. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70044362','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70044362">Climate variability during the Medieval Climate Anomaly and Little Ice Age based on ostracod faunas and shell geochemistry from Biscayne Bay, Florida: Chapter 14</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Cronin, Thomas M.; Wingard, G. Lynn; Dwyer, Gary S.; Swart, Peter K.; Willard, Debra A.; Albietz, Jessica 2012-01-01 An 800-year-long environmental history of Biscayne Bay, Florida, is reconstructed from ostracod faunal and shell geochemical (oxygen, carbon isotopes, Mg/Ca ratios) studies of sediment cores from three mudbanks in the central and southern parts of the bay. Using calibrations derived from analyses of modern Biscayne and Florida Bay ostracods, palaeosalinity oscillations associated with changes in precipitation were identified. These oscillations reflect multidecadal- and centennial-scale climate variability associated with the Atlantic Multidecadal Oscillation during the late Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Evidence suggests wetter regional climate during the MCA and drier conditions during the LIA. In addition, twentieth century anthropogenic modifications to Everglades hydrology influenced bay circulation and/or processes controlling carbon isotopic composition. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PalOc..30..558M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PalOc..30..558M">Holocene multidecadal- to millennial-scale variations in Iceland-Scotland overflow and their relationship to climate</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mjell, Tor Lien; Ninnemann, Ulysses S.; Eldevik, Tor; Kleiven, Helga Kikki F. 2015-05-01 The Nordic Seas overflows are an important part of the Atlantic thermohaline circulation. While there is growing evidence that the overflow of dense water changed on orbital time scales during the Holocene, less is known about the variability on shorter time scales beyond the instrumental record. Here we reconstruct the relative changes in flow strength of Iceland-Scotland Overflow Water (ISOW), the eastern branch of the overflows, on multidecadal-millennial time scales. The reconstruction is based on mean sortable silt (SS>¯) from a sediment core on the Gardar Drift (60°19'N, 23°58'W, 2081 m). Our SS>¯ record reveals that the main variance in ISOW vigor occurred on millennial time scales (1-2 kyr) with particularly prominent fluctuations after 8 kyr. Superimposed on the millennial variability, there were multidecadal-centennial flow speed fluctuations during the early Holocene (10-9 kyr) and one prominent minimum at 0.9 kyr. We find a broad agreement between reconstructed ISOW and regional North Atlantic climate, where a strong (weak) ISOW is generally associated with warm (cold) climate. We further identify the possible contribution of anomalous heat and freshwater forcing, respectively, related to reconstructed overflow variability. We infer that ocean poleward heat transport can explain the relationship between regional climate and ISOW during the middle to late Holocene, whereas freshwater input provides a possible explanation for the reduced overflow during early Holocene (8-10 kyr). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1306152-sensitivity-summer-ensembles-fledgling-superparameterized-mesoscale-convective-systems-cloud-resolving-model-microphysics-grid-configuration','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1306152-sensitivity-summer-ensembles-fledgling-superparameterized-mesoscale-convective-systems-cloud-resolving-model-microphysics-grid-configuration">Sensitivity of summer ensembles of fledgling superparameterized U.S. mesoscale convective systems to cloud resolving model microphysics and grid configuration</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Elliott, Elizabeth J.; Yu, Sungduk; Kooperman, Gabriel J.; ... 2016-05-01 The sensitivities of simulated mesoscale convective systems (MCSs) in the central U.S. to microphysics and grid configuration are evaluated here in a global climate model (GCM) that also permits global-scale feedbacks and variability. Since conventional GCMs do not simulate MCSs, studying their sensitivities in a global framework useful for climate change simulations has not previously been possible. To date, MCS sensitivity experiments have relied on controlled cloud resolving model (CRM) studies with limited domains, which avoid internal variability and neglect feedbacks between local convection and larger-scale dynamics. However, recent work with superparameterized (SP) GCMs has shown that eastward propagating MCS-likemore » events are captured when embedded CRMs replace convective parameterizations. This study uses a SP version of the Community Atmosphere Model version 5 (SP-CAM5) to evaluate MCS sensitivities, applying an objective empirical orthogonal function algorithm to identify MCS-like events, and harmonizing composite storms to account for seasonal and spatial heterogeneity. A five-summer control simulation is used to assess the magnitude of internal and interannual variability relative to 10 sensitivity experiments with varied CRM parameters, including ice fall speed, one-moment and two-moment microphysics, and grid spacing. MCS sensitivities were found to be subtle with respect to internal variability, and indicate that ensembles of over 100 storms may be necessary to detect robust differences in SP-GCMs. Furthermore, these results emphasize that the properties of MCSs can vary widely across individual events, and improving their representation in global simulations with significant internal variability may require comparison to long (multidecadal) time series of observed events rather than single season field campaigns.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3808612','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3808612">Human and natural influences on the changing thermal structure of the atmosphere</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Santer, Benjamin D.; Painter, Jeffrey F.; Bonfils, Céline; Mears, Carl A.; Solomon, Susan; Wigley, Tom M. L.; Gleckler, Peter J.; Schmidt, Gavin A.; Doutriaux, Charles; Gillett, Nathan P.; Taylor, Karl E.; Thorne, Peter W.; Wentz, Frank J. 2013-01-01 Since the late 1970s, satellite-based instruments have monitored global changes in atmospheric temperature. These measurements reveal multidecadal tropospheric warming and stratospheric cooling, punctuated by short-term volcanic signals of reverse sign. Similar long- and short-term temperature signals occur in model simulations driven by human-caused changes in atmospheric composition and natural variations in volcanic aerosols. Most previous comparisons of modeled and observed atmospheric temperature changes have used results from individual models and individual observational records. In contrast, we rely on a large multimodel archive and multiple observational datasets. We show that a human-caused latitude/altitude pattern of atmospheric temperature change can be identified with high statistical confidence in satellite data. Results are robust to current uncertainties in models and observations. Virtually all previous research in this area has attempted to discriminate an anthropogenic signal from internal variability. Here, we present evidence that a human-caused signal can also be identified relative to the larger “total” natural variability arising from sources internal to the climate system, solar irradiance changes, and volcanic forcing. Consistent signal identification occurs because both internal and total natural variability (as simulated by state-of-the-art models) cannot produce sustained global-scale tropospheric warming and stratospheric cooling. Our results provide clear evidence for a discernible human influence on the thermal structure of the atmosphere. PMID:24043789 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48.2635L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48.2635L">Simulated decadal modes of the NH atmospheric circulation arising from intra-decadal variability, external forcing and slow-decadal climate processes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lou, Jiale; Zheng, Xiaogu; Frederiksen, Carsten S.; Liu, Haibo; Grainger, Simon; Ying, Kairan 2017-04-01 A decadal variance decomposition method is applied to the Northern Hemisphere (NH) 500-hPa geopotential height (GPH) and the sea level pressure (SLP) taken from the last millennium (850-1850 AD) experiment with the coupled climate model CCSM4, to estimate the contribution of the intra-decadal variability to the inter-decadal variability. By removing the intra-decadal variability from the total inter-decadal variability, the residual variability is more likely to be associated with slowly varying external forcings and slow-decadal climate processes, and therefore is referred to as slow-decadal variability. The results show that the (multi-)decadal changes of the NH 500-hPa GPH are primarily dominated by slow-decadal variability, whereas the NH SLP field is primarily dominated by the intra-decadal variability. At both pressure levels, the leading intra-decadal modes each have features related to the El Niño-southern oscillation, the intra-decadal variability of the Pacific decadal oscillation (PDO) and the Arctic oscillation (AO); while the leading slow-decadal modes are associated with external radiative forcing (mostly with volcanic aerosol loadings), the Atlantic multi-decadal oscillation and the slow-decadal variability of AO and PDO. Moreover, the radiative forcing has much weaker effect to the SLP than that to the 500-hPa GPH. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GMD.....9.3589Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GMD.....9.3589Z">GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhou, Tianjun; Turner, Andrew G.; Kinter, James L.; Wang, Bin; Qian, Yun; Chen, Xiaolong; Wu, Bo; Wang, Bin; Liu, Bo; Zou, Liwei; He, Bian 2016-10-01 The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the "Grand Challenges" proposed by the World Climate Research Programme. At present, 21 international modeling groups are committed to joining GMMIP. This overview paper introduces the motivation behind GMMIP and the scientific questions it intends to answer. Three tiers of experiments, of decreasing priority, are designed to examine (a) model skill in simulating the climatology and interannual-to-multidecadal variability of global monsoons forced by the sea surface temperature during historical climate period; (b) the roles of the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation in driving variations of the global and regional monsoons; and (c) the effects of large orographic terrain on the establishment of the monsoons. The outputs of the CMIP6 Diagnostic, Evaluation and Characterization of Klima experiments (DECK), "historical" simulation and endorsed MIPs will also be used in the diagnostic analysis of GMMIP to give a comprehensive understanding of the roles played by different external forcings, potential improvements in the simulation of monsoon rainfall at high resolution and reproducibility at decadal timescales. The implementation of GMMIP will improve our understanding of the fundamental physics of changes in the global and regional monsoons over the past 140 years and ultimately benefit monsoons prediction and projection in the current century. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ERL....11l4025B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ERL....11l4025B">Quantifying the increasing sensitivity of power systems to climate variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bloomfield, H. C.; Brayshaw, D. J.; Shaffrey, L. C.; Coker, P. J.; Thornton, H. E. 2016-12-01 Large quantities of weather-dependent renewable energy generation are expected in power systems under climate change mitigation policies, yet little attention has been given to the impact of long term climate variability. By combining state-of-the-art multi-decadal meteorological records with a parsimonious representation of a power system, this study characterises the impact of year-to-year climate variability on multiple aspects of the power system of Great Britain (including coal, gas and nuclear generation), demonstrating why multi-decadal approaches are necessary. All aspects of the example system are impacted by inter-annual climate variability, with the impacts being most pronounced for baseload generation. The impacts of inter-annual climate variability increase in a 2025 wind-power scenario, with a 4-fold increase in the inter-annual range of operating hours for baseload such as nuclear. The impacts on peak load and peaking-plant are comparably small. Less than 10 years of power supply and demand data are shown to be insufficient for providing robust power system planning guidance. This suggests renewable integration studies—widely used in policy, investment and system design—should adopt a more robust approach to climate characterisation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS43C..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS43C..03S">The impact of multi-decadal sub-surface circulation changes on sea surface chlorophyll patterns in the tropical Pacific</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schollaert Uz, S.; Busalacchi, A. J.; Smith, T. M.; Evans, M. N.; Brown, C.; Hackert, E. C.; Wang, X. 2016-12-01 The tropical Pacific is a region of strong forcing where physical oceanography primarily controls biological variability over the seasonal to interannual time scales observed since dedicated ocean color satellite remote sensing began in 1997. To quantify how multi-decadal, climate-scale changes impact marine biological dynamics, we used the correlation with sea-surface temperature and height to reconstruct a 50-year time series of surface chlorophyll concentrations. The reconstruction demonstrates greatest skill away from the coast and within 10o of the equator where chlorophyll variance is greatest and primarily associated with El Niño Southern Oscillation (ENSO) dynamics and secondarily associated with decadal variability. We observe significant basin-wide differences between east and central Pacific events when the El Niño events are strong: chlorophyll increases with La Niña and decreases with El Niño, with larger declines east of 180o for remotely-forced east Pacific events and west of 180o for locally-forced central Pacific events. Chlorophyll variations also reflect the physical dynamics of Pacific decadal variability with small but significant differences between cool and warm eras: consistent with advection variability west of 180o and likely driven by subsurface changes in the nutricline depth between 110-140oW. Comparisons with output from a fully-coupled biogeochemical model support the hypothesis that this anomalous region is controlled by lower frequency changes in subsurface circulation patterns that transport nutrients to the surface. Basin-wide chlorophyll distributions exhibiting spatial heterogeneity in response to multi-decadal climate forcing imply similar long-term changes in phytoplankton productivity, with implications for the marine food web and the ocean's role as a carbon sink. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS51B1664Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS51B1664Z">The Atlantic Multidecadal Variability in surface and deep ocean temperature and salinity fields from unperturbed climate simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zanchettin, D.; Jungclaus, J. H. 2013-12-01 Large multidecadal fluctuations in basin-average sea-surface temperature (SST) are a known feature of observed, reconstructed and simulated variability in the North Atlantic Ocean. This phenomenon is often referred to as Multidecadal Atlantic Variability or AMV. Historical AMV fluctuations are associated with analog basin-scale changes in sea-surface salinity, so that warming corresponds to salinification and cooling to freshening [Polyakov et al., 2005]. The surface imprint of the AMV further corresponds to same-sign fluctuations in the shallow ocean and with opposite-sign fluctuations in the deep ocean for both temperature and salinity [Polyakov et al., 2005]. This out-of-phase behavior reflects the thermohaline overturning circulation shaping North Atlantic's low-frequency variability. Several processes contribute to the AMV, involving both ocean-atmosphere coupled processes and deep ocean circulation [e.g., Grossmann and Klotzbach, 2009]. In particular, recirculation in the North Atlantic subpolar gyre region of salinity anomalies from Arctic freshwater export may trigger multidecadal variability in the Atlantic meridional overturning circulation, and therefore may be part of the AMV [Jungclaus et al., 2005; Dima and Lohmann, 2007]. With this contribution, we aim to improve the physical interpretation of the AMV by investigating spatial and temporal patterns of temperature and salinity fields in the shallow and deep ocean. We focus on two unperturbed millennial-scale simulations performed with the Max Planck Institute Earth system model in its paleo (MPI-ESM-P) and low-resolution (MPI-ESM-LR) configurations, which provide reference control climates for assessments of pre-industrial and historical climate simulations. The two model configurations only differ for the presence, in MPI-ESM-LR, of an active module for dynamical vegetation. We use spatial-average indices and empirical orthogonal functions/principal components to track the horizontal and vertical propagation of temperature and salinity anomalies related to the AMV. In particular, we discuss the potential predictability of multidecadal fluctuations in North Atlantic SSTs based on indices derived from the sea-surface salinity field. We show how the two simulations provide AMV realizations with some distinguishable characteristics, e.g., the typical fluctuations' frequencies and the linkage with the North Atlantic meridional overturning and gyre circulations. We further show how information gained by investigating different definitions of the AMV [Zanchettin et al., 2013] helps designing numerical sensitivity studies for understanding the mechanism(s) behind this phenomenon, concerning both its origin and global impacts. References Dima, M., and G. Lohmann [2007], J. Clim., 20, 2706-2719, doi:10.1175/JCLI4174.1 Jungclaus, J.H., et al. [2005], J. Clim., 18, 4013- 4031, doi:10.1175/JCLI3462.1 Polyakov, I. V., et al. [2005], J. Clim., 18:4562-4581 Grossmann, I., and P. J. Klotzbach [2009], J. Geophys. Res., 114, D24107, doi:10.1029/2009JD012728 Zanchettin D., et al. [2013], Clim. Dyn., doi:10.1007/s00382-013-1669-0 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120016294','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120016294">Multi-Decadal Change of Atmospheric Aerosols and Their Effect on Surface Radiation</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Chin, Mian; Diehl, Thomas; Tan, Qian; Wild, Martin; Qian, Yun; Yu, Hongbin; Bian, Huisheng; Wang, Weiguo 2012-01-01 We present an investigation on multi-decadal changes of atmospheric aerosols and their effects on surface radiation using a global chemistry transport model along with the near-term to long-term data records. We focus on a 28-year time period of satellite era from 1980 to 2007, during which a suite of aerosol data from satellite observations and ground-based remote sensing and in-situ measurements have become available. We analyze the long-term global and regional aerosol optical depth and concentration trends and their relationship to the changes of emissions" and assess the role aerosols play in the multi-decadal change of solar radiation reaching the surface (known as "dimming" or "brightening") at different regions of the world, including the major anthropogenic source regions (North America, Europe, Asia) that have been experiencing considerable changes of emissions, dust and biomass burning regions that have large interannual variabilities, downwind regions that are directly affected by the changes in the source area, and remote regions that are considered to representing "background" conditions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160008717&hterms=spices&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dspices','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160008717&hterms=spices&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dspices">Warming of the Global Ocean: Spatial Structure and Water-Mass Trends</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L. 2016-01-01 This study investigates the multidecadal warming and interannual-to-decadal heat content changes in the upper ocean (0-700 m), focusing on vertical and horizontal patterns of variability. These results support a nearly monotonic warming over much of the World Ocean, with a shift toward Southern Hemisphere warming during the well-observed past decade. This is based on objectively analyzed gridded observational datasets and on a modeled state estimate. Besides the surface warming, a warming climate also has a subsurface effect manifesting as a strong deepening of the midthermocline isopycnals, which can be diagnosed directly from hydrographic data. This deepening appears to be a result of heat entering via subduction and spreading laterally from the high-latitude ventilation regions of subtropical mode waters. The basin-average multidecadal warming mainly expands the subtropical mode water volume, with weak changes in the temperature-salinity (u-S) relationship (known as ''spice'' variability). However, the spice contribution to the heat content can be locally large, for example in Southern Hemisphere. Multidecadal isopycnal sinking has been strongest over the southern basins and weaker elsewhere with the exception of the Gulf Stream/North Atlantic Current/subtropical recirculation gyre. At interannual to decadal time scales, wind-driven sinking and shoaling of density surfaces still dominate ocean heat content changes, while the contribution from temperature changes along density surfaces tends to decrease as time scales shorten. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27787628','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27787628">ENSO and PDO-related climate variability impacts on Midwestern United States crop yields.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Henson, Chasity; Market, Patrick; Lupo, Anthony; Guinan, Patrick 2017-05-01 An analysis of crop yields for the state of Missouri was completed to determine if an interannual or multidecadal variability existed as a result of the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Corn and soybean yields were recorded in kilograms per hectare for each of the six climate regions of Missouri. An analysis using the Mokhov "method of cycles" demonstrated interannual, interdecadal, and multidecadal variations in crop yields. Cross-spectral analysis was used to determine which region was most impacted by ENSO and PDO influenced seasonal (April-September) temperature and precipitation. Interannual (multidecadal) variations found in the spectral analysis represent a relationship to ENSO (PDO) phase, while interdecadal variations represent a possible interaction between ENSO and PDO. Average crop yields were then calculated for each combination of ENSO and PDO phase, displaying a pronounced increase in corn and soybean yields when ENSO is warm and PDO is positive. Climate regions 1, 2, 4, and 6 displayed significant differences (p value of 0.10 or less) in yields between El Niño and La Niña years, representing 55-70 % of Missouri soybean and corn productivity, respectively. Final results give the opportunity to produce seasonal predictions of corn and soybean yields, specific to each climate region in Missouri, based on the combination of ENSO and PDO phases. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150002680','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150002680">On the Origin of Multidecadal to Centennial Greenland Temperature Anomalies Over the Past 800 yr</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kobashi, T.; Shindell, D. T.; Kodera, K.; Box, J. E.; Nakaegawa, T.; Kawamura, K. 2013-01-01 The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH]) over the past 800 yr by subtracting the standardized northern hemispheric (NH) temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH); polar amplification; and regional variability (GTA[G-NH]). The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The GTA[G-NH] explains 31-35%of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and associated changes in northward oceanic heat transport. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CliPa...9..583K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CliPa...9..583K">On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kobashi, T.; Shindell, D. T.; Kodera, K.; Box, J. E.; Nakaegawa, T.; Kawamura, K. 2013-03-01 The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH]) over the past 800 yr by subtracting the standardized northern hemispheric (NH) temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH); polar amplification; and regional variability (GTA[G-NH]). The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The GTA[G-NH] explains 31-35% of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and associated changes in northward oceanic heat transport. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPC21A..06O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPC21A..06O">Wintertime atmospheric response to decadal SST anomalies in the North Pacific frontal zone and its relationship to dominant atmospheric internal variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Okajima, S.; Nakamura, H.; Nishii, K.; Miyasaka, T.; Kuwano-Yoshida, A.; Taguchi, B. 2016-02-01 A decadal-scale warm SST anomaly observed in the North Pacific subarctic frontal zone (SAFZ) tends to accompany a basin-scale anticyclonic anomaly in the troposphere that peaks in January. A set of sensitivity experiments conducted with an AGCM simulates an anticyclonic ensemble response over the North Pacific in January. As observed, the simulated anticyclonic response is in equivalent barotropic structure and maintained mainly through energy conversion from the ensemble mean circulation realized under the climatological SST, suggesting that the anomaly may have a characteristic of a dynamical mode. Conversion of both available potential energy (APE) and kinetic energy (KE) from the mean flow is important for the observed anomaly, while only the former is important for the model response. This is because the model response is located to the north of the jet core region whereas the observed anomaly is straddling the jet exit region, which appears to be in correspondence to the northwestward displacement of the center of the dominant atmospheric internal variability in our model relative to the observed center. Transient eddy feedback forcing also acts to maintain the observed anomaly rather efficiently, while its efficiency is much lower for the simulated response, which seems to be consistent with the poleward displacement of the anticyclonic response from the jet and stormtrack axes. A multi-decadal integration of our coupled GCM also suggests that atmospheric internal variability may be important for determining atmospheric response to the decadal SST variability of the SAFZ. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://wwwpaztcn.wr.usgs.gov/julio_pdf/Gray_Ecol_ea.pdf','USGSPUBS'); return false;" href="http://wwwpaztcn.wr.usgs.gov/julio_pdf/Gray_Ecol_ea.pdf">Role of multidecadal climate variability in a range extension of pinyon pine</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Gray, Stephen T.; Betancourt, Julio L.; Jackson, Stephen T.; Eddy, Robert G. 2006-01-01 Evidence from woodrat middens and tree rings at Dutch John Mountain (DJM) in northeastern Utah reveal spatiotemporal patterns of pinyon pine (Pinus edulis Engelm.) colonization and expansion in the past millennium. The DJM population, a northern outpost of pinyon, was established by long-distance dispersal (~40 km). Growth of this isolate was markedly episodic and tracked multidecadal variability in precipitation. Initial colonization occurred by AD 1246, but expansion was forestalled by catastrophic drought (1250–1288), which we speculate produced extensive mortality of Utah Juniper (Juniperus osteosperma (Torr.) Little), the dominant tree at DJM for the previous ~8700 years. Pinyon then quickly replaced juniper across DJM during a few wet decades (1330–1339 and 1368–1377). Such alternating decadal-scale droughts and pluvial events play a key role in structuring plant communities at the landscape to regional level. These decadal-length precipitation anomalies tend to be regionally coherent and can synchronize physical and biological processes across large areas. Vegetation forecast models must incorporate these temporal and geographic aspects of climate variability to accurately predict the effects of future climate change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/biblio/1340887-gmmip-v1-contribution-cmip6-global-monsoons-model-inter-comparison-project','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1340887-gmmip-v1-contribution-cmip6-global-monsoons-model-inter-comparison-project">GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Zhou, Tianjun; Turner, Andrew G.; Kinter, James L. The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the “Grand Challenges” proposed by the World Climate Research Programme. At present, 21 international modeling groups are committed to joining GMMIP. This overview paper introduces the motivation behind GMMIP and the scientific questions it intends to answer. Three tiers of experiments, of decreasing priority, are designed to examinemore » (a) model skill in simulating the climatology and interannual-to-multidecadal variability of global monsoons forced by the sea surface temperature during historical climate period; (b) the roles of the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation in driving variations of the global and regional monsoons; and (c) the effects of large orographic terrain on the establishment of the monsoons. The outputs of the CMIP6 Diagnostic, Evaluation and Characterization of Klima experiments (DECK), “historical” simulation and endorsed MIPs will also be used in the diagnostic analysis of GMMIP to give a comprehensive understanding of the roles played by different external forcings, potential improvements in the simulation of monsoon rainfall at high resolution and reproducibility at decadal timescales. The implementation of GMMIP will improve our understanding of the fundamental physics of changes in the global and regional monsoons over the past 140 years and ultimately benefit monsoons prediction and projection in the current century.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoRL..3921705A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoRL..3921705A">The amplitude of decadal to multidecadal variability in precipitation simulated by state-of-the-art climate models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ault, T. R.; Cole, J. E.; St. George, S. 2012-11-01 We assess the magnitude of decadal to multidecadal (D2M) variability in Climate Model Intercomparison Project 5 (CMIP5) simulations that will be used to understand, and plan for, climate change as part of the Intergovernmental Panel on Climate Change's 5th Assessment Report. Model performance on D2M timescales is evaluated using metrics designed to characterize the relative and absolute magnitude of variability at these frequencies. In observational data, we find that between 10% and 35% of the total variance occurs on D2M timescales. Regions characterized by the high end of this range include Africa, Australia, western North America, and the Amazon region of South America. In these areas D2M fluctuations are especially prominent and linked to prolonged drought. D2M fluctuations account for considerably less of the total variance (between 5% and 15%) in the CMIP5 archive of historical (1850-2005) simulations. The discrepancy between observation and model based estimates of D2M prominence reflects two features of the CMIP5 archive. First, interannual components of variability are generally too energetic. Second, decadal components are too weak in several key regions. Our findings imply that projections of the future lack sufficient decadal variability, presenting a limited view of prolonged drought and pluvial risk. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JHyd..556..835V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JHyd..556..835V">A conditional stochastic weather generator for seasonal to multi-decadal simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Verdin, Andrew; Rajagopalan, Balaji; Kleiber, William; Podestá, Guillermo; Bert, Federico 2018-01-01 We present the application of a parametric stochastic weather generator within a nonstationary context, enabling simulations of weather sequences conditioned on interannual and multi-decadal trends. The generalized linear model framework of the weather generator allows any number of covariates to be included, such as large-scale climate indices, local climate information, seasonal precipitation and temperature, among others. Here we focus on the Salado A basin of the Argentine Pampas as a case study, but the methodology is portable to any region. We include domain-averaged (e.g., areal) seasonal total precipitation and mean maximum and minimum temperatures as covariates for conditional simulation. Areal covariates are motivated by a principal component analysis that indicates the seasonal spatial average is the dominant mode of variability across the domain. We find this modification to be effective in capturing the nonstationarity prevalent in interseasonal precipitation and temperature data. We further illustrate the ability of this weather generator to act as a spatiotemporal downscaler of seasonal forecasts and multidecadal projections, both of which are generally of coarse resolution. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7678M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7678M">Antarctic warming driven by internal Southern Ocean deep convection oscillations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Martin, Torge; Pedro, Joel B.; Steig, Eric J.; Jochum, Markus; Park, Wonsun; Rasmussen, Sune O. 2016-04-01 Simulations with the free-running, complex coupled Kiel Climate Model (KCM) show that heat release associated with recurring Southern Ocean deep convection can drive centennial-scale Antarctic temperature variations of 0.5-2.0 °C. We propose a mechanism connecting the intrinsic ocean variability with Antarctic warming that involves the following three steps: Preconditioning: heat supplied by the lower branch of the Atlantic Meridional Overturning Circulation (AMOC) accumulates at depth in the Southern Ocean, trapped by the Weddell Gyre circulation; Convection onset: wind and/or sea-ice changes tip the preconditioned, thermally unstable system into the convective state; Antarctic warming: fast sea-ice-albedo feedbacks (on annual to decadal timescales) and slower Southern Ocean frontal and sea-surface temperature adjustments to the convective heat release (on multi-decadal to centennial timescales), drive an increase in atmospheric heat and moisture transport towards Antarctica resulting in warming over the continent. Further, we discuss the potential role of this mechanism to explain climate variability observed in Antarctic ice-core records. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMPP33B1574E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMPP33B1574E">Multi-Decadal to Millennial Scale Holocene Hydrologic Variation in the Southern Hemisphere Tropics of South America</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ekdahl, E. J.; Fritz, S. C.; Baker, P. A.; Burns, S. J.; Coley, K.; Rigsby, C. A. 2005-12-01 Numerous sites in the Northern Hemisphere show multi-decadal to millennial scale climate variation during the Holocene, many of which have been correlated with changes in atmospheric radiocarbon production or with changes in North Atlantic oceanic circulation. The manifestation of such climate variability in the hydrology of the Southern Hemisphere tropics of South America is unclear, because of the limited number of records at suitably high resolution. In the Lake Titicaca drainage basin of Bolivia and Peru, high-resolution lacustrine records reveal the overall pattern of Holocene lake-level change, the influence of precessional forcing of the South American Summer Monsoon, and the effects of high-frequency climate variability in records of lake productivity and lake ecology. Precessional forcing of regional precipitation is evident in the Lake Titicaca basin as a massive (ca. 85 m) mid-Holocene decline in lake level beginning about 7800 cal yr BP and a subsequent rise in lake level after 4000 cal yr BP. Here we show that multi-decadal to millennial-scale climate variability, superimposed upon the envelope of change at orbital time scales, is similar in timing and pattern to the ice-rafted debris record of Holocene Bond events in the North Atlantic. A high-resolution carbon isotopic record from Lake Titicaca that spans the entire Holocene suggests that cold intervals of Holocene Bond events are periods of increased precipitation, thus indicating an anti-phasing of precipitation variation on the Altiplano relative to the Northern Hemisphere tropics. A similar pattern of variation is also evident in high-resolution (2-30 yr spacing) diatom and geochemical records that span the last 7000 yr from two smaller lakes, Lagos Umayo and Lagunillas, in the Lake Titicaca drainage basin. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1137K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1137K">Canadian snow and sea ice: assessment of snow, sea ice, and related climate processes in Canada's Earth system model and climate-prediction system</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kushner, Paul J.; Mudryk, Lawrence R.; Merryfield, William; Ambadan, Jaison T.; Berg, Aaron; Bichet, Adéline; Brown, Ross; Derksen, Chris; Déry, Stephen J.; Dirkson, Arlan; Flato, Greg; Fletcher, Christopher G.; Fyfe, John C.; Gillett, Nathan; Haas, Christian; Howell, Stephen; Laliberté, Frédéric; McCusker, Kelly; Sigmond, Michael; Sospedra-Alfonso, Reinel; Tandon, Neil F.; Thackeray, Chad; Tremblay, Bruno; Zwiers, Francis W. 2018-04-01 The Canadian Sea Ice and Snow Evolution (CanSISE) Network is a climate research network focused on developing and applying state-of-the-art observational data to advance dynamical prediction, projections, and understanding of seasonal snow cover and sea ice in Canada and the circumpolar Arctic. This study presents an assessment from the CanSISE Network of the ability of the second-generation Canadian Earth System Model (CanESM2) and the Canadian Seasonal to Interannual Prediction System (CanSIPS) to simulate and predict snow and sea ice from seasonal to multi-decadal timescales, with a focus on the Canadian sector. To account for observational uncertainty, model structural uncertainty, and internal climate variability, the analysis uses multi-source observations, multiple Earth system models (ESMs) in Phase 5 of the Coupled Model Intercomparison Project (CMIP5), and large initial-condition ensembles of CanESM2 and other models. It is found that the ability of the CanESM2 simulation to capture snow-related climate parameters, such as cold-region surface temperature and precipitation, lies within the range of currently available international models. Accounting for the considerable disagreement among satellite-era observational datasets on the distribution of snow water equivalent, CanESM2 has too much springtime snow mass over Canada, reflecting a broader northern hemispheric positive bias. Biases in seasonal snow cover extent are generally less pronounced. CanESM2 also exhibits retreat of springtime snow generally greater than observational estimates, after accounting for observational uncertainty and internal variability. Sea ice is biased low in the Canadian Arctic, which makes it difficult to assess the realism of long-term sea ice trends there. The strengths and weaknesses of the modelling system need to be understood as a practical tradeoff: the Canadian models are relatively inexpensive computationally because of their moderate resolution, thus enabling their use in operational seasonal prediction and for generating large ensembles of multidecadal simulations. Improvements in climate-prediction systems like CanSIPS rely not just on simulation quality but also on using novel observational constraints and the ready transfer of research to an operational setting. Improvements in seasonal forecasting practice arising from recent research include accurate initialization of snow and frozen soil, accounting for observational uncertainty in forecast verification, and sea ice thickness initialization using statistical predictors available in real time. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1280976','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1280976">Initialized decadal prediction for transition to positive phase of the Interdecadal Pacific Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Meehl, Gerald A.; Hu, Aixue; Teng, Haiyan The negative phase of the Interdecadal Pacific Oscillation (IPO), a dominant mode of multi-decadal variability of sea surface temperatures (SSTs) in the Pacific, contributed to the reduced rate of global surface temperature warming in the early 2000s. Here, a proposed mechanism for IPO multidecadal variability indicates that the presence of decadal timescale upper ocean heat content in the off-equatorial western tropical Pacific can provide conditions for an interannual El Nino/Southern Oscillation event to trigger a transition of tropical Pacific SSTs to the opposite IPO phase. Here we show that a decadal prediction initialized in 2013 simulates predicted Nino3.4 SSTs thatmore » have qualitatively tracked the observations through 2015. The year three to seven average prediction (2015-2019) from the 2013 initial state shows a transition to the positive phase of the IPO from the previous negative phase and a resumption of larger rates of global warming over the 2013-2022 period consistent with a positive IPO phase.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.7865Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.7865Z">On the persistence and coherence of subpolar sea surface temperature and salinity anomalies associated with the Atlantic multidecadal variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, Rong 2017-08-01 This study identifies key features associated with the Atlantic multidecadal variability (AMV) in both observations and a fully coupled climate model, e.g., decadal persistence of monthly mean subpolar North Atlantic (NA) sea surface temperature (SST) and salinity (SSS) anomalies, and high coherence at low frequency among subpolar NA SST/SSS, upper ocean heat/salt content, and the Atlantic Meridional Overturning Circulation (AMOC) fingerprint. These key AMV features, which can be used to distinguish the AMV mechanism, cannot be explained by the slab ocean model results or the red noise process but are consistent with the ocean dynamics mechanism. This study also shows that at low frequency, the correlation and regression between net surface heat flux and SST anomalies are key indicators of the relative roles of oceanic versus atmospheric forcing in SST anomalies. The oceanic forcing plays a dominant role in the subpolar NA SST anomalies associated with the AMV. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010886','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010886">Stationarity of the Tropical Pacific Teleconnection to North America in CMIP5 PMIP3 Model Simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Coats, Sloan; Smerdon, Jason E.; Cook, Benjamin I.; Seager, Richard 2013-01-01 The temporal stationarity of the teleconnection between the tropical Pacific Ocean and North America (NA) is analyzed in atmosphere-only, and coupled last-millennium, historical, and control runs from the Coupled Model Intercomparison Project Phase 5 data archive. The teleconnection, defined as the correlation between December-January-February (DJF) tropical Pacific sea surface temperatures (SSTs) and DJF 200 mb geopotential height, is found to be nonstationary on multidecadal timescales. There are significant changes in the spatial features of the teleconnection over NA in continuous 56-year segments of the last millennium and control simulations. Analysis of atmosphere-only simulations forced with observed SSTs indicates that atmospheric noise cannot account for the temporal variability of the teleconnection, which instead is likely explained by the strength of, and multidecadal changes in, tropical Pacific Ocean variability. These results have implications for teleconnection-based analyses of model fidelity in simulating precipitation, as well as any reconstruction and forecasting efforts that assume stationarity of the observed teleconnection. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4412527S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4412527S">Strong Dependence of U.S. Summertime Air Quality on the Decadal Variability of Atlantic Sea Surface Temperatures</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shen, Lu; Mickley, Loretta J.; Leibensperger, Eric M.; Li, Mingwei 2017-12-01 We find that summertime air quality in the eastern U.S. displays strong dependence on North Atlantic sea surface temperatures, resulting from large-scale ocean-atmosphere interactions. Using observations, reanalysis data sets, and climate model simulations, we further identify a multidecadal variability in surface air quality driven by the Atlantic Multidecadal Oscillation (AMO). In one-half cycle ( 35 years) of the AMO from cold to warm phase, summertime maximum daily 8 h ozone concentrations increase by 1-4 ppbv and PM2.5 concentrations increase by 0.3-1.0 μg m-3 over much of the east. These air quality changes are related to warmer, drier, and more stagnant weather in the AMO warm phase, together with anomalous circulation patterns at the surface and aloft. If the AMO shifts to the cold phase in future years, it could partly offset the climate penalty on U.S. air quality brought by global warming, an effect which should be considered in long-term air quality planning. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoRL..37.8703C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoRL..37.8703C">Twentieth century bipolar seesaw of the Arctic and Antarctic surface air temperatures</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chylek, Petr; Folland, Chris K.; Lesins, Glen; Dubey, Manvendra K. 2010-04-01 Understanding the phase relationship between climate changes in the Arctic and Antarctic regions is essential for our understanding of the dynamics of the Earth's climate system. In this paper we show that the 20th century de-trended Arctic and Antarctic temperatures vary in anti-phase seesaw pattern - when the Arctic warms the Antarctica cools and visa versa. This is the first time that a bi-polar seesaw pattern has been identified in the 20th century Arctic and Antarctic temperature records. The Arctic (Antarctic) de-trended temperatures are highly correlated (anti-correlated) with the Atlantic Multi-decadal Oscillation (AMO) index suggesting the Atlantic Ocean as a possible link between the climate variability of the Arctic and Antarctic regions. Recent accelerated warming of the Arctic results from a positive reinforcement of the linear warming trend (due to an increasing concentration of greenhouse gases and other possible forcings) by the warming phase of the multidecadal climate variability (due to fluctuations of the Atlantic Ocean circulation). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1280976-initialized-decadal-prediction-transition-positive-phase-interdecadal-pacific-oscillation','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1280976-initialized-decadal-prediction-transition-positive-phase-interdecadal-pacific-oscillation">Initialized decadal prediction for transition to positive phase of the Interdecadal Pacific Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Meehl, Gerald A.; Hu, Aixue; Teng, Haiyan 2016-06-02 The negative phase of the Interdecadal Pacific Oscillation (IPO), a dominant mode of multi-decadal variability of sea surface temperatures (SSTs) in the Pacific, contributed to the reduced rate of global surface temperature warming in the early 2000s. Here, a proposed mechanism for IPO multidecadal variability indicates that the presence of decadal timescale upper ocean heat content in the off-equatorial western tropical Pacific can provide conditions for an interannual El Nino/Southern Oscillation event to trigger a transition of tropical Pacific SSTs to the opposite IPO phase. Here we show that a decadal prediction initialized in 2013 simulates predicted Nino3.4 SSTs thatmore » have qualitatively tracked the observations through 2015. The year three to seven average prediction (2015-2019) from the 2013 initial state shows a transition to the positive phase of the IPO from the previous negative phase and a resumption of larger rates of global warming over the 2013-2022 period consistent with a positive IPO phase.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813442D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813442D">Impacts of climate change and internal climate variability on french rivers streamflows</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dayon, Gildas; Boé, Julien; Martin, Eric 2016-04-01 The assessment of the impacts of climate change often requires to set up long chains of modeling, from the model to estimate the future concentration of greenhouse gases to the impact model. Throughout the modeling chain, sources of uncertainty accumulate making the exploitation of results for the development of adaptation strategies difficult. It is proposed here to assess the impacts of climate change on the hydrological cycle over France and the associated uncertainties. The contribution of the uncertainties from greenhouse gases emission scenario, climate models and internal variability are addressed in this work. To have a large ensemble of climate simulations, the study is based on Global Climate Models (GCM) simulations from the Coupled Model Intercomparison Phase 5 (CMIP5), including several simulations from the same GCM to properly assess uncertainties from internal climate variability. Simulations from the four Radiative Concentration Pathway (RCP) are downscaled with a statistical method developed in a previous study (Dayon et al. 2015). The hydrological system Isba-Modcou is then driven by the downscaling results on a 8 km grid over France. Isba is a land surface model that calculates the energy and water balance and Modcou a hydrogeological model that routes the surface runoff given by Isba. Based on that framework, uncertainties uncertainties from greenhouse gases emission scenario, climate models and climate internal variability are evaluated. Their relative importance is described for the next decades and the end of this century. In a last part, uncertainties due to internal climate variability on streamflows simulated with downscaled GCM and Isba-Modcou are evaluated against observations and hydrological reconstructions on the whole 20th century. Hydrological reconstructions are based on the downscaling of recent atmospheric reanalyses of the 20th century and observations of temperature and precipitation. We show that the multi-decadal variability of streamflows observed in the 20th century is generally weaker in the hydrological simulations done with the historical simulations from climate models. References: Dayon et al. (2015), Transferability in the future climate of a statistical downscaling mehtod for precipitation in France, J. Geophys. Res. Atmos., 120, 1023-1043, doi:10.1002/2014JD022236 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....1505D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....1505D">300 Years of East African Climate Variability from Oxygen Isotopes in a Kenya Coral</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dunbar, R. 2003-04-01 Instrumental records of climate variability from the western Indian Ocean are relatively scarce and short. Here I present a monthly resolution stable isotopic record acquired from a large living coral head (Porites) from the Malindi Marine Reserve, Kenya (3^oS, 40^oE). The annual chronology is precise and is based on exceptionally clear high and low density growth band couplets. The record extends from 1696 to 1996 A.D., making it the longest coral climate record from the Indian Ocean and one of the longest available worldwide. We have analyzed the uppermost portion of the coral colony in triplicate, using 3 separate cores. This upper section, used for calibration purposes, also provides estimates of signal fidelity and noise in the climate recording system internal to the colony. Coral δ18O at this site primarily records SST; linear regression of monthly coral δ18O vs. SST yields a slope of -0.26 ppm δ18O per ^oC, and δ18O explains ˜57% of the SST variance. Additional isotopic variability may result from changes in seawater δ18O due to local runoff or regional evaporation/precipitation balance, but these changes are likely to be small because local rainfall δ18O is not strongly depleted relative to seawater and salinity gradients are small. The coral record indicates a clear warming trend of about 1.5^oC that accelerates in the latest 20th century, superimposed on strong decadal variability that persists throughout the record. In fact, δ18O values in the 1990's exceed the 300 year envelope (they are lower) and correspond with apparently unprecedented coral bleaching in coastal East Africa. The decadal component of the Malindi coral record reflects a regional climate signal spanning much of the western equatorial Indian Ocean. In general, East African SST and rainfall are better correlated with Pacific ENSO indicators than with the Indian Monsoon at all periods (inter-annual through multi-decadal) but the correlation weakens after 1975. One dramatic new result we report here is a strong indication of a major cool and dry period from 1750--1820 A.D. This is the single largest multi-decadal anomaly of the past 300 years and correlates perfectly in time with the historically and anecdotally defined Lapanarat Drought. Our results indicate a strong link between multi-decadal tropical cold SST anomalies And far-reaching continental droughts in East Africa. Causes and links to other climate recording systems will be explored. Interannual-decadal SST variations are strongly coherent with ENSO indices and other ENSO-sensitive coral records on decadal and interannual time scales. The decadal component of the Malindi coral record reflects a regional climate signal spanning much of the western equatorial Indian Ocean. Previous work has argued that this component likely reflects a monsoonal influence. However, decadal variance in both Malindi and Seychelles (Charles et al. 1997) coral records is more strongly coherent with ENSO indices than with the India or East Africa rain indices. The coherency of both coral records with Pacific indicators suggests instead that Indian Ocean variability reflects decadal ENSO-like variability originating in the Pacific. These records don't correlate significantly with the Pacific Decadal Oscillation implying a dominant role for the tropical Pacific (as opposed to extra-tropical regions) as a source of regional decadal variability in the western Indian Ocean. This work confirms that the tropical Pacific can act as an agent of decadal climate variability over a very large spatial scale. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A14F..02G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A14F..02G">The role of historical forcings in simulating the observed Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Goes, L. M.; Cane, M. A.; Bellomo, K.; Clement, A. C. 2016-12-01 The variation in basin-wide North Atlantic sea surface temperatures (SST), known as the Atlantic multidecadal oscillation (AMO), affects climate throughout the Northern Hemisphere and tropics, yet the forcing mechanisms are not fully understood. Here, we analyze the AMO in the Coupled Model Intercomparison Project phase 5 (CMIP5) Pre-industrial (PI) and Historical (HIST) simulations to determine the role of historical climate forcings in producing the observed 20th century shifts in the AMO (OBS, 1865-2005). We evaluate whether the agreement between models and observations is better with historical forcings or without forcing - i.e. due to processes internal to the climate system, such as the Atlantic Meridional Overturning Circulation (AMOC). To do this we draw 141-year samples from 38 CMIP5 PI runs and compare the correlation between the PI and HIST AMO to the observed AMO. We find that in the majority of models (24 out of 38), it is very unlikely (less than 10% chance) that the unforced simulations produce agreement with observations that are as high as the forced simulations. We also compare the amplitude of the simulated AMO and find that 87% of models produce multi-decadal variance in the AMO with historical forcings that is very likely higher than without forcing, but most models underestimate the variance of the observed AMO. This indicates that over the 20th century external rather than internal forcing was crucial in setting the pace, phase and amplitude of the AMO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70024590','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70024590">A 1500-year record of climatic and environmental change in Elk Lake, Minnesota I: Varve thickness and gray-scale density</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Dean, W.; Anderson, R.; Platt, Bradbury J.; Anderson, D. 2002-01-01 The deepest part (29.5 m) of Elk Lake, Clearwater County, northwestern Minnesota, contains a complete Holocene section that is continuously varved. The varve components are predominantly autochthonous (CaCO3, organic matter, biogenic silica, and several iron and manganese minerals), but the varves do contain a minor detrital-clastic (aluminosilicate) component that is predominantly wind-borne (eolian) and provides an important record of atmospheric conditions. Singular spectrum analysis (SSA) and wavelet analysis of varve thickness recognized significant periodicities in the multicentennial and multidecadal bands that varied in power (i.e., variable significance) and position (i.e., variable period) within the periodic bands. Persistent periodicities of about 10, 22, 40, and 90 years, and, in particular, multicentennial periodicities in varve thickness and other proxy variables are similar to those in spectra of radiocarbon production, a proxy for past solar activity. This suggests that there may be a solar control, perhaps through geomagnetic effects on atmospheric circulation. Multicentennial and multidecadal periodicities also occur in wavelet spectra of relative gray-scale density. However, gray-scale density does not appear to correlate with any of the measured proxy variables, and at this point we do not know what controlled gray scale. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140008676','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140008676">Reply to Comment by Laprise on 'the Added Value to Global Model Projections of Climate Change by Dynamical Downscaling: a Case Study over the Continental U.S. Using the GISS-ModelE2 and WRF Models'</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Shindell, Drew Todd; Racherla, Pavan; Milly, George Peter 2014-01-01 In his comment, Laprise raises several points that we agree merit consideration. His primary critique is that our study [Racherla et al., 2012] tested the ability of the WRF regional climate model to reproduce historical temperature and precipitation change relative to the driving global climate model (GCM) using only a single simulation rather than an ensemble. He asserts that the observed changes are smaller than the internal variability in the climate system (i.e., not statistically significant) and that thus a single simulation should not necessarily be able to capture the observations. Laprise points out that the statistical signal is reduced for a multi-decadal trend such as the one we analyzed in comparison with mean climatology and cites two studies showing that for particular climate parameters it can take any years for a signal to be discerned over internal variability. He states that The results of theexperiment as designed were strongly influenced by the presence of internal variability and sampling errors,which masked the rather small climate changes that may have occurred as a consequence of changes inforcing during the period considered. While Laprise discusses statistics in general terms at some length, for the actual climate trends examined in our study, he offers no evidence that the forced signal was smallcompared with internal variability. The two studies he cites [de Ela et al., 2013; Maraun, 2013] do not provide convincing evidence as they concern climate variables averaged over different times and areas. One in fact examines extreme precipitation events, which by definition are rare and thus have a lower significance level. We accept the general point that it is important to consider internal variability, and as noted in our paper we agree that an ensemble of simulations is in principle an optimal, though computationally expensive, approach. While we did not present the statistical significance of the observations in our original paper, we have now evaluated those for the regional temperature trends used in our study to evaluate the added value of WRF and thus can analyze data as to the magnitude of the trends with respect to internal variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70184320','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70184320">Teleconnected ocean forcing of Western North American droughts and pluvials during the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Routson, Cody C.; Woodhouse, Connie A.; Overpeck, Jonathan T.; Betancourt, Julio L.; McKay, Nicholas P. 2016-01-01 Western North America (WNA) is rich in hydroclimate reconstructions, yet questions remain about the causes of decadal-to-multidecadal hydroclimate variability. Teleconnection patterns preserved in annually-resolved tree-ring reconstructed drought maps, and anomalies in a global network of proxy sea surface temperature (SST) reconstructions, were used to reassess the evidence linking ocean forcing to WNA hydroclimate variability over the past millennium. Potential forcing mechanisms of the Medieval Climate Anomaly (MCA) and individual drought and pluvial events—including two multidecadal-length MCA pluvials—were evaluated. We show strong teleconnection patterns occurred during the driest (wettest) years within persistent droughts (pluvials), implicating SSTs as a potent hydroclimate forcing mechanism. The role of the SSTs on longer timescales is more complex. Pacific teleconnection patterns show little long-term change, whereas low-resolution SST reconstructions vary over decades to centuries. While weaker than the tropical Pacific teleconnections, North Atlantic teleconnection patterns and SST reconstructions also show links to WNA droughts and pluvials, and may in part account for longer-term WNA hydroclimate changes. Nonetheless, evidence linking WNA hydroclimate to SSTs still remains sparse and nuanced—especially over long-timescales with a broader range of hydroclimatic variability than characterized during the 20th century. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009088','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009088">Coherent Multidecadal Atmospheric and Oceanic Variability in the North Atlantic: Blocking Corresponds with Warm Subpolar Ocean</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hakkinen, Sirpa M.; Rhines, P. B.; Worthen, D. L. 2012-01-01 Winters with frequent atmospheric blocking, in a band of latitudes from Greenland to Western Europe, are found to persist over several decades and correspond to a warm North Atlantic Ocean. This is evident in atmospheric reanalysis data, both modern and for the full 20th century. Blocking is approximately in phase with Atlantic multidecadal ocean variability (AMV). Wintertime atmospheric blocking involves a highly distorted jetstream, isolating large regions of air from the westerly circulation. It influences the ocean through windstress-curl and associated air/sea heat flux. While blocking is a relatively high-frequency phenomenon, it is strongly modulated over decadal timescales. The blocked regime (weaker ocean gyres, weaker air-sea heat flux, paradoxically increased transport of warm subtropical waters poleward) contributes to the warm phase of AMV. Atmospheric blocking better describes the early 20thC warming and 1996-2010 warm period than does the NAO index. It has roots in the hemispheric circulation and jet stream dynamics. Subpolar Atlantic variability covaries with distant AMOC fields: both these connections may express the global influence of the subpolar North Atlantic ocean on the global climate system. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48.1841V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48.1841V">Decadal climate prediction with a refined anomaly initialisation approach</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Volpi, Danila; Guemas, Virginie; Doblas-Reyes, Francisco J.; Hawkins, Ed; Nichols, Nancy K. 2017-03-01 In decadal prediction, the objective is to exploit both the sources of predictability from the external radiative forcings and from the internal variability to provide the best possible climate information for the next decade. Predicting the climate system internal variability relies on initialising the climate model from observational estimates. We present a refined method of anomaly initialisation (AI) applied to the ocean and sea ice components of the global climate forecast model EC-Earth, with the following key innovations: (1) the use of a weight applied to the observed anomalies, in order to avoid the risk of introducing anomalies recorded in the observed climate, whose amplitude does not fit in the range of the internal variability generated by the model; (2) the AI of the ocean density, instead of calculating it from the anomaly initialised state of temperature and salinity. An experiment initialised with this refined AI method has been compared with a full field and standard AI experiment. Results show that the use of such refinements enhances the surface temperature skill over part of the North and South Atlantic, part of the South Pacific and the Mediterranean Sea for the first forecast year. However, part of such improvement is lost in the following forecast years. For the tropical Pacific surface temperature, the full field initialised experiment performs the best. The prediction of the Arctic sea-ice volume is improved by the refined AI method for the first three forecast years and the skill of the Atlantic multidecadal oscillation is significantly increased compared to a non-initialised forecast, along the whole forecast time. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160013870','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160013870">AERONET Version 3 Release: Providing Significant Improvements for Multi-Decadal Global Aerosol Database and Near Real-Time Validation</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Holben, Brent; Slutsker, Ilya; Giles, David; Eck, Thomas; Smirnov, Alexander; Sinyuk, Aliaksandr; Schafer, Joel; Sorokin, Mikhail; Rodriguez, Jon; Kraft, Jason; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20160013870'); toggleEditAbsImage('author_20160013870_show'); toggleEditAbsImage('author_20160013870_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20160013870_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20160013870_hide"> 2016-01-01 Aerosols are highly variable in space, time and properties. Global assessment from satellite platforms and model predictions rely on validation from AERONET, a highly accurate ground-based network. Ver. 3 represents a significant improvement in accuracy and quality. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=317711&Lab=NERL&keyword=Remote+AND+sensing&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=317711&Lab=NERL&keyword=Remote+AND+sensing&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Assessment of the Interactions Among Tropospheric Aerosol Loading, Radiative Balance and Clouds Through Examination of Their Multi-decadal Trends</a> <a target="_blank" rel="noopener noreferrer" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> While aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of aerosol radiative forcing has remained challenging. Anthropogenic emissions of prima... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...24Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...24Y">Variability and predictability of decadal mean temperature and precipitation over China in the CCSM4 last millennium simulation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ying, Kairan; Frederiksen, Carsten S.; Zheng, Xiaogu; Lou, Jiale; Zhao, Tianbao 2018-02-01 The modes of variability that arise from the slow-decadal (potentially predictable) and intra-decadal (unpredictable) components of decadal mean temperature and precipitation over China are examined, in a 1000 year (850-1850 AD) experiment using the CCSM4 model. Solar variations, volcanic aerosols, orbital forcing, land use, and greenhouse gas concentrations provide the main forcing and boundary conditions. The analysis is done using a decadal variance decomposition method that identifies sources of potential decadal predictability and uncertainty. The average potential decadal predictabilities (ratio of slow-to-total decadal variance) are 0.62 and 0.37 for the temperature and rainfall over China, respectively, indicating that the (multi-)decadal variations of temperature are dominated by slow-decadal variability, while precipitation is dominated by unpredictable decadal noise. Possible sources of decadal predictability for the two leading predictable modes of temperature are the external radiative forcing, and the combined effects of slow-decadal variability of the Arctic oscillation (AO) and the Pacific decadal oscillation (PDO), respectively. Combined AO and PDO slow-decadal variability is associated also with the leading predictable mode of precipitation. External radiative forcing as well as the slow-decadal variability of PDO are associated with the second predictable rainfall mode; the slow-decadal variability of Atlantic multi-decadal oscillation (AMO) is associated with the third predictable precipitation mode. The dominant unpredictable decadal modes are associated with intra-decadal/inter-annual phenomena. In particular, the El Niño-Southern Oscillation and the intra-decadal variability of the AMO, PDO and AO are the most important sources of prediction uncertainty. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CliPa..14..577S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CliPa..14..577S">Timescale dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shi, Jian; Yan, Qing; Wang, Huijun 2018-04-01 Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variations based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM-precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase III and Community Earth System Model to investigate the stability of the EASM-precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) was enhanced in the Medieval Climate Anomaly (MCA; ˜ 950-1250 AD), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ˜ 1500-1800 AD), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM-precipitation relationship is only stable on a centennial and longer timescale and is unstable on a shorter timescale. The nonstationary short-timescale EASM-precipitation relationship broadly exhibits a multi-decadal periodicity, which may be attributed to the internal variability of the climate system and has no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP52A..08C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP52A..08C">Two Centuries of Climate Variability From a Gulf of Papua Coral Confirms a Coherent, Widespread Multidecadal Signal</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cole, J. E.; Lough, J.; Reed, E. V.; Schrag, D. P. 2016-12-01 The Indo-Pacific warm pool is intimately involved with large-scale climate variability on seasonal to secular time scales. The lack of long instrumental observations in this region has motivated paleoclimatic analyses using diverse proxy data sources. We present here new multicentury paleoclimate records from a Gulf of Papua coral that capture past variability with a Pacific-wide signature. We have developed stable isotope, Sr/Ca, skeletal density, and luminescence data from a coral core recovered at Bramble Cay, Australia (9°S, 144°E). The geochemical records span CE 1775-1993 and are dominated by low-frequency (decade-century scale) variability that is consistent with records from other proxies in the same region, and with other coral records from far-flung sites across the southwest Pacific. Unlike in many Pacific coral records, we observe no strong trend towards warmer conditions. Although skeletal density bands are clearly visible, they show inconsistent seasonal phasing with the geochemical tracers of sea surface temperature (SST; Sr/Ca and oxygen isotope content), and skeletal density does not correlate with these tracers on longer time scales. In this coral, density banding must be controlled by a more complex mix of internal and/or external factors. Luminescent banding and reconstructed salinity provide similar histories, suggesting a common hydroclimatic signal with significant variability at periods of decades and longer. The strong low-frequency behavior in these new climate records of SST and hydroclimate, from a remote region of the Indo-Pacific, confirms an important source of internal climate variability, on a poorly documented time scale, from a region with far-reaching climatic importance. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...44..229R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...44..229R">Combined influences of seasonal East Atlantic Pattern and North Atlantic Oscillation to excite Atlantic multidecadal variability in a climate model</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ruprich-Robert, Yohan; Cassou, Christophe 2015-01-01 The physical processes underlying the internal component of the Atlantic Multidecadal Variability (AMV) are investigated from a 1,000-yr pre-industrial control simulation of the CNRM-CM5 model. The low-frequency fluctuations of the Atlantic Meridional Overturning Circulation (AMOC) are shown to be the main precursor for the model AMV. The full life cycle of AMOC/AMV events relies on a complex time-evolving relationship with both North Atlantic Oscillation (NAO) and East Atlantic Pattern (EAP) that must be considered from a seasonal perspective in order to isolate their action; the ocean is responsible for setting the multidecadal timescale of the fluctuations. AMOC rise leading to a warm phase of AMV is statistically preceded by wintertime NAO+ and EAP+ from ~Lag -40/-20 yrs. Associated wind stress anomalies induce an acceleration of the subpolar gyre (SPG) and enhanced northward transport of warm and saline subtropical water. Concurrent positive salinity anomalies occur in the Greenland-Iceland-Norwegian Seas in link to local sea-ice decline; those are advected by the Eastern Greenland Current to the Labrador Sea participating to the progressive densification of the SPG and the intensification of ocean deep convection leading to AMOC strengthening. From ~Lag -10 yrs prior an AMOC maximum, opposite relationship is found with the NAO for both summer and winter seasons. Despite negative lags, NAO- at that time is consistent with the atmospheric response through teleconnection to the northward shift/intensification of the Inter Tropical Convergence Zone in link to the ongoing warming of tropical north Atlantic basin due to AMOC rise/AMV build-up. NAO- acts as a positive feedback for the full development of the model AMV through surface fluxes but, at the same time, prepares its termination through negative retroaction on AMOC. Relationship between EAP+ and AMOC is also present in summer from ~Lags -30/+10 yrs while winter EAP- is favored around the AMV peak. Based on additional atmospheric-forced experiments, both are interpreted as the local seasonal-dependent atmospheric response to warmer North Atlantic. Finally, advection of fresher water from the tropical basin created by local atmosphere/ocean anomalous circulation on one hand and from the Arctic on the other hand due to large-scale sea ice melting leads to decrease of density in the SPG and contributes terminating the model AMOC/AMV events. All together, the combined effects of NAO and EAP, their intertwined seasonal forcing/forced role upon/by the ocean and the primary role of salinity anomalies associated with oceanic dynamical changes acting as an integrator are responsible in CNRM-CM5 for an irregular and damped mode of variability for AMOC/AMV that takes about 35-40 (15-20) years to build up (dissipate). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS31C1734C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS31C1734C">Predictability of Subsurface Temperature and the AMOC</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chang, Y.; Schubert, S. D. 2013-12-01 GEOS 5 coupled model is extensively used for experimental decadal climate prediction. Understanding the limits of decadal ocean predictability is critical for making progress in these efforts. Using this model, we study the subsurface temperature initial value predictability, the variability of the Atlantic meridional overturning circulation (AMOC) and its impacts on the global climate. Our approach is to utilize the idealized data assimilation technology developed at the GMAO. The technique 'replay' allows us to assess, for example, the impact of the surface wind stresses and/or precipitation on the ocean in a very well controlled environment. By running the coupled model in replay mode we can in fact constrain the model using any existing reanalysis data set. We replay the model constraining (nudging) it to the MERRA reanalysis in various fields from 1948-2012. The fields, u,v,T,q,ps, are adjusted towards the 6-hourly analyzed fields in atmosphere. The simulated AMOC variability is studied with a 400-year-long segment of replay integration. The 84 cases of 10-year hindcasts are initialized from 4 different replay cycles. Here, the variability and predictability are examined further by a measure to quantify how much the subsurface temperature and AMOC variability has been influenced by atmospheric forcing and by ocean internal variability. The simulated impact of the AMOC on the multi-decadal variability of the SST, sea surface height (SSH) and sea ice extent is also studied. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSMG14A1922G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSMG14A1922G">Multi-Decadal Coastal Behavioural States From A Fusion Of Geohistorical Conceptual Modelling With 2-D Morphodynamic Modelling</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Goodwin, I. D.; Mortlock, T. 2016-02-01 Geohistorical archives of shoreline and foredune planform geometry provides a unique evidence-based record of the time integral response to coupled directional wave climate and sediment supply variability on annual to multi-decadal time scales. We develop conceptual shoreline modelling from the geohistorical shoreline archive using a novel combination of methods, including: LIDAR DEM and field mapping of coastal geology; a decadal-scale climate reconstruction of sea-level pressure, marine windfields, and paleo-storm synoptic type and frequency, and historical bathymetry. The conceptual modelling allows for the discrimination of directional wave climate shifts and the relative contributions of cross-shore and along-shore sand supply rates at multi-decadal resolution. We present regional examples from south-eastern Australia over a large latitudinal gradient from subtropical Queensland (S 25°) to mid-latitude Bass Strait (S 40°) that illustrate the morphodynamic evolution and reorganization to wave climate change. We then use the conceptual modeling to inform a two-dimensional coupled spectral wave-hydrodynamic-morphodynamic model to investigate the shoreface response to paleo-directional wind and wave climates. Unlike one-line shoreline modelling, this fully dynamical approach allows for the investigation of cumulative and spatial bathymetric change due to wave-induced currents, as well as proxy-shoreline change. The fusion of the two modeling approaches allows for: (i) the identification of the natural range of coastal planform geometries in response to wave climate shifts; and, (ii) the decomposition of the multidecadal coastal change into the cross-shore and along-shore sand supply drivers, according to the best-matching planforms. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoRL..3923706N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoRL..3923706N">Multidecadal climate variability in Brazil's Nordeste during the last 3000 years based on speleothem isotope records</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Novello, Valdir F.; Cruz, Francisco W.; Karmann, Ivo; Burns, Stephen J.; Stríkis, Nicolás M.; Vuille, Mathias; Cheng, Hai; Lawrence Edwards, R.; Santos, Roberto V.; Frigo, Everton; Barreto, Eline A. S. 2012-12-01 We present the first high resolution, approximately ∼4 years sample spacing, precipitation record from northeastern Brazil (hereafter referred to as ‘Nordeste’) covering the last ∼3000 yrs from 230Th-dated stalagmites oxygen isotope records. Our record shows abrupt fluctuations in rainfall tied to variations in the intensity of the South American summer monsoon (SASM), including the periods corresponding to the Little Ice Age (LIA), the Medieval Climate Anomaly (MCA) and an event around 2800 yr B.P. Unlike other monsoon records in southern tropical South America, dry conditions prevailed during the LIA in the Nordeste. Our record suggests that the region is currently undergoing drought conditions that are unprecedented over the past 3 millennia, rivaled only by the LIA period. Using spectral, wavelet and cross-wavelet analyses we show that changes in SASM activity in the region are mainly associated with variations of the Atlantic Multidecadal Oscillation (AMO) and to a lesser degree caused by fluctuations in tropical Pacific SST. Our record also shows a distinct periodicity around 210 years, which has been linked to solar variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A33N..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A33N..05G">ENSO and its modulations on annual and multidecadal timescales revealed by Nonlinear Laplacian Spectral Analysis</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Giannakis, D.; Slawinska, J. M. 2016-12-01 The variability of the Indo-Pacific Ocean on interannual to multidecadal timescales is investigated in a millennial control run of CCSM4 and in observations using a recently introduced technique called Nonlinear Laplacian Spectral Analysis (NLSA). Through this technique, drawbacks associated with ad hoc pre-filtering of the input data are avoided, enabling recovery of low-frequency and intermittent modes not accessible previously via classical approaches. Here, a multiscale hierarchy of modes is identified for Indo-Pacific SST and numerous linkages between these patterns are revealed. On interannual timescales, a mode with spatiotemporal pattern corresponding to the fundamental component of ENSO emerges, along with modulations of the annual cycle by ENSO in agreement with ENSO combination mode theory. In spatiotemporal reconstructions, these patterns capture the seasonal southward migration of SST and zonal wind anomalies associated with termination of El Niño and La Niña events. Notably, this family of modes explains a significant portion of SST variance in Eastern Indian Ocean regions employed in the definition of Indian Ocean dipole (IOD) indices, suggesting that it should be useful for understanding the linkage of these indices with ENSO and the interaction of the Indian and Pacific Oceans. In model data, we find that the ENSO and ENSO combination modes are modulated on multidecadal timescales by a mode predominantly active in the western tropical Pacific - we call this mode West Pacific Multidecadal Oscillation (WPMO). Despite the relatively low variance explained by this mode, its dynamical role appears to be significant as it has clear sign-dependent modulating relationships with the interannual modes carrying most of the variance. In particular, cold WPMO events are associated with anomalous Central Pacific westerlies favoring stronger ENSO events, while warm WPMO events suppress ENSO activity. Moreover, the WPMO has significant climatic impacts as demonstrated here through its strong correlation with decadal precipitation over Australia. As an extension of this work, we discuss the deterministic and stochastic aspects of the variability of these modes and their potential predictability based on nonparametric kernel analog forecasting techniques. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51L..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51L..07D">The North Atlantic Oscillation as a driver of multidecadal variability of the AMOC, the AMO, and Northern Hemisphere climate</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Delworth, T. L.; Zeng, F. J.; Yang, X.; Zhang, L. 2017-12-01 We use suites of simulations with coupled ocean-atmosphere models to show that multidecadal changes in the North Atlantic Oscillation (NAO) can drive multidecadal changes in the Atlantic Meridional Overturning Circulation (AMOC) and the Atlantic Multidecadal Oscillation (AMO), with associated hemispheric climatic impacts. These impacts include rapid changes in Arctic sea ice, hemispheric temperature, and modulation of Atlantic hurricane activity. We use models that incorporate either a fully dynamic ocean or a simple slab ocean to explore the role of ocean dynamics and ocean-atmosphere interactions. A positive phase of the NAO is associated with strengthened westerly winds over the North Atlantic. These winds extract more heat than normal from the subpolar ocean, thereby increasing upper ocean density, deepwater formation, and the strength of the AMOC and associated poleward ocean heat transport. This warming leads to a positive phase of the AMO. The enhanced oceanic heat transport extends to the Arctic where it causes a reduction of Arctic sea ice. Large-scale atmospheric warming reduces vertical wind shear in the tropical North Atlantic, creating an environment more favorable for tropical storms. We use models to further show that observed multidecadal variations of the NAO over the 20th and early 21st centuries may have led to multidecadal variations of simulated AMOC and the AMO. Specifically, negative NAO values from the late 1960s through the early 1980s led to a weakened AMOC/cold North Atlantic, whereas increasing NAO values from the late 1980s through the late 1990s increased the model AMOC and led to a positive (warm) phase of the AMO. The warm phase contributed to increases in tropical storm activity and decreases in Arctic sea ice after the mid 1990s. Ocean dynamics are essential for translating the observed NAO variations into ocean heat content variations for the extratropical North Atlantic, but appear less important in the tropical North Atlantic. The observed AMO has substantial SST amplitude in both the tropical and extratropical North Atlantic. These results suggest that additional factors, such as cloud feedback, dust feedback, and anthropogenic radiative forcing, may play a crucial role for the tropical expression of the AMO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990106583','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990106583">Vegetation Interaction Enhances Interdecadal Climate Variability in the Sahel</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Zeng, Ning; Neelin, J. David; Lau, William K.-M. 1999-01-01 The role of naturally varying vegetation in influencing the climate variability in the Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea surface temperature (SST) variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation significantly, but can reduce year to year variability due to a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall, in particular, the multi-decadal drying trend from the 1950s to the 80s. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG51B..02P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG51B..02P">Global Surface Temperature Anomalies and Attribution</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pietrafesa, L. J. 2017-12-01 We study Non-Stationary, Non-Linear time series of global surface temperatures from 1850 to 2016, and via an empirical, mathematical methodology, we reveal the buried, internal modes of variability of planetary temperatures over the past 167 years, and find periods of cooling and warming, both in the ocean and the atmosphere over land, with multiple modes of variability; seasonal, annual, inter-annual, multi-year, decadal, multi-decadal, centennial and overall warming trends in the ocean, atmosphere and the combination therein. The oceanic rate of warming is less than two thirds of that of the atmosphere. While our findings on overall trends of fossil fuel burning and planetary temperatures are only visually correlative, by employing a mathematical methodology well known in ergonomics, this study causally links the upward rise in planetary surface temperature from the latter part of the 19th Century and into the 21st Century, to the contemporaneous upward rise in fossil fuel burning and suggests that if present fossil fuel burning is not curtailed there will be continued warming of the planet in the future. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/biblio/1244792-interannual-modulation-subtropical-atlantic-boreal-summer-dust-variability-enso','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1244792-interannual-modulation-subtropical-atlantic-boreal-summer-dust-variability-enso">Interannual Modulation of Subtropical Atlantic Boreal Summer Dust Variability by ENSO</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> DeFlorio, Mike; Goodwin, Ian D.; Cayan, Dan 2016-01-01 Dust variability in the climate system has been studied for several decades, yet there remains an incomplete understanding of the dynamical mechanisms controlling interannual and decadal variations in dust transport. The sparseness of multi-year observational datasets has limited our understanding of the relationship between climate variations and atmospheric dust. We use available observations and a century-length fully coupled Community Earth System Model (CESM) simulation to show that the El Niño- Southern Oscillation (ENSO) exerts a control on North African dust transport during boreal summer. In CESM, this relationship is stronger over the dusty tropical North Atlantic than near Barbados, onemore » of the few sites having a multi-decadal observed record. During strong La Niña summers in CESM, a statistically significant increase in lower tropospheric easterly wind is associated with an increase in North African dust transport over the Atlantic. Barbados dust and Pacific SST variability are only weakly correlated in both observations and CESM, suggesting that other processes are controlling the crossbasin variability of dust. We also use our CESM simulation to show that the relationship between downstream North African dust transport and ENSO fluctuates on multidecadal timescales and may be modulated by the North Atlantic Oscillation (NAO). Our findings indicate that existing observations of dust over the tropical North Atlantic are not extensive enough to completely describe the variability of dust and dust transport, and demonstrate the importance of global models to supplement and interpret observational records.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5462496','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5462496">Reconstructed storm tracks reveal three centuries of changing moisture delivery to North America</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wise, Erika K.; Dannenberg, Matthew P. 2017-01-01 Moisture delivery to western North America is closely linked to variability in the westerly storm tracks of midlatitude cyclones, which are, in turn, modified by larger-scale features such as the El Niño–Southern Oscillation system. Instrumental and modeling data suggest that extratropical storm tracks may be intensifying and shifting poleward due to anthropogenic climate change, but it is difficult to separate recent trends from natural variability because of the large amount of decadal and longer variation in storm tracks and their limited instrumental record. We reconstruct cool-season, midlatitude Pacific storm-track position and intensity from 1693 to 1995 CE using existing tree-ring chronologies along with a network of newly developed chronologies from the U.S. Pacific Northwest, where small variations in storm-track position can have a major influence on hydroclimate patterns. Our results show high interannual-to-multidecadal variability in storm-track position and intensity over the past 303 years, with spectral signatures characteristic of tropical and northern Pacific influences. Comparison with reconstructions of precipitation and tropical sea surface temperature confirms the relationship between shifting drought patterns in the Pacific Northwest and storm-track variability through time and demonstrates the long-term influence of El Niño. These results allow us to place recent storm-track changes in the context of decadal and multidecadal fluctuations across the long-term record, showing that recent changes in storm-track intensity likely represent a warming-related increase amplified by natural decadal variability. PMID:28630900 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28630900','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28630900">Reconstructed storm tracks reveal three centuries of changing moisture delivery to North America.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wise, Erika K; Dannenberg, Matthew P 2017-06-01 Moisture delivery to western North America is closely linked to variability in the westerly storm tracks of midlatitude cyclones, which are, in turn, modified by larger-scale features such as the El Niño-Southern Oscillation system. Instrumental and modeling data suggest that extratropical storm tracks may be intensifying and shifting poleward due to anthropogenic climate change, but it is difficult to separate recent trends from natural variability because of the large amount of decadal and longer variation in storm tracks and their limited instrumental record. We reconstruct cool-season, midlatitude Pacific storm-track position and intensity from 1693 to 1995 CE using existing tree-ring chronologies along with a network of newly developed chronologies from the U.S. Pacific Northwest, where small variations in storm-track position can have a major influence on hydroclimate patterns. Our results show high interannual-to-multidecadal variability in storm-track position and intensity over the past 303 years, with spectral signatures characteristic of tropical and northern Pacific influences. Comparison with reconstructions of precipitation and tropical sea surface temperature confirms the relationship between shifting drought patterns in the Pacific Northwest and storm-track variability through time and demonstrates the long-term influence of El Niño. These results allow us to place recent storm-track changes in the context of decadal and multidecadal fluctuations across the long-term record, showing that recent changes in storm-track intensity likely represent a warming-related increase amplified by natural decadal variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.G51B..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.G51B..07W">Changes in US extreme sea levels and the role of large scale climate variations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wahl, T.; Chambers, D. P. 2015-12-01 We analyze a set of 20 tide gauge records covering the contiguous United States (US) coastline and the period from 1929 to 2013 to identify long-term trends and multi-decadal variations in extreme sea levels (ESLs) relative to changes in mean sea level (MSL). Significant but small long-term trends in ESLs above/below MSL are found at individual sites along most coastline stretches, but are mostly confined to the southeast coast and the winter season when storm surges are primarily driven by extra-tropical cyclones. We identify six regions with broadly coherent and considerable multi-decadal ESL variations unrelated to MSL changes. Using a quasi-non-stationary extreme value analysis approach we show that the latter would have caused variations in design relevant return water levels (RWLs; 50 to 200 year return periods) ranging from ~10 cm to as much as 110 cm across the six regions. To explore the origin of these temporal changes and the role of large-scale climate variability we develop different sets of simple and multiple linear regression models with RWLs as dependent variables and climate indices, or tailored (toward the goal of predicting multi-decadal RWL changes) versions of them, and wind stress curl as independent predictors. The models, after being tested for spatial and temporal stability, explain up to 97% of the observed variability at individual sites and almost 80% on average. Using the model predictions as covariates for the quasi-non-stationary extreme value analysis also significantly reduces the range of change in the 100-year RWLs over time, turning a non-stationary process into a stationary one. This highlights that the models - when used with regional and global climate model output of the predictors - should also be capable of projecting future RWL changes to be used by decision makers for improved flood preparedness and long-term resiliency. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018HESS...22.3155L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018HESS...22.3155L">Interannual-to-multidecadal hydroclimate variability and its sectoral impacts in northeastern Argentina</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lovino, Miguel A.; Müller, Omar V.; Müller, Gabriela V.; Sgroi, Leandro C.; Baethgen, Walter E. 2018-06-01 This study examines the joint variability of precipitation, river streamflow and temperature over northeastern Argentina; advances the understanding of their links with global SST forcing; and discusses their impacts on water resources, agriculture and human settlements. The leading patterns of variability, and their nonlinear trends and cycles are identified by means of a principal component analysis (PCA) complemented with a singular spectrum analysis (SSA). Interannual hydroclimatic variability centers on two broad frequency bands: one of 2.5-6.5 years corresponding to El Niño Southern Oscillation (ENSO) periodicities and the second of about 9 years. The higher frequencies of the precipitation variability (2.5-4 years) favored extreme events after 2000, even during moderate extreme phases of the ENSO. Minimum temperature is correlated with ENSO with a main frequency close to 3 years. Maximum temperature time series correlate well with SST variability over the South Atlantic, Indian and Pacific oceans with a 9-year frequency. Interdecadal variability is characterized by low-frequency trends and multidecadal oscillations that have induced a transition from dryer and cooler climate to wetter and warmer decades starting in the mid-twentieth century. The Paraná River streamflow is influenced by North and South Atlantic SSTs with bidecadal periodicities. The hydroclimate variability at all timescales had significant sectoral impacts. Frequent wet events between 1970 and 2005 favored floods that affected agricultural and livestock productivity and forced population displacements. On the other hand, agricultural droughts resulted in soil moisture deficits that affected crops at critical growth stages. Hydrological droughts affected surface water resources, causing water and food scarcity and stressing the capacity for hydropower generation. Lastly, increases in minimum temperature reduced wheat and barley yields. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CSR...143..278M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CSR...143..278M">Decadal sea level variability in the East China Sea linked to the North Pacific Gyre Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Moon, Jae-Hong; Song, Y. Tony 2017-07-01 In view of coastal community's need for adapting to sea level rise (SLR), understanding and predicting regional variability on decadal to longer time scales still remain a challenging issue in SLR research. Here, we have examined the low-frequency sea level signals in the East China Sea (ECS) from the 50-year hindcast of a non-Boussinesq ocean model in comparison with data sets from altimeters, tide-gauges, and steric sea level produced by in-situ profiles. It is shown that the mean sea levels in the ECS represent significant decadal fluctuations over the past 50 years, with a multi-decadal trend shift since the mid-1980s compared to the preceding 30 years. The decadal fluctuations in sea level are more closely linked to the North Pacific Gyre Oscillation (NPGO) rather than the Pacific Decadal Oscillation, which reflects the multi-decadal trend shift. A composite analysis indicates that wind patterns associated with the NPGO is shown to control the decadal variability of the western subtropical North Pacific. A positive NPGO corresponds to cyclonic wind stress curl anomaly in the western subtropical regions that results in a higher sea level in the ECS, particularly along the continental shelf, and lower sea levels off the ECS. The reverse occurs in years of negative NPGO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70178534','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70178534">Multi-species coral Sr/Ca-based sea-surface temperature reconstruction using Orbicella faveolata and Siderastrea siderea from the Florida Straits</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Flannery, Jennifer A.; Richey, Julie N.; Thirumalai, Kaustubh; Poore, Richard Z.; DeLong, Kristine L. 2017-01-01 We present new, monthly-resolved Sr/Ca-based sea-surface temperature (SST) records from two species of massive coral, Orbicella faveolata and Siderastrea siderea, from the Dry Tortugas National Park, FL, USA (DTNP). We combine these new records with published data from three additional S. siderea coral colonies to generate a 278-year long multi-species stacked Sr/Ca-SST record from DTNP. The composite record of mean annual Sr/Ca-SST at DTNP shows pronounced decadal-scale variability with a range of 1 to 2°C. Notable cool intervals in the Sr/Ca-derived SST lasting about a decade centered at ~1845, ~1935, and ~1965 are associated with reduced summer Sr/Ca-SST (monthly maxima < 29°C), and imply a reduction in the spatial extent of the Atlantic Warm Pool (AWP). There is significant coherence between the composite DTNP Sr/Ca-SST record and the Atlantic Multidecadal Oscillation (AMO) index, with the AMO lagging Sr/Ca-SST at DTNP by 9 years. Low frequency variability in the Gulf Stream surface transport, which originates near DTNP, may provide a link for the lagged relationship between multidecadal variability at DTNP and the AMO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70186185','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70186185">Trends and natural variability of North American spring onset as evaluated by a new gridded dataset of spring indices</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ault, Toby R.; Schwartz, Mark D.; Zurita-Milla, Raul; Weltzin, Jake F.; Betancourt, Julio L. 2015-01-01 Climate change is expected to modify the timing of seasonal transitions this century, impacting wildlife migrations, ecosystem function, and agricultural activity. Tracking seasonal transitions in a consistent manner across space and through time requires indices that can be used for monitoring and managing biophysical and ecological systems during the coming decades. Here a new gridded dataset of spring indices is described and used to understand interannual, decadal, and secular trends across the coterminous United States. This dataset is derived from daily interpolated meteorological data, and the results are compared with historical station data to ensure the trends and variations are robust. Regional trends in the first leaf index range from 20.8 to 21.6 days decade21, while first bloom index trends are between20.4 and 21.2 for most regions. However, these trends are modulated by interannual to multidecadal variations, which are substantial throughout the regions considered here. These findings emphasize the important role large-scale climate modes of variability play in modulating spring onset on interannual to multidecadal time scales. Finally, there is some potential for successful subseasonal forecasts of spring onset, as indices from most regions are significantly correlated with antecedent large-scale modes of variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B23K..03A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B23K..03A">Trends and Natural Variability of Spring Onset in the Coterminous United States as Evaluated by a New Gridded Dataset of Spring Indices</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ault, T.; Schwartz, M. D.; Zurita-Milla, R.; Weltzin, J. F.; Betancourt, J. L. 2015-12-01 Climate change is expected to modify the timing of seasonal transitions this century, impacting wildlife migrations, ecosystem function, and agricultural activity. Tracking seasonal transitions in a consistent manner across space and through time requires indices that can be used for monitoring and managing biophysical and ecological systems during the coming decades. Here a new gridded dataset of spring indices is described and used to understand interannual, decadal, and secular trends across the coterminous US. This dataset is derived from daily interpolated meteorological data, and results are compared with historical station data to ensure the trends and variations are robust. Regional trends in the first leaf index range from -0.8 to -1.6 days per decade, while first bloom index trends are between -0.4 and -1.2 for most regions. However, these trends are modulated by interannual to multidecadal variations, which are substantial throughout the regions considered here. These findings emphasize the important role large-scale climate modes of variability play in modulating spring onset on interannual to multidecadal timescales. Finally, there is some potential for successful sub-seasonal forecasts of spring onset, as indices from most regions are significantly correlated with antecedent large-scale modes of variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA621273','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA621273">Multi-Decadal Variability in the Bering Sea: A Synthesis of Model Results and Observations from 1948 to the Present</a> <a target="_blank" rel="noopener noreferrer" href="http://www.dtic.mil/">DTIC Science & Technology</a> 2013-12-01 stated that the development and use of high-resolution Arctic climate and systems models are important stepping stones for dedicated studies of...W., J. L. Clement Kinney, D. C. Marble , and J. Jakacki, 2008: Towards eddy resolving models of the Arctic Ocean: Ocean Modeling in an Eddying </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311406&Lab=NERL&keyword=Remote+AND+sensing&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311406&Lab=NERL&keyword=Remote+AND+sensing&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Simulating Changes in Tropospheric Aerosol Burden and its Radiative Effects across the Northern Hemisphere: Contrasting Multi-Decadal Trends between Asia and North America</a> <a target="_blank" rel="noopener noreferrer" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Though aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of the magnitude and directionality of aerosol radiative forcing has remained challeng... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC22B..05T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC22B..05T">European Climate and Pinot Noir Grape-Harvest Dates in Burgundy, since the 17th Century</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tourre, Y. M. 2011-12-01 Time-series of growing season air temperature anomalies in the Parisian region and of 'Pinot Noir' grape-harvest dates (GHD) in Burgundy (1676-2004) are analyzed in the frequency-domain. Variability of both time-series display three significant frequency-bands (peaks significant at the 5% level) i.e., a low-frequency band (multi-decadal) with a 25-year peak period; a 3-to-8 year band period (inter-annual) with a 3.1-year peak period; and a 2-to-3 year band period (quasi-biennial) with a 2.4-year peak period. Joint sea surface temperature/sea level pressure (SST/SLP) empirical orthogonal functions (EOF) analyses during the 20th century, along with spatio-temporal patterns for the above frequency-bands are presented. It is found that SST anomalies display early significant spatial SST patterns in the North Atlantic Ocean (air temperature lagging by 6 months) similar to those obtained from EOF analyses. It is thus proposed that the robust power spectra for the above frequency-bands could be linked with Atlantic climate variability metrics modulating Western European climate i.e., 1) the global Multi-decadal Oscillation (MDO) with its Atlantic Multi-decadal Oscillation (AMO) footprint; 2) the Atlantic Inter-Annual (IA) fluctuations; and 3) the Atlantic Quasi-Biennial (QB) fluctuations, respectively. Moreover these specific Western European climate signals have effects on ecosystem health and can be perceived as contributors to the length of the growing season and the timing of GHD in Burgundy. Thus advance knowledge on the evolution and phasing of the above climate fluctuations become important elements for viticulture and wine industry management. It is recognized that anthropogenic effects could have modified time-series patterns presented here, particularly since the mid 1980s. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC41A1000H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC41A1000H">Macroweather Predictions and Climate Projections using Scaling and Historical Observations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hébert, R.; Lovejoy, S.; Del Rio Amador, L. 2017-12-01 There are two fundamental time scales that are pertinent to decadal forecasts and multidecadal projections. The first is the lifetime of planetary scale structures, about 10 days (equal to the deterministic predictability limit), and the second is - in the anthropocene - the scale at which the forced anthropogenic variability exceeds the internal variability (around 16 - 18 years). These two time scales define three regimes of variability: weather, macroweather and climate that are respectively characterized by increasing, decreasing and then increasing varibility with scale.We discuss how macroweather temperature variability can be skilfully predicted to its theoretical stochastic predictability limits by exploiting its long-range memory with the Stochastic Seasonal and Interannual Prediction System (StocSIPS). At multi-decadal timescales, the temperature response to forcing is approximately linear and this can be exploited to make projections with a Green's function, or Climate Response Function (CRF). To make the problem tractable, we exploit the temporal scaling symmetry and restrict our attention to global mean forcing and temperature response using a scaling CRF characterized by the scaling exponent H and an inner scale of linearity τ. An aerosol linear scaling factor α and a non-linear volcanic damping exponent ν were introduced to account for the large uncertainty in these forcings. We estimate the model and forcing parameters by Bayesian inference using historical data and these allow us to analytically calculate a median (and likely 66% range) for the transient climate response, and for the equilibrium climate sensitivity: 1.6K ([1.5,1.8]K) and 2.4K ([1.9,3.4]K) respectively. Aerosol forcing typically has large uncertainty and we find a modern (2005) forcing very likely range (90%) of [-1.0, -0.3] Wm-2 with median at -0.7 Wm-2. Projecting to 2100, we find that to keep the warming below 1.5 K, future emissions must undergo cuts similar to Representative Concentration Pathway (RCP) 2.6 for which the probability to remain under 1.5 K is 48%. RCP 4.5 and RCP 8.5-like futures overshoot with very high probability. This underscores that over the next century, the state of the environment will be strongly influenced by past, present and future economical policies. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG41A0121M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG41A0121M">Extracting Leading Nonlinear Modes of Changing Climate From Global SST Time Series</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mukhin, D.; Gavrilov, A.; Loskutov, E. M.; Feigin, A. M.; Kurths, J. 2017-12-01 Data-driven modeling of climate requires adequate principal variables extracted from observed high-dimensional data. For constructing such variables it is needed to find spatial-temporal patterns explaining a substantial part of the variability and comprising all dynamically related time series from the data. The difficulties of this task rise from the nonlinearity and non-stationarity of the climate dynamical system. The nonlinearity leads to insufficiency of linear methods of data decomposition for separating different processes entangled in the observed time series. On the other hand, various forcings, both anthropogenic and natural, make the dynamics non-stationary, and we should be able to describe the response of the system to such forcings in order to separate the modes explaining the internal variability. The method we present is aimed to overcome both these problems. The method is based on the Nonlinear Dynamical Mode (NDM) decomposition [1,2], but takes into account external forcing signals. An each mode depends on hidden, unknown a priori, time series which, together with external forcing time series, are mapped onto data space. Finding both the hidden signals and the mapping allows us to study the evolution of the modes' structure in changing external conditions and to compare the roles of the internal variability and forcing in the observed behavior. The method is used for extracting of the principal modes of SST variability on inter-annual and multidecadal time scales accounting the external forcings such as CO2, variations of the solar activity and volcanic activity. The structure of the revealed teleconnection patterns as well as their forecast under different CO2 emission scenarios are discussed.[1] Mukhin, D., Gavrilov, A., Feigin, A., Loskutov, E., & Kurths, J. (2015). Principal nonlinear dynamical modes of climate variability. Scientific Reports, 5, 15510. [2] Gavrilov, A., Mukhin, D., Loskutov, E., Volodin, E., Feigin, A., & Kurths, J. (2016). Method for reconstructing nonlinear modes with adaptive structure from multidimensional data. Chaos: An Interdisciplinary Journal of Nonlinear Science, 26(12), 123101. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010390','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010390">Northern North Atlantic Sea Surface Height and Ocean Heat Content Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hakkinen, Sirpa; Rhines, Peter; Worthen, Denise L. 2013-01-01 The evolution of nearly 20 years of altimetric sea surface height (SSH) is investigated to understand its association with decadal to multidecadal variability of the North Atlantic heat content. Altimetric SSH is dominated by an increase of about 14 cm in the Labrador and Irminger seas from 1993 to 2011, while the opposite has occurred over the Gulf Stream region over the same time period. During the altimeter period the observed 0-700 m ocean heat content (OHC) in the subpolar gyre mirrors the increased SSH by its dominantly positive trend. Over a longer period, 1955-2011, fluctuations in the subpolar OHC reflect Atlantic multidecadal variability (AMV) and can be attributed to advection driven by the wind stress ''gyre mode'' bringing more subtropical waters into the subpolar gyre. The extended subpolar warming evident in SSH and OHC during the altimeter period represents transition of the AMV from cold to warm phase. In addition to the dominant trend, the first empirical orthogonal function SSH time series shows an abrupt change 2009-2010 reaching a new minimum in 2010. The change coincides with the change in the meridional overturning circulation at 26.5N as observed by the RAPID (Rapid Climate Change) project, and with extreme behavior of the wind stress gyre mode and of atmospheric blocking. While the general relationship between northern warming and Atlantic meridional overturning circulation (AMOC) volume transport remains undetermined, the meridional heat and salt transport carried by AMOC's arteries are rich with decade-to-century timescale variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSME24E0754M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSME24E0754M">Decadal to centennial oscillations in the upper and lower boundaries of the San Diego, California margin Oxygen Minimum Zone</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Myhre, S. E.; Hill, T. M.; Frieder, C.; Grupe, B. 2016-02-01 Here we present two new marine sediment archives from the continental margin of San Diego, California, USA, which record decadal to centennial oscillations in the hydrographic structure of the Eastern Pacific Oxygen Minimum Zone (OMZ). The two cores, located at 528 and 1,180 m water depth, record oceanographic history across overlapping timescales. Biotic communities, including Foraminifera, Echinodermata, Brachiopoda, Mollusca and Ostrocoda, were examined in subsurface (>10 cm sediment core depth) samples. Chronologies for both cores were developed with reservoir-corrected 14C dates of mixed planktonic Foraminifera and linearly interpolated sedimentation rates. Sediment ages for the cores range from 400-1,800 years before present. Indices of foraminiferal community density, diversity and evenness are applied as biotic proxies to track the intensification of the continental margin OMZ. Biotic communities at the shallower site reveal multi-decadal to centennial timescales of OMZ intensification, whereas the deeper site exhibits decadal to multi-decadal scales of hydrographic variability. Hypoxia-associated foraminiferal genera Uvigerina and Bolivina were compositionally dominant during intervals of peak foraminiferal density. Invertebrate assemblages often co-occurred across taxa groups, and thereby provide a broad trophic context for interpreting changes in the margin seafloor. Variability in the advection of Pacific Equatorial Water may mechanistically contribute to this described hydrographic variability. This investigation reconstructs historical timescales of OMZ intensification, seafloor ecological variability, and synchrony between open-ocean processes and regional climate. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoRL..39.4707N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoRL..39.4707N">Hydroclimate of the northeastern United States is highly sensitive to solar forcing</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nichols, Jonathan E.; Huang, Yongsong 2012-02-01 Dramatic hydrological fluctuations strongly impact human society, but the driving mechanisms for these changes are unclear. One suggested driver is solar variability, but supporting paleoclimate evidence is lacking. Therefore, long, continuous, high-resolution records from strategic locations are crucial for resolving the scientific debate regarding sensitivity of climate to solar forcing. We present a 6800-year, decadally-resolved biomarker and multidecadally-resolved hydrogen isotope record of hydroclimate from a coastal Maine peatland, The Great Heath (TGH). Regional moisture balance responds strongly and consistently to solar forcing at centennial to millennial timescales, with solar minima concurrent with wet conditions. We propose that the Arctic/North Atlantic Oscillation (AO/NAO) can amplify small solar fluctuations, producing the reconstructed hydrological variations. The Sun may be entering a weak phase, analogous to the Maunder minimum, which could lead to more frequent flooding in the northeastern US at this multidecadal timescale. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26472908','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26472908">The Atlantic Multidecadal Oscillation without a role for ocean circulation.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Clement, Amy; Bellomo, Katinka; Murphy, Lisa N; Cane, Mark A; Mauritsen, Thorsten; Rädel, Gaby; Stevens, Bjorn 2015-10-16 The Atlantic Multidecadal Oscillation (AMO) is a major mode of climate variability with important societal impacts. Most previous explanations identify the driver of the AMO as the ocean circulation, specifically the Atlantic Meridional Overturning Circulation (AMOC). Here we show that the main features of the observed AMO are reproduced in models where the ocean heat transport is prescribed and thus cannot be the driver. Allowing the ocean circulation to interact with the atmosphere does not significantly alter the characteristics of the AMO in the current generation of climate models. These results suggest that the AMO is the response to stochastic forcing from the mid-latitude atmospheric circulation, with thermal coupling playing a role in the tropics. In this view, the AMOC and other ocean circulation changes would be largely a response to, not a cause of, the AMO. Copyright © 2015, American Association for the Advancement of Science. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.2679M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.2679M">Multidecadal Changes and Interannual Variation in Springtime Phenology of North American Temperate and Boreal Deciduous Forests</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Melaas, Eli K.; Sulla-Menashe, Damien; Friedl, Mark A. 2018-03-01 The timing of leaf emergence is an important diagnostic of climate change impacts on ecosystems. Here we present the first continental-scale analysis of multidecadal changes in the timing of spring onset across North American temperate and boreal forests based on Landsat imagery. Our results show that leaf emergence in Eastern Temperate Forests has consistently trended earlier, with a median change of about 1 week over the 30 year study period. Changes in leaf emergence dates in boreal forests were more heterogeneous, with some sites showing trends toward later dates. Interannual variability in leaf emergence dates was strongly sensitive to springtime accumulated growing degree days across all sites, and geographic patterns of changes in onset dates were highly correlated with changes in regional springtime temperatures. These results provide a refined characterization of recent changes in springtime forest phenology and improve understanding regarding the sensitivity of North American forests to climate change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70031051','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70031051">Climate variability controls on unsaturated water and chemical movement, High Plains aquifer, USA</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Gurdak, J.J.; Hanson, R.T.; McMahon, P.B.; Bruce, B.W.; McCray, J.E.; Thyne, G.D.; Reedy, R.C. 2007-01-01 Responses in the vadose zone and groundwater to interannual, interdecadal, and multidecadal climate variability have important implications for groundwater resource sustainability, yet they are poorly documented and not well understood in most aquifers of the USA. This investigation systematically examines the role of interannual to multidecadal climate variability on groundwater levels, deep infiltration (3-23 m) events, and downward displacement (>1 m) of chloride and nitrate reservoirs in thick (15-50 m) vadose zones across the regionally extensive High Plains aquifer. Such vadose zone responses are unexpected across much of the aquifer given a priori that unsaturated total-potential profiles indicate upward water movement from the water table toward the root zone, mean annual potential evapotranspiration exceeds mean annual precipitation, and millennia-scale evapoconcentration results in substantial vadose zone chloride and nitrate reservoirs. Using singular spectrum analysis (SSA) to reconstruct precipitation and groundwater level time-series components, variability was identified in all time series as partially coincident with known climate cycles, such as the Pacific Decadal Oscillation (PDO) (10-25 yr) and the El Nin??o/Southern Oscillation (ENSO) (2-6 yr). Using these lag-correlated hydrologic time series, a new method is demonstrated to estimate climate-varying unsaturated water flux. The results suggest the importance of interannual to interdecadal climate variability on water-flux estimation in thick vadose zones and provide better understanding of the climate-induced transients responsible for the observed deep infiltration and chemical-mobilization events. Based on these results, we discuss implications for climate-related sustainability of the High Plains aquifer. ?? Soil Science Society of America. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611711W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611711W">Influence of climate variability versus change at multi-decadal time scales on hydrological extremes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Willems, Patrick 2014-05-01 Recent studies have shown that rainfall and hydrological extremes do not randomly occur in time, but are subject to multidecadal oscillations. In addition to these oscillations, there are temporal trends due to climate change. Design statistics, such as intensity-duration-frequency (IDF) for extreme rainfall or flow-duration-frequency (QDF) relationships, are affected by both types of temporal changes (short term and long term). This presentation discusses these changes, how they influence water engineering design and decision making, and how this influence can be assessed and taken into account in practice. The multidecadal oscillations in rainfall and hydrological extremes were studied based on a technique for the identification and analysis of changes in extreme quantiles. The statistical significance of the oscillations was evaluated by means of a non-parametric bootstrapping method. Oscillations in large scale atmospheric circulation were identified as the main drivers for the temporal oscillations in rainfall and hydrological extremes. They also explain why spatial phase shifts (e.g. north-south variations in Europe) exist between the oscillation highs and lows. Next to the multidecadal climate oscillations, several stations show trends during the most recent decades, which may be attributed to climate change as a result of anthropogenic global warming. Such attribution to anthropogenic global warming is, however, uncertain. It can be done based on simulation results with climate models, but it is shown that the climate model results are too uncertain to enable a clear attribution. Water engineering design statistics, such as extreme rainfall IDF or peak or low flow QDF statistics, obviously are influenced by these temporal variations (oscillations, trends). It is shown in the paper, based on the Brussels 10-minutes rainfall data, that rainfall design values may be about 20% biased or different when based on short rainfall series of 10 to 15 years length, and still 8% for series of 25 years lengths. Methods for bias correction are demonstrated. The definition of "bias" depends on a number of factors, which needs further debate in the hydrological and water engineering community. References: Willems P. (2013), 'Multidecadal oscillatory behaviour of rainfall extremes in Europe', Climatic Change, 120(4), 931-944 Willems, P. (2013). 'Adjustment of extreme rainfall statistics accounting for multidecadal climate oscillations', Journal of Hydrology, 490, 126-133 Willems, P., Olsson, J., Arnbjerg-Nielsen, K., Beecham, S., Pathirana, A., Bülow Gregersen, I., Madsen, H., Nguyen, V-T-V. (2012), 'Impacts of climate change on rainfall extremes and urban drainage', IWA Publishing, 252p., Paperback Print ISBN 9781780401256; Ebook ISBN 9781780401263 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP41C2272A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP41C2272A">Modest Little Ice Age cooling of the Western Tropical Atlantic inferred from Sr-U Coral Paleothermometry</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Alpert, A.; Cohen, A. L.; Oppo, D.; Gaetani, G. A. 2016-12-01 Proxy records of the Little Ice Age (LIA; 1450-1850CE) at high latitude Northern Hemisphere indicate temperatures 1-2°C cooler relative to the mid-20th century. However, estimates of sea surface temperatures (SSTs) from the western tropical Atlantic (WTA) range widely, indicating SSTs from 0- 4°C cooler than the mid-20th century. The largest of these cooling estimates indicate that the LIA tropics were more sensitive than the high latitudes, inconsistent with model predictions. Here we apply a novel coral thermometer, Sr-U, that has been demonstrated to accurately capture spatial and temporal variability across coral genera in both the Pacific and Atlantic Oceans. A continuous section of reconstructed SSTs in the WTA (Puerto Rico) during the LIA (1465-1560CE) reveals a modest cooling relative to the late 20th century but no significant difference from the early 20th century prior. At this site sensitive to the modern Atlantic Multidecadal Oscillation (AMO) multidecadal variability was present during the LIA with amplitude comparable to the 20th century. Our record is consistent with weaker tropical sensitivity to external forcing than at higher latitudes during the LIA. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040075030&hterms=TOM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTOM','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040075030&hterms=TOM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTOM">Evaluation of a Multi-Decadal Simulation of Stratospheric Ozone by Comparison with Total Ozone Mapping Spectrometer (TOMS) Observations</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Douglass, Anne R.; Stolarski, Richard S.; Steenrod, Steven; Pawson, Steven 2003-01-01 One key application of atmospheric chemistry and transport models is prediction of the response of ozone and other constituents to various natural and anthropogenic perturbations. These include changes in composition, such as the previous rise and recent decline in emission of man-made chlorofluorcarbons, changes in aerosol loading due to volcanic eruption, and changes in solar forcing. Comparisons of hindcast model results for the past few decades with observations are a key element of model evaluation and provide a sense of the reliability of model predictions. The 25 year data set from Total Ozone Mapping Spectrometers is a cornerstone of such model evaluation. Here we report evaluation of three-dimensional multi-decadal simulation of stratospheric composition. Meteorological fields for this off-line calculation are taken from a 50 year simulation of a general circulation model. Model fields are compared with observations from TOMS and also with observations from the Stratospheric Aerosol and Gas Experiment (SAGE), Microwave Limb Sounder (MLS), Cryogenic Limb Array Etalon Spectrometer (CLAES), and the Halogen Occultation Experiment (HALOE). This overall evaluation will emphasize the spatial, seasonal, and interannual variability of the simulation compared with observed atmospheric variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22498628','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22498628">Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Booth, Ben B B; Dunstone, Nick J; Halloran, Paul R; Andrews, Timothy; Bellouin, Nicolas 2012-04-04 Systematic climate shifts have been linked to multidecadal variability in observed sea surface temperatures in the North Atlantic Ocean. These links are extensive, influencing a range of climate processes such as hurricane activity and African Sahel and Amazonian droughts. The variability is distinct from historical global-mean temperature changes and is commonly attributed to natural ocean oscillations. A number of studies have provided evidence that aerosols can influence long-term changes in sea surface temperatures, but climate models have so far failed to reproduce these interactions and the role of aerosols in decadal variability remains unclear. Here we use a state-of-the-art Earth system climate model to show that aerosol emissions and periods of volcanic activity explain 76 per cent of the simulated multidecadal variance in detrended 1860-2005 North Atlantic sea surface temperatures. After 1950, simulated variability is within observational estimates; our estimates for 1910-1940 capture twice the warming of previous generation models but do not explain the entire observed trend. Other processes, such as ocean circulation, may also have contributed to variability in the early twentieth century. Mechanistically, we find that inclusion of aerosol-cloud microphysical effects, which were included in few previous multimodel ensembles, dominates the magnitude (80 per cent) and the spatial pattern of the total surface aerosol forcing in the North Atlantic. Our findings suggest that anthropogenic aerosol emissions influenced a range of societally important historical climate events such as peaks in hurricane activity and Sahel drought. Decadal-scale model predictions of regional Atlantic climate will probably be improved by incorporating aerosol-cloud microphysical interactions and estimates of future concentrations of aerosols, emissions of which are directly addressable by policy actions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611943C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611943C">The impact of large-scale circulation patterns on summer crop yields in IP</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Capa Morocho, Mirian; Rodríguez Fonseca, Belén; Ruiz Ramos, Margarita 2014-05-01 Large-scale circulations patterns (ENSO, NAO) have been shown to have a significant impact on seasonal weather, and therefore on crop yield over many parts of the world(Garnett and Khandekar, 1992; Aasa et al., 2004; Rozas and Garcia-Gonzalez, 2012). In this study, we analyze the influence of large-scale circulation patterns and regional climate on the principal components of maize yield variability in Iberian Peninsula (IP) using reanalysis datasets. Additionally, we investigate the modulation of these relationships by multidecadal patterns. This study is performed analyzing long time series of maize yield, only climate dependent, computed with the crop model CERES-maize (Jones and Kiniry, 1986) included in Decision Support System for Agrotechnology Transfer (DSSAT v.4.5). To simulate yields, reanalysis daily data of radiation, maximum and minimum temperature and precipitation were used. The reanalysis climate data were obtained from National Center for Environmental Prediction (20th Century and NCEP) and European Centre for Medium-Range Weather Forecasts (ECMWF) data server (ERA 40 and ERA Interim). Simulations were run at five locations: Lugo (northwestern), Lerida (NE), Madrid (central), Albacete (southeastern) and Córdoba (S IP) (Gabaldón et al., 2013). From these time series standardized anomalies were calculated. Afterwards, time series were time filtered to focus on the interannual-to-multiannual variability, splitting up in two components: low frequency (LF) and high frequency (HF) time scales. The principal components of HF yield anomalies in IP were compared with a set of documented patterns. These relationships were compared with multidecadal patterns, as Atlanctic Multidecadal Oscillations (AMO) and Interdecadal Pacific Oscillations (IPO). The results of this study have important implications in crop forecasting. In this way, it may have a positive impact on both public (agricultural planning) and private (decision support to farmers, insurance companies) sectors, to take advantage of favorable conditions or reduce the effect of adverse conditions. Acknowledgements Research by M. Capa-Morocho has been partly supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM) and MULCLIVAR project (CGL2012-38923-C02-02) References Aasa, A., Jaagus, J., Ahas, R. and Sepp, M. 2004. The influence of atmospheric circulation on plant phenological phases in central and eastern Europe. International Journal of Climatology 24, 1551-1564. Gabaldón, C. et al. 2013. Evaluation of local strategies to climate change of maize crop in Andalusia for the first half of 21st century. European Geosciences Union - General Assembly2013 Vol. 15 (Vienna - Austria, 2013). Garnett, E. R. and Khandekar, M. L. 1992. The impact of large-scale atmospheric circulations and anomalies on Indian monsoon droughts and floods and on world grain yields-a statistical analysis. Agricultural and Forest Meteorology 61, 113-128. Jones, C. and Kiniry, J. 1986. CERES-Maize: A Simulation Model of Maize Growth and Development. Texas A&M University Press, 194. Rozas, V. and Garcia-Gonzalez, I. 2012. Non-stationary influence of El Nino-Southern Oscillation and winter temperature on oak latewood growth in NW Iberian Peninsula. Int J Biometeorol 56, 787-800. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70162514','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70162514">Interannual to multidecadal climate forcings on groundwater resources of the U.S. West Coast</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Velasco, Elzie M.; Gurdak, Jason J.; Dickinson, Jesse; Ferré, T.P.A.; Corona, Claudia 2017-01-01 Study regionThe U.S. West Coast, including the Pacific Northwest and California Coastal Basins aquifer systems.Study focusGroundwater response to interannual to multidecadal climate variability has important implications for security within the water–energy–food nexus. Here we use Singular Spectrum Analysis to quantify the teleconnections between AMO, PDO, ENSO, and PNA and precipitation and groundwater level fluctuations. The computer program DAMP was used to provide insight on the influence of soil texture, depth to water, and mean and period of a surface infiltration flux on the damping of climate signals in the vadose zone.New hydrological insights for the regionWe find that PDO, ENSO, and PNA have significant influence on precipitation and groundwater fluctuations across a north-south gradient of the West Coast, but the lower frequency climate modes (PDO) have a greater influence on hydrologic patterns than higher frequency climate modes (ENSO and PNA). Low frequency signals tend to be preserved better in groundwater fluctuations than high frequency signals, which is a function of the degree of damping of surface variable fluxes related to soil texture, depth to water, mean and period of the infiltration flux. The teleconnection patterns that exist in surface hydrologic processes are not necessarily the same as those preserved in subsurface processes, which are affected by damping of some climate variability signals within infiltrating water. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006E%26PSL.242..143L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006E%26PSL.242..143L">Oscillations in land surface hydrological cycle</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Labat, D. 2006-02-01 Hydrological cycle is the perpetual movement of water throughout the various component of the global Earth's system. Focusing on the land surface component of this cycle, the determination of the succession of dry and humid periods is of high importance with respect to water resources management but also with respect to global geochemical cycles. This knowledge requires a specified estimation of recent fluctuations of the land surface cycle at continental and global scales. Our approach leans towards a new estimation of freshwater discharge to oceans from 1875 to 1994 as recently proposed by Labat et al. [Labat, D., Goddéris, Y., Probst, JL, Guyot, JL, 2004. Evidence for global runoff increase related to climate warming. Advances in Water Resources, 631-642]. Wavelet analyses of the annual freshwater discharge time series reveal an intermittent multiannual variability (4- to 8-y, 14- to 16-y and 20- to 25-y fluctuations) and a persistent multidecadal 30- to 40-y variability. Continent by continent, reasonable relationships between land-water cycle oscillations and climate forcing (such as ENSO, NAO or sea surface temperature) are proposed even though if such relationships or correlations remain very complex. The high intermittency of interannual oscillations and the existence of persistent multidecadal fluctuations make prediction difficult for medium-term variability of droughts and high-flows, but lead to a more optimistic diagnostic for long-term fluctuations prediction. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP42A..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP42A..04M">Climatic and anthropogenic controls on Mississippi River floods: a multi-proxy palaeoflood approach</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Munoz, S. E.; Therrell, M. D.; Remo, J. W.; Giosan, L.; Donnelly, J. P. 2017-12-01 Over the last century, many of the world's major rivers have been modified for the purposes of flood mitigation, power generation, and commercial navigation. Engineering modifications to the Mississippi River system have altered the river's sediment budget and channel morphology, but the influence of these modifications on flood risk is debated. Detecting and attributing changes in river discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability prior to the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood risk on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Niño-Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO), but that artificial channelization has greatly amplified flood magnitudes over the last century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the last five hundred years that combines sedimentary, tree-ring, and instrumental records, reveal that the magnitude of the 100-year flood has increased by 20% over the period of record, with 75% of this increase attributed to river engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood risk to levels that are unprecedented within the last five centuries. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/biblio/588604-greenhouse-warming-decadal-variability-el-nino-attempt-understand-anomalous','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/588604-greenhouse-warming-decadal-variability-el-nino-attempt-understand-anomalous">Greenhouse warming, decadal variability, or El Nino? An attempt to understand the anomalous 1990s</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Latif, M.; Eckert, C.; Kleeman, R. The dominant variability modes in the Tropics are investigated and contrasted with the anomalous situation observed during the last few years. The prime quantity analyzed is anomalous sea surface temperature (SST) in the region 30{degrees}S-60{degrees}N. Additionally, observed tropical surface wind stress fields were investigated. Further tropical atmospheric information was derived from a multidecadal run with an atmospheric general circulation model that was forced by the same SSTs. The tropical SST variability can be characterized by three modes: an interannual mode [the El Nino-Southern Oscillation (ENSO)], a decadal mode, and a trend or unresolved ultra-low-frequency variability. 48 refs., 20 figs. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGC22A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGC22A..06S">Is Global Warming Accelerating?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shukla, J.; Delsole, T. M.; Tippett, M. K. 2009-12-01 A global pattern that fluctuates naturally on decadal time scales is identified in climate simulations and observations. This newly discovered component, called the Global Multidecadal Oscillation (GMO), is related to the Atlantic Meridional Oscillation and shown to account for a substantial fraction of decadal fluctuations in the observed global average sea surface temperature. IPCC-class climate models generally underestimate the variance of the GMO, and hence underestimate the decadal fluctuations due to this component of natural variability. Decomposing observed sea surface temperature into a component due to anthropogenic and natural radiative forcing plus the GMO, reveals that most multidecadal fluctuations in the observed global average sea surface temperature can be accounted for by these two components alone. The fact that the GMO varies naturally on multidecadal time scales implies that it can be predicted with some skill on decadal time scales, which provides a scientific rationale for decadal predictions. Furthermore, the GMO is shown to account for about half of the warming in the last 25 years and hence a substantial fraction of the recent acceleration in the rate of increase in global average sea surface temperature. Nevertheless, in terms of the global average “well-observed” sea surface temperature, the GMO can account for only about 0.1° C in transient, decadal-scale fluctuations, not the century-long 1° C warming that has been observed during the twentieth century. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/31786','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/31786">Response of Subalpine Conifers in the Sierra Nevada, California, U.S.A., to 20th-Century Warming and Decadal Climate Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Constance I. Millar; Robert D. Westfall; Diane L. Delany; John C. King; Lisa J. Graumlich 2004-01-01 Four independent studies of conifer growth between 1880 and 2002 in upper elevation forests of the central Sierra Nevada, California, U.S.A., showed correlated multidecadal and century-long responses associated with climate. Using tree-ring and ecological plot analysis, we studied annual branch growth of krummholz Pinus albicaulis; invasion by P.... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513897W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513897W">Multidecadal oscillations in rainfall and hydrological extremes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Willems, Patrick 2013-04-01 Many studies have anticipated a worldwide increase in the frequency and intensity of precipitation extremes and floods since the last decade(s). Natural variability by climate oscillations partly determines the observed evolution of precipitation extremes. Based on a technique for the identification and analysis of changes in extreme quantiles, it is shown that hydrological extremes have oscillatory behaviour at multidecadal time scales. Results are based on nearly independent extremes extracted from long-term historical time series of precipitation intensities and river flows. Study regions include Belgium - The Netherlands (Meuse basin), Ethiopia (Blue Nile basin) and Ecuador (Paute basin). For Belgium - The Netherlands, the past 100 years showed larger and more hydrological extremes around the 1910s, 1950-1960s, and more recently during the 1990-2000s. Interestingly, the oscillations for southwestern Europe are anti-correlated with these of northwestern Europe, thus with oscillation highs in the 1930-1940s and 1970s. The precipitation oscillation peaks are explained by persistence in atmospheric circulation patterns over the North Atlantic during periods of 10 to 15 years. References: Ntegeka V., Willems P. (2008), 'Trends and multidecadal oscillations in rainfall extremes, based on a more than 100 years time series of 10 minutes rainfall intensities at Uccle, Belgium', Water Resources Research, 44, W07402, doi:10.1029/2007WR006471 Mora, D., Willems, P. (2012), 'Decadal oscillations in rainfall and air temperature in the Paute River Basin - Southern Andes of Ecuador', Theoretical and Applied Climatology, 108(1), 267-282, doi:0.1007/s00704-011-0527-4 Taye, M.T., Willems, P. (2011). 'Influence of climate variability on representative QDF predictions of the upper Blue Nile Basin', Journal of Hydrology, 411, 355-365, doi:10.1016/j.jhydrol.2011.10.019 Taye, M.T., Willems, P. (2012). 'Temporal variability of hydro-climatic extremes in the Blue Nile basin', Water Resources Research, 48, W03513, 13p. Willems, P., Olsson, J., Arnbjerg-Nielsen, K., Beecham, S., Pathirana, A., Bülow Gregersen, I., Madsen, H., Nguyen, V-T-V. (2012), 'Impacts of climate change on rainfall extremes and urban drainage', IWA Publishing, 252p., Paperback Print ISBN 9781780401256; Ebook ISBN 9781780401263 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613612K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613612K">Multi-decadal Variability of the Wind Power Output</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kirchner Bossi, Nicolas; García-Herrera, Ricardo; Prieto, Luis; Trigo, Ricardo M. 2014-05-01 The knowledge of the long-term wind power variability is essential to provide a realistic outlook on the power output during the lifetime of a planned wind power project. In this work, the Power Output (Po) of a market wind turbine is simulated with a daily resolution for the period 1871-2009 at two different locations in Spain, one at the Central Iberian Plateau and another at the Gibraltar Strait Area. This is attained through a statistical downscaling of the daily wind conditions. It implements a Greedy Algorithm as classificator of a geostrophic-based wind predictor, which is derived by considering the SLP daily field from the 56 ensemble members of the longest homogeneous reanalysis available (20CR, 1871-2009). For calibration and validation purposes we use 10 years of wind observations (the predictand) at both sites. As a result, a series of 139 annual wind speed Probability Density Functions (PDF) are obtained, with a good performance in terms of wind speed uncertainty reduction (average daily wind speed MAE=1.48 m/s). The obtained centennial series allow to investigate the multi-decadal variability of wind power from different points of view. Significant periodicities around the 25-yr frequency band, as well as long-term linear trends are detected at both locations. In addition, a negative correlation is found between annual Po at both locations, evidencing the differences in the dynamical mechanisms ruling them (and possible complementary behavior). Furthermore, the impact that the three leading large-scale circulation patterns over Iberia (NAO, EA and SCAND) exert over wind power output is evaluated. Results show distinct (and non-stationary) couplings to these forcings depending on the geographical position and season or month. Moreover, significant non-stationary correlations are observed with the slow varying Atlantic Multidecadal Oscillation (AMO) index for both case studies. Finally, an empirical relationship is explored between the annual Po and the parameters of the Weibull PDF. This allowed us to derive a linear model to estimate the annual power output from those parameters, which results especially useful when no wind power data is available. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A51V..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A51V..07S">Spatial patterns of Antarctic surface temperature trends in the context of natural variability: Lessons from the CMIP5 Models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Smith, K. L.; Polvani, L. M. 2015-12-01 The recent annually averaged warming of the Antarctic Peninsula, and of West Antarctica, stands in stark contrast to very small and weakly negative trends over East Antarctica. This asymmetry arises primarily from a highly significant warming of West Antarctica in austral spring and a strong cooling of East Antarctic in austral autumn. Here we examine whether this East-West asymmetry is a response to anthropogenic climate forcings or a manifestation of natural climate variability. We compare the observed Antarctic surface air temperature (SAT) trends from five temperature reconstructions over two distinct time periods (1979-2005 and 1960-2005), and with those simulated by 40 coupled models participating in Phase 5 of the Coupled Model Intercomparison Project. We find that the observed East-West asymmetry differs substantially over the two time periods and, furthermore, is completely absent from the CMIP5 multi-model mean (from which all natural variability is eliminated by the averaging). We compare the CMIP5 SAT trends to those of 29 historical atmosphere-only simulations with prescribed sea surface temperatures (SSTs) and sea ice and find that these simulations are in better agreement with the observations. This suggests that natural multi-decadal variability associated with SSTs and sea ice and not external forcings is the primary driver of Antarctic SAT trends. We confirm this by showing that the observed trends lie within the distribution of multi-decadal trends from the CMIP5 pre-industrial integrations. These results, therefore, offer new evidence which points to natural climate variability as the more likely cause of the recent warming of West Antarctica and of the Peninsula. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.132...68Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.132...68Y">The role of the Atlantic Water in multidecadal ocean variability in the Nordic and Barents Seas</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yashayaev, Igor; Seidov, Dan 2015-03-01 The focus of this work is on the temporal and spatial variability of the Atlantic Water (AW). We analyze the existing historic hydrographic data from the World Ocean Database to document the long-term variability of the AW throughflow across the Norwegian Sea to the western Barents Sea. Interannual-to-multidecadal variability of water temperature, salinity and density are analyzed along six composite sections crossing the AW flow and coastal currents at six selected locations. The stations are lined up from southwest to northeast - from the northern North Sea (69°N) throughout the Norwegian Sea to the Kola Section in the Barents Sea (33°30‧E). The changing volume and characteristics of the AW throughflow dominate the hydrographic variability on decadal and longer time scales in the studied area. We examine the role of fluctuations of the volume of inflow versus the variable local factors, such as the air-sea interaction and mixing with the fresh coastal and cold Arctic waters, in controlling the long-term regional variability. It is shown that the volume of the AW, passing through the area and affecting the position of the outer edge of the warm and saline core, correlates well with temperature and salinity averaged over the central portions of the studied sections. The coastal flow (mostly associated with the Norwegian Coastal Current flowing over the continental shelf) is largely controlled by seasonal local heat and freshwater impacts. Temperature records at all six lines show a warming trend superimposed on a series of relatively warm and cold periods, which in most cases follow, with a delay of four to five years, the periods of relatively low and high North Atlantic Oscillation (NAO), and the periods of relatively high and low Atlantic Multidecadal Oscillation (AMO), respectively. In general, there is a relatively high correlation between the year-to-year changes of the NAO and AMO indices, which is to some extent reflected in the (delayed) AW temperature fluctuations. It takes about two years for freshening and salinification events and a much shorter time (of about a year or less) for cooling and warming episodes to propagate or spread across the region. This significant difference in the propagation rates of salinity and temperature anomalies is explained by the leading role of horizontal advection in the propagation of salinity anomalies, whereas temperature is also controlled by the competing air-sea interaction along the AW throughflow. Therefore, although a water parcel moves within the flow as a whole, the temperature, salinity and density anomalies split and propagate separately, with the temperature and density signals leading relative to the salinity signal. A new hydrographic index, coastal-to-offshore density step, is introduced to capture variability in the strength of the AW volume transport. This index shows the same cycles of variability as observed in temperature, NAO and AMO but without an obvious trend. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41E..05D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41E..05D">Multi-Decadal Averages of Basal Melt for Ross Ice Shelf, Antarctica Using Airborne Observations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Das, I.; Bell, R. E.; Tinto, K. J.; Frearson, N.; Kingslake, J.; Padman, L.; Siddoway, C. S.; Fricker, H. A. 2017-12-01 Changes in ice shelf mass balance are key to the long term stability of the Antarctic Ice Sheet. Although the most extensive ice shelf mass loss currently is occurring in the Amundsen Sea sector of West Antarctica, many other ice shelves experience changes in thickness on time scales from annual to ice age cycles. Here, we focus on the Ross Ice Shelf. An 18-year record (1994-2012) of satellite radar altimetry shows substantial variability in Ross Ice Shelf height on interannual time scales, complicating detection of potential long-term climate-change signals in the mass budget of this ice shelf. Variability of radar signal penetration into the ice-shelf surface snow and firn layers further complicates assessment of mass changes. We investigate Ross Ice Shelf mass balance using aerogeophysical data from the ROSETTA-Ice surveys using IcePod. We use two ice-penetrating radars; a 2 GHz unit that images fine-structure in the upper 400 m of the ice surface and a 360 MHz radar to identify the ice shelf base. We have identified internal layers that are continuous along flow from the grounding line to the ice shelf front. Based on layer continuity, we conclude that these layers must be the horizons between the continental ice of the outlet glaciers and snow accumulation once the ice is afloat. We use the Lagrangian change in thickness of these layers, after correcting for strain rates derived using modern day InSAR velocities, to estimate multidecadal averaged basal melt rates. This method provides a novel way to quantify basal melt, avoiding the confounding impacts of spatial and short-timescale variability in surface accumulation and firn densification processes. Our estimates show elevated basal melt rates (> -1m/yr) around Byrd and Mullock glaciers within 100 km from the ice shelf front. We also compare modern InSAR velocity derived strain rates with estimates from the comprehensive ground-based RIGGS observations during 1973-1978 to estimate the potential magnitude of strain-driven thickness changes over four decades. Combining maps of basal melt rate with radar derived basal reflectivity, we identify regions that are undergoing melting and freezing and provide a comprehensive understanding of how ocean processes may be changing the base of Ross Ice Shelf in recent decades. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1378474','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1378474">AMOC decadal variability in Earth system models: Mechanisms and climate impacts</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fedorov, Alexey This is the final report for the project titled "AMOC decadal variability in Earth system models: Mechanisms and climate impacts". The central goal of this one-year research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) within a hierarchy of climate models ranging from realistic ocean GCMs to Earth system models. The AMOC is a key element of ocean circulation responsible for oceanic transport of heat from low to high latitudes and controlling, to a large extent, climate variations in the North Atlantic. The questions of the AMOC stability, variability andmore » predictability, directly relevant to the questions of climate predictability, were at the center of the research work.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1167250','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1167250">A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for Decadal Variability and Abrupt Climate Change</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fedorov, Alexey V. 2015-01-14 The central goal of this research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate variability and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC variability to the factors that determine AMOC predictability in the Earth systemmore » models, to the stability and variability of the AMOC in past climates.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24451542','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24451542">Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun 2014-01-23 In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911342R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911342R">Hydroclimatic variability in the Lake Mondsee region and its relationships with large-scale climate anomaly patterns</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rimbu, Norel; Ionita, Monica; Swierczynski, Tina; Brauer, Achim; Kämpf, Lucas; Czymzik, Markus 2017-04-01 Flood triggered detrital layers in varved sediments of Lake Mondsee, located at the northern fringe of the European Alps (47°48'N,13°23'E), provide an important archive of regional hydroclimatic variability during the mid- to late Holocene. To improve the interpretation of the flood layer record in terms of large-scale climate variability, we investigate the relationships between observational hydrological records from the region, like the Mondsee lake level, the runoff of the lake's main inflow Griesler Ache, with observed precipitation and global climate patterns. The lake level shows a strong positive linear trend during the observational period in all seasons. Additionally, lake level presents important interannual to multidecadal variations. These variations are associated with distinct seasonal atmospheric circulation patterns. A pronounced anomalous anticyclonic center over the Iberian Peninsula is associated with high lake levels values during winter. This center moves southwestward during spring, summer and autumn. In the same time, a cyclonic anomaly center is recorded over central and western Europe. This anomalous circulation extends southwestward from winter to autumn. Similar atmospheric circulation patterns are associated with river runoff and precipitation variability from the region. High lake levels are associated with positive local precipitation anomalies in all seasons as well as with negative local temperature anomalies during spring, summer and autumn. A correlation analysis reveals that lake level, runoff and precipitation variability is related to large-scale sea surface temperature anomaly patterns in all seasons suggesting a possible impact of large-scale climatic modes, like the North Atlantic Oscillation and Atlantic Multidecadal Oscillation on hydroclimatic variability in the Lake Mondsee region. The results presented in this study can be used for a more robust interpretation of the long flood layer record from Lake Mondsee sediments in terms of regional and large-scale climate variability during the past. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4646T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4646T">Analysis of Sea Level Rise in Singapore Strait</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tkalich, Pavel; Luu, Quang-Hung 2013-04-01 Sea level in Singapore Strait is governed by various scale phenomena, from global to local. Global signals are dominated by the climate change and multi-decadal variability and associated sea level rise; at regional scale seasonal sea level variability is caused by ENSO-modulated monsoons; locally, astronomic tides are the strongest force. Tide gauge records in Singapore Strait are analyzed to derive local sea level trend, and attempts are made to attribute observed sea level variability to phenomena at various scales, from global to local. It is found that at annual scale, sea level anomalies in Singapore Strait are quasi-periodic, of the order of ±15 cm, the highest during northeast monsoon and the lowest during southwest monsoon. Interannual regional sea level falls are associated with El Niño events, while the rises are related to La Niña episodes; both variations are in the range of ±9 cm. At multi-decadal scale, sea level in Singapore Strait has been rising at the rate 1.2-1.9 mm/year for the period 1975-2009, 2.0±0.3 mm/year for 1984-2009, and 1.3-4.7 mm/year for 1993-2009. When compared with the respective global trends of 2.0±0.3, 2.4, and 2.8±0.8 mm/year, Singapore Strait sea level rise trend was weaker at the earlier period and stronger at the recent decade. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70170127','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70170127">Tree-ring-based estimates of long-term seasonal precipitation in the Souris River Region of Saskatchewan, North Dakota and Manitoba</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ryberg, Karen R.; Vecchia, Aldo V.; Akyüz, F. Adnan; Lin, Wei 2016-01-01 Historically unprecedented flooding occurred in the Souris River Basin of Saskatchewan, North Dakota and Manitoba in 2011, during a longer term period of wet conditions in the basin. In order to develop a model of future flows, there is a need to evaluate effects of past multidecadal climate variability and/or possible climate change on precipitation. In this study, tree-ring chronologies and historical precipitation data in a four-degree buffer around the Souris River Basin were analyzed to develop regression models that can be used for predicting long-term variations of precipitation. To focus on longer term variability, 12-year moving average precipitation was modeled in five subregions (determined through cluster analysis of measures of precipitation) of the study area over three seasons (November–February, March–June and July–October). The models used multiresolution decomposition (an additive decomposition based on powers of two using a discrete wavelet transform) of tree-ring chronologies from Canada and the US and seasonal 12-year moving average precipitation based on Adjusted and Homogenized Canadian Climate Data and US Historical Climatology Network data. Results show that precipitation varies on long-term (multidecadal) time scales of 16, 32 and 64 years. Past extended pluvial and drought events, which can vary greatly with season and subregion, were highlighted by the models. Results suggest that the recent wet period may be a part of natural variability on a very long time scale. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Natur.556...95M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Natur.556...95M">Climatic control of Mississippi River flood hazard amplified by river engineering</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Munoz, Samuel E.; Giosan, Liviu; Therrell, Matthew D.; Remo, Jonathan W. F.; Shen, Zhixiong; Sullivan, Richard M.; Wiman, Charlotte; O’Donnell, Michelle; Donnelly, Jeffrey P. 2018-04-01 Over the past century, many of the world’s major rivers have been modified for the purposes of flood mitigation, power generation and commercial navigation. Engineering modifications to the Mississippi River system have altered the river’s sediment levels and channel morphology, but the influence of these modifications on flood hazard is debated. Detecting and attributing changes in river discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability before the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood hazard on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Niño–Southern Oscillation and the Atlantic Multidecadal Oscillation, but that the artificial channelization (confinement to a straightened channel) has greatly amplified flood magnitudes over the past century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the past 500 years, reveal that the magnitude of the 100-year flood (a flood with a 1 per cent chance of being exceeded in any year) has increased by 20 per cent over those five centuries, with about 75 per cent of this increase attributed to river engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood hazard to levels that are unprecedented within the past five centuries. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29620734','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29620734">Climatic control of Mississippi River flood hazard amplified by river engineering.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Munoz, Samuel E; Giosan, Liviu; Therrell, Matthew D; Remo, Jonathan W F; Shen, Zhixiong; Sullivan, Richard M; Wiman, Charlotte; O'Donnell, Michelle; Donnelly, Jeffrey P 2018-04-04 Over the past century, many of the world's major rivers have been modified for the purposes of flood mitigation, power generation and commercial navigation. Engineering modifications to the Mississippi River system have altered the river's sediment levels and channel morphology, but the influence of these modifications on flood hazard is debated. Detecting and attributing changes in river discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability before the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood hazard on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Niño-Southern Oscillation and the Atlantic Multidecadal Oscillation, but that the artificial channelization (confinement to a straightened channel) has greatly amplified flood magnitudes over the past century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the past 500 years, reveal that the magnitude of the 100-year flood (a flood with a 1 per cent chance of being exceeded in any year) has increased by 20 per cent over those five centuries, with about 75 per cent of this increase attributed to river engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood hazard to levels that are unprecedented within the past five centuries. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7439V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7439V">Downscaling and hydrological uncertainties in 20th century hydrometeorological reconstructions over France</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vidal, Jean-Philippe; Caillouet, Laurie; Dayon, Gildas; Boé, Julien; Sauquet, Eric; Thirel, Guillaume; Graff, Benjamin 2017-04-01 The record length of streamflow observations is generally limited to the last 50 years, which is not enough to properly explore the natural hydrometeorological variability, a key to better understand the effects of anthropogenic climate change. This work proposes a comparison of different hydrometeorological reconstruction datasets over France built on the downscaling of the NOAA 20th century global extended reanalysis (20CR, Compo et al., 2011). It aims at assessing the uncertainties related to these reconstructions and improving our knowledge of the multi-decadal hydrometeorological variability over the 20th century. High-resolution daily meteorological reconstructions over the period 1871-2012 are obtained with two statistical downscaling methods based on the analogue approach: the deterministic ANALOG method (Dayon et al., 2015) and the probabilistic SCOPE method (Caillouet et al., 2016). These reconstructions are then used as forcings for the GR6J lumped conceptual rainfall-runoff model and the SIM physically-based distributed hydrological model, in order to derive daily streamflow reconstructions over a set of around 70 reference near-natural catchments. Results show a large multi-decadal streamflow variability over the last 140 years, which is however relatively consistent over France. Empirical estimates of three types of uncertainty - structure of the downscaling method, small-scale internal variability, and hydrological model structure - show roughly equal contributions to the streamflow uncertainty at the annual time scale, with values as high as 20% of the interannual mean. Caillouet, L., Vidal, J.-P., Sauquet, E., and Graff, B.: Probabilistic precipitation and temperature downscaling of the Twentieth Century Reanalysis over France, Clim. Past, 12, 635-662, doi:10.5194/cp-12-635-2016, 2016. Compo, G. P., Whitaker, J. S., Sardeshmukh, P. D., Matsui, N., Allan, R. J., Yin, X., Gleason, B. E., Vose, R. S., Rutledge, G., Bessemoulin, P., Brönnimann, S., Brunet, M., Crouthamel, R. I., Grant, A. N., Groisman, P. Y., Jones, P. D., Kruk, M. C., Kruger, A. C., Marshall, G. J., Maugeri, M., Mok, H. Y., Nordli, Ø., Ross, T. F., Trigo, R. M., Wang, X. L., Woodruff, S. D., and Worley, S. J.: The Twentieth Century Reanalysis Project. Q. J. R. Meteorol. Soc., 137, 1-28, doi:10.1002/qj.776, 2011. Dayon, G., Boé, J., and Martin, E.: Transferability in the future climate of a statistical downscaling method for precipitation in France, J. Geophys. Res.-Atmos., 120, 1023-1043, doi: 10.1002/2014JD022236, 2015. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4218T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4218T">Mechanisms and Early Detections of Multidecadal Oxygen Changes in the Interior Subpolar North Atlantic</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tjiputra, J. F.; Goris, N.; Lauvset, S. K.; Heinze, C.; Olsen, A.; Schwinger, J.; Steinfeldt, R. 2018-05-01 The oxygen response in the subpolar North Atlantic (SPNA) to future climate change is poorly understood. We investigate the multidecadal variability in interior oxygen and its association with the subpolar gyre index (a gyre strength proxy) for models and data. During positive phases, persistent strong Labrador Sea (LS) lateral and vertical mixing entrains oxygen-rich water into the interior southern SPNA and vice versa during negative phases. This is indicated by the observed anomalously fresh, cold, and low apparent oxygen utilization, resembling LS water mass during positive phases. We use this relationship to benchmark Earth system models. Under a high CO2 future, the best performing models project a steady decline in SPNA oxygen, driven partly by lower solubility and increases in apparent oxygen utilization. The deoxygenation depends on the sensitivity of the LS mixing to warming. The time of emergence of interior oxygen is projected to be decades earlier than that of temperature and salinity. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29263398','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29263398">Forest productivity in southwestern Europe is controlled by coupled North Atlantic and Atlantic Multidecadal Oscillations.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Madrigal-González, Jaime; Ballesteros-Cánovas, Juan A; Herrero, Asier; Ruiz-Benito, Paloma; Stoffel, Markus; Lucas-Borja, Manuel E; Andivia, Enrique; Sancho-García, Cesar; Zavala, Miguel A 2017-12-20 The North Atlantic Oscillation (NAO) depicts annual and decadal oscillatory modes of variability responsible for dry spells over the European continent. The NAO therefore holds a great potential to evaluate the role, as carbon sinks, of water-limited forests under climate change. However, uncertainties related to inconsistent responses of long-term forest productivity to NAO have so far hampered firm conclusions on its impacts. We hypothesize that, in part, such inconsistencies might have their origin in periodical sea surface temperature anomalies in the Atlantic Ocean (i.e., Atlantic Multidecadal Oscillation, AMO). Here we show strong empirical evidence in support of this hypothesis using 120 years of periodical inventory data from Iberian pine forests. Our results point to AMO + NAO + and AMO - NAO - phases as being critical for forest productivity, likely due to decreased winter water balance and abnormally low winter temperatures, respectively. Our findings could be essential for the evaluation of ecosystem functioning vulnerabilities associated with increased climatic anomalies under unprecedented warming conditions in the Mediterranean. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4410560S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4410560S">Multidecadal Weakening of Indian Summer Monsoon Circulation Induces an Increasing Northern Indian Ocean Sea Level</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Swapna, P.; Jyoti, J.; Krishnan, R.; Sandeep, N.; Griffies, S. M. 2017-10-01 North Indian Ocean sea level has shown significant increase during last three to four decades. Analyses of long-term climate data sets and ocean model sensitivity experiments identify a mechanism for multidecadal sea level variability relative to global mean. Our results indicate that North Indian Ocean sea level rise is accompanied by a weakening summer monsoon circulation. Given that Indian Ocean meridional heat transport is primarily regulated by the annual cycle of monsoon winds, weakening of summer monsoon circulation has resulted in reduced upwelling off Arabia and Somalia and decreased southward heat transport, and corresponding increase of heat storage in the North Indian Ocean. These changes in turn lead to increased retention of heat and increased thermosteric sea level rise in the North Indian Ocean, especially in the Arabian Sea. These findings imply that rising North Indian Ocean sea level due to weakening of monsoon circulation demands adaptive strategies to enable a resilient South Asian population. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070020527&hterms=doi&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddoi%253A','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070020527&hterms=doi&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddoi%253A">Multidecadal Changes in Near-Global Cloud Cover and Estimated Cloud Cover Radiative Forcing</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Norris, Joel 2005-01-01 The first paper was Multidecadal changes in near-global cloud cover and estimated cloud cover radiative forcing, by J. R. Norris (2005, J. Geophys. Res. - Atmos., 110, D08206, doi: lO.l029/2004JD005600). This study examined variability in zonal mean surface-observed upper-level (combined midlevel and high-level) and low-level cloud cover over land during 1971-1 996 and over ocean during 1952-1997. These data were averaged from individual synoptic reports in the Extended Edited Cloud Report Archive (EECRA). Although substantial interdecadal variability is present in the time series, long-term decreases in upper-level cloud cover occur over land and ocean at low and middle latitudes in both hemispheres. Near-global upper-level cloud cover declined by 1.5%-sky-cover over land between 1971 and 1996 and by 1.3%-sky-cover over ocean between 1952 and 1997. Consistency between EECRA upper-level cloud cover anomalies and those from the International Satellite Cloud Climatology Project (ISCCP) during 1984-1 997 suggests the surface-observed trends are real. The reduction in surface-observed upper-level cloud cover between the 1980s and 1990s is also consistent with the decadal increase in all-sky outgoing longwave radiation reported by the Earth Radiation Budget Satellite (EMS). Discrepancies occur between time series of EECRA and ISCCP low-level cloud cover due to identified and probable artifacts in satellite and surface cloud data. Radiative effects of surface-observed cloud cover anomalies, called "cloud cover radiative forcing (CCRF) anomalies," are estimated based on a linear relationship to climatological cloud radiative forcing per unit cloud cover. Zonal mean estimated longwave CCRF has decreased over most of the globe. Estimated shortwave CCRF has become slightly stronger over northern midlatitude oceans and slightly weaker over northern midlatitude land areas. A long-term decline in the magnitude of estimated shortwave CCRF occurs over low-latitude land and ocean, but comparison with EMS all-sky reflected shortwave radiation during 1985-1997 suggests this decrease may be underestimated. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990102609&hterms=heiser&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dheiser','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990102609&hterms=heiser&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dheiser">Seasonal-to-Interannual Precipitation Variability and Predictability in a Coupled Land-Atmosphere System</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Koster, Randal D.; Suarez, M. J.; Heiser, M. 1998-01-01 In an earlier GCM study, we showed that interactive land surface processes generally contribute more to continental precipitation variance than do variable sea surface temperatures (SSTs). A new study extends this result through an analysis of 16-member ensembles of multi-decade GCM simulations. We can now show that in many regions, although land processes determine the amplitude of the interannual precipitation anomalies, variable SSTs nevertheless control their timing. The GCM data can be processed into indices that describe geographical variations in (1) the potential for seasonal-to-interannual prediction, and (2) the extent to which the predictability relies on the proper representation of land-atmosphere feedback. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1030607','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1030607">Towards the Prediction of Decadal to Centennial Climate Processes in the Coupled Earth System Model</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Liu, Zhengyu; Kutzbach, J.; Jacob, R. 2011-12-05 In this proposal, we have made major advances in the understanding of decadal and long term climate variability. (a) We performed a systematic study of multidecadal climate variability in FOAM-LPJ and CCSM-T31, and are starting exploring decadal variability in the IPCC AR4 models. (b) We develop several novel methods for the assessment of climate feedbacks in the observation. (c) We also developed a new initialization scheme DAI (Dynamical Analogue Initialization) for ensemble decadal prediction. (d) We also studied climate-vegetation feedback in the observation and models. (e) Finally, we started a pilot program using Ensemble Kalman Filter in CGCM for decadalmore » climate prediction.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1375428','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1375428">Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Klein, Francois; Goosse, Hugues; Graham, Nicholas E. The multi-decadal to centennial hydroclimate changes in East Africa over the last millennium are studied by comparing the results of forced transient simulations by six general circulation models (GCMs) with published hydroclimate reconstructions from four lakes: Challa and Naivasha in equatorial East Africa, and Masoko and Malawi in southeastern inter-tropical Africa. All GCMs simulate fairly well the unimodal seasonal cycle of precipitation in the Masoko–Malawi region, while the bimodal seasonal cycle characterizing the Challa–Naivasha region is generally less well captured by most models. Model results and lake-based hydroclimate reconstructions display very different temporal patterns over the last millennium. Additionally, theremore » is no common signal among the model time series, at least until 1850. This suggests that simulated hydroclimate fluctuations are mostly driven by internal variability rather than by common external forcing. After 1850, half of the models simulate a relatively clear response to forcing, but this response is different between the models. Overall, the link between precipitation and tropical sea surface temperatures (SSTs) over the pre-industrial portion of the last millennium is stronger and more robust for the Challa–Naivasha region than for the Masoko–Malawi region. At the inter-annual timescale, last-millennium Challa–Naivasha precipitation is positively (negatively) correlated with western (eastern) Indian Ocean SST, while the influence of the Pacific Ocean appears weak and unclear. Although most often not significant, the same pattern of correlations between East African rainfall and the Indian Ocean SST is still visible when using the last-millennium time series smoothed to highlight centennial variability, but only in fixed-forcing simulations. Furthermore, this means that, at the centennial timescale, the effect of (natural) climate forcing can mask the imprint of internal climate variability in large-scale teleconnections.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1375428-comparison-simulated-reconstructed-variations-east-african-hydroclimate-over-last-millennium','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1375428-comparison-simulated-reconstructed-variations-east-african-hydroclimate-over-last-millennium">Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Klein, Francois; Goosse, Hugues; Graham, Nicholas E.; ... 2016-07-13 The multi-decadal to centennial hydroclimate changes in East Africa over the last millennium are studied by comparing the results of forced transient simulations by six general circulation models (GCMs) with published hydroclimate reconstructions from four lakes: Challa and Naivasha in equatorial East Africa, and Masoko and Malawi in southeastern inter-tropical Africa. All GCMs simulate fairly well the unimodal seasonal cycle of precipitation in the Masoko–Malawi region, while the bimodal seasonal cycle characterizing the Challa–Naivasha region is generally less well captured by most models. Model results and lake-based hydroclimate reconstructions display very different temporal patterns over the last millennium. Additionally, theremore » is no common signal among the model time series, at least until 1850. This suggests that simulated hydroclimate fluctuations are mostly driven by internal variability rather than by common external forcing. After 1850, half of the models simulate a relatively clear response to forcing, but this response is different between the models. Overall, the link between precipitation and tropical sea surface temperatures (SSTs) over the pre-industrial portion of the last millennium is stronger and more robust for the Challa–Naivasha region than for the Masoko–Malawi region. At the inter-annual timescale, last-millennium Challa–Naivasha precipitation is positively (negatively) correlated with western (eastern) Indian Ocean SST, while the influence of the Pacific Ocean appears weak and unclear. Although most often not significant, the same pattern of correlations between East African rainfall and the Indian Ocean SST is still visible when using the last-millennium time series smoothed to highlight centennial variability, but only in fixed-forcing simulations. Furthermore, this means that, at the centennial timescale, the effect of (natural) climate forcing can mask the imprint of internal climate variability in large-scale teleconnections.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712560D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712560D">Exploring the control of land-atmospheric oscillations over terrestrial vegetation productivity</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Depoorter, Mathieu; Green, Julia; Gentine, Pierre; Liu, Yi; van Eck, Christel; Regnier, Pierre; Dorigo, Wouter; Verhoest, Niko; Miralles, Diego 2015-04-01 Vegetation dynamics play an important role in the climate system due to their control on the carbon, energy and water cycles. The spatiotemporal variability of vegetation is regulated by internal climate variability as well as natural and anthropogenic forcing mechanisms, including fires, land use, volcano eruptions or greenhouse gas emissions. Ocean-atmospheric oscillations, affect the fluxes of heat and water over continents, leading to anomalies in radiation, precipitation or temperature at widely separated locations (i.e. teleconnections); an effect of ocean-atmospheric oscillations on terrestrial primary productivity can therefore be expected. While different studies have shown the general importance of internal climate variability for global vegetation dynamics, the control by particular teleconnections over the regional growth and decay of vegetation is still poorly understood. At continental to global scales, satellite remote sensing offers a feasible approach to enhance our understanding of the main drivers of vegetation variability. Traditional studies of the multi-decadal variability of global vegetation have been usually based on the normalized difference vegetation index (NDVI) derived from the Advanced Very High Resolution Radiometer (AVHRR), which extends back to the early '80s. There are, however, some limitations to NDVI observations; arguably the most important of these limitations is that from the plant physiology perspective the index does not have a well-defined meaning, appearing poorly correlated to vegetation productivity. On the other hand, recently developed records from other remotely-sensed properties of vegetation, like fluorescence or microwave vegetation optical depth, have proven a significantly better correspondence to above-ground biomass. To enhance our understanding of the controls of ocean-atmosphere oscillations over vegetation, we propose to explore the link between climate oscillation extremes and net primary productivity over the last two decades. The co-variability of a range of climate oscillation indices and newly-derived records of fluorescence and vegetation optical depth is analyzed using a statistical framework based on correlations, bootstrapping and Empirical Orthogonal Functions (EOFs). Results will enable us to characterize regional hotspots where particular climatic oscillations control vegetation productivity, as well as allowing us to underpin the climatic variables behind this control. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC33H..05L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC33H..05L">The summer North Atlantic Oscillation (SNAO) variability on decadal to paleoclimate time scales</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Linderholm, H. W.; Folland, C. K.; Zhang, P.; Gunnarson, B. E.; Jeong, J. H.; Ren, H. 2017-12-01 The summer North Atlantic Oscillation (SNAO), strongly related to the latitude of the North Atlantic and European summer storm tracks, exerts a considerable influence on European summer climate variability and extremes. Here we extend the period covered by the SNAO from July and August to June, July and August (JJA). As well as marked interannual variability, the JJA SNAO has shown a large inter-decadal change since the 1970s. Decadally averaged, there has been a change from a very positive to a rather negative SNAO phase. This change in SNAO phase is opposite in sign from that expected by a number of climate models under enhanced greenhouse forcing by the late twenty first century. It has led to noticeably wetter summers in North West Europe in the last decade. On interannual to multidecadal timescales, SNAO variability is linked to variations in North Atlantic sea surface temperature (SST): observations and models indicate an association between the Atlantic Multi-decadal Oscillation (AMO) where the cold (warm) phase of the AMO corresponds a positive (negative) phase of the SNAO. Observations also indicate a link with SST in the Gulf Stream region of the North Atlantic where, particularly on decadal time scales, SST warming may favour a more positive phase of the SNAO. Influences of Arctic climate change on North Atlantic and European atmospheric circulation may also exist, particularly reduced sea ice coverage, perhaps favouring the negative phase of the SNAO. A new tree-ring data based JJA SNAO reconstruction extending over the last millennium, as well as climate model output for the same period, enables us to examine the influence of North Atlantic SST and Arctic sea-ice coverage, as well as SNAO impacts on European summer climate, in a long-term, pre-industrial context. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1393921','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1393921">Variability of fire emissions on interannual to multi-decadal timescales in two Earth System models</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ward, D. S.; Shevliakova, E.; Malyshev, S. Connections between wildfires and modes of variability in climate are sought as a means for predicting fire activity on interannual to multi-decadal timescales. Several fire drivers, such as temperature and local drought index, have been shown to vary on these timescales, and analysis of tree-ring data suggests covariance between fires and climate oscillation indices in some regions. HBut, the shortness of the satellite record of global fire events limits investigations on larger spatial scales. Here we explore the interplay between climate variability and wildfire emissions with the preindustrial long control numerical experiments and historical ensembles of CESM1 and the NOAA/GFDLmore » ESM2Mb. We find that interannual variability in fires is underpredicted in both Earth System models (ESMs) compared to present day fire emission inventories. Modeled fire emissions respond to the El Niño/southern oscillation (ENSO) and Pacific decadal oscillation (PDO) with increases in southeast Asia and boreal North America emissions, and decreases in southern North America and Sahel emissions, during the ENSO warm phase in both ESMs, and the PDO warm phase in CESM1. In addition, CESM1 produces decreases in boreal northern hemisphere fire emissions for the warm phase of the Atlantic Meridional Oscillation. Through analysis of the long control simulations, we show that the 20th century trends in both ESMs are statistically significant, meaning that the signal of anthropogenic activity on fire emissions over this time period is detectable above the annual to decadal timescale noise. However, the trends simulated by the two ESMs are of opposite sign (CESM1 decreasing, ESM2Mb increasing), highlighting the need for improved understanding, proxy observations, and modeling to resolve this discrepancy.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ERL....11l5008W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ERL....11l5008W">Variability of fire emissions on interannual to multi-decadal timescales in two Earth System models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ward, D. S.; Shevliakova, E.; Malyshev, S.; Lamarque, J.-F.; Wittenberg, A. T. 2016-12-01 Connections between wildfires and modes of variability in climate are sought as a means for predicting fire activity on interannual to multi-decadal timescales. Several fire drivers, such as temperature and local drought index, have been shown to vary on these timescales, and analysis of tree-ring data suggests covariance between fires and climate oscillation indices in some regions. However, the shortness of the satellite record of global fire events limits investigations on larger spatial scales. Here we explore the interplay between climate variability and wildfire emissions with the preindustrial long control numerical experiments and historical ensembles of CESM1 and the NOAA/GFDL ESM2Mb. We find that interannual variability in fires is underpredicted in both Earth System models (ESMs) compared to present day fire emission inventories. Modeled fire emissions respond to the El Niño/southern oscillation (ENSO) and Pacific decadal oscillation (PDO) with increases in southeast Asia and boreal North America emissions, and decreases in southern North America and Sahel emissions, during the ENSO warm phase in both ESMs, and the PDO warm phase in CESM1. Additionally, CESM1 produces decreases in boreal northern hemisphere fire emissions for the warm phase of the Atlantic Meridional Oscillation. Through analysis of the long control simulations, we show that the 20th century trends in both ESMs are statistically significant, meaning that the signal of anthropogenic activity on fire emissions over this time period is detectable above the annual to decadal timescale noise. However, the trends simulated by the two ESMs are of opposite sign (CESM1 decreasing, ESM2Mb increasing), highlighting the need for improved understanding, proxy observations, and modeling to resolve this discrepancy. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011CliPa...7.1123R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011CliPa...7.1123R">Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rodgers, K. B.; Mikaloff-Fletcher, S. E.; Bianchi, D.; Beaulieu, C.; Galbraith, E. D.; Gnanadesikan, A.; Hogg, A. G.; Iudicone, D.; Lintner, B. R.; Naegler, T.; Reimer, P. J.; Sarmiento, J. L.; Slater, R. D. 2011-10-01 Tree ring Δ14C data (Reimer et al., 2004; McCormac et al., 2004) indicate that atmospheric Δ14C varied on multi-decadal to centennial timescales, in both hemispheres, over the period between AD 950 and 1830. The Northern and Southern Hemispheric Δ14C records display similar variability, but from the data alone is it not clear whether these variations are driven by the production of 14C in the stratosphere (Stuiver and Quay, 1980) or by perturbations to exchanges between carbon reservoirs (Siegenthaler et al., 1980). As the sea-air flux of 14CO2 has a clear maximum in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the interhemispheric gradient. In this study, model simulations are used to show that Southern Ocean winds are likely a main driver of the observed variability in the interhemispheric gradient over AD 950-1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980-2004). This interpretation also implies that there may have been a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds at the Medieval Climate Anomaly to Little Ice Age transition remain unknown. Our process-focused suite of perturbation experiments with models raises the possibility that the current generation of coupled climate and earth system models may underestimate the natural background multi-decadal- to centennial-timescale variations in the winds over the Southern Ocean. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP11B1031H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP11B1031H">Biological and climate controls on North Atlantic marine carbon dynamics over the last millennium: Insights from an absolutely-dated shell based record from the North Icelandic Shelf</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hall, I. R.; Reynolds, D.; Scourse, J. D.; Richardson, C.; Wanamaker, A. D.; Butler, P. G. 2017-12-01 Given the rapid increase in atmospheric carbon dioxide concentrations (pCO2) over the industrial era there is a pressing need to construct longterm records of natural carbon cycling prior to this perturbation and to develop a more robust understanding of the role the oceans play in the sequestration of atmospheric carbon. Here we reconstruct the historical biological and climatic controls on the carbon isotopic (δ13C-shell) composition of the North Icelandic shelf waters over the last millennium derived from the shells of the long-lived marine bivalve mollusc Arctica islandica. Variability in the annually resolved δ13C-shell record is dominated by multi-decadal variability with a negative trend (-0.003±0.002‰yr-1) over the industrial era (1800-2000). This trend is consistent with the marine Suess effect brought about by the sequestration of isotopically light carbon (δ13C of CO2) derived from the burning of fossil fuels. Comparison of the δ13C-shell record with contemporary proxy archives, over the last millennium, and instrumental data over the 20th century, suggests that primary productivity and climate conditions over the sub-polar North Atlantic region played a vital role in driving inter-annual to multi-decadal scale variability in the δ13C-shell record. Our results highlight that relative shifts in the proportion of sub-polar mode waters and Arctic intermediate waters entrained onto the North Icelandic shelf, coupled with atmospheric circulation patterns associated with the winter North Atlantic Oscillation (wNAO), are the likely physical mechanisms that drive natural variations in seawater δ13C variability on the North Icelandic shelf. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1393921-variability-fire-emissions-interannual-multi-decadal-timescales-two-earth-system-models','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1393921-variability-fire-emissions-interannual-multi-decadal-timescales-two-earth-system-models">Variability of fire emissions on interannual to multi-decadal timescales in two Earth System models</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Ward, D. S.; Shevliakova, E.; Malyshev, S.; ... 2016-12-02 Connections between wildfires and modes of variability in climate are sought as a means for predicting fire activity on interannual to multi-decadal timescales. Several fire drivers, such as temperature and local drought index, have been shown to vary on these timescales, and analysis of tree-ring data suggests covariance between fires and climate oscillation indices in some regions. HBut, the shortness of the satellite record of global fire events limits investigations on larger spatial scales. Here we explore the interplay between climate variability and wildfire emissions with the preindustrial long control numerical experiments and historical ensembles of CESM1 and the NOAA/GFDLmore » ESM2Mb. We find that interannual variability in fires is underpredicted in both Earth System models (ESMs) compared to present day fire emission inventories. Modeled fire emissions respond to the El Niño/southern oscillation (ENSO) and Pacific decadal oscillation (PDO) with increases in southeast Asia and boreal North America emissions, and decreases in southern North America and Sahel emissions, during the ENSO warm phase in both ESMs, and the PDO warm phase in CESM1. In addition, CESM1 produces decreases in boreal northern hemisphere fire emissions for the warm phase of the Atlantic Meridional Oscillation. Through analysis of the long control simulations, we show that the 20th century trends in both ESMs are statistically significant, meaning that the signal of anthropogenic activity on fire emissions over this time period is detectable above the annual to decadal timescale noise. However, the trends simulated by the two ESMs are of opposite sign (CESM1 decreasing, ESM2Mb increasing), highlighting the need for improved understanding, proxy observations, and modeling to resolve this discrepancy.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMGC23C..03F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMGC23C..03F">Holocene Multi-Decadal to Millennial-Scale Hydrologic Variability on the South American Altiplano</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fritz, S. C.; Baker, P. A.; Ekdahl, E.; Burns, S. 2006-12-01 On orbital timescales, lacustrine sediment records in the tropical central Andes show massive changes in lake level due to mechanisms related to global-scale drivers, varying at precessional timescales. Here we use stable isotopic and diatom records from two lakes in the Lake Titicaca drainage basin to reconstruct multi- decadal to millennial scale precipitation variability during the last 7000 to 8000 years. The records are tightly coupled at multi-decadal to millennial scales with each other and with lake-level fluctuations in Lake Titicaca, indicating that the lakes are recording a regional climate signal. A quantitative reconstruction of precipitation from stable isotopic data indicates that the central Andes underwent significant wet to dry alternations at multi- centennial frequencies with an amplitude of 30 to 40% of total precipitation. A strong millennial-scale component, similar in duration to periods of increased ice rafted debris flux in the North Atlantic, is observed in both lake records, suggesting that tropical North Atlantic sea-surface temperature (SST) variability may partly control regional precipitation. No clear relationship is evident between these records and the inferred ENSO history from Lago Pallcacocha in the northern tropical Andes. In the instrumental period, regional precipitation variability on inter-annual timescales is clearly influenced by Pacific modes; for example, most El Ninos produce dry and warm conditions in this part of the central Andes. However, on longer timescales, the control of tropical Pacific modes is less clear. Our reconstructions suggest that the cold intervals of the Holocene Bond events are periods of increased precipitation in the central Andes, thus indicating an anti-phasing of precipitation variation in the southern tropics of South America relative to the Northern Hemisphere monsoon region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4319Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4319Y">Underestimated AMOC Variability and Implications for AMV and Predictability in CMIP Models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yan, Xiaoqin; Zhang, Rong; Knutson, Thomas R. 2018-05-01 The Atlantic Meridional Overturning Circulation (AMOC) has profound impacts on various climate phenomena. Using both observations and simulations from the Coupled Model Intercomparison Project Phase 3 and 5, here we show that most models underestimate the amplitude of low-frequency AMOC variability. We further show that stronger low-frequency AMOC variability leads to stronger linkages between the AMOC and key variables associated with the Atlantic multidecadal variability (AMV), and between the subpolar AMV signal and northern hemisphere surface air temperature. Low-frequency extratropical northern hemisphere surface air temperature variability might increase with the amplitude of low-frequency AMOC variability. Atlantic decadal predictability is much higher in models with stronger low-frequency AMOC variability and much lower in models with weaker or without AMOC variability. Our results suggest that simulating realistic low-frequency AMOC variability is very important, both for simulating realistic linkages between AMOC and AMV-related variables and for achieving substantially higher Atlantic decadal predictability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.3597A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.3597A">Time Scales and Sources of European Temperature Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Årthun, Marius; Kolstad, Erik W.; Eldevik, Tor; Keenlyside, Noel S. 2018-04-01 Skillful predictions of continental climate would be of great practical benefit for society and stakeholders. It nevertheless remains fundamentally unresolved to what extent climate is predictable, for what features, at what time scales, and by which mechanisms. Here we identify the dominant time scales and sources of European surface air temperature (SAT) variability during the cold season using a coupled climate reanalysis, and a statistical method that estimates SAT variability due to atmospheric circulation anomalies. We find that eastern Europe is dominated by subdecadal SAT variability associated with the North Atlantic Oscillation, whereas interdecadal and multidecadal SAT variability over northern and southern Europe are thermodynamically driven by ocean temperature anomalies. Our results provide evidence that temperature anomalies in the North Atlantic Ocean are advected over land by the mean westerly winds and, hence, provide a mechanism through which ocean temperature controls the variability and provides predictability of European SAT. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110013132','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110013132">New Insights in Tropospheric Ozone and its Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Oman, Luke D.; Douglass, Anne R.; Ziemke, Jerry R.; Rodriquez, Jose M. 2011-01-01 We have produced time-slice simulations using the Goddard Earth Observing System Version 5 (GEOS-5) coupled to a comprehensive stratospheric and tropospheric chemical mechanism. These simulations are forced with observed sea surface temperatures over the past 25 years and use constant specified surface emissions, thereby providing a measure of the dynamically controlled ozone response. We examine the model performance in simulating tropospheric ozone and its variability. Here we show targeted comparisons results from our simulations with a multi-decadal tropical tropospheric column ozone dataset obtained from satellite observations of total column ozone. We use SHADOZ ozonesondes to gain insight into the observed vertical response and compare with the simulated vertical structure. This work includes but is not limited to ENSO related variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..939D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..939D">The bivalve Glycymeris longior as an environmental archive for the Mar Argentino, southern South Atlantic</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> del Socorro Doldan, María; Morsan, Enrique Mario; Giménez, Lucas; Zaidman, Paula Cecilia 2017-04-01 Southern Hemisphere lacks of suitable high-resolution long datasets for the marine environment. This is translated in poor understanding of climate dynamics and processes at regional and continental-scale. We assessed the potential of Glycymeris longior as an environmental indicator for the mid-latitudes of South Atlantic by applying sclerochronological techniques on sample sets collected from San Matías Gulf, Mar Argentino, southern South Atlantic. We present a reconstruction of marine environmental variability of SMG for the period 1890-2016, covering 125 years. The reconstruction is based on the growth increment series for the first absolutely-dated annually-resolved multi-decadal G. longior bivalve on Sothern Atlantic. Shells were collected in 1918, 1933, 1945, 1983, 1989, 2009, 2011, 2015 and 2016. Sample depth varies between collection years. Age of the individuals was estimated from the hinge region of the shell. G. longior forms an annual narrow growth line. Maximal longevity was 40 years old. A strong common environmental signal is apparent in the increment widths. Correlations between the growth increment indices and regional temperature series (sea surface temperatures, continental temperatures) and other proxies were made. Preliminary results indicate that G.longior sclerochronologies, combined with low-frequency proxies can facilitate reconstructions of oceanographic variability. We discuss multi-decadal climate variability. Given the ability to generate annually-resolved chronologies G. longior is likely to be used as a climate recorder in southern South America. Hence, G. longior shells from Pleistocene marine deposits from Patagonia, Argentina, have a considerable potential to contain information of past climate for mid-latitudes of South Atlantic. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESSD....9..955G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESSD....9..955G">A multi-decadal wind-wave hindcast for the North Sea 1949-2014: coastDat2</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Groll, Nikolaus; Weisse, Ralf 2017-12-01 Long and consistent wave data are important for analysing wave climate variability and change. Moreover, such wave data are also needed in coastal and offshore design and for addressing safety-related issues at sea. Using the third-generation spectral wave model WAM a multi-decadal wind-wave hindcast for the North Sea covering the period 1949-2014 was produced. The hindcast is part of the coastDat database representing a consistent and homogeneous met-ocean data set. It is shown that despite not being perfect, data from the wave hindcast are generally suitable for wave climate analysis. In particular, comparisons of hindcast data with in situ and satellite observations show on average a reasonable agreement, while a tendency towards overestimation of the highest waves could be inferred. Despite these limitations, the wave hindcast still provides useful data for assessing wave climate variability and change as well as for risk analysis, in particular when conservative estimates are needed. Hindcast data are stored at the World Data Center for Climate (WDCC) and can be freely accessed using the <a href="https://doi.org/10.1594/WDCC/coastDat-2_WAM-North_Sea" target="_blank">doi:10.1594/WDCC/coastDat-2_WAM-North_Sea</a> Groll and Weisse(2016) or via the coastDat web-page <a href="http://www.coastdat.de" target="_blank">http://www.coastdat.de</a>. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/biblio/1054032-testing-possible-influence-unknown-climate-forcings-upon-global-temperature-increases-from','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1054032-testing-possible-influence-unknown-climate-forcings-upon-global-temperature-increases-from">Testing for the Possible Influence of Unknown Climate Forcings upon Global Temperature Increases from 1950-2000</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Anderson, Bruce T.; Knight, Jeff R.; Ringer, Mark A. 2012-10-15 Global-scale variations in the climate system over the last half of the twentieth century, including long-term increases in global-mean near-surface temperatures, are consistent with concurrent human-induced emissions of radiatively active gases and aerosols. However, such consistency does not preclude the possible influence of other forcing agents, including internal modes of climate variability or unaccounted for aerosol effects. To test whether other unknown forcing agents may have contributed to multidecadal increases in global-mean near-surface temperatures from 1950 to 2000, data pertaining to observed changes in global-scale sea surface temperatures and observed changes in radiatively active atmospheric constituents are incorporated into numericalmore » global climate models. Results indicate that the radiative forcing needed to produce the observed long-term trends in sea surface temperatures—and global-mean near-surface temperatures—is provided predominantly by known changes in greenhouse gases and aerosols. Further, results indicate that less than 10% of the long-term historical increase in global-mean near-surface temperatures over the last half of the twentieth century could have been the result of internal climate variability. In addition, they indicate that less than 25%of the total radiative forcing needed to produce the observed long-term trend in global-mean near-surface temperatures could have been provided by changes in net radiative forcing from unknown sources (either positive or negative). These results, which are derived from simple energy balance requirements, emphasize the important role humans have played in modifying the global climate over the last half of the twentieth century.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17197425','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17197425">Contingent Pacific-Atlantic Ocean influence on multicentury wildfire synchrony over western North America.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kitzberger, Thomas; Brown, Peter M; Heyerdahl, Emily K; Swetnam, Thomas W; Veblen, Thomas T 2007-01-09 Widespread synchronous wildfires driven by climatic variation, such as those that swept western North America during 1996, 2000, and 2002, can result in major environmental and societal impacts. Understanding relationships between continental-scale patterns of drought and modes of sea surface temperatures (SSTs) such as El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) may explain how interannual to multidecadal variability in SSTs drives fire at continental scales. We used local wildfire chronologies reconstructed from fire scars on tree rings across western North America and independent reconstructions of SST developed from tree-ring widths at other sites to examine the relationships of multicentury patterns of climate and fire synchrony. From 33,039 annually resolved fire-scar dates at 238 sites (the largest paleofire record yet assembled), we examined forest fires at regional and subcontinental scales. Since 1550 CE, drought and forest fires covaried across the West, but in a manner contingent on SST modes. During certain phases of ENSO and PDO, fire was synchronous within broad subregions and sometimes asynchronous among those regions. In contrast, fires were most commonly synchronous across the West during warm phases of the AMO. ENSO and PDO were the main drivers of high-frequency variation in fire (interannual to decadal), whereas the AMO conditionally changed the strength and spatial influence of ENSO and PDO on wildfire occurrence at multidecadal scales. A current warming trend in AMO suggests that we may expect an increase in widespread, synchronous fires across the western U.S. in coming decades. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PalOc..29..403D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PalOc..29..403D">A reconstruction of sea surface temperature variability in the southeastern Gulf of Mexico from 1734 to 2008 C.E. using cross-dated Sr/Ca records from the coral Siderastrea siderea</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> DeLong, Kristine L.; Flannery, Jennifer A.; Poore, Richard Z.; Quinn, Terrence M.; Maupin, Christopher R.; Lin, Ke; Shen, Chuan-Chou 2014-05-01 This study uses skeletal variations in coral Sr/Ca from three Siderastrea siderea coral colonies within the Dry Tortugas National Park in the southeastern Gulf of Mexico (24°42'N, 82°48'W) to reconstruct monthly sea surface temperature (SST) variations from 1734 to 2008 Common Era (C.E.). Calibration and verification of the replicated coral Sr/Ca-SST reconstruction with local, regional, and historical temperature records reveals that this proxy-temperature relationship is stable back to 1879 C.E. The coral SST reconstruction contains robust interannual ( 2.0°C) and multidecadal variability ( 1.5°C) for the past 274 years, the latter of which does not covary with the Atlantic Multidecadal Oscillation. Winter SST extremes are more variable than summer SST extremes (±2.2°C versus ±1.6°C, 2σ) suggesting that Loop Current transport in the winter dominates variability on interannual and longer time scales. Summer SST maxima are increasing (+1.0°C for 274 years, σMC = ±0.5°C, 2σ), whereas winter SST minima contain no significant trend. Colder decades ( 1.5°C) during the Little Ice Age (LIA) do not coincide with decades of sunspot minima. The coral SST reconstruction contains similar variability to temperature reconstructions from the northern Gulf of Mexico (planktic foraminifer Mg/Ca) and the Caribbean Sea (coral Sr/Ca) suggesting areal reductions in the Western Hemisphere Warm Pool during the LIA. Mean summer coral SST extremes post-1985 C.E. (29.9°C) exceeds the long-term summer average (29.2°C for 1734-2008 C.E.), yet the warming trend after 1985 C.E. (0.04°C for 24 years, σMC = ±0.5, 2σ) is not significant, whereas Caribbean coral Sr/Ca studies contain a warming trend for this interval. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25752943','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25752943">An atmospheric origin of the multi-decadal bipolar seesaw.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wang, Zhaomin; Zhang, Xiangdong; Guan, Zhaoyong; Sun, Bo; Yang, Xin; Liu, Chengyan 2015-03-10 A prominent feature of recent climatic change is the strong Arctic surface warming that is contemporaneous with broad cooling over much of Antarctica and the Southern Ocean. Longer global surface temperature observations suggest that this contrasting pole-to-pole change could be a manifestation of a multi-decadal interhemispheric or bipolar seesaw pattern, which is well correlated with the North Atlantic sea surface temperature variability, and thus generally hypothesized to originate from Atlantic meridional overturning circulation oscillations. Here, we show that there is an atmospheric origin for this seesaw pattern. The results indicate that the Southern Ocean surface cooling (warming) associated with the seesaw pattern is attributable to the strengthening (weakening) of the Southern Hemisphere westerlies, which can be traced to Northern Hemisphere and tropical tropospheric warming (cooling). Antarctic ozone depletion has been suggested to be an important driving force behind the recently observed increase in the Southern Hemisphere's summer westerly winds; our results imply that Northern Hemisphere and tropical warming may have played a triggering role at an stage earlier than the first detectable Antarctic ozone depletion, and enhanced Antarctic ozone depletion through decreasing the lower stratospheric temperature. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170003432','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170003432">Positive Low Cloud and Dust Feedbacks Amplify Tropical North Atlantic Multidecadal Variability</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Yuan, Tianle; Oraiopoulos, Lazaros; Zelinka, Mark; Yu, Hongbin; Norris, Joel R.; Chin, Mian; Platnick, Steven; Meyer, Kerry 2016-01-01 The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP43C..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP43C..01A">Past Asian Monsoon circulation from multiple tree-ring proxies and models (Invited)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Anchukaitis, K. J.; Herzog, M.; Hernandez, M.; Martin-Benito, D.; Gagen, M.; LeGrande, A. N.; Ummenhofer, C.; Buckley, B.; Cook, E. R. 2013-12-01 The Asian monsoon can be characterized in terms of precipitation variability as well as features of regional atmospheric circulation across a range of spatial and temporal scales. While multicentury time series of tree-ring widths at hundreds of sites across Asia provide estimates of past rainfall, the oxygen isotope ratios of annual rings at some of these sites can reveal broader regional atmosphere-ocean dynamics. Here we present a replicated, multicentury stable isotope series from Vietnam that integrates the influence of monsoon circulation on water isotopes. Stronger (weaker) monsoon flow over Indochina is associated with lower (higher) oxygen isotope values in our long-lived tropical conifers. Ring width and isotopes show particular coherence at multidecadal time scales, and together allow past precipitation amount and circulation strength to be disentangled. Combining multiple tree-ring proxies with simulations from isotope-enabled and paleoclimate general circulation models allows us to independently assess the mechanisms responsible for proxy formation and to evaluate how monsoon rainfall is influenced by ocean-atmosphere interactions at timescales from interannual to multidecadal. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080045757&hterms=climate+change+anthropogenic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dclimate%2Bchange%2Banthropogenic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080045757&hterms=climate+change+anthropogenic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dclimate%2Bchange%2Banthropogenic">Multi-Decadal Variation of Aerosols: Sources, Transport, and Climate Effects</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Chin, Mian; Diehl, Thomas; Bian, Huisheng; Streets, David 2008-01-01 We present a global model study of multi-decadal changes of atmospheric aerosols and their climate effects using a global chemistry transport model along with the near-term to longterm data records. We focus on a 27-year time period of satellite era from 1980 to 2006, during which a suite of aerosol data from satellite observations, ground-based measurements, and intensive field experiments have become available. We will use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, which involves a time-varying, comprehensive global emission dataset that we put together in our previous investigations and will be improved/extended in this project. This global emission dataset includes emissions of aerosols and their precursors from fuel combustion, biomass burning, volcanic eruptions, and other sources from 1980 to the present. Using the model and satellite data, we will analyze (1) the long-term global and regional aerosol trends and their relationship to the changes of aerosol and precursor emissions from anthropogenic and natural sources, (2) the intercontinental source-receptor relationships controlled by emission, transport pathway, and climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA609706','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA609706">Intraseasonal to Interannual Variability of the Atlantic Meridional Overturning Circulation from Eddy-resolving Simulations and Observations</a> <a target="_blank" rel="noopener noreferrer" href="http://www.dtic.mil/">DTIC Science & Technology</a> 2014-07-01 flow of warm, saline water in approximately the upper 1 km overlying a net southward flow of cold, fresh water [see Long- worth and Bryden, 2007 ...of the Arctic sea ice [Serreze et al., 2007 ] and Greenland glaciers [Holland et al., 2008; Straneo et al., 2010]. On a broader scale, fluctuations of...the AMOC are often linked to the Atlantic multidecadal oscillation [Knight et al., 2005; Delworth et al., 2007 ], the domi- nant pattern of </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP51A1059P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP51A1059P">Multi-decadal Variability of the Indian Monsoon Rainfall for the last 14 kyr</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Panmei, C.; Pothuri, D. 2017-12-01 Precise reconstruction of Indian monsoon fluctuation events and variability trends over the last 14 kyr has great implications for understanding the dynamics and possible forcing/feedback mechanisms associated with it. We have carried out high-resolution Indian monsoon variability studies of multi-decadal to sub-centennial timescales for the past 14 kyr through oxygen isotopes and Mg/Ca-derived sea surface temperatures (SST) from a western Bay of Bengal sediment core MD 161/17, using planktonic foraminifera Globigerinoides ruber. Indian summer monsoon (ISM) intensity was low during the Younger Dryas (YD) as evidenced by enriched δ18Osw coincides with a striking warming of 1.5°C. We observed ISM intensification from 12-9 kyr, followed by a milder period from 9-7.2 kyr. ISM gradually weakened from 7.2-2.5 kyr, after which there were two very prominent shifts in both ISM and SST; abrupt decrease at 2.4 kyr and increase at 1.4 kyr for ISM, while SST exhibited opposite trend. The contrasting trend continued from 1.4 kyr to the present wherein ISM precipitation has been decreasing and SST has been increasing. In addition, spectral analysis was done using Redfit and the ISM precipitation records reveal statistically significant periodicities at 2118, 411, 344, 144, 101 and 90 yrs. Furthermore, we compared our results with other existing records from the Northern Indian Ocean and adjacent regions, and found that the records share similarities suggesting regional dynamics being expressed coherently. Our results suggest that ISM precipitation and warming/cooling of the Northern Indian Ocean is directly associated with the southward/northward shift of the Intertropical Convergence Zone, which in turn is influenced by Atlantic Meridional Overturning Circulation, North Atlantic climate, and solar insolation interplaying differently at different timescales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.4214I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.4214I">Upper ocean O2 trends: 1958-2015</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ito, Takamitsu; Minobe, Shoshiro; Long, Matthew C.; Deutsch, Curtis 2017-05-01 Historic observations of dissolved oxygen (O2) in the ocean are analyzed to quantify multidecadal trends and variability from 1958 to 2015. Additional quality control is applied, and the resultant oxygen anomaly field is used to quantify upper ocean O2 trends at global and hemispheric scales. A widespread negative O2 trend is beginning to emerge from the envelope of interannual variability. Ocean reanalysis data are used to evaluate relationships with changes in ocean heat content (OHC) and oxygen solubility (O2,sat). Global O2 decline is evident after the 1980s, accompanied by an increase in global OHC. The global upper ocean O2 inventory (0-1000 m) changed at the rate of -243 ± 124 T mol O2 per decade. Further, the O2 inventory is negatively correlated with the OHC (r = -0.86; 0-1000 m) and the regression coefficient of O2 to OHC is approximately -8.2 ± 0.66 nmol O2 J-1, on the same order of magnitude as the simulated O2-heat relationship typically found in ocean climate models. Variability and trends in the observed upper ocean O2 concentration are dominated by the apparent oxygen utilization component with relatively small contributions from O2,sat. This indicates that changing ocean circulation, mixing, and/or biochemical processes, rather than the direct thermally induced solubility effects, are the primary drivers for the observed O2 changes. The spatial patterns of the multidecadal trend include regions of enhanced ocean deoxygenation including the subpolar North Pacific, eastern boundary upwelling systems, and tropical oxygen minimum zones. Further studies are warranted to understand and attribute the global O2 trends and their regional expressions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.4061E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.4061E">Wavelet-based time series bootstrap model for multidecadal streamflow simulation using climate indicators</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Erkyihun, Solomon Tassew; Rajagopalan, Balaji; Zagona, Edith; Lall, Upmanu; Nowak, Kenneth 2016-05-01 A model to generate stochastic streamflow projections conditioned on quasi-oscillatory climate indices such as Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO) is presented. Recognizing that each climate index has underlying band-limited components that contribute most of the energy of the signals, we first pursue a wavelet decomposition of the signals to identify and reconstruct these features from annually resolved historical data and proxy based paleoreconstructions of each climate index covering the period from 1650 to 2012. A K-Nearest Neighbor block bootstrap approach is then developed to simulate the total signal of each of these climate index series while preserving its time-frequency structure and marginal distributions. Finally, given the simulated climate signal time series, a K-Nearest Neighbor bootstrap is used to simulate annual streamflow series conditional on the joint state space defined by the simulated climate index for each year. We demonstrate this method by applying it to simulation of streamflow at Lees Ferry gauge on the Colorado River using indices of two large scale climate forcings: Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO), which are known to modulate the Colorado River Basin (CRB) hydrology at multidecadal time scales. Skill in stochastic simulation of multidecadal projections of flow using this approach is demonstrated. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PApGe.174.2863B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PApGe.174.2863B">Multi-Decadal Oscillations of the Ocean Active Upper-Layer Heat Content</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Byshev, Vladimir I.; Neiman, Victor G.; Anisimov, Mikhail V.; Gusev, Anatoly V.; Serykh, Ilya V.; Sidorova, Alexandra N.; Figurkin, Alexander L.; Anisimov, Ivan M. 2017-07-01 Spatial patterns in multi-decadal variability in upper ocean heat content for the last 60 years are examined using a numerical model developed at the Institute of Numerical Mathematics of Russia (INM Model) and sea water temperature-salinity data from the World Ocean Database (in: Levitus, NOAA Atlas NESDIS 66, U.S. Wash.: Gov. Printing Office, 2009). Both the model and the observational data show that the heat content of the Active Upper Layer (AUL) in particular regions of the Atlantic, Pacific and Southern oceans have experienced prominent simultaneous variations on multi-decadal (25-35 years) time scales. These variations are compared earlier revealed climatic alternations in the Northern Atlantic region during the last century (Byshev et al. in Doklady Earth Sci 438(2):887-892, 2011). We found that from the middle of 1970s to the end of 1990s the AUL heat content decreased in several oceanic regions, while the mean surface temperature increased on Northern Hemisphere continents according to IPCC (in: Stocker et al. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change, Cambridge University Press, Cambridge, 2013). This means that the climate-forcing effect of the ocean-atmosphere interaction in certain energy-active areas determines not only local climatic processes, but also have an influence on global-scale climate phenomena. Here we show that specific regional features of the AUL thermal structure are in a good agreement with climatic conditions on the adjacent continents. Further, the ocean AUL in the five distinctive regions identified in our study have resumed warming in the first decade of this century. By analogy inference from previous climate scenarios, this may signal the onset of more continental climate over mainlands. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27245575','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27245575">Multi-model attribution of upper-ocean temperature changes using an isothermal approach.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Weller, Evan; Min, Seung-Ki; Palmer, Matthew D; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook 2016-06-01 Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...626926W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...626926W">Multi-model attribution of upper-ocean temperature changes using an isothermal approach</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Weller, Evan; Min, Seung-Ki; Palmer, Matthew D.; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook 2016-06-01 Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..MARG40005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..MARG40005C">Causes and implications of the growing divergence between climate model simulations and observations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Curry, Judith 2014-03-01 For the past 15+ years, there has been no increase in global average surface temperature, which has been referred to as a 'hiatus' in global warming. By contrast, estimates of expected warming in the first several decades of 21st century made by the IPCC AR4 were 0.2C/decade. This talk summarizes the recent CMIP5 climate model simulation results and comparisons with observational data. The most recent climate model simulations used in the AR5 indicate that the warming stagnation since 1998 is no longer consistent with model projections even at the 2% confidence level. Potential causes for the model-observation discrepancies are discussed. A particular focus of the talk is the role of multi-decadal natural internal variability on the climate variability of the 20th and early 21st centuries. The ``stadium wave'' climate signal is described, which propagates across the Northern Hemisphere through a network of ocean, ice, and atmospheric circulation regimes that self-organize into a collective tempo. The stadium wave hypothesis provides a plausible explanation for the hiatus in warming and helps explain why climate models did not predict this hiatus. Further, the new hypothesis suggests how long the hiatus might last. Implications of the hiatus are discussed in context of climate model sensitivity to CO2 forcing and attribution of the warming that was observed in the last quarter of the 20th century. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1414S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1414S">The Baltic Sea natural long-term variability of salinity</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schimanke, Semjon; Markus Meier, H. E. 2015-04-01 The Baltic Sea is one of the largest brackish sea areas of the world. The sensitive state of the Baltic Sea is sustained by a fresh-water surplus by river discharge and precipitation on one hand as well as inflows of highly saline and oxygen-rich water masses from the North Sea on the other. Major inflows which are crucial for the renewal of the deep water occur very intermittent with a mean frequency of approximately one per year. Stagnation periods (periods without major inflows) lead for instance to a reduction of oxygen concentration in the deep Baltic Sea spreading hypoxic conditions. Depending on the amount of salt water inflow and fresh-water supply the deep water salinity of the Baltic Sea varies between 11 to 14 PSU on the decadal scale. The goal of this study is to understand the contribution of different driving factors for the decadal to multi-decadal variability of salinity in the Baltic Sea. Continuous measurement series of salinity exist from the 1950 but are not sufficiently long for the investigation of long-term fluctuations. Therefore, a climate simulation of more than 800 years has been carried out with the Rossby Center Ocean model (RCO). RCO is a biogeochemical regional climate model which covers the entire Baltic Sea. It is driven with atmospheric data dynamical downscaled from a GCM mimicking natural climate variability. The analysis focus on the role of variations in river discharge and precipitation, changes in wind speed and direction, fluctuations in temperature and shifts in large scale pressure patterns (e.g. NAO). Hereby, the length of the simulation will allow to identify mechanisms working on decadal to multi-decadal time scales. Moreover, it will be discussed how likely long stagnation periods are under natural climate variability and if the observed exceptional long stagnation period between 1983-1993 might be related to beginning climate change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP51C..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP51C..03K">Synchronous centennial-scale variability in abundance of remote sardine populations in the Pacific</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kuwae, M.; Takashige, S.; Yamamoto, M.; Sagawa, T.; Takeoka, H. 2012-12-01 A number of studies have identified evidence for connections between Pacific climate decadal variability and variations in Pacific marine ecosystems which are typically shown in abundance of remote sardine and anchovy species off Japan, California, Peru, and Chile as well as Alaska salmon species. The variations in climate indices and abundance of sardine and anchovy species most likely have 50-70 year cycles and therefore these natural perturbations in climates and Pacific ecosystems should be considered for developing predictive models of fisheries productions and the managements. Despite the importance of natural perturbations for long-term predictions, one issue, whether synchronous centennial-variations in remote Pacific fisheries productions in response to climate variability exists in the past, has not been questioned, because there has never been long-term reconstructed time series in the western North Pacific. Here we present well preserved, fossil fish scale-based abundance record of Japanese sardine over the last 1100 years reconstructed from a seasonal anoxic basin in the western Seto Inland Sea near their spawning areas in the western North Pacific. A comparison of our record with other previous records clearly showed centennial-scale variations in abundance of sardine species off Japan, California, and Chile, characterized by centennial-scale alternations between low abundance regimes and high abundance regimes in which multidecadal fluctuations with large amplitudes occurred once or several times. High abundance regimes from 1450 to 1650 AD and after 1800 AD and a low abundance regime from 1650 to 1800 AD corresponded to low frequency patterns of PDO index reconstructed from tree-ring records in North America. This indicates that connections between Pacific climate variability and variations in Pacific marine ecosystems exist not only on multidecadal timescales but on centennial timescales. Three to four hundred-yr periodicity of the Pacific climate-ecosystem dynamics suggests possibility of a change into a century-long, low sardine abundance regime in the next 100 years. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP11C1038G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP11C1038G">Stable Carbon Isotopes in Treerings; Revisiting the Paleocloud Proxy.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gagen, M.; Zorita, E.; Dorado Liñán, I.; Loader, N.; McCarroll, D.; Robertson, I.; Young, G. 2017-12-01 The long term relationship between cloud cover and temperature is one of the most important climate feedbacks contributing to determining the value of climate sensitivity. Climate models still reveal a large spread in the simulation of changes in cloud cover under future warming scenarios and clarity might be aided by a picture of the past variability of cloudiness. Stable carbon isotope ratios from tree ring records have been successfully piloted as a palaeocloud proxy in geographical areas traditionally producing strong dendroclimatological reconstructions (high northern latitudes in the Northern Hemisphere) and with some notable successes elsewhere too. An expansion of tree-ring based palaeocloud reconstructions might help to estimate past variations of cloud cover in periods colder or warmer than the 20th century, providing a way to test model test this specific aspect. Calibration with measured instrumental sunshine and cloud data reveals stable carbon isotope ratios from tree rings as an indicator of incoming short wave solar radiation (SWR) in non-moisture stressed sites, but the statistical identification of the SWR signal is hampered by its interannual co-variability with air temperature during the growing season. Here we present a spatio-temporal statistical analysis of a multivariate stable carbon isotope tree ring data set over Europe to assess its usefulness to reconstruct past solar radiation changes. The interannual co-variability of the tree ring records stronger covariation with SWR than with air temperature. The resulting spatial patterns of interannual co-variability are strongly linked to atmospheric circulation in a physically consistent manner. However, the multidecadal variations in the proxy records show a less physically coherent picture. We explore whether atmospheric corrections applied to the proxy series are contributing to differences in the multi decadal signal and investigate whether multidecadal variations in soil moisture perturb the SWR. Preliminary results of strategies to bypass these problems are explored. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.476....1A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.476....1A">Speleothem records decadal to multidecadal hydroclimate variations in southwestern Morocco during the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ait Brahim, Yassine; Cheng, Hai; Sifeddine, Abdelfettah; Wassenburg, Jasper A.; Cruz, Francisco W.; Khodri, Myriam; Sha, Lijuan; Pérez-Zanón, Núria; Beraaouz, El Hassane; Apaéstegui, James; Guyot, Jean-Loup; Jochum, Klaus Peter; Bouchaou, Lhoussaine 2017-10-01 This study presents the first well-dated high resolution stable isotope (δ18 O and δ13 C) and trace element (Mg and Sr) speleothem records from southwestern Morocco covering the last 1000 yrs. Our records reveal substantial decadal to multidecadal swings between dry and humid periods, consistent with regional paleorecords with prevailing dry conditions during the Medieval Climate Anomaly (MCA), wetter conditions during the second part of the Little Ice Age (LIA), and a trend towards dry conditions during the current warm period. These coherent regional climate signals suggest common climate controls. Statistical analyses indicate that the climate of southwestern Morocco remained under the combined influence of both the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) over the last millennium. Interestingly, the generally warmer MCA and colder LIA at longer multidecadal timescales probably influenced the regional climate in North Africa through the influence on Sahara Low which weakened and strengthened the mean moisture inflow from the Atlantic Ocean during the MCA and LIA respectively. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026918','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026918">Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> McCabe, G.J.; Palecki, M.A.; Betancourt, J.L. 2004-01-01 More than half (52%) of the spatial and temporal variance in multidecadal drought frequency over the conterminous United States is attributable to the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). An additional 22% of the variance in drought frequency is related to a complex spatial pattern of positive and negative trends in drought occurrence possibly related to increasing Northern Hemisphere temperatures or some other unidirectional climate trend. Recent droughts with broad impacts over the conterminous U.S. (1996, 1999-2002) were associated with North Atlantic warming (positive AMO) and north-eastern and tropical Pacific cooling (negative PDO). Much of the long-term predictability of drought frequency may reside in the multidecadal behavior of the North Atlantic Ocean. Should the current positive AMO (warm North Atlantic) conditions persist into the upcoming decade, we suggest two possible drought scenarios that resemble the continental-scale patterns of the 1930s (positive PDO) and 1950s (negative PDO) drought. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4682045','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4682045">Atlantic multi-decadal oscillation covaries with Agulhas leakage</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Biastoch, Arne; Durgadoo, Jonathan V.; Morrison, Adele K.; van Sebille, Erik; Weijer, Wilbert; Griffies, Stephen M. 2015-01-01 The interoceanic transfer of seawater between the Indian Ocean and the Atlantic, ‘Agulhas leakage', forms a choke point for the overturning circulation in the global ocean. Here, by combining output from a series of high-resolution ocean and climate models with in situ and satellite observations, we construct a time series of Agulhas leakage for the period 1870–2014. The time series demonstrates the impact of Southern Hemisphere westerlies on decadal timescales. Agulhas leakage shows a correlation with the Atlantic Multi-decadal Oscillation on multi-decadal timescales; the former leading by 15 years. This is relevant for climate in the North Atlantic. PMID:26656850 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1259279-atlantic-multi-decadal-oscillation-covaries-agulhas-leakage','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1259279-atlantic-multi-decadal-oscillation-covaries-agulhas-leakage">Atlantic multi-decadal oscillation covaries with Agulhas leakage</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Biastoch, Arne; Durgadoo, Jonathan V.; Morrison, Adele K.; ... 2015-12-10 The interoceanic transfer of seawater between the Indian Ocean and the Atlantic, ‘Agulhas leakage’, forms a choke point for the overturning circulation in the global ocean. Here, by combining output from a series of high-resolution ocean and climate models with in situ and satellite observations, we construct a time series of Agulhas leakage for the period 1870–2014. The time series demonstrates the impact of Southern Hemisphere westerlies on decadal timescales. Agulhas leakage shows a correlation with the Atlantic Multi-decadal Oscillation on multi-decadal timescales; the former leading by 15 years. Lastly, this is relevant for climate in the North Atlantic. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://www.pnas.org/content/106/suppl.2/19685.abstract','USGSPUBS'); return false;" href="http://www.pnas.org/content/106/suppl.2/19685.abstract">Ecology and the ratchet of events: climate variability, niche dimensions, and species distributions</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Jackson, Stephen T.; Betancourt, Julio L.; Booth, Robert K.; Gray, Stephen T. 2009-01-01 Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70034289','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70034289">Ecology and the ratchet of events: Climate variability, niche dimensions, and species distributions</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Jackson, S.T.; Betancourt, J.L.; Booth, R.K.; Gray, S.T. 2009-01-01 Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and morefundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2780932','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2780932">Ecology and the ratchet of events: Climate variability, niche dimensions, and species distributions</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Jackson, Stephen T.; Betancourt, Julio L.; Booth, Robert K.; Gray, Stephen T. 2009-01-01 Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics. PMID:19805104 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70189901','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70189901">Variability common to global sea surface temperatures and runoff in the conterminous United States</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> McCabe, Gregory J.; Wolock, David M. 2014-01-01 Singular value decomposition (SVD) is used to identify the variability common to global sea surface temperatures (SSTs) and water-balance-modeled water-year (WY) runoff in the conterminous United States (CONUS) for the 1900–2012 period. Two modes were identified from the SVD analysis; the two modes explain 25% of the variability in WY runoff and 33% of the variability in WY SSTs. The first SVD mode reflects the variability of the El Niño–Southern Oscillation (ENSO) in the SST data and the hydroclimatic effects of ENSO on WY runoff in the CONUS. The second SVD mode is related to variability of the Atlantic multidecadal oscillation (AMO). An interesting aspect of these results is that both ENSO and AMO appear to have nearly equivalent effects on runoff variability in the CONUS. However, the relatively small amount of variance explained by the SVD analysis indicates that there is little covariation between runoff and SSTs, suggesting that SSTs may not be a viable predictor of runoff variability for most of the conterminous United States. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70041483','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70041483">Lake trout otolith chronologies as multidecadal indicators of high-latitude freshwater ecosystems</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Black, B.A.; Von Biela, V.R.; Zimmerman, C.E.; Brown, Randy J. 2013-01-01 High-latitude ecosystems are among the most vulnerable to long-term climate change, yet continuous, multidecadal indicators by which to gauge effects on biology are scarce, especially in freshwater environments. To address this issue, dendrochronology (tree-ring analysis) techniques were applied to growth-increment widths in otoliths from lake trout (Salvelinus namaycush) from the Chandler Lake system, Alaska (68.23°N, 152.70°W). All otoliths were collected in 1987 and exhibited highly synchronous patterns in growth-increment width. Increments were dated, the widths were measured, and age-related growth declines were removed using standard dendrochronology techniques. The detrended time series were averaged to generate an annually resolved chronology, which continuously spanned 1964–1984. The chronology positively and linearly correlated with August air temperature over the 22-year interval (p < 0.01), indicating that warmer summers were beneficial for growth, perhaps by increasing fish metabolic rate or lake productivity. Given the broad distribution of lake trout within North America, this study suggests that otolith chronologies could be used to examine responses between freshwater ecosystems and environmental variability across a range of temporal and spatial scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP31A1272A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP31A1272A">Hydro-climate variability and teleconnection patterns during the last millennium in NW Africa, inferred from speleothem records</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ait Brahim, Y.; Cheng, H.; Sifeddine, A.; Wassenburg, J. A.; Khodri, M.; Cruz, F. W., Sr. 2017-12-01 In this study, we present new paleoclimate records from two well dated Moroccan speleothems. Our stalagmites were sampled from Ifoulki cave in the Western High Atlas Mountains in SW Morocco and Chaara cave in the Eastern Middle Atlas Mountains in NE Morocco. The new paleo-records cover the last 1000 years with a high resolution and reveal substantial swings of dry and humid periods with decadal to multidecadal frequencies. The Medieval Climate Anomaly (MCA) is characterized by generally dry conditions, while wetter conditions are recorded during the Little Ice Age (LIA) and a trend towards dry conditions during the 20th century. These observations are consistent with regional climate signals, providing new insights on common climate controls and teleconnection patterns in NW Africa. We emphasize that the hydro-climate conditions in Morocco remained under the influence of the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO). At longer timescales, we hypothesize that the generally warmer MCA and colder LIA influenced the regional climate in NW Africa through interactions with local mechanisms, such as the Sahara Low, which weakened and strengthened the mean moisture inflow from the Atlantic Ocean during the MCA and LIA respectively. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThApC.129..873P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThApC.129..873P">Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pasini, Antonello; Triacca, Umberto; Attanasio, Alessandro 2017-08-01 The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean-atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001-2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere-ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26369503','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26369503">Solar forcing synchronizes decadal North Atlantic climate variability.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas 2015-09-15 Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015QSRv..121....1L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015QSRv..121....1L">Cyclic changes of Asian monsoon intensity during the early mid-Holocene from annually-laminated stalagmites, central China</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liu, Dianbing; Wang, Yongjin; Cheng, Hai; Edwards, R. L.; Kong, Xinggong 2015-08-01 Climate during the early Holocene was highly variable due to the complex interplay of external and internal forcing mechanisms. The relative importance for them on the Asian monsoon (AM) evolution yet remains to be resolved. Here we present two-to six-yr-resolution oxygen isotope (δ18O) records of five stalagmites, four of which are annually-laminated, from Qingtian Cave, central China, revealing detailed AM variability between 10.9 and 6.1 ka BP. Over the contemporaneous periods, the δ18O records agree well with each other at multi-decadal to centennial timescales. When pieced together with the previously published isotopic data from the same cave, the final δ18O record reveals detailed AM variability from the last deglaciation to the mid-Holocene, consistent with other cave records. The most striking feature of the δ18O record is the recurrence of centennial-scale oscillations, especially during the annually-counted period (8.8-6.1 ka BP). Cross-wavelet analyses between the δ18O record and solar proxies show strong coherence at 200-yr cycle, suggesting that solar output was actively involved as a primary contributor. The AM depression at 8.2 ka BP is indistinguishable in amplitude and pattern from a series of weak AM events after 8 ka BP. We speculate that these centennial-scale AM changes might be regulated by the positive feedbacks of oceanic/atmospheric interactions to the solar activity under the condition of the retreat of continental ice-sheets. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A44B..03H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A44B..03H">The long view: Causes of climate change over the instrumental period</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hegerl, G. C.; Schurer, A. P.; Polson, D.; Iles, C. E.; Bronnimann, S. 2016-12-01 The period of instrumentally recorded data has seen remarkable changes in climate, with periods of rapid warming, and periods of stagnation or cooling. A recent analysis of the observed temperature change from the instrumental record confirms that most of the warming recorded since the middle of the 20rst century has been caused by human influences, but shows large uncertainty in separating greenhouse gas from aerosol response if accounting for model uncertainty. The contribution by natural forcing and internal variability to the recent warming is estimated to be small, but becomes more important when analysing climate change over earlier or shorter time periods. For example, the enigmatic early 20th century warming was a period of strong climate anomalies, including the US dustbowl drought and exceptional heat waves, and pronounced Arctic warming. Attribution results suggests that about half of the global warming 1901-1950 was forced by greenhouse gases increases, with an anomalously strong contribution by climate variability, and contributions by natural forcing. Long term variations in circulation are important for some regional climate anomalies. Precipitation is important for impacts of climate change and precipitation changes are uncertain in models. Analysis of the instrumental record suggests a human influence on mean and heavy precipitation, and supports climate model estimates of the spatial pattern of precipitation sensitivity to warming. Broadly, and particularly over ocean, wet regions are getting wetter and dry regions are getting drier. In conclusion, the historical record provides evidence for a strong response to external forcings, supports climate models, and raises questions about multi-decadal variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812894W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812894W">Past climate variability between 97 and 7 ka reconstructed from a multi proxy speleothem record from Western Cuba</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Winterhalder, Sophie; Scholz, Denis; Mangini, Augusto; Spötl, Christoph; Jochum, Klaus Peter; Pajón, Jesús M. 2016-04-01 The tropical hydrological cycle plays a key role in regulating global climate, mainly through the export of heat and moisture to higher latitudes, and is highly sensitive to climate change, for instance due to changes in the position of the Intertropical Convergence Zone (ITCZ). Previous work on Caribbean stalagmites suggests a strong connection of precipitation variability to North Atlantic (NA) sea surface temperatures on multidecadal to millenial timescales (Fensterer et al., 2012; Fensterer et al., 2013; Winter et al., 2011). Cold phases in the NA potentially lead to a southward shift of the ITCZ and thus drier conditions in Cuba. On orbital timescales, Cuban stalagmites suggest a relation of speleothem δ18O values with the δ18O value of Caribbean surface waters (Fensterer et al., 2013). Here we present an expansion of the Cuban speleothem record covering the whole last glacial period from the end of MIS5c (97 ka BP) until 7 ka with hiatuses between 93-80 ka, 37-35 ka and 13-10 ka. Stalagmite Cuba medio (CM) has been precisely dated with 60 230Th/U-ages, mainly performed by the MC-ICPMS technique. The δ18O and δ13C records are completed by a continuous, high resolution LA-ICPMS trace element profile. These data allow for the first time to establish a multi-proxy climate reconstruction for the North Western Caribbean at decadal to centennial resolution for this period. The long-term variability of the δ18O values probably reflects rainfall amount in Cuba. The response to some Dansgaard/Oeschger and Heinrich stadials confirms the previously observed correlation between Caribbean and NA climate variability. However, this connection is not clearly imprinted throughout the record. Furthermore, trace elements, such as Mg, do not proof without ambiguity drier conditions in Cuba during NA cold events, such as the Heinrich stadials. This suggests that climate variability in Cuba was more complex during the last 100ka, and that the NA was not the only driving factor. Due to the competing influence of the NA, the Gulf of Mexico and the Pacific Ocean, the proposed severe changes in the tropical hydrological cycle during that time (such as variations of the ITCZ, insolation and the thermohaline circulation (THC)) have potentially lead to significant changes in sources and trajectories of precipitation in Western Cuba. Our record, thus, provides an important contribution towards understanding and differentiating these parameters on Caribbean climate during glacial climate changes. References: Fensterer, C., Scholz, D., Hoffmann, D., Spötl, C., Pajón, J.M., Mangini, A., 2012. Cuban stalagmite suggests relationship between Caribbean precipitation and the Atlantic Multidecadal Oscillation during the past 1.3 ka. The Holocene, 0959683612449759. Fensterer, C., Scholz, D., Hoffmann, D.L., Spötl, C., Schröder-Ritzrau, A., Horn, C., Pajón, J.M., Mangini, A., 2013. Millennial-scale climate variability during the last 12.5 ka recorded in a Caribbean speleothem. Earth and Planetary Science Letters 361, 143-151. Winter, A., Miller, T., Kushnir, Y., Sinha, A., Timmermann, A., Jury, M.R., Gallup, C., Cheng, H., Edwards, R.L., 2011. Evidence for 800years of North Atlantic multi-decadal variability from a Puerto Rican speleothem. Earth and Planetary Science Letters 308, 23-28. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP43A1456L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP43A1456L">Late Pleistocene and Holocene Hydroclimate Variability in the Tropical Andes from Alpine Lake Sediments, Cordillera de Mérida, Venezuela</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Larsen, D. J.; Abbott, M. B.; Polissar, P. J. 2014-12-01 The tropics play a major role in the global hydrologic cycle and changes to tropical rainfall patterns have critical implications for water resources and ecosystem dynamics over large geographic scales. In tropical South America, late Pleistocene and Holocene precipitation variability has been documented in geologic records and associated with numerous external and internal variables, including changes in summer insolation, South American summer monsoon strength, Pacific Ocean sea surface temperatures, continental moisture recycling, and other climate processes. However, there are few records from the northern hemisphere tropical Americas, a key region for understanding interhemispheric linkages and the drivers of tropical hydroclimate variability. Here, we present a ~13 ka record of coupled hydroclimate and environmental changes from Laguna Brava, a small (~0.07 km2), hydrologically closed lake basin situated at 2400 m asl in the Cordillera de Mérida, Venezuela. Sediment cores collected from varying water depths and proximity to shore are placed in a chronologic framework using radiocarbon ages from terrestrial macrofossils, and analyzed for a suite of physical, bulk geochemical, and stable isotopic parameters. Compound specific hydrogen isotope (D/H) measurements of terrestrial plant waxes (long-chain n-alkanes) show a sharp increase in the late Pleistocene, followed by a long-term trend toward more negative values that suggest a ~20‰ decrease in the D/H ratios of South American tropical precipitation during the Holocene. This pattern is consistent in sign and magnitude to other South American precipitation reconstructions from both hemispheres, indicating interhemispheric similarities in tropical hydroclimate variability. Superimposed on this continent-scale trend are changes in moisture balance and environmental conditions in the Venezuelan Andes. We reconstruct these parameters at Laguna Brava at multidecadal and centennial resolution and evaluate this record within the context of late Pleistocene and Holocene South American tropical hydroclimate variability and global climate changes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5384G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5384G">North Atlantic sea-level variability during the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gehrels, Roland; Long, Antony; Saher, Margot; Barlow, Natasha; Blaauw, Maarten; Haigh, Ivan; Woodworth, Philip 2014-05-01 Climate modelling studies have demonstrated that spatial and temporal sea-level variability observed in North Atlantic tide-gauge records is controlled by a complex array of processes, including ice-ocean mass exchange, freshwater forcing, steric changes, changes in wind fields, and variations in the speed of the Gulf Stream. Longer records of sea-level change, also covering the pre-industrial period, are important as a 'natural' and long-term baseline against which to test model performance and to place recent and future sea-level changes and ice-sheet change into a long-term context. Such records can only be reliably and continuously reconstructed from proxy methods. Salt marshes are capable of recording decimetre-scale sea-level variations with high precision and accuracy. In this paper we present four new high-resolution proxy records of (sub-) decadal sea-level variability reconstructed from salt-marsh sediments in Iceland, Nova Scotia, Maine and Connecticut that span the past 400 to 900 years. Our records, based on more than 100 new radiocarbon analyses, Pb-210 and Cs-137 measurements as well as other biological and geochemical age markers, together with hundreds of new microfossil observations from contemporary and fossil salt marshes, capture not only the rapid 20th century sea-level rise, but also small-scale (decimetre, multi-decadal) sea-level fluctuations during preceding centuries. We show that in Iceland three periods of rapid sea-level rise are synchronous with the three largest positive shifts of the reconstructed North Atlantic Oscillation (NAO) index. Along the North American east coast we compare our data with salt-marsh records from New Jersey, North Carolina and Florida and observe a trend of increased pre-industrial sea-level variability from south to north (Florida to Nova Scotia). Mass changes and freshwater forcing cannot explain this pattern. Based on comparisons with instrumental sea-level data and modelling studies we hypothesise that multi-decadal to centennial changes in wind and air pressure are more important than mass flux from land-based ice as drivers of North Atlantic sea-level variability during the last millennium. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B51J..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B51J..02B">Remembrance of ecohydrologic extremes past</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Band, L. E.; Hwang, T. 2013-12-01 Ecohydrological systems operate at time scales that span several orders of magnitude. Significant processes and feedbacks range from subdaily physiologic response to meteorological drivers, to soil forming and geomorphic processes ranging up through 10^3-10^4 years. While much attention in ecohydrology has focused on ecosystem optimization paradigms, these systems can show significant transience in structure and function, with apparent memory of hydroclimate extremes and regime shifts. While optimization feedbacks can be reconciled with system transience, a better understanding of the time scales and mechanisms of adjustment to increased hydroclimate variability and to specific events is required to understand and predict dynamics and vulnerability of ecosystems. Under certain circumstances of slowly varying hydroclimate, we hypothesize that ecosystems can remain adjusted to changing climate regimes, without displaying apparent system memory. Alternatively, rapid changes in hydroclimate and increased hydroclimate variability, amplified with well expressed non-linearity in the processes controlling feedbacks between water, carbon and nutrients, can move ecosystems far from adjusted states. The Coweeta Hydrological Laboratory is typical of humid, broadleaf forests in eastern North America, with a range of forest biomes from northern hardwoods at higher elevations, to oak-pine assemblages at lower elevations. The site provides almost 80 years of rainfall-runoff records for a set of watersheds under different management, along with multi-decadal forest plot structural information, soil moisture conditions and stream chemistry. An initial period of multi-decadal cooling, was followed by three decades of warming and increased hydroclimate variability. While mean temperature has risen over this time period, precipitation shows no long term trends in the mean, but has had a significant rise in variability with repeated extreme drought and wet periods. Over this latter period, intra and interannual shifts of canopy structure and phenology are discernable, along with long term canopy adjustment. We use a combination of field observations, long term remote sensing records and distributed ecohydrological modeling to investigate transient behavior, apparent memory and mechanisms of ecosystem adjustment to hydroclimate variability and change over the range of biomes in the watershed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70176084','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70176084">A reconstruction of sea surface temperature variability in the southeastern Gulf of Mexico from 1734 to 2008 C.E. using cross-dated Sr/Ca records from the coral Siderastrea siderea</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> DeLong, Kristine L.; Maupin, Christopher R.; Flannery, Jennifer A.; Quinn, Terrence M.; Shen, CC 2014-01-01 This study uses skeletal variations in coral Sr/Ca from three Siderastrea siderea coral colonies within the Dry Tortugas National Park in the southeastern Gulf of Mexico (24°42′N, 82°48′W) to reconstruct monthly sea surface temperature (SST) variations from 1734 to 2008 Common Era (C.E.). Calibration and verification of the replicated coral Sr/Ca-SST reconstruction with local, regional, and historical temperature records reveals that this proxy-temperature relationship is stable back to 1879 C.E. The coral SST reconstruction contains robust interannual (~2.0°C) and multidecadal variability (~1.5°C) for the past 274 years, the latter of which does not covary with the Atlantic Multidecadal Oscillation. Winter SST extremes are more variable than summer SST extremes (±2.2°C versus ±1.6°C, 2σ) suggesting that Loop Current transport in the winter dominates variability on interannual and longer time scales. Summer SST maxima are increasing (+1.0°C for 274 years, σMC = ±0.5°C, 2σ), whereas winter SST minima contain no significant trend. Colder decades (~1.5°C) during the Little Ice Age (LIA) do not coincide with decades of sunspot minima. The coral SST reconstruction contains similar variability to temperature reconstructions from the northern Gulf of Mexico (planktic foraminifer Mg/Ca) and the Caribbean Sea (coral Sr/Ca) suggesting areal reductions in the Western Hemisphere Warm Pool during the LIA. Mean summer coral SST extremes post-1985 C.E. (29.9°C) exceeds the long-term summer average (29.2°C for 1734–2008 C.E.), yet the warming trend after 1985 C.E. (0.04°C for 24 years, σMC = ±0.5, 2σ) is not significant, whereas Caribbean coral Sr/Ca studies contain a warming trend for this interval. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=312670&Lab=NERL&keyword=Springer%2C+E&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=312670&Lab=NERL&keyword=Springer%2C+E&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Multiscale Modeling of Multi-decadal Trends in Ozone and Precursor Species Across the Northern Hemisphere and the United States</a> <a target="_blank" rel="noopener noreferrer" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Multi-decadal model calculations for the 1990-2010 period are performed with the coupled WRF-CMAQ modeling system over a domain encompassing the northern hemisphere and a nested domain over the continental U.S. Simulated trends in ozone and precursor species concentrations acros... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..892C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..892C">Mechanisms of interannual- to decadal-scale winter Labrador Sea ice variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Close, S.; Herbaut, C.; Houssais, M.-N.; Blaizot, A.-C. 2017-12-01 The variability of the winter sea ice cover of the Labrador Sea region and its links to atmospheric and oceanic forcing are investigated using observational data, a coupled ocean-sea ice model and a fully-coupled model simulation drawn from the CMIP5 archive. A consistent series of mechanisms associated with high sea ice cover are found amongst the various data sets. The highest values of sea ice area occur when the northern Labrador Sea is ice covered. This region is found to be primarily thermodynamically forced, contrasting with the dominance of mechanical forcing along the eastern coast of Baffin Island and Labrador, and the growth of sea ice is associated with anomalously fresh local ocean surface conditions. Positive fresh water anomalies are found to propagate to the region from a source area off the southeast Greenland coast with a 1 month transit time. These anomalies are associated with sea ice melt, driven by the enhanced offshore transport of sea ice in the source region, and its subsequent westward transport in the Irminger Current system. By combining sea ice transport through the Denmark Strait in the preceding autumn with the Greenland Blocking Index and the Atlantic Multidecadal Oscillation Index, strong correlation with the Labrador Sea ice area of the following winter is obtained. This relationship represents a dependence on the availability of sea ice to be melted in the source region, the necessary atmospheric forcing to transport this offshore, and a further multidecadal-scale link with the large-scale sea surface temperature conditions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A21B0030B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A21B0030B">A volcanic wind-stress origin of the Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Birkel, S. D.; Mayewski, P. A.; Maasch, K. A.; Auger, J.; Lyon, B. 2016-12-01 The Atlantic Multidecadal Oscillation (AMO) is a mode of sea-surface temperature (SST) variability in the North Atlantic that has significant impact on global climate. Most previous studies ascribe the origin of the AMO to oceanic mechanisms, and suggest only a limited role for the atmosphere. Here, we suggest that the AMO is manifested from basin-wide changes in surface wind stress that arise in response to episodic volcanic activity. Our interpretation is based on historical SST, reanalysis, and stratospheric aerosol optical thickness data, wherein it is evident that cool (warm) intervals of the AMO coincide with emergence of strong (weak) winds and high (low) volcanic activity. We find that SST excursions ultimately develop from atmospheric forcing as volcanic events project onto the North Atlantic Oscillation (NAO). A volcanic signature is particularly evident beneath the westerlies in the subpolar region south of Greenland, where several large SST excursions occur coincident with identifiable major eruptions. High latitude surface waters cool when NAO+ circulation, which includes a deepened Icelandic Low, draws cold flow out of the Labrador Sea and into the subpolar region. Important feedbacks that cause SST anomalies to spread across the basin include cloud cover, wind-driven upwelling, and entrainment of Saharan dust into the tropical easterlies. Finally, we speculate that cooling in the North Atlantic observed since 2011 could be linked to renewed volcanic activity over Iceland, namely from the eruptions of Grímsvötn (2011) and Bárðarbunga (2014). An important question remains how North Atlantic SST variability will evolve as atmospheric circulation becomes increasingly modified by human activity. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.2931B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.2931B">Changes in intense tropical cyclone activity for the western North Pacific during the last decades derived from a regional climate model simulation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barcikowska, Monika; Feser, Frauke; Zhang, Wei; Mei, Wei 2017-11-01 An atmospheric regional climate model (CCLM) was employed to dynamically downscale atmospheric reanalyses (NCEP/NCAR 1, ERA 40) over the western North Pacific and South East Asia. This approach is used for the first time to reconstruct a tropical cyclone climatology, which extends beyond the satellite era and serves as an alternative data set for inhomogeneous observation-derived records (Best Track Data sets). The simulated TC climatology skillfully reproduces observations of the recent decades (1978-2010), including spatial patterns, frequency, lifetime, trends, variability on interannual and decadal time scales and their association with the large-scale circulation patterns. These skills, facilitated here with the spectral nudging method, seem to be a prerequisite to understand the factors determining spatio-temporal variability of TC activity over the western North Pacific. Long-term trends (1948-2011 and 1959-2001) in both simulations show a strong increase of intense tropical cyclone activity. This contrasts with pronounced multidecadal variations found in observations. The discrepancy may partly originate from temporal inhomogeneities in atmospheric reanalyses and Best Track Data, which affect both the model-based and observational-based trends. An adjustment, which removes the simulated upward trend, reduces the apparent discrepancy. Ultimately, our observational and modeling analysis suggests an important contribution of multi-decadal fluctuations in the TC activity during the last six decades. Nevertheless, due to the uncertainties associated with the inconsistencies and quality changes of those data sets, we call for special caution when reconstructing long-term TC statistics either from atmospheric reanalyses or Best Track Data. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHyd..552..704H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHyd..552..704H">Climate-driven variability in the occurrence of major floods across North America and Europe</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hodgkins, Glenn A.; Whitfield, Paul H.; Burn, Donald H.; Hannaford, Jamie; Renard, Benjamin; Stahl, Kerstin; Fleig, Anne K.; Madsen, Henrik; Mediero, Luis; Korhonen, Johanna; Murphy, Conor; Wilson, Donna 2017-09-01 Concern over the potential impact of anthropogenic climate change on flooding has led to a proliferation of studies examining past flood trends. Many studies have analysed annual-maximum flow trends but few have quantified changes in major (25-100 year return period) floods, i.e. those that have the greatest societal impacts. Existing major-flood studies used a limited number of very large catchments affected to varying degrees by alterations such as reservoirs and urbanisation. In the current study, trends in major-flood occurrence from 1961 to 2010 and from 1931 to 2010 were assessed using a very large dataset (>1200 gauges) of diverse catchments from North America and Europe; only minimally altered catchments were used, to focus on climate-driven changes rather than changes due to catchment alterations. Trend testing of major floods was based on counting the number of exceedances of a given flood threshold within a group of gauges. Evidence for significant trends varied between groups of gauges that were defined by catchment size, location, climate, flood threshold and period of record, indicating that generalizations about flood trends across large domains or a diversity of catchment types are ungrounded. Overall, the number of significant trends in major-flood occurrence across North America and Europe was approximately the number expected due to chance alone. Changes over time in the occurrence of major floods were dominated by multidecadal variability rather than by long-term trends. There were more than three times as many significant relationships between major-flood occurrence and the Atlantic Multidecadal Oscillation than significant long-term trends. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2328A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2328A">Stratospheric role in interdecadal changes of El Niño impacts over Europe</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ayarzagüena, B.; López-Parages, J.; Iza, M.; Calvo, N.; Rodríguez-Fonseca, B. 2018-04-01 The European precipitation response to El Niño (EN) has been found to present interdecadal changes, with alternated periods of important or negligible EN impact in late winter. These periods are associated with opposite phases of multi-decadal sea surface temperature (SST) variability, which modifies the tropospheric background and EN teleconnections. In addition, other studies have shown how SST anomalies in the equatorial Pacific, and in particular, the location of the largest anomalous SST, modulate the stratospheric response to EN. Nevertheless, the role of the stratosphere on the stationarity of EN response has not been investigated in detail so far. Using reanalysis data, we present a comprehensive study of EN teleconnections to Europe including the role of the ocean background and the stratosphere in the stationarity of the signal. The results reveal multidecadal variability in the location of EN-related SST anomalies that determines different teleconnections. In periods with relevant precipitation signal over Europe, the EN SST pattern resembles Eastern Pacific EN and the stratospheric pathway plays a key role in transmitting the signal to Europe in February, together with two tropospheric wavetrains that transmit the signal in February and April. Conversely, the stratospheric pathway is not detected in periods with a weak EN impact on European precipitation, corresponding to EN-related SST anomalies primarily located over the central Pacific. SST mean state and its associated atmospheric background control the location of EN-related SST anomalies in different periods and modulate the establishment of the aforementioned stratospheric pathway of EN teleconnection to Europe too. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://www.sciencedirect.com/science/article/pii/S002216941730478X','USGSPUBS'); return false;" href="http://www.sciencedirect.com/science/article/pii/S002216941730478X">Climate-driven variability in the occurrence of major floods across North America and Europe</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Hodgkins, Glenn A.; Whitfield, Paul H.; Burn, Donald H.; Hannaford, Jamie; Renard, Benjamin; Stahl, Kerstin; Fleig, Anne K.; Madsen, Henrik; Mediero, Luis; Korhonen, Johanna; Murphy, Conor; Wilson, Donna 2017-01-01 Concern over the potential impact of anthropogenic climate change on flooding has led to a proliferation of studies examining past flood trends. Many studies have analysed annual-maximum flow trends but few have quantified changes in major (25–100 year return period) floods, i.e. those that have the greatest societal impacts. Existing major-flood studies used a limited number of very large catchments affected to varying degrees by alterations such as reservoirs and urbanisation. In the current study, trends in major-flood occurrence from 1961 to 2010 and from 1931 to 2010 were assessed using a very large dataset (>1200 gauges) of diverse catchments from North America and Europe; only minimally altered catchments were used, to focus on climate-driven changes rather than changes due to catchment alterations. Trend testing of major floods was based on counting the number of exceedances of a given flood threshold within a group of gauges. Evidence for significant trends varied between groups of gauges that were defined by catchment size, location, climate, flood threshold and period of record, indicating that generalizations about flood trends across large domains or a diversity of catchment types are ungrounded. Overall, the number of significant trends in major-flood occurrence across North America and Europe was approximately the number expected due to chance alone. Changes over time in the occurrence of major floods were dominated by multidecadal variability rather than by long-term trends. There were more than three times as many significant relationships between major-flood occurrence and the Atlantic Multidecadal Oscillation than significant long-term trends. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28205603','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28205603">Influences of volcano eruptions on Asian Summer Monsoon over the last 110 years.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ning, Liang; Liu, Jian; Sun, Weiyi 2017-02-16 Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901-1935 and 1963-1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936-1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatSR...742626N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatSR...742626N">Influences of volcano eruptions on Asian Summer Monsoon over the last 110 years</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ning, Liang; Liu, Jian; Sun, Weiyi 2017-02-01 Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901-1935 and 1963-1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936-1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28550281','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28550281">Decadal Variations in Eastern Canada's Taiga Wood Biomass Production Forced by Ocean-Atmosphere Interactions.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Boucher, Etienne; Nicault, Antoine; Arseneault, Dominique; Bégin, Yves; Karami, Mehdi Pasha 2017-05-26 Across Eastern Canada (EC), taiga forests represent an important carbon reservoir, but the extent to which climate variability affects this ecosystem over decades remains uncertain. Here, we analyze an extensive network of black spruce (Picea mariana Mill.) ring width and wood density measurements and provide new evidence that wood biomass production is influenced by large-scale, internal ocean-atmosphere processes. We show that while black spruce wood biomass production is primarily governed by growing season temperatures, the Atlantic ocean conveys heat from the subtropics and influences the decadal persistence in taiga forests productivity. Indeed, we argue that 20-30 years periodicities in Sea Surface Temperatures (SSTs) as part of the the Atlantic Multi-decadal Oscillation (AMO) directly influence heat transfers to adjacent lands. Winter atmospheric conditions associated with the North Atlantic Oscillation (NAO) might also impact EC's taiga forests, albeit indirectly, through its effect on SSTs and sea ice conditions in surrounding seas. Our work emphasizes that taiga forests would benefit from the combined effects of a warmer atmosphere and stronger ocean-to-land heat transfers, whereas a weakening of these transfers could cancel out, for decades or longer, the positive effects of climate change on Eastern Canada's largest ecosystem. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4685260','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4685260">Sensitivity of proxies on non-linear interactions in the climate system</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Schultz, Johannes A.; Beck, Christoph; Menz, Gunter; Neuwirth, Burkhard; Ohlwein, Christian; Philipp, Andreas 2015-01-01 Recent climate change is affecting the earth system to an unprecedented extent and intensity and has the potential to cause severe ecological and socioeconomic consequences. To understand natural and anthropogenic induced processes, feedbacks, trends, and dynamics in the climate system, it is also essential to consider longer timescales. In this context, annually resolved tree-ring data are often used to reconstruct past temperature or precipitation variability as well as atmospheric or oceanic indices such as the North Atlantic Oscillation (NAO) or the Atlantic Multidecadal Oscillation (AMO). The aim of this study is to assess weather-type sensitivity across the Northern Atlantic region based on two tree-ring width networks. Our results indicate that nonstationarities in superordinate space and time scales of the climate system (here synoptic- to global scale, NAO, AMO) can affect the climate sensitivity of tree-rings in subordinate levels of the system (here meso- to synoptic scale, weather-types). This scale bias effect has the capability to impact even large multiproxy networks and the ability of these networks to provide information about past climate conditions. To avoid scale biases in climate reconstructions, interdependencies between the different scales in the climate system must be considered, especially internal ocean/atmosphere dynamics. PMID:26686001 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3641520','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3641520">Coralline algal Barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Hetzinger, S.; Halfar, J.; Zack, T.; Mecking, J. V.; Kunz, B. E.; Jacob, D. E.; Adey, W. H. 2013-01-01 During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes. PMID:23636135 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28317857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28317857">Enhanced biennial variability in the Pacific due to Atlantic capacitor effect.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wang, Lei; Yu, Jin-Yi; Paek, Houk 2017-03-20 The El Niño-Southern Oscillation (ENSO) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in ENSO and the PSHs during recent decades. The 'charging' (that is, ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and 'discharging' (that is, the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global warming trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard events. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23636135','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23636135">Coralline algal barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hetzinger, S; Halfar, J; Zack, T; Mecking, J V; Kunz, B E; Jacob, D E; Adey, W H 2013-01-01 During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5364382','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5364382">Enhanced biennial variability in the Pacific due to Atlantic capacitor effect</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wang, Lei; Yu, Jin-Yi; Paek, Houk 2017-01-01 The El Niño-Southern Oscillation (ENSO) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in ENSO and the PSHs during recent decades. The ‘charging' (that is, ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and ‘discharging' (that is, the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global warming trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard events. PMID:28317857 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007MAP....96...85N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007MAP....96...85N">Interannual variability of cut-off low systems over the European sector: The role of blocking and the Northern Hemisphere circulation modes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nieto, R.; Gimeno, L.; de La Torre, L.; Ribera, P.; Barriopedro, D.; García-Herrera, R.; Serrano, A.; Gordillo, A.; Redaño, A.; Lorente, J. 2007-04-01 An earlier developed multidecadal database of Northern Hemisphere cut-off low systems (COLs), covering a 41 years period (from 1958 to 1998) is used to study COLs interannual variability in the European sector (25°-47.5° N, 50° W-40° E) and the major factors controlling it. The study focus on the influence on COLs interannual variability, of larger scale phenomena such as blocking events and other main circulation modes defined over the Euro-Atlantic region. It is shown that there is a very large interannual variability in the COLs occurrence at the annual and seasonal scales, although without significant trends. The influence of larger scale phenomena is seasonal dependent, with the positive phase of the NAO favoring autumn COL development, while winter COL occurrence is mostly related to blocking events. During summer, the season when more COLs occur, no significant influences were found. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...814887W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...814887W">Enhanced biennial variability in the Pacific due to Atlantic capacitor effect</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, Lei; Yu, Jin-Yi; Paek, Houk 2017-03-01 The El Niño-Southern Oscillation (ENSO) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in ENSO and the PSHs during recent decades. The `charging' (that is, ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and `discharging' (that is, the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global warming trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard events. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5461504','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5461504">Multicentennial record of Labrador Sea primary productivity and sea-ice variability archived in coralline algal barium</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Chan, P.; Halfar, J.; Adey, W.; Hetzinger, S.; Zack, T.; Moore, G.W.K.; Wortmann, U. G.; Williams, B.; Hou, A. 2017-01-01 Accelerated warming and melting of Arctic sea-ice has been associated with significant increases in phytoplankton productivity in recent years. Here, utilizing a multiproxy approach, we reconstruct an annually resolved record of Labrador Sea productivity related to sea-ice variability in Labrador, Canada that extends well into the Little Ice Age (LIA; 1646 AD). Barium-to-calcium ratios (Ba/Ca) and carbon isotopes (δ13C) measured in long-lived coralline algae demonstrate significant correlations to both observational and proxy records of sea-ice variability, and show persistent patterns of co-variability broadly consistent with the timing and phasing of the Atlantic Multidecadal Oscillation (AMO). Results indicate reduced productivity in the Subarctic Northwest Atlantic associated with AMO cool phases during the LIA, followed by a step-wise increase from 1910 to present levels—unprecedented in the last 363 years. Increasing phytoplankton productivity is expected to fundamentally alter marine ecosystems as warming and freshening is projected to intensify over the coming century. PMID:28569839 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70178805','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70178805">Climate variability and extremes, interacting with nitrogen storage, amplify eutrophication risk</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Lee, Minjin; Shevliakova, Elena; Malyshev, Sergey; Milly, P.C.D.; Jaffe, Peter R. 2016-01-01 Despite 30 years of basin-wide nutrient-reduction efforts, severe hypoxia continues to be observed in the Chesapeake Bay. Here we demonstrate the critical influence of climate variability, interacting with accumulated nitrogen (N) over multidecades, on Susquehanna River dissolved nitrogen (DN) loads, known precursors of the hypoxia in the Bay. We used the process model LM3-TAN (Terrestrial and Aquatic Nitrogen), which is capable of capturing both seasonal and decadal-to-century changes in vegetation-soil-river N storage, and produced nine scenarios of DN-load distributions under different short-term scenarios of climate variability and extremes. We illustrate that after 1 to 3 yearlong dry spells, the likelihood of exceeding a threshold DN load (56 kt yr−1) increases by 40 to 65% due to flushing of N accumulated throughout the dry spells and altered microbial processes. Our analyses suggest that possible future increases in climate variability/extremes—specifically, high precipitation occurring after multiyear dry spells—could likely lead to high DN-load anomalies and hypoxia. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27382163','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27382163">Large scale, synchronous variability of marine fish populations driven by commercial exploitation.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Frank, Kenneth T; Petrie, Brian; Leggett, William C; Boyce, Daniel G 2016-07-19 Synchronous variations in the abundance of geographically distinct marine fish populations are known to occur across spatial scales on the order of 1,000 km and greater. The prevailing assumption is that this large-scale coherent variability is a response to coupled atmosphere-ocean dynamics, commonly represented by climate indexes, such as the Atlantic Multidecadal Oscillation and North Atlantic Oscillation. On the other hand, it has been suggested that exploitation might contribute to this coherent variability. This possibility has been generally ignored or dismissed on the grounds that exploitation is unlikely to operate synchronously at such large spatial scales. Our analysis of adult fishing mortality and spawning stock biomass of 22 North Atlantic cod (Gadus morhua) stocks revealed that both the temporal and spatial scales in fishing mortality and spawning stock biomass were equivalent to those of the climate drivers. From these results, we conclude that greater consideration must be given to the potential of exploitation as a driving force behind broad, coherent variability of heavily exploited fish species. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4495927','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4495927">Quantifying the Intra-Regional Precipitation Variability in Northwestern China over the Past 1,400 Years</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Lee, Harry F.; Pei, Qing; Zhang, David D.; Choi, Kan P. K. 2015-01-01 There has been a surge of paleo-climatic/environmental studies of Northwestern China (NW China), a region characterized by a diverse assortment of hydro-climatic systems. Their common approach, however, focuses on “deducing regional resemblance” rather than “exploring regional variance.” To date, efforts to produce a quantitative assessment of long-term intra-regional precipitation variability (IRPV) in NW China has been inadequate. In the present study, we base on historical flood/drought records to compile a decadal IRPV index for NW China spanned AD580–1979 and to find its major determinants via wavelet analysis. Results show that our IRPV index captures the footprints of internal hydro-climatic disparity in NW China. In addition, we find distinct ~120–200 year periodicities in the IRPV index over the Little Ice Age, which are attributable to the change of hydro-climatic influence of ocean-atmospheric modes during the period. Also, we offer statistical evidence of El Niño Southern Oscillation (Indo-Pacific warm pool sea surface temperature and China-wide land surface temperature) as the prominent multi-decadal to centennial (centennial to multi-centennial) determinant of the IRPV in NW China. The present study contributes to the quantitative validation of the long-term IRPV in NW China and its driving forces, covering the periods with and without instrumental records. It may help to comprehend the complex hydro-climatic regimes in the region. PMID:26154711 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP53D..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP53D..06P">Subtropical Climate Variability since the Last Glacial Maximum from Speleothem Precipitation Reconstructions in Florida</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Polk, J.; van Beynen, P.; DeLong, K. L.; Asmerom, Y.; Polyak, V. J. 2017-12-01 Teleconnections between the tropical-subtropical regions of the Americas since the Last Glacial Maximum (LGM), particularly the Mid- to Late-Holocene, and high-resolution proxy records refining climate variability over this period continue to receive increasing attention. Here, we present a high-resolution, precisely dated speleothem record spanning multiple periods of time since the LGM ( 30 ka) for the Florida peninsula. The data indicate that the amount effect plays a significant role in determining the isotopic signal of the speleothem calcite. Collectively, the records indicate distinct differences in climate in the region between the LGM, Mid-Holocene, and Late Holocene, including a progressive shift in ocean composition and precipitation isotopic values through the period, suggesting Florida's sensitivity to regional and global climatic shifts. Comparisons between speleothem δ18O values and Gulf of Mexico marine records reveal a strong connection between the Gulf region and the terrestrial subtropical climate in the Late Holocene, while the North Atlantic's influence is clear in the earlier portions of the record. Warmer sea surface temperatures correspond to enhanced evaporation, leading to more intense atmospheric convection in Florida, and thereby modulating the isotopic composition of rainfall above the cave. These regional signals in climate extend from the subtropics to the tropics, with a clear covariance between the speleothem signal and other proxy records from around the region, as well as global agreement during the LGM period with other records. These latter connections appear to be driven by changes in the mean position of the Intertropical Convergence Zone and time series analysis of the δ18O values reveals significant multidecadal periodicities in the record, which are evidenced by agreement with the AMV and other multidecadal influences (NAO and PDO) likely having varying influence throughout the period of record. The climate variability recorded in our record suggests complex responses to major and abrupt shifts during these periods, likely due to Florida's subtropical location and the influence of multiple climate forcing mechanisms in the region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GPC...151..122F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GPC...151..122F">Covariability of seasonal temperature and precipitation over the Iberian Peninsula in high-resolution regional climate simulations (1001-2099)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fernández-Montes, S.; Gómez-Navarro, J. J.; Rodrigo, F. S.; García-Valero, J. A.; Montávez, J. P. 2017-04-01 Precipitation and surface temperature are interdependent variables, both as a response to atmospheric dynamics and due to intrinsic thermodynamic relationships and feedbacks between them. This study analyzes the covariability of seasonal temperature (T) and precipitation (P) across the Iberian Peninsula (IP) using regional climate paleosimulations for the period 1001-1990, driven by reconstructions of external forcings. Future climate (1990-2099) was simulated according to SRES scenarios A2 and B2. These simulations enable exploring, at high spatial resolution, robust and physically consistent relationships. In winter, positive P-T correlations dominate west-central IP (Pearson correlation coefficient ρ = + 0.43, for 1001-1990), due to prevalent cold-dry and warm-wet conditions, while this relationship weakens and become negative towards mountainous, northern and eastern regions. In autumn, negative correlations appear in similar regions as in winter, whereas for summer they extend also to the N/NW of the IP. In spring, the whole IP depicts significant negative correlations, strongest for eastern regions (ρ = - 0.51). This is due to prevalent frequency of warm-dry and cold-wet modes in these regions and seasons. At the temporal scale, regional correlation series between seasonal anomalies of temperature and precipitation (assessed in 31 years running windows in 1001-1990) show very large multidecadal variability. For winter and spring, periodicities of about 50-60 years arise. The frequency of warm-dry and cold-wet modes appears correlated with the North Atlantic Oscillation (NAO), explaining mainly co-variability changes in spring. For winter and some regions in autumn, maximum and minimum P-T correlations appear in periods with enhanced meridional or easterly circulation (low or high pressure anomalies in the Mediterranean and Europe). In spring and summer, the Atlantic Multidecadal Oscillation shows some fingerprint on the frequency of warm/cold modes. For future scenarios, an intensification of the negative P-T relationship is generally found, as a result of an increased frequency of the warm-dry mode. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP51B..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP51B..02W">Reconstructing the history of the Atlantic Multidecadal Oscillation using high-resolution Mg/Ca paleothermometry from a Cariaco Basin core</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wurtzel, J. B.; Black, D. E.; Rahman, S.; Thunell, R.; Peterson, L. C.; Tappa, E. 2010-12-01 Instrumental and proxy-reconstructions show the existence of an approximately 70-year periodicity in Atlantic sea surface temperature (SST), known as the Atlantic Multidecadal Oscillation (AMO). The AMO is correlated with circum-tropical Atlantic climate phenomena such as Sahel and Nordeste rainfall, and Atlantic hurricane patterns. Though it has been suggested that the AMO is controlled by thermohaline circulation, much debate exists as to whether the SST fluctuations are a result of anthropogenic forcing or a natural climate mode, or even if the AMO is a true oscillation at all. Our ability to address this issue has been limited by instrumental SST records that rarely extend back more than 50-100 years and proxy reconstructions that are mostly terrestrial-based. Additionally, the modern instrumental variability likely contains an anthropogenic component that is not easily distinguished from the natural background of the system. From a marine sediment core taken in the Cariaco Basin, we have developed a high-resolution SST reconstruction for the past ca. 1500 years using Mg/Ca paleothermometry on seasonally-representative foraminifera, with the most recent data calibrated to the instrumental record. Previous studies have shown Cariaco Basin Mg/Ca-SSTs to be well-correlated to the Caribbean Sea and much of the western tropical Atlantic, which allows us to create a record that can be used to determine pre-anthropogenic rates and ranges of SST variability and observe how they change over time. Averaging the seasonal temperatures derived from the two foraminiferal species over the instrumental period yields a strong correlation to the AMO index from A. D. 1880 through 1970 (r = 0.44, p<0.0001). Wavelet analysis of the proxy average annual SST data indicates that modern AMO variability is not a consistent feature through time, and may be a function of warm-period climate. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H42C..03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H42C..03M">Investigating the Control of Ocean-Atmospheric Oscillations on Global Terrestrial Evaporation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Martens, B.; Waegeman, W.; Dorigo, W.; Verhoest, N.; Miralles, D. G. 2017-12-01 Intra-annual and multi-decadal variability in Earth's climate is strongly driven by periodic oscillations in the coupled state of our atmosphere and ocean. These oscillations do not only impact climate in nearby regions, but can also have an effect on the climate in remote areas, a phenomenon that is often referred to as teleconnection. Because changes in local climate immediately affect terrestrial ecosystems through a series of complex processes, ocean-atmospheric oscillations are expected to influence land evaporation; i.e. the return flux of water from land into the atmosphere. In this presentation, the effects of ocean-atmospheric oscillations on global terrestrial evaporation are analysed. We use multi-decadal, satellite-based observations of different climate variables (air temperature, radiation, precipitation) in combination with a simple supervised learning method - the Least Absolute Shrinkage and Selection Operator - to detect the impact of sixteen leading ocean-atmospheric oscillations on terrestrial evaporation. The latter is retrieved using the Global Land Evaporation Amsterdam Model (GLEAM). The analysis reveals hotspot regions in which more than 30% of the inter-annual variability in terrestrial evaporation can be explained by ocean-atmospheric oscillations. The impact is different per region and season, and can typically be attributed to a small subset of oscillations. For instance, the dynamics in terrestrial evaporation over eastern Australia are substantially impacted by both the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) during Austral spring. Using the same learning method, but targeting terrestrial evaporation based on its local climatic drivers (air temperature, precipitation, and radiation), shows the dominant control of precipitation on terrestrial evaporation in Australia, suggesting that both ENSO and IOD affect the precipitation, in his turn influencing evaporation. The latter is confirmed by regressing precipitation to the ocean-atmospheric oscillations. The results of our study allow for a better understanding of the link between ocean-atmosphere dynamics and terrestrial bio-geochemical cycles, and may help improve the prediction of future changes in the water cycle over the continents. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3458S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3458S">Two centuries of observed atmospheric variability and change over the North Sea region</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; van Oldenborgh, Geert Jan; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard 2015-04-01 Situated in northwestern Europe, the North Sea region is under influence of air masses from subtropical to arctic origin, and thus exhibits significant natural climate variability. As the land areas surrounding the North Sea are densely populated, climate change is an important issue in terms of e.g. coastal protection, fishery and trade. This study is part of the NOSCCA initiative (North Sea Region Climate Change Assessment) and presents observed variability and changes in atmospheric parameters during the last roughly 200 years. Circulation patterns show considerable decadal variability. In recent decades, a northward shift of storm tracks and increased cyclonic activity has been observed. There is also an indication of increased persistence of weather types. The wind climate is dominated by large multidecadal variability, and no robust long-term trends can be identified in the available datasets. There is a clear positive trend in near-surface temperatures, in particular during spring and winter. Over the region as a whole, no clear long-term precipitation trends are visible, although regional indications exist for an increased risk of extreme precipitation events. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThApC.127..533C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThApC.127..533C">Surface temperature dataset for North America obtained by application of optimal interpolation algorithm merging tree-ring chronologies and climate model output</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Xin; Xing, Pei; Luo, Yong; Nie, Suping; Zhao, Zongci; Huang, Jianbin; Wang, Shaowu; Tian, Qinhua 2017-02-01 A new dataset of surface temperature over North America has been constructed by merging climate model results and empirical tree-ring data through the application of an optimal interpolation algorithm. Errors of both the Community Climate System Model version 4 (CCSM4) simulation and the tree-ring reconstruction were considered to optimize the combination of the two elements. Variance matching was used to reconstruct the surface temperature series. The model simulation provided the background field, and the error covariance matrix was estimated statistically using samples from the simulation results with a running 31-year window for each grid. Thus, the merging process could continue with a time-varying gain matrix. This merging method (MM) was tested using two types of experiment, and the results indicated that the standard deviation of errors was about 0.4 °C lower than the tree-ring reconstructions and about 0.5 °C lower than the model simulation. Because of internal variabilities and uncertainties in the external forcing data, the simulated decadal warm-cool periods were readjusted by the MM such that the decadal variability was more reliable (e.g., the 1940-1960s cooling). During the two centuries (1601-1800 AD) of the preindustrial period, the MM results revealed a compromised spatial pattern of the linear trend of surface temperature, which is in accordance with the phase transition of the Pacific decadal oscillation and Atlantic multidecadal oscillation. Compared with pure CCSM4 simulations, it was demonstrated that the MM brought a significant improvement to the decadal variability of the gridded temperature via the merging of temperature-sensitive tree-ring records. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFMPP52A..06G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFMPP52A..06G">Paleo-environmental Perspectives on Climate-change Monitoring in the National Parks of the Northern U.S. Rocky Mountains</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gray, S. T.; Graumlich, L. J.; Pederson, G. T.; Fagre, D. B.; Betancourt, J. L.; Norris, J. R.; Jackson, S. T. 2004-12-01 In the face of growing visitation, encroaching development and a changing climate, the United States National Park Service has initiated a nationwide program to inventory and monitor the resources it protects. The foundation for this initiative lies in the development of baseline or reference datasets for physical and biological systems within each park unit. In a series of paleo-proxy studies from the Greater Yellowstone and Glacier National Park regions, we demonstrate that most instrumental and observational records are too short to capture a significant portion of the climatic and ecological variability that might be expected in the parks of the northern U.S. Rockies. Networks of tree-ring based temperature and precipitation reconstructions spanning the last ~1,000 yr demonstrate that the climates of these regions are not stationary. These climates are instead characterized by strong regime-like behavior over decadal to multidecadal timescales. Complimentary studies of past plant-community and landscape dynamics show how such lower-frequency variability can have a profound impact on vital park resources and amenities. In the eastern Yellowstone region, for example, persistent (20-30 yr) wet/cool periods in the 19th and early 20th centuries led to widespread recruitment of woody plants, and the legacy of these recruitment events still persists in the structure of many woodlands and forests. Studies of fossil packrat middens also suggest that at least some recent woody-plant encroachment and densification- a major management concern in the region- is related to plant late-Holocene plant migration dynamics and population processes rather than changing climate and land-use. Though the timing and effects of such events may differ, similar ecological responses to decadal/multidecadal climate variability are seen in the Glacier National Park region. In combination these studies serve to emphasize the need for careful selection of reference periods and baseline conditions used in climate-change monitoring, and this work shows the invaluable role that paleo-environmental archives can play in natural resource management. Overall, a more complete knowledge of long-duration ecological processes and lower-frequency climate variability should influence how we monitor and manage climate-change impacts throughout the northern Rockies. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/55518','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/55518">Multidecadal trends in area burned with high severity in the Selway-Bitterroot Wilderness Area 1880-2012</a> <a target="_blank" rel="noopener noreferrer" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Penelope Morgan; Andrew T. Hudak; Ashley Wells; Sean A. Parks; L. Scott Baggett; Benjamin C. Bright; Patricia Green 2017-01-01 Multidecadal trends in areas burned with high severity shape ecological effects of fires, but most assessments are limited to ~30 years of satellite data. We analysed the proportion of area burned with high severity, the annual area burned with high severity, the probability areas burned with high severity and also the area reburned (all severities and high burn... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/50826','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/50826">Multidecadal response of naturally regenerated southern pine to early competition control and commercial thinning</a> <a target="_blank" rel="noopener noreferrer" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Andrew S. Nelson; Don C. Bragg 2016-01-01 Multidecadal responses to early competition control are poorly documented in naturally regenerated southern pine stands. This study examined the effects of the followingÂ early herbicide treatments in thinned southern pine stands through age 31: (1) no control (CK), (2) herbaceous vegetation control only (HC), (3) woody vegetation controlÂ only (WC), and (4) total (woody... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160003522&hterms=churchill&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dchurchill','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160003522&hterms=churchill&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dchurchill">Combined Effect of El Nino Southern Oscillation and Atlantic Multidecadal Oscillation on Lake Chad Level Variability Region</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Okonkwo, Churchill; Demoz, Belay; Sakai, Ricardo; Ichoku, Charles; Anarado, Chigozie; Adegoke, Jimmy; Amadou, Angelina; Abdullahi, Sanusu Imran 2015-01-01 In this study, the combined effect of the Atlantic Multidecadal Oscillation (AMO) and El Niño Southern Oscillation (ENSO) on the Lake Chad (LC) level variability is explored. Our results show that the lake level at the Bol monitoring station has a statistically significant correlation with precipitation (R2 = 0.6, at the 99.5% confidence level). The period between the late 1960s and early 1970s marked a turning point in the response of the regional rainfall to climatic drivers, thereby severely affecting the LC level. Our results also suggest that the negative impact of the cold phase of AMO on Sahel precipitation masks and supersedes the positive effect of La Niña in the early the 1970s. The drop in the size of LC level from 282.5 m in the early 1960s to about 278.1 m in 1983/1984 was the largest to occur within the period of study (1900-2010) and coincides with the combined cold phase of AMO and strong El Niño phase of ENSO. Further analyses show that the current warm phase of AMO and increasing La Niña episodes appear to be playing a major role in the increased precipitation in the Sahel region. The LC level is responding to this increase in precipitation by a gradual recovery, though it is still below the levels of the 1960s. This understanding of the AMO-ENSO-rainfall-LC level association will help in forecasting the impacts of similar combined episodes in the future. These findings also have implications for long-term water resources management in the LC region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005IJCli..25.1715G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005IJCli..25.1715G">A mid-shelf, mean wave direction climatology for southeastern Australia, and its relationship to the El Niño - Southern Oscillation since 1878 A.D.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Goodwin, Ian D. 2005-11-01 Coastal systems behave on timescales from days to centuries. Shelf and coastal wave climatological data from the Tasman Sea are only available for the past few decades. Hence, the records are too short to investigate inter- and multidecadal variability and their impact on coastal systems. A method is presented to hindcast monthly mid-shelf mean wave direction (MWD) for southeastern Australia, based on the monthly, trans-Tasman mean sea-level pressure (MSLP) difference between northern NSW (Yamba) and the north island of New Zealand (Auckland). The MSLP index is calibrated to instrumental (Waverider buoy) MWD data for the Sydney shelf and coast. Positive/negative trans-Tasman MSLP difference is significantly correlated to southerly/easterly Sydney MWD, and to long/short mean wave periods. The 124-year Sydney annual (MWD) time series displays multidecadal variability, and identifies a significant period of more southerly annual MWD during 1884 to 1914 than in the period since 1915. The Sydney MWD is significantly correlated to the Southern Oscillation Index (SOI). The correlation with the SOI is enhanced during periods when the Interdecadal Pacific Oscillation (IPO) is in its negative state and warm SST anomalies occur in the southwest Pacific region. The Sydney MWD was found to be associated with Pacific basin-wide climate fluctuations associated with the El Niño-Southern Oscillation (ENSO). Southerly/easterly Sydney MWD is correlated with low/high MSLP anomalies over New Zealand and the central Pacific Ocean. Southerly/easterly Sydney MWD is also correlated with cool/warm SST anomalies in the southwest Pacific, particularly in the eastern Coral Sea and Tasman Sea. Copyright </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011844','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011844">Pan-Continental Droughts in North America over the Last Millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Cook, Benjamin I.; Smerdon, Jason E.; Seager, Richard; Cook, Edward R. 2014-01-01 Regional droughts are common in North America, but pan-continental droughts extending across multiple regions, including the 2012 event, are rare relative to single-region events. Here, the tree-ring-derived North American Drought Atlas is used to investigate drought variability in four regions over the last millennium, focusing on pan-continental droughts. During the Medieval Climate Anomaly (MCA), the central plains (CP), Southwest (SW), and Southeast (SE) regions experienced drier conditions and increased occurrence of droughts and the Northwest (NW) experienced several extended pluvials. Enhanced MCA aridity in the SW and CP manifested as multidecadal megadroughts. Notably, megadroughts in these regions differed in their timing and persistence, suggesting that they represent regional events influenced by local dynamics rather than a unified, continental-scale phenomena. There is no trend in pan-continental drought occurrence, defined as synchronous droughts in three or more regions. SW, CP, and SE (SW+CP+SE) droughts are the most common, occurring in 12 percent of all years and peaking in prevalence during the twelfth and thirteenth centuries; patterns involving three other regions occur in about 8 percent of years. Positive values of the Southern Oscillation index (La Nina conditions) are linked to SW, CP, and SE (SW+CP+SE) droughts and SW, CP, and NW (SW+CP+NW) droughts, whereas CP, NW, and SE (CP+NW+SE) droughts are associated with positive values of the Pacific decadal oscillation and Atlantic multidecadal oscillation. While relatively rare, pan-continental droughts are present in the paleo record and are linked to defined modes of climate variability, implying the potential for seasonal predictability. Assuming stable drought teleconnections, these events will remain an important feature of future North American hydroclimate, possibly increasing in their severity in step with other expected hydroclimate responses to increased greenhouse gas forcing. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7217U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7217U">Links between North Atlantic atmospheric blocking and recent trends in European winter precipitation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ummenhofer, Caroline; Seo, Hyodae; Kwon, Young-Oh; Joyce, Terrence 2015-04-01 European precipitation has sustained robust trends during wintertime (January - March) over recent decades. Central, western, and northern Europe have become wetter by an average 0.1-0.3% per annum for the period 1901-2010, while southern Europe, including the Iberian Peninsula, much of Italy and the Balkan States, has sustained drying of -0.2% per annum or more over the same period. The overall pattern is consistent across different observational precipitation products, while the magnitude of the precipitation trends varies amongst data sets. Using cluster analysis, which identifies recurrent states (or regimes) of European winter precipitation by grouping them according to an objective similarity criterion, changes in the frequency of dominant winter precipitation patterns over the past century are evaluated. Considerable multi-decadal variability exists in the frequency of dominant winter precipitation patterns: more recent decades are characterised by significantly fewer winters with anomalous wet conditions over southern, western, and central Europe. In contrast, winters with dry conditions in western and southern Europe, but above-average rainfall in western Scandinavia and the northern British Isles, have been more common recently. We evaluate the associated multi-decadal large-scale circulation changes across the broader extratropical North Atlantic region, which accompany the observed wintertime precipitation variability using the 20th Century reanalysis product. Some influence of the North Atlantic Oscillation (NAO) is apparent in modulating the frequency of dominant precipitation patterns. However, recent trends in the characteristics of atmospheric blocking across the North Atlantic sector indicate a change in the dominant blocking centres (near Greenland, the British Isles, and west of the Iberian Peninsula). Associated changes in sea level pressure, storm track position and strength, and oceanic heat fluxes across the North Atlantic region are also addressed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPC14E2102M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPC14E2102M">Global decadal climate variability driven by Southern Ocean convection</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Marinov, I.; Cabre, A. 2016-02-01 Here we suggest a set of new "teleconnections" by which the Southern Ocean (SO) can induce anomalies in the tropical oceans and atmosphere. A 5000-year long control simulation in a coupled atmosphere-ocean model (CM2Mc, a low-resolution GFDL model) shows a natural, highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process happens naturally, with different frequencies and durations of convection across the majority of CMIP5 under preindustrial forcing (deLavergne et al., 2014). In our model, oscillations in Weddell Sea convection drive multidecadal variability in SO and global SSTs, as well as SO heat storage, with convective decades warm due to the heat released from the Circumpolar Deep Water and non-convective decades cold due to subsurface heat storage. Convective pulses drive local SST and sea ice variations south of 60S, immediately triggering changes in the Ferrell and Hadley cells, atmospheric energy budget and cross-equatorial heat exchange, ultimately influencing the position of the Intertropical Convergence Zone and rain patterns in the tropics. Additionally, the SO convection pulse is propagated to the tropics and the North Atlantic MOC via oceanic pathways on relatively fast (decadal) timescales, in agreement with recent observational constraints. Open sea convection is the major mode of Antarctic Bottom Water (AABW) formation in the CMIP5 models. Future improvements in the representation of shelf convection and sea-ice interaction in the SO are a clear necessity. These model improvements should render the AABW representation more realistic, and might influence (a) the connectivity of the SO with the rest of the planet, as described above and (b) the oceanic and global carbon cycle, of which the AABW is a fundamental conduit. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMS...133...77F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMS...133...77F">Differential response of continental stock complexes of Atlantic salmon (Salmo salar) to the Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Friedland, Kevin D.; Shank, Burton V.; Todd, Christopher D.; McGinnity, Philip; Nye, Janet A. 2014-05-01 Atlantic salmon, Salmo salar, in the North Atlantic are managed as a set of population complexes distributed in North America and Europe. In recent years, these complexes have experienced reduced marine survival and many populations within the complexes are at risk, especially those at the southern ends of the species amphi-Atlantic range. Atlantic salmon is an anadromous fish dividing its life history between residence in freshwater and the marine environment. The freshwater portion of the life history includes spawning and the rearing of juveniles where in-river production has tended to be relatively stable, whereas the first year at sea, termed the post-smolt year, is characterized by more variable rates of mortality. Although their habitats are widely separated geographically along the North Atlantic seaboards, strong recruitment coherence exists between North American and European stock complexes. This recruitment coherence is correlated with ocean temperature variation associated with the Atlantic Multidecadal Oscillation (AMO). The North Atlantic Oscillation (NAO) appears to be relatively unimportant as a driver of salmon abundance. The mechanism determining the link between AMO-related thermal variation and abundance appears to differ fundamentally for the two continental stock groupings. Whereas ocean climate variability during the first springtime months of juvenile salmon migration to sea appears to be important to the survival of North American stocks, summer climate variation appears to be central to adult recruitment variation for European stocks. This contrast in seasonal effects appears to be related to the varying roles of predation pressure and size-related mortality on the continental stock complexes. The anticipated warming due to global climate change will impose thermal conditions on salmon populations outside historical context and challenge the ability of many populations to persist. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP51A2286H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP51A2286H">The impact of AMO and NAO in Western Iberia during the Late Holocene</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hernandez, A.; Leira, M.; Trigo, R.; Vázquez-Loureiro, D.; Carballeira, R.; Sáez, A. 2016-12-01 High mountain lakes in the Iberian Peninsula are particularly sensitive to the influence of North Atlantic large-scale modes of climate variability due to their geographical position and the reduced anthropic disturbances. In this context, Serra da Estrela (Portugal), the westernmost range of the Sistema Central, constitutes a physical barrier to air masses coming from the Atlantic Ocean. However, long-term climate reconstructions have not yet been conducted. We present a climate reconstruction of this region based on facies analysis, X-ray fluorescence core scanning, elemental and isotope geochemistry on bulk organic matter and a preliminary study of diatom assemblages from the sedimentary record of Lake Peixão (1677 m a.s.l.; Serra da Estrela) for the last ca. 3500 years. A multivariate statistical analysis has been performed to recognize the main environmental factors controlling the sedimentary infill. Our results reveal that two main processes explain the 70% of the total variance. Thus, changes in primary productivity, reflected in organic matter accumulation, and variations in runoff, related to external particles input, explain 53% and 17% respectively. Additionally, evidence of changes in productivity and water level regime recorded as variations in diatom assemblages correlate well with our interpretations. A comparison between the lake productivity changes and previous Atlantic Multidecadal Oscillation (AMO) reconstructions shows a good correlation, suggesting this climate mode as the main driver over lacustrine primary productivity at multi-decadal scales. In turn, changes in terrigenous inputs, linked to precipitation, seem to be more influenced by the winter North Atlantic Oscillation (NAO) variability. Hence, our results highlight that although the climate regime in this area is clearly influenced by the NAO, the AMO also plays a key role at long-term time-scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3611S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3611S">Abrupt aridities in the Levant-Sahel linked with solar activities</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stein, M.; Kushnir, Y. 2012-04-01 Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan Sahel and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea and Sahelian lake levels and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the Sahel and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an antiphase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However, the records are punctuated by abrupt lake-level drops and extensive expansion of the desert belt at ~8.1, 5.7, 3.3 and 1.4 ka cal BP, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We link these cooling to solar activity variations that were identified in the North Atlantic IRD and cosmogenic isotopes records. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.3627W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.3627W">Variability of tropical cyclone rapid intensification in the North Atlantic and its relationship with climate variations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, Chunzai; Wang, Xidong; Weisberg, Robert H.; Black, Michael L. 2017-12-01 The paper uses observational data from 1950 to 2014 to investigate rapid intensification (RI) variability of tropical cyclones (TCs) in the North Atlantic and its relationships with large-scale climate variations. RI is defined as a TC intensity increase of at least 15.4 m/s (30 knots) in 24 h. The seasonal RI distribution follows the seasonal TC distribution, with the highest number in September. Although an RI event can occur anywhere over the tropical North Atlantic (TNA), there are three regions of maximum RI occurrence: (1) the western TNA of 12°N-18°N and 60°W-45°W, (2) the Gulf of Mexico and the western Caribbean Sea, and (3) the open ocean southeast and east of Florida. RI events also show a minimum value in the eastern Caribbean Sea north of South America—a place called a hurricane graveyard due to atmospheric divergence and subsidence. On longer time scales, RI displays both interannual and multidecadal variability, but RI does not show a long-term trend due to global warming. The top three climate indices showing high correlations with RI are the June-November ENSO and Atlantic warm pool indices, and the January-March North Atlantic oscillation index. It is found that variabilities of vertical wind shear and TC heat potential are important for TC RI in the hurricane main development region, whereas relative humidity at 500 hPa is the main factor responsible for TC RI in the eastern TNA. However, the large-scale oceanic and atmospheric variables analyzed in this study do not show an important role in TC RI in the Gulf of Mexico and the open ocean southeast and east of Florida. This suggests that other factors such as small-scale changes of oceanic and atmospheric variables or TC internal processes may be responsible for TC RI in these two regions. Additionally, the analyses indicate that large-scale atmospheric and oceanic variables are not critical to TC genesis and formation; however, once a tropical depression forms, large-scale climate variations play a role in TC intensification. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.7410L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.7410L">Tree ring reconstructed rainfall over the southern Amazon Basin</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lopez, Lidio; Stahle, David; Villalba, Ricardo; Torbenson, Max; Feng, Song; Cook, Edward 2017-07-01 Moisture sensitive tree ring chronologies of Centrolobium microchaete have been developed from seasonally dry forests in the southern Amazon Basin and used to reconstruct wet season rainfall totals from 1799 to 2012, adding over 150 years of rainfall estimates to the short instrumental record for the region. The reconstruction is correlated with the same atmospheric variables that influence the instrumental measurements of wet season rainfall. Anticyclonic circulation over midlatitude South America promotes equatorward surges of cold and relatively dry extratropical air that converge with warm moist air to form deep convection and heavy rainfall over this sector of the southern Amazon Basin. Interesting droughts and pluvials are reconstructed during the preinstrumental nineteenth and early twentieth centuries, but the tree ring reconstruction suggests that the strong multidecadal variability in instrumental and reconstructed wet season rainfall after 1950 may have been unmatched since 1799. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..216V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..216V">600 yr High-Resolution Climate Reconstruction of the Atlantic Multidecadal Oscillation deduced from a Puerto Rican Speleothem</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vieten, Rolf; Winter, Amos; Scholz, Denis; Black, David; Spoetl, Christoph; Winterhalder, Sophie; Koltai, Gabriella; Schroeder-Ritzrau, Andrea; Terzer, Stefan; Zanchettin, Davide; Mangini, Augusto 2016-04-01 A multi-proxy speleothem study tracks the regional hydrological variability in Puerto Rico and highlights its close relation to the Atlantic Multidecadal Oscillation (AMO) describing low-frequency sea-surface temperature (SST) variability in the North Atlantic ocean. Our proxy record extends instrumental observations 600 years into the past, and reveals the range of natural hydrologic variability for the region. A detailed interpretation and understanding of the speleothem climate record is achieved by the combination of multi-proxy measurements, thin section petrography, XRD analysis and cave monitoring results. The speleothem was collected in Cueva Larga, a one mile-long cave system that has been monitored since 2012. MC-ICPMS 230Th/U-dating reveals that the speleothem grew constantly over the last 600 years. Trace element ratios (Sr/Ca and Mg/Ca) as well as stable isotope ratios (δ18O and δ13C) elucidate significant changes in atmospheric precipitation at the site. Monthly cave monitoring results demonstrate that the epikarst system responds to multi-annual changes in seepage water recharge. The drip water isotope and trace element composition lack short term or seasonal variability. This hydrological system creates favorable conditions to deduce decadal climate variability from Cueva Larga's climate record. The speleothem time series mimics the most recent AMO reconstruction over the last 200 years (Svendsen et al., 2014) with a time lag of 10-20 years. The lag seems to results from slow atmospheric signal transmission through the epikarst but the effect of dating uncertainties cannot be ruled out. Warm SSTs in the North Atlantic are related to drier conditions in Puerto Rico. During times of decreased rainfall a relative increase in prior calcite precipitation seems to be the main process causing increased Mg/Ca trace element ratios. High trace element ratios correlate to higher δ13C values. The increase in both proxies indicates a shift towards time periods of decreased rainfall. Before 1800 there were two intervals of increased Mg/Ca and δ13C values (dryer conditions) lasting several decades in our speleothem record centered around 1680 CE and 1470 CE. The elevated ratios indicate that drier conditions than present may have occurred in the region during periods of warm Atlantic surface waters. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP51A2263W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP51A2263W">600 yr High-Resolution Climate Reconstruction of the Atlantic Multidecadal Variability deduced from a Puerto Rican Speleothem</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Winter, A.; Vieten, R. 2015-12-01 A multi-proxy speleothem study tracks the regional hydrological variability in Puerto Rico and highlights its close relation to the Atlantic Multidecadal Oscillation. Our proxy record extends instrumental observations 600 years into the past, and reveals the range of natural hydrologic variability for the region. A detailed interpretation and understanding of the speleothem climate record is achieved by the combination of multi-proxy measurements, thin section petrography, XRD analysis and cave monitoring results. The speleothem was collected in Cueva Larga, a one mile-long cave system that has been monitored since 2012. MC-ICPMS 230Th/U-dating reveals that the speleothem grew constantly over the last 600 years. Trace element ratios (Sr/Ca and Mg/Ca) as well as stable isotope ratios (δ18O and δ13C) elucidate significant changes in atmospheric precipitation at the site. Monthly cave monitoring results demonstrate that the epikarst system responds to multi-annual changes in seepage water recharge. The drip water isotope and trace element composition lack short term or seasonal variability. This hydrological system creates favorable conditions to deduce decadal climate variability from Cueva Larga's climate record. The speleothem time series mimics the most-recently published AMO reconstruction over the last 200 years with a time lag of 10-20 years. The time lag seems to results from slow atmospheric signal transmission through the epikarst but the effect of dating uncertainties cannot be ruled out. Warm SSTs in the North Atlantic are related to drier conditions in Puerto Rico. During times of decreased rainfall a relative increase in prior calcite precipitation seems to be the main process causing increased Mg/Ca trace element ratios. High trace element ratios correlate to higher δ13C values. The increase in both proxies indicates a shift towards time periods of decreased rainfall. Over the past 600 years there are two intervals of increased Mg/Ca and δ13C values lasting several decades in our speleothem record. They are centered around 1680 CE and 1470 CE. The elevated ratios indicate that drier conditions than present occurred in the region during periods of warm Atlantic surface waters. This may be a precursor of conditions now and to come. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7862M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7862M">North Atlantic early 20th century warming and impact on European summer: Mechanisms and Predictability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Müller, Wolfgang 2017-04-01 During the last century, substantial climate variations in the North Atlantic have occurred, such as the warmings in the 1920s and 1990s. Such variations are considered to be part of the variability known as the Atlantic Multidecadal Variations (AMV) and have a strong impact on local climates such as European summers. Here a synthesis of previous works is presented which describe the occurrence of the warming in the 1920s in the North Atlantic and its impact on the European summer climate (Müller et al. 2014, 2015). For this the 20th century reanalysis (20CR) and 20CR forced ocean experiments are evaluated. It can be shown that the North Atlantic Current and Sub-Polar Gyre are strengthened as a result of an increased pressure gradient over the North Atlantic. Concurrently, Labrador Sea convection and Atlantic meridional overturning circulation (AMOC) increase. The intensified NAC, SPG, and AMOC redistribute sub-tropical water into the North Atlantic and Nordic Seas, thereby increasing observed and modelled temperature and salinity during the 1920s. Further a mechanism is proposed by which North Atlantic heat fluxes associated with the AMV modulate European decadal summer climate (Ghosh et al. 2016). By using 20CR, it can be shown that multi-decadal variations in the European summer temperature are associated to a linear baroclinic atmospheric response to the AMV-related surface heat flux. This response induce a sea level pressure structure modulating meridional temperature advection over north-western Europe and Blocking statistics over central Europe. This structure is shown to be the leading mode of variability and is independent of the summer North Atlantic Oscillation. Ghosh, R., W.A. Müller, J. Bader, and J. Baehr, 2016: Impact of observed North Atlantic multidecadal variations to European summer climate: A linear baroclinic response to surface heating. Clim. Dyn. doi:10.10007/s00382-016-3283-4 Müller W. A., D. Matei, M. Bersch, J. H. Jungclaus, H. Haak, K. Lohmann,G. P. Compo, and J. Marotzke, 2015: A 20th-century reanalysis forced ocean model to reconstruct North Atlantic climate variation during the 1920s, Climate Dynamics. doi:10.1007/s00382-014-2267-5 Müller, W. A., H. Pohlmann, F. Sienz, and D. Smith, 2014: Decadal climate prediction for the period 1901-2010 with a coupled climate model. Geophys. Res. Lett., 41, pp 2100-2107. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2342S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2342S">Contrasting spatial structures of Atlantic Multidecadal Oscillation between observations and slab ocean model simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sun, Cheng; Li, Jianping; Kucharski, Fred; Xue, Jiaqing; Li, Xiang 2018-04-01 The spatial structure of Atlantic multidecadal oscillation (AMO) is analyzed and compared between the observations and simulations from slab ocean models (SOMs) and fully coupled models. The observed sea surface temperature (SST) pattern of AMO is characterized by a basin-wide monopole structure, and there is a significantly high degree of spatial coherence of decadal SST variations across the entire North Atlantic basin. The observed SST anomalies share a common decadal-scale signal, corresponding to the basin-wide average (i. e., the AMO). In contrast, the simulated AMO in SOMs (AMOs) exhibits a tripole-like structure, with the mid-latitude North Atlantic SST showing an inverse relationship with other parts of the basin, and the SOMs fail to reproduce the observed strong spatial coherence of decadal SST variations associated with the AMO. The observed spatial coherence of AMO SST anomalies is identified as a key feature that can be used to distinguish the AMO mechanism. The tripole-like SST pattern of AMOs in SOMs can be largely explained by the atmosphere-forced thermodynamics mechanism due to the surface heat flux changes associated with the North Atlantic Oscillation (NAO). The thermodynamic forcing of AMOs by the NAO gives rise to a simultaneous inverse NAO-AMOs relationship at both interannual and decadal timescales and a seasonal phase locking of the AMOs variability to the cold season. However, the NAO-forced thermodynamics mechanism cannot explain the observed NAO-AMO relationship and the seasonal phase locking of observed AMO variability to the warm season. At decadal timescales, a strong lagged relationship between NAO and AMO is observed, with the NAO leading by up to two decades, while the simultaneous correlation of NAO with AMO is weak. This lagged relationship and the spatial coherence of AMO can be well understood from the view point of ocean dynamics. A time-integrated NAO index, which reflects the variations in Atlantic meridional overturning circulation (AMOC) and northward ocean heat transport caused by the accumulated effect of NAO forcing, reasonably well captures the observed multidecadal fluctuations in the AMO. Further analysis using the fully coupled model simulations provides direct modeling evidence that the observed spatial coherence of decadal SST variations across North Atlantic basin can be reproduced only by including the AMOC-related ocean dynamics, and the AMOC acts as a common forcing signal that results in a spatially coherent variation of North Atlantic SST. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...713502R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...713502R">Annually resolved North Atlantic marine climate over the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Reynolds, D. J.; Scourse, J. D.; Halloran, P. R.; Nederbragt, A. J.; Wanamaker, A. D.; Butler, P. G.; Richardson, C. A.; Heinemeier, J.; Eiríksson, J.; Knudsen, K. L.; Hall, I. R. 2016-12-01 Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ18O archive. We interpret our record of oxygen isotope ratios from the shells of the long-lived marine bivalve Arctica islandica (δ18O-shell), from the North Icelandic shelf, in relation to seawater density variability and demonstrate that solar and volcanic forcing coupled with ocean circulation dynamics are key drivers of climate variability over the last millennium. During the pre-industrial period (AD 1000-1800) variability in the sub-polar North Atlantic leads changes in Northern Hemisphere surface air temperatures at multi-decadal timescales, indicating that North Atlantic Ocean dynamics played an active role in modulating the response of the atmosphere to solar and volcanic forcing. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JASTP..90....9K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JASTP..90....9K">Climate sensitivity to the lower stratospheric ozone variations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kilifarska, N. A. 2012-12-01 The strong sensitivity of the Earth's radiation balance to variations in the lower stratospheric ozone—reported previously—is analysed here by the use of non-linear statistical methods. Our non-linear model of the land air temperature (T)—driven by the measured Arosa total ozone (TOZ)—explains 75% of total variability of Earth's T variations during the period 1926-2011. We have analysed also the factors which could influence the TOZ variability and found that the strongest impact belongs to the multi-decadal variations of galactic cosmic rays. Constructing a statistical model of the ozone variability, we have been able to predict the tendency in the land air T evolution till the end of the current decade. Results show that Earth is facing a weak cooling of the surface T by 0.05-0.25 K (depending on the ozone model) until the end of the current solar cycle. A new mechanism for O3 influence on climate is proposed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ERL....10f4002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ERL....10f4002D">The impact of monsoon intraseasonal variability on renewable power generation in India</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dunning, C. M.; Turner, A. G.; Brayshaw, D. J. 2015-06-01 India is increasingly investing in renewable technology to meet rising energy demands, with hydropower and other renewables comprising one-third of current installed capacity. Installed wind-power is projected to increase 5-fold by 2035 (to nearly 100GW) under the International Energy Agency's New Policies scenario. However, renewable electricity generation is dependent upon the prevailing meteorology, which is strongly influenced by monsoon variability. Prosperity and widespread electrification are increasing the demand for air conditioning, especially during the warm summer. This study uses multi-decadal observations and meteorological reanalysis data to assess the impact of intraseasonal monsoon variability on the balance of electricity supply from wind-power and temperature-related demand in India. Active monsoon phases are characterized by vigorous convection and heavy rainfall over central India. This results in lower temperatures giving lower cooling energy demand, while strong westerly winds yield high wind-power output. In contrast, monsoon breaks are characterized by suppressed precipitation, with higher temperatures and hence greater demand for cooling, and lower wind-power output across much of India. The opposing relationship between wind-power supply and cooling demand during active phases (low demand, high supply) and breaks (high demand, low supply) suggests that monsoon variability will tend to exacerbate fluctuations in the so-called demand-net-wind (i.e., electrical demand that must be supplied from non-wind sources). This study may have important implications for the design of power systems and for investment decisions in conventional schedulable generation facilities (such as coal and gas) that are used to maintain the supply/demand balance. In particular, if it is assumed (as is common) that the generated wind-power operates as a price-taker (i.e., wind farm operators always wish to sell their power, irrespective of price) then investors in conventional facilities will face additional weather-volatility through the monsoonal impact on the length and frequency of production periods (i.e. their load-duration curves). </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29769593','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29769593">East Asian warm season temperature variations over the past two millennia.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhang, Huan; Werner, Johannes P; García-Bustamante, Elena; González-Rouco, Fidel; Wagner, Sebastian; Zorita, Eduardo; Fraedrich, Klaus; Jungclaus, Johann H; Ljungqvist, Fredrik Charpentier; Zhu, Xiuhua; Xoplaki, Elena; Chen, Fahu; Duan, Jianping; Ge, Quansheng; Hao, Zhixin; Ivanov, Martin; Schneider, Lea; Talento, Stefanie; Wang, Jianglin; Yang, Bao; Luterbacher, Jürg 2018-05-16 East Asia has experienced strong warming since the 1960s accompanied by an increased frequency of heat waves and shrinking glaciers over the Tibetan Plateau and the Tien Shan. Here, we place the recent warmth in a long-term perspective by presenting a new spatially resolved warm-season (May-September) temperature reconstruction for the period 1-2000 CE using 59 multiproxy records from a wide range of East Asian regions. Our Bayesian Hierarchical Model (BHM) based reconstructions generally agree with earlier shorter regional temperature reconstructions but are more stable due to additional temperature sensitive proxies. We find a rather warm period during the first two centuries CE, followed by a multi-century long cooling period and again a warm interval covering the 900-1200 CE period (Medieval Climate Anomaly, MCA). The interval from 1450 to 1850 CE (Little Ice Age, LIA) was characterized by cooler conditions and the last 150 years are characterized by a continuous warming until recent times. Our results also suggest that the 1990s were likely the warmest decade in at least 1200 years. The comparison between an ensemble of climate model simulations and our summer reconstructions since 850 CE shows good agreement and an important role of internal variability and external forcing on multi-decadal time-scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5311988','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5311988">Influences of volcano eruptions on Asian Summer Monsoon over the last 110 years</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ning, Liang; Liu, Jian; Sun, Weiyi 2017-01-01 Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901–1935 and 1963–1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936–1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM. PMID:28205603 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4411201W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4411201W">A Census of Atmospheric Variability From Seconds to Decades</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Williams, Paul D.; Alexander, M. Joan; Barnes, Elizabeth A.; Butler, Amy H.; Davies, Huw C.; Garfinkel, Chaim I.; Kushnir, Yochanan; Lane, Todd P.; Lundquist, Julie K.; Martius, Olivia; Maue, Ryan N.; Peltier, W. Richard; Sato, Kaoru; Scaife, Adam A.; Zhang, Chidong 2017-11-01 This paper synthesizes and summarizes atmospheric variability on time scales from seconds to decades through a phenomenological census. We focus mainly on unforced variability in the troposphere, stratosphere, and mesosphere. In addition to atmosphere-only modes, our scope also includes coupled modes, in which the atmosphere interacts with the other components of the Earth system, such as the ocean, hydrosphere, and cryosphere. The topics covered include turbulence on time scales of seconds and minutes, gravity waves on time scales of hours, weather systems on time scales of days, atmospheric blocking on time scales of weeks, the Madden-Julian Oscillation on time scales of months, the Quasi-Biennial Oscillation and El Niño-Southern Oscillation on time scales of years, and the North Atlantic, Arctic, Antarctic, Pacific Decadal, and Atlantic Multidecadal Oscillations on time scales of decades. The paper serves as an introduction to a special collection of Geophysical Research Letters on atmospheric variability. We hope that both this paper and the collection will serve as a useful resource for the atmospheric science community and will act as inspiration for setting future research directions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70059128','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70059128">Impact of climate variability on runoff in the north-central United States</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ryberg, Karen R.; Lin, Wei; Vecchia, Aldo V. 2014-01-01 Large changes in runoff in the north-central United States have occurred during the past century, with larger floods and increases in runoff tending to occur from the 1970s to the present. The attribution of these changes is a subject of much interest. Long-term precipitation, temperature, and streamflow records were used to compare changes in precipitation and potential evapotranspiration (PET) to changes in runoff within 25 stream basins. The basins studied were organized into four groups, each one representing basins similar in topography, climate, and historic patterns of runoff. Precipitation, PET, and runoff data were adjusted for near-decadal scale variability to examine longer-term changes. A nonlinear water-balance analysis shows that changes in precipitation and PET explain the majority of multidecadal spatial/temporal variability of runoff and flood magnitudes, with precipitation being the dominant driver. Historical changes in climate and runoff in the region appear to be more consistent with complex transient shifts in seasonal climatic conditions than with gradual climate change. A portion of the unexplained variability likely stems from land-use change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..748C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..748C">Pacific-North American teleconnection and North Pacific Oscillation: historical simulation and future projection in CMIP5 models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Zheng; Gan, Bolan; Wu, Lixin; Jia, Fan 2017-09-01 Based on reanalysis datasets and as many as 35 CMIP5 models, this study evaluates the capability of climate models to simulate the spatiotemporal features of Pacific-North American teleconnection (PNA) and North Pacific Oscillation (NPO) in the twentieth century wintertime, and further investigates their responses to greenhouse warming in the twenty-first century. Analysis reveals that while the majority (80%) of models reasonably simulate either the geographical distribution or the amplitude of PNA/NPO pattern, only half of models can well capture both features in space. As for the temporal features, variabilities of PNA and NPO in most models are biased toward higher amplitude. Additionally, most models simulate the interannual variabilities of PNA and NPO, qualitatively consistent with the observation, whereas models generally lack the capability to reproduce the decadal (20-25 years) variability of PNA. As the climate warms under the strongest future warming scenario, the PNA intensity is found to be strengthened, whereas there is no consensus on the direction of change in the NPO intensity among models. The intensification of positive PNA is primarily manifested in the large deepening of the North Pacific trough, which is robust as it is 2.3 times the unforced internal variability. By focusing on the tropical Pacific Ocean, we find that the multidecadal evolution of the North Pacific trough intensity (dominating the PNA intensity evolution) is closely related to that of the analogous trough in the PNA-like teleconnection forced by sea surface temperature anomalies (SSTa) in the tropical central Pacific (CP) rather than the tropical eastern Pacific (EP). Such association is also found to act under greenhouse warming: that is, the strengthening of the PNA-like teleconnection induced by the CP SSTa rather than the EP SSTa is a driving force for the intensification of PNA. This is in part owing to the robust enhancement of the tropical precipitation response to the CP SST variation. Indeed, further inspection suggests that models with stronger intensification of the CP SST variability and its related tropical precipitation response tend to have larger deepening magnitude of the North Pacific trough associated with the PNA variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4379C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4379C">Pacific-North American teleconnection and North Pacific Oscillation: historical simulation and future projection in CMIP5 models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Zheng; Gan, Bolan; Wu, Lixin; Jia, Fan 2018-06-01 Based on reanalysis datasets and as many as 35 CMIP5 models, this study evaluates the capability of climate models to simulate the spatiotemporal features of Pacific-North American teleconnection (PNA) and North Pacific Oscillation (NPO) in the twentieth century wintertime, and further investigates their responses to greenhouse warming in the twenty-first century. Analysis reveals that while the majority (80%) of models reasonably simulate either the geographical distribution or the amplitude of PNA/NPO pattern, only half of models can well capture both features in space. As for the temporal features, variabilities of PNA and NPO in most models are biased toward higher amplitude. Additionally, most models simulate the interannual variabilities of PNA and NPO, qualitatively consistent with the observation, whereas models generally lack the capability to reproduce the decadal (20-25 years) variability of PNA. As the climate warms under the strongest future warming scenario, the PNA intensity is found to be strengthened, whereas there is no consensus on the direction of change in the NPO intensity among models. The intensification of positive PNA is primarily manifested in the large deepening of the North Pacific trough, which is robust as it is 2.3 times the unforced internal variability. By focusing on the tropical Pacific Ocean, we find that the multidecadal evolution of the North Pacific trough intensity (dominating the PNA intensity evolution) is closely related to that of the analogous trough in the PNA-like teleconnection forced by sea surface temperature anomalies (SSTa) in the tropical central Pacific (CP) rather than the tropical eastern Pacific (EP). Such association is also found to act under greenhouse warming: that is, the strengthening of the PNA-like teleconnection induced by the CP SSTa rather than the EP SSTa is a driving force for the intensification of PNA. This is in part owing to the robust enhancement of the tropical precipitation response to the CP SST variation. Indeed, further inspection suggests that models with stronger intensification of the CP SST variability and its related tropical precipitation response tend to have larger deepening magnitude of the North Pacific trough associated with the PNA variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.464....1P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.464....1P">The combined influence of Pacific decadal oscillation and Atlantic multidecadal oscillation on central Mexico since the early 1600s</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Park, Jungjae; Byrne, Roger; Böhnel, Harald 2017-04-01 Periodic droughts have been one of the most serious environmental issues in central Mexico since the earliest times. The impacts of future droughts are likely to become even more severe as the current global warming trend increases potential evaporation and moisture deficits. A full understanding of the mechanism underlying climate variability is imperative to narrow the uncertainty about future droughts and predict water availability. The climatic complexity generated by the combined influence of both Atlantic and Pacific forcings, however, causes considerable difficulty in interpreting central Mexican climate records. Also, the lack of high-resolution information regarding the climate in the recent past makes it difficult to clearly understand current drought mechanisms. Our new high-resolution δ18 O record from Hoya Rincon de Parangueo in central Mexico provides useful information on climate variations since the early 1600s. According to our results, the central Mexican climate has been predominantly controlled by the combined influence of the 20-year Pacific Decadal Oscillation (PDO) and the 70-year Atlantic Multidecadal Oscillation (AMO). However, the AMO probably lost much of its influence in central Mexico in the early 20th century and the PDO has mostly driven climate change since. Marked dryness was mostly associated with co-occurrence of highly positive PDO and negative AMO between ∼1600 and 1900. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5003230','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5003230">Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Vezzulli, Luigi; Grande, Chiara; Reid, Philip C.; Hélaouët, Pierre; Edwards, Martin; Höfle, Manfred G.; Brettar, Ingrid; Colwell, Rita R.; Pruzzo, Carla 2016-01-01 Climate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet. In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958–2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years. PMID:27503882 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4626800','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4626800">Vegetation Greening and Climate Change Promote Multidecadal Rises of Global Land Evapotranspiration</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Zhang, Ke; Kimball, John S.; Nemani, Ramakrishna R.; Running, Steven W.; Hong, Yang; Gourley, Jonathan J.; Yu, Zhongbo 2015-01-01 Recent studies showed that anomalous dry conditions and limited moisture supply roughly between 1998 and 2008, especially in the Southern Hemisphere, led to reduced vegetation productivity and ceased growth in land evapotranspiration (ET). However, natural variability of Earth’s climate system can degrade capabilities for identifying climate trends. Here we produced a long-term (1982–2013) remote sensing based land ET record and investigated multidecadal changes in global ET and underlying causes. The ET record shows a significant upward global trend of 0.88 mm yr−2 (P < 0.001) over the 32-year period, mainly driven by vegetation greening (0.018% per year; P < 0.001) and rising atmosphere moisture demand (0.75 mm yr−2; P = 0.016). Our results indicate that reduced ET growth between 1998 and 2008 was an episodic phenomenon, with subsequent recovery of the ET growth rate after 2008. Terrestrial precipitation also shows a positive trend of 0.66 mm yr−2 (P = 0.08) over the same period consistent with expected water cycle intensification, but this trend is lower than coincident increases in evaporative demand and ET, implying a possibility of cumulative water supply constraint to ET. Continuation of these trends will likely exacerbate regional drought-induced disturbances, especially during regional dry climate phases associated with strong El Niño events. PMID:26514110 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26514110','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26514110">Vegetation Greening and Climate Change Promote Multidecadal Rises of Global Land Evapotranspiration.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhang, Ke; Kimball, John S; Nemani, Ramakrishna R; Running, Steven W; Hong, Yang; Gourley, Jonathan J; Yu, Zhongbo 2015-10-30 Recent studies showed that anomalous dry conditions and limited moisture supply roughly between 1998 and 2008, especially in the Southern Hemisphere, led to reduced vegetation productivity and ceased growth in land evapotranspiration (ET). However, natural variability of Earth's climate system can degrade capabilities for identifying climate trends. Here we produced a long-term (1982-2013) remote sensing based land ET record and investigated multidecadal changes in global ET and underlying causes. The ET record shows a significant upward global trend of 0.88 mm yr(-2) (P < 0.001) over the 32-year period, mainly driven by vegetation greening (0.018% per year; P < 0.001) and rising atmosphere moisture demand (0.75 mm yr(-2); P = 0.016). Our results indicate that reduced ET growth between 1998 and 2008 was an episodic phenomenon, with subsequent recovery of the ET growth rate after 2008. Terrestrial precipitation also shows a positive trend of 0.66 mm yr(-2) (P = 0.08) over the same period consistent with expected water cycle intensification, but this trend is lower than coincident increases in evaporative demand and ET, implying a possibility of cumulative water supply constraint to ET. Continuation of these trends will likely exacerbate regional drought-induced disturbances, especially during regional dry climate phases associated with strong El Niño events. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRD..117.8108S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRD..117.8108S">Tree ring based precipitation reconstruction in the south slope of the middle Qilian Mountains, northeastern Tibetan Plateau, over the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sun, Junyan; Liu, Yu 2012-04-01 A tree ring (Sabina przewalskiiKom.) based millennial precipitation reconstruction on the south slope of the middle Qilian Mountains in the northeastern margin of Tibetan Plateau, China, was completed, which explains 48.5% of the variance in the instrumental precipitation from 1958 to 2004. The long-term precipitation variation patterns were confirmed on the basis of the duration, magnitude, and intensify of the multidecadal dry (wet) events. There are several stronger multidecadal dry periods, 1092-1172, 1441-1517, and 1564-1730, whereas there is only one outstanding severe wet event of 1352-1440. The variations of the precipitation reconstruction are accordant with the glacier accumulation and dust contents of Dunde ice core and also with the variations of the precipitation, runoff, Palmer Drought Severity Index, and tree ring width series in the northeastern Tibetan Plateau. The spatial extent of the great drought in the latter half of the 15th century also concentrated on the northeastern Tibetan Plateau. The moisture variations in the northeastern Tibetan Plateau are synchronous over a large spatial and temporal range in multidecadal scale for the last millennium, especially during dry periods. Wavelet analyses and comparisons with the minimal solar activity show that the precipitation variations for the last millennium may have some association with the solar activity on multidecadal to centennial scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP43D..05Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP43D..05Z">Volcanic Eruptions as the Cause of the Little Ice Age</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zambri, B.; Robock, A. 2017-12-01 Both external forcing (solar radiation, volcanic eruptions) and internal fluctuations have been proposed to explain such multi-centennial perturbations as the Little Ice Age. Confidence in these hypotheses is limited due to the limited number of proxies, as well as only one observed realization of the Last Millennium. Here, we evaluate different hypotheses on the origin of Little Ice Age-like anomalies, focusing in particular on the long-term response of North Atlantic and Arctic climate perturbations to solar and volcanic perturbations. For that, we conduct a range of sensitivity tests carried out with the Community Earth System Model (CESM) at the National Center for Atmospheric Research, focusing in particular on the sensitivity to initial conditions and the strength of solar and volcanic forcing. By comparing the climate response to various combinations of external perturbations, we demonstrate nonlinear interactions that are necessary to explain trends observed in the fully coupled system and discuss physical mechanisms through which these external forcings can trigger multidecadal modes of the Atlantic Multidecadal Oscillation and subsequently lead to a Little-Ice-Age-like regime. For that, we capture and compare patterns of the coupled atmosphere-sea-ice-ocean response as revealed through a range of data analysis techniques. We show that the large 1257 Samalas, 1452 Kuwae, and 1600 Huaynaputina volcanic eruptions were the main causes of the multi-centennial glaciation associated with the Little Ice Age. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSME13A..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSME13A..04L">Potential Impact of North Atlantic Climate Variability on Ocean Biogeochemical Processes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liu, Y.; Muhling, B.; Lee, S. K.; Muller-Karger, F. E.; Enfield, D. B.; Lamkin, J. T.; Roffer, M. A. 2016-02-01 Previous studies have shown that upper ocean circulations largely determine primary production in the euphotic layers, here the global ocean model with biogeochemistry (GFDL's Modular Ocean Model with TOPAZ biogeochemistry) forced with the ERA-Interim is used to simulate the natural variability of biogeochemical processes in global ocean during 1979-present. Preliminary results show that the surface chlorophyll is overall underestimated in MOM-TOPAZ, but its spatial pattern is fairly realistic. Relatively high chlorophyll variability is shown in the subpolar North Atlantic, northeastern tropical Atlantic, and equatorial Atlantic. Further analysis suggests that the chlorophyll variability in the North Atlantic Ocean is affected by long-term climate variability. For the subpolar North Atlantic region, the chlorophyll variability is light-limited and is significantly correlated with North Atlantic Oscillation. A dipole pattern of chlorophyll variability is found between the northeastern tropical Atlantic and equatorial Atlantic. For the northeastern North Atlantic, the chlorophyll variability is significantly correlated with Atlantic Meridional Mode (AMM) and Atlantic Multidecadal Oscillation (AMO). During the negative phase of AMM and AMO, the increased trade wind in the northeast North Atlantic can lead to increased upwelling of nutrients. In the equatorial Atlantic region, the chlorophyll variability is largely link to Atlantic-Niño and associated equatorial upwelling of nutrients. The potential impact of climate variability on the distribution of pelagic fishes (i.e. yellowfin tuna) are discussed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMS...133...39G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMS...133...39G">Connecting Atlantic temperature variability and biological cycling in two earth system models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gnanadesikan, Anand; Dunne, John P.; Msadek, Rym 2014-05-01 Connections between the interdecadal variability in North Atlantic temperatures and biological cycling have been widely hypothesized. However, it is unclear whether such connections are due to small changes in basin-averaged temperatures indicated by the Atlantic Multidecadal Oscillation (AMO) Index, or whether both biological cycling and the AMO index are causally linked to changes in the Atlantic Meridional Overturning Circulation (AMOC). We examine interdecadal variability in the annual and month-by-month diatom biomass in two Earth System Models with the same formulations of atmospheric, land, sea ice and ocean biogeochemical dynamics but different formulations of ocean physics and thus different AMOC structures and variability. In the isopycnal-layered ESM2G, strong interdecadal changes in surface salinity associated with changes in AMOC produce spatially heterogeneous variability in convection, nutrient supply and thus diatom biomass. These changes also produce changes in ice cover, shortwave absorption and temperature and hence the AMO Index. Off West Greenland, these changes are consistent with observed changes in fisheries and support climate as a causal driver. In the level-coordinate ESM2M, nutrient supply is much higher and interdecadal changes in diatom biomass are much smaller in amplitude and not strongly linked to the AMO index. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2718Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2718Z">Response of North Atlantic Ocean Chlorophyll a to the Change of Atlantic Meridional Overturning Circulation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, Min; Zhang, Yuanling; Shu, Qi; Zhao, Chang; Wang, Gang; Wu, Zhaohua; Qiao, Fangli 2017-04-01 Changes in marine phytoplankton are a vital component in global carbon cycling. Despite this far-reaching importance, the variable trend in phytoplankton and its response to climate variability remain unclear. This work presents the spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean by using merged ocean color products for the period 1997-2016. We find a dipole pattern between the subpolar gyre and the Gulf Stream path,and chlorophyll a trend signal propagatedalong the opposite direction of the North Atlantic Current. Such a dipole pattern and opposite propagation of chlorophyll a signal are consistent with the recent distinctive signature of the slowdown of the Atlantic MeridionalOverturning Circulation (AMOC). It is suggested that the spatiotemporal evolution of chlorophyll a during the two most recent decades is a part of the multidecadal variation and regulated byAMOC, which could be used as an indicator of AMOC variations. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A31H..01V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A31H..01V">Reconstruction of regional climate and climate change in past decades</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> von Storch, H.; Feser, F.; Weisse, R.; Zahn, M. 2009-12-01 Regional climate models, which are constrained by large scale information (spectral nudging) provided by re-analyses, allow for the construction of a mostly homogeneous description of regional weather statistics since about 1950. The potential of this approach has been demonstrated for Northern Europe. That data set, named CoastDat, does not only contain hourly data on atmospheric variables, in particular wind, but also on marine weather, i.e., short term water level, current and sea state variations. Another example is the multi-decadal variability of Polar Lows in the subarctic waters. The utility of such data sets is broad, from risk assessments related to coastal wind and wave conditions, assessment of determining the causes for regional climate change, a-posteriori analysis of the efficiency of environmental legislation (example: lead). In the paper, the methodology is outlined, examples are provided and the utility of the product discussed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912063L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912063L">Is there a connection between Earth's core and climate at multidecadal time scales?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lambert, Sébastien; Marcus, Steven; de Viron, Olivier 2017-04-01 The length-of-day (LOD) undergoes multidecadal variations of several milliseconds (ms) attributed to changes in the fluid outer core angular momentum. These variations resemble a quasi-periodic oscillation of duration 60 to 70 years, although the periodicity (and its accurate length) are disputable because of the relatively short observational time span and the lower quality of the observations before the 20th century. Interestingly, similar variations show up in various measured or reconstructed climate indices including the sea surface (SST) and surface air (SAT) temperatures. It has been shown in several studies that LOD variations lead SST and SAT variations by a few years. No clear scenarios have been raised so far to explain the link between external, astronomical forcing (e.g., Solar wind), Earth's rotation (core-driven torsional) oscillations, and Earth's surface processes (climate variations) at these time scales. Accumulating evidence, however, suggests the centrifugal tides generated by multidecadal LOD variations as a 'valve' to control the transfer of thermal energy from the lithosphere to the surface via geothermal fluxes. This hypothesis is supported by recent studies reporting significant correlations between tidal and rotational excitation and seafloor and surface volcanism. In this study, we extend recent works from us and other independent authors by re-assessing the correlations between multidecadal LOD, climate indices, Solar and magnetic activities, as well as gridded data including SST, SAT, and cloud cover. We pay a special attention to the time lags: when a significant correlation is found, the value of the lag may help to discriminate between various possible scenarios. We locate some `hot spots', particularly in the Atlantic ocean and along the trajectory of the upper branch of the Atlantic meridional overturning circulation (AMOC), where the 70-yr oscillation is strongly marked. In addition, we discuss the possibility for centrifugal tides generated by multidecadal LOD variations to activate geothermal activity on the seafloor or to affect the global conveyor belt circulation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JHyd..528..550S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JHyd..528..550S">Baseflow response to climate variability induced droughts in the Apalachicola-Chattahoochee-Flint River Basin, U.S.A.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Singh, Sarmistha; Srivastava, Puneet; Abebe, Ash; Mitra, Subhasis 2015-09-01 Droughts have been a major factor leading to the Tri-State Water Wars in the southeastern United States. One of the primary issues related to the conflict is the reduction in baseflow levels in the Flint River during droughts. This affects the availability of freshwater resources to support the endangered mussel species in the Flint and Apalachicola Rivers and threatens the shellfish industry in the Apalachicola Bay. Study of large-scale climate phenomena as well as the interactions of interannual with decadal and multidecadal oceanic-atmospheric phenomena can provide valuable information regarding regional climatic conditions such as droughts and their impact on water resources. This study was conducted to quantify the impacts of climate variability cycles on baseflow levels in the Flint River. The individual and coupled impacts of the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and North Atlantic Oscillation (NAO) on baseflow were quantified. The non-parametric Joint Rank Fit (JRFit) procedure was used to provide a robust test of the significance of interactions between the phases of ENSO-PDO, ENSO-AMO and ENSO-NAO baseflows. Simple-main effect comparisons were also performed using the JRFit model to estimate significant difference between the positive and negative phase baseflows of PDO, AMO and NAO associated with El Niño or La Niña phases. The results indicate that the phases of ENSO, AMO and NAO significantly affect baseflows in the Flint River. Interaction tests showed that the PDO and AMO phases modulate ENSO phase baseflows. La Niña associated with positive phases of PDO and AMO resulted in greater decrease in baseflow levels of approximately 28% and 33%, respectively. However, La Niña associated with negative phase of AMO showed above normal baseflows. The results illustrate the importance of coupled analyses of climate variability by providing a better understanding of the severity of droughts and their impact on baseflows. The results obtained from this study can be used by water managers in the region as a guide for the issuance of drought severity-based water restrictions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT.......190K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT.......190K">Regional hydro-climatic impacts of contemporary Amazonian deforestation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Khanna, Jaya More than 17% of the Amazon rainforest has been cleared in the past three decades triggering important climatological and societal impacts. This thesis is devoted to identifying and explaining the regional hydroclimatic impacts of this change employing multidecadal satellite observations and numerical simulations providing an integrated perspective on this topic. The climatological nature of this study motivated the implementation and application of a cloud detection technique to a new geostationary satellite dataset. The resulting sub daily, high spatial resolution, multidecadal time series facilitated the detection of trends and variability in deforestation triggered cloud cover changes. The analysis was complemented by satellite precipitation, reanalysis and ground based datasets and attribution with the variable resolution Ocean-Land-Atmosphere-Model. Contemporary Amazonian deforestation affects spatial scales of hundreds of kilometers. But, unlike the well-studied impacts of a few kilometers scale deforestation, the climatic response to contemporary, large scale deforestation is neither well observed nor well understood. Employing satellite datasets, this thesis shows a transition in the regional hydroclimate accompanying increasing scales of deforestation, with downwind deforested regions receiving 25% more and upwind deforested regions receiving 25% less precipitation from the deforested area mean. Simulations robustly reproduce these shifts when forced with increasing deforestation alone, suggesting a negligible role of large-scale decadal climate variability in causing the shifts. Furthermore, deforestation-induced surface roughness variations are found necessary to reproduce the observed spatial patterns in recent times illustrating the strong scale-sensitivity of the climatic response to Amazonian deforestation. This phenomenon, inconsequential during the wet season, is found to substantially affect the regional hydroclimate in the local dry and parts of transition seasons, hence occurring in atmospheric conditions otherwise less conducive to thermal convection. Evidence of this phenomenon is found at two large scale deforested areas considered in this thesis. Hence, the 'dynamical' mechanism, which affects the seasons most important for regional ecology, emerges as an impactful convective triggering mechanism. The phenomenon studied in this thesis provides context for thinking about the climate of a future, more patchily forested Amazonia, by articulating relationships between climate and spatial scales of deforestation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1304704-role-atlantic-multi-decadal-oscillation-global-mean-temperature-variability','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1304704-role-atlantic-multi-decadal-oscillation-global-mean-temperature-variability">The role of Atlantic Multi-decadal Oscillation in the global mean temperature variability</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Chylek, Petr; Klett, James D.; Dubey, Manvendra K.; ... 2016-11-01 We simulated the global mean 1900–2015 warming by 42 Coupled Models Inter-comparison Project, phase 5 (CMIP5) climate models varies between 0.58 and 1.70 °C. The observed warming according to the NASA GISS temperature analysis is 0.95 °C with a 1200 km smoothing radius, or 0.86 °C with a 250 km smoothing radius. The projection of the future 2015–2100 global warming under a moderate increase of anthropogenic radiative forcing (RCP4.5 scenario) by individual models is between 0.7 and 2.3 °C. The CMIP5 climate models agree that the future climate will be warmer; however, there is little consensus as to how largemore » the warming will be (reflected by an uncertainty of over a factor of three). Moreover, a parsimonious statistical regression model with just three explanatory variables [anthropogenic radiative forcing due to greenhouse gases and aerosols (GHGA), solar variability, and the Atlantic Multi-decadal Oscillation (AMO) index] accounts for over 95 % of the observed 1900–2015 temperature variance. This statistical regression model reproduces very accurately the past warming (0.96 °C compared to the observed 0.95 °C) and projects the future 2015–2100 warming to be around 0.95 °C (with the IPCC 2013 suggested RCP4.5 radiative forcing and an assumed cyclic AMO behavior). The AMO contribution to the 1970–2005 warming was between 0.13 and 0.20 °C (depending on which AMO index is used) compared to the GHGA contribution of 0.49–0.58 °C. During the twenty-first century AMO cycle the AMO contribution is projected to remain the same (0.13–0.20 °C), while the GHGA contribution is expected to decrease to 0.21–0.25 °C due to the levelling off of the GHGA radiative forcing that is assumed according to the RCP4.5 scenario. Therefore, the anthropogenic contribution and natural variability are expected to contribute about equally to the anticipated global warming during the second half of the twenty-first century for the RCP4.5 trajectory.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1304704','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1304704">The role of Atlantic Multi-decadal Oscillation in the global mean temperature variability</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Chylek, Petr; Klett, James D.; Dubey, Manvendra K. We simulated the global mean 1900–2015 warming by 42 Coupled Models Inter-comparison Project, phase 5 (CMIP5) climate models varies between 0.58 and 1.70 °C. The observed warming according to the NASA GISS temperature analysis is 0.95 °C with a 1200 km smoothing radius, or 0.86 °C with a 250 km smoothing radius. The projection of the future 2015–2100 global warming under a moderate increase of anthropogenic radiative forcing (RCP4.5 scenario) by individual models is between 0.7 and 2.3 °C. The CMIP5 climate models agree that the future climate will be warmer; however, there is little consensus as to how largemore » the warming will be (reflected by an uncertainty of over a factor of three). Moreover, a parsimonious statistical regression model with just three explanatory variables [anthropogenic radiative forcing due to greenhouse gases and aerosols (GHGA), solar variability, and the Atlantic Multi-decadal Oscillation (AMO) index] accounts for over 95 % of the observed 1900–2015 temperature variance. This statistical regression model reproduces very accurately the past warming (0.96 °C compared to the observed 0.95 °C) and projects the future 2015–2100 warming to be around 0.95 °C (with the IPCC 2013 suggested RCP4.5 radiative forcing and an assumed cyclic AMO behavior). The AMO contribution to the 1970–2005 warming was between 0.13 and 0.20 °C (depending on which AMO index is used) compared to the GHGA contribution of 0.49–0.58 °C. During the twenty-first century AMO cycle the AMO contribution is projected to remain the same (0.13–0.20 °C), while the GHGA contribution is expected to decrease to 0.21–0.25 °C due to the levelling off of the GHGA radiative forcing that is assumed according to the RCP4.5 scenario. Therefore, the anthropogenic contribution and natural variability are expected to contribute about equally to the anticipated global warming during the second half of the twenty-first century for the RCP4.5 trajectory.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090009321&hterms=Time+series&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DTime%2Bseries','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090009321&hterms=Time+series&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DTime%2Bseries">Incorporating Satellite Time-Series Data into Modeling</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gregg, Watson 2008-01-01 In situ time series observations have provided a multi-decadal view of long-term changes in ocean biology. These observations are sufficiently reliable to enable discernment of even relatively small changes, and provide continuous information on a host of variables. Their key drawback is their limited domain. Satellite observations from ocean color sensors do not suffer the drawback of domain, and simultaneously view the global oceans. This attribute lends credence to their use in global and regional model validation and data assimilation. We focus on these applications using the NASA Ocean Biogeochemical Model. The enhancement of the satellite data using data assimilation is featured and the limitation of tongterm satellite data sets is also discussed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53D2280L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53D2280L">Modulation of the Aleutian-Icelandic Low Seesaw and Its Surface Impacts by the Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, F.; Orsolini, Y. J. 2017-12-01 Early studies suggested that the Aleutian-Icelandic low seesaw (AIS) features multidecadal variation. In this study, the multidecadal modulation of the AIS and associated surface climate by the Atlantic Multidecadal Oscillation (AMO) during late winter (February-March) is explored with observational data. It is shown that, in the cold phase of the AMO (AMO|-), a clear AIS is established, while this is not the case in the warm phase of the AMO (AMO|+). The surface climate over Eurasia is significantly influenced by the AMO's modulation of the Aleutian low (AL). For example, the weak AL in AMO|- displays warmer surface temperatures over the entire Far East and along the Russian Arctic coast and into Northern Europe, but only over the Russian Far East in AMO|+. Similarly, precipitation decreases over central Europe with the weak AL in AMO|-, but decreases over northern Europe and increases over southern Europe in AMO|+. The mechanism underlying the influence of AMO|- on the AIS can be described as follows: AMO|- weakens the upward component of the Eliassen-Palm flux along the polar waveguide by reducing atmospheric blocking occurrence over the Euro-Atlantic sector, and hence drives an enhanced stratospheric polar vortex. With the intensified polar night jet, the wave trains originating over the central North Pacific can propagate horizontally through North America and extend into the North Atlantic, favoring an eastward-extended Pacific-North America-Atlantic pattern, and resulting in a significant AIS at the surface during late winter. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdAtS..35...95L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdAtS..35...95L">Modulation of the Aleutian-Icelandic low seesaw and its surface impacts by the Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, Fei; Orsolini, Yvan J.; Wang, Huijun; Gao, Yongqi; He, Shengping 2018-01-01 Early studies suggested that the Aleutian-Icelandic low seesaw (AIS) features multidecadal variation. In this study, the multidecadal modulation of the AIS and associated surface climate by the Atlantic Multidecadal Oscillation (AMO) during late winter (February-March) is explored with observational data. It is shown that, in the cold phase of the AMO (AMO|-), a clear AIS is established, while this is not the case in the warm phase of the AMO (AMO|+). The surface climate over Eurasia is significantly influenced by the AMO's modulation of the Aleutian low (AL). For example, the weak AL in AMO|- displays warmer surface temperatures over the entire Far East and along the Russian Arctic coast and into Northern Europe, but only over the Russian Far East in AMO|+. Similarly, precipitation decreases over central Europe with the weak AL in AMO|-, but decreases over northern Europe and increases over southern Europe in AMO|+. The mechanism underlying the influence of AMO|- on the AIS can be described as follows: AMO|- weakens the upward component of the Eliassen-Palm flux along the polar waveguide by reducing atmospheric blocking occurrence over the Euro-Atlantic sector, and hence drives an enhanced stratospheric polar vortex. With the intensified polar night jet, the wave trains originating over the central North Pacific can propagate horizontally through North America and extend into the North Atlantic, favoring an eastward-extended Pacific-North America-Atlantic pattern, and resulting in a significant AIS at the surface during late winter. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP22A..08S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP22A..08S">Indices and Dynamics of Global Hydroclimate Over the Past Millennium from Data Assimilation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Steiger, N. J.; Smerdon, J. E. 2017-12-01 Reconstructions based on data assimilation (DA) are at the forefront of model-data syntheses in that such reconstructions optimally fuse proxy data with climate models. DA-based paleoclimate reconstructions have the benefit of being physically-consistent across the reconstructed climate variables and are capable of providing dynamical information about past climate phenomena. Here we use a new implementation of DA, that includes updated proxy system models and climate model bias correction procedures, to reconstruct global hydroclimate on seasonal and annual timescales over the last millennium. This new global hydroclimate product includes reconstructions of the Palmer Drought Severity Index, the Standardized Precipitation Evapotranspiration Index, and global surface temperature along with dynamical variables including the Nino 3.4 index, the latitudinal location of the intertropical convergence zone, and an index of the Atlantic Multidecadal Oscillation. Here we present a validation of the reconstruction product and also elucidate the causes of severe drought in North America and in equatorial Africa. Specifically, we explore the connection between droughts in North America and modes of ocean variability in the Pacific and Atlantic oceans. We also link drought over equatorial Africa to shifts of the intertropical convergence zone and modes of ocean variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JQS....21..689C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JQS....21..689C">Millennia-long tree-ring records from Tasmania and New Zealand: a basis for modelling climate variability and forcing, past, present and future</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cook, Edward R.; Buckley, Brendan M.; Palmer, Jonathan G.; Fenwick, Pavla; Peterson, Michael J.; Boswijk, Gretel; Fowler, Anthony 2006-10-01 Progress in the development of millennia-long tree-ring chronologies from Australia and New Zealand is reviewed from the perspective of modelling long-term climate variability there. Three tree species have proved successful in this regard: Huon pine (Lagarostrobos franklinii) from Tasmania, silver pine (L. colensoi) from the South Island of New Zealand, and kauri (Agathis australis) from the North Island of New Zealand. Each of these species is very long-lived and produces abundant quantities of well-preserved wood for extending their tree-ring chronologies back several millennia into the past. The growth patterns on these chronologies strongly correlate with both local and regional warm-season temperature changes over significant areas of the Southern Hemisphere (especially Huon and silver pine) and to ENSO variability emanating from the equatorial Pacific region (especially kauri). In addition, there is evidence for significant, band-limited, multi-decadal and centennial timescale variability in the warm-season temperature reconstruction based on Huon pine tree rings that may be related to slowly varying changes in ocean circulation dynamics in the southern Indian Ocean. This suggests the possibility of long-term climate predictability there. Copyright </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70025982','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70025982">Medieval Warm Period, Little Ice Age and 20th century temperature variability from Chesapeake Bay</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Cronin, T. M.; Dwyer, G.S.; Kamiya, T.; Schwede, S.; Willard, D.A. 2003-01-01 We present paleoclimate evidence for rapid (< 100 years) shifts of ~2-4oC in Chesapeake Bay (CB) temperature ~2100, 1600, 950, 650, 400 and 150 years before present (years BP) reconstructed from magnesium/calcium (Mg/Ca) paleothermometry. These include large temperature excursions during the Little Ice Age (~1400-1900 AD) and the Medieval Warm Period (~800-1300 AD) possibly related to changes in the strength of North Atlantic thermohaline circulation (THC). Evidence is presented for a long period of sustained regional and North Atlantic-wide warmth with low-amplitude temperature variability between ~450 and 1000 AD. In addition to centennial-scale temperature shifts, the existence of numerous temperature maxima between 2200 and 250 years BP (average ~70 years) suggests that multi-decadal processes typical of the North Atlantic Oscillation (NAO) are an inherent feature of late Holocene climate. However, late 19th and 20th century temperature extremes in Chesapeake Bay associated with NAO climate variability exceeded those of the prior 2000 years, including the interval 450-1000 AD, by 2-3oC, suggesting anomalous recent behavior of the climate system. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JCli...18..160R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JCli...18..160R">The Aleutian Low and Winter Climatic Conditions in the Bering Sea. Part I: Classification</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rodionov, S. N.; Overland, J. E.; Bond, N. A. 2005-01-01 The Aleutian low is examined as a primary determinant of surface air temperature (SAT) variability in the Bering Sea during the winter (December-January-February-March (DJFM)) months. The Classification and Regression Tree (CART) method is used to classify five types of atmospheric circulation for anomalously warm months (W1-W5) and cold months (C1-C5). For the Bering Sea, changes in the position of the Aleutian low are shown to be more important than changes in its central pressure. The first two types, W1 and C1, account for 51% of the "warm" and 37% of the "cold" months. The W1-type pattern is characterized by the anomalously deep Aleutian low shifted west and north of its mean position. In this situation, an increased cyclonic activity occurs in the western Bering Sea. The C1-type pattern represents a split Aleutian low with one center in the northwestern Pacific and the other in the Gulf of Alaska. The relative frequency of the W1 to C1 types of atmospheric circulation varies on decadal time scales, which helps to explain the predominance of fluctuations on these time scales in the weather of the Bering Sea. Previous work has noted the prominence of multidecadal variability in the North Pacific. The present study finds multidecadal variations in frequencies of the W3 and C3 patterns, both of which are characterized by increased cyclonic activity south of 51°N. In general, the CART method is found to be a suitable means for characterizing the wintertime atmospheric circulation of the North Pacific in terms of its impact on the Bering Sea. The results show that similar pressure anomaly patterns for the North Pacific as a whole can actually result in different conditions for the Bering Sea, and that similar weather conditions in the Bering Sea can arise from decidedly different large-scale pressure patterns. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QSRv..154..100S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QSRv..154..100S">A late Holocene record of solar-forced atmospheric blocking variability over Northern Europe inferred from varved lake sediments of Lake Kuninkaisenlampi</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Saarni, Saija; Muschitiello, Francesco; Weege, Stefanie; Brauer, Achim; Saarinen, Timo 2016-12-01 This study presents a new varved lake sediment sequence from Lake Kuninkaisenlampi, Eastern Finland. The record is constituted by alternations of clastic and biogenic laminae and provides a precise chronology extending back to 3607 ± 94 varve yrs. BP. The seasonality of the boreal climatic zone, with cold winters and mild summers, is reflected in the varve structure as a succession of three laminae from bottom to top, (i) a coarse to fine-grained detrital lamina marked by detrital catchment material transported by spring floods; (ii) a biogenic lamina with diatoms, plant and insect remnants reflecting biological productivity during the season of lake productivity; and (iii) a very fine amorphous organic lamina deposited during the winter stratification. The thickness of the detrital lamina in the lake reflects changes in the rate of spring snow melt in the catchment and is, therefore, considered a proxy for winter conditions. Hence, the record allows reconstructing local climate and environmental conditions on inter-annual to the multi-centennial timescales. We find that minerogenic accumulation reflected in the detrital lamina exhibits a high multi-decadal to centennial-scale spectral coherency with proxies for solar activity, such as Δ14C, and Total Solar Irradiance, suggesting a strong link between solar variability and sediment transport to the lake basin. Increased catchment erosion is observed during periods of low solar activity, which we ascribe to the development of more frequent atmospheric winter blocking circulation induced by solar-forced changes in the stratosphere. We suggest that soil frost in the catchment of Lake Kuninkaisenlampi related to more frequent winter blocking led to increased surface run-off and ultimately to increased catchment erosion during spring. We conclude that, during the past ca 3600 years, solar forcing may have modulated multi-decadal to centennial variations in sedimentation regimes in lakes from Eastern Finland and potentially in other North European lakes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018DyAtO..81...84L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018DyAtO..81...84L">Multi-decadal timeseries of the Indonesian throughflow</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, Mingting; Gordon, Arnold L.; Wei, Jun; Gruenburg, Laura K.; Jiang, Guoqing 2018-03-01 NCEP reanalysis wind data from 1948 to 2016 and Makassar Strait transport from 2004 to 2011 are used to construct a multi-decadal timeseries of 0-300 m Makassar Throughflow using a back-propagation (BP) neural network. Based on the 2004-2015 Makassar timeseries, 0-300 m transport accounts for 75% (±8%) of the total Makassar throughflow. Results from the INSTANT program 2004-2006 indicate that the Makassar throughflow provides 78% of the Indonesian Throughflow (ITF) within the upper 1000 m (77% of the full depth ITF). As the ITF is driven largely by North Pacific winds, we use the North Pacific zonal wind to construct a 68-year timeseries of 0-300 m Makassar Throughflow to trace interannual to decadal variability. The constructed timeseries has a mean transport of 9.2 ± 1 Sv within the 0-300 m layer. Using the 2004-2015 statistics this converts to a total Makassar Strait throughflow of 12.2 Sv and using the 2004-2006 INSTANT data, to a total ITF within the upper kilometer of 14.7 Sv. The Makassar throughflow decreases from 1948 to 1995, increases after 1995, then rapidly decreases after 2013, which agrees with the Pacific to Indian inter-ocean pressure difference across the Indonesian seas based on SODA reanalysis with a correlation coefficients of 0.6. The Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO), have correlation coefficients with the constructed Makassar throughflow of -0.6 and -0.4 respectively. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.8631V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.8631V">Regional reanalysis without local data: Exploiting the downscaling paradigm</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> von Storch, Hans; Feser, Frauke; Geyer, Beate; Klehmet, Katharina; Li, Delei; Rockel, Burkhardt; Schubert-Frisius, Martina; Tim, Nele; Zorita, Eduardo 2017-08-01 This paper demonstrates two important aspects of regional dynamical downscaling of multidecadal atmospheric reanalysis. First, that in this way skillful regional descriptions of multidecadal climate variability may be constructed in regions with little or no local data. Second, that the concept of large-scale constraining allows global downscaling, so that global reanalyses may be completed by additions of consistent detail in all regions of the world. Global reanalyses suffer from inhomogeneities. However, their large-scale componenst are mostly homogeneous; Therefore, the concept of downscaling may be applied to homogeneously complement the large-scale state of the reanalyses with regional detail—wherever the condition of homogeneity of the description of large scales is fulfilled. Technically, this can be done by dynamical downscaling using a regional or global climate model, which's large scales are constrained by spectral nudging. This approach has been developed and tested for the region of Europe, and a skillful representation of regional weather risks—in particular marine risks—was identified. We have run this system in regions with reduced or absent local data coverage, such as Central Siberia, the Bohai and Yellow Sea, Southwestern Africa, and the South Atlantic. Also, a global simulation was computed, which adds regional features to prescribed global dynamics. Our cases demonstrate that spatially detailed reconstructions of the climate state and its change in the recent three to six decades add useful supplementary information to existing observational data for midlatitude and subtropical regions of the world. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70155825','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70155825">Assessing the risk persistent drought using climate model simulations and paleoclimate data</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ault, Toby R.; Cole, Julia E.; Overpeck, Jonathan T.; Pederson, Gregory T.; Meko, David M. 2014-01-01 Projected changes in global rainfall patterns will likely alter water supplies and ecosystems in semiarid regions during the coming century. Instrumental and paleoclimate data indicate that natural hydroclimate fluctuations tend to be more energetic at low (multidecadal to multicentury) than at high (interannual) frequencies. State-of-the-art global climate models do not capture this characteristic of hydroclimate variability, suggesting that the models underestimate the risk of future persistent droughts. Methods are developed here for assessing the risk of such events in the coming century using climate model projections as well as observational (paleoclimate) information. Where instrumental and paleoclimate data are reliable, these methods may provide a more complete view of prolonged drought risk. In the U.S. Southwest, for instance, state-of-the-art climate model projections suggest the risk of a decade-scale megadrought in the coming century is less than 50%; the analysis herein suggests that the risk is at least 80%, and may be higher than 90% in certain areas. The likelihood of longer-lived events (>35 yr) is between 20% and 50%, and the risk of an unprecedented 50-yr megadrought is nonnegligible under the most severe warming scenario (5%–10%). These findings are important to consider as adaptation and mitigation strategies are developed to cope with regional impacts of climate change, where population growth is high and multidecadal megadrought—worse than anything seen during the last 2000 years—would pose unprecedented challenges to water resources in the region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6827M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6827M">Sea level variability at the coast: is it dominated by waves even at interdecadal time scales?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Melet, Angelique; Almar, Rafael; Meyssignac, Benoit 2017-04-01 Tide gauge records and satellite altimetry indicate that global mean sea level has risen by 16±3 cm during the 20th century. This rise is essentially due to thermal expansion of the ocean and land ice loss from glaciers and ice sheets in response to anthropogenic emissions of greenhouse gases. It is projected to continue over the 21st century and raise concerns for coastal regions. But coastal sea level variations are influenced by other processes such as tides, atmospheric surges and wave induced run-up and set-up. Here we examine the relative importance of the processes causing sea level variations at the coast over the last 23 years from observational datasets and model reanalyses focusing on coastal sites distributed along the world's coastlines for which tide gauges records are available. We show that the long term wave signal can dampen or enhance the effect of the ocean thermal expansion and land ice loss at the coast, over all time scales from subannnual to multidecadal. We estimate that the effect of waves generally explains 60%±20% of the coastal sea level variations at interannual to multidecadal time scales. In the Eastern Pacific, the wave effect dominates the total budget and counterbalances the thermal expansion of the ocean and land ice loss signals. These results highlight that the wave effect has to be taken into account in sea level predictions and projections. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPO14E2852L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPO14E2852L">Linking the South Atlantic Meridional Overturning Circulation and the Global Monsoons</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lopez, H.; Dong, S.; Goni, G. J.; Lee, S. K. 2016-02-01 This study tested the hypothesis whether low frequency decadal variability of the South Atlantic meridional heat transport (SAMHT) influences decadal variability of the global monsoons. A multi-century run from a state-of-the-art coupled general circulation model is used as basis for the analysis. Our findings indicate that multi-decadal variability of the South Atlantic Ocean plays a key role in modulating atmospheric circulation via interhemispheric changes in Atlantic Ocean heat content. Weaker SAMHT produces anomalous ocean heat divergence over the South Atlantic resulting in negative ocean heat content anomaly about 15 years later. This, in turn, forces a thermally direct anomalous interhemispheric Hadley circulation in the atmosphere, transporting heat from the northern hemisphere (NH) to the southern hemisphere (SH) and moisture from the SH to the NH, thereby intensify (weaken) summer (winter) monsoon in the NH and winter (summer) monsoon in the SH. Results also show that anomalous atmospheric eddies, both transient and stationary, transport heat northward in both hemispheres producing eddy heat flux convergence (divergence) in the NH (SH) around 15-30°, reinforcing the anomalous Hadley circulation. Overall, SAMHT decadal variability leads its atmospheric response by about 15 years, suggesting that the South Atlantic is a potential predictor of global climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H43D1679S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H43D1679S">Effect of Modulation of ENSO by Decadal and Multidecadal Ocean-Atmospheric Oscillations on Continental US Streamflows</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Singh, S.; Abebe, A.; Srivastava, P.; Chaubey, I. 2017-12-01 Evaluation of the influences of individual and coupled oceanic-atmospheric oscillations on streamflow at a regional scale in the United States is the focus of this study. The main climatic oscillations considered in this study are: El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and North Atlantic Oscillation (NAO). Unimpacted or minimally impacted by water management streamflow data from the Model Parameter Estimation Experiment (MOPEX) were used in this study. Two robust and novel non-parametric tests, namely, the rank based partial least square (PLS) and the Joint Rank Fit (JRFit) procedures were used to identify the individual and coupled effect of oscillations on streamflow across continental U.S. (CONUS), respectively. Moreover, the interactive effects of ENSO with decadal and multidecadal cycles were tested and quantified using the JRFit interaction test. The analysis of ENSO indicated higher streamflows during La Niña phase compared to the El Niño phase in Northwest, Northeast and the lower part of Ohio Valley while the opposite occurs for rest of the climatic regions in US. Two distinct climate regions (Northwest and Southeast) were identified from the PDO analysis where PDO negative phase results in increased streamflow than PDO positive phase. Consistent negative and positive correlated regions around the CONUS were identified for AMO and NAO, respectively. The interaction test of ENSO with decadal and multidecadal oscillations showed that El Niño is modulated by the negative phase of PDO and NAO, and the positive phase of AMO, respectively, in the Upper Midwest. However, La Niña is modulated by the positive phase of AMO and PDO in Ohio Valley and Northeast while in Southeast and the South it is modulated by AMO negative phase. Results of this study will assist water managers to understand the streamflow change patterns across the CONUS at decadal and multi-decadal time scales. The information derived from this study would be helpful for regional water managers in forecasting regional water availability and help them develop drought adaptation and mitigation policies by incorporating information based on the large scale ocean-atmospheric cycles. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150001521','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150001521">The Stratospheric Aerosol and Gas Experiment (SAGE III) on the International Space Station (ISS) Mission</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Cisewski, Michael; Zawodny, Joseph; Gasbarre, Joseph; Eckman, Richard; Topiwala, Nandkishore; Rodriquez-Alvarez, Otilia; Cheek, Dianne; Hall, Steve 2014-01-01 The Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III/ISS) mission will provide the science community with high-vertical resolution and nearly global observations of ozone, aerosols, water vapor, nitrogen dioxide, and other trace gas species in the stratosphere and upper-troposphere. SAGE III/ISS measurements will extend the long-term Stratospheric Aerosol Measurement (SAM) and SAGE data record begun in the 1970s. The multi-decadal SAGE ozone and aerosol data sets have undergone intense scrutiny and are considered the international standard for accuracy and stability. SAGE data have been used to monitor the effectiveness of the Montreal Protocol. Key objectives of the mission are to assess the state of the recovery in the distribution of ozone, to re-establish the aerosol measurements needed by both climate and ozone models, and to gain further insight into key processes contributing to ozone and aerosol variability. The space station mid-inclination orbit allows for a large range in latitude sampling and nearly continuous communications with payloads. The SAGE III instrument is the fifth in a series of instruments developed for monitoring atmospheric constituents with high vertical resolution. The SAGE III instrument is a moderate resolution spectrometer covering wavelengths from 290 nm to 1550 nm. Science data is collected in solar occultation mode, lunar occultation mode, and limb scatter measurement mode. A SpaceX Falcon 9 launch vehicle will provide access to space. Mounted in the unpressurized section of the Dragon trunk, SAGE III will be robotically removed from the Dragon and installed on the space station. SAGE III/ISS will be mounted to the ExPRESS Logistics Carrier-4 (ELC-4) location on the starboard side of the station. To facilitate a nadir view from this location, a Nadir Viewing Platform (NVP) payload was developed which mounts between the carrier and the SAGE III Instrument Payload (IP). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A52E..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A52E..07P">Influence of North Atlantic modes on European climate extremes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Proemmel, K.; Cubasch, U. 2017-12-01 It is well known that the North Atlantic strongly influences European climate. Only few studies exist that focus on its impact on climate extremes. We are interested in these extremes and the processes and mechanisms behind it. For the analysis of the North Atlantic Oscillation (NAO) we use simulations performed with the Max Planck Institute for Meteorology Earth System Model (MPI-ESM). The NAO has a strong impact especially on European winter and the changes in minimum temperature are even larger than in maximum temperature. The impact of the Atlantic Multi-decadal Variability (AMV) on climate extremes is analyzed in ECHAM6 simulations forced with AMV warm and AMV cold sea surface temperature patterns. We analyze different extreme indices and try to understand the processes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70022457','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70022457">Climatic variability in the eastern United States over the past millenium from Chesapeake Bay sediments</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Cronin, T.; Willard, D.; Karlsen, A.; Ishman, S.; Verardo, S.; McGeehin, J.; Kerhin, R.; Holmes, C.; Colman, S.; Zimmerman, A. 2000-01-01 Salinity oscillations caused by multidecadal climatic variability had major impacts on the Chesapeake Bay estuarine ecosystem during the past 1000 yr. Microfossils from sediments dated by radiometry (14C, 137Cs, 210Pb) and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10-15 ppt during periods of extreme drought (low fresh-water discharge) and wet climate (high discharge). During the past 500 yr, 14 wet-dry cycles occurred, including sixteenth and early seventeenth century megadroughts that exceeded twentieth century droughts in their severity. These droughts correspond to extremely dry climate also recorded in North American tree-ring records and by early colonists. Wet periods occurred every ~60-70 yr, began abruptly, lasted <20 yr, and had mean annual rainfall ~25%-30% and fresh-water discharge ~40%-50% greater than during droughts. A shift toward wetter regional climate occurred in the early nineteenth century, lowering salinity and compounding the effects of agricultural land clearance on bay ecosystems. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3687247','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3687247">Climate-change impact on the 20th-century relationship between the Southern Annular Mode and global mean temperature</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wang, Guojian; Cai, Wenju 2013-01-01 The positive phase of the El Niño-Southern Oscillation (ENSO) increases global mean temperature, and contributes to a negative phase of the Southern Annular Mode (SAM), the dominant mode of climate variability in the Southern Hemisphere. This interannual relationship of a high global mean temperature associated with a negative SAM, however, is opposite to the relationship between their trends under greenhouse warming. We show that over much of the 20th century this relationship undergoes multidecadal fluctuations depending on the intensity of ENSO. During the period 1925–1955, subdued ENSO activities weakened the relationship. However, a similar weakening has occurred since the late 1970s despite the strong ENSO. We demonstrate that this recent weakening is induced by climate change in the Southern Hemisphere. Our result highlights a rare situation in which climate change signals emerge against an opposing property of interannual variability, underscoring the robustness of the recent climate change. PMID:23784087 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1972S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1972S">Multidecadal Variability in Surface Albedo Feedback Across CMIP5 Models</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schneider, Adam; Flanner, Mark; Perket, Justin 2018-02-01 Previous studies quantify surface albedo feedback (SAF) in climate change, but few assess its variability on decadal time scales. Using the Coupled Model Intercomparison Project Version 5 (CMIP5) multimodel ensemble data set, we calculate time evolving SAF in multiple decades from surface albedo and temperature linear regressions. Results are meaningful when temperature change exceeds 0.5 K. Decadal-scale SAF is strongly correlated with century-scale SAF during the 21st century. Throughout the 21st century, multimodel ensemble mean SAF increases from 0.37 to 0.42 W m-2 K-1. These results suggest that models' mean decadal-scale SAFs are good estimates of their century-scale SAFs if there is at least 0.5 K temperature change. Persistent SAF into the late 21st century indicates ongoing capacity for Arctic albedo decline despite there being less sea ice. If the CMIP5 multimodel ensemble results are representative of the Earth, we cannot expect decreasing Arctic sea ice extent to suppress SAF in the 21st century. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC21E0985O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC21E0985O">Uncertainty in Earth System Models: Benchmarks for Ocean Model Performance and Validation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ogunro, O. O.; Elliott, S.; Collier, N.; Wingenter, O. W.; Deal, C.; Fu, W.; Hoffman, F. M. 2017-12-01 The mean ocean CO2 sink is a major component of the global carbon budget, with marine reservoirs holding about fifty times more carbon than the atmosphere. Phytoplankton play a significant role in the net carbon sink through photosynthesis and drawdown, such that about a quarter of anthropogenic CO2 emissions end up in the ocean. Biology greatly increases the efficiency of marine environments in CO2 uptake and ultimately reduces the impact of the persistent rise in atmospheric concentrations. However, a number of challenges remain in appropriate representation of marine biogeochemical processes in Earth System Models (ESM). These threaten to undermine the community effort to quantify seasonal to multidecadal variability in ocean uptake of atmospheric CO2. In a bid to improve analyses of marine contributions to climate-carbon cycle feedbacks, we have developed new analysis methods and biogeochemistry metrics as part of the International Ocean Model Benchmarking (IOMB) effort. Our intent is to meet the growing diagnostic and benchmarking needs of ocean biogeochemistry models. The resulting software package has been employed to validate DOE ocean biogeochemistry results by comparison with observational datasets. Several other international ocean models contributing results to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) were analyzed simultaneously. Our comparisons suggest that the biogeochemical processes determining CO2 entry into the global ocean are not well represented in most ESMs. Polar regions continue to show notable biases in many critical biogeochemical and physical oceanographic variables. Some of these disparities could have first order impacts on the conversion of atmospheric CO2 to organic carbon. In addition, single forcing simulations show that the current ocean state can be partly explained by the uptake of anthropogenic emissions. Combined effects of two or more of these forcings on ocean biogeochemical cycles and ecosystems are challenging to predict since additive or antagonistic effects may occur. A benchmarking tool for accurate assessment and validation of marine biogeochemical outputs will be indispensable as the model community continues to improve ESM developments. It will provide a first order tool in understanding climate-carbon cycle feedbacks. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4963102','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4963102">Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ghosh, Subimal; Vittal, H.; Sharma, Tarul; Karmakar, Subhankar; Kasiviswanathan, K. S.; Dhanesh, Y.; Sudheer, K. P.; Gunthe, S. S. 2016-01-01 India’s agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC) model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins. PMID:27463092 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27463092','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27463092">Indian Summer Monsoon Rainfall: Implications of Contrasting Trends in the Spatial Variability of Means and Extremes.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ghosh, Subimal; Vittal, H; Sharma, Tarul; Karmakar, Subhankar; Kasiviswanathan, K S; Dhanesh, Y; Sudheer, K P; Gunthe, S S 2016-01-01 India's agricultural output, economy, and societal well-being are strappingly dependent on the stability of summer monsoon rainfall, its variability and extremes. Spatial aggregate of intensity and frequency of extreme rainfall events over Central India are significantly increasing, while at local scale they are spatially non-uniform with increasing spatial variability. The reasons behind such increase in spatial variability of extremes are poorly understood and the trends in mean monsoon rainfall have been greatly overlooked. Here, by using multi-decadal gridded daily rainfall data over entire India, we show that the trend in spatial variability of mean monsoon rainfall is decreasing as exactly opposite to that of extremes. The spatial variability of extremes is attributed to the spatial variability of the convective rainfall component. Contrarily, the decrease in spatial variability of the mean rainfall over India poses a pertinent research question on the applicability of large scale inter-basin water transfer by river inter-linking to address the spatial variability of available water in India. We found a significant decrease in the monsoon rainfall over major water surplus river basins in India. Hydrological simulations using a Variable Infiltration Capacity (VIC) model also revealed that the water yield in surplus river basins is decreasing but it is increasing in deficit basins. These findings contradict the traditional notion of dry areas becoming drier and wet areas becoming wetter in response to climate change in India. This result also calls for a re-evaluation of planning for river inter-linking to supply water from surplus to deficit river basins. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915757J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915757J">Multidecadal oscillations in past Baltic Sea hypoxia: the role of sedimentary iron-phosphorus feedbacks</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jilbert, Tom; Gustafsson, Bo G.; Veldhuijzen, Simon; Reed, Daniel C.; van Helmond, Niels A. G. M.; Slomp, Caroline P. 2017-04-01 The Baltic Sea currently experiences widespread deep-water hypoxia, a consequence of both anthropogenic nutrient loading and the natural susceptibility of its stratified water column to oxygen depletion. Sediment core records show that hypoxia was also prevalent in the Baltic during the Holocene Thermal Maximum (HTM) and Medieval Climate Anomaly (MCA). Sedimentary iron (Fe) and phosphorus (P) dynamics are known to play a key role in determining the intensity of Baltic Sea hypoxia through time. Rapid intensification of hypoxia at the onset of past centennial-scale hypoxic events during the HTM and MCA has been explained by release of P from sedimentary Fe oxides, leading to enhanced primary productivity and deep water oxygen consumption (Jilbert and Slomp, 2013). Similarly, rapid relief from hypoxia at the termination of these events reflects efficient trapping of P by Fe oxides as oxic conditions expand. Here we show that within past hypoxic events in the Baltic Sea, hypoxia intensity also varied continuously on multidecadal timescales. We observe persistent oscillations in new high-resolution records of sediment redox proxies derived from Laser Ablation (LA) ICP-MS analysis. In-phase multidecadal oscillations in molybdenum/aluminium (Mo/Al), bromine/phosphorus (Br/P) and Fe/Al indicate coupling between redox conditions, the flux of carbon to the seafloor, and mobilization of Fe in shelf areas, respectively. Using a simple box model, we show that instabilities in the response of sedimentary P release to changing oxygen concentrations and carbon flux were the likely cause of the observed oscillations. When prescribing a non-linear relationship between P release, oxygen concentration and carbon flux, and forcing the model with external P loadings typical of the HTM and MCA, the simulated time-series of deep-water oxygen show pronounced oscillations similar to those observed in the sediment records. However, when external P loads typical of the modern anthropogenic interval are used in the simulations, these instabilities are overcome and deep water conditions remain permanently hypoxic. The results suggest that complete recovery from hypoxia in the modern Baltic Sea will require a substantial further decline in external nutrient loading. Reference: Jilbert, T. and Slomp, C.P., Rapid high-amplitude variability in Baltic Sea hypoxia during the Holocene. Geology 41 (11), 1183-1186, 2013. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC13G1265P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC13G1265P">A Centrifugal Volcanism Mechanism for the AMO</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pratt, V. R. 2016-12-01 The Atlantic Multidecadal Oscillation has proved hard to isolate from both (i) global warming and (ii) faster oscillations. For (i), we showed [1] that by filtering all harmonics of a 63-year period, what remained could be explained remarkably accurately by the expected contribution of greenhouse warming along with the interesting increase in TSI during 1900-1950, leading to considerable confidence that global surface temperature averaged over 2069-2131 will be very close to 3 C above preindustrial. For (ii), principal component analysis of HadCRUT4 since 1850, Central England Temperature since 1659, and various other land and sea time series all show a distinct 21-year oscillation the start of whose downward swing is well synchronized with the maximum solar activity of the odd-numbered solar cycles, persisting even through the Maunder Minimum. After these are removed there remains a well-defined signal that has been associated with the so-called Atlantic Multidecadal Oscillation. There are two schools of thought, the AMO is of either radiative (RAD) or internal (INT) origin. RAD is explained in terms of aerosol fluctuations of volcanic origin. In [2] we gave what we felt was a knockdown argument against RAD. INT so far has been explained mainly in terms of instabilities in ocean currents such as the Atlantic Meridional Overturning Current. An interesting correlation between the AMO and Earth's Length of Day (LOD) has been noted by several authors. Missing is a plausible mechanism explaining this correlation. The mechanism we propose here is that magma welling up through ocean ridges is in a quasi-equilibrium that even small fluctuations in LOD can disturb significantly. Heat from emerging magma is carried up to the oceanic mixed layer in very large thermals. A simple model of this process leads to a correlation that is excellent except for the period 1940-1950. We propose to explain this difference in terms of a lifting of the crust by the excess magma developed during the long increase in LOD from 1880 to 1910. [1] Pratt, V.R., Model Complexity of Global Climate: Could Arrhenius have foreseen the hiatus? Session GC43C, AGUFM2015. [2] Pratt, V.R., Reconciling multidecadal land-sea global temperature with rising CO2. GC53C, AGUFM2013. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PEPS....4...13S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PEPS....4...13S">Outcomes and challenges of global high-resolution non-hydrostatic atmospheric simulations using the K computer</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Satoh, Masaki; Tomita, Hirofumi; Yashiro, Hisashi; Kajikawa, Yoshiyuki; Miyamoto, Yoshiaki; Yamaura, Tsuyoshi; Miyakawa, Tomoki; Nakano, Masuo; Kodama, Chihiro; Noda, Akira T.; Nasuno, Tomoe; Yamada, Yohei; Fukutomi, Yoshiki 2017-12-01 This article reviews the major outcomes of a 5-year (2011-2016) project using the K computer to perform global numerical atmospheric simulations based on the non-hydrostatic icosahedral atmospheric model (NICAM). The K computer was made available to the public in September 2012 and was used as a primary resource for Japan's Strategic Programs for Innovative Research (SPIRE), an initiative to investigate five strategic research areas; the NICAM project fell under the research area of climate and weather simulation sciences. Combining NICAM with high-performance computing has created new opportunities in three areas of research: (1) higher resolution global simulations that produce more realistic representations of convective systems, (2) multi-member ensemble simulations that are able to perform extended-range forecasts 10-30 days in advance, and (3) multi-decadal simulations for climatology and variability. Before the K computer era, NICAM was used to demonstrate realistic simulations of intra-seasonal oscillations including the Madden-Julian oscillation (MJO), merely as a case study approach. Thanks to the big leap in computational performance of the K computer, we could greatly increase the number of cases of MJO events for numerical simulations, in addition to integrating time and horizontal resolution. We conclude that the high-resolution global non-hydrostatic model, as used in this five-year project, improves the ability to forecast intra-seasonal oscillations and associated tropical cyclogenesis compared with that of the relatively coarser operational models currently in use. The impacts of the sub-kilometer resolution simulation and the multi-decadal simulations using NICAM are also reviewed. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRD..11913637C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRD..11913637C">Intensified anticyclonic anomaly over the western North Pacific during El Niño decaying summer under a weakened Atlantic thermohaline circulation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Wei; Lu, Riyu; Dong, Buwen 2014-12-01 It has been well documented that there is an anticyclonic anomaly over the western North Pacific (WNPAC, hereafter) during El Niño decaying summer. This El Niño-WNPAC relationship is greatly useful for the seasonal prediction of summer climate in the WNP and East Asia. In this study, we investigate the modification of the El Niño-WNPAC relationship induced by a weakened Atlantic thermohaline circulation (THC) in a water-hosing experiment. The results suggest that the WNPAC during the El Niño decaying summer, as well as the associated precipitation anomaly over the WNP, is intensified under the weakened THC. On the one hand, this intensification is in response to the increased amplitude and frequency of El Niño events in the water-hosing experiment. On the other hand, this intensification is also because of greater climatological humidity over the western to central North Pacific under the weakened THC. We suggest that the increase of climatological humidity over the western to central North Pacific during summer under the weakened THC is favorable for enhanced interannual variability of precipitation, and therefore favorable for the intensification of the WNPAC during El Niño decaying summer. This study suggests a possible modulation of the El Niño-Southern Oscillation-WNP summer monsoon relationship by the low-frequency fluctuation of Atlantic sea surface temperature. The results offer an explanation for the observed modification of the multidecadal fluctuation of El Niño-WNPAC relationship by the Atlantic multidecadal oscillation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2388F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2388F">Interdecadal modulation of the Atlantic Multi-decadal Oscillation (AMO) on southwest China's temperature over the past 250 years</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fang, Keyan; Guo, Zhengtang; Chen, Deliang; Wang, Lei; Dong, Zhipeng; Zhou, Feifei; Zhao, Yan; Li, Jinbao; Li, Yingjun; Cao, Xinguang 2018-05-01 The temperature gradient between southwestern China and Indian Ocean is one key driver of the Indian Summer Monsoon, suggesting the necessity to understand temperature variability in southwestern China. Contrary to the general warming experienced in most of China, a few regions in southwestern China have undergone a cooling trend since the 1950s. To place this cooling trend in a historical context, this study develops an Abies fabri tree-ring width chronology in the Sichuan Basin, the most populated region in southwest China. The chronology spans from 1590 to 2012, with its reliable portion from 1758 to 2012, by far the longest in the Sichuan Basin. To better extract regional climate signals encoded in tree rings with strong local disturbances, we incorporate climate signals of nearby tree-ring chronologies to generate a large-scale tree-ring chronology (LSC). The LSC shows higher correlations with temperature near the sampling site on Mount Emei and sea surface temperatures of the northern Atlantic Ocean than chronologies developed using traditional methods. The highest correlations between the LSC and temperature are found from current February to July in the Sichuan Basin for the period 1901-1950 (r = 0.70), with a sharp decrease afterwards. Interdecadal variations of the LSC match well with Atlantic Multi-decadal Oscillation reconstructions, except for the late nineteenth century and after 1980s. This study provides evidence that southwest China is a transitional region both affected by the interdecadal temperature variations of the northern Atlantic and Asian areas, although their influences weakened in recent possible due to enhanced human activities. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP41C2269L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP41C2269L">Multi-decadal to centennial scale variations in sea surface temperature off southeast Korea over the last 2000 yr</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lee, K. E.; Park, W.; Bae, S. W.; Nam, S. I. 2016-12-01 We have reconstructed variations in sea surface temperature (SST) for the last 2000 yr by using the alkenone unsaturation index of marine sediments of cores TY2010 PC4 and ARA/ES 03-01 GC01 recovered from the southwestern part of the East Sea. The core site is chracterized by very high sedimentation rate so that a new high-resolution continuous SST record can be reconstructed with an average temporal resolution of 2-7 years. The core top alkenone temperature (20.5°C) is higher than the annual averaged in situ SST (18 °C) and it corresponds to those of summer to autumn. During the last 2000 yr, the alkenone temperatures exhibited fluctuations on multi-decadal to centennial time scales. The temperatures were relatively warm fluctuating between 19.6°C and 21°C on centennial time scale during the period of AD 0- 1200. There were two evident cold periods: AD 1200-1400 and AD 1600-1800. The lowest temperature (approximately 18°C) occurred at AD 1290 and AD 1650. The temperatures increased toward 20 centry, which is consistent with anthropogenic global warming. Results of singular spectrum analysis of the last 2000 yr SST record suggest that there is characteristic periodicity of 100 yr and 160 yr and 50-60 yr, which can be natural variability of climate system. In addition, a comparison of the SST record with global volcanic forcing data shows that volcanic events also can be correlated to the distinct cooling events. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A13E0319S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A13E0319S">Inter-annual Variability of Temperature and Extreme Heat Events during the Nairobi Warm Season</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Scott, A.; Misiani, H. O.; Zaitchik, B. F.; Ouma, G. O.; Anyah, R. O.; Jordan, A. 2016-12-01 Extreme heat events significantly stress all organisms in the ecosystem, and are likely to be amplified in peri-urban and urban areas. Understanding the variability and drivers behind these events is key to generating early warnings, yet in Equatorial East Africa, this information is currently unavailable. This study uses daily maximum and minimum temperature records from weather stations within Nairobi and its surroundings to characterize variability in daily minimum temperatures and the number of extreme heat events. ERA-Interim reanalysis is applied to assess the drivers of these events at event and seasonal time scales. At seasonal time scales, high temperatures in Nairobi are a function of large scale climate variability associated with the Atlantic Multi-decadal Oscillation (AMO) and Global Mean Sea Surface Temperature (GMSST). Extreme heat events, however, are more strongly associated with the El Nino Southern Oscillation (ENSO). For instance, the persistence of AMO and ENSO, in particular, provide a basis for seasonal prediction of extreme heat events/days in Nairobi. It is also apparent that the temporal signal from extreme heat events in tropics differs from classic heat wave definitions developed in the mid-latitudes, which suggests that a new approach for defining these events is necessary for tropical regions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70184378','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70184378">Holocene climate and climate variability of the northern Gulf of Mexico and adjacent northern Gulf Coast: A review</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Poore, Richard Z. 2008-01-01 Marine records from the northern Gulf of Mexico indicate that significant multidecadal- and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3°C, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details of climate variability are not well known. Continuous and well-dated records of climate change and climate variability in the western portion of the northern Gulf Coast are essentially lacking.Information on Holocene floods, droughts, and storm frequency along the northern Gulf Coast is limited. Records of floods may be preserved in continental shelf sediments, but establishing continuity and chronologies for sedimentary sequences on the shelf presents challenges due to sediment remobilization and redeposition during storms. Studies of past storm deposits in coastal lakes and marshes show promise for constructing records of past storm frequency. A recent summary of sea-level history of the northern Gulf Coast indicates sea level was higher than modern sea level several times during the last few thousand years. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP41E..08T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP41E..08T">140-year subantarctic tree-ring temperature reconstruction reveals tropical forcing of increased Southern Ocean climate variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Turney, C. S.; Fogwill, C. J.; Palmer, J. G.; VanSebille, E.; Thomas, Z.; McGlone, M.; Richardson, S.; Wilmshurst, J.; Fenwick, P.; Zunz, V.; Goosse, H.; Wilson, K. J.; Carter, L.; Lipson, M.; Jones, R. T.; Harsch, M.; Clark, G.; Marzinelli, E.; Rogers, T.; Rainsley, E.; Ciasto, L.; Waterman, S.; Thomas, E. R.; Visbeck, M. 2017-12-01 Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine-atmosphere-ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on south-west Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52-54˚S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record, and coincident with major changes in mammalian and bird populations. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4177G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4177G">Vadose zone controls on damping of climate-induced transient recharge fluxes in U.S. agroecosystems</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gurdak, Jason 2017-04-01 Understanding the physical processes in the vadose zone that link climate variability with transient recharge fluxes has particular relevance for the sustainability of groundwater-supported irrigated agriculture and other groundwater-dependent ecosystems. Natural climate variability on interannual to multidecadal timescales has well-documented influence on precipitation, evapotranspiration, soil moisture, infiltration flux, and can augment or diminish human stresses on water resources. Here the behavior and damping depth of climate-induced transient water flux in the vadose zone is explored. The damping depth is the depth in the vadose zone that the flux variation damps to 5% of the land surface variation. Steady-state recharge occurs when the damping depth is above the water table, and transient recharge occurs when the damping depth is below the water table. Findings are presented from major agroecosystems of the United States (U.S.), including the High Plains, Central Valley, California Coastal Basin, and Mississippi Embayment aquifer systems. Singular spectrum analysis (SSA) is used to identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (<1-4 yr cycle), El Niño/Southern Oscillation (ENSO) (2-7 yr cycle), North Atlantic Oscillation (NAO) (3-6 yr cycle), Pacific Decadal Oscillation (PDO) (15-30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 yr cycle). SSA results indicate that nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. Results from HYDRUS-1D simulations indicate that transient water flux through the vadose zone are controlled by highly nonlinear interactions between mean infiltration flux and infiltration period related to the modes of climate variability and the local soil textures, layering, and depth to the water table. Simulation results for homogeneous profiles generally show that shorter-period climate oscillations, smaller mean fluxes, and finer-grained soil textures generally produce damping depths closer to land surface. Simulation results for layered soil textures indicate more complex responses in the damping depth, including the finding that finer-textured layers in a coarser soil profile generally result in damping depths closer to land surface, while coarser-textured layers in coarser soil profile result in damping depths deeper in the vadose zone. Findings from this study improve understanding of how vadose zone properties influences transient recharge flux and damp climate variability signals in groundwater systems, and have important implications for sustainable management of groundwater resources and coupled agroecosystems under future climate variability and change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp....5S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp....5S">Mediterranean sea water budget long-term trend inferred from salinity observations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Skliris, N.; Zika, J. D.; Herold, L.; Josey, S. A.; Marsh, R. 2018-01-01 Changes in the Mediterranean water cycle since 1950 are investigated using salinity and reanalysis based air-sea freshwater flux datasets. Salinity observations indicate a strong basin-scale multi-decadal salinification, particularly in the intermediate and deep layers. Evaporation, precipitation and river runoff variations are all shown to contribute to a very strong increase in net evaporation of order 20-30%. While large temporal uncertainties and discrepancies are found between E-P multi-decadal trend patterns in the reanalysis datasets, a more robust and spatially coherent structure of multi-decadal change is obtained for the salinity field. Salinity change implies an increase in net evaporation of 8 to 12% over 1950-2010, which is considerably lower than that suggested by air-sea freshwater flux products, but still largely exceeding estimates of global water cycle amplification. A new method based on water mass transformation theory is used to link changes in net evaporation over the Mediterranean Sea with changes in the volumetric distribution of salinity. The water mass transformation distribution in salinity coordinates suggests that the Mediterranean basin salinification is driven by changes in the regional water cycle rather than changes in salt transports at the straits. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.tmp...72R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.tmp...72R">Upper-Level Mediterranean Oscillation index and seasonal variability of rainfall and temperature</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Redolat, Dario; Monjo, Robert; Lopez-Bustins, Joan A.; Martin-Vide, Javier 2018-02-01 The need for early seasonal forecasts stimulates continuous research in climate teleconnections. The large variability of the Mediterranean climate presents a greater difficulty in predicting climate anomalies. This article reviews teleconnection indices commonly used for the Mediterranean basin and explores possible extensions of one of them, the Mediterranean Oscillation index (MOi). In particular, the anomalies of the geopotential height field at 500 hPa are analyzed using segmentation of the Mediterranean basin in seven spatial windows: three at eastern and four at western. That is, different versions of an Upper-Level Mediterranean Oscillation index (ULMOi) were calculated, and monthly and annual variability of precipitation and temperature were analyzed for 53 observatories from 1951 to 2015. Best versions were selected according to the Pearson correlation, its related p value, and two measures of standardized error. The combination of the Balearic Sea and Libya/Egypt windows was the best for precipitation and temperature, respectively. The ULMOi showed the highest predictive ability in combination with the Atlantic Multidecadal Oscillation index (AMOi) for the annual temperature throughout the Mediterranean basin. The best model built from the indices presented a final mean error between 15 and 25% in annual precipitation for most of the studied area. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B53F..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B53F..01S">Climate as a driver of continent-wide irruptions in boreal seed-eating birds (Invited)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Strong, C.; Zuckerberg, B.; Betancourt, J. L. 2013-12-01 Boreal seed-eating birds regularly breed and overwinter throughout Canada and Alaska, but every few years these species demonstrate impressive irruptive migrations out of the boreal forest and into more southerly regions. It is thought that irruptive migrations are inversely dependent on a circumboreally synchronized pattern of seed crop fluctuations in boreal trees; seed-eating boreal birds stay in the north when food is plentiful, but sojourn south when food is scarce. Because both seed production and bird irruptions are characterized by periodicity ranging from biennial to decadal cycles, there is a strong possibility that these ecological phenomena are driven by climate variability. Using over twenty years of data from Project FeederWatch (a national citizen science project), we found that 'super irruptions' are correlated with continent-wide irruptive events in pine siskin population, and that these irruptions are associated with multi-decadal climate variability of Pacific origin. We also investigate how climate variability may influence the distribution of boreal bird species across different regions of North America during winter, and evaluate results in the context of limited banding data to assess possible geographic pathways of irruptions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://wwwpaztcn.wr.usgs.gov/julio_pdf/Gray_Yellowstone_QR.pdf','USGSPUBS'); return false;" href="http://wwwpaztcn.wr.usgs.gov/julio_pdf/Gray_Yellowstone_QR.pdf">Annual precipitation in the Yellowstone National Park region since AD 1173</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Gray, Stephen T.; Graumlich, Lisa J.; Betancourt, Julio L. 2007-01-01 Cores and cross sections from 133 limber pine (Pinus flexilis James) and Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) at four sites were used to estimate annual (July to June) precipitation in the Yellowstone National Park region for the period from AD 1173 to 1998. Examination of the long-term record shows that the early 20th century was markedly wet compared to the previous 700 yr. Extreme wet and dry years within the instrumental period fall within the range of past variability, and the magnitude of the worst-case droughts of the 20th century (AD 1930s and 1950s) was likely equaled or exceeded on numerous occasions before AD 1900. Spectral analysis showed significant decadal to multidecadal precipitation variability. At times this lower frequency variability produces strong regime-like behavior in regional precipitation, with the potential for rapid, high-amplitude switching between predominately wet and predominately dry conditions. Over multiple time scales, strong Yellowstone region precipitation anomalies were almost always associated with spatially extensive events spanning various combinations of the central and southern U.S. Rockies, the northern U.S.-Southern Canadian Rockies and the Pacific Northwest. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70030032','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70030032">Annual precipitation in the Yellowstone National Park region since AD 1173</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Gray, S.T.; Graumlich, L.J.; Betancourt, J.L. 2007-01-01 Cores and cross sections from 133 limber pine (Pinus flexilis James) and Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) at four sites were used to estimate annual (July to June) precipitation in the Yellowstone National Park region for the period from AD 1173 to 1998. Examination of the long-term record shows that the early 20th century was markedly wet compared to the previous 700??yr. Extreme wet and dry years within the instrumental period fall within the range of past variability, and the magnitude of the worst-case droughts of the 20th century (AD 1930s and 1950s) was likely equaled or exceeded on numerous occasions before AD 1900. Spectral analysis showed significant decadal to multidecadal precipitation variability. At times this lower frequency variability produces strong regime-like behavior in regional precipitation, with the potential for rapid, high-amplitude switching between predominately wet and predominately dry conditions. Over multiple time scales, strong Yellowstone region precipitation anomalies were almost always associated with spatially extensive events spanning various combinations of the central and southern U.S. Rockies, the northern U.S.-Southern Canadian Rockies and the Pacific Northwest. ?? 2007 University of Washington. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H43K1792G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H43K1792G">Determining the effect of key climate drivers on global hydropower production</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Galelli, S.; Ng, J. Y.; Lee, D.; Block, P. J. 2017-12-01 Accounting for about 17% of total global electrical power production, hydropower is arguably the world's main renewable energy source and a key asset to meet Paris climate agreements. A key component of hydropower production is water availability, which depends on both precipitation and multiple drivers of climate variability acting at different spatial and temporal scales. To understand how these drivers impact global hydropower production, we study the relation between four patterns of ocean-atmosphere climate variability (i.e., El Niño Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation, and Atlantic Multidecadal Oscillation) and monthly time series of electrical power production for over 1,500 hydropower reservoirs—obtained via simulation with a high-fidelity dam model forced with 20th century climate conditions. Notably significant relationships between electrical power productions and climate variability are found in many climate sensitive regions globally, including North and South America, East Asia, West Africa, and Europe. Coupled interactions from multiple, simultaneous climate drivers are also evaluated. Finally, we highlight the importance of using these climate drivers as an additional source of information within reservoir operating rules where the skillful predictability of inflow exists. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Sci...354.1419T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Sci...354.1419T">More tornadoes in the most extreme U.S. tornado outbreaks</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tippett, Michael K.; Lepore, Chiara; Cohen, Joel E. 2016-12-01 Tornadoes and severe thunderstorms kill people and damage property every year. Estimated U.S. insured losses due to severe thunderstorms in the first half of 2016 were $8.5 billion (US). The largest U.S. effects of tornadoes result from tornado outbreaks, which are sequences of tornadoes that occur in close succession. Here, using extreme value analysis, we find that the frequency of U.S. outbreaks with many tornadoes is increasing and that it is increasing faster for more extreme outbreaks. We model this behavior by extreme value distributions with parameters that are linear functions of time or of some indicators of multidecadal climatic variability. Extreme meteorological environments associated with severe thunderstorms show consistent upward trends, but the trends do not resemble those currently expected to result from global warming. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP53D..04E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP53D..04E">Connecting medieval megadroughts and surface climate in the Last Millennium Reanalysis</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Erb, M. P.; Emile-Geay, J.; Anderson, D. M.; Hakim, G. J.; Horlick, K. A.; Noone, D.; Perkins, W. A.; Steig, E. J.; Tardif, R. 2016-12-01 The North American Drought Atlas shows severe, long-lasting droughts during the Medieval Climate Anomaly. Because drought frequency and severity over the coming century is an area of vital interest, better understanding the causes of these historic droughts is crucial. A variety of research has suggested that a La Niña state was important for producing medieval megadroughts [1], and other work has indicated the potential roles of the Atlantic Multidecadal Oscillation [2] and internal atmospheric variability [3]. Correlations between drought and large-scale climate patterns also exist in the instrumental record [4], but understanding these relationships is far from complete. To investigate these relationships further, a data assimilation approach is employed. Proxy records - including tree rings, corals, and ice cores - are used to constrain climate states over the Common Era. By using general circulation model (GCM) output to quantify the covariances in the climate system, climate can be constrained not just at proxy sites but for all covarying locations and climate fields. Multiple GCMs will be employed to offset the limitations of imperfect model physics. This "Last Millennium Reanalysis" will be used to quantify relationships between North American medieval megadroughts and sea surface temperature patterns in the Atlantic and Pacific. 1. Cook, E. R., et al., Earth-Sci. Rev. 81, 93 (2007). 2. Oglesby, R., et al., Global Planet. Change 84-85, 56 (2012). 3. Stevenson, S., et al., J. Climate 28, 1865 (2015). 4. Cook, B. I., et al., J. Climate 27, 383 (2014). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GPC...162..175R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GPC...162..175R">A North American Hydroclimate Synthesis (NAHS) of the Common Era</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rodysill, Jessica R.; Anderson, Lesleigh; Cronin, Thomas M.; Jones, Miriam C.; Thompson, Robert S.; Wahl, David B.; Willard, Debra A.; Addison, Jason A.; Alder, Jay R.; Anderson, Katherine H.; Anderson, Lysanna; Barron, John A.; Bernhardt, Christopher E.; Hostetler, Steven W.; Kehrwald, Natalie M.; Khan, Nicole S.; Richey, Julie N.; Starratt, Scott W.; Strickland, Laura E.; Toomey, Michael R.; Treat, Claire C.; Wingard, G. Lynn 2018-03-01 This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow and runoff, cave drip rates, biological productivity, assemblages of living organisms, and salinity. Centennial-scale hydroclimate anomalies are obtained by iteratively sampling the proxy data on each of thousands of age model realizations and determining the fractions of possible time series indicating that the century-smoothed data was anomalously wet or dry relative to the 100 BCE to 1900 CE mean. Results suggest regionally asynchronous wet and dry periods over multidecadal to centennial timescales and frequent periods of extended regional drought. Most sites indicate drying during previously documented multicentennial periods of warmer Northern Hemisphere temperatures, particularly in the western U.S., central U.S., and Canada. Two widespread droughts were documented by the NAHS: from 50 BCE to 450 CE and from 800 to 1100 CE. Major hydroclimate reorganizations occurred out of sync with Northern Hemisphere temperature variations and widespread wet and dry anomalies occurred during both warm and cool periods. We present a broad assessment of paleoclimate relationships that highlights the potential influences of internal variability and external forcing and supports a prominent role for Pacific and Atlantic Ocean dynamics on century-scale continental hydroclimate. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1412032G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1412032G">Climate variability in China during the last millennium based on reconstructions and simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> García-Bustamante, E.; Luterbacher, J.; Xoplaki, E.; Werner, J. P.; Jungclaus, J.; Zorita, E.; González-Rouco, J. F.; Fernández-Donado, L.; Hegerl, G.; Ge, Q.; Hao, Z.; Wagner, S. 2012-04-01 Multi-decadal to centennial climate variability in China during the last millennium is analysed. We compare the low frequency temperature and precipitation variations from proxy-based reconstructions and palaeo-simulations from climate models. Focusing on the regional responses to the global climate evolution is of high relevance due to the complexity of the interactions between physical mechanisms at different spatio-temporal scales and the potential severity of the derived multiple socio-economic impacts. China stands out as a particularly interesting region, not only due to its complex climatic features, ranging from the semiarid northwestern Tibetan Plateau to the tropical monsoon southeastern climates, but also because of its wealth of proxy data. However, comprehensive assessments of proxy- and model-based information about palaeo-climatic variations in China are, to our knowledge, still lacking. In addition, existing studies depict a general lack of agreement between reconstructions and model simulations with respect to the amplitude and/or occurrence of warmer/colder and wetter/drier periods during the last millennium and the magnitude of the 20th century warming trend. Furthermore, these works are mainly focused on eastern China regions that show a denser proxy data coverage. We investigate how last millennium palaeo-runs compare to independent evidences from an unusual large number of proxy reconstructions over the study area by employing state-of-the-art palaeo-simulations with multi-member ensembles from the CMIP5/PMIP3 project. This shapes an ideal frame for the evaluation of the uncertainties associated to internal and intermodel model variability. Preliminary results indicate that despite the strong regional and seasonal dependencies, temperature reconstructions in China evidence coherent variations among all regions at centennial scale, especially during the last 500 years. The spatial consistency of low frequency temperature changes is an interesting aspect and of relevance for the assessment of forced climatic responses in China. The comparison between reconstructions and simulations from climate models show that, apart from the 20th century warming trend, the variance of the reconstructed mean China temperature lies in the envelope (uncertainty range) spanned by the temperature simulations. The uncertainty arises from the internal (multi-member ensembles) and the inter-model variability. Centennial variations tend to be broadly synchronous in the reconstructions and the simulations. However, the simulations show a delay of the warm period 1000-1300 AD. This warm medieval period both in the simulations and the reconstructions is followed by cooling till 1800 AD. Based on the simulations, the recent warming is not unprecedented and is comparable to the medieval warming. Further steps of this study will address the individual contribution of anthropogenic and natural forcings on climate variability and change during the last millennium in China. We will make use of of models that provide runs including single forcings (fingerprints) for the attribution of climate variations from decadal to multi-centennial time scales. With this aim, we will implement statistical techniques for the detection of optimal signal-to-noise-ratio between external forcings and internal variability of reconstructed temperatures and precipitation. To apply these approaches the uncertainties associated with both reconstructions and simulations will be estimated. The latter will shed some light into the mechanisms behind current climate evolution and will help to constrain uncertainties in the sensitivity of model simulations to increasing CO2 scenarios of future climate change. This work will also contribute to the overall aims of the PAGES 2k initiative in Asia (http://www.pages.unibe.ch/workinggroups/2k-network) </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AdG.....6..119G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AdG.....6..119G">Anoxic sediments off Central Peru record interannual to multidecadal changes of climate and upwelling ecosystem during the last two centuries</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gutiérrez, D.; Sifeddine, A.; Reyss, J. L.; Vargas, G.; Velazco, F.; Salvatteci, R.; Ferreira, V.; Ortlieb, L.; Field, D.; Baumgartner, T.; Boussafir, M.; Boucher, H.; Valdés, J.; Marinovic, L.; Soler, P.; Tapia, P. 2006-01-01 High-resolution paleo-environmental and paleo-ecological archives in laminated sequences are present in selected areas from the upper continental Peruvian margin within the oxygen minimum zone. We present initial results of a multidisciplinary study (the PALEOPECES project) that aims to reconstruct environmental and ecosystem variability during the past 200 years from high-resolution records. We report chronology development, sediment structure, elemental, organic, and mineralogical compositions of a box core collected at 300 m depth off Pisco, central Peru. An average sedimentation rate of 2.2 mm y-1 was estimated from downcore excess 210Pb activities for the last 100-150 years. Extending this rate further downcore indicates that a slump located at 52 cm depth from the top of the core can be correlated with a large tsunami that struck the coast of central Peru in 1746. X-ray analyses reveal laminated structures composed of couplets of light and dark laminae. Observations under polarized microscope show that light laminae are dominated by more dense, detrital and terrigenous material, while dark laminae are less dense with greater concentrations of amorphous biogenic silica. Downcore variations in dry bulk density and X-ray radioscopy of gray level show similar patterns, including a major shift at 34 cm depth (ca. mid-nineteenth century). A finely laminated sequence, which may include annual varves, is present between 34 cm depth and the slump layer. Sediment characteristics of the sequence suggest increased seasonality of terrigenous versus biogenous sedimentation during the corresponding period. In addition to a mid-nineteenth century change and considerable multidecadal variability in TOC, there is a positive trend in the past 50 years. Mineralogical analyses from a Fourier Transformed Infrared Spectroscopy (FTIR) of the upper core covering the last 25 years, indicate higher concentrations of the mineral fraction (quartz, feldspar, kaolinite and illite) in layers including large El Niño events (1982-1983, 1986-1987 and 1997-1998), with the largest peak during the 1997-1998 episode. These results confirm that anoxic sediments off Pisco are suitable archives to investigate interannual and decadal changes in oceanographic conditions and climate of the northern Humboldt upwelling system. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70036570','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70036570">Historical fire and multidecadal drought as context for piñon - Juniper woodland restoration in western Colorado</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Shinneman, Douglas J.; Baker, William L. 2009-01-01 Fire is known to structure tree populations, but the role of broad-scale climate variability is less clear. For example, the influence of climatic “teleconnections” (the relationship between oceanic–atmospheric fluctuations and anomalous weather patterns across broad scales) on forest age structure is relatively unexplored. We sampled semiarid piñon–juniper (Pinus edulis–Juniperus osteosperma) woodlands in western Colorado, USA, to test the hypothesis that woodland age structures are shaped by climate, including links to oceanic–atmospheric fluctuations, and by past fires and livestock grazing. Low-severity surface fire was lacking, as fire scars were absent, and did not influence woodland densities, but stand-replacing fires served as long-rotation (>400–600 years), stand-initiating events. Old-growth stands (>300 years old) were found in 75% of plots, consistent with a long fire rotation. Juniper and piñon age structures suggest contrasting responses during the past several centuries to dry and wet episodes linked to the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). Juniper density increased slightly during periods of drought, positive (warm) AMO (after ∼10-year lag), and negative (cool) PDO. In contrast, piñon populations may still be recovering from a long, drought-filled period (AD 1620–1820), with pulses of recovery favored during cool AMO, warm PDO, and above-average moisture periods. Analysis of 20th-century tree establishment and instrumental climate data corroborate the long-term relationships between age structure and climate. After Euro–American settlement (AD 1881), livestock grazing reduced understory grasses and forbs, reducing competition with tree seedlings and facilitating climate-induced increases in piñons. Thus tree populations in these woodlands are in flux, affected by drought and wet periods linked to oceanic–atmospheric variability, Euro–American livestock grazing, and long-rotation, high-severity fires. Reductions in livestock grazing levels may aid ecological restoration efforts. However, given long-term fluctuations in tree density and composition, and expected further drought, thinning or burning to reduce tree populations may be misdirected. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27151406','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27151406">Fine-scale climate change: modelling spatial variation in biologically meaningful rates of warming.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Maclean, Ilya M D; Suggitt, Andrew J; Wilson, Robert J; Duffy, James P; Bennie, Jonathan J 2017-01-01 The existence of fine-grain climate heterogeneity has prompted suggestions that species may be able to survive future climate change in pockets of suitable microclimate, termed 'microrefugia'. However, evidence for microrefugia is hindered by lack of understanding of how rates of warming vary across a landscape. Here, we present a model that is applied to provide fine-grained, multidecadal estimates of temperature change based on the underlying physical processes that influence microclimate. Weather station and remotely derived environmental data were used to construct physical variables that capture the effects of terrain, sea surface temperatures, altitude and surface albedo on local temperatures, which were then calibrated statistically to derive gridded estimates of temperature. We apply the model to the Lizard Peninsula, United Kingdom, to provide accurate (mean error = 1.21 °C; RMS error = 1.63 °C) hourly estimates of temperature at a resolution of 100 m for the period 1977-2014. We show that rates of warming vary across a landscape primarily due to long-term trends in weather conditions. Total warming varied from 0.87 to 1.16 °C, with the slowest rates of warming evident on north-east-facing slopes. This variation contributed to substantial spatial heterogeneity in trends in bioclimatic variables: for example, the change in the length of the frost-free season varied from +11 to -54 days and the increase in annual growing degree-days from 51 to 267 °C days. Spatial variation in warming was caused primarily by a decrease in daytime cloud cover with a resulting increase in received solar radiation, and secondarily by a decrease in the strength of westerly winds, which has amplified the effects on temperature of solar radiation on west-facing slopes. We emphasize the importance of multidecadal trends in weather conditions in determining spatial variation in rates of warming, suggesting that locations experiencing least warming may not remain consistent under future climate change. © 2016 John Wiley & Sons Ltd. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ERL....12j4005B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ERL....12j4005B">Decadal climate variability and the spatial organization of deep hydrological drought</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barros, Ana P.; Hodes, Jared L.; Arulraj, Malarvizhi 2017-10-01 Empirical Orthogonal Function (EOF), wavelet, and wavelet coherence analysis of baseflow time-series from 126 streamgauges (record-length > 50 years; small and mid-size watersheds) in the US South Atlantic (USSA) region reveal three principal modes of space-time variability: (1) a region-wide dominant mode tied to annual precipitation that exhibits non-stationary decadal variability after the mid 1990s concurrent with the warming of the AMO (Atlantic Multidecadal Oscillation); (2) two spatial modes, east and west of the Blue Ridge, exhibiting nonstationary seasonal to sub-decadal variability before and after 1990 attributed to complex nonlinear interactions between ENSO and AMO impacting precipitation and recharge; and (3) deep (decadal) and shallow (< 6 years) space-time modes of groundwater variability separating basins with high and low annual mean baseflow fraction (MBF) by physiographic region. The results explain the propagation of multiscale climate variability into the regional groundwater system through recharge modulated by topography, geomorphology, and geology to determine the spatial organization of baseflow variability at decadal (and longer) time-scales, that is, deep hydrologic drought. Further, these findings suggest potential for long-range predictability of hydrological drought in small and mid-size watersheds, where baseflow is a robust indicator of nonstationary yield capacity of the underlying groundwater basins. Predictive associations between climate mode indices and deep baseflow (e.g. persistent decreases of the decadal-scale components of baseflow during the cold phase of the AMO in the USSA) can be instrumental toward improving forecast lead-times and long-range mitigation of severe drought. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017WRR....53.3047H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017WRR....53.3047H">Multiscale temporal variability and regional patterns in 555 years of conterminous U.S. streamflow</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ho, Michelle; Lall, Upmanu; Sun, Xun; Cook, Edward R. 2017-04-01 The development of paleoclimate streamflow reconstructions in the conterminous United States (CONUS) has provided water resource managers with improved insights into multidecadal and centennial scale variability that cannot be reliably detected using shorter instrumental records. Paleoclimate streamflow reconstructions have largely focused on individual catchments limiting the ability to quantify variability across the CONUS. The Living Blended Drought Atlas (LBDA), a spatially and temporally complete 555 year long paleoclimate record of summer drought across the CONUS, provides an opportunity to reconstruct and characterize streamflow variability at a continental scale. We explore the validity of the first paleoreconstructions of streamflow that span the CONUS informed by the LBDA targeting a set of U.S. Geological Survey streamflow sites. The reconstructions are skillful under cross validation across most of the country, but the variance explained is generally low. Spatial and temporal structures of streamflow variability are analyzed using hierarchical clustering, principal component analysis, and wavelet analyses. Nine spatially coherent clusters are identified. The reconstructions show signals of contemporary droughts such as the Dust Bowl (1930s) and 1950s droughts. Decadal-scale variability was detected in the late 1900s in the western U.S., however, similar modes of temporal variability were rarely present prior to the 1950s. The twentieth century featured longer wet spells and shorter dry spells compared with the preceding 450 years. Streamflows in the Pacific Northwest and Northeast are negatively correlated with the central U.S. suggesting the potential to mitigate some drought impacts by balancing economic activities and insurance pools across these regions during major droughts. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ems..confE.144D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ems..confE.144D">Extense historical droughts in Spain derived from documentary sources</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dominguez-Castro, F.; García-Herrera, R.; Barriendos, M. 2009-09-01 Documentary records, specially those from rogation ceremonies have been extensively used to build proxy series of droughts and floods in Spain. Most of the work done previously has focused in the abstraction of the documents and building of the individual series, but less attention has been paid to the joint analysis of this type of records. This is problematic because, due to the diversity of Spanish climates, the climatological meaning of the rogation ceremonies changes depending on the considered region. This paper aims to analyse the spatial extension of drought events from the rogation records from Barcelona, Bilbao, Gerona, Murcia, Seville, Tarragona, Toledo, Tortosa and Zamora, which cover the 16th to 19th centuries. The representativeness of each of them is analysed taking into account the local climate and the series variability. Then the spatial scale of the recorded droughts is examined at seasonal scale. The results show high multidecadal variability, with the driest periods at national scale recorded during the 1680s, 1730s and 1780s. Finally, the dry years of 1680, 1683 and 1817 are analysed in detail. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoRL..40.3180L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoRL..40.3180L">Recent 121-year variability of western boundary upwelling in the northern South China Sea</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liu, Yi; Peng, Zicheng; Shen, Chuan-Chou; Zhou, Renjun; Song, Shaohua; Shi, Zhengguo; Chen, Tegu; Wei, Gangjian; Delong, Kristine L. 2013-06-01 upwelling is typically related to the eastern boundary upwelling system, whereas the powerful southwest Asian summer monsoon can also generate significant cold, nutrient-rich deep water in western coastal zones. Here we present a sea surface temperature record (A.D. 1876-1996) derived from coral Porites Sr/Ca for an upwelling zone in the northern South China Sea. The upwelling-induced sea surface temperature anomaly record reveals prominent multidecadal variability driven by Asian summer monsoon dynamics with an abrupt transition from warmer to colder conditions in 1930, and a return to warmer conditions after 1960. Previous studies suggest the expected increase in atmospheric CO2 for the coming decades may result in intensification in the eastern boundary upwelling system, which could enhance upwelling of CO2-rich deep water thus exacerbating the impact of acidification in these productive zones. In contrast, the weakening trend since 1961 in the upwelling time series from the northern South China Sea suggests moderate regional ocean acidification from upwelling thus a stress relief for marine life in this region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24516152','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24516152">A 3,500-year tree-ring record of annual precipitation on the northeastern Tibetan Plateau.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yang, Bao; Qin, Chun; Wang, Jianglin; He, Minhui; Melvin, Thomas M; Osborn, Timothy J; Briffa, Keith R 2014-02-25 An annually resolved and absolutely dated ring-width chronology spanning 4,500 y has been constructed using subfossil, archaeological, and living-tree juniper samples from the northeastern Tibetan Plateau. The chronology represents changing mean annual precipitation and is most reliable after 1500 B.C. Reconstructed precipitation for this period displays a trend toward more moist conditions: the last 10-, 25-, and 50-y periods all appear to be the wettest in at least three and a half millennia. Notable historical dry periods occurred in the 4th century BCE and in the second half of the 15th century CE. The driest individual year reconstructed (since 1500 B.C.) is 1048 B.C., whereas the wettest is 2010. Precipitation variability in this region appears not to be associated with inferred changes in Asian monsoon intensity during recent millennia. The chronology displays a statistical association with the multidecadal and longer-term variability of reconstructed mean Northern Hemisphere temperatures over the last two millennia. This suggests that any further large-scale warming might be associated with even greater moisture supply in this region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.131.1133E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.131.1133E">Drivers of long-term precipitation and runoff variability in the southeastern USA</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Engström, Johanna; Waylen, Peter 2018-02-01 The hydroclimatology of the southeastern USA (AL, GA, NC, SC, and TN) is analyzed from a holistic perspective, including multiple climate drivers. Monthly precipitation modeled by the PRISM group and runoff data (1952-2011) from 18 basins are analyzed using a single-field based principal component's analysis. Results indicate that the Atlantic Multidecadal Oscillation and El Niño-Southern Oscillation are the main atmospheric drivers of hydroclimate variability in the region, sometimes operating at several months' lag. Their influence is the strongest in the fall through spring, which corresponds with the dry season in the southern parts of the study area thereby increasing pressure on already limited water resources. The Arctic Oscillation, North Atlantic Oscillation, and Pacific-North American patterns vary on shorter-term bases, and also show a significant, but temporally more sporadic influence. Insight is also brought to the ongoing discussion, confirming the disassociation of the Arctic and North Atlantic Oscillation. Findings can be used in water resources forecasting, giving an indication of expected water volumes several months ahead. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A21B0029T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A21B0029T">Ocean carbon and heat variability in an Earth System Model</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Thomas, J. L.; Waugh, D.; Gnanadesikan, A. 2016-12-01 Ocean carbon and heat content are very important for regulating global climate. Furthermore, due to lack of observations and dependence on parameterizations, there has been little consensus in the modeling community on the magnitude of realistic ocean carbon and heat content variability, particularly in the Southern Ocean. We assess the differences between global oceanic heat and carbon content variability in GFDL ESM2Mc using a 500-year, pre-industrial control simulation. The global carbon and heat content are directly out of phase with each other; however, in the Southern Ocean the heat and carbon content are in phase. The global heat mutli-decadal variability is primarily explained by variability in the tropics and mid-latitudes, while the variability in global carbon content is primarily explained by Southern Ocean variability. In order to test the robustness of this relationship, we use three additional pre-industrial control simulations using different mesoscale mixing parameterizations. Three pre-industrial control simulations are conducted with the along-isopycnal diffusion coefficient (Aredi) set to constant values of 400, 800 (control) and 2400 m2 s-1. These values for Aredi are within the range of parameter settings commonly used in modeling groups. Finally, one pre-industrial control simulation is conducted where the minimum in the Gent-McWilliams parameterization closure scheme (AGM) increased to 600 m2 s-1. We find that the different simulations have very different multi-decadal variability, especially in the Weddell Sea where the characteristics of deep convection are drastically changed. While the temporal frequency and amplitude global heat and carbon content changes significantly, the overall spatial pattern of variability remains unchanged between the simulations. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JASTP.128...92S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JASTP.128...92S">Response to the comment on: “Soon, W., and Legates, D.R., solar irradiance modulation of equator-to-pole (Arctic) temperature gradients: empirical evidence for climate variation on multi-decadal timescales. Journal of Atmospheric and solar-terrestrial physics, 93, (2013) 45-56” by F. Meunier and A. H. Reis</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Soon, Willie; Legates, David R. 2015-06-01 We thank Meunier and Reis (hereafter as MR) for their comments on our paper. We, however, do not see the relevance of their alternative interpretation to our original results and believe this reflects their confusion regarding our conclusions rather than a discussion on physical mechanisms. </ce:displayed-quote></ce:para>In the context of this quote, note that even Pallé et al. (2009:3)admitted that “while the deseasonalized CERES data has a small year to year variability (Fig. 2 of Pallé et al., 2009), the Earthshine data seem to present overly large interannual anomalies, along with a large size of the error bars associated to the yearly means [which] is mostly due to sampling issues, as Earthshine measurements are taken from a single station.”</ce:para>To put this in a different way, the relatively short duration of Earthshine or satellite-borne measurements of global albedo is unable to provide the necessary information on how this important quantity may vary on multi-decadal timescales as studies by Soon and Legates (2013). We note that efforts to 'reconstruct' Earth albedo over a 120-to-130 year period have been discussed by Zavalishin (2014) but we stress that such research requires non-independent information regarding surface temperatures and some unproven assumptions about the thermal inertia of the hydrosphere.</ce:para></ce:sections></ja:body><ja:simple-tail view="all"><ce:bibliography </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26132268','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26132268">Regime Shift in an Exploited Fish Community Related to Natural Climate Oscillations.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Auber, Arnaud; Travers-Trolet, Morgane; Villanueva, Maria Ching; Ernande, Bruno 2015-01-01 Identifying the various drivers of marine ecosystem regime shifts and disentangling their respective influence are critical tasks for understanding biodiversity dynamics and properly managing exploited living resources such as marine fish communities. Unfortunately, the mechanisms and forcing factors underlying regime shifts in marine fish communities are still largely unknown although climate forcing and anthropogenic pressures such as fishing have been suggested as key determinants. Based on a 24-year-long time-series of scientific surveys monitoring 55 fish and cephalopods species, we report here a rapid and persistent structural change in the exploited fish community of the eastern English Channel from strong to moderate dominance of small-bodied forage fish species with low temperature preferendum that occurred in the mid-1990s. This shift was related to a concomitant warming of the North Atlantic Ocean as attested by a switch of the Atlantic Multidecadal Oscillation from a cold to a warm phase. Interestingly, observed changes in the fish community structure were opposite to those classically induced by exploitation as larger fish species of higher trophic level increased in abundance. Despite not playing a direct role in the regime shift, fishing still appeared as a forcing factor affecting community structure. Moreover, although related to climate, the regime shift may have been facilitated by strong historic exploitation that certainly primed the system by favoring the large dominance of small-bodied fish species that are particularly sensitive to climatic variations. These results emphasize that particular attention should be paid to multidecadal natural climate variability and its interactions with both fishing and climate warming when aiming at sustainable exploitation and ecosystem conservation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.S51C..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.S51C..04A">Multi-Decadal analysis of Global Trends in Microseism Intensity: A Proxy for Changes in Extremal Storm Activity and Oceanic Wave State</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Anthony, R. E.; Aster, R. C.; Rowe, C. A. 2016-12-01 The Earth's seismic noise spectrum features two globally ubiquitous peaks near 8 and 16 s periods (secondary and primary bands) that arise when storm-generated ocean gravity waves are converted to seismic energy, predominantly into Rayleigh waves. Because of its regionally integrative nature, microseism intensity and other seismographic data from long running sites can provide useful proxies for wave state. Expanding an earlier study of global microseism trends (Aster et al., 2010), we analyze digitally-archived, up-to-date (through late 2016) multi-decadal seismic data from stations of global seismographic networks to characterize the spatiotemporal evolution of wave climate over the past >20 years. The IRIS Noise Tool Kit (Bahavair et al., 2013) is used to produce ground motion power spectral density (PSD) estimates in 3-hour overlapping time series segments. The result of this effort is a longer duration and more broadly geographically distributed PSD database than attained in previous studies, particularly for the primary microseism band. Integrating power within the primary and secondary microseism bands enables regional characterization of spatially-integrated trends in wave states and storm event statistics of varying thresholds. The results of these analyses are then interpreted within the context of recognized modes of atmospheric variability, including the particularly strong 2015-2016 El Niño. We note a number of statistically significant increasing trends in both raw microseism power and storm activity occurring at multiple stations in the Northwest Atlantic and Southeast Pacific consistent with generally increased wave heights and storminess in these regions. Such trends in wave activity have the potential to significantly influence coastal environments particularly under rising global sea levels. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP21B2288S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP21B2288S">Multidecadally resolved Asian summer monsoon dynamics during MIS 5a-5d</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shen, C. C.; Jiang, X.; Hu, H. M.; Spoetl, C. 2016-12-01 A strong correlation between the Asian summer monsoon (ASM) and the North Atlantic climate on millennial and sub-millennial timescales during the last glacial period (MIS 4-2) and deglacial sequence has been demonstrated. However, our knowledge of this millennial- and sub-millennial-scale climatic link before MIS 4 is limited. Here, we present a new U-Th-dated absolute chronology of ASM variability from 113.5 to 86.6 kyr BP, covering marine isotope stages (MIS) 5a-5d. This integrated multidecadally resolved record, based on 1435 oxygen isotope data and 46 U-Th dates with 2-sigma errors as low as ±0.3 kyr from three stalagmites collected in Sanxing Cave, southwestern China, can be a reference for calibrating paleoclimate proxy sequences. The Sanxing oxygen isotope record follows the 23 kyr precessional cycle of insolation and is punctuated by prominent millennial-scale oscillations of the Chinese Interstadials (CIS) 25 to 22, corresponding to Greenland Interstadials (GIS) 25 to 22. A centennial-scale precursor event at 104.1 ± 0.3 kyr BP preceding CIS 23 is clearly registered. These events in the Sanxing record are synchronous with those identified in stalagmites from the European Alps (NALPS), except for the onset of GIS 25 and the end of GIS 22, and are up to 2.3 kyr older than the corresponding ones in Greenland ice core records. The high degree of similarity of the oxygen isotope records between Sanxing Cave and Greenland supports the northern hemisphere forcing of the ASM. The anti-phase relationship of oxygen isotope records between Sanxing stalagmites and Antarctic ice cores suggests an additional ASM linkage to the Southern Hemisphere. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017QSRv..170...69A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017QSRv..170...69A">Ocean-atmosphere interactions as drivers of mid-to-late Holocene rapid climate changes: Evidence from high-resolution stalagmite records at DeSoto Caverns, Southeast USA</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Aharon, Paul; Dhungana, Rajesh 2017-08-01 Oxygen and carbon isotope time-series derived from an actively growing aragonitic stalagmite in DeSoto Caverns exhibit with unusual clarity rapid hydroclimate changes in the mid-to-late Holocene. Data consist of 1884 δ18O and δ13C determinations whose chronology is anchored on 35 230Th/234U absolute dates in the interval 6.0-1.1 cal ka BP. Exceptional 18O and 13C-enrichments centered at 4.8 ± 0.14 cal ka BP likely represent the imprints of a severe drought. Isotope cycles from 4.7 to 1.3 cal ka BP, exhibit a dominant periodicity of 68 ± 4 yrs. A gradual cooling trend of ∼0.6 °C/103 yrs is attributed to a declining seasonal contrast in insolation. The synchronicity of the mega-drought in the Southeast US with the (1) termination of the African Humid Period; (ii) abrupt reduction of the North Atlantic Deep Water production, and (iii) rapid sea-ice expansion in the polar regions of both Hemispheres testifies to the global extent and rapidity of the "5 ka" event and points to the North Atlantic Deep Water variability as the likely controlling factor. The multidecadal cycles are consistent with alternating dry and wet summers occurring during a long-term switch in the seasonal rainfall amount dominance from winter to summer. The periodic summer droughts in the Southeast US support climate models that predict profound hydroclimate changes in the late Holocene governed by the Atlantic Multidecadal Oscillation. The relatively short and rapid hydroclimate phase transitions documented in this study introduce a complication in the correlation of late Holocene drought events that had significant societal impacts. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25452247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25452247">Plant communities on infertile soils are less sensitive to climate change.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Harrison, Susan; Damschen, Ellen; Fernandez-Going, Barbara; Eskelinen, Anu; Copeland, Stella 2015-11-01 Much evidence suggests that plant communities on infertile soils are relatively insensitive to increased water deficit caused by increasing temperature and/or decreasing precipitation. However, a multi-decadal study of community change in the western USA does not support this conclusion. This paper tests explanations related to macroclimatic differences, overstorey effects on microclimate, variation in soil texture and plant functional traits. A re-analysis was undertaken of the changes in the multi-decadal study, which concerned forest understorey communities on infertile (serpentine) and fertile soils in an aridifying climate (southern Oregan) from 1949-1951 to 2007-2008. Macroclimatic variables, overstorey cover and soil texture were used as new covariates. As an alternative measure of climate-related change, the community mean value of specific leaf area was used, a functional trait measuring drought tolerance. We investigated whether these revised analyses supported the prediction of lesser sensitivity to climate change in understorey communities on infertile serpentine soils. Overstorey cover, but not macroclimate or soil texture, was a significant covariate of community change over time. It strongly buffered understorey temperatures, was correlated with less change and averaged >50 % lower on serpentine soils, thereby counteracting the lower climate sensitivity of understorey herbs on these soils. Community mean specific leaf area showed the predicted pattern of less change over time in serpentine than non-serpentine communities. Based on the current balance of evidence, plant communities on infertile serpentine soils are less sensitive to changes in the climatic water balance than communities on more fertile soils. However, this advantage may in some cases be lessened by their sparser overstorey cover. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMIN52A..03H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMIN52A..03H">Adding Semantics and OPM Ontology for the Provenance of Multi-sensor Merged Climate Data Records. Now What About Reproducibility?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hua, H.; Wilson, B. D.; Manipon, G.; Pan, L.; Fetzer, E. 2011-12-01 Multi-decadal climate data records are critical to studying climate variability and change. These often also require merging data from multiple instruments such as those from NASA's A-Train that contain measurements covering a wide range of atmospheric conditions and phenomena. Multi-decadal climate data record of water vapor measurements from sensors on A-Train, operational weather, and other satellites are being assembled from existing data sources, or produced from well-established methods published in peer-reviewed literature. However, the immense volume and inhomogeneity of data often requires an "exploratory computing" approach to product generation where data is processed in a variety of different ways with varying algorithms, parameters, and code changes until an acceptable intermediate product is generated. This process is repeated until a desirable final merged product can be generated. Typically the production legacy is often lost due to the complexity of processing steps that were tried along the way. The data product information associated with source data, processing methods, parameters used, intermediate product outputs, and associated materials are often hidden in each of the trials and scattered throughout the processing system(s). We will discuss methods to help users better capture and explore the production legacy of the data, metadata, ancillary files, code, and computing environment changes used during the production of these merged and multi-sensor data products. By leveraging existing semantic and provenance tools, we can capture sufficient information to enable users to track, perform faceted searches, and visualize the provenance of the products and processing lineage. We will explore if sufficient provenance information can be captured to enable science reproducibility of these climate data records. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QSRv..143....1J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QSRv..143....1J">Precisely dated multidecadally resolved Asian summer monsoon dynamics 113.5-86.6 thousand years ago</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jiang, Xiuyang; Wang, Xiaoyan; He, Yaoqi; Hu, Hsun-Ming; Li, Zhizhong; Spötl, Christoph; Shen, Chuan-Chou 2016-07-01 We present a new 230Th-dated absolute chronology of Asian summer monsoon (ASM) variability from 113.5 to 86.6 kyr BP (before 1950 AD). This integrated multidecadally resolved record, based on 1435 oxygen isotope data and 46 230Th dates with 2-sigma errors as low as ±0.3 kyr from three stalagmites collected in Sanxing Cave, southwestern China, can be a new reference for calibrating paleoclimate proxy sequences. The Sanxing δ18O record follows the 23 kyr precessional cycle of insolation and is punctuated by prominent millennial-scale oscillations of the Chinese Interstadials (CIS) 25 to 22, corresponding to Greenland Interstadials (GIS) 25 to 22. The onset of CIS 25, 24, 23 and 22 is dated to 113.1 ± 0.4, 108.1 ± 0.3, 103.7 ± 0.3 and 91.4 ± 0.6 kyr BP in the Sanxing record, respectively. The end of CIS 24 and CIS 22 is constrained to 105.5 ± 0.4 and 87.7 ± 0.3 kyr BP, respectively. A centennial-scale precursor event at 104.1 ± 0.3 kyr BP preceding CIS 23 is clearly registered. These events in the Sanxing record are synchronous with those identified in stalagmites from the European Alps (NALPS), except for the onset of GIS 25 and the end of GIS 22, and differ by up to 2.3 kyr from the corresponding ones in Greenland ice core records. The high degree of similarity of the δ18O records between Sanxing Cave and Greenland supports a Northern Hemisphere forcing of the ASM. The anti-phase relationship of δ18O records between Sanxing stalagmites and Antarctic ice cores suggests an additional ASM linkage to the Southern Hemisphere. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27934705','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27934705">More tornadoes in the most extreme U.S. tornado outbreaks.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tippett, Michael K; Lepore, Chiara; Cohen, Joel E 2016-12-16 Tornadoes and severe thunderstorms kill people and damage property every year. Estimated U.S. insured losses due to severe thunderstorms in the first half of 2016 were $8.5 billion (US). The largest U.S. effects of tornadoes result from tornado outbreaks, which are sequences of tornadoes that occur in close succession. Here, using extreme value analysis, we find that the frequency of U.S. outbreaks with many tornadoes is increasing and that it is increasing faster for more extreme outbreaks. We model this behavior by extreme value distributions with parameters that are linear functions of time or of some indicators of multidecadal climatic variability. Extreme meteorological environments associated with severe thunderstorms show consistent upward trends, but the trends do not resemble those currently expected to result from global warming. Copyright © 2016, American Association for the Advancement of Science. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3996540','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3996540">Timescales for detecting a significant acceleration in sea level rise</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Haigh, Ivan D.; Wahl, Thomas; Rohling, Eelco J.; Price, René M.; Pattiaratchi, Charitha B.; Calafat, Francisco M.; Dangendorf, Sönke 2014-01-01 There is observational evidence that global sea level is rising and there is concern that the rate of rise will increase, significantly threatening coastal communities. However, considerable debate remains as to whether the rate of sea level rise is currently increasing and, if so, by how much. Here we provide new insights into sea level accelerations by applying the main methods that have been used previously to search for accelerations in historical data, to identify the timings (with uncertainties) at which accelerations might first be recognized in a statistically significant manner (if not apparent already) in sea level records that we have artificially extended to 2100. We find that the most important approach to earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual to multidecadal variability in sea level records. PMID:24728012 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24305146','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24305146">North Atlantic warming and the retreat of Greenland's outlet glaciers.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Straneo, Fiammetta; Heimbach, Patrick 2013-12-05 Mass loss from the Greenland ice sheet quadrupled over the past two decades, contributing a quarter of the observed global sea-level rise. Increased submarine melting is thought to have triggered the retreat of Greenland's outlet glaciers, which is partly responsible for the ice loss. However, the chain of events and physical processes remain elusive. Recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes, multidecadal natural ocean variability and a long-term increase in the North Atlantic's upper ocean heat content since the 1950s all contributed to a warming of the subpolar North Atlantic. This led, in conjunction with increased runoff, to enhanced submarine glacier melting. Future climate projections raise the potential for continued increases in warming and ice-mass loss, with implications for sea level and climate. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A53B0286A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A53B0286A">Atmospheric Circulation and West Greenland Precipitation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Auger, J.; Birkel, S. D.; Maasch, K. A.; Schuenemann, K. C.; Mayewski, P. A.; Osterberg, E. C.; Hawley, R. L.; Marshall, H. P. 2016-12-01 The surface mass balance of the Greenland Ice Sheet has declined substantially in recent decades across West Greenland with important implications for global sea level and freshwater resources. Here, we investigate changes in heat and moisture delivery to West Greenland through changes in atmospheric circulation in order to gain insight into possible future climate. Particular focus is placed on the role of known climate variability, including the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO), in influencing the intensity, frequency, and track of cyclones across the North Atlantic. This study utilizes multiple daily climate reanalysis models (CFSR, ERA-Interim, JRA-55) in addition to observational data. Preliminary results indicate a primary influence from the NAO, with a secondary influence from the low frequency oscillation connected to the AMO. Work is ongoing, and a complete synthesis will be presented at the fall meeting. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ems..confE.593Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ems..confE.593Z">European temperature records of the past five centuries based on documentary information compared to climate simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zorita, E. 2009-09-01 Two European temperature records for the past half-millennium, January-to-April air temperature for Stockholm (Sweden) and seasonal temperature for a Central European region, both derived from the analysis of documentary sources combined with long instrumental records, are compared with the output of forced (solar, volcanic, greenhouse gases) climate simulations with the model ECHO-G. The analysis is complemented with the long (early)-instrumental record of Central England Temperature (CET). Both approaches to study past climates (simulations and reconstructions) are burdened with uncertainties. The main objective of this comparative analysis is to identify robust features and weaknesses that may help to improve models and reconstruction methods. The results indicate a general agreement between simulations and the reconstructed Stockholm and CET records regarding the long-term temperature trend over the recent centuries, suggesting a reasonable choice of the amplitude of the solar forcing in the simulations and sensitivity of the model to the external forcing. However, the Stockholm reconstruction and the CET record also show a long and clear multi-decadal warm episode peaking around 1730, which is absent in the simulations. The uncertainties associated with the reconstruction method or with the simulated internal climate variability cannot easily explain this difference. Regarding the interannual variability, the Stockholm series displays in some periods higher amplitudes than the simulations but these differences are within the statistical uncertainty and further decrease if output from a regional model driven by the global model is used. The long-term trends in the simulations and reconstructions of the Central European temperature agree less well. The reconstructed temperature displays, for all seasons, a smaller difference between the present climate and past centuries than the simulations. Possible reasons for these differences may be related to a limitation of the traditional technique for converting documentary evidence to temperature values to capture long-term climate changes, because the documents often reflect temperatures relative to the contemporary authors' own perception of what constituted 'normal' conditions. By contrast, the simulated and reconstructed inter-annual variability is in rather good agreement. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70047945','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70047945">Implications of multi-scale sea level and climate variability for coastal resources</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Karamperidou, Christina; Engel, Victor; Lall, Upmanu; Stabenau, Erik; Smith, Thomas J. 2013-01-01 While secular changes in regional sea levels and their implications for coastal zone management have been studied extensively, less attention is being paid to natural fluctuations in sea levels, whose interaction with a higher mean level could have significant impacts on low-lying areas, such as wetlands. Here, the long record of sea level at Key West, FL is studied in terms of both the secular trend and the multi-scale sea level variations. This analysis is then used to explore implications for the Everglades National Park (ENP), which is recognized internationally for its ecological significance, and is the site of the largest wetland restoration project in the world. Very shallow topographic gradients (3–6 cm per km) make the region susceptible to small changes in sea level. Observations of surface water levels from a monitoring network within ENP exhibit both the long-term trends and the interannual-to-(multi)decadal variability that are observed in the Key West record. Water levels recorded at four long-term monitoring stations within ENP exhibit increasing trends approximately equal to or larger than the long-term trend at Key West. Time- and frequency-domain analyses highlight the potential influence of climate mechanisms, such as the El Niño/Southern Oscillation and the North Atlantic Oscillation (NAO), on Key West sea levels and marsh water levels, and the potential modulation of their influence by the background state of the North Atlantic Sea Surface Temperatures. In particular, the Key West sea levels are found to be positively correlated with the NAO index, while the two series exhibit high spectral power during the transition to a cold Atlantic Multidecadal Oscillation (AMO). The correlation between the Key West sea levels and the NINO3 Index reverses its sign in coincidence with a reversal of the AMO phase. Water levels in ENP are also influenced by precipitation and freshwater releases from the northern boundary of the Park. The analysis of both climate variability and climate change in such wetlands is needed to inform management practices in coastal wetland zones around the world. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS22B..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS22B..07W">Enhanced Biennial Variability in the Pacific due to Atlantic Capacitor Effect after the Early 1990s</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> WANG, L.; Yu, J. Y.; Paek, H. 2016-12-01 The El Niño-Southern Oscillation (ENSO) and Pacific subtropical highs (PSHs) have major impacts on social and ecological systems through their influences on severe natural hazards including tropical storms, coastal erosions, droughts and floods. The ability to forecast ENSO and PSHs requires an understanding of the underlying physical mechanisms that drive their variability. Here we present an Atlantic capacitor effect mechanism to suggest the Atlantic as a key pacemaker of the biennial variability in the Pacific including ENSO and PSHs in recent decades, while the pacemaker was previously considered to be mainly lied within the Pacific or Indian Oceans. The "charging" (i.e., ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and "discharging" (i.e., the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) process works alternately, generating the biennial rhythmic changes in the Pacific. After the early-1990s, the positive phase of the Atlantic Multidecadal Oscillation and global warming provides more favorable background states over the NTA that enable the Atlantic capacitor effect to operate more efficiently, giving rise to enhanced biennial variability in the Pacific which may increase the occurrence frequency of severe natural hazard events. The results highlight the increasing important role of the Atlantic-Pacific coupling as an important pacemaker of the ENSO cycle in recent decades. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19965473','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19965473">Climate-driven basin-scale decadal oscillations of oceanic phytoplankton.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Martinez, Elodie; Antoine, David; D'Ortenzio, Fabrizio; Gentili, Bernard 2009-11-27 Phytoplankton--the microalgae that populate the upper lit layers of the ocean--fuel the oceanic food web and affect oceanic and atmospheric carbon dioxide levels through photosynthetic carbon fixation. Here, we show that multidecadal changes in global phytoplankton abundances are related to basin-scale oscillations of the physical ocean, specifically the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation. This relationship is revealed in approximately 20 years of satellite observations of chlorophyll and sea surface temperature. Interaction between the main pycnocline and the upper ocean seasonal mixed layer is one mechanism behind this correlation. Our findings provide a context for the interpretation of contemporary changes in global phytoplankton and should improve predictions of their future evolution with climate change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009282','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009282">Integrated Data Modeling and Simulation on the Joint Polar Satellite System Program</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Roberts, Christopher J.; Boyce, Leslye; Smith, Gary; Li, Angela; Barrett, Larry 2012-01-01 The Joint Polar Satellite System is a modern, large-scale, complex, multi-mission aerospace program, and presents a variety of design, testing and operational challenges due to: (1) System Scope: multi-mission coordination, role, responsibility and accountability challenges stemming from porous/ill-defined system and organizational boundaries (including foreign policy interactions) (2) Degree of Concurrency: design, implementation, integration, verification and operation occurring simultaneously, at multiple scales in the system hierarchy (3) Multi-Decadal Lifecycle: technical obsolesce, reliability and sustainment concerns, including those related to organizational and industrial base. Additionally, these systems tend to become embedded in the broader societal infrastructure, resulting in new system stakeholders with perhaps different preferences (4) Barriers to Effective Communications: process and cultural issues that emerge due to geographic dispersion and as one spans boundaries including gov./contractor, NASA/Other USG, and international relationships. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHyd..555..108C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHyd..555..108C">Oscillations and trends of river discharge in the southern Central Andes and linkages with climate variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred R. 2017-12-01 This study analyzes the discharge variability of small to medium drainage basins (102-104 km2) in the southern Central Andes of NW Argentina. The Hilbert-Huang Transform (HHT) was applied to evaluate non-stationary oscillatory modes of variability and trends, based on four time series of monthly-normalized discharge anomaly between 1940 and 2015. Statistically significant trends reveal increasing discharge during the past decades and document an intensification of the hydrological cycle during this period. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be best described by five quasi-periodic statistically significant oscillatory modes, with mean periods varying from 1 to ∼20 y. Moreover, we show that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (∼20 y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (∼2-5 y). Previous studies highlighted a rapid increase in discharge in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. Our results suggest that the rapid discharge increase in the NW Argentine Andes coincides with the periodic enhancement of discharge, which is mainly linked to a negative to positive transition of the PDO phase and TSA variability associated with a long-term increasing trend. We therefore suggest that variations in discharge in this region are largely driven by both natural variability and the effects of global climate change. We furthermore posit that the links between atmospheric and hydrologic processes result from a combination of forcings that operate on different spatiotemporal scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC41F..02C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC41F..02C">Continuing the Total and Spectral Solar Irradiance Climate Data Record</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Coddington, O.; Pilewskie, P.; Kopp, G.; Richard, E. C.; Sparn, T.; Woods, T. N. 2017-12-01 Radiative energy from the Sun establishes the basic climate of the Earth's surface and atmosphere and defines the terrestrial environment that supports all life on the planet. External solar variability on a wide range of scales ubiquitously affects the Earth system, and combines with internal forcings, including anthropogenic changes in greenhouse gases and aerosols, and natural modes such as ENSO, and volcanic forcing, to define past, present, and future climates. Understanding these effects requires continuous measurements of total and spectrally resolved solar irradiance that meet the stringent requirements of climate-quality accuracy and stability over time. The current uninterrupted 39-year total solar irradiance (TSI) climate data record is the result of several overlapping instruments flown on different missions. Measurement continuity, required to link successive instruments to the existing data record to discern long-term trends makes this important climate data record susceptible to loss in the event of a gap in measurements. While improvements in future instrument accuracy will reduce the risk of a gap, the 2017 launch of TSIS-1 ensures continuity of the solar irradiance record into the next decade. There are scientific and programmatic motivations for addressing the challenges of maintaining the solar irradiance data record beyond TSIS-1. The science rests on well-founded requirements of establishing a trusted climate observing network that can monitor trends in fundamental climate variables. Programmatically, the long-term monitoring of solar irradiance must be balanced within the broader goals of NASA Earth Science. New concepts for a low-risk, cost efficient observing strategy is a priority. New highly capable small spacecraft, low-cost launch vehicles and a multi-decadal plan to provide overlapping TSI and SSI data records are components of a low risk/high reliability plan with lower annual cost than past implementations. This paper provides the justification for prioritizing solar irradiance observations and plans for extending the record into the next two decades that adheres to the rigors of quantifiable methods for meeting objectives. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70046338','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70046338">The continuum of hydroclimate variability in western North America during the last millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ault, Toby R.; Cole, Julia E.; Overpeck, Jonathan T.; Pederson, Gregory T.; St. George, Scott; Otto-Bliesner, Bette; Woodhouse, Connie A.; Deser, Clara 2013-01-01 The distribution of climatic variance across the frequency spectrum has substantial importance for anticipating how climate will evolve in the future. Here we estimate power spectra and power laws (ß) from instrumental, proxy, and climate model data to characterize the hydroclimate continuum in western North America (WNA). We test the significance of our estimates of spectral densities and ß against the null hypothesis that they reflect solely the effects of local (non-climate) sources of autocorrelation at the monthly timescale. Although tree-ring based hydroclimate reconstructions are generally consistent with this null hypothesis, values of ß calculated from long-moisture sensitive chronologies (as opposed to reconstructions), and other types of hydroclimate proxies, exceed null expectations. We therefore argue that there is more low-frequency variability in hydroclimate than monthly autocorrelation alone can generate. Coupled model results archived as part of the Climate Model Intercomparison Project 5 (CMIP5) are consistent with the null hypothesis and appear unable to generate variance in hydroclimate commensurate with paleoclimate records. Consequently, at decadal to multidecadal timescales there is more variability in instrumental and proxy data than in the models, suggesting that the risk of prolonged droughts under climate change may be underestimated by CMIP5 simulations of the future. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OcMod.121..117B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OcMod.121..117B">Simulating the Agulhas system in global ocean models - nesting vs. multi-resolution unstructured meshes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Biastoch, Arne; Sein, Dmitry; Durgadoo, Jonathan V.; Wang, Qiang; Danilov, Sergey 2018-01-01 Many questions in ocean and climate modelling require the combined use of high resolution, global coverage and multi-decadal integration length. For this combination, even modern resources limit the use of traditional structured-mesh grids. Here we compare two approaches: A high-resolution grid nested into a global model at coarser resolution (NEMO with AGRIF) and an unstructured-mesh grid (FESOM) which allows to variably enhance resolution where desired. The Agulhas system around South Africa is used as a testcase, providing an energetic interplay of a strong western boundary current and mesoscale dynamics. Its open setting into the horizontal and global overturning circulations also requires global coverage. Both model configurations simulate a reasonable large-scale circulation. Distribution and temporal variability of the wind-driven circulation are quite comparable due to the same atmospheric forcing. However, the overturning circulation differs, owing each model's ability to represent formation and spreading of deep water masses. In terms of regional, high-resolution dynamics, all elements of the Agulhas system are well represented. Owing to the strong nonlinearity in the system, Agulhas Current transports of both configurations and in comparison with observations differ in strength and temporal variability. Similar decadal trends in Agulhas Current transport and Agulhas leakage are linked to the trends in wind forcing. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70035488','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70035488">Continuous salinity and temperature data from san francisco estuary, 19822002: Trends and the salinity-freshwater inflow relationship</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Shellenbarger, G.G.; Schoellhamer, D.H. 2011-01-01 The U.S. Geological Survey and other federal and state agencies have been collecting continuous temperature and salinity data, two critical estuarine habitat variables, throughout San Francisco estuary for over two decades. Although this dynamic, highly variable system has been well studied, many questions remain relating to the effects of freshwater inflow and other physical and biological linkages. This study examines up to 20 years of publically available, continuous temperature and salinity data from 10 different San Francisco Bay stations to identify trends in temperature and salinity and quantify the salinityfreshwater inflow relationship. Several trends in the salinity and temperature records were identified, although the high degree of daily and interannual variability confounds the analysis. In addition, freshwater inflow to the estuary has a range of effects on salinity from -0.0020 to -0.0096 (m3 s-1) -1 discharge, depending on location in the estuary and the timescale of analyzed data. Finally, we documented that changes in freshwater inflow to the estuary that are within the range of typical management actions can affect bay-wide salinities by 0.61.4. This study reinforces the idea that multidecadal records are needed to identify trends from decadal changes in water management and climate and, therefore, are extremely valuable. ?? 2011 Coastal Education & Research Foundation. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2809W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2809W">How does mesoscale impact deep convection? Answers from ensemble Northwestern Mediterranean Sea simulations.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Waldman, Robin; Herrmann, Marine; Somot, Samuel; Arsouze, Thomas; Benshila, Rachid; Bosse, Anthony; Chanut, Jérôme; Giordani, Hervé; Pennel, Romain; Sevault, Florence; Testor, Pierre 2017-04-01 Ocean deep convection is a major process of interaction between surface and deep ocean. The Gulf of Lions is a well-documented deep convection area in the Mediterranean Sea, and mesoscale dynamics is a known factor impacting this phenomenon. However, previous modelling studies don't allow to address the robustness of its impact with respect to the physical configuration and ocean intrinsic variability. In this study, the impact of mesoscale on ocean deep convection in the Gulf of Lions is investigated using a multi-resolution ensemble simulation of the northwestern Mediterranean sea. The eddy-permitting Mediterranean model NEMOMED12 (6km resolution) is compared to its eddy-resolving counterpart with the 2-way grid refinement AGRIF in the northwestern Mediterranean (2km resolution). We focus on the well-documented 2012-2013 period and on the multidecadal timescale (1979-2013). The impact of mesoscale on deep convection is addressed in terms of its mean and variability, its impact on deep water transformations and on associated dynamical structures. Results are interpreted by diagnosing regional mean and eddy circulation and using buoyancy budgets. We find a mean inhibition of deep convection by mesoscale with large interannual variability. It is associated with a large impact on mean and transient circulation and a large air-sea flux feedback. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ECSS..187...43T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ECSS..187...43T">Biodiversity of shallow subtidal, under-rock invertebrates in Europe's first marine reserve: Effects of physical factors and scientific sampling</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Trowbridge, Cynthia D.; Kachmarik, Katy; Plowman, Caitlin Q.; Little, Colin; Stirling, Penny; McAllen, Rob 2017-03-01 At Lough Hyne Marine Reserve in SW Ireland, shallow subtidal, under-rock biodiversity was investigated to assess (i) any deleterious effects of scientific sampling and (ii) quantitative baseline community patterns. Comparisons were made between 10 sites with annual rock-turning disturbance and 10 with multi-decadal (historical) disturbance. At each site, shallow subtidal rocks (N = 1289 total) were lifted, organisms recorded, and rocks replaced in their original position. Biodiversity indices were calculated to evaluate how diversity varied with location within the lough, frequency of sampling disturbance, degree of hypoxia/anoxia, dissolved oxygen (DO) concentration, and number of rocks turned. The richness of solitary invertebrates surveyed in situ averaged 21 taxa per site with significantly more in the South Basin (near the lough's connection to the ocean) than in the North Basin. The Shannon-Wiener Index did not differ significantly with variables investigated. However, evenness was higher at annually disturbed sites than at historical ones where anemones with algal symbionts often dominated. Several sites were hypoxic to anoxic under the shallow subtidal rocks. Cup corals were most abundant in the South Basin; DO was a crucial explanatory variable of these sensitive species. Solitary ascidians were most abundant at South-Basin annual sites with DO levels being a highly significant explanatory variable. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CliPD..11.4483R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CliPD..11.4483R">Atmospheric circulation patterns associated to the variability of River Ammer floods: evidence from observed and proxy data</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rimbu, N.; Czymzik, M.; Ionita, M.; Lohmann, G.; Brauer, A. 2015-09-01 The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammersee for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic time scales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over Western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency as recorded in the instrumental discharge record are associated to a wave-train pattern extending from the North Atlantic to western Asia with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated to increases in flood layer frequency in the Lake Ammersee sediment record during the pre-instrumental period. We argue that the complete flood layer time-series from Lake Ammersee sediments covering the last 5500 years, contains information about atmospheric circulation variability on inter-annual to millennial time-scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H43I1343J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H43I1343J">Stationarity and Inequality from the Mississippi to the Kissimmee: Climatic Control of Temporal Patterns in Catchment Discharge and Solute Export</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jawitz, J. W. 2011-12-01 What are the relative contributions of climatic variability, land management, and local geomorphology in determining the temporal dynamics of streamflow and the export of solutes from watersheds to receiving water bodies? A simple analytical framework is introduced for characterizing the temporal inequality of stream discharge and solute export from catchments using Lorenz diagrams and the associated Gini coefficient. These descriptors are used to illustrate a broad range of observed flow variability with a synthesis of multi-decadal flow data from 22 rivers in Florida. The analytical framework is extended to comprehensively link variability in flows and loads to climatically-driven inputs in terms of these inequality-based metrics. Further, based on a synthesis of data from the basins of the Baltic Sea, the Mississippi River, the Kissimmee River and other tributaries to Lake Okeechobee, FL, it is shown that inter-annual variations in exported loads for geogenic constituents, and for total N and total P, are dominantly controlled by discharge. Emergence of this consistent pattern across diverse managed catchments is attributed to the anthropogenic legacy of accumulated nutrient sources generating memory, similar to ubiquitously present sources for geogenic constituents. Multi-decadal phosphorus load data from 4 of the primary tributaries to Lake Okeechobee and sodium and nitrate load data from 9 of the Hubbard Brook, NH long-term study site catchments are used to examine the relation between inequality of climatic inputs, river flows and catchment loads. The intra-annual loads to Lake Okeechobee are shown to be highly unequal, such that 90% of annual load is delivered in as little as 15% of the time. Analytic expressions are developed for measures of inequality in terms of parameters of the lognormal distribution under general conditions that include intermittency. In cases where climatic variability is high compared to that of concentrations (chemostatic conditions), such as for P in the Lake Okeechobee basin and Na in Hubbard Brook, the temporal inequality of rainfall and flow are strong surrogates for load inequality. However, in cases where variability of concentrations is high compared to that of flows (chemodynamic conditions), such as for nitrate in the Hubbard Brook catchments, load inequality is greater than rainfall or flow inequality. The measured degree of correspondence between climatic, flow, and load inequality for these data sets are shown to be well described using the general inequality framework introduced here. Important implications are that (1) variations in hydro-climatic or anthropogenic forcing can be used to robustly predict inter-annual variations in flows and loads, (2) water quality problems in receiving inland and coastal waters may persist until the accumulated storages of nutrients have been substantially depleted, and (3) remedial measures designed to intercept or capture exported flows and loads must be designed with consideration of the intra-annual inequality. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMEP31D..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMEP31D..01G">Increasing Influence of Societal Response Variables in Coastal Evolution Projections (Invited)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gayes, P. T.; McCoy, C. A.; Pietrafesa, L. J. 2010-12-01 Recent efforts to project changes in coastal erosion and vulnerability of the state of South Carolina’s (SC’s) oceanfront for different scenarios of future sea level have reinforced the significance of the influence of societal modifications and response to past and anticipated coastal change in these systems. For large reaches of the SC coast human interactions have been a dominant signal driving coastal change across annual to decadal scales. Over the last 20 years, SC’s shoreline has been advanced seawards in many areas due to a combination of sustained societal commitment to beach nourishment and to a lull in atmospheric storms; reversing the long-term erosional trend of shoreline change. Adjacent areas not yet threatened or where coastal defense is unsupported economically have continued to migrate landwards. Locally, efforts focused on stabilizing the subaerial beach have not moderated long-term shoreward migration of the shoreface changing the overall morphology of the coastal boundary waves and currents are operating against. These societal effects, coupled with realistic, substative assessments of future atmospheric storm activity and sea level variability, both over scales of seasons to multi-decades, require consideration to realistically project future coastal behavior across time and spatial scales for planning and resource management. As with future climate and sea level variability effects on the shoreline, the scale and intensity of societal response is not static or precisely projected spatially and temporally into the future. With continued expansion of coastal development and erosion into previously lightly developed and defended coastal areas, societal influences should be expected to increase. Increasing cost of larger scale defenses will likely drive pressure for hardened structures to enhance ”softer” nourishment strategies. However, this strategy would further modify the ability of nature to respond to natural forces. Nourishment programs are strongly cyclic and can act in or out of phase with natural cyclic (inlet migration, sea level variability) or stochastic (storms) drivers with significant effects on coastal response and predictions of coastal behavior. Economic cycles and events may similarly moderate timing and scale of coastal defense relative to natural drivers. Societal decisions to not, enhance and or even abandon and remove existing engineering structures as future forces and costs increase, can result in a disproportional response and potentially failure of a section of coast. Some communities have expressed confidence in the ability to maintain the oceanfront shoreline against most projections of sea level rise over the next 100 years. The long-term trend in sea level change may be less important than naturally occurring regional scale, seasonal to inter-annual to multi-decadal variability in sea level; and these are complex but deterministic. There is less confidence, however, in the ability to combat passive submergence and associated flooding issues behind the immediate oceanfront. To the extent that may influence commitment to defend the oceanfront could strongly influence coastal behavior and stability in the long term. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70162171','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70162171">Lake oxygen isotopes as recorders of North American Rocky Mountain hydroclimate: Holocene patterns and variability at multi-decadal to millennial time scales</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Anderson, Lesleigh; Max Berkelhammer,; Barron, John A.; Steinman, Byron A.; Finney, Bruce P.; Abbott, Mark B. 2016-01-01 Lake sediment oxygen isotope records (calcium carbonate-δ18O) in the western North American Cordillera developed during the past decade provide substantial evidence of Pacific ocean–atmosphere forcing of hydroclimatic variability during the Holocene. Here we present an overview of 18 lake sediment δ18O records along with a new compilation of lake water δ18O and δ2H that are used to characterize lake sediment sensitivity to precipitation-δ18O in contrast to fractionation by evaporation. Of the 18 records, 14 have substantial sensitivity to evaporation. Two records reflect precipitation-δ18O since the middle Holocene, Jellybean and Bison Lakes, and are geographically positioned in the northern and southern regions of the study area. Their comparative analysis indicates a sequence of time-varying north–south precipitation-δ18O patterns that is evidence for a highly non-stationary influence by Pacific ocean–atmosphere processes on the hydroclimate of western North America. These observations are discussed within the context of previous research on North Pacific precipitation-δ18O based on empirical and modeling methods. The Jellybean and Bison Lake records indicate that a prominent precipitation-δ18O dipole (enriched-north and depleted-south) was sustained between ~ 3.5 and 1.5 ka, which contrasts with earlier Holocene patterns, and appears to indicate the onset of a dominant tropical control on North Pacific ocean–atmosphere dynamics. This remains the state of the system today. Higher frequency reversals of the north–south precipitation-δ18O dipole between ~ 2.5 and 1.5 ka, and during the Medieval Climate Anomaly and the Little Ice Age, also suggest more varieties of Pacific ocean–atmosphere modes than a single Pacific Decadal Oscillation (PDO) type analogue. Results indicate that further investigation of precipitation-δ18O patterns on short (observational) and long (Holocene) time scales is needed to improve our understanding of the processes that drive regional precipitation-δ18O responses to Pacific ocean–atmosphere variability, which in turn, will lead to a better understanding of internal Pacific ocean–atmosphere variability and its response to external climate forcing mechanisms. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP21B2021M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP21B2021M">Assessing modern climatic controls on southern Sierra Nevada precipitation and speleothem δ18O</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McCabe-Glynn, S. E.; Johnson, K. R.; Berkelhammer, M. B. 2012-12-01 Precipitation in the southwestern United States (SW US) is highly seasonal and exhibits inter-annual to inter-decadal variability. A 1154-year δ18O time series obtained from a southwestern Sierra Nevada Mountain stalagmite from Crystal Cave, CRC-3, (36.58°N; 118.56°W; 1540 m) reveals substantial decadal to multi-decadal variability closely linked to the Pacific Decadal Oscillation (PDO), and more specifically, to sea surface temperatures (SSTs) in the Kuroshio Extension region, which impact the atmospheric trajectory and isotopic composition of moisture reaching the study site. The instrumental portion of the CRC-3 δ18O time series suggests that more negative precipitation δ18O values are delivered from higher latitudes during positive phases of the PDO and/or when SSTs in the Kuroshio Extension region are anomalously cool, such as during La Niña events. In order to improve our understanding of the controls on speleothem δ18O in this region, we have conducted a detailed modern study of the climate, hydrology, and stable isotopic composition of meteoric waters (precipitation and drip water) at the cave. Here we present Crystal Cave drip logger results from 2010 to 2012, the isotopic composition of North American Deposition Program precipitation samples collected from 2001 to 2012 from several locations near our site including Ash Mountain (ASM), Sequoia National Park-Giant Forest (Ca75), and Yosemite National Park (Ca99), and isotopic composition of cave drip water and glass plate calcite. We also compare the δ18O values in the precipitation to satellite imagery, NCAR/NCEP data, and NOAA Hysplit Model backward trajectories between the sites. Results indicate that this site is particularly sensitive to "Pineapple Express" type storms, a persistent flow of atmospheric moisture and heavy rainfall extending from near the Hawaiian Islands to the coast of North America, which average about twice as much precipitation as other storms in the Sierra Nevada during winter. Crystal Cave drip logger results indicate a low drip rate variability in the cave between July 2010 and July 2011, averaging between ~25 drips/hour but we observe a significant increase during three "Pineapple Express" type storms (PE) during the 2010-2011 winter. Analysis of the δ18O of precipitation samples collected during these storms events exhibit significantly more negative values which could complicate the interpretation of speleothem δ18O if the relative contribution of PE moisture varies on interannual to multi-decadal timescales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010QSRv...29.3843K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010QSRv...29.3843K">North Atlantic influence on 19th-20th century rainfall in the Dead Sea watershed, teleconnections with the Sahel, and implication for Holocene climate fluctuations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kushnir, Yochanan; Stein, Mordechai 2010-12-01 The importance of understanding processes that govern the hydroclimate of the Mediterranean Basin is highlighted by the projected significant drying of the region in response to the increase in greenhouse gas concentrations. Here we study the long-term hydroclimatic variability of the central Levant region, situated in the eastern boundary of the Basin, as reveled by instrumental observations and the Holocene record of Dead Sea level variations. Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan Sahel and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with a broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea lake level, by lake levels in the Sahel, and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the Sahel and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an anti-phase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However the records are punctuated by abrupt lake-level drops, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We propose that the mechanisms by which NAtl SSTs affect precipitation in the central Levant is related to the tendency for high (low) pressure anomalies to persist over the eastern North Atlantic/Western Mediterranean region when the Basin is cold (warm). This, in turn, affects the likelihood of cold air outbreaks and cyclogenesis in the Eastern Mediterranean and, consequently, rainfall in the central Levant region. Depending on its phase, this natural mechanism can alleviate or exacerbate the anthropogenic impact on the regions' hydroclimatic future. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25142221','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25142221">The 2014 China meeting of the International Society for Vascular Surgery.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dardik, Alan; Ouriel, Kenneth; Wang, JinSong; Liapis, Christos 2014-10-01 The 2014 meeting of the International Society for Vascular Surgery (ISVS) was held in Guangzhou, China, in conjunction with the fifth annual Wang Zhong-Gao's Vascular Forum, the eighth annual China Southern Endovascular Congress, and the third annual Straits Vascular Forum. Keynote addresses were given by Professors Christos Liapis, Wang Zhong-Gao, and Wang Shen-Ming. President Liapis presented the first ISVS Lifetime Achievement Award to Professor Wang Zhong-Gao for his multi-decade accomplishments establishing Vascular Surgery as a specialty in China. Faculty presentations were made in plenary sessions that focused on diseases relevant to the patterns of vascular disease prevalent in China. Thirty-one abstracts were presented by vascular surgeons from around the globe, and the top 10 presentations were recognized. Thirteen countries were represented in the meeting. The 2014 ISVS meeting was a success. Partnership of this meeting with host Chinese Vascular Surgery societies was of mutual benefit, bringing vascular surgeons of international reputation to the local area for academic and intellectual exchange and formation of collaborations; integration of the meetings allows easier logistics to facilitate meeting organization and optimization of time for both faculty and attendees. This integrated model may serve as an optimal model for future meetings. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4944156','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4944156">Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Incarbona, Alessandro; Martrat, Belen; Mortyn, P. Graham; Sprovieri, Mario; Ziveri, Patrizia; Gogou, Alexandra; Jordà, Gabriel; Xoplaki, Elena; Luterbacher, Juerg; Langone, Leonardo; Marino, Gianluca; Rodríguez-Sanz, Laura; Triantaphyllou, Maria; Di Stefano, Enrico; Grimalt, Joan O.; Tranchida, Giorgio; Sprovieri, Rodolfo; Mazzola, Salvatore 2016-01-01 The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales. PMID:27412622 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H13I1516C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H13I1516C">SMERGE: A multi-decadal root-zone soil moisture product for CONUS</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Crow, W. T.; Dong, J.; Tobin, K. J.; Torres, R. 2017-12-01 Multi-decadal root-zone soil moisture products are of value for a range of water resource and climate applications. The NASA-funded root-zone soil moisture merging project (SMERGE) seeks to develop such products through the optimal merging of land surface model predictions with surface soil moisture retrievals acquired from multi-sensor remote sensing products. This presentation will describe the creation and validation of a daily, multi-decadal (1979-2015), vertically-integrated (both surface to 40 cm and surface to 100 cm), 0.125-degree root-zone product over the contiguous United States (CONUS). The modeling backbone of the system is based on hourly root-zone soil moisture simulations generated by the Noah model (v3.2) operating within the North American Land Data Assimilation System (NLDAS-2). Remotely-sensed surface soil moisture retrievals are taken from the multi-sensor European Space Agency Climate Change Initiative soil moisture data set (ESA CCI SM). In particular, the talk will detail: 1) the exponential smoothing approach used to convert surface ESA CCI SM retrievals into root-zone soil moisture estimates, 2) the averaging technique applied to merge (temporally-sporadic) remotely-sensed with (continuous) NLDAS-2 land surface model estimates of root-zone soil moisture into the unified SMERGE product, and 3) the validation of the SMERGE product using long-term, ground-based soil moisture datasets available within CONUS. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.1305S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.1305S">Three centuries of winter temperature change on the southeastern Tibetan Plateau and its relationship with the Atlantic Multidecadal Oscillation</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shi, Shiyuan; Li, Jinbao; Shi, Jiangfeng; Zhao, Yesi; Huang, Gang 2017-08-01 Long-term, high-resolution proxy records containing cold season temperature signals are scarce on the southeastern Tibetan Plateau (TP), limiting our understanding of regional climate and the potential driving forces. In this study, we present a nearly three centuries long reconstruction of winter (December-February) mean temperature for the central Hengduan Mountains, southeastern TP. The reconstruction is derived from a composite tree-ring width chronology of Pinus yunnanensis Franch from two high elevation sites (>3000 m above sea level). Our reconstruction passes all standard calibration-verification schemes and explains nearly 73 % of the variance of the original instrumental data. However, we were constrained to calibrate our full period (1718-2013) reconstruction of December-February mean temperature on the calibration period from 1959 to 1992 only, due to a decrease in temperature sensitivity of tree-ring index exhibited after 1992. Spatial correlation analysis shows that our reconstruction represents large-scale temperature variations in southwest China and the eastern TP. Our reconstructed December-February mean temperature shows a close association with the Atlantic Multidecadal Oscillation (AMO) over the past three centuries, with warm (cold) periods coinciding with the positive (negative) phases of the AMO. This persistent relationship suggests that the AMO may have been a key driver of multidecadal winter temperature variations on the southeastern TP. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53D2285R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53D2285R">A Skilful Marine Sclerochronological Network Based Reconstruction of North Atlantic Subpolar Gyre Dynamics</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Reynolds, D.; Hall, I. R.; Slater, S. M.; Scourse, J. D.; Wanamaker, A. D.; Halloran, P. R.; Garry, F. K. 2017-12-01 Spatial network analyses of precisely dated, and annually resolved, tree-ring proxy records have facilitated robust reconstructions of past atmospheric climate variability and the associated mechanisms and forcings that drive it. In contrast, a lack of similarly dated marine archives has constrained the use of such techniques in the marine realm, despite the potential for developing a more robust understanding of the role basin scale ocean dynamics play in the global climate system. Here we show that a spatial network of marine molluscan sclerochronological oxygen isotope (δ18Oshell) series spanning the North Atlantic region provides a skilful reconstruction of basin scale North Atlantic sea surface temperatures (SSTs). Our analyses demonstrate that the composite marine series (referred to as δ18Oproxy_PC1) is significantly sensitive to inter-annual variability in North Atlantic SSTs (R=-0.61 P<0.01) and surface air temperatures (SATs; R=-0.67, P<0.01) over the 20th century. Subpolar gyre (SPG) SSTs dominates variability in the δ18Oproxy_PC1 series at sub-centennial frequencies (R=-0.51, P<0.01). Comparison of the δ18Oproxy_PC1 series against variability in the strength of the European Slope Current and maximum North Atlantic meridional overturning circulation derived from numeric climate models (CMIP5), indicates that variability in the SPG region, associated with the strength of the surface currents of the North Atlantic, are playing a significant role in shaping the multi-decadal scale SST variability over the industrial era. These analyses demonstrate that spatial networks developed from sclerochronological archives can provide powerful baseline archives of past ocean variability that can facilitate the development of a quantitative understanding for the role the oceans play in the global climate systems and constraining uncertainties in numeric climate models. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70155262','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70155262">The forcing of southwestern Asia teleconnections by low-frequency sea surface temperature variability during boreal winter</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Hoell, Andrew; Funk, Christopher C.; Mathew Barlow, 2015-01-01 Southwestern Asia, defined here as the domain bounded by 20°–40°N and 40°–70°E, which includes the nations of Iraq, Iran, Afghanistan, and Pakistan, is a water-stressed and semiarid region that receives roughly 75% of its annual rainfall during November–April. The November–April climate of southwestern Asia is strongly influenced by tropical Indo-Pacific variability on intraseasonal and interannual time scales, much of which can be attributed to sea surface temperature (SST) variations. The influences of lower-frequency SST variability on southwestern Asia climate during November–April Pacific decadal SST (PDSST) variability and the long-term trend in SST (LTSST) is examined. The U.S. Climate Variability and Predictability Program (CLIVAR) Drought Working Group forced global atmospheric climate models with PDSST and LTSST patterns, identified using empirical orthogonal functions, to show the steady atmospheric response to these modes of decadal to multidecadal SST variability. During November–April, LTSST forces an anticyclone over southwestern Asia, which results in reduced precipitation and increases in surface temperature. The precipitation and tropospheric circulation influences of LTSST are corroborated by independent observed precipitation and circulation datasets during 1901–2004. The decadal variations of southwestern Asia precipitation may be forced by PDSST variability, with two of the three models indicating that the cold phase of PDSST forces an anticyclone and precipitation reductions. However, there are intermodel circulation variations to PDSST that influence subregional precipitation patterns over the Middle East, southwestern Asia, and subtropical Asia. Changes in wintertime temperature and precipitation over southwestern Asia forced by LTSST and PDSST imply important changes to the land surface hydrology during the spring and summer. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CliPa..13.1831S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CliPa..13.1831S">Hydroclimate variability in Scandinavia over the last millennium - insights from a climate model-proxy data comparison</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Seftigen, Kristina; Goosse, Hugues; Klein, Francois; Chen, Deliang 2017-12-01 The integration of climate proxy information with general circulation model (GCM) results offers considerable potential for deriving greater understanding of the mechanisms underlying climate variability, as well as unique opportunities for out-of-sample evaluations of model performance. In this study, we combine insights from a new tree-ring hydroclimate reconstruction from Scandinavia with projections from a suite of forced transient simulations of the last millennium and historical intervals from the CMIP5 and PMIP3 archives. Model simulations and proxy reconstruction data are found to broadly agree on the modes of atmospheric variability that produce droughts-pluvials in the region. Despite these dynamical similarities, large differences between simulated and reconstructed hydroclimate time series remain. We find that the GCM-simulated multi-decadal and/or longer hydroclimate variability is systematically smaller than the proxy-based estimates, whereas the dominance of GCM-simulated high-frequency components of variability is not reflected in the proxy record. Furthermore, the paleoclimate evidence indicates in-phase coherencies between regional hydroclimate and temperature on decadal timescales, i.e., sustained wet periods have often been concurrent with warm periods and vice versa. The CMIP5-PMIP3 archive suggests, however, out-of-phase coherencies between the two variables in the last millennium. The lack of adequate understanding of mechanisms linking temperature and moisture supply on longer timescales has serious implications for attribution and prediction of regional hydroclimate changes. Our findings stress the need for further paleoclimate data-model intercomparison efforts to expand our understanding of the dynamics of hydroclimate variability and change, to enhance our ability to evaluate climate models, and to provide a more comprehensive view of future drought and pluvial risks. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CorRe..36.1225T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CorRe..36.1225T">Multi-decadal analysis reveals contrasting patterns of resilience and decline in coral assemblages</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tanner, Jason E. 2017-12-01 A 50-yr study of coral dynamics at Heron Island, on Australia's Great Barrier Reef, shows that community change on a single reef is highly variable and that while some areas of the reef are in decline, others are recovering well 40 yr after a major cyclonic disturbance that eliminated all corals in the study plot. At one site, the genus-level composition in 2012 was identical to that before the cyclone, although it took around 30 yr to recover, and there were still differences at the species level. The colony size structure of some species at this site, notably the dominant Acropora digitifera, which had over 40% cover in 2012, also recovered after 30 yr, although sub-dominant species still lacked large colonies even after 40 yr. Given the small scale of the individual study plots (1 m2), this shows an unexpected degree of determinism in assemblage structure. At a second site, however, both composition and size structure changed dramatically over the last 40 yr of the study as both external and internal factors altered local environmental conditions. At both sites, major changes in composition appear to be related to drying out of the reef crest due to changes in flow regimes and/or natural accretion. At the site that has recovered, erosion has reversed this drying out, whereas no such erosion has occurred at the second site. If such erosion occurs, or sea levels increase due to global warming, then the second site may also prove to be resilient over decadal time scales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSAH53A..04R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSAH53A..04R">Multidecadal Increase in North Atlantic Coccolithophores and Potential Role of Increasing CO2</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rivero-Calle, S.; Gnanadesikan, A.; del Castillo, C. E.; Balch, W. M.; Guikema, S. 2016-02-01 As anthropogenic CO2 emissions acidify the oceans, calcifiers are expected to be negatively impacted. Using data from the Continuous Plankton Recorder, we show that coccolithophore occurrence in the North Atlantic has increased from 2 to over 20% from 1965 through 2010. We used Random Forest models to examine more than 20 possible environmental drivers of this change. CO2 and the Atlantic Multidecadal Oscillation were the best predictors. Since coccolithophore photosynthesis is strongly carbon-limited, we hypothesize that higher CO2 levels might be encouraging growth. A compilation of 41 independent laboratory studies supports our hypothesis. Our study shows a long-term basin-scale increase in coccolithophores and suggests that increasing pCO2 and temperature accelerated the growth rate of a key phytoplankton group for carbon cycling. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413219L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413219L">Do GCM's predict the climate.... Or the low frequency weather?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lovejoy, S.; Schertzer, D.; Varon, D. 2012-04-01 Over twenty-five years ago, a three-regime scaling model was proposed describing the statistical variability of the atmosphere over time scales ranging from weather scales out to ≈ 100 kyrs. Using modern in situ data reanalyses, monthly surface series (at 5ox5o), 8 "multiproxy" (yearly) series of the Northern hemisphere from 1500 - 1980, and GRIP and Vostok paleotemperatures at 5.2 and ≈ 100 year resolutions (over the past 91-420 kyrs), we refine the model and show how it can be understood with the help of new developments in nonlinear dynamics, especially multifractals and cascades. In a scaling range, mean fluctuations in state variables such as temperature ΔT vary in power law manners ≈ Δt**H the where Δt is the duration. At small (weather) scales the fluctuation exponents are generally H>0; they grow with scale (Δt). At longer scales Δt >τw (≈ 10 days) H changes sign, the fluctuations decrease with scale; this is the low variability, "low frequency weather" regime. In this regime, the spectrum is a relatively flat "plateau", it's variability is low, stable, corresponding to our usual idea of "long term weather statistics". Finally for longer times, Δt>τc ≈ 10 - 100 years, once again H>0, so that the variability increases with scale: the true climate regime. These scaling regimes allow us to objectively define the weather as fluctuations over periods <τw, to define "climate states" as fluctuations at scale τc and then "climate change" as the fluctuations at longer periods (Δt>τc). We show that the intermediate low frequency weather regime is the result of the weather regime undergoing a "dimensional transition": at temporal scales longer than the typical lifetime of planetary structures (τw), the spatial degrees of freedom are rapidly quenched so that only the temporal degrees of freedom are important. This low frequency weather regime has statistical properties well reproduced not only by stochastic cascade models of weather, but also by control runs (i.e. without climate forcing) of GCM based climate forecasting systems including those of the Institut Pierre Simon Laplace (Paris) and the Earth Forecasting System (Hamburg). In order for these systems to go beyond simply predicting low frequency weather i.e. in order for them to predict the climate, they need appropriate climate forcings and/ or new internal mechanisms of variability. Using statistical scaling techniques we examine the scale dependence of fluctuations from forced and unforced GCM outputs, including from the ECHO-G and EFS simulations in the Millenium climate reconstruction project and compare this with data, multiproxies and paleo data. Our general conclusion is that the models systematically underestimate the multidecadal, multicentennial scale variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26168910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26168910">Persistent drying in the tropics linked to natural forcing.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Winter, Amos; Zanchettin, Davide; Miller, Thomas; Kushnir, Yochanan; Black, David; Lohmann, Gerrit; Burnett, Allison; Haug, Gerald H; Estrella-Martínez, Juan; Breitenbach, Sebastian F M; Beaufort, Luc; Rubino, Angelo; Cheng, Hai 2015-07-14 Approximately half of the world's population lives in the tropics, and future changes in the hydrological cycle will impact not just the freshwater supplies but also energy production in areas dependent upon hydroelectric power. It is vital that we understand the mechanisms/processes that affect tropical precipitation and the eventual surface hydrological response to better assess projected future regional precipitation trends and variability. Paleo-climate proxies are well suited for this purpose as they provide long time series that pre-date and complement the present, often short instrumental observations. Here we present paleo-precipitation data from a speleothem located in Mesoamerica that reveal large multi-decadal declines in regional precipitation, whose onset coincides with clusters of large volcanic eruptions during the nineteenth and twentieth centuries. This reconstruction provides new independent evidence of long-lasting volcanic effects on climate and elucidates key aspects of the causal chain of physical processes determining the tropical climate response to global radiative forcing. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2827G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2827G">Santa Ana Winds of Southern California: Their climatology, extremes, and behavior spanning six and a half decades</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Guzman-Morales, Janin; Gershunov, Alexander; Theiss, Jurgen; Li, Haiqin; Cayan, Daniel 2016-03-01 Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region, but their climate-scale behavior is poorly understood. In the present work, we identify SAWs in mesoscale dynamical downscaling of a global reanalysis from 1948 to 2012. Model winds are validated with anemometer observations. SAWs exhibit an organized pattern with strongest easterly winds on westward facing downwind slopes and muted magnitudes at sea and over desert lowlands. We construct hourly local and regional SAW indices and analyze elements of their behavior on daily, annual, and multidecadal timescales. SAWs occurrences peak in winter, but some of the strongest winds have occurred in fall. Finally, we observe that SAW intensity is influenced by prominent large-scale low-frequency modes of climate variability rooted in the tropical and north Pacific ocean-atmosphere system. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29712890','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29712890">Increasing occurrence of cold and warm extremes during the recent global warming slowdown.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Johnson, Nathaniel C; Xie, Shang-Ping; Kosaka, Yu; Li, Xichen 2018-04-30 The recent levelling of global mean temperatures after the late 1990s, the so-called global warming hiatus or slowdown, ignited a surge of scientific interest into natural global mean surface temperature variability, observed temperature biases, and climate communication, but many questions remain about how these findings relate to variations in more societally relevant temperature extremes. Here we show that both summertime warm and wintertime cold extreme occurrences increased over land during the so-called hiatus period, and that these increases occurred for distinct reasons. The increase in cold extremes is associated with an atmospheric circulation pattern resembling the warm Arctic-cold continents pattern, whereas the increase in warm extremes is tied to a pattern of sea surface temperatures resembling the Atlantic Multidecadal Oscillation. These findings indicate that large-scale factors responsible for the most societally relevant temperature variations over continents are distinct from those of global mean surface temperature. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.4245M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.4245M">Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A. 2015-06-01 Previous studies have suggested that ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE) can be used to measure the depth-averaged, or barotropic, transport variability of the Antarctic Circumpolar Current (ACC). Here, we use GRACE OBP observations to calculate transport variability in a region of the southern Indian Ocean encompassing the major fronts of the ACC. We use a statistical analysis of a simulated GRACE-like data set to determine the uncertainty of the estimated transport for the 2003.0-2013.0 time period. We find that when the transport is averaged over 60° of longitude, the uncertainty (one standard error) is close to 1 Sv (1 Sv = 106 m3 s-1) for low-pass filtered transport, which is significantly smaller than the signal and lower than previous studies have found. The interannual variability is correlated with the Southern Annual mode (SAM) (0.61), but more highly correlated with circumpolar zonally averaged winds between 45°S and 65°S (0.88). GRACE transport reflects significant changes in transport between 2007 and 2009 that is observed in the zonal wind variations but not in the SAM index. We also find a statistically significant trend in transport (-1.0 ± 0.4 Sv yr-1, 90% confidence) that is correlated with a local deceleration in zonal winds related to an asymmetry in the SAM on multidecadal periods. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011CliPD...7..347R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011CliPD...7..347R">Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rodgers, K. B.; Fletcher, S. E. M.; Bianchi, D.; Beaulieu, C.; Galbraith, E. D.; Gnanadesikan, A.; Hogg, A. G.; Iudicone, D.; Lintner, B.; Naegler, T.; Reimer, P. J.; Sarmiento, J. L.; Slater, R. D. 2011-01-01 Tree ring Δ14C data (Reimer et al., 2004; McCormac et al., 2004) indicate that atmospheric Δ14C varied on multi-decadal to centennial timescales, in both hemispheres, over the pre-industrial period AD 950-1830. Although the Northern and Southern Hemispheric Δ14C records display similar variability, it is difficult from these data alone to distinguish between variations driven by 14CO2 production in the upper atmosphere (Stuiver, 1980) and exchanges between carbon reservoirs (Siegenthaler, 1980). Here we consider rather the Interhemispheric Gradient in atmospheric Δ14C as revealing of the background pre-bomb air-sea Disequilbrium Flux between 14CO2 and CO2. As the global maximum of the Disequilibrium Flux is squarely centered in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the Interhemispheric Gradient. The analysis presented here implies that changes to Southern Ocean windspeeds are likely a main driver of the observed variability in the Interhemispheric Gradient over 950-1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980-2004). This interpretation also implies a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds remain unkown. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70189930','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70189930">Predicting regime shifts in flow of the Colorado River</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Gangopadhyay, Subhrendu; McCabe, Gregory J. 2010-01-01 The effects of continued global warming on water resources are a concern for water managers and stake holders. In the western United States, where the combined climatic demand and consumptive use of water is equal to or greater than the natural supply of water for some locations, there is growing concern regarding the sustainability of future water supplies. In addition to the adverse effects of warming on water supply, another issue for water managers is accounting for, and managing, the effects of natural climatic variability, particularly persistently dry and wet periods. Analyses of paleo-reconstructions of Upper Colorado River basin (UCRB) flow demonstrate that severe sustained droughts, and persistent pluvial periods, are a recurring characteristic of hydroclimate in the Colorado River basin. Shifts between persistently dry and wet regimes (e.g., decadal to multi-decadal variability (D2M)) have important implications for water supply and water management. In this study paleo-reconstructions of UCRB flow are used to compute the risks of shifts between persistently wet and dry regimes given the length of time in a specific regime. Results indicate that low frequency variability of hydro-climatic conditions and the statistics that describe this low frequency variability can be useful to water managers by providing information about the risk of shifting from one hydrologic regime to another. To manage water resources in the future water managers will have to understand the joint hydrologic effects of natural climate variability and global warming. These joint effects may produce future hydrologic conditions that are unprecedented in both the instrumental and paleoclimatic records. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H14E..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H14E..01C">Spatiotemporal drought variability in the Mediterranean over the last 900 years</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cook, B.; Anchukaitis, K. J.; Touchan, R.; Meko, D. M.; Cook, E. R. 2016-12-01 Recent Mediterranean droughts have highlighted concerns that climate change may be contributing to observed drying trends, but natural climate variability in the region is still poorly understood. We analyze 900 years (1100-2012) of Mediterranean drought variability in the Old World Drought Atlas (OWDA), a spatiotemporal tree ring reconstruction of the June-July-August self-calibrating Palmer Drought Severity Index. In the Mediterranean, the OWDA is highly correlated with spring precipitation (April-June), the North Atlantic Oscillation (January-April), the Scandinavian Pattern (January-March), and the East Atlantic Pattern (April-June). Drought variability displays significant east-west coherence across the basin on multidecadal to centennial timescales and north-south antiphasing in the eastern Mediterranean, with a tendency for wet anomalies in the Black Sea region (e.g., Greece, Anatolia, and the Balkans) when coastal Libya, the southern Levant, and the Middle East are dry, possibly related to the North Atlantic Oscillation. Recent droughts are centered in the western Mediterranean, Greece, and the Levant. Events of similar magnitude in the western Mediterranean and Greece occur in the OWDA, but the recent 15 year drought in the Levant (1998-2012) is the driest in the record. Estimating uncertainties using a resampling approach, we conclude that there is an 89% likelihood that this drought is drier than any comparable period of the last 900 years and a 98% likelihood that it is drier than the last 500 years. These results confirm the exceptional nature of this drought relative to natural variability in recent centuries, consistent with studies that have found evidence for anthropogenically forced drying in the region. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ClDy...39.1021P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ClDy...39.1021P">Decadal-timescale changes of the Atlantic overturning circulation and climate in a coupled climate model with a hybrid-coordinate ocean component</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Persechino, A.; Marsh, R.; Sinha, B.; Megann, A. P.; Blaker, A. T.; New, A. L. 2012-08-01 A wide range of statistical tools is used to investigate the decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) and associated key variables in a climate model (CHIME, Coupled Hadley-Isopycnic Model Experiment), which features a novel ocean component. CHIME is as similar as possible to the 3rd Hadley Centre Coupled Model (HadCM3) with the important exception that its ocean component is based on a hybrid vertical coordinate. Power spectral analysis reveals enhanced AMOC variability for periods in the range 15-30 years. Strong AMOC conditions are associated with: (1) a Sea Surface Temperature (SST) anomaly pattern reminiscent of the Atlantic Multi-decadal Oscillation (AMO) response, but associated with variations in a northern tropical-subtropical gradient; (2) a Surface Air Temperature anomaly pattern closely linked to SST; (3) a positive North Atlantic Oscillation (NAO)-like pattern; (4) a northward shift of the Intertropical Convergence Zone. The primary mode of AMOC variability is associated with decadal changes in the Labrador Sea and the Greenland Iceland Norwegian (GIN) Seas, in both cases linked to the tropical activity about 15 years earlier. These decadal changes are controlled by the low-frequency NAO that may be associated with a rapid atmospheric teleconnection from the tropics to the extratropics. Poleward advection of salinity anomalies in the mixed layer also leads to AMOC changes that are linked to processes in the Labrador Sea. A secondary mode of AMOC variability is associated with interannual changes in the Labrador and GIN Seas, through the impact of the NAO on local surface density. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29780676','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29780676">Spatiotemporal drought variability in the Mediterranean over the last 900 years.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cook, Benjamin I; Anchukaitis, Kevin J; Touchan, Ramzi; Meko, David M; Cook, Edward R 2016-03-16 Recent Mediterranean droughts have highlighted concerns that climate change may be contributing to observed drying trends, but natural climate variability in the region is still poorly understood. We analyze 900 years (1100-2012) of Mediterranean drought variability in the Old World Drought Atlas (OWDA), a spatiotemporal tree-ring reconstruction of the June-July-August self calibrating Palmer Drought Severity Index. In the Mediterranean, the OWDA is highly correlated with spring precipitation (April-June), the North Atlantic Oscillation (January-April), the Scandinavian Pattern (January-March), and the East Atlantic Pattern (April-June). Drought variability displays significant east-west coherence across the basin on multi-decadal to centennial time scales and north-south anti-phasing in the eastern Mediterranean, with a tendency for wet anomalies in the Black Sea region (e.g., Greece, Anatolia, the Balkans, etc) when coastal Libya, the southern Levant, and the Middle East are dry, possibly related to the North Atlantic Oscillation. Recent droughts are centered in the Western Mediterranean, Greece, and the Levant. Events of similar magnitude in the Western Mediterranean and Greece occur in the OWDA, but the recent 15-year drought in the Levant (1998-2012) is the driest in the record. Estimating uncertainties using a resampling approach, we conclude there is an 89% likelihood this drought is drier than any comparable period of the last 900 years and a 98% likelihood it is drier than the last 500 years. These results confirm the exceptional nature of this drought relative to natural variability in recent centuries, consistent with studies that have found evidence for anthropogenically forced drying in the region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013713','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013713">Comparative Analysis of Upper Ocean Heat Content Variability from Ensemble Operational Ocean Analyses</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Xue, Yan; Balmaseda, Magdalena A.; Boyer, Tim; Ferry, Nicolas; Good, Simon; Ishikawa, Ichiro; Rienecker, Michele; Rosati, Tony; Yin, Yonghong; Kumar, Arun 2012-01-01 Upper ocean heat content (HC) is one of the key indicators of climate variability on many time-scales extending from seasonal to interannual to long-term climate trends. For example, HC in the tropical Pacific provides information on thermocline anomalies that is critical for the longlead forecast skill of ENSO. Since HC variability is also associated with SST variability, a better understanding and monitoring of HC variability can help us understand and forecast SST variability associated with ENSO and other modes such as Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), Tropical Atlantic Variability (TAV) and Atlantic Multidecadal Oscillation (AMO). An accurate ocean initialization of HC anomalies in coupled climate models could also contribute to skill in decadal climate prediction. Errors, and/or uncertainties, in the estimation of HC variability can be affected by many factors including uncertainties in surface forcings, ocean model biases, and deficiencies in data assimilation schemes. Changes in observing systems can also leave an imprint on the estimated variability. The availability of multiple operational ocean analyses (ORA) that are routinely produced by operational and research centers around the world provides an opportunity to assess uncertainties in HC analyses, to help identify gaps in observing systems as they impact the quality of ORAs and therefore climate model forecasts. A comparison of ORAs also gives an opportunity to identify deficiencies in data assimilation schemes, and can be used as a basis for development of real-time multi-model ensemble HC monitoring products. The OceanObs09 Conference called for an intercomparison of ORAs and use of ORAs for global ocean monitoring. As a follow up, we intercompared HC variations from ten ORAs -- two objective analyses based on in-situ data only and eight model analyses based on ocean data assimilation systems. The mean, annual cycle, interannual variability and longterm trend of HC have been analyzed </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24080617','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24080617">Extreme rainfall, vulnerability and risk: a continental-scale assessment for South America.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Vörösmarty, Charles J; Bravo de Guenni, Lelys; Wollheim, Wilfred M; Pellerin, Brian; Bjerklie, David; Cardoso, Manoel; D'Almeida, Cassiano; Green, Pamela; Colon, Lilybeth 2013-11-13 Extreme weather continues to preoccupy society as a formidable public safety concern bearing huge economic costs. While attention has focused on global climate change and how it could intensify key elements of the water cycle such as precipitation and river discharge, it is the conjunction of geophysical and socioeconomic forces that shapes human sensitivity and risks to weather extremes. We demonstrate here the use of high-resolution geophysical and population datasets together with documentary reports of rainfall-induced damage across South America over a multi-decadal, retrospective time domain (1960-2000). We define and map extreme precipitation hazard, exposure, affectedpopulations, vulnerability and risk, and use these variables to analyse the impact of floods as a water security issue. Geospatial experiments uncover major sources of risk from natural climate variability and population growth, with change in climate extremes bearing a minor role. While rural populations display greatest relative sensitivity to extreme rainfall, urban settings show the highest rates of increasing risk. In the coming decades, rapid urbanization will make South American cities the focal point of future climate threats but also an opportunity for reducing vulnerability, protecting lives and sustaining economic development through both traditional and ecosystem-based disaster risk management systems. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5020648','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5020648">Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic Meridional Overturning Circulation</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ionita, M.; Scholz, P.; Lohmann, G.; Dima, M.; Prange, M. 2016-01-01 As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962–1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models. PMID:27619955 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27619955','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27619955">Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic Meridional Overturning Circulation.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ionita, M; Scholz, P; Lohmann, G; Dima, M; Prange, M 2016-09-13 As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962-1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P23D..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P23D..07D">Two Decades (almost) of Keck Observations of Io</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> De Pater, I.; Davies, A. G.; de Kleer, K. 2015-12-01 We have regularly observed Io with the 10-m Keck Telescope since 1998, initially using the speckle imaging technique, and switching to Adaptive Optics techniques when this became available in 2001. In this talk we will discuss several eruptions that we witnessed, and present 20-30 year timelines of thermal emission from Pele, Pillan, Janus Patera, Kanehekili Fluctus, and Loki Patera, updating timelines in recent publications [1, 2] with additional Keck adaptive optics data obtained between 2002 and 2015. These new timelines are the most comprehensive plots ever produced of the volcanic thermal emission variability for these or any other locations on Io, utilizing data from multiple ground- and space-based assets. Our continuing multi-decadal observing program forms the basis for charting the variability of Io's volcanic activity, of great importance for understanding the evolution of the Galilean satellite system, and with the expectation of new missions to the jovian system in the next decade. Acknowledgements: This research is in part supported by NSF grant AST-1313485 to UC Berkeley. AGD is supported by a grant from the NASA OPR Program. References: [1] Davies et al. (2012) Icarus, 221, 466-470. [2] Rathbun and Spencer (2010) Icarus, 209, 625-630. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028605','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028605">Precipitation history and ecosystem response to multidecadal precipitation variability in the Mojave Desert region, 1893-2001</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Hereford, R.; Webb, R.H.; Longpre, C.I. 2006-01-01 Precipitation varied substantially in the Mojave Desert through the 20th century in a manner broadly similar to the other warm North American deserts. Episodes of drought and prolonged dry conditions (1893-1904, ca. 1942-1975, and 1999-present) alternated with relatively wet periods (1905-ca. 1941 and ca. 1976-1998), probably because of global-scale climate fluctuations. These are the El Nin??o-Southern Oscillation that affects interannual climate and the Pacific Decadal Oscillation that evidently causes decadal-scale variability such as prolonged dry and wet episodes. Studies done in the late 20th century demonstrate that precipitation fluctuations affected populations of perennial vegetation, annuals, and small herbivores. Landscape rephotography reveals that several species, particularly creosote bush, increased in size and density during the ca. 1976-1998 wet period. A brief, intense drought from 1989 to 1991 and the ongoing drought caused widespread mortality of certain species; for example, chenopods and perennial grasses suffered up to 100% mortality. Drought pruning, the shedding of above-ground biomass to reduce carbon allocation, increased substantially during drought. Overall, drought had the greatest influence on the Mojave Desert ecosystem. ?? 2006. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120015958','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120015958">Identifying and Evaluating the Relationships that Control a Land Surface Model's Hydrological Behavior</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Koster, Randal D.; Mahanama, Sarith P. 2012-01-01 The inherent soil moisture-evaporation relationships used in today 's land surface models (LSMs) arguably reflect a lot of guesswork given the lack of contemporaneous evaporation and soil moisture observations at the spatial scales represented by regional and global models. The inherent soil moisture-runoff relationships used in the LSMs are also of uncertain accuracy. Evaluating these relationships is difficult but crucial given that they have a major impact on how the land component contributes to hydrological and meteorological variability within the climate system. The relationships, it turns out, can be examined efficiently and effectively with a simple water balance model framework. The simple water balance model, driven with multi-decadal observations covering the conterminous United States, shows how different prescribed relationships lead to different manifestations of hydrological variability, some of which can be compared directly to observations. Through the testing of a wide suite of relationships, the simple model provides estimates for the underlying relationships that operate in nature and that should be operating in LSMs. We examine the relationships currently used in a number of different LSMs in the context of the simple water balance model results and make recommendations for potential first-order improvements to these LSMs. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP41D..08H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP41D..08H">Tropical Pacific forcing on decadal-to-centennial NAO-dominated precipitation variability in northern Mediterranean over the past 6500 years</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hu, H. M.; Shen, C. C.; Michel, V.; Jiang, X.; Mii, H. S.; Wang, Y.; Valensi, P. 2017-12-01 We present a multi-annual-resolved absolute-dated stalagmite-inferred precipitation record, with age precision as good as ±2 years, from northern Italy, to reflect North Atlantic Oscillation (NAO) dynamics since 6.5 ka (thousand years ago, before 1950 C.E.). Our record features millennial precipitation fluctuations punctuated by several centennial-scale drought periods centered at 5.6, 6.2, 4.2, 3.0 and 2.3 ka. The phase relationship with previous NAO-sensitive records suggests a multi-millennial southward migration of the northern Westerlies and enhanced NAO variability from the middle- to late-Holocene. We also found the multi-decadal to centennial rainfall amount could dramatically vary within few decades, possibly affecting ancient Mediterranean civilizations. Concurrence between northern Mediterranean precipitation and western tropical Pacific sea surface temperature records suggests the remote forcing on this NAO-dominated rainfall. We argue that the irregular NAO change nowadays could be related to high frequency of El Niño-Southern Oscillation events and might cause an inevitable abrupt hydroclimate change and irreparable impacts on the regional human society in the near future. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PrOce..83...65M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PrOce..83...65M">The Humboldt Current System: Ecosystem components and processes, fisheries, and sediment studies</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Montecino, Vivian; Lange, Carina B. 2009-12-01 In the Humboldt Current System (HCS), biological and non-biological components, ecosystem processes, and fisheries are known to be affected by multi-decadal, inter-annual, annual, and intra-seasonal scales. The interplay between atmospheric variability, the poleward undercurrent, the shallow oxygen minimum zone (OMZ), and the fertilizing effect of coastal upwelling and overall high primary production rates drive bio-physical interactions, the carbon biomass, and fluxes of gases and particulate and dissolved matter through the water column. Coastal upwelling (permanent and seasonally modulated off Peru and northern Chile, and markedly seasonal between 30°S and 40°S) is the key process responsible for the high biological productivity in the HCS. At present, the western coast of South America produces more fish per unit area than any other region in the world ocean (i.e. ∼7.5 × 10 6 t of anchoveta were landed in 2007). Climate changes on different temporal scales lead to alterations in the distribution ranges of anchoveta and sardine populations and shifts in their dominance throughout the HCS. The factors affecting the coastal marine ecosystem that reverberate in the fisheries are crucial from a social perspective, since the economic consequences of mismanagement can be severe. Fish remains are often well-preserved in sediment settings under the hypoxic conditions of the OMZ off Peru and Chile, and reveal multi-decadal variability and centennial-scale changes in fish populations. Sediment studies from the Chilean continental margin encompassing the last 20,000 years of deposition reveal changes in sub-surface conditions in the HCS during deglaciation, interpreted to include: a major reorganization of the OMZ; a deglacial increase in denitrification decoupled from local marine productivity; and higher deglacial and Holocene paleoproductivities compared to the Last Glacial Maximum in central-south Chile (35-37°S) while this scheme is reversed for north-central Chile. Multi-scale, interdisciplinary approaches and focused research groups are needed to understand air-sea interactions, plankton dynamics, biomass removal by fisheries, and the transformation and fluxes of matter across the different HCS components. In this paper, we present a multidisciplinary synthesis of the HCS that covers its physics, atmosphere, primary and secondary production, medium and high trophic levels, fisheries including management aspects, and relevant sedimentary studies. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMS...133...55H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMS...133...55H">Multidecadal Atlantic climate variability and its impact on marine pelagic communities</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Harris, Victoria; Edwards, Martin; Olhede, Sofia C. 2014-05-01 A large scale analysis of sea surface temperature (SST) and climate variability over the North Atlantic and its interactions with plankton over the North East Atlantic was carried out to better understand what drives both temperature and species abundance. The spatio-temporal pattern of SST was found to correspond to known climate indices, namely the Atlantic Multidecadal Oscillation (AMO), the East Atlantic Pattern (EAP) and the North Atlantic Oscillation (NAO). The spatial influence of these indices is heterogeneous. Although the AMO is present across all regions, it is most strongly represented in the SST signal in the subpolar gyre region. The NAO instead is strongly weighted in the North Sea and the pattern of its influence is oscillatory in space with a wavelength of approximately 6000 km. Natural oscillations might obscure the influence of climate change effects, making it difficult to determine how much of the variation is attributable to longer term trends. In order to separate the influences of different climate signals the SST signals were decomposed in to spatial and temporal components using principal component analysis (PCA). A similar analysis is carried out on various indicator species of plankton: Calanus finmarchicus, Phytoplankton Colour Index and total copepod abundance, as well as phytoplankton and zooplankton communities. By comparing the two outputs it is apparent that the dominant driver is the recent warming trend, which has a negative influence on C. finmarchicus and total copepods, but has a positive one on phytoplankton colour. However natural oscillations also influence the abundance of plankton, in particular the AMO is a driver of diatom abundance. Fourier principal component analysis, an approach which is novel in terms of the ecological data, was used to analyse the behaviour of various communities averaged over space. The zooplankton community is found to be primarily influenced by climate warming trends. The analysis provides compelling evidence for the hypothesis that cold water species are gradually being replaced by more temperate species in the North Atlantic. This may have detrimental effects for the entire marine ecosystem, by affecting on organisms such as fish larva for example. The second group, a phytoplankton subset consisting primarily of diatom species, is primarily influenced by the AMO rather than the average temperature trend. This result highlights the importance of natural oscillations to certain functional groups, in particular those subgroups which are less directly metabolically affected by changes in temperature. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70025498','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70025498">Taking the pulse of mountains: Ecosystem responses to climatic variability</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Fagre, Daniel B.; Peterson, David L.; Hessl, Amy E. 2003-01-01 An integrated program of ecosystem modeling and field studies in the mountains of the Pacific Northwest (U.S.A.) has quantified many of the ecological processes affected by climatic variability. Paleoecological and contemporary ecological data in forest ecosystems provided model parameterization and validation at broad spatial and temporal scales for tree growth, tree regeneration and treeline movement. For subalpine tree species, winter precipitation has a strong negative correlation with growth; this relationship is stronger at higher elevations and west-side sites (which have more precipitation). Temperature affects tree growth at some locations with respect to length of growing season (spring) and severity of drought at drier sites (summer). Furthermore, variable but predictable climate-growth relationships across elevation gradients suggest that tree species respond differently to climate at different locations, making a uniform response of these species to future climatic change unlikely. Multi-decadal variability in climate also affects ecosystem processes. Mountain hemlock growth at high-elevation sites is negatively correlated with winter snow depth and positively correlated with the winter Pacific Decadal Oscillation (PDO) index. At low elevations, the reverse is true. Glacier mass balance and fire severity are also linked to PDO. Rapid establishment of trees in subalpine ecosystems during this century is increasing forest cover and reducing meadow cover at many subalpine locations in the western U.S.A. and precipitation (snow depth) is a critical variable regulating conifer expansion. Lastly, modeling potential future ecosystem conditions suggests that increased climatic variability will result in increasing forest fire size and frequency, and reduced net primary productivity in drier, east-side forest ecosystems. As additional empirical data and modeling output become available, we will improve our ability to predict the effects of climatic change across a broad range of climates and mountain ecosystems in the northwestern U.S.A. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP41E..05D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP41E..05D">Relationship between annual precipitation variability and ENSO in Southern California for the Common Era (last 2,000 years)</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> DU, X.; Hendy, I. L.; Hinnov, L.; Brown, E. T.; Schimmelmann, A.; Pak, D. K. 2017-12-01 The El Niño-Southern Oscillation (ENSO) has a major influence on Southern California's hydroclimate as demonstrated by both historical observations and model simulations. Santa Barbara Basin (SBB) off Southern California preserves a unique varved (i.e. annually laminated) marine sedimentary archive of modern and Holocene hydroclimate variability, notably including the transition from the regionally dry Medieval Climate Anomaly (MCA) to the wetter Little Ice Age (LIA). Here we present sub-annually resolved scanning XRF elemental counts for the last 2,000 years in SBB from core SPR0901-03KC. Titanium (associated with silicate minerals) is delivered more efficiently to SBB sediments during times of enhanced river flow and in the Mediterranean climate of Southern California, river flow only occurs after precipitation. The Ti record suggests that the precipitation frequency was reduced during the MCA except for a pluvial episode at CE 1075-1121, but increased during the LIA. Time series analysis of Ti counts indicates ENSO variability robustly increased during the intervals CE 450-520, 650-720, 980-1150, 1380-1550 and 1720-1750, and experienced relatively quiescent intervals between CE 50-150, 250-400, 550-650, 750-950, 1150-1280 and 1580-1620. Generally the LIA in Southern California is characterized by more active ENSO variability with long periodicities (4-7 yr) and multi-decadal variability (54 yr). MCA drought episodes were associated with less active ENSO. Active ENSO variability in Southern California during the last 2,000 years coincided with reconstructed southward migration of the Intertropical Convergence Zone (ITCZ) suggesting the ITCZ may play a role in the waxing and waning of ENSO teleconnections between the central Pacific and the west coast of North America. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H42G..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H42G..02S">Examining the last few decades of global hydroclimate for evidence of anthropogenic change amidst natural variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Seager, R.; Naik, N.; Ting, M.; Kushnir, Y.; Kelley, C. P. 2011-12-01 Climate models robustly predict that the deep tropics and mid-latitude-to-subpolar regions will moisten, and the subtropical dry zones both dry and expand, as a consequence of global warming driven by rising greenhouse gases. The models also predict that this transition to a more extreme climatological mean global hydroclimate should already be underway. Given the importance of these predictions it is an imperative that the climate science community assess whether there is evidence within the observational record that they are correct. This task is made difficult by the tremendous natural variability of the hydrological cycle on seasonal to multidecadal timescales. Here we will use instrumental observations, reanalyses, sea surface temperature forced atmosphere models and coupled model simulations, and a variety of methodologies, to attempt to separate global radiatively-forced hydroclimate change from ongoing natural variability. The results will be applied to explain trends and recent events in key regions such as Mexico, the United States and the Mediterranean. It is concluded that the signal of anthropogenic change is small compared to the amplitude of natural variability but that it is a discernible contributor. Globally the evidence reveals that radiatively-forced hydroclimate change is occurring with an amplitude and spatial pattern largely consistent with the predictions by IPCC AR4 models of hydroclimate change to date. However it will also be shown that the radiatively-forced component does not in and of itself provide a useful prediction of near term hydroclimate change because for many regions the amplitude of natural decadal variability is as large or larger. Useful predictions need to account for how natural variability may evolve as well as forced change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Sci...350.1533R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Sci...350.1533R">Multidecadal increase in North Atlantic coccolithophores and the potential role of rising CO2</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rivero-Calle, Sara; Gnanadesikan, Anand; Del Castillo, Carlos E.; Balch, William M.; Guikema, Seth D. 2015-12-01 As anthropogenic carbon dioxide (CO2) emissions acidify the oceans, calcifiers generally are expected to be negatively affected. However, using data from the Continuous Plankton Recorder, we show that coccolithophore occurrence in the North Atlantic increased from ~2 to more than 20% from 1965 through 2010. We used random forest models to examine more than 20 possible environmental drivers of this change, finding that CO2 and the Atlantic Multidecadal Oscillation were the best predictors, leading us to hypothesize that higher CO2 levels might be encouraging growth. A compilation of 41 independent laboratory studies supports our hypothesis. Our study shows a long-term basin-scale increase in coccolithophores and suggests that increasing CO2 and temperature have accelerated the growth of a phytoplankton group that is important for carbon cycling. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1260166-distinct-effects-anthropogenic-aerosols-east-asian-summer-monsoon-between-multidecadal-strong-weak-monsoon-stages','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1260166-distinct-effects-anthropogenic-aerosols-east-asian-summer-monsoon-between-multidecadal-strong-weak-monsoon-stages">Distinct effects of anthropogenic aerosols on the East Asian summer monsoon between multidecadal strong and weak monsoon stages</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/pages">DOE PAGES</a> Xie, Xiaoning; Wang, Hongli; Liu, Xiaodong; ... 2016-06-18 Industrial emissions of anthropogenic aerosols over East Asia have greatly increased in recent decades, and so the interactions between atmospheric aerosols and the East Asian summer monsoon (EASM) have attracted enormous attention. In order to further understand the aerosol-EASM interaction, we investigate the impacts of anthropogenic aerosols on the EASM during the multidecadal strong (1950–1977) and weak (1978–2000) EASM stages using the Community Atmospheric Model 5.1. Numerical experiments are conducted for the whole period, including the two different EASM stages, with present day (PD, year 2000) and preindustrial (PI, year 1850) aerosol emissions, as well as the observed time-varying aerosolmore » emissions. A comparison of the results from PD and PI shows that, with the increase in anthropogenic aerosols, the large-scale EASM intensity is weakened to a greater degree (-9.8%) during the weak EASM stage compared with the strong EASM stage (-4.4%). The increased anthropogenic aerosols also result in a significant reduction in precipitation over North China during the weak EASM stage, as opposed to a statistically insignificant change during the strong EASM stage. Because of greater aerosol loading and the larger sensitivity of the climate system during weak EASM stages, the aerosol effects are more significant during these EASM stages. Moreover, these results suggest that anthropogenic aerosols from the same aerosol emissions have distinct effects on the EASM and the associated precipitation between the multidecadal weak and strong EASM stages.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC21I..04F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC21I..04F">The dominant role of Arctic surface buoyancy fluxes for AMOC slow-down on multi-decadal timescales</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fedorov, A. V.; Sevellec, F. 2016-12-01 One of the most dramatic consequences of the ongoing climate change is the reduction in the Arctic sea ice cover observed over the past few decades. This sea ice loss increases net heat flux into the ocean and at the same time exposes the ocean to additional freshwater flux from the atmosphere. These two effects imply positive anomalies in surface buoyancy fluxes over the Arctic ocean. In this study we estimate the sensitivity of the Atlantic Meridional Overturning Circulation (AMOC) to global changes in surface buoyancy forcing, especially in the context of changes in the Arctic. We find that, whereas on decadal timescale the subpolar region (especially east and south of Greenland) is the primarily driver of AMOC weakening due to positive buoyancy fluxes, on multidecadal timescales (longer than 20 years) it is the Arctic region that largely controls the AMOC slow-down. On timescales close to one century surface buoyancy fluxes over the Arctic ocean are nearly twice as effective for weakening the AMOC than those in the subpolar North Atlantic. We also find that the anomalous surface buoyancy fluxes in the Arctic can efficiently weaken poleward heat transport in the North Atlantic on a basin scale (i.e., between 25oN and 50oN). We conclude that such remote control of the AMOC intensity and heat transport by the Arctic ocean is a robust feature of climate change on multi-decadal timescales. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SpWea..15.1215K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SpWea..15.1215K">Ms. Hisako Koyama: From Amateur Astronomer to Long-Term Solar Observer</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Knipp, Delores; Liu, Huixin; Hayakawa, Hisashi 2017-10-01 The path to science for a girl of any nationality born in the early twentieth century was formidable-to-nonexistent. Yet paths were forged by a few. We present the little-known story of one of Japan's premier solar observers and her contribution to the world's understanding of sunspots and space weather cycles. Ms. Hisako Koyama, born in Tokyo in 1916, became a passionate amateur astronomer, a dedicated solar observer, and a long-serving staff member of the National Museum of Nature and Science, Tokyo. As a writer for amateur astronomy journals she advised many on the details and joys of sky viewing. She created a consistent, extended record of sunspots. Her multidecade archive of sunspot drawings is one of the "backbones" for the recent international recalibration of the sunspot record that provides insight into space weather reaching back to the early 1600s. We detail her contributions to the citizens of Japan as an ambassador of astronomy and her international contribution to understanding the symmetries and asymmetries of the solar cycle. We comment on the value of her continuous record of sunspots and on her tenacity in promoting a science that links to space weather. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AdSpR..40.1126T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AdSpR..40.1126T">The role of the global electric circuit in solar and internal forcing of clouds and climate</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tinsley, Brian A.; Burns, G. B.; Zhou, Limin Reports of a variety of short-term meteorological responses to changes in the global electric circuit associated with a set of disparate inputs are analyzed. The meteorological responses consist of changes in cloud cover, atmospheric temperature, pressure, or dynamics. All of these are found to be responding to changes in a key linking agent, that of the downward current density, Jz, that flows from the ionosphere through the troposphere to the surface (ocean and land). As it flows through layer clouds, Jz generates space charge in conductivity gradients at the upper and lower boundaries, and this electrical charge is capable of affecting the microphysical interactions between droplets and both ice-forming nuclei and condensation nuclei. Four short-term inputs to the global circuit are due to solar activity and consist of (1) Forbush decreases of the galactic cosmic ray flux; (2) solar energetic particle events; (3) relativistic electron precipitation changes; and (4) polar cap ionospheric convection potential changes. One input that is internal to the global circuit consists of (5) global ionospheric potential changes due to changes in the current output of the highly electrified clouds (mainly deep convective clouds at low latitudes) that act as generators for the circuit. The observed short-term meteorological responses to these five inputs are of small amplitude but high statistical significance for repeated Jz changes of order 5% for low latitudes increasing to 25-30% at high latitudes. On the timescales of multidecadal solar minima, such as the Maunder minimum, changes in tropospheric dynamics and climate related to Jz are also larger at high latitudes, and correlate with the lower energy component (˜1 GeV) of the cosmic ray flux increasing by as much as a factor of two relative to present values. Also, there are comparable cosmic ray flux changes and climate responses on millennial timescales. The persistence of the longer-term Jz changes for many decades to many centuries would produce an integrated effect on climate that could dominate over short-term weather and climate variations, and explain the observed correlations. Thus, we propose that mechanisms responding to Jz are a candidate for explanations of sun-weather-climate correlations on multidecadal to millenial timescales, as well as on the day-to-day timescales analyzed here. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PApGe.tmp...30G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PApGe.tmp...30G">Long-Term Trends, Variability and Extremes of In Situ Sea Surface Temperature Measured Along the Eastern Adriatic Coast and its Relationship to Hemispheric Processes</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Grbec, Branka; Matić, Frano; Beg Paklar, Gordana; Morović, Mira; Popović, Ružica; Vilibić, Ivica 2018-02-01 This paper examines long-term series of in situ sea surface temperature (SST) data measured at nine coastal and one open sea stations along the eastern Adriatic Sea for the period 1959-2015. Monthly and yearly averages were used to document SST trends and variability, while clustering and connections to hemispheric indices were achieved by applying the Principal Component Analysis (PCA) and Self-Organizing Maps (SOM) method. Both PCA and SOM revealed the dominance of temporal changes with respect to the effects of spatial differences in SST anomalies, indicating the prevalence of hemispheric processes over local dynamics, such as bora wind spatial inhomogeneity. SST extremes were connected with blocking atmospheric patterns. A substantial warming between 1979 and 2015, in total exceeding 1 °C, was preceded by a period with a negative SST trend, implying strong multidecadal variability in the Adriatic. The strongest connection was found between yearly SST and the East Atlantic (EA) pattern, while North Atlantic Oscillation (NAO) and East Atlantic/West Russia (EAWR) patterns were found to also affect February SST values. Quantification of the Adriatic SST and their connection to hemispheric indices allow for more precise projections of future SST, considered to be rather important for Adriatic thermohaline circulation, biogeochemistry and fisheries, and sensitive to ongoing climate change. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70030129','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70030129">1400 yr multiproxy record of climate variability from the northern Gulf of Mexico</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Richey, J.N.; Poore, R.Z.; Flower, B.P.; Quinn, T.M. 2007-01-01 A continuous decadal-scale resolution record of climate variability over the past 1400 yr in the northern Gulf of Mexico was constructed from a box core recovered in the Pigmy Basin, northern Gulf of Mexico. Proxies include paired analyses of Mg/Ca and δ18O in the white variety of the planktic foraminifer Globigerinoides ruber and relative abundance variations of G. sacculifer in the foraminifer assemblages. Two multi-decadal intervals of sustained high Mg/Ca indicate that Gulf of Mexico sea surface temperatures (SSTs) were as warm or warmer than near-modern conditions between 1000 and 1400 yr B.P. Foraminiferal Mg/Ca during the coolest interval of the Little Ice Age (ca. 250 yr B.P.) indicate that SST was 2–2.5 °C below modern SST. Four minima in the Mg/Ca record between 900 and 250 yr B.P. correspond with the Maunder, Spörer, Wolf, and Oort sunspot minima, suggesting a link between changes in solar insolation and SST variability in the Gulf of Mexico. An abrupt shift recorded in both δ18Ocalcite and relative abundance of G. sacculifer occurred ca. 600 yr B.P. The shift in the Pigmy Basin record corresponds with a shift in the sea-salt-sodium (ssNa) record from the Greenland Ice Sheet Project 2 ice core, linking changes in high-latitude atmospheric circulation with the subtropical Atlantic Ocean. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PNAS..114.6227T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PNAS..114.6227T">Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tokinaga, Hiroki; Xie, Shang-Ping; Mukougawa, Hitoshi 2017-06-01 With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean-atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C13D..08T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C13D..08T">Grounding Zones, Subglacial Lakes, and Dynamics of an Antarctic Ice Stream: The WISSARD Glaciological Experiment</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tulaczyk, S. M.; Schwartz, S. Y.; Fisher, A. T.; Powell, R. D.; Fricker, H. A.; Anandakrishnan, S.; Horgan, H. J.; Scherer, R. P.; Walter, J. I.; Siegfried, M. R.; Mikucki, J.; Christianson, K.; Beem, L.; Mankoff, K. D.; Carter, S. P.; Hodson, T. O.; Marsh, O.; Barcheck, C. G.; Branecky, C.; Neuhaus, S.; Jacobel, R. W. 2015-12-01 Interactions of West Antarctic ice streams with meltwater at their beds, and with seawater at their grounding lines, are widely considered to be the primary drivers of ice stream flow variability on different timescales. Understanding of processes controlling ice flow variability is needed to build quantitative models of the Antarctic Ice Sheet that can be used to help predict its future behavior and to reconstruct its past evolution. The ice plain of Whillans Ice Stream provides a natural glaciological laboratory for investigations of Antarctic ice flow dynamics because of its highly variable flow rate modulated by tidal processes and fill-drain cycles of subglacial lakes. Moreover, this part of Antarctica has one of the longest time series of glaciological observations, which can be used to put recently acquired datasets in a multi-decadal context. Since 2007 Whillans Ice Stream has been the focus of a regional glaciological experiment, which included surface GPS and passive-source seismic sensors, radar and seismic imaging of subglacial properties, as well as deep borehole geophysical sensors. This experiment was possible thanks to the NSF-funded multidisciplinary WISSARD project (Whillans Ice Stream Subglacial Access Research Drilling). Here we will review the datasets collected during the WISSARD glaciological experiment and report on selected results pertaining to interactions of this ice stream with water at its bed and its grounding line. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5172530','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5172530">Putting Temperature and Oxygen Thresholds of Marine Animals in Context of Environmental Change: A Regional Perspective for the Scotian Shelf and Gulf of St. Lawrence</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> 2016-01-01 We conducted a literature review of reported temperature, salinity, pH, depth and oxygen preferences and thresholds of important marine species found in the Gulf of St. Lawrence and Scotian Shelf region. We classified 54 identified fishes and macroinvertebrates as important either because they support a commercial fishery, have threatened or at risk status, or meet one of the following criteria: bycatch, baitfish, invasive, vagrant, important for ecosystem energy transfer, or predators or prey of the above species. The compiled data allow an assessment of species-level impacts including physiological stress and mortality given predictions of future ocean physical and biogeochemical conditions. If an observed, multi-decadal oxygen trend on the central Scotian Shelf continues, a number of species will lose favorable oxygen conditions, experience oxygen-stress, or disappear due to insufficient oxygen in the coming half-century. Projected regional trends and natural variability are both large, and natural variability will act to alternately amplify and dampen anthropogenic changes. When estimates of variability are included with the trend, species encounter unfavourable oxygen conditions decades sooner. Finally, temperature and oxygen thresholds of adult Atlantic wolffish (Anarhichas lupus) and adult Atlantic cod (Gadus morhua) are assessed in the context of a potential future scenario derived from high-resolution ocean models for the central Scotian Shelf. PMID:27997536 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27997536','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27997536">Putting Temperature and Oxygen Thresholds of Marine Animals in Context of Environmental Change: A Regional Perspective for the Scotian Shelf and Gulf of St. Lawrence.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Brennan, Catherine E; Blanchard, Hannah; Fennel, Katja 2016-01-01 We conducted a literature review of reported temperature, salinity, pH, depth and oxygen preferences and thresholds of important marine species found in the Gulf of St. Lawrence and Scotian Shelf region. We classified 54 identified fishes and macroinvertebrates as important either because they support a commercial fishery, have threatened or at risk status, or meet one of the following criteria: bycatch, baitfish, invasive, vagrant, important for ecosystem energy transfer, or predators or prey of the above species. The compiled data allow an assessment of species-level impacts including physiological stress and mortality given predictions of future ocean physical and biogeochemical conditions. If an observed, multi-decadal oxygen trend on the central Scotian Shelf continues, a number of species will lose favorable oxygen conditions, experience oxygen-stress, or disappear due to insufficient oxygen in the coming half-century. Projected regional trends and natural variability are both large, and natural variability will act to alternately amplify and dampen anthropogenic changes. When estimates of variability are included with the trend, species encounter unfavourable oxygen conditions decades sooner. Finally, temperature and oxygen thresholds of adult Atlantic wolffish (Anarhichas lupus) and adult Atlantic cod (Gadus morhua) are assessed in the context of a potential future scenario derived from high-resolution ocean models for the central Scotian Shelf. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29780675','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29780675">The paleoclimate context and future trajectory of extreme summer hydroclimate in eastern Australia.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cook, Benjamin I; Palmer, Jonathan G; Cook, Edward R; Turney, Chris S M; Allen, Kathryn; Fenwick, Pavla; O'Donnell, Alison; Lough, Janice M; Grierson, Pauline F; Ho, Michelle; Baker, Patrick J 2016-11-16 Eastern Australia recently experienced an intense drought (Millennium Drought, 2003-2009) and record-breaking rainfall and flooding (austral summer 2010-2011). There is some limited evidence for a climate change contribution to these events, but such analyses are hampered by the paucity of information on long-term natural variability. Analyzing a new reconstruction of summer (December-January-February) Palmer Drought Severity Index (the Australia-New Zealand Drought Atlas; ANZDA, 1500-2012 CE), we find moisture deficits during the Millennium Drought fall within the range of the last 500 years of natural hydroclimate variability. This variability includes periods of multi-decadal drought in the 1500s more persistent than any event in the historical record. However, the severity of the Millennium Drought, which was caused by autumn (March-April-May) precipitation declines, may be underestimated in the ANZDA because the reconstruction is biased towards summer and antecedent spring (September-October-November) precipitation. The pluvial in 2011, however, which was characterized by extreme summer rainfall faithfully captured by the ANZDA, is likely the wettest year in the reconstruction for Coastal Queensland. Climate projections (RCP 8.5 scenario) suggest that eastern Australia will experience long-term drying during the 21 st century. While the contribution of anthropogenic forcing to recent extremes remains an open question, these projections indicate an amplified risk of multi-year drought anomalies matching or exceeding the intensity of the Millennium Drought. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910131C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910131C">River-discharge variability and trends in southeastern Central Andes since 1940</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred R. 2017-04-01 The southern Central Andes in NW Argentina comprise small to medium drainage basins (102-104 km2) particularly sensitive to climate variability. In this area and in contrast to larger drainage basins such as the Amazon or La Plata rivers, floodplains or groundwater reservoirs either do not exist or are small. This reduces their dampening effect on discharge variability. Previous studies highlighted a rapid discharge increase up to 40% in seven years in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. To better understand the processes that drive variations in river discharge in this region, we analyze discharge variability on different timescales, relying on four time series of monthly discharge between 1940 and 2015. Since river discharge in this complex mountain environment results in a pronounced non-stationary and non-linear character, we apply the Hilbert-Huang Transform (HHT) to evaluate non-stationary oscillatory modes of variability and trends. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be decomposed in four quasi-periodic, statistically significant oscillatory modes, associated with timescales varying from 1 to ˜20y. In addition, statistically significant long-term trends show increasing discharge during the period between 1940 and 2015, documenting an intensification of the hydrological cycle during this period. Furthermore, time-dependent intrinsic correlation (TDIC) analysis shows that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (˜20y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (˜2-5y). Finally, our results suggest that the rapid discharge increased occurred during the 1970s coincides with the periodic enhancement of discharge mainly linked to the rise of the PDO oscillation from the negative to the positive phase in superposition with the long-term increasing trend, further modulated by TSA variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110005518&hterms=theory+develop&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dtheory%2Bdevelop','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110005518&hterms=theory+develop&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dtheory%2Bdevelop">Generating Vegetation Leaf Area Index Earth System Data Record from Multiple Sensors. Part 1; Theory</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ganguly, Sangram; Schull, Mitchell A.; Samanta, Arindam; Shabanov, Nikolay V.; Milesi, Cristina; Nemani, Ramakrishna R.; Knyazikhin, Yuri; Myneni, Ranga B. 2008-01-01 The generation of multi-decade long Earth System Data Records (ESDRs) of Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) from remote sensing measurements of multiple sensors is key to monitoring long-term changes in vegetation due to natural and anthropogenic influences. Challenges in developing such ESDRs include problems in remote sensing science (modeling of variability in global vegetation, scaling, atmospheric correction) and sensor hardware (differences in spatial resolution, spectral bands, calibration, and information content). In this paper, we develop a physically based approach for deriving LAI and FPAR products from the Advanced Very High Resolution Radiometer (AVHRR) data that are of comparable quality to the Moderate resolution Imaging Spectroradiometer (MODIS) LAI and FPAR products, thus realizing the objective of producing a long (multi-decadal) time series of these products. The approach is based on the radiative transfer theory of canopy spectral invariants which facilitates parameterization of the canopy spectral bidirectional reflectance factor (BRF). The methodology permits decoupling of the structural and radiometric components and obeys the energy conservation law. The approach is applicable to any optical sensor, however, it requires selection of sensor-specific values of configurable parameters, namely, the single scattering albedo and data uncertainty. According to the theory of spectral invariants, the single scattering albedo is a function of the spatial scale, and thus, accounts for the variation in BRF with sensor spatial resolution. Likewise, the single scattering albedo accounts for the variation in spectral BRF with sensor bandwidths. The second adjustable parameter is data uncertainty, which accounts for varying information content of the remote sensing measurements, i.e., Normalized Difference Vegetation Index (NDVI, low information content), vs. spectral BRF (higher information content). Implementation of this approach indicates good consistency in LAI values retrieved from NDVI (AVHRRmode) and spectral BRF (MODIS-mode). Specific details of the implementation and evaluation of the derived products are detailed in the second part of this two-paper series. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A33M..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A33M..03R">Global Ocean Evaporation Increases Since 1960 in Climate Reanalyses: How Accurate Are They?</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Robertson, F. R.; Roberts, J. B.; Bosilovich, M. G. 2016-12-01 Evaporation from the world's oceans constitutes the largest component of the global water balance. It is important not only as the ultimate source of moisture that is tied to the radiative processes determining Earth's energy balance but also to freshwater availability over land, governing habitability of the planet. The question we address is whether by using conventional observations alone, the problematic stepwise changes to model bias correction imposed by the continually changing satellite data record can be avoided and a more accurate estimate of evaporation changes obtained over the past six decades—including the satellite era from 1979 to the present. Three climate reanalyses are used, the NOAA ESRL 20CR V2, the ECMWF ERA-20C, and the JRA-55C. In contrast to conventional reanalyses, reduced-observational reanalyses are run with fewer constraints with more temporally homogenous records- SSTs, sea-ice, and radiative forcing (i.e. AMIPs) and additional, minimal observations of surface pressure and marine observations. An ensemble of AMIP-style experiments provides an important comparison. Though limited in temporal extent, state-of-the-art satellite retrievals from the SeaFlux project and 10m neutral winds from Remote Sensing Systems analysis of passive microwave measurements represent observationally driven estimates of evaporation and near-surface wind speed. ENSO-related changes in evaporation dominate interannual timescales, though over multi-decadal periods we find increasing evaporation trends approaching the Clausius-Clapeyron rate of 6% per degree SST rise. This contrasts with the more muted changes in AMIP experiments. Near-surface relative humidity and stability changes generally act to counterbalance the effects of SST alone, but wind speed changes are a chief driver of the evaporation changes. Multi-decadal signals related to Pacific and Atlantic climate variability are prominent; however, there are notable signatures of wind data issues—particularly over the Southern Indian Ocean. Though the passive microwave record extends only from 1988, associated wind speed measurements confirm the basic structure of wind-driven evaporation trends in recent decades. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28199416','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28199416">Restoring and managing low-severity fire in dry-forest landscapes of the western USA.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Baker, William L 2017-01-01 Low-severity fires that killed few canopy trees played a significant historical role in dry forests of the western USA and warrant restoration and management, but historical rates of burning remain uncertain. Past reconstructions focused on on dating fire years, not measuring historical rates of burning. Past statistics, including mean composite fire interval (mean CFI) and individual-tree fire interval (mean ITFI) have biases and inaccuracies if used as estimators of rates. In this study, I used regression, with a calibration dataset of 96 cases, to test whether these statistics could accurately predict two equivalent historical rates, population mean fire interval (PMFI) and fire rotation (FR). The best model, using Weibull mean ITFI, had low prediction error and R2adj = 0.972. I used this model to predict historical PMFI/FR at 252 sites spanning dry forests. Historical PMFI/FR for a pool of 342 calibration and predicted sites had a mean of 39 years and median of 30 years. Short (< 25 years) mean PMFI/FRs were in Arizona and New Mexico and scattered in other states. Long (> 55 years) mean PMFI/FRs were mainly from northern New Mexico to South Dakota. Mountain sites often had a large range in PMFI/FR. Nearly all 342 estimates are for old forests with a history of primarily low-severity fire, found across only about 34% of historical dry-forest area. Frequent fire (PMFI/FR < 25 years) was found across only about 14% of historical dry-forest area, with 86% having multidecadal rates of low-severity fire. Historical fuels (e.g., understory shrubs and small trees) could fully recover between multidecadal fires, allowing some denser forests and some ecosystem processes and wildlife habitat to be less limited by fire. Lower historical rates mean less restoration treatment is needed before beginning managed fire for resource benefits, where feasible. Mimicking patterns of variability in historical low-severity fire regimes would likely benefit biological diversity and ecosystem functioning. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6314D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6314D">Development of a harmonised multi sensor retrieval scheme for HCHO within the Quality Assurance For Essential Climate Variables (QA4ECV) project</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> De Smedt, Isabelle; Richter, Andreas; Beirle, Steffen; Danckaert, Thomas; Van Roozendael, Michel; Yu, Huan; Bösch, Tim; Hilboll, Andreas; Peters, Enno; Doerner, Steffen; Wagner, Thomas; Wang, Yang; Lorente, Alba; Eskes, Henk; Van Geffen, Jos; Boersma, Folkert 2016-04-01 One of the main goals of the QA4ECV project is to define community best-practices for the generation of multi-decadal ECV data records from satellite instruments. QA4ECV will develop retrieval algorithms for the Land ECVs surface albedo, leaf area index (LAI), and fraction of active photosynthetic radiation (fAPAR), as well as for the Atmosphere ECV ozone and aerosol precursors nitrogen dioxide (NO2), formaldehyde (HCHO), and carbon monoxide (CO). Here we assess best practices and provide recommendations for the retrieval of HCHO. Best practices are established based on (1) a detailed intercomparison exercise between the QA4ECV partner's for each specific algorithm processing steps, (2) the feasibility of implementation, and (3) the requirement to generate consistent multi-sensor multi-decadal data records. We propose a fitting window covering the 328.5-346 nm spectral interval for the morning sensors (GOME, SCIAMACHY and GOME-2) and an extension to 328.5-359 nm for OMI and GOME-2, allowed by improved quality of the recorded spectra. A high level of consistency between group algorithms is found when the retrieval settings are carefully aligned. However, the retrieval of slant columns is highly sensitive to any change in the selected settings. The use of a mean background radiance as DOAS reference spectrum allows for a stabilization of the retrievals. A background correction based on the reference sector method is recommended for implementation in the QA4ECV HCHO algorithm as it further reduces retrieval uncertainties. HCHO AMFs using different radiative transfer codes show a good overall consistency when harmonized settings are used. As for NO2, it is proposed to use a priori HCHO profiles from the TM5 model. These are provided on a 1°x1° latitude-longitude grid. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5310858','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5310858">Restoring and managing low-severity fire in dry-forest landscapes of the western USA</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> 2017-01-01 Low-severity fires that killed few canopy trees played a significant historical role in dry forests of the western USA and warrant restoration and management, but historical rates of burning remain uncertain. Past reconstructions focused on on dating fire years, not measuring historical rates of burning. Past statistics, including mean composite fire interval (mean CFI) and individual-tree fire interval (mean ITFI) have biases and inaccuracies if used as estimators of rates. In this study, I used regression, with a calibration dataset of 96 cases, to test whether these statistics could accurately predict two equivalent historical rates, population mean fire interval (PMFI) and fire rotation (FR). The best model, using Weibull mean ITFI, had low prediction error and R2adj = 0.972. I used this model to predict historical PMFI/FR at 252 sites spanning dry forests. Historical PMFI/FR for a pool of 342 calibration and predicted sites had a mean of 39 years and median of 30 years. Short (< 25 years) mean PMFI/FRs were in Arizona and New Mexico and scattered in other states. Long (> 55 years) mean PMFI/FRs were mainly from northern New Mexico to South Dakota. Mountain sites often had a large range in PMFI/FR. Nearly all 342 estimates are for old forests with a history of primarily low-severity fire, found across only about 34% of historical dry-forest area. Frequent fire (PMFI/FR < 25 years) was found across only about 14% of historical dry-forest area, with 86% having multidecadal rates of low-severity fire. Historical fuels (e.g., understory shrubs and small trees) could fully recover between multidecadal fires, allowing some denser forests and some ecosystem processes and wildlife habitat to be less limited by fire. Lower historical rates mean less restoration treatment is needed before beginning managed fire for resource benefits, where feasible. Mimicking patterns of variability in historical low-severity fire regimes would likely benefit biological diversity and ecosystem functioning. PMID:28199416 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=338026&Lab=NRMRL&keyword=Control+AND+design&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=338026&Lab=NRMRL&keyword=Control+AND+design&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">SWMM LID Module Validation Study</a> <a target="_blank" rel="noopener noreferrer" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> EPA’s Storm Water Management Model (SWMM) is a computational code heavily relied upon by industry for the simulation of wastewater and stormwater infrastructure performance. Many municipalities are relying on SWMM results to design multi-billion-dollar, multi-decade infrastructu... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC53A1250K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC53A1250K">Detecting influences on California drought intervals using isotopes in tree-ring cellulose</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kanner, L. C.; Buenning, N. H.; Stott, L. D.; Stahle, D. W. 2012-12-01 Multi-decadal drought events have characterized climate variability in California over the last century. However, the causes of interannual precipitation variability and the origins of multi-decadal drought in California remain unclear. We utilize the oxygen isotopic composition (δ18O) of tree-ring cellulose in combination with previously developed ring-width measurements to trace the delivery of moisture to the region and investigate ocean-atmosphere patterns that might generate prolonged drought. Of the 36 Quercus douglasii (blue oak) sites in the California central valley, we have focused our work at two locations - one north of Los Angeles (34.74°N, 120°W, 1036 masl) and the other east of San Francisco (37.88°N 121.97°W, 182 masl). Using cores from at least five different trees at each location, tree-ring cellulose δ18O was measured for each year of growth from 1954 to 2004. The δ18O values of tree-ring cellulose range from 29‰ to 34‰ (VSMOW) at both sites and exhibit shared interannual variance (r = 0.43, p < 0.01). To trace changes in moisture delivery, we apply a biophysical model of cellulose δ18O and derive a proxy for rainfall δ18O. A reasonable approximation of rainfall δ18O is soil water δ18O, which, based on the biophysical model, can be estimated using cellulose δ18O, relative humidity, and temperature. High-resolution climate data from PRISM are combined with our cellulose measurements to compute soil water δ18O (and thus rainfall δ18O). Calculated rainfall δ18O is well correlated between the two locations (r = 0.55, p < 0.001) and the variance in δ18O at each site is 6‰. In terms of regional climate changes, our rainfall δ18O proxy exhibits a positive correlation with local precipitation amount, inferred from tree-ring width (r = 0.66, p < 0.001). This positive correlation suggests rainfall amount cannot be the main influence on the isotopic composition because changes in δ18O solely due to amount typically occur in the negative direction (the so-called amount effect usually observed in the tropics). Instead, we hypothesize that shifts in the moisture source region are of primary importance because moisture from high latitude sources has a lower isotopic composition compared to subtropical regions. Using NCAR reanalysis data, wind field anomalies suggest that moisture is derived from the north during dry years (low δ18O) and from the subtropics during wet years (high δ18O). Additional processes such as condensation height and post-condensation effects may also be important in controlling isotopic variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3948066','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3948066">Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Knudsen, Mads Faurschou; Jacobsen, Bo Holm; Seidenkrantz, Marit-Solveig; Olsen, Jesper 2014-01-01 The Atlantic Multidecadal Oscillation (AMO) represents a significant driver of Northern Hemisphere climate, but the forcing mechanisms pacing the AMO remain poorly understood. Here we use the available proxy records to investigate the influence of solar and volcanic forcing on the AMO over the last ~450 years. The evidence suggests that external forcing played a dominant role in pacing the AMO after termination of the Little Ice Age (LIA; ca. 1400–1800), with an instantaneous impact on mid-latitude sea-surface temperatures that spread across the North Atlantic over the ensuing ~5 years. In contrast, the role of external forcing was more ambiguous during the LIA. Our study further suggests that the Atlantic Meridional Overturning Circulation is important for linking external forcing with North Atlantic sea-surface temperatures, a conjecture that reconciles two opposing theories concerning the origin of the AMO. PMID:24567051 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24567051','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24567051">Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Knudsen, Mads Faurschou; Jacobsen, Bo Holm; Seidenkrantz, Marit-Solveig; Olsen, Jesper 2014-02-25 The Atlantic Multidecadal Oscillation (AMO) represents a significant driver of Northern Hemisphere climate, but the forcing mechanisms pacing the AMO remain poorly understood. Here we use the available proxy records to investigate the influence of solar and volcanic forcing on the AMO over the last ~450 years. The evidence suggests that external forcing played a dominant role in pacing the AMO after termination of the Little Ice Age (LIA; ca. 1400-1800), with an instantaneous impact on mid-latitude sea-surface temperatures that spread across the North Atlantic over the ensuing ~5 years. In contrast, the role of external forcing was more ambiguous during the LIA. Our study further suggests that the Atlantic Meridional Overturning Circulation is important for linking external forcing with North Atlantic sea-surface temperatures, a conjecture that reconciles two opposing theories concerning the origin of the AMO. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170001388','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170001388">A Multi-Decadal Sample Return Campaign Will Advance Lunar and Solar System Science and Exploration by 2050</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Neal, C. R.; Lawrence, S. J. 2017-01-01 There have been 11 missions to the Moon this century, 10 of which have been orbital, from 5 different space agencies. China became the third country to successfully soft-land on the Moon in 2013, and the second to successfully remotely operate a rover on the lunar surface. We now have significant global datasets that, coupled with the 1990s Clementine and Lunar Prospector missions, show that the sample collection is not representative of the lithologies present on the Moon. The M3 data from the Indian Chandrayaan-1 mission have identified lithologies that are not present/under-represented in the sample collection. LRO datasets show that volcanism could be as young as 100 Ma and that significant felsic complexes exist within the lunar crust. A multi-decadal sample return campaign is the next logical step in advancing our understanding of lunar origin and evolution and Solar System processes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45..327G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45..327G">A New Method for Interpreting Nonstationary Running Correlations and Its Application to the ENSO-EAWM Relationship</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Geng, Xin; Zhang, Wenjun; Jin, Fei-Fei; Stuecker, Malte F. 2018-01-01 We here propose a new statistical method to interpret nonstationary running correlations by decomposing them into a stationary part and a first-order Taylor expansion approximation for the nonstationary part. Then, this method is applied to investigate the nonstationary behavior of the El Niño-Southern Oscillation (ENSO)-East Asian winter monsoon (EAWM) relationship, which exhibits prominent multidecadal variations. It is demonstrated that the first-order approximation of the nonstationary part can be expressed to a large extent by the impact of the nonlinear interaction between the Atlantic Multidecadal Oscillation (AMO) and ENSO (AMO*Niño3.4) on the EAWM. Therefore, the nonstationarity in the ENSO-EAWM relationship comes predominantly from the impact of an AMO modulation on the ENSO-EAWM teleconnection via this key nonlinear interaction. This general method can be applied to investigate nonstationary relationships that are often observed between various different climate phenomena. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26612836','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26612836">Multidecadal increase in North Atlantic coccolithophores and the potential role of rising CO₂.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rivero-Calle, Sara; Gnanadesikan, Anand; Del Castillo, Carlos E; Balch, William M; Guikema, Seth D 2015-12-18 As anthropogenic carbon dioxide (CO2) emissions acidify the oceans, calcifiers generally are expected to be negatively affected. However, using data from the Continuous Plankton Recorder, we show that coccolithophore occurrence in the North Atlantic increased from ~2 to more than 20% from 1965 through 2010. We used random forest models to examine more than 20 possible environmental drivers of this change, finding that CO2 and the Atlantic Multidecadal Oscillation were the best predictors, leading us to hypothesize that higher CO2 levels might be encouraging growth. A compilation of 41 independent laboratory studies supports our hypothesis. Our study shows a long-term basin-scale increase in coccolithophores and suggests that increasing CO2 and temperature have accelerated the growth of a phytoplankton group that is important for carbon cycling. Copyright © 2015, American Association for the Advancement of Science. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC52B..01W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC52B..01W">The 2016 southeastern US drought: an extreme departure from centennial wetting and cooling</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Williams, P.; Cook, B. I.; Smerdon, J. E.; Bishop, D. A.; Seager, R.; Mankin, J. S. 2017-12-01 The southeastern United States (SE US) drought in fall 2016 appeared exceptional based on its wildfire and water-supply impacts but the current monitoring framework does not readily facilitate evaluation of moisture-balance anomalies in a centennial context. A new method to extend modeled soil-moisture records back to 1895 is developed using monthly climate data. Since 1895, October-November 2016 soil moisture (0-200 cm) in the SE US was likely the second lowest on record, behind 1954. This severe drought developed rapidly and was brought on by near record-low September-November precipitation and record-high September-November daily maximum temperatures (Tmax). Record Tmax drove record-high atmospheric moisture demand, accounting for 28% of the October-November 2016 soil-moisture anomaly. Drought and heat in fall 2016 contrasted strongly with 20th-century wetting and cooling trends, with few analogs after the mid-1950s. Dynamically, the exceptional drying in fall 2016 was driven by anomalous ridging over the central United States that reduced south-southwesterly moisture transports into the SE US by approximately 75%. These circulation anomalies were promoted by moderate La Niña conditions and warmth in the tropical North Atlantic, but these processes did not account for a majority of the SE US drying in fall 2016 and therefore imply a large role for internal atmospheric variability. The extended analysis back to 1895 indicates that SE US droughts as strong as the 2016 event are more likely than indicated from a shorter 60-year perspective, and continued multi-decadal swings in precipitation may combine with future warming to further enhance the likelihood of such events. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGC54B..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGC54B..04A">Weather-forced variations of Central and East Pacific ENSO events</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Alexander, M. A.; Newman, M.; Shin, S. 2010-12-01 It has been suggested that a possible outcome of climate change is an increase in the occurrence of “Modoki” or central Pacific El Nino events relative to canonical eastern Pacific El Nino events, and that this change may already be occurring. Such a determination, however, is complicated by possible natural variations of the two types of events. How large a change in the relative occurrence can be expected from purely internal variability? To explore this question, a “patterns-based” red noise null hypothesis is constructed from 40 years of observed seasonally-averaged SST, 20 deg C thermocline depth, and surface zonal wind stress anomalies. Patterns-based (or multivariate) red noise differs from “local” (or univariate) red noise since it allows for non-local advective processes; for example, weather noise driving surface wind stress in one location to produce an ocean response in a different location. It is shown that natural random variations of the central Pacific to east Pacific El Nino occurrence ratio are large enough that they could account for all past observed differences as well as all differences found in the SRESA1B runs of all AR4 climate models. Additionally, the correlation between Nino3 and Nino4 SST indices over 30-yr periods can range between 0.7 and 0.9 simply due to such variations in noise, with apparent multidecadal “trends” during which the value increases or decreases. Further analysis shows the different spatial patterns of “noise” (i.e., random weather forcing) that can lead to the development of central vs. eastern Pacific ENSO events or various combinations thereof. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140007298','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140007298">Climate Scenarios for the NASA / USAID SERVIR Project: Challenges for Multiple Planning Horizons</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Robertson, Franklin R.; Roberts, J. B.; Lyon, B.; Funk, C.; Bosilovich, M. G. 2014-01-01 SERVIR, an acronym meaning "to serve" in Spanish, is a joint venture between NASA and the U.S. Agency for International Development (USAID) which provides satellite-based Earth observation data, modeling, and science applications to help developing nations in Central America, East Africa and the Himalayas improve environmental decision making. Anticipating climate variability / climate change impacts has now become an important component of the SERVIR efforts to build capacity in these regions. Uncertainty in hydrometeorological components of climate variations and exposure to extreme events across scales from weather to climate are of particular concern. We report here on work to construct scenarios or outlooks that are being developed as input drivers for decision support systems (DSSs) in a variety of settings. These DSSs are being developed jointly by a broad array NASA Applied Science Team (AST) Investigations and user communities in the three SERVIR Hub Regions, Central America, East Africa and the Himalayas. Issues span hydrologic / water resources modeling, agricultural productivity, and forest carbon reserves. The scenarios needed for these efforts encompass seasonal forecasts, interannual outlooks, and likely decadal / multi-decadal trends. Providing these scenarios across the different AST efforts enables some level of integration in considering regional responses to climate events. We will discuss a number of challenges in developing this continuum of scenarios including the identification and "mining" of predictability, addressing multiple continental regions, issues of downscaling global model integrations to regional / local applications (i.e. hydrologic and crop modeling). We compare / contrast the role of the U.S. National Multi- Model Experiment initiative in seasonal forecasts and the CMIP-5 climate model experiments in supporting these efforts. Examples of these scenarios, their use, and an assessment of their utility as well as limitations will be presented. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OcDyn..65..255G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OcDyn..65..255G">Climate change impact on North Sea wave conditions: a consistent analysis of ten projections</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Grabemann, Iris; Groll, Nikolaus; Möller, Jens; Weisse, Ralf 2015-02-01 Long-term changes in the mean and extreme wind wave conditions as they may occur in the course of anthropogenic climate change can influence and endanger human coastal and offshore activities. A set of ten wave climate projections derived from time slice and transient simulations of future conditions is analyzed to estimate the possible impact of anthropogenic climate change on mean and extreme wave conditions in the North Sea. This set includes different combinations of IPCC SRES emission scenarios (A2, B2, A1B, and B1), global and regional models, and initial states. A consistent approach is used to provide a more robust assessment of expected changes and uncertainties. While the spatial patterns and the magnitude of the climate change signals vary, some robust features among the ten projections emerge: mean and severe wave heights tend to increase in the eastern parts of the North Sea towards the end of the twenty-first century in nine to ten projections, but the magnitude of the increase in extreme waves varies in the order of decimeters between these projections. For the western parts of the North Sea more than half of the projections suggest a decrease in mean and extreme wave heights. Comparing the different sources of uncertainties due to models, scenarios, and initial conditions, it can be inferred that the influence of the emission scenario on the climate change signal seems to be less important. Furthermore, the transient projections show strong multi-decadal fluctuations, and changes towards the end of the twenty-first century might partly be associated with internal variability rather than with systematic changes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..465A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..465A">Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang 2017-08-01 This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4061A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4061A">Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang 2018-06-01 This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS41A1989L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS41A1989L">Interhemispheric Changes in Atlantic Ocean Heat Content and Their Link to Global Monsoons</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lopez, H.; Lee, S. K.; Dong, S.; Goni, G. J. 2015-12-01 This study tested the hypothesis whether low frequency decadal variability of the South Atlantic meridional heat transport (SAMHT) influences decadal variability of the global monsoons. A multi-century run from a state-of-the-art coupled general circulation model is used as basis for the analysis. Our findings indicate that multi-decadal variability of the South Atlantic Ocean plays a key role in modulating atmospheric circulation via interhemispheric changes in Atlantic Ocean heat content. Weaker SAMHT produces anomalous ocean heat divergence over the South Atlantic resulting in negative ocean heat content anomaly about 15 years later. This, in turn, forces a thermally direct anomalous interhemispheric Hadley circulation in the atmosphere, transporting heat from the northern hemisphere (NH) to the southern hemisphere (SH) and moisture from the SH to the NH, thereby intensify (weaken) summer (winter) monsoon in the NH and winter (summer) monsoon in the SH. Results also show that anomalous atmospheric eddies, both transient and stationary, transport heat northward in both hemispheres producing eddy heat flux convergence (divergence) in the NH (SH) around 15-30°, reinforcing the anomalous Hadley circulation. The effect of eddies on the NH (SH) poleward of 30° is opposite with heat flux divergence (convergence), which must be balanced by sinking (rising) motion, consistent with a poleward (equatorward) displacement of the jet stream and mean storm track. The mechanism described here could easily be interpreted for the case of strong SAMHT, with the reverse influence on the interhemispheric atmospheric circulation and monsoons. Overall, SAMHT decadal variability leads its atmospheric response by about 15 years, suggesting that the South Atlantic is a potential predictor of global climate variability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP41C2275R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP41C2275R">Bayesian Models for Streamflow and River Network Reconstruction using Tree Rings</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ravindranath, A.; Devineni, N. 2016-12-01 Water systems face non-stationary, dynamically shifting risks due to shifting societal conditions and systematic long-term variations in climate manifesting as quasi-periodic behavior on multi-decadal time scales. Water systems are thus vulnerable to long periods of wet or dry hydroclimatic conditions. Streamflow is a major component of water systems and a primary means by which water is transported to serve ecosystems' and human needs. Thus, our concern is in understanding streamflow variability. Climate variability and impacts on water resources are crucial factors affecting streamflow, and multi-scale variability increases risk to water sustainability and systems. Dam operations are necessary for collecting water brought by streamflow while maintaining downstream ecological health. Rules governing dam operations are based on streamflow records that are woefully short compared to periods of systematic variation present in the climatic factors driving streamflow variability and non-stationarity. We use hierarchical Bayesian regression methods in order to reconstruct paleo-streamflow records for dams within a basin using paleoclimate proxies (e.g. tree rings) to guide the reconstructions. The riverine flow network for the entire basin is subsequently modeled hierarchically using feeder stream and tributary flows. This is a starting point in analyzing streamflow variability and risks to water systems, and developing a scientifically-informed dynamic risk management framework for formulating dam operations and water policies to best hedge such risks. We will apply this work to the Missouri and Delaware River Basins (DRB). Preliminary results of streamflow reconstructions for eight dams in the upper DRB using standard Gaussian regression with regional tree ring chronologies give streamflow records that now span two to two and a half centuries, and modestly smoothed versions of these reconstructed flows indicate physically-justifiable trends in the time series. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP41A1279B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP41A1279B">High-resolution lake sediment archives of midcontinental atmospheric and hydroclimate variability during the Medieval Climate Anomaly and Little Ice Age</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bird, B. W.; Wilson, J. J.; Gilhooly, W., III; Steinman, B. A.; Stamps, L. G.; Ahmed, M. N.; Abbott, M. B.; Pompeani, D. P.; Hillman, A. L.; Finkenbinder, M. S. 2017-12-01 Hydroclimate variability in the midcontinental United States (US) during the last 2000 years is not well characterized because there are few high-resolution paleoclimate records from the region. The majority of information about late Holocene midcontinental hydroclimate variability comes from scattered lake and bog sediment archives (primarily north of 42˚N) and gridded Palmer Drought Severity Index (PDSI) data calculated from a network of tree-ring records. The density of tree-ring records is lowest in the midcontinent, however, and decreases precipitously with time. In order to address this midcontinental paleoclimate data gap, we are developing a series of new lake-sediment-based hydroclimate records spanning 85˚ to 98˚W and 38˚ to 45˚N. New results from the eastern and central portions of the study area indicate large hydroclimate changes during the last 2000 years. Specifically, the Ohio and central Mississippi River valleys were wetter during the Medieval Climate Anomaly (MCA; 950-1250 CE), but drier during the Little Ice Age (LIA; 1350-1850 CE) with an especially severe, multi-decadal drought between 1350-1450 CE. Comparison with western (west of 96˚W) drought and fire records supports the existence of a hydroclimate dipole, with opposite hydroclimate conditions west and east of 96˚W. Isotopic changes in precipitation during the MCA and LIA suggest hydroclimate anomalies during these events were associated with mean state atmospheric circulation changes that resemble modern Pacific North American Mode (PNA) variability. Midcontinental Native American populations appear to have responded to MCA and LIA hydroclimate variability, with the latter event contributing to midcontinental depopulation between 1350-1500 CE. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/936956','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/936956"></a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kilbourne, K H; Quinn, T M; Guilderson, T P Water that forms the Florida Current, and eventually the Gulf Stream, coalesces in the Caribbean from both subtropical and equatorial sources. The equatorial sources are made up of, in part, South Atlantic water moving northward and compensating for southward flow at depth related to meridional overturning circulation. Subtropical surface water contains relatively high amounts of radiocarbon ({sup 14}C), whereas equatorial waters are influenced by the upwelling of low {sup 14}C water and have relatively low concentrations of {sup 14}C. We use a 250-year record of {Delta}{sup 14}C in a coral from southwestern Puerto Rico along with previously published coral {Delta}{supmore » 14}C records as tracers of subtropical and equatorial water mixing in the northern Caribbean. Data generated in this study and from other studies indicate that the influence of either of the two water masses can change considerably on interannual to interdecadal time scales. Variability due to ocean dynamics in this region is large relative to variability caused by atmospheric {sup 14}C changes, thus masking the Suess effect at this site. A mixing model produced using coral {Delta}{sup 14}C illustrates the time varying proportion of equatorial versus subtropical waters in the northern Caribbean between 1963 and 1983. The results of the model are consistent with linkages between multidecadal thermal variability in the North Atlantic and meridional overturning circulation. Ekman transport changes related to tradewind variability are proposed as a possible mechanism to explain the observed switches between relatively low and relatively high {Delta}{sup 14}C values in the coral radiocarbon records.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18543633','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18543633">Bottom-up and climatic forcing on the worldwide population of leatherback turtles.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Saba, Vincent S; Spotila, James R; Chavez, Francisco P; Musick, John A 2008-05-01 Nesting populations of leatherback turtles (Dermochelys coriacea) in the Atlantic and western Indian Oceans are increasing or stable while those in the Pacific are declining. It has been suggested that leatherbacks in the eastern Pacific may be resource limited due to environmental variability derived from the El Niño Southern Oscillation (ENSO), but this has yet to be tested. Here we explored bottom-up forcing and the responding reproductive output of nesting leatherbacks worldwide. We achieved this through an extensive review of leatherback nesting and migration data and by analyzing the spatial, temporal, and quantitative nature of resources as indicated by net primary production at post-nesting female migration and foraging areas. Leatherbacks in the eastern Pacific were the smallest in body size and had the lowest reproductive output due to less productive and inconsistent resources within their migration and foraging areas. This derived from natural interannual and multidecadal climate variability together with an influence of anthropogenic climate warming that is possibly affecting these natural cycles. The reproductive output of leatherbacks in the Atlantic and western Indian Oceans was nearly twice that of turtles in the eastern Pacific. The inconsistent nature of the Pacific Ocean may also render western Pacific leatherbacks susceptible to a more variable reproductive output; however, it appears that egg harvesting on nesting beaches is their major threat. We suggest that the eastern Pacific leatherback population is more sensitive to anthropogenic mortality due to recruitment rates that are lower and more variable, thus accounting for much of the population differences compared to Atlantic and western Indian turtles. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG51B..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG51B..03R">Characterizing Transitions Between Decadal States of the Tropical Pacific using State Space Reconstruction</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ramesh, N.; Cane, M. A. 2017-12-01 The complex coupled ocean-atmosphere system of the Tropical Pacific generates variability on timescales from intraseasonal to multidecadal. Pacific Decadal Variability (PDV) is among the key drivers of global climate, with effects on hydroclimate on several continents, marine ecosystems, and the rate of global mean surface temperature rise under anthropogenic greenhouse gas forcing. Predicting phase shifts in the PDV would therefore be highly useful. However, the small number of PDV phase shifts that have occurred in the observational record pose a substantial challenge to developing an understanding of the mechanisms that underlie decadal variability. In this study, we use a 100,000-year unforced simulation from an intermediate-complexity model of the Tropical Pacific region that has been shown to produce PDV comparable to that in the real world. We apply the Simplex Projection method to the NINO3 index from this model to reconstruct a shadow manifold that preserves the topology of the true attractor of this system. We find that the high- and low-variance phases of PDV emerge as a pair of regimes in a 3-dimensional state space, and that the transitions between decadal states lie in a highly predictable region of the attractor. We then use a random forest algorithm to develop a physical interpretation of the processes associated with these highly-predictable transitions. We find that transitions to low-variance states are most likely to occur approximately 2.5 years after an El Nino event, and that ocean-atmosphere variables in the southeastern Tropical Pacific play a crucial role in driving these transitions. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMOS22A..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMOS22A..08P">Revealing climate modes in steric sea levels: lessons learned from satellite geodesy, objective analyses and ocean reanalyses</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pfeffer, J.; Tregoning, P.; Purcell, A. P. 2017-12-01 Due to increased greenhouse gases emissions, the oceans are accumulating heat. In response to the ocean circulation and atmospheric forcing, the heat is irregularly redistributed within the oceans, causing sea level to rise at variable rates in space and time. These rates of steric expansion are extremely difficult to assess because of the sparsity of in-situ hydrographic observations available within the course of the 20th century. We compare here three methods to reconstruct the steric sea levels over the past 13, 25 and 58 years based on satellite geodesy, objective analyses and ocean reanalyses. The interannual to decadal variability of each dataset is explored with a model merging six climate indices representative of the natural variability of the ocean and climate system. Consistent regional patterns are identified for the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) in all datasets at all timescales. Despite the short time coverage (13 years), the combination of satellite geodetic data (altimetry and GRACE) also reveals significant steric responses to the North Pacific Gyre Oscillation (NPGO), Indian Dipole (IOD) and Indian ocean basinwide (IOBM) mode. The richer information content in the ocean reanalyses allows us to recover the regional fingerprints of the PDO, ENSO, NPGO, IOD and IOBM, but also of the Atlantic Multidecadal Oscillation (AMO) acting over longer time scales (40 to 60 years). Therefore, ocean reanalyses, coupled with climate mode analyses, constitute innovative and promising tools to investigate the mechanisms triggering the variability of sea level rise over the past decades. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://rosap.ntl.bts.gov/view/dot/31258','DOTNTL'); return false;" href="https://rosap.ntl.bts.gov/view/dot/31258">Development of SWITCH-Hawaii model: loads and renewable resources.</a> <a target="_blank" rel="noopener noreferrer" href="http://ntlsearch.bts.gov/tris/index.do">DOT National Transportation Integrated Search</a> 2016-08-01 This report summarizes work done to configure the SWITCH power system model using data for the Oahu power system. SWITCH is a planning model designed to choose optimal infrastructure investments for power systems over a multi-decade period. Investmen... </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://eric.ed.gov/?q=highway&pg=3&id=EJ774970','ERIC'); return false;" href="https://eric.ed.gov/?q=highway&pg=3&id=EJ774970">What's New in Boston?</a> <a target="_blank" rel="noopener noreferrer" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a> Hoffman, Morton Z.; Lichter, Robert 2007-01-01 The Big Dig, the multi-decade urban highway project has led to several changes in the U.S. most vulnerable city, Boston. Various parts of the city are being renovated to change the old tired industrial wasteland to a business and convention-oriented area. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMGC31A0105L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMGC31A0105L">Climate Variability and Ponderosa Pine Colonizations in Central Wyoming: Integrating Dendroecology and Dendroclimatology</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lesser, M.; Wentzel, C.; Gray, S.; Jackson, S. 2007-12-01 Many tree species are predicted to expand into new territory over the coming decades in response to changing climate. By studying tree expansions over the last several centuries we can begin to understand the mechanisms underlying these changes and anticipate their consequences for forest management. Woody-plant demographics and decadal to multidecadal climate variability are often closely linked in semi-arid regions. Integrated tree-ring analysis, combining dendroecology and dendroclimatology to document, respectively, the demographic history of the population and the climatic history of the region, can reveal ecological dynamics in response to climate variability. We studied four small, disjunct populations of Pinus ponderosa in the Bighorn Basin of north-central Wyoming. These populations are located 30 to 100 kilometers from the nearest core populations of ponderosa pine in the western Bighorn Mountains. Packrat midden studies have shown that ponderosa pine colonized the western slopes of the Bighorn Range 1500 years ago, so the disjunct populations in the basin must be younger. All trees (living and dead) at each of the four disjunct populations were mapped, cored, and then aged using tree-ring based techniques. We obtained records of hydroclimatic variability from the Bighorn Basin using four tree-ring series from Pinus flexilis (3 sites) and Pseudotsuga menziesii (1 site). The four disjunct populations were all established within the past 500 years. Initially, the populations grew slowly with low recruitment rates until the early 19th century, when they experienced one or more large recruitment pulses. These pulses coincided with extended wet periods in the climate reconstruction. However, similar wet periods before the 19th Century were not accompanied by recruitment pulses, indicating that other factors (e.g., population density, genetic variability) are also important in colonization and expansion. We are currently obtaining genetic data and carrying out population modeling to differentiate the effects of population dynamics, genetic variability, and climate variability on recruitment and expansion of these populations. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.1877L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.1877L">Investigating the Uncertainty in Global SST Trends Due to Internal Variations Using an Improved Trend Estimator</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lian, Tao; Shen, Zheqi; Ying, Jun; Tang, Youmin; Li, Junde; Ling, Zheng 2018-03-01 A new criterion was proposed recently to measure the influence of internal variations on secular trends in a time series. When the magnitude of the trend is greater than a theoretical threshold that scales the influence from internal variations, the sign of the estimated trend can be interpreted as the underlying long-term change. Otherwise, the sign may depend on the period chosen. An improved least squares method is developed here to further reduce the theoretical threshold and is applied to eight sea surface temperature (SST) data sets covering the period 1881-2013 to investigate whether there are robust trends in global SSTs. It is found that the warming trends in the western boundary regions, the South Atlantic, and the tropical and southern-most Indian Ocean are robust. However, robust trends are not found in the North Pacific, the North Atlantic, or the South Indian Ocean. The globally averaged SST and Indian Ocean Dipole indices are found to have robustly increased, whereas trends in the zonal SST gradient across the equatorial Pacific, Niño 3.4 SST, and the Atlantic Multidecadal Oscillation indices are within the uncertainty range associated with internal variations. These results indicate that great care is required when interpreting SST trends using the available records in certain regions and indices. It is worth noting that the theoretical threshold can be strongly influenced by low-frequency oscillations, and the above conclusions are based on the assumption that trends are linear. Caution should be exercised when applying the theoretical threshold criterion to real data. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.2362Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.2362Y">A First Look at Decadal Hydrological Predictability by Land Surface Ensemble Simulations</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yuan, Xing; Zhu, Enda 2018-03-01 The prediction of terrestrial hydrology at the decadal scale is critical for managing water resources in the face of climate change. Here we conducted an assessment by global land model simulations following the design of the fifth Coupled Model Intercomparison Project (CMIP5) decadal hindcast experiments, specifically testing for the sensitivity to perfect initial or boundary conditions. The memory for terrestrial water storage (TWS) is longer than 6 years over 11% of global land areas where the deep soil moisture and aquifer water have a long memory and a nonnegligible variability. Ensemble decadal predictions based on realistic initial conditions are skillful over 31%, 43%, and 59% of global land areas for TWS, deep soil moisture, and aquifer water, respectively. The fraction of skillful predictions for TWS increases by 10%-16% when conditioned on Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation indices. This study provides a first look at decadal hydrological predictability, with an improved skill when incorporating low-frequency climate information. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.8557U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.8557U">Emerging European winter precipitation pattern linked to atmospheric circulation changes over the North Atlantic region in recent decades</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ummenhofer, Caroline C.; Seo, Hyodae; Kwon, Young-Oh; Parfitt, Rhys; Brands, Swen; Joyce, Terrence M. 2017-08-01 Dominant European winter precipitation patterns over the past century, along with their associated extratropical North Atlantic circulation changes, are evaluated using cluster analysis. Contrary to the four regimes traditionally identified based on daily wintertime atmospheric circulation patterns, five distinct seasonal precipitation regimes are detected here. Recurrent precipitation patterns in each regime are linked to changes in atmospheric blocking, storm track, and sea surface temperatures across the North Atlantic region. Multidecadal variability in the frequency of the precipitation patterns reveals more (fewer) winters with wet conditions in northern (southern) Europe in recent decades and an emerging distinct pattern of enhanced wintertime precipitation over the northern British Isles. This pattern has become unusually common since the 1980s and is associated with changes in moisture transport and more frequent atmospheric river events. The observed precipitation changes post-1950 coincide with changes in storm track activity over the central/eastern North Atlantic toward the northern British Isles. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29239569','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29239569">Climate impact on malaria in northern Burkina Faso.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tourre, Yves M; Vignolles, Cécile; Viel, Christian; Mounier, Flore 2017-11-27 The Paluclim project managed by the French Centre National d'Etudes Spatiales (CNES) found that total rainfall for a 3-month period is a confounding factor for the density of malaria vectors in the region of Nouna in the Sahel administrative territory of northern Burkina Faso. Following the models introduced in 1999 by Craig et al. and in 2003 by Tanser et al., a climate impact model for malaria risk (using different climate indices) was created. Several predictions of this risk at different temporal scales (i.e. seasonal, inter-annual and low-frequency) were assessed using this climate model. The main result of this investigation was the discovery of a significant link between malaria risk and low-frequency rainfall variability related to the Atlantic Multi-decadal Oscillation (AMO). This result is critical for the health information systems in this region. Knowledge of the AMO phases would help local authorities to organise preparedness and prevention of malaria, which is of particular importance in the climate change context. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC21D..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC21D..05G">The climate sensitivity of food security in Mali - a historical perspective on availability and access dimensions</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Giannini, A.; Krishnamurthy, P. K.; Cousin, R.; Choularton, R. J. 2011-12-01 We present results based on an analysis of a 2005 livelihood survey of ~2000 rural households in ~200 villages scattered across Mali, a sparsely populated, large land-locked country in West Africa, to elucidate the role of climate variability and change in shaping availability and access dimensions of food security. The Comprehensive Food Security Vulnerability Analysis is a recurrent survey carried out by the World Food Programme and in-country partners to map out nutritional and socio-economic status during normal (~food secure) conditions in the hope of understanding underlying cause(s) and prevent the next food security crisis. We set the spatial characterization of food security that emerges from the CFSVA against the background of a varying climate, on intra-seasonal, interannual and multi-decadal time scales: through elucidation of the influence of climate on agricultural production we arrive at an interpretation of structural and conjunctural events affecting food security. We conclude with a discussion of possible interventions to reduce vulnerability. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70176085','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70176085">Precipitation changes in the western tropical Pacific over the past millennium</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Richey, Julie; Sachs, Julian P. 2016-01-01 Palau is linked to both meridional movement of the Intertropical Convergence Zone (ITCZ) and changes in the Pacific Walker Circula- tion (PWC) associated with the El Niño–Southern Oscillation. Thus, Palau’s hydroclimate should be sensitive to mean shifts in the ITCZ and PWC on decadal to centennial time scales. Using compound- specific hydrogen isotope ratios (δ2H) of dinosterol in lake sediments, we generated a decadal-resolution proxy record of hydroclimatic variability in Palau spanning the past 800 yr. Results indicate a dry- ing trend during the Little Ice Age in Palau, consistent with a south- ward displacement of the ITCZ. In addition to the secular drying trend, there are persistent large (~20‰) multi-decadal to centennial oscillations in the δ2H record, the most recent of which indicates an abrupt shift to drier conditions in the mid-1970s that coincides with a decadal-scale negative shift in the Southern Oscillation Index. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011WRR....47.0G06K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011WRR....47.0G06K">Steps toward “useful” hydroclimatic scenarios for water resource management in the Murray-Darling Basin</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kiem, Anthony S.; Verdon-Kidd, Danielle C. 2011-12-01 There is currently a distinct gap between what climate science can provide and information that is practically useful for (and needed by) natural resource managers. Improved understanding, and model representations, of interactions between the various climate drivers (both regional and global scale), combined with increased knowledge about the interactions between climate processes and hydrological processes at the regional scale, is necessary for improved attribution of climate change impacts, forecasting at a range of temporal scales and extreme event risk profiling (e.g., flood, drought, and bushfire). It is clear that the science has a long way to go in closing these research gaps; however, in the meantime water resource managers in the Murray-Darling Basin, and elsewhere, require hydroclimatic projections (i.e., seasonal to multidecadal future scenarios) that are regionally specific and, importantly, take into account the impacts, and associated uncertainties, of both natural climate variability and anthropogenic change. The strengths and weaknesses of various approaches for supplying this information are discussed in this paper. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41A0018E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41A0018E">The Stratospheric Aerosol and Gas Experiment III/International Space Station Mission: Science Objectives and Mission Status</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Eckman, R.; Zawodny, J. M.; Cisewski, M. S.; Flittner, D. E.; McCormick, M. P.; Gasbarre, J. F.; Damadeo, R. P.; Hill, C. A. 2015-12-01 The Stratospheric Aerosol and Gas Experiment III/International Space Station (SAGE III/ISS) is a strategic climate continuity mission which was included in NASA's 2010 plan, "Responding to the Challenge of Climate and Environmental Change: NASA's Plan for a Climate-Centric Architecture for Earth Observations and Applications from Space." SAGE III/ISS continues the long-term, global measurements of trace gases and aerosols begun in 1979 by SAGE I and continued by SAGE II and SAGE III on Meteor 3M. Using a well characterized occultation technique, the SAGE III instrument's spectrometer will measure vertical profiles of ozone, aerosols, water vapor, nitrogen dioxide, and other trace gases relevant to ozone chemistry. The mission will launch in 2016 aboard a Falcon 9 spacecraft.The primary objective of SAGE III/ISS is to monitor the vertical distribution of aerosols, ozone, and other trace gases in the Earth's stratosphere and troposphere to enhance our understanding of ozone recovery and climate change processes in the stratosphere and upper troposphere. SAGE III/ISS will provide data necessary to assess the state of the recovery in the distribution of ozone, extend the SAGE III aerosol measurement record that is needed by both climate models and ozone models, and gain further insight into key processes contributing to ozone and aerosol variability. The multi-decadal SAGE ozone and aerosol data sets have undergone intense community scrutiny for accuracy and stability. SAGE ozone data have been used to monitor the effectiveness of the Montreal Protocol.The ISS inclined orbit of 51.6 degrees is ideal for SAGE III measurements because the orbit permits solar occultation measurement coverage to approximately +/- 70 degrees of latitude. SAGE III/ISS will make measurements using the solar occultation measurement technique, lunar occultation measurement technique, and the limb scattering measurement technique. In this presentation, we describe the SAGE III/ISS mission, its implementation, the current status of the instrument, and the testing that took place this past summer. We will focus principally on the science to be conducted by the mission. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4519735','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4519735">The role of dynamically induced variability in the recent warming trend slowdown over the Northern Hemisphere</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Guan, Xiaodan; Huang, Jianping; Guo, Ruixia; Lin, Pu 2015-01-01 Since the slowing of the trend of increasing surface air temperature (SAT) in the late 1990 s, intense interest and debate have arisen concerning the contribution of human activities to the warming observed in previous decades. Although several explanations have been proposed for the warming-trend slowdown (WTS), none has been generally accepted. We investigate the WTS using a recently developed methodology that can successfully identify and separate the dynamically induced and radiatively forced SAT changes from raw SAT data. The dynamically induced SAT changes exhibited an obvious cooling effect relative to the warming effect of the adjusted SAT in the hiatus process. A correlation analysis suggests that the changes are dominated primarily by the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). Our results confirm that dynamically induced variability caused the WTS. The radiatively forced SAT changes are determined mainly by anthropogenic forcing, indicating the warming influence of greenhouse gases (GHGs), which reached levels of 400 ppm during the hiatus period. Therefore, the global SAT will not remain permanently neutral. The increased radiatively forced SAT will be amplified by increased dynamically induced SAT when the natural mode returns to a warming phase in the next period. PMID:26223491 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28827329','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28827329">Southern Annular Mode drives multicentury wildfire activity in southern South America.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Holz, Andrés; Paritsis, Juan; Mundo, Ignacio A; Veblen, Thomas T; Kitzberger, Thomas; Williamson, Grant J; Aráoz, Ezequiel; Bustos-Schindler, Carlos; González, Mauro E; Grau, H Ricardo; Quezada, Juan M 2017-09-05 The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531-2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37-54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665-1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721083','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721083">Resilience and stability of a pelagic marine ecosystem</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Lindegren, Martin; Checkley, David M.; Ohman, Mark D.; Koslow, J. Anthony; Goericke, Ralf 2016-01-01 The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS. PMID:26763697 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ClDy...35..577F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ClDy...35..577F">Reconstructed droughts for the southeastern Tibetan Plateau over the past 568 years and its linkages to the Pacific and Atlantic Ocean climate variability</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fang, Keyan; Gou, Xiaohua; Chen, Fahu; Li, Jinbao; D'Arrigo, Rosanne; Cook, Edward; Yang, Tao; Davi, Nicole 2010-09-01 We present a Palmer Drought Severity Index reconstruction ( r = 0.61, P < 0.01) from 1440 to 2007 for the southeastern Tibetan Plateau, based on tree rings of the forest fir ( Abies forrestii). Persistent decadal dry intervals were found in the 1440s-1460s, 1560s-1580s, 1700s, 1770s, 1810s, 1860s and 1980s, and the extreme wet epochs were the 1480s-1490s, 1510s-1520s, 1590s, 1610s-1630s, 1720s-1730s, 1800s, 1830s, 1870s, 1930s, 1950s and after the 1990s. Comparisons of our record with those identified in other moisture related reconstructions for nearby regions showed that our reconstructed droughts were relatively consistent with those found in other regions of Indochina, suggesting similar drought regimes. Spectral peaks of 2.3-5.5 years may be indicative of ENSO activity, as also suggested by negative correlations with SSTs in the eastern equatorial and southeastern Pacific Ocean. Significant multidecadal spectral peaks of 29.2-40.9 and 56.8-60.2 years were identified. As indicated by the spatial correlation patterns, the decadal-scale variability may be linked to SST variations in the northern Pacific and Atlantic Oceans. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28378830','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28378830">Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover.</a> <a target="_blank" rel="noopener noreferrer" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A; Zhou, Mingyu; Lenschow, Donald H; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua 2017-04-05 Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.456..124S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.456..124S">Sea surface temperature variability in the North Western Mediterranean Sea (Gulf of Lion) during the Common Era</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sicre, Marie-Alexandrine; Jalali, Bassem; Martrat, Belen; Schmidt, Sabine; Bassetti, Maria-Angela; Kallel, Nejib 2016-12-01 This study investigates the multidecadal-scale variability of sea surface temperatures (SSTs) in the convection region of the Gulf of Lion (NW Mediterranean Sea) over the full past 2000 yr (Common Era) using alkenone biomarkers. Our data show colder SSTs by 1.7 °C over most of the first millennium (200-800 AD) and by 1.3 °C during the Little Ice Age (LIA; 1400-1850 AD) than the 20th century mean (17.9 °C). Although on average warmer, those of the Medieval Climate Anomaly (MCA) (1000-1200 AD) were lower by 1 °C. We found a mean SST warming of 2 °C/100 yr over the last century in close agreement with the 0.22 and 0.26 °C/decade values calculated for the western Mediterranean Sea from in situ and satellite data, respectively. Our results also reveal strongly fluctuating SSTs characterized by cold extremes followed by abrupt warming during the LIA. We suggest that the coldest decades of the LIA were likely caused by prevailing negative EA states and associated anticyclone blocking over the North Atlantic resulting in cold continental northeasterly winds to blow over Western Europe and the Mediterranean region. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RvGeo..54..653H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RvGeo..54..653H">Progress on upwelling studies in the China seas</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hu, Jianyu; Wang, Xiao Hua 2016-09-01 East Asian marginal seas surrounding China exhibit rich ocean upwelling, mostly in response to the southwesterly summer monsoon. Upwelling in the China seas, namely, the South China Sea, the Taiwan Strait, the East China Sea, the Yellow Sea, and the Bohai Sea, has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem, socioeconomic, and climate impacts. This paper reviews the progress of upwelling studies in the China seas since the year 2000, by presenting the principal characteristics and new understanding of 12 major upwelling regions in the China seas. Upwelling exhibits long-term variability at intraseasonal to multidecadal scales as well as short-term variability frequently caused by tropical cyclones. It is also associated with the El Niño-Southern Oscillation, local environmental variation, and biogeochemical factors. The coastal upwelling around Hainan Island and the upwelling or cold dome northeast of Taiwan Island are specifically highlighted because they have attracted great interest for decades. This paper summarizes upwelling mechanisms in terms of wind, topography, tide, stratification, and background flow, with applications mostly to the China seas. Finally, we propose some topics for future upwelling research, i.e., potential intensification of coastal upwelling under global climate change, downwelling, intrusion of upwelling into coastal embayments, and the influence of upwelling on fishery and biogeochemical processes. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H53Q..05L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H53Q..05L">Improved Hourly and Sub-Hourly Gauge Data for Assessing Precipitation Extremes in the U.S.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lawrimore, J. H.; Wuertz, D.; Palecki, M. A.; Kim, D.; Stevens, S. E.; Leeper, R.; Korzeniewski, B. 2017-12-01 The NOAA/National Weather Service (NWS) Fischer-Porter (F&P) weighing bucket precipitation gauge network consists of approximately 2000 stations that comprise a subset of the NWS Cooperative Observers Program network. This network has operated since the mid-20th century, providing one of the longest records of hourly and 15-minute precipitation observations in the U.S. The lengthy record of this dataset combined with its relatively high spatial density, provides an important source of data for many hydrological applications including understanding trends and variability in the frequency and intensity of extreme precipitation events. In recent years NOAA's National Centers for Environmental Information initiated an upgrade of its end-to-end processing and quality control system for these data. This involved a change from a largely manual review and edit process to a fully automated system that removes the subjectivity that was previously a necessary part of dataset quality control and processing. An overview of improvements to this dataset is provided along with the results of an analysis of observed variability and trends in U.S. precipitation extremes since the mid-20th century. Multi-decadal trends in many parts of the nation are consistent with model projections of an increase in the frequency and intensity of heavy precipitation in a warming world. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70143408','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70143408">Extreme rainfall, vulnerability and risk: a continental-scale assessment for South America</a> <a target="_blank" rel="noopener noreferrer" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Vorosmarty, Charles J.; de Guenni, Lelys Bravo; Wollheim, Wilfred M.; Pellerin, Brian A.; Bjerklie, David M.; Cardoso, Manoel; D'Almeida, Cassiano; Colon, Lilybeth 2013-01-01 Extreme weather continues to preoccupy society as a formidable public safety concern bearing huge economic costs. While attention has focused on global climate change and how it could intensify key elements of the water cycle such as precipitation and river discharge, it is the conjunction of geophysical and socioeconomic forces that shapes human sensitivity and risks to weather extremes. We demonstrate here the use of high-resolution geophysical and population datasets together with documentary reports of rainfall-induced damage across South America over a multi-decadal, retrospective time domain (1960–2000). We define and map extreme precipitation hazard, exposure, affectedpopulations, vulnerability and risk, and use these variables to analyse the impact of floods as a water security issue. Geospatial experiments uncover major sources of risk from natural climate variability and population growth, with change in climate extremes bearing a minor role. While rural populations display greatest relative sensitivity to extreme rainfall, urban settings show the highest rates of increasing risk. In the coming decades, rapid urbanization will make South American cities the focal point of future climate threats but also an opportunity for reducing vulnerability, protecting lives and sustaining economic development through both traditional and ecosystem-based disaster risk management systems. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5381096','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5381096">Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover</a> <a target="_blank" rel="noopener noreferrer" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A.; Zhou, Mingyu; Lenschow, Donald H.; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua 2017-01-01 Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration. PMID:28378830 </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160010511&hterms=america&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Damerica','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160010511&hterms=america&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Damerica">Winter-to-Summer Precipitation Phasing in Southwestern North America: A Multi-Century Perspective from Paleoclimatic Model-Data Comparisons</a> <a target="_blank" rel="noopener noreferrer" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Coats, Sloan; Smerdon, Jason E.; Seager, Richard; Griffin, Daniel; Cook, Benjamin I. 2015-01-01 The phasing of winter-to-summer precipitation anomalies in the North American monsoon (NAM) region 2 (113.25 deg W-107.75 deg W, 30 deg N-35.25 deg N-NAM2) of southwestern North America is analyzed in fully coupled simulations of the Last Millennium and compared to tree ring reconstructed winter and summer precipitation variability. The models simulate periods with in-phase seasonal precipitation anomalies, but the strength of this relationship is variable on multidecadal time scales, behavior that is also exhibited by the reconstructions. The models, however, are unable to simulate periods with consistently out-of-phase winter-to-summer precipitation anomalies as observed in the latter part of the instrumental interval. The periods with predominantly in-phase winter-to-summer precipitation anomalies in the models are significant against randomness, and while this result is suggestive of a potential for dual-season drought on interannual and longer time scales, models do not consistently exhibit the persistent dual-season drought seen in the dendroclimatic reconstructions. These collective findings indicate that model-derived drought risk assessments may underestimate the potential for dual-season drought in 21st century projections of hydroclimate in the American Southwest and parts of Mexico. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14..217C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14..217C">High resolution reconstruction of monthly autumn and winter precipitation of Iberian Peninsula for last 150 years.</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cortesi, N.; Trigo, R.; González-Hidalgo, J. C.; Ramos, A. 2012-04-01 Precipitation over Iberian Peninsula (IP) presents large values of interannual variability and large spatial contrasts between wet mountainous regions in the north and dry regions in the southern plains. Unlike other European regions, IP was poorly monitored for precipitation during 19th century. Here we present a new approach to fill this gap. A set of 26 atmospheric circulation weather types (Trigo R.M. and DaCamara C.C., 2000) derived from a recent SLP dataset, the EMULATE (European and North Atlantic daily to multidecadal climate variability) Project, was used to reconstruct Iberian monthly precipitation from October to March during 1851-1947. Principal Component Regression Analysis was chosen to develop monthly precipitation reconstruction back to 1851 and calibrated over 1948-2003 period for 3030 monthly precipitation series of high-density homogenized MOPREDAS (Monthly Precipitation Database for Spain and Portugal) database. Validation was conducted over 1920-1947 at 15 key site locations. Results show high model performance for selected months, with a mean coefficient of variation (CV) around 0.6 during validation period. Lower CV values were achieved in western area of IP. Trigo, R. M., and DaCamara, C.C., 2000: "Circulation weather types and their impact on the precipitation regime in Portugal". Int. J. Climatol., 20, 1559-1581. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/940218','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/940218">Studies of regional-scale climate variability and change. Hidden Markov models and coupled ocean-atmosphere modes</a> <a target="_blank" rel="noopener noreferrer" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ghil, M.; Kravtsov, S.; Robertson, A. W. 2008-10-14 This project was a continuation of previous work under DOE CCPP funding, in which we had developed a twin approach of probabilistic network (PN) models (sometimes called dynamic Bayesian networks) and intermediate-complexity coupled ocean-atmosphere models (ICMs) to identify the predictable modes of climate variability and to investigate their impacts on the regional scale. We had developed a family of PNs (similar to Hidden Markov Models) to simulate historical records of daily rainfall, and used them to downscale GCM seasonal predictions. Using an idealized atmospheric model, we had established a novel mechanism through which ocean-induced sea-surface temperature (SST) anomalies might influencemore » large-scale atmospheric circulation patterns on interannual and longer time scales; we had found similar patterns in a hybrid coupled ocean-atmosphere-sea-ice model. The goal of the this continuation project was to build on these ICM results and PN model development to address prediction of rainfall and temperature statistics at the local scale, associated with global climate variability and change, and to investigate the impact of the latter on coupled ocean-atmosphere modes. Our main results from the grant consist of extensive further development of the hidden Markov models for rainfall simulation and downscaling together with the development of associated software; new intermediate coupled models; a new methodology of inverse modeling for linking ICMs with observations and GCM results; and, observational studies of decadal and multi-decadal natural climate results, informed by ICM results.« less </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.132..103V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.132..103V">Summer weather characteristics and periodicity observed over the period 1888-2013 in the region of Belgrade, Serbia</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vujović, Dragana; Todorović, Nedeljko; Paskota, Mira 2018-04-01 With the goal of finding summer climate patterns in the region of Belgrade (Serbia) over the period 1888-2013, different techniques of multivariate statistical analysis were used in order to analyze the simultaneous changes of a number of climatologic parameters. An increasing trend of the mean daily minimum temperature was detected. In the recent decades (1960-2013), this increase was much more pronounced. The number of days with the daily minimum temperature greater or equal to 20 °C also increased significantly. Precipitation had no statistically significant trend. Spectral analysis showed a repetitive nature of the climatologic parameters which had periods that roughly can be classified into three groups, with the durations of the following: (1) 6 to 7 years, (2) 10 to 18 years, and (3) 21, 31, and 41 years. The temperature variables mainly had one period of repetitiveness of 5 to 7 years. Among other variables, the correlations of regional fluctuations of the temperature and precipitation and atmospheric circulation indices were analyzed. The North Atlantic oscillation index had the same periodicity as that of the precipitation, and it was not correlated to the temperature variables. Atlantic multidecadal oscillation index correlated well to the summer mean daily minimum and summer mean temperatures. The underlying structure of the data was analyzed by principal component analysis, which detected the following four easily interpreted dimensions: More sunshine-Higher temperature, Precipitation, Extreme heats, and Changeable summer. </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC31D..02K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC31D..02K">Century long observation constrained global dynamic downscaling and hydrologic implication</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kim, H.; Yoshimura, K.; Chang, E.; Famiglietti, J. S.; Oki, T. 2012-12-01 It has been suggested that greenhouse gas induced warming climate causes the acceleration of large scale hydrologic cycles, and, indeed, many regions on the Earth have been suffered by hydrologic extremes getting more frequent. However, historical observations are not able to provide enough information in comprehensive manner to understand their long-term variability and/or global distributions. In this study, a century long high resolution global climate data is developed in order to break through existing limitations. 20th Century Reanalysis (20CR) which has relatively low spatial resolution (~2.0°) and longer term availability (140 years) is dynamically downscaled into global T248 (~0.5°) resolution using Experimental Climate Prediction Center (ECPC) Global Spectral Model (GSM) by spectral nudging data assimilation technique. Also, Global Precipitation Climatology Centre (GPCC) and Climate Research Unit (CRU) observational data are adopted to reduce model dependent uncertainty. Downscaled product successfully represents realistic geographical detail keeping low frequency signal in mean state and spatiotemporal variability, while previous bias correction method fails to reproduce high frequency variability. Newly developed data is used to investigate how long-term large scale terrestrial hydrologic cycles have been changed globally and how they have been interacted with various climate modes, such as El-Niño Southern Oscillation (ENSO) and Atlantic Multidecadal Oscillation (AMO). As a further application, it will be used to provide atmospheric boundary condition of multiple land surface models in the Global Soil Wetness Project Phase 3 (GSWP3). </li> <li> <a target="_blank" rel="noopener noreferrer" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A32G..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A32G..03G">Santa Ana Winds of Southern California: Their Climatology and Variability Spanning 6.5 Decades from Regional Dynamical Modelling</a> <a target="_blank" rel="noopener noreferrer" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Guzman-Morales, J.; Gershunov, A. 2015-12-01 Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region. In spite of their tremendous episodic impacts on the health, economy and mood of the region, climate-scale behavior of SAW is poorly understood. In the present work, we identify SAWs in mesoscale dynamical downscaling of a global reanalysis product and construct an hourly SAW catalogue spanning 65 years. We describe the long-term SAW climatology at relevant time-space resolutions, i.e, we developed local and regional SAW indices and analyse their variability on hourly, daily, annual, and multi-decadal timescales. Local and regional SAW indices are validated with available anemometer observations. Characteristic behaviors are revealed, e.g. the SAW intensity-duration relationship. At interdecadal time scales, we find that seasonal SAW activity is sensitive to prominent large-scale low-frequency modes of climate variability rooted in the tropical and north Pacific ocean-atmosphere system that are also known to affect the hydroclimate of this region. Lastly, we do not find any long-term trend in SAW frequency and intensity as previously reported. Instead, we identify a significant long-term trend in SAW behavior whereby contribution of extreme SAW events to total seasonal SAW activity has been increasing at the expense of moderate events. These findings motivate further investigation on SAW evolution in future climate and its impact on wildfires. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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Sample records for multidecadal internal variability