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Sample records for atlantic climate region

  1. The Atlantic Multi-Decadal Oscillation Impact on Regional Climate

    NASA Astrophysics Data System (ADS)

    Werner, Rolf; Valev, Dimitar; Atanassov, Atanas; Danov, Dimitar; Guineva, Veneta; Kirillov, Andrey S.

    2016-07-01

    The Atlantic multi-decadal oscillation (AMO) shows a period of about 60-70 years. Over the time span from 1860 up to 2014 the AMO has had a strong climate impact on the Northern Hemisphere. The AMO is considered to be related to the Atlantic overturning circulation, but the origin of the oscillation is not fully understood up till now. To study the AMO impact on climate, the Hadcrut4, Crut4 and HadSST3 temperature data sets have been employed in the current study. The influence of the AMO on the zonal and meridional temperature distribution has been investigated in detail. The strongest zonal AMO impact was obtained in the Arctic region. The results indicated that the AMO influence on temperature at Southern latitudes was opposite in phase compared to the temperature influence in the Northern Hemisphere, in agreement with the well known heat transfer phenomenon from South to North Atlantic. In the Northern Hemisphere the strongest AMO temperature impact was found over the Atlantic and America. In the West from American continent, over the Pacific, the AMO impact was the lowest obtained over the whole Northern Hemisphere. The Rocky Mountains and Sierra Madre, connected with it southwards, built up an atmospheric circulation barrier preventing a strong propagation of the AMO temperature signal westerly. The amplitude of the AMO index itself was greater during summer-fall. However stronger AMO influence on the Northern Hemisphere temperatures was found during the fall-winter season, when the differences between the Northern Hemisphere temperatures and the temperatures in the tropics were the greatest.

  2. CLIMATE IMPACTS ON NUTRIENT FLUXES IN STREAM FLOW IN THE MID-ATLANTIC REGION

    EPA Science Inventory

    As part of a national assessment process, researchers of the Mid-Atlantic Regional Assessment (MARA) are studying the impacts of climate variation and change on the natural and social systems of the Mid-Atlantic Region. This poster presents research investigating climate impacts ...

  3. IMPACT OF CLIMATE VARIATION AND CHANGE ON MID-ATLANTIC REGION HYDROLOGY AND WATER RESOURCES

    EPA Science Inventory

    The sensitivity of hydrology and water resources to climate variation and climate change is assessed for the Mid-Atlantic Region (MAR) of the United States. Observed streamflow, groundwater, and water-quality data are shown to vary in association with climate variation. Projectio...

  4. IMPACTS OF CLIMATE VARIATION AND CHANGE ON MID-ATLANTIC REGION HYDROLOGY

    EPA Science Inventory

    This study analyzes periodic variations in the climate of the mid-Atlantic Region over the last 100 years and uses general circulation models (GCMs) to project major climate trends for the next hundred years. Historical data include the Palmer Drought Severity Index (PDSI) for th...

  5. Climate change in the circum-North Atlantic region during the last deglaciation

    NASA Technical Reports Server (NTRS)

    Overpeck, Jonathan T.; Peterson, Larry C.; Kipp, Nilva; Imbrie, John; Rind, David

    1989-01-01

    A survey of new and published palaeoclimate data indicates that both the high- and low-latitude North Atlantic regions were characterized by at least three synchronous periods of abrupt climate change during the last glacial-to-interglacial transition. Climate model results suggest that changes in the melting history of the Laurentide Ice Sheet may explain much of this nonlinear response of the climate system to astronomical (Milankovitch) forcing.

  6. THE POTENTIAL IMPACTS OF CLIMATE CHANGE ON THE MID-ATLANTIC COASTAL REGION

    EPA Science Inventory

    This paper assesses the potential impacts of climate change on the mid-Atlantic coastal (MAC) region of the United States. In order of increasing uncertainty, it is projected that sea level, temperature and streamflow will increase in the MAC region in response to higher levels o...

  7. VULNERABILITY OF ECOSYSTEMS OF THE MID-ATLANTIC REGION, USA, TO CLIMATIC CHANGE

    EPA Science Inventory

    Changes in the distribution of vegetation in the mid-Atlantic region of the United States were explored for two climate-change scenarios. The equilibrium vegetation ecology (EVE) model was used to project the distribution of life forms and to combine these into biomes for a doubl...

  8. Regional impacts of Atlantic Forest deforestation on climate and vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Holm, J. A.; Chambers, J. Q.

    2012-12-01

    The Brazilian Atlantic Forest was a large and important forest due to its high biodiversity, endemism, range in climate, and complex geography. The original Atlantic Forest was estimated to cover 150 million hectares, spanning large latitudinal, longitudinal, and elevation gradients. This unique environment helped contribute to a diverse assemblage of plants, mammals, birds, and reptiles. Unfortunately, due to land conversion into agriculture, pasture, urban areas, and increased forest fragmentation, only ~8-10% of the original Atlantic Forest remains. Tropical deforestation in the Americas can have considerable effects on local to global climates, and surrounding vegetation growth and survival. This study uses a fully coupled, global climate model (Community Earth System Model, CESM v.1.0.1) to simulate the full removal of the historical Atlantic Forest, and evaluate the regional climatic and vegetation responses due to deforestation. We used the fully coupled atmosphere and land surface components in CESM, and a partially interacting ocean component. The vegetated grid cell portion of the land surface component, the Community Landscape Model (CLM), is divided into 4 of 16 plant functional types (PFTs) with vertical layers of canopy, leaf area index, soil physical properties, and interacting hydrological features all tracking energy, water, and carbon state and flux variables, making CLM highly capable in predicting the complex nature and outcomes of large-scale deforestation. The Atlantic Forest removal (i.e. deforestation) was conducted my converting all woody stem PFTs to grasses in CLM, creating a land-use change from forest to pasture. By comparing the simulated historical Atlantic Forest (pre human alteration) to a deforested Atlantic Forest (close to current conditions) in CLM and CESM we found that live stem carbon, NPP (gC m-2 yr-1), and other vegetation dynamics inside and outside the Atlantic Forest region were largely altered. In addition to vegetation

  9. CLIMATE CHANGE AND ECOSYSTEMS OF THE MID-ATLANTIC REGION

    EPA Science Inventory

    This paper discusses the current status of forested, wetland, freshwater and coastal ecosystems; the combined impacts of habitat alteration, pollution and non-native invasive species on those systems; how climatic changes could interact with existing stresses; potential managemen...

  10. High-resolution Coupled Regional Climate Modeling in the Atlantic Sector

    NASA Astrophysics Data System (ADS)

    Saravanan, R.; Hsieh, J.; Patricola, C. M.; Chang, P.; Li, M.

    2011-12-01

    Coupled Global Climate Models (CGCMs) that are used for centennial-scale climate projections typically lack sufficient horizontal resolution to properly resolve topographic features as well as fine-scale atmospheric and oceanic flow patterns that can have a significant impact on regional climate variability. A regional climate model can be used to carry out high-resolution climate simulations over specific regions on decadal timescales. Much of the research on regional climate modeling has been focused on the use of high-resolution uncoupled atmospheric models, but this approach neglects both the potential effects of air-sea feedbacks as well as the role of fine-scale oceanic phenomena, such as coastal upwelling, in regional climate variations. To address these omissions, we have developed a Coupled Regional Climate Model (CRCM), consisting of a high-resolution atmospheric model (WRF) coupled to a high-resolution ocean model (ROMS) in a region covering much of the Atlantic Ocean and surrounding continental areas. The two models use a common horizontal grid and exchange fluxes of momentum, heat, and freshwater every hour. We have carried out multi-year integrations using the CRCM at two different horizontal resolutions, 27km and 9km. We analyze tropical Atlantic variability in the CRCM simulations, focusing in particular on the statistics of simulated hurricanes, and the impact of air-sea interaction on the hurricane simulations. The CRCM produces fairly realistic hurricane activity, but with maximum intensities weaker than observations. To isolate the effect of air-sea interaction on hurricanes, we have also carried out a number of uncoupled (atmosphere-only) simulations of hurricane evolution initialized with "perfect initial conditions" obtained from the coupled integration, but using persisted sea surface temperatures as the surface boundary condition. Preliminary comparisons of the coupled and uncoupled simulations of hurricane evolution indicate that air

  11. North Atlantic Oscillation-related climate variability in a regional atmospheric model

    NASA Astrophysics Data System (ADS)

    Previdi, Michael; Veron, Dana E.

    2005-08-01

    Climate variability over the Greenland ice sheet associated with the North Atlantic Oscillation (NAO) is simulated with the Polar MM5 (PMM5) regional climate model (RCM). Two five-member monthly ensembles, each representative of high or low NAO extremes, are made, with data from the European Centre for Medium-Range Weather Forecasts 40-year reanalysis (ERA-40) used to provide the forcing for the RCM runs. Ensemble differences between the high and low NAO cases are discussed, and model output is compared to ERA-40 and to observations from automatic weather stations over Greenland. PMM5 is shown to reproduce several well-known features of NAO-related climate variability in the Greenland region, including colder near-surface air temperatures, lower sea level pressure, stronger westerly winds south of Greenland, and reduced precipitation over western Greenland and the Labrador Sea during high NAO months.

  12. Potential effects of climate change on freshwater ecosystems of the New England/Mid-Atlantic Region

    USGS Publications Warehouse

    Moore, M.V.; Pace, M.L.; Mather, J.R.; Murdoch, Peter S.; Howarth, R.W.; Folt, C.L.; Chen, C.-Y.; Hemond, Harold F.; Flebbe, P.A.; Driscoll, C.T.

    1997-01-01

    Numerous freshwater ecosystems, dense concentrations of humans along the eastern seaboard, extensive forests and a history of intensive land use distinguish the New England/Mid-Atlantic Region. Human population densities are forecast to increase in portions of the region at the same time that climate is expected to be changing. Consequently, the effects of humans and climatic change are likely to affect freshwater ecosystems within the region interactively. The general climate, at present, is humid continental, and the region receives abundant precipitation. Climatic projections for a 2 ??CO2 atmosphere, however, suggest warmer and drier conditions for much of this region. Annual temperature increases ranging from 3-5??C are projected, with the greatest increases occurring in autumn or winter. According to a water balance model, the projected increase in temperature will result in greater rates of evaporation and evapotranspiration. This could cause a 21 and 31% reduction in annual stream flow in the southern and northern sections of the region, respectively, with greatest reductions occurring in autumn and winter. The amount and duration of snow cover is also projected to decrease across the region, and summer convective thunderstorms are likely to decrease in frequency but increase in intensity. The dual effects of climate change and direct anthropogenic stress will most likely alter hydrological and biogeochemical processes, and, hence, the floral and faunal communities of the region's freshwater ecosystems. For example, the projected increase in evapotranspiration and evaporation could eliminate most bog ecosystems, and increases in water temperature may increase bioaccumulation, and possibly biomagnification, of organic and inorganic contaminants. Not all change may be adverse. For example, a decrease in runoff may reduce the intensity of ongoing estuarine eutrophication, and acidification of aquatic habitats during the spring snowmelt period may be

  13. Climatic Variability over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hurrell, J.; Hoerling, M. P.; Folland, C. K.

    INTRODUCTION WHAT IS THE NORTH ATLANTIC OSCILLATION AND HOW DOES IT IMPACT REGIONAL - CLIMATE? WHAT ARE THE MECHANISMS THAT GOVERN NORTH ATLANTIC OSCILLATION VARIABILITY? Atmospheric Processes Ocean Forcing of the Atmosphere CONCLUDING COMMENTS ON THE OTHER ASPECTS OF NORTH ATLANTIC CLIMATE - VARIABILITY REFERENCES

  14. Phase Variability of the Recent Climate in the North Atlantic Region

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Anisimov, Mikhail; Byshev, Vladimir; Neiman, Victor; Romanov, Juri; Sidorova, Alexandra

    2014-05-01

    The atmospheric pressure and near-surface temperature differences between the Azores High and the Icelandic Low for the period of 1900-2012 within the spatial-temporal average-out (20º latitude, 20º longitude and 12 years) were considered. The secular term of phase states of the system under consideration was found to divide into three non-intersecting subsets. Each of that was put in consequence with one of three climatic scenarios related to the periods of 1905-1935 (relatively warm phase), 1940-1970 (colder phase) and 1980-2000 (warmer phase). A life time of such a scenario lasted about 20-35 years, and the transition from one scenario to another covered 4-6 years, i.e. it run comparatively quickly. The revealed non-overlapping sub-aggregates of the thermodynamic indices related to each particular climate scenario gave an idea to follow the circulation peculiarities and the interrelated temperature differences within the limits of the Northern Atlantic ocean-atmosphere regional system. The results of this analysis bear evidence that the most probable intermittent strengthening and weakening of Hadley and Ferrell circulations occurred there in coincided phase. The analogous character of the climate system behavior was also detected in some other regional atmospheric activity centers that can be considered as a witness on the global nature of the detected phase type of modern climate inter-decadal variability. Hence, we have the grounds to suppose that mentioned above the short-period inter-decadal excitations of the modern climate have a global nature and appears everywhere. Finally, the attention was paid to the fact that at the early XXI century the thermodynamic state of the Northern Atlantic regional climate system has shown a tendency to face towards the situation, similar to the cooler scenario of the 1940-1970. We used the heat content of upper 700m Atlantic Ocean layer data from NODC to calculate its anomalies for the periods of 1955-1970, 1980-2000 and

  15. Assessing the link between Atlantic Niño 1 and drought over West Africa using CORDEX regional climate models

    NASA Astrophysics Data System (ADS)

    Adeniyi, Mojisola Oluwayemisi; Dilau, Kabiru Alabi

    2016-12-01

    The skill of Coordinated Regional Climate Downscaling Experiment (CORDEX) models (ARPEGE, CCLM, HIRHAM, RACMO, REMO, PRECIS, RegCM3, RCA, WRF and CRCM) in simulating the climate (precipitation, temperature and drought) of West Africa is determined using a process-based metric. This is done by comparing the CORDEX models' simulated and observed correlation coefficients between Atlantic Niño Index 1 (ATLN1) and the climate over West Africa. Strong positive correlation is observed between ATLN1 and the climate parameters at the Guinea Coast (GC). The Atlantic Ocean has Niño behaviours through the ATLN indices which influence the climate of the tropics. Drought has distinct dipole structure of correlation with ATLN1 (negative at the Sahel); precipitation does not have distinct dipole structure of correlation, while temperature has almost a monopole correlation structure with ATLN1 over West Africa. The magnitude of the correlation increases with closeness to the equatorial eastern Atlantic. Correlations between ATLN1 and temperature are mostly stronger than those between ATLN1 and precipitation over the region. Most models have good performance over the GC, but ARPEGE has the highest skill at GC. The PRECIS is the most skilful over Savannah and RCA over Sahel. These models can be used to downscale the projected climate at the region of their highest skill.

  16. GLOBAL CHANGE RESEARCH NEWS #34: PUBLICATION OF FACT SHEET BY EPA REGION 3, "HOW WILL CLIMATE CHANGE AFFECT THE MID-ATLANTIC REGION?"

    EPA Science Inventory

    EPA's Global Change Research Program is pleased to announce the publication of a fact sheet entitled, "How Will Climate Change Affect the Mid-Atlantic Region?." This information sheet was prepared and published by EPA's Region 3 office. It summarizes key findings from the Mid-Atl...

  17. An Investigation of the Relationship between the Components of School Climate and Leadership Behaviors on Student Achievement: Urban School Districts in the Mid-Atlantic Region

    ERIC Educational Resources Information Center

    Collins, Karmen J.

    2015-01-01

    The purpose of this research study was to investigate the relationship between the components of school climate and leadership behaviors on student achievement in an urban school district in the mid-atlantic region. School climate and leadership behaviors for the participating school districts was determined by the School Climate Survey (Corner…

  18. Modulation of extremes in the Atlantic region by modes of climate variability/change: A mechanistic coupled regional model study

    SciTech Connect

    Saravanan, Ramalingam

    2015-01-09

    During the course of this project, we have accomplished the following: 1) Explored the parameter space of component models to minimize regional model bias 2) Assessed the impact of air-sea interaction on hurricanes, focusing in particular on the role of the oceanic barrier layer 3) Contributed to the activities of the U.S. CLIVAR Hurricane Working Group 4) Assessed the impact of lateral and lower boundary conditions on extreme flooding events in the U.S. Midwest in regional model simulations 5) Analyzed the concurrent impact of El Niño-Southern Oscillation and Atlantic Meridional Mode on Atlantic Hurricane activity using observations and regional model simulations

  19. Abrupt climate variability in the North Atlantic region: Did the icebergs do it?

    NASA Astrophysics Data System (ADS)

    Barker, S.; Chen, J.; Gong, X.; Jonkers, L.; Knorr, G.; Thornalley, D. J.

    2014-12-01

    We present high resolution records of temperature and ice rafted debris over the last ~440Kyr from a sediment core retrieved from the NE Atlantic. Our records reveal that episodes of ice rafting typically occurred after abrupt cooling at the site. Because the site is sensitive to the earliest phases of ice rafting as recorded by other sites across the wider Atlantic, this suggests that icebergs were not the trigger for North Atlantic cold events. Moreover we find a different relationship between cooling and the arrival of rafted ice at a site ~750km to the SE of ours. We suggest that asynchronous cooling between these locations can be explained by the more gradual southward migration of the North Atlantic polar front. We describe a mechanism that can explain the occurrence of abrupt stadial events over Greenland as a non-linear response as regional cooling continues beyond the threshold necessary for sustaining ocean circulation in its 'warm' mode with active convection north of Iceland. Thus while the freshwater derived from melting icebergs may provide a positive feedback for enhancing and prolonging stadial conditions, it is probably not the trigger for northern stadial events.

  20. Holocene sea surface temperatures in the East African Coastal Current region and their relationship with North Atlantic climate

    NASA Astrophysics Data System (ADS)

    Kuhnert, Henning; Kuhlmann, Holger; Mohtadi, Mahyar; Pätzold, Jürgen

    2013-04-01

    The East African Coastal Current (EACC) is one of the western boundary currents of the Indian Ocean and represents the only pathway for southern water masses to enter the Arabian Sea. Today, sea surface temperatures (SST) in the western boundary currents region covary with those in large parts of the central tropical Indian Ocean. The latter play an important role in global climate by influencing the mean state of the North Atlantic Oscillation (NAO) and associated Atlantic SST anomalies (Hoerling et al., 2001). In the EACC region paleoclimate data are sparse and its Holocene temperature history is unexplored. We present data from a 5 m long sediment core retrieved off northern Tanzania where the EACC flows northward year-round. Proximity to the Pangani River mouth provides a steady sediment supply. We have reconstructed SST from Mg/Ca and stable oxygen isotope ratios (^18O) of the surface-dwelling planktonic foraminifera species Globigerinoides ruber (sensu stricto). Our record spans the time period from 9700 to 1400 years BP at an average temporal resolution of 40 years. The Holocene is characterized by a sequence of intervals representing cool, warm, cool, and intermediate SST, with boundaries at 7.8, 5.6, and 4.4 ka BP. SST anomalies relative to the series mean range from -0.6 to +0.75 ° C. This pattern strikingly resembles a Northwest Atlantic foraminiferal ^18O record (Cléroux et al., 2012), with warm Indian SST corresponding to low Atlantic foraminiferal ^18O (indicating low sea surface density). This matches the modern situation on the interdecadal time-scale, where a warm Indian Ocean leads to a shift of the NAO towards a positive mean state, which is accompanied by SST warming over much of the low- and mid-latitude western Atlantic and a displacement of the Gulf Stream path. We hypothesize that this mechanism also operates on millennial time-scales to explain the obvious similarities in the SST patterns observed in the Northwest Atlantic and western

  1. Final Report on Hierarchical Coupled Modeling and Prediction of Regional Climate Change in the Atlantic Sector

    SciTech Connect

    Saravanan, Ramalingam

    2011-10-30

    During the course of this project, we have accomplished the following: a) Carried out studies of climate changes in the past using a hierarchy of intermediate coupled models (Chang et al., 2008; Wan et al 2009; Wen et al., 2010a,b) b) Completed the development of a Coupled Regional Climate Model (CRCM; Patricola et al., 2011a,b) c) Carried out studies testing hypotheses testing the origin of systematic errors in the CRCM (Patricola et al., 2011a,b) d) Carried out studies of the impact of air-sea interaction on hurricanes, in the context of barrier layer interactions (Balaguru et al)

  2. The Atlantic Climate Change Program

    SciTech Connect

    Molinari, R.L. ); Battisti, D. ); Bryan, K. ); Walsh, J. )

    1994-07-01

    The Atlantic Climate Change Program (ACCP) is a component of NOAA's Climate and Global Change Program. ACCP is directed at determining the role of the thermohaline circulation of the Atlantic Ocean on global atmospheric climate. Efforts and progress in four ACCP elements are described. Advances include (1) descriptions of decadal and longer-term variability in the coupled ocean-atmosphere-ice system of the North Atlantic; (2) development of tools needed to perform long-term model runs of coupled simulations of North Atlantic air-sea interaction; (3) definition of mean and time-dependent characteristics of the thermohaline circulation; and (4) development of monitoring strategies for various elements of the thermohaline circulation. 20 refs., 4 figs., 1 tab.

  3. Climatic trends in the North Atlantic region during the last 2,000 years in an orbitally forced AOGCM simulation

    NASA Astrophysics Data System (ADS)

    Wagner, S.; Zorita, E.

    2013-12-01

    The global coverage of temporal highly resolved proxy-based climate reconstructions is extending to cover the last 2,000 years. It is thus important to fully understand the effect of the orbital forcing at these time scales, as the imprint of the orbital forcing becomes clearer when analyzing climate on time scales longer than the last 1,000 years. The slow-varying orbital parameters affect the seasonal distribution of the incoming solar radiation. Although changes are not as pronounced compared to the mid-Holocene, still distinct differences exist, with lower insolation between February and May and higher insolation between July and October over the mid- and high northern latitudes 2,000 years ago compared to present. Here, we analyze a simulation with the coupled climate model ECHO-G forced only with changes in orbital variations for the last 2,000 years. Other factors such as solar activity and greenhouse gas changes are set to constant pre-industrial values. The modeled near-surface temperature trends reflect the expected orbitally induced insolation trends over the northern hemispheric continents and the Arctic, with increased temperatures during May and reduced temperatures during October. Over the North Atlantic Ocean, however SST trends are not directly consistent to changes in orbital forcing throughout the year, mostly showing little or slight uniform cooling trends. The strength of the maximum overturning circulation in the North Atlantic Ocean also shows no clear-cut trends that can be linked to changes in external forcings. Other variables related to oceanic convection and surface heat fluxes indicate, however, spatially heterogeneous trend patterns. For example, regions south of Greenland and off Labrador show increases in convection that compensate the decreases over the Labrador and the Norwegian Sea. This pattern varies in intensity and spatial extent between the different winter half year months. Changes in oceanic convection and surface heat

  4. Contribution of the North Atlantic subtropical high to regional climate model (RCM) skill in simulating southeastern United States summer precipitation

    NASA Astrophysics Data System (ADS)

    Li, Laifang; Li, Wenhong; Jin, Jiming

    2015-07-01

    This study assesses the skill of advanced regional climate models (RCMs) in simulating southeastern United States (SE US) summer precipitation and explores the physical mechanisms responsible for the simulation skill at a process level. Analysis of the RCM output for the North American Regional Climate Change Assessment Program indicates that the RCM simulations of summer precipitation show the largest biases and a remarkable spread over the SE US compared to other regions in the contiguous US. The causes of such a spread are investigated by performing simulations using the Weather Research and Forecasting (WRF) model, a next-generation RCM developed by the US National Center for Atmospheric Research. The results show that the simulated biases in SE US summer precipitation are due mainly to the misrepresentation of the modeled North Atlantic subtropical high (NASH) western ridge. In the WRF simulations, the NASH western ridge shifts 7° northwestward when compared to that in the reanalysis ensemble, leading to a dry bias in the simulated summer precipitation according to the relationship between the NASH western ridge and summer precipitation over the southeast. Experiments utilizing the four dimensional data assimilation technique further suggest that the improved representation of the circulation patterns (i.e., wind fields) associated with the NASH western ridge substantially reduces the bias in the simulated SE US summer precipitation. Our analysis of circulation dynamics indicates that the NASH western ridge in the WRF simulations is significantly influenced by the simulated planetary boundary layer (PBL) processes over the Gulf of Mexico. Specifically, a decrease (increase) in the simulated PBL height tends to stabilize (destabilize) the lower troposphere over the Gulf of Mexico, and thus inhibits (favors) the onset and/or development of convection. Such changes in tropical convection induce a tropical-extratropical teleconnection pattern, which modulates the

  5. Contribution of the North Atlantic Subtropical High to Regional Climate Model (RCM) Skill in Simulating Southeastern United States Summer Precipitation

    NASA Astrophysics Data System (ADS)

    Li, L.; Li, W.; Jin, J.

    2014-12-01

    This study assesses the skill of advanced regional climate models (RCMs) in simulating Southeastern United States (SE US) summer precipitation and explores the mechanisms responsible for the simulation skill at a process level. Analysis of the RCM output for the North American Regional Climate Change Assessment Program (NARCCAP) indicates that the RCM simulations of summer precipitation show large biases and a remarkable spread over the SE US. The causes of such a spread are investigated by performing simulations using the Weather Research and Forecasting (WRF) model, a next-generation RCM developed by the US National Center for Atmospheric Research. The results show that the simulated biases in SE US summer precipitation are due mainly to the misrepresentation of the modeled North Atlantic Subtropical High (NASH) western ridge. In WRF simulations, the NASH western ridge shifts 7-deg northwestward compared to that in the reanalysis ensemble, leading to a dry bias in the simulated precipitation according to the "NASH western ridge - Southeast summer precipitation" relationship. Experiments utilizing the Four Dimensional Data Assimilation technique further suggest that the improved representation of the circulation patterns associated with the NASH western ridge substantially reduces the bias in simulating SE US summer precipitation. Our analysis of circulation dynamics indicates that the NASH western ridge in the WRF simulations is significantly influenced by planetary boundary layer (PBL) processes over the Gulf of Mexico. Specifically, a decrease (increase) in the simulated PBL height tends to stabilize (destabilize) the lower troposphere over the Gulf of Mexico, and thus inhibits (favors) the onset and/or development of convection. The changes in tropical convecton induce a tropical-extratropical teleconnection pattern, which modulates the circulation along the NASH western ridge in the WRF simulations and contributes to the precipitation biases over the SE US

  6. Modeling the Effects of Sahara Dust on the Climate and Water Cycle of the Tropical Atlantic/Caribbean Region

    NASA Astrophysics Data System (ADS)

    Lau, W. K.; Kim, K.

    2006-12-01

    We have investigated the direct effects of air-borne dust particles generated by dust storm over the Sahara desert on the water cycle of the tropical Atlantic and Caribbean region using the NASA finite-volume general circulation model (fvGCM). Global aerosol forcings are computed from radiative transfer functions derived from global distributions of five species of aerosols, i.e., dust, black carbon, organic carbon, sulphate and sea salt from the Goddard Chemistry Aerosol Radiation Transport (GOCART) model. Comparing fvGCM experiments without aerosol forcing, and with different combinations of aerosol forcing, we evaluate the impacts of aerosol direct heating on the onset, maintenance and evolution of the South American summer monsoon. We find that during the boreal summer, Saharan dust contribute to substantial heating of the atmosphere over the central and eastern equatorial Atlantic/Africa region through the "elevated heat pump" (EHP) mechanism, which works as follows. Absorption of solar radiation by the upper portion of the thick dust layer causes heating of the middle atmosphere, while the blocking of solar radiation by dust reduces surface solar radiation and leads to cooling over the desert land surface. When the dust layer is sufficiently thick, heating by the elevated portion of dust layer produces a pressure gradient in the mid-troposphere between the dust layer and the surrounding clean air. The pressure gradient draws in low level anomalous westerlies which brings in warm, moist air from the central and western Atlantic. The warm, moist air flows eastward, and rises above the cold surface air as they approach the West Africa continent, and converges in the middle troposphere to produce anomalous rain over the eastern Atlantic and West Africa coast. The latent heat of condensation from the increased rain causes more warm air to rise over the dust layer. Eventually, through the aforementioned aerosol heating and water cycle feedback, an anomalous Walker

  7. Nonlinear responses of southern African rainfall to forcing from Atlantic SST in a high-resolution regional climate model

    NASA Astrophysics Data System (ADS)

    Williams, C.; Kniveton, D.; Layberry, R.

    2009-04-01

    It is increasingly accepted that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or flooding, may have a far greater impact on human and natural systems than a changing mean. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The subcontinent is considered especially vulnerable to and ill-equipped (in terms of adaptation) for extreme events, due to a number of factors including extensive poverty, famine, disease and political instability. Rainfall variability is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. In this research, high resolution satellite derived rainfall data from the Microwave Infra-Red Algorithm (MIRA) are used as a basis for undertaking model experiments using a state-of-the-art regional climate model. The MIRA dataset covers the period from 1993-2002 and the whole of southern Africa at a spatial resolution of 0.1 degree longitude/latitude. Once the model's ability to reproduce extremes has been assessed, idealised regions of sea surface temperature (SST) anomalies are used to force the model, with the overall aim of investigating the ways in which SST anomalies influence rainfall extremes over southern Africa. In this paper, results from sensitivity testing of the regional climate model's domain size are briefly presented, before a comparison of simulated daily rainfall from the model with the satellite-derived dataset. Secondly, simulations of current climate and rainfall extremes from the model are compared to the MIRA dataset at daily timescales. Finally, the results from the idealised SST experiments are presented, suggesting highly nonlinear associations between rainfall extremes

  8. GLOBAL CHANGE RESEARCH NEWS #17: PUBLICATION OF MID-ATLANTIC REGIONAL ASSESSMENT

    EPA Science Inventory

    The report, "Preparing for a Changing Climate: The Potential Consequences of Climate Variability and Change - Mid-Atlantic Overview", summarizes the findings of the first Mid-Atlantic Regional Assessment. The Mid-Atlantic Regional Assessment was led by a team from The Pennsylvani...

  9. Regional Climate Tutorial: Assessing Regional Climate Change and Its Impacts

    NASA Astrophysics Data System (ADS)

    Barron, E.; Fisher, A.

    2002-05-01

    Recent scientific progress now enables credible projections of global changes in climate over long time periods. But people will experience global climate change where they live and work, and have difficulty thinking of a future beyond their grandchildren's lifetime. Although the task of projecting climate change and its impacts is far more challenging for regional and relatively near-term time scales, these are the scales at which actions most easily can be taken to moderate negative impacts. This tutorial will summarize what is known about projecting changes in regional climate, and about assessing the impacts for sectors such as forests, agriculture, fresh water quantity and quality, coastal zones, human health, and ecosystems. The Mid-Atlantic Regional Assessment (MARA) is used to provide context and illustrate how adaptation within the region and feedback from other regions influence the impacts that might be experienced.

  10. Tephra constraints on Rapid Climate Events (TRACE): precise correlation of marine and ice-core records in the North Atlantic region

    NASA Astrophysics Data System (ADS)

    Davies, Siwan; Abbott, Peter; Bourne, Anna; Cook, Eliza; Griggs, Adam; Meara, Rhian

    2013-04-01

    Little has challenged our understanding of climate change more so than the abruptness with which large-scale shifts in temperature occurred during the last glacial period. Atmospheric temperature jumps occurring within decades over Greenland were closely matched by rapid changes in North Atlantic sea surface temperatures and major re-organisation of the deep ocean circulation. Although these climatic instabilities are well-documented in various proxy records, the causal mechanisms of such short-lived oscillations remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Synchronisation of palaeoclimate records on a common timescale is inherently problematic, and unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is currently beyond our reach. TRACE - a 5 year project funded by the European Research Council - exploits the use of microscopic traces of volcanic events to precisely correlate the Greenland ice-cores with North Atlantic marine records. Tephrochronology has experienced a considerable step-change in recent years, with invisible layers of volcanic ash traced over much wider geographical regions than previously thought. What is more, recent work has identified new, previously unknown eruptions within both marine and ice-core records - several of which fall close to rapid climatic jumps imprinted in the proxy records. Here we draw upon examples of how these time-lines can be used to constrain the lead/lag responses between the atmospheric and oceanic systems during the last glacial period as well as some of the challenges that arise in the application of tephrochronology. Led by Swansea University, this project involves collaboration with groups at the University of Copenhagen, Aberystwyth University, Bangor University, University of St Andrews, Stockholm University, University of Tromsø and the University of East Anglia.

  11. A Regional Climate Mode Discovered in the North Atlantic: Dakar Niño/Niña.

    PubMed

    Oettli, Pascal; Morioka, Yushi; Yamagata, Toshio

    2016-01-07

    The interrannual variability of coastal sea surface temperature (SST) anomalies confined off Senegal is explored from a new viewpoint of the ocean-land-atmosphere interaction. The phenomenon may be classified into "coastal Niño/Niña" in the North Atlantic as discussed recently in the Northeastern Pacific and Southeastern Indian Oceans. The interannual variability of the regional mixed-layer temperature anomaly that evolves in boreal late fall and peaks in spring is associated with the alongshore wind anomaly, mixed-layer depth anomaly and cross-shore atmospheric pressure gradient anomaly, suggesting the existence of ocean-land-atmosphere coupled processes. The coupled warm (cold) event is named Dakar Niño (Niña). The oceanic aspect of the Dakar Niño (Niña) may be basically explained by anomalous warming (cooling) of the anomalously thin (thick) mixed-layer, which absorbs shortwave surface heat flux. In the case of Dakar Niña, however, enhancement of the entrainment at the bottom of the mixed-layer is not negligible.

  12. A Regional Climate Mode Discovered in the North Atlantic: Dakar Niño/Niña

    PubMed Central

    Oettli, Pascal; Morioka, Yushi; Yamagata, Toshio

    2016-01-01

    The interrannual variability of coastal sea surface temperature (SST) anomalies confined off Senegal is explored from a new viewpoint of the ocean-land-atmosphere interaction. The phenomenon may be classified into “coastal Niño/Niña” in the North Atlantic as discussed recently in the Northeastern Pacific and Southeastern Indian Oceans. The interannual variability of the regional mixed-layer temperature anomaly that evolves in boreal late fall and peaks in spring is associated with the alongshore wind anomaly, mixed-layer depth anomaly and cross-shore atmospheric pressure gradient anomaly, suggesting the existence of ocean-land-atmosphere coupled processes. The coupled warm (cold) event is named Dakar Niño (Niña). The oceanic aspect of the Dakar Niño (Niña) may be basically explained by anomalous warming (cooling) of the anomalously thin (thick) mixed-layer, which absorbs shortwave surface heat flux. In the case of Dakar Niña, however, enhancement of the entrainment at the bottom of the mixed-layer is not negligible. PMID:26739121

  13. Climatic variability in the Mediterranean region over the last 130 ka, sapropel formation and teleconnection with the North Atlantic and monsoon systems

    NASA Astrophysics Data System (ADS)

    Sanchez Goñi, M. F.; Fletcher, W. J.; Landais, A.

    2009-04-01

    Since the identification of millennial-scale climatic variability in Greenland and the North Atlantic (Dansgaard-Oeschger (D-O) and Heinrich (H) events) several questions remain open regarding the expression of this variability in the Mediterranean region, the oceanic and atmospheric mechanisms involved and how other forcings such as orbital parameters affect this variability. Several high-resolution pollen-rich marine cores retrieved in the framework of the IMAGES and ODP programs and covering at least the last 50,000 years have been analysed in the last decade. An array of terrestrial and marine micropalaeontological (pollen, foraminifer), sedimentary (microcharcoal, ice rafted detritus) and geochemical (d18O and d13C) tracers from the same sample set has allowed us to establish a direct correlation between the evolution of the atmospheric and oceanic reservoirs. All the D-O events have a counterpart in western Mediterranean terrestrial and marine ecosystems. Cold sea surface temperatures (SST) were synchronous with the expansion of semi-desert landscapes indicating a decrease in winter precipitation likely related with the northward displacement of the westerlies. SST increases were contemporaneous with the expansion of this forest and, therefore, the establishment of the Mediterranean climate, i.e. wet and mild winters with warm and dry summers. The best expression of the Mediterranean climate occurred during the Eemian, D-O 24, 21, 17-16, 8-7, 1 and the Holocene. These maxima occurred always during precession minima (seasonality maxima). The comparison of Mediterranean and Atlantic terrestrial and marine palaeoclimatic records of the last glacial period with Greenland temperature changes reveals that the Mediterranean region is distinctly impacted by precession. The comparison of this contrasting latitudinal climatic scenario with the global methane record which is also modulated by precession during the last climatic cycle reveals that the amplitude of

  14. Atlantic Ocean forcing of North American and European summer climate.

    PubMed

    Sutton, Rowan T; Hodson, Daniel L R

    2005-07-01

    Recent extreme events such as the devastating 2003 European summer heat wave raise important questions about the possible causes of any underlying trends, or low-frequency variations, in regional climates. Here, we present new evidence that basin-scale changes in the Atlantic Ocean, probably related to the thermohaline circulation, have been an important driver of multidecadal variations in the summertime climate of both North America and western Europe. Our findings advance understanding of past climate changes and also have implications for decadal climate predictions.

  15. Climate, fishery and society interactions: Observations from the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hamilton, Lawrence C.

    2007-11-01

    Interdisciplinary studies comparing fisheries-dependent regions across the North Atlantic find a number of broad patterns. Large ecological shifts, disastrous to historical fisheries, have resulted when unfavorable climatic events occur atop overfishing. The "teleconnections" linking fisheries crises across long distances include human technology and markets, as well as climate or migratory fish species. Overfishing and climate-driven changes have led to a shift downwards in trophic levels of fisheries takes in some ecosystems, from dominance by bony fish to crustaceans. Fishing societies adapt to new ecological conditions through social reorganization that have benefited some people and places, while leaving others behind. Characteristic patterns of demographic change are among the symptoms of such reorganization. These general observations emerge from a review of recent case studies of individual fishing communities, such as those conducted for the North Atlantic Arc research project.

  16. Variability and predictability of the North Atlantic wave climate

    NASA Astrophysics Data System (ADS)

    Woolf, D. K.; Challenor, P. G.; Cotton, P. D.

    2002-10-01

    Wave climate across the ocean basins can be described using satellite altimetry; here, we concentrate on the North Atlantic region. Waves in the North Atlantic are strongly seasonal and peak in the winter season. The northeastern sector of the Atlantic and adjoining shelf seas also exhibit exceptionally high interannual variability in the winter, with monthly average significant wave height varying by up to a factor of 2 from one year to the next. The strength and geographical distribution of variability is broadly consistent throughout the winter months (December-March). A large fraction of these wave height anomalies is associated with a single pattern of pressure anomalies that resembles the North Atlantic Oscillation (NAO). A predictor based on NAO dependence is "trained" from relatively recent satellite data and then tested against earlier satellite and in situ data. The predictor is successful in large areas of the North Atlantic, confirming a robust relationship between wave height anomalies and the NAO over the last few decades. A substantial rise (up to 0.6 m) in monthly mean wave heights on the northeastern Atlantic during the latter part of the twentieth century is attributable to changes in the NAO. Substantial residual anomalies in wave heights exist after the influence of the NAO has been subtracted; these are partly explained by a second pair of North Atlantic patterns in wave height anomalies and sea level pressure anomalies. This "East Atlantic" pattern is particularly influential in midwinter and affects the southern part of the northeastern sector (including the region of Seven Stones Light Vessel).

  17. Potential tropical Atlantic impacts on Pacific decadal climate trends

    NASA Astrophysics Data System (ADS)

    Chikamoto, Y.; Mochizuki, T.; Timmermann, A.; Kimoto, M.; Watanabe, M.

    2016-07-01

    The tropical Pacific cooling from the early 1990s to 2013 has contributed to the slowdown of globally averaged sea surface temperatures (SSTs). The origin of this regional cooling trend still remains elusive. Here we demonstrate that the remote impact of Atlantic SST anomalies, as well as local atmosphere-ocean interactions, contributed to the eastern Pacific cooling during this period. By assimilating observed three-dimensional Atlantic temperature and salinity anomalies into a coupled general circulation model, we are able to qualitatively reproduce the observed Pacific decadal trends of SST and sea level pressure (SLP), albeit with reduced amplitude. Although a major part of the Pacific SLP trend can be explained by equatorial Pacific SST forcing only, the origin of this low-frequency variability can be traced back further to the remote impacts of equatorial Atlantic and South Atlantic SST trends. Atlantic SST impacts on the atmospheric circulation can also be detected for the Northeastern Pacific, thus providing a linkage between Atlantic climate and Western North American drought conditions.

  18. Tephra constraints on Rapid Climate Events (TRACE): precise correlation of marine and ice-core records during the last glacial period in the North Atlantic region

    NASA Astrophysics Data System (ADS)

    Davies, S. M.; Griggs, A. J.; Abbott, P. M.; Bourne, A. J.; Purcell, C. S.; Hall, I. R.; Scourse, J. D.

    2014-12-01

    Little has challenged our understanding of climate change more so than the abruptness with which large-scale shifts in temperature occurred during the last glacial period. Atmospheric temperature jumps occurring within decades over Greenland were closely matched by rapid changes in North Atlantic sea surface temperatures and major re-organisation of the deep ocean circulation. Although these climatic instabilities are well-documented in various proxy records, the causal mechanisms of such short-lived oscillations remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Synchronisation of palaeoclimate records on a common timescale is inherently problematic, and unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is currently beyond our reach. TRACE - a 5 year project funded by the European Research Council - exploits the use of microscopic traces of tephra deposits to precisely correlate the Greenland ice-cores with North Atlantic marine records. Here we draw upon examples of how these time-lines can be used to constrain the lead/lag responses between the atmospheric and oceanic systems during the last glacial period. High-resolution proxy data from North Atlantic marine cores MD04-2829CQ from the Rosemary Bank and MD04 2820CQ from the Goban Spur are integrated with the Greenland ice-cores according to the position of common tephra isochrons. These direct tie-lines allow us to focus in detail on the relative timing of rapid warming transitions between Greenland and the North Atlantic ocean during the last glacial period.

  19. Interactive effects of climate change with nutrients, mercury, and freshwater acidification on key taxa in the North Atlantic Landscape Conservation Cooperative region.

    PubMed

    Pinkney, Alfred E; Driscoll, Charles T; Evers, David C; Hooper, Michael J; Horan, Jeffrey; Jones, Jess W; Lazarus, Rebecca S; Marshall, Harold G; Milliken, Andrew; Rattner, Barnett A; Schmerfeld, John; Sparling, Donald W

    2015-07-01

    The North Atlantic Landscape Conservation Cooperative LCC (NA LCC) is a public-private partnership that provides information to support conservation decisions that may be affected by global climate change (GCC) and other threats. The NA LCC region extends from southeast Virginia to the Canadian Maritime Provinces. Within this region, the US National Climate Assessment documented increases in air temperature, total precipitation, frequency of heavy precipitation events, and rising sea level, and predicted more drastic changes. Here, we synthesize literature on the effects of GCC interacting with selected contaminant, nutrient, and environmental processes to adversely affect natural resources within this region. Using a case study approach, we focused on 3 stressors with sufficient NA LCC region-specific information for an informed discussion. We describe GCC interactions with a contaminant (Hg) and 2 complex environmental phenomena-freshwater acidification and eutrophication. We also prepared taxa case studies on GCC- and GCC-contaminant/nutrient/process effects on amphibians and freshwater mussels. Several avian species of high conservation concern have blood Hg concentrations that have been associated with reduced nesting success. Freshwater acidification has adversely affected terrestrial and aquatic ecosystems in the Adirondacks and other areas of the region that are slowly recovering due to decreased emissions of N and sulfur oxides. Eutrophication in many estuaries within the region is projected to increase from greater storm runoff and less denitrification in riparian wetlands. Estuarine hypoxia may be exacerbated by increased stratification. Elevated water temperature favors algal species that produce harmful algal blooms (HABs). In several of the region's estuaries, HABs have been associated with bird die-offs. In the NA LCC region, amphibian populations appear to be declining. Some species may be adversely affected by GCC through higher temperatures and

  20. Interactive effects of climate change with nutrients, mercury, and freshwater acidification on key taxa in the North Atlantic Landscape Conservation Cooperative region

    USGS Publications Warehouse

    Pinkney, Alfred E.; Driscoll, Charles T.; Evers, David C.; Hooper, Michael J.; Horan, Jeffrey; Jones, Jess W.; Lazarus, Rebecca; Marshall, Harold G.; Milliken, Andrew; Rattner, Barnett A.; Schmerfeld, John J.; Sparling, Donald W.

    2015-01-01

    The North Atlantic Landscape Conservation Cooperative LCC (NA LCC) is a public–private partnership that provides information to support conservation decisions that may be affected by global climate change (GCC) and other threats. The NA LCC region extends from southeast Virginia to the Canadian Maritime Provinces. Within this region, the US National Climate Assessment documented increases in air temperature, total precipitation, frequency of heavy precipitation events, and rising sea level, and predicted more drastic changes. Here, we synthesize literature on the effects of GCC interacting with selected contaminant, nutrient, and environmental processes to adversely affect natural resources within this region. Using a case study approach, we focused on 3 stressors with sufficient NA LCC region-specific information for an informed discussion. We describe GCC interactions with a contaminant (Hg) and 2 complex environmental phenomena—freshwater acidification and eutrophication. We also prepared taxa case studies on GCC- and GCC-contaminant/nutrient/process effects on amphibians and freshwater mussels. Several avian species of high conservation concern have blood Hg concentrations that have been associated with reduced nesting success. Freshwater acidification has adversely affected terrestrial and aquatic ecosystems in the Adirondacks and other areas of the region that are slowly recovering due to decreased emissions of N and sulfur oxides. Eutrophication in many estuaries within the region is projected to increase from greater storm runoff and less denitrification in riparian wetlands. Estuarine hypoxia may be exacerbated by increased stratification. Elevated water temperature favors algal species that produce harmful algal blooms (HABs). In several of the region's estuaries, HABs have been associated with bird die-offs. In the NA LCC region, amphibian populations appear to be declining. Some species may be adversely affected by GCC through higher temperatures

  1. Synchronous climate changes in antarctica and the north atlantic

    PubMed

    Steig; Brook; White; Sucher; Bender; Lehman; Morse; Waddington; Clow

    1998-10-02

    Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.

  2. Synchronous climate changes in Antarctica and the North Atlantic

    USGS Publications Warehouse

    Steig, E.J.; Brook, E.J.; White, J.W.C.; Sucher, C.M.; Bender, M.L.; Lehman, S.J.; Morse, D.L.; Waddington, E.D.; Clow, G.D.

    1998-01-01

    Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events - the rapid warming that makes the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation - are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.

  3. Combining model simulations and paleoceanographic reconstructions for a process-based understanding of climate variability in the North Atlantic/Arctic region

    NASA Astrophysics Data System (ADS)

    Jungclaus, Johann; Lohmann, Katja; Kleiven, Helga

    2013-04-01

    Climate variations on multi-decadal to centennial time scales in the North Atlantic sector are often postulated to result from changes in the ocean's meridional overturning circulation and the associated heat and fresh water transports. Testing this mainly model-based hypothesis for the historically recorded climate change over the last millennium requires at least decadally-resolved constrains on the state of the ocean and its circulation. Such records have become increasingly available in recent years. For example, the European Union FP7 project THOR (Thermohaline Overturning - at Risk?), delivered the first combined assessment of water mass exchange between the Atlantic and the Nordic Seas. Coeval changes in both kinetic and chemical deep water proxies characterize variability in intensity and properties of North Atlantic Deep Water. Other recently published reconstructions provide information on variations of the oceanic heat transfer into the Arctic or the sea-ice extent in the Arcticover the last millennium. Here we show that high-resolution geological archives and model simulations over the last millennium can be combined to achieve a quantified, process-based understanding of ocean circulation variability and its impact on climate. On the one hand, reconstructions are necessary to evaluate the models' representation of hydrography, circulation and variability time-scales. On the other hand, the simulations provide the large-scale context to interpret the observed changes at discrete locations. Specifically, we address the dynamics of variations of the deep overflows across the Greenland Scotland Ridge, the coupling between deep flow and surface properties south of Greenland and the mechanisms leading to heat transport variations into the Arctic. We focus on internally-generated and externally forced variations in the ocean-atmosphere system over the last millennium and address also aspects of model uncertainty.

  4. Linking Agulhas Leakage Variability and North Atlantic Climate MIS 1-5a

    NASA Astrophysics Data System (ADS)

    Dyez, K. A.; Zahn, R.; Hall, I. R.

    2014-12-01

    Agulhas leakage of warm, salty water from the Indian Ocean to the South Atlantic is suggested to have altered Atlantic meridional overturning and climate in the North Atlantic. One way to assess such linkages with North Atlantic climate variability is to examine the past Agulhas hydrography via high-resolution marine records from the Agulhas Bank slope. Here we present one such hydrographic estimate from the Agulhas Bank slope in the Atlantic sector of the Agulhas Corridor using planktic foraminiferal (Globigerinoides ruber) δ18O and Mg/Ca-derived SST to estimate surface salinity. By focusing on the last 80,000 years this is the first quantitative fine-scale Agulhas leakage record that overlaps in time with the Greenland ice core record of abrupt climate changes in the North Atlantic region. Periods of enhanced Agulhas Corridor salinity occur at Northern Hemisphere cool periods (glacial termination and Heinrich meltwater events) and are followed by rapid northern hemisphere warming. We show that the timing of maximal salinity events in relation to periods of North Atlantic freshwater perturbation is consistent with the concept suggested by climate models that Agulhas salinity oscillations could provide buoyancy compensation for the Atlantic and potentially even trigger increased convective activity in the North Atlantic, thereby restoring Atlantic overturning circulation after relatively weak states.

  5. Climatic Concepts and Regions.

    ERIC Educational Resources Information Center

    Thomas, Paul F.

    Designed for students in grades 7 through 12, this teaching unit presents illustrative resource materials depicting concepts related to climate and geographic regions. Emphasis is on giving students an understanding of climatic elements and factors, not as isolated, disjointed entities, but as a dynamic interplay of forces having a very definite…

  6. Cenozoic climates: evidence from the North Atlantic

    SciTech Connect

    Berggren, W.A.

    1985-01-01

    Cenozoic biostratigraphy and climatology of the North Atlantic and adjacent land areas reflects the continuing fragmentation of Eurasia and concomitant changes on ocean-continent geometry. A latitudinal (zonal) Mesozoic circulation pattern evolved into a predominantly longitudinal (meridional) pattern during the Cenozoic in which the development of oceanic gateways and barriers gradually decreased the efficiency of poleward heat transfer resulting in the progressive climatic change which has taken place over the past 50 million years. Cenozoic distributional data from the North Atlantic and adjacent land areas will be reviewed from the following fields: a) terrestrial vertebrates and floras: b) marine calcareous microplankton and benthic foraminifera; c) other marine invertebrates. Available data suggests that the present climate in the northern hemisphere has resulted from a gradual, but inexorable, strengthening of latitudinal and vertical temperature gradients punctuated by several brief intervals of accelerated change. The absence of evidence for northern hemisphere polar glaciation prior to the late Neogene does not preclude seasonal cooling near the freezing point in post-Eocene time. Evidence for early Paleogene cold climates is not reflected in the fossil record.

  7. GLOBAL CHANGE RESEARCH NEWS #6: PUBLICATION OF FIRST REPORT FROM MID-ATLANTIC REGIONAL ASSESSMENT (MARA)

    EPA Science Inventory

    This research news edition announces the publication of the first report from the Mid-Atlantic Regional Assessment (MARA). The report is entitled, *Climate Change Impacts in the Mid-Atlantic Region -- A Workshop Report.* MARA is being conducted as part of the USGCRP First Nation...

  8. North Atlantic-Fennoscandian Holocene climate trends and mechanisms

    NASA Astrophysics Data System (ADS)

    Sejrup, Hans Petter; Seppä, Heikki; McKay, Nicholas P.; Kaufman, Darrell S.; Geirsdóttir, Áslaug; de Vernal, Anne; Renssen, Hans; Husum, Katrine; Jennings, Anne; Andrews, John T.

    2016-09-01

    To investigate the mechanisms behind Holocene regional climate trends from north of 58°N in the North Atlantic-Fennoscandian region Principal Component Analysis (PCA) was performed and a temperature anomaly stack produced from 81 proxy derived summer temperature time series from 74 sites. The PC results show distinctly different trends for near-surface versus surface temperatures, demonstrating the importance of handling these separately. The first PC of weighted sea surface summer temperature time series and continental time series explains 45 ± 8% of the variance, where the uncertainty is the standard deviation of the distribution of variance explained across the 1000 age-uncertain ensemble members. PC1 has a relatively uniform expression over the whole region, closely following the summer insolation at 65°N. The second PC explains 22 ± 4% of the variance and shows a non-uniform expression, with loadings in opposite directions in the northern and southeastern parts of the region. Comparing the PC time series with model runs and with the timing of the demise of the Laurentide Ice Sheet (LIS), suggest that this pattern reflects both topographic and albedo effects of the LIS as well as release of meltwater into the North Atlantic and Arctic Oceans. Comparing the stack of gridded records with published global stacks reveals an unusual Holocene temperature development in the North Atlantic-Fennoscandian region most likely resulting from the location relative to the decaying LIS.

  9. Modeling the impact of changes in Atlantic sea surface temperature on the climate of West Africa

    NASA Astrophysics Data System (ADS)

    Adeniyi, Mojisola O.

    2016-08-01

    This study assesses the impacts of warming/cooling of the Atlantic sea surface temperature (SST) on the climate of West Africa using Version 4.4 of Regional Climate Model (RegCM4.4) of International Center for Theoretical Physics, Trieste, Italy. The 1-2 K cooling and warming of the Atlantic SST both result in tripole temperature and precipitation change structure, having a northwest-southeast orientation over West Africa. Findings reveal that the responses of precipitation and temperature to the Atlantic SST cooling are opposite to those for the Atlantic SST warming and these responses intensify with increased warming/cooling of the Atlantic SST. The structure of the change in climate is attributed to the response of atmospheric/soil moisture gradient and orientation of orography in West Africa.

  10. The South Atlantic Anticyclone as a key player for the representation of the tropical Atlantic climate in coupled climate models

    NASA Astrophysics Data System (ADS)

    Cabos, William; Sein, Dmitry V.; Pinto, Joaquim G.; Fink, Andreas H.; Koldunov, Nikolay V.; Alvarez, Francisco; Izquierdo, Alfredo; Keenlyside, Noel; Jacob, Daniela

    2016-08-01

    The key role of the South Atlantic Anticyclone (SAA) on the seasonal cycle of the tropical Atlantic is investigated with a regionally coupled atmosphere-ocean model for two different coupled domains. Both domains include the equatorial Atlantic and a large portion of the northern tropical Atlantic, but one extends southward, and the other northwestward. The SAA is simulated as internal model variability in the former, and is prescribed as external forcing in the latter. In the first case, the model shows significant warm biases in sea surface temperature (SST) in the Angola-Benguela front zone. If the SAA is externally prescribed, these biases are substantially reduced. The biases are both of oceanic and atmospheric origin, and are influenced by ocean-atmosphere interactions in coupled runs. The strong SST austral summer biases are associated with a weaker SAA, which weakens the winds over the southeastern tropical Atlantic, deepens the thermocline and prevents the local coastal upwelling of colder water. The biases in the basins interior in this season could be related to the advection and eddy transport of the coastal warm anomalies. In winter, the deeper thermocline and atmospheric fluxes are probably the main biases sources. Biases in incoming solar radiation and thus cloudiness seem to be a secondary effect only observed in austral winter. We conclude that the external prescription of the SAA south of 20°S improves the simulation of the seasonal cycle over the tropical Atlantic, revealing the fundamental role of this anticyclone in shaping the climate over this region.

  11. Aerosol interactions with African/Atlantic climate dynamics

    NASA Astrophysics Data System (ADS)

    Hosseinpour, F.; Wilcox, E. M.

    2014-07-01

    Mechanistic relationships exist between variability of dust in the oceanic Saharan air layer (OSAL) and transient changes in the dynamics of Western Africa and the tropical Atlantic Ocean. This study provides evidence of possible interactions between dust in the OSAL region and African easterly jet-African easterly wave (AEJ-AEW) system in the climatology of boreal summer, when easterly wave activity peaks. Synoptic-scale changes in instability and precipitation in the African/Atlantic intertropical convergence zone are correlated with enhanced aerosol optical depth (AOD) in the OSAL region in response to anomalous 3D overturning circulations and upstream/downstream thermal anomalies at above and below the mean-AEJ level. Upstream and downstream anomalies are referred to the daily thermal/dynamical changes over the West African monsoon region and the Eastern Atlantic Ocean, respectively. Our hypothesis is that AOD in the OSAL is positively correlated with the downstream AEWs and negatively correlated with the upstream waves from climatological perspective. The similarity between the 3D pattern of thermal/dynamical anomalies correlated with dust outbreaks and those of AEWs provides a mechanism for dust radiative heating in the atmosphere to reinforce AEW activity. We proposed that the interactions of OSAL dust with regional climate mainly occur through coupling of dust with the AEWs.

  12. Northwest Regional Climate Assessment

    NASA Technical Reports Server (NTRS)

    Lipschultz, Fred

    2011-01-01

    Objectives are to establish a continuing, inclusive National process that: 1) synthesizes relevant science and information 2) increases understanding of what is known & not known 3) identifies information needs related to preparing for climate variability and change, and reducing climate impacts and vulnerability 4) evaluates progress of adaptation & mitigation activities 5) informs science priorities 6) builds assessment capacity in regions and sectors 7) builds understanding & skilled use of findings

  13. ASSOCIATIONS BETWEEN NAO VARIBILITY AND U.S. MID-ATLANTIC REGION HYDROCLIMATOLOGY

    EPA Science Inventory

    Variability in the climate of the US Mid-Atlantic Region is associated with larger scale variability in the El Nino-Southern Oscillation (ENSO), the Pacific North American (PNA) teleconnection pattern, and the North Atlantic Oscillation (NAO). Collectively, these three large-scal...

  14. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    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.

  15. Solar forcing synchronizes decadal North Atlantic climate variability

    PubMed Central

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-01-01

    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. PMID:26369503

  16. Middle Atlantic Bight Marine Ecosystem: A Regional Forecast Model Study

    NASA Astrophysics Data System (ADS)

    Kim, H.; Coles, V. J.; Garraffo, Z. D.

    2011-12-01

    Changes in basin scale climate patterns can drive changes in mesoscale physical oceanographic processes and subsequent alterations of ecosystem states. Climatic variability can be induced in the northeastern shelfbreak large marine ecosystem by climate oscillations, such as North Atlantic Oscillation, Atlantic Multidecadal Oscillation; and long-term trends, such as a warming pattern. Short term variability can be induced by changes in the water masses in the northern and southern boundaries, by Gulf Stream path and transport variations, and by local mesoscale and submesoscale features. A coupled bio-physical model (HYbrid Coordinate Ocean Model) is being used to forecast the evolution of the frontal and current systems of the shelf and Gulf Stream, and subsequent changes in thermal conditions and ecosystem structure over the Middle Atlantic Bight (MAB). This study aims to forecast the ocean state and nutrients in the MAB, and to investigate how cross-shelf exchanges of different water masses could affect nutrient budgets, primary and secondary production, and fish populations in coastal and shelf marine ecosystems. Preliminary results are shown for a regional MAB model nested to the global 1/12o HYCOM run at NOAA/NCEP/EMC using Naval Oceanographic Office (NAVO) daily initialization. Elements of this simulation are nutrient influx condition at the northern and southern boundaries through regression to ocean thermodynamic variables, and nutrient input at the river mouths.

  17. Mid-Atlantic Regional Wind Energy Institute

    SciTech Connect

    Courtney Lane

    2011-12-20

    As the Department of Energy stated in its 20% Wind Energy by 2030 report, there will need to be enhanced outreach efforts on a national, state, regional, and local level to communicate wind development opportunities, benefits and challenges to a diverse set of stakeholders. To help address this need, PennFuture was awarded funding to create the Mid-Atlantic Regional Wind Energy Institute to provide general education and outreach on wind energy development across Maryland, Virginia, Delaware, Pennsylvania and West Virginia. Over the course of the two-year grant period, PennFuture used its expertise on wind energy policy and development in Pennsylvania and expanded it to other states in the Mid-Atlantic region. PennFuture accomplished this through reaching out and establishing connections with policy makers, local environmental groups, health and economic development organizations, and educational institutions and wind energy developers throughout the Mid-Atlantic region. PennFuture conducted two regional wind educational forums that brought together wind industry representatives and public interest organizations from across the region to discuss and address wind development in the Mid-Atlantic region. PennFuture developed the agenda and speakers in collaboration with experts on the ground in each state to help determine the critical issue to wind energy in each location. The sessions focused on topics ranging from the basics of wind development; model ordinance and tax issues; anti-wind arguments and counter points; wildlife issues and coalition building. In addition to in-person events, PennFuture held three webinars on (1) Generating Jobs with Wind Energy; (2) Reviving American Manufacturing with Wind Power; and (3) Wind and Transmission. PennFuture also created a web page for the institute (http://www.midatlanticwind.org) that contains an online database of fact sheets, research reports, sample advocacy letters, top anti-wind claims and information on how to

  18. Northern tropical Atlantic climate since late Medieval times from Northern Caribbean coral geochemistry

    NASA Astrophysics Data System (ADS)

    Kilbourne, K. H.; Xu, Y.

    2015-12-01

    Paleoclimate reconstructions of different global climate modes over the last 1000 years provide the basis for testing the relative roles of forced and unforced variability climate system, which can help us improve projections of future climate change. The Medieval Climate Anomaly (MCA) has been characterized by a combination of persistent La Niña-like conditions, a positive North Atlantic Oscillation (+NAO), and increased Atlantic Meridional Overturning Circulation (AMOC). The northern tropical Atlantic is sensitive to each of these climate patterns, but not all of them have the same regional fingerprint in the modern northern tropical Atlantic. The relative influence of different processes related to these climate patterns can help us better understand regional responses to climate change. The regional response of the northern tropical Atlantic is important because the tropical Atlantic Ocean is a large source of heat and moisture to the global climate system that can feedback onto global climate patterns. This study presents new coral Sr/Ca and δ18O data from the northern tropical Atlantic (Anegada, British Virgin Islands). Comparison of the sub-fossil corals that grew during the 13th and 14th Centuries with modern coral geochemical data from this site indicates relatively cooler mean conditions with a decrease in the oxygen isotopic composition of the water consistent with lower salinities. Similar average annual cycles between modern and sub-fossil Sr/Ca indicate no change in seasonal temperature range, but a difference in the relative phasing of the δ18O seasonal cycles indicates that the fresher mean conditions may be due to a more northerly position of the regional salinity front. This localized response is consistent with some, but not all of the expected regional responses to a La Niña-like state, a +NAO state, and increased AMOC. Understanding these differences can provide insight into the relative importance of advection versus surface fluxes for

  19. Cyclic growth in Atlantic region continental crust

    NASA Technical Reports Server (NTRS)

    Goodwin, A. M.

    1986-01-01

    Atlantic region continental crust evolved in successive stages under the influence of regular, approximately 400 Ma-long tectonic cycles. Data point to a variety of operative tectonic processes ranging from widespread ocean floor consumption (Wilson cycle) to entirely ensialic (Ampferer-style subduction or simple crustal attenuation-compression). Different processes may have operated concurrently in some or different belts. Resolving this remains the major challenge.

  20. Synchronous response of marine plankton ecosystems to climate in the Northeast Atlantic and the North Sea

    NASA Astrophysics Data System (ADS)

    Goberville, Eric; Beaugrand, Gregory; Edwards, Martin

    2014-01-01

    Over the last few decades, global warming has accelerated both the rate and magnitude of changes observed in many functional units of the Earth System. In this context, plankton are sentinel organisms because they are sensitive to subtle levels of changes in temperature and might help in identifying the current effects of climate change on pelagic ecosystems. In this paper, we performed a comparative approach in two regions of the North Atlantic (i.e. the Northeast Atlantic and the North Sea) to explore the relationships between changes in marine plankton, the regional physico-chemical environment and large-scale hydro-climatic forcing using four key indices: the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), the East Atlantic (EA) pattern and Northern Hemisphere Temperature (NHT) anomalies. Our analyses suggest that long-term changes in the states of the two ecosystems were synchronous and correlated to the same large-scale hydro-climatic variables: NHT anomalies, the AMO and to a lesser extent the EA pattern. No significant correlation was found between long-term ecosystem modifications and the state of the NAO. Our results suggest that the effect of climate on these ecosystems has mainly occurred in both regions through the modulation of the thermal regime.

  1. Carbon uptake sensitivity of the North Atlantic to climate change: A model study with the Bergen Climate Model

    NASA Astrophysics Data System (ADS)

    Goris, Nadine; Heinze, Christoph; Tjiputra, Jerry; Schwinger, Jörg

    2015-04-01

    The efficiency of the world's oceans to take up carbon is expected to decrease with ongoing climate change, thereby increasing the atmospheric burden of carbon. Here, the North Atlantic is a region of special interest as it is one of the most important oceanic carbon sinks, featuring an exceptionally high column inventory of anthropogenic CO2. Several model studies have identified the carbon uptake of the North Atlantic as highly sensitive to climate change, but these studies are mostly global studies and are not concerned with a detailed attribution of the underlying mechanisms and their regional differences within the North Atlantic. Yet, quantifying the climate change induced CO2-uptake variability in the North Atlantic and identifying its main drivers is of high relevance for improving climate projections. In order to assess and understand the climate sensitivity of the CO2 uptake of the North Atlantic, we investigate the differences between two simulations (denoted as simulation COU and simulation BGC) carried out with the Bergen Earth System Model (BCM-C). While simulation COU features rising atmospheric CO2 concentrations (based on observed records for 1850-1999 and the IPCC SRES-A2 scenario for 2000-2099) for radiation code and carbon fluxes, simulation BGC uses rising atmospheric concentrations only for the calculation of the carbon fluxes. The differences between those simulations identify climate induced changes. Our analysis confirms the important role of the North Atlantic for carbon uptake and demonstrates that this region is most sensitive to climate change (in comparison to other oceanic regions as defined in Tjiputra et al., 2010). We furthermore identify substantially different responses to climate change in different parts of the North Atlantic. Based on these differing responses, we divide the North Atlantic into 3 regions, namely the subpolar gyre region (SPG), the high latitude region (HL) and the rest of the North Atlantic (rNAT*, covering

  2. Climate and ecosystem linkages explain widespread declines in North American Atlantic salmon populations.

    PubMed

    Mills, Katherine E; Pershing, Andrew J; Sheehan, Timothy F; Mountain, David

    2013-10-01

    North American Atlantic salmon (Salmo salar) populations experienced substantial declines in the early 1990s, and many populations have persisted at low abundances in recent years. Abundance and productivity declined in a coherent manner across major regions of North America, and this coherence points toward a potential shift in marine survivorship, rather than local, river-specific factors. The major declines in Atlantic salmon populations occurred against a backdrop of physical and biological shifts in Northwest Atlantic ecosystems. Analyses of changes in climate, physical, and lower trophic level biological factors provide substantial evidence that climate conditions directly and indirectly influence the abundance and productivity of North American Atlantic salmon populations. A major decline in salmon abundance after 1990 was preceded by a series of changes across multiple levels of the ecosystem, and a subsequent population change in 1997, primarily related to salmon productivity, followed an unusually low NAO event. Pairwise correlations further demonstrate that climate and physical conditions are associated with changes in plankton communities and prey availability, which are ultimately linked to Atlantic salmon populations. Results suggest that poor trophic conditions, likely due to climate-driven environmental factors, and warmer ocean temperatures throughout their marine habitat area are constraining the productivity and recovery of North American Atlantic salmon populations.

  3. Do regional climate models represent regional climate?

    NASA Astrophysics Data System (ADS)

    Maraun, Douglas; Widmann, Martin

    2014-05-01

    When using climate change scenarios - either from global climate models or further downscaled - to assess localised real world impacts, one has to ensure that the local simulation indeed correctly represents the real world local climate. Representativeness has so far mainly been discussed as a scale issue: simulated meteorological variables in general represent grid box averages, whereas real weather is often expressed by means of point values. As a result, in particular simulated extreme values are not directly comparable with observed local extreme values. Here we argue that the issue of representativeness is more general. To illustrate this point, assume the following situations: first, the (GCM or RCM) simulated large scale weather, e.g., the mid-latitude storm track, might be systematically distorted compared to observed weather. If such a distortion at the synoptic scale is strong, the simulated local climate might be completely different from the observed. Second, the orography even of high resolution RCMs is only a coarse model of true orography. In particular in mountain ranges the simulated mesoscale flow might therefore considerably deviate from the observed flow, leading to systematically displaced local weather. In both cases, the simulated local climate does not represent observed local climate. Thus, representativeness also encompasses representing a particular location. We propose to measure this aspect of representativeness for RCMs driven with perfect boundary conditions as the correlation between observations and simulations at the inter-annual scale. In doing so, random variability generated by the RCMs is largely averaged out. As an example, we assess how well KNMIs RACMO2 RCM at 25km horizontal resolution represents winter precipitation in the gridded E-OBS data set over the European domain. At a chosen grid box, RCM precipitation might not be representative of observed precipitation, in particular in the rain shadow of major moutain ranges

  4. Surface temperatures of the Mid-Pliocene North Atlantic Ocean: Implications for future climate

    USGS Publications Warehouse

    Dowsett, Harry J.; Chandler, Mark A.; Robinson, Marci M.

    2009-01-01

    The Mid-Pliocene is the most recent interval in the Earth's history to have experienced warming of the magnitude predicted for the second half of the twenty-first century and is, therefore, a possible analogue for future climate conditions. With continents basically in their current positions and atmospheric CO2 similar to early twenty-first century values, the cause of Mid-Pliocene warmth remains elusive. Understanding the behaviour of the North Atlantic Ocean during the Mid-Pliocene is integral to evaluating future climate scenarios owing to its role in deep water formation and its sensitivity to climate change. Under the framework of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) sea surface reconstruction, we synthesize Mid-Pliocene North Atlantic studies by PRISM members and others, describing each region of the North Atlantic in terms of palaeoceanography. We then relate Mid-Pliocene sea surface conditions to expectations of future warming. The results of the data and climate model comparisons suggest that the North Atlantic is more sensitive to climate change than is suggested by climate model simulations, raising the concern that estimates of future climate change are conservative.

  5. Sub-decadal North Atlantic Oscillation variability in observations and the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Reintges, Annika; Latif, Mojib; Park, Wonsun

    2016-07-01

    The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability in the North Atlantic sector. The corresponding index varies on a wide range of timescales, from days and months to decades and beyond. Sub-decadal NAO variability has been well documented, but the underlying mechanism is still under discussion. Other indices of North Atlantic sector climate variability such as indices of sea surface and surface air temperature or Arctic sea ice extent also exhibit pronounced sub-decadal variability. Here, we use sea surface temperature and sea level pressure observations, and the Kiel Climate Model to investigate the dynamics of the sub-decadal NAO variability. The sub-decadal NAO variability is suggested to originate from dynamical large-scale air-sea interactions. The adjustment of the Atlantic Meridional Overturning Circulation to previous surface heat flux variability provides the memory of the coupled mode. The results stress the role of coupled feedbacks in generating sub-decadal North Atlantic sector climate variability, which is important to multiyear climate predictability in that region.

  6. Patagonian and southern South Atlantic view of Holocene climate

    NASA Astrophysics Data System (ADS)

    Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Denton, G. H.; Anderson, R. F.; Vandergoes, M. J.; Finkel, R. C.; Schwartz, R.; Travis, S. G.; Garcia, J. L.; Martini, M. A.; Nielsen, S. H. H.

    2016-06-01

    We present a comprehensive 10Be chronology for Holocene moraines in the Lago Argentino basin, on the east side of the South Patagonian Icefield. We focus on three different areas, where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change. The 10Be dated records are from the Lago Pearson, Herminita Península-Brazo Upsala, and Lago Frías areas, which span a distance of almost 100 km adjacent to the modern Icefield. New 10Be ages show that expanded glaciers and moraine building events occurred at least at 6120 ± 390 (n = 13), 4450 ± 220 (n = 7), 1450 or 1410 ± 110 (n = 18), 360 ± 30 (n = 5), and 240 ± 20 (n = 8) years ago. Furthermore, other less well-dated glacier expansions of the Upsala Glacier occurred between 1400 and ∼1000 and ∼2300 and ∼2000 years ago. The most extensive glaciers occurred over the interval from ∼6100 to ∼4500 years ago, and their margins over the last ∼600 years were well within and lower than those in the middle Holocene. The 10Be ages agree with 14C-limiting data for the glacier histories in this area. We then link southern South American, adjacent South Atlantic, and other Southern Hemisphere records to elucidate broader regional patterns of climate and their possible causes. In the early Holocene, a far southward position of the westerly winds fostered warmth, small Patagonian glaciers, and reduced sea ice coverage over the South Atlantic. Although we infer a pronounced southward displacement of the westerlies during the early Holocene, these conditions did not occur throughout the southern mid-high latitudes, an important exception being over the southwest Pacific sector. Subsequently, a northward locus and/or expansion of the winds over the Patagonia-South Atlantic sector promoted the largest glaciers between ∼6100 and ∼4500 years ago and greatest sea ice coverage. Over the last few millennia, the South Patagonian Icefield has experienced

  7. Surface Temperature Trends in the Arctic Atlantic Region Over the Last 2,000 Years

    NASA Astrophysics Data System (ADS)

    Korhola, A.; Hanhijarvi, S.; Tingley, M.

    2013-12-01

    We introduce a new reconstruction method that uses the ordering of all pairs of proxy observations within each record to arrive at a consensus time series that best agrees with all proxy records. By considering only pairwise comparisons, this method, which we call PaiCo, facilitates the inclusion of records with differing temporal resolutions, and relaxes the assumption of linearity to the more general assumption of a monotonically increasing relationship between each proxy series and the target climate variable. We apply PaiCo to a newly assembled collection of high-quality proxy data to reconstruct the mean temperature of the Northernmost Atlantic region, which we call Arctic Atlantic, over the last 2,000 years. The Arctic Atlantic is a dynamically important region known to feature substantial temperature variability over recent millennia, and PaiCo allows for a more thorough investigation of the Arctic Atlantic regional climate as we include a diverse array of terrestrial and marine proxies with annual to multidecadal temporal resolutions. Comparisons of the PaiCo reconstruction to recent reconstructions covering larger areas indicate greater climatic variability in the Arctic Atlantic than for the Arctic as a whole. The Arctic Atlantic reconstruction features temperatures during the Roman Warm Period and Medieval Climate Anomaly that are comparable or even warmer than those of the twentieth century, and coldest temperatures in the middle of the nineteenth century, just prior to the onset of the recent warming trend.

  8. Intensified impact of tropical Atlantic SST on the western North Pacific summer climate under a weakened Atlantic thermohaline circulation

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Lee, June-Yi; Lu, Riyu; Dong, Buwen; Ha, Kyung-Ja

    2015-10-01

    The tropical North Atlantic (TNA) sea surface temperature (SST) has been identified as one of regulators on the boreal summer climate over the western North Pacific (WNP), in addition to SSTs in the tropical Pacific and Indian Oceans. The major physical process proposed is that the TNA warming induces a pair of cyclonic circulation anomaly over the eastern Pacific and negative precipitation anomalies over the eastern to central tropical Pacific, which in turn lead to an anticyclonic circulation anomaly over the western to central North Pacific. This study further demonstrates that the modulation of the TNA warming to the WNP summer climate anomaly tends to be intensified under background of the weakened Atlantic thermohaline circulation (THC) by using a water-hosing experiment. The results suggest that the weakened THC induces a decrease in thermocline depth over the TNA region, resulting in the enhanced sensitivity of SST variability to wind anomalies and thus intensification of the interannual variation of TNA SST. Under the weakened THC, the atmospheric responses to the TNA warming are westward shifted, enhancing the anticyclonic circulation and negative precipitation anomaly over the WNP. This study supports the recent finding that the negative phase of the Atlantic multidecadal oscillation after the late 1960s has been favourable for the strengthening of the connection between TNA SST variability and WNP summer climate and has important implications for seasonal prediction and future projection of the WNP summer climate.

  9. Glacier response to North Atlantic climate variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Balascio, N. L.; D'Andrea, W. J.; Bradley, R. S.

    2015-12-01

    Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of

  10. Waveform Tomography of the North Atlantic Region

    NASA Astrophysics Data System (ADS)

    Celli, Nicolas Luca; Lebedev, Sergei; Schaeffer, Andrew; Gaina, Carmen

    2016-04-01

    The enormous volumes of newly available, broadband seismic data and the continuing development of waveform tomography techniques present us with an opportunity to resolve the structure of North Atlantic at a new level of detail. Dynamics of the North Atlantic Ridge and the Iceland Hotspot, evolution of the passive margins on both sides of the ocean, and the nature of the upper-mantle flow beneath the region are some of the important fundamental problems that we can make progress on using new, more detailed and accurate models of seismic structure and anisotropy within the lithosphere and underlying mantle. We assemble a very large waveform dataset including all publicly available data in the region, from both permanent and temporary seismic networks and experiments conducted in Northern and Western Europe, Iceland, Canada, USA, Greenland and Russia. The tomographic model is constrained by vertical-component waveform fits, computed using the Automated Multimode Inversion of surface, S and multiple S waves. Each seismogram fit provides a set of linear equations describing 1D average velocity perturbations with respect to a 3D reference velocity model within an approximate sensitivity region between the source and the receiver. The equations are then combined into a large linear system and jointly inverted for a model of shear- and compressional-wave speeds and azimuthal anisotropy within the lithosphere and underlying mantle. The isotropic-average shear speeds reflect the temperature and composition at depth, offering important new information on both regional- and basin-scale lithospheric structure and evolution. Azimuthal anisotropy provides evidence on the past and present deformation in the lithosphere and asthenosphere beneath the region, which can be interpreted together with other evidence from geological and geophysical data and recent plate kinematic models.

  11. Marine and terrestrial biotic response to climate variability across the Paleocene-Eocene boundary in the Mid-Atlantic region, USA

    NASA Astrophysics Data System (ADS)

    Willard, D. A.; Aleman, W.; Edwards, L. E.; Farmer, J. R.; Self-Trail, J.

    2009-12-01

    Late Paleocene to early Eocene continental margin sediments provide an opportunity to examine rates and patterns of change in terrestrial and marine ecoystems during an interval of rapid global warming and increasing atmospheric carbon concentrations. We present Paleocene-Eocene thermal maximum (PETM) multiproxy data from a core obtained in 2007 from South Dover Bridge, Talbot County, Maryland. In it, we identified an apparently conformable Paleocene-Eocene contact at the Aquia Formation/Marlboro Clay boundary based on nannofossil, dinocyst, and pollen assemblages. A CaCO3 dissolution zone persists through the lower 91 cm of the Marlboro Clay. Terrestrial palynomorph concentration increases sharply at the base (<10 cm) of the dissolution zone, which is characterized by dominance (40-50%) of fern spores and distinctive palynofacies. Specimens of the dinocyst marker species Apectodinium augustum are present but not abundant. Planktic and benthic foraminifers and nannofossils are absent in the dissolution zone, except for distinct and reduced assemblages at 54 cm above the basal Marlboro contact. Marlboro Clay sediment above the dissolution zone contains a unique nannofossil assemblage that is restricted to this unit and is indicative of the PETM both regionally and globally. The re-occurrence of calcareous nannofossil species in the upper Marlboro that disappeared at the base of the dissolution zone suggests a return to normal oceanic conditions. Comparison of multi-proxy data from this high-sedimentation site with other PETM records is important to improve our understanding of the pattern and timing of vegetation, phytoplankton, and marine responses to climate variability associated with the PETM, both regionally and globally.

  12. Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks.

    PubMed

    Williams, Ross H; McGee, David; Kinsley, Christopher W; Ridley, David A; Hu, Shineng; Fedorov, Alexey; Tal, Irit; Murray, Richard W; deMenocal, Peter B

    2016-11-01

    Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust's radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust's radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa.

  13. Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks

    PubMed Central

    Williams, Ross H.; McGee, David; Kinsley, Christopher W.; Ridley, David A.; Hu, Shineng; Fedorov, Alexey; Tal, Irit; Murray, Richard W.; deMenocal, Peter B.

    2016-01-01

    Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust’s radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust’s radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa. PMID:28138515

  14. North Atlantic forcing of tropical Indian Ocean climate.

    PubMed

    Mohtadi, Mahyar; Prange, Matthias; Oppo, Delia W; De Pol-Holz, Ricardo; Merkel, Ute; Zhang, Xiao; Steinke, Stephan; Lückge, Andreas

    2014-05-01

    The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.

  15. Ocean impact on decadal Atlantic climate variability revealed by sea-level observations

    NASA Astrophysics Data System (ADS)

    McCarthy, Gerard D.; Haigh, Ivan D.; Hirschi, Joël J.-M.; Grist, Jeremy P.; Smeed, David A.

    2015-05-01

    Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

  16. Ocean impact on decadal Atlantic climate variability revealed by sea-level observations.

    PubMed

    McCarthy, Gerard D; Haigh, Ivan D; Hirschi, Joël J-M; Grist, Jeremy P; Smeed, David A

    2015-05-28

    Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

  17. 77 FR 35357 - Atlantic Highly Migratory Species; Commercial Atlantic Region Non-Sandbar Large Coastal Shark...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ...; Commercial Atlantic Region Non-Sandbar Large Coastal Shark Fishery Opening Date AGENCY: National Marine...-sandbar large coastal shark fishery. This action is necessary to inform fishermen and dealers about the fishery opening date. DATES: The commercial Atlantic region non-sandbar large coastal shark fishery...

  18. CARICOF - The Caribbean Regional Climate Outlook Forum

    NASA Astrophysics Data System (ADS)

    Van Meerbeeck, Cedric

    2013-04-01

    Regional Climate Outlook Forums (RCOFs) are viewed as a critical building block in the Global Framework for Climate Services (GFCS) of the World Meteorological Organization (WMO). The GFCS seeks to extend RCOFs to all vulnerable regions of the world such as the Caribbean, of which the entire population is exposed to water- and heat-related natural hazards. An RCOF is initially intended to identify gaps in information and technical capability; facilitate research cooperation and data exchange within and between regions, and improve coordination within the climate forecasting community. A focus is given on variations in climate conditions on a seasonal timescale. In this view, the relevance of a Caribbean RCOF (CARICOF) is the following: while the seasonality of the climate in the Caribbean has been well documented, major gaps in knowledge exist in terms of the drivers in the shifts of amplitude and phase of seasons (as evidenced from the worst region-wide drought period in recent history during 2009-2010). To address those gaps, CARICOF has brought together National Weather Services (NWSs) from 18 territories under the coordination of the Caribbean Institute for Meteorology and Hydrology (CIMH), to produce region-wide, consensus, seasonal climate outlooks since March 2012. These outlooks include tercile rainfall forecasts, sea and air surface temperature forecasts as well as the likely evolution of the drivers of seasonal climate variability in the region, being amongst others the El Niño Southern Oscillation or tropical Atlantic and Caribbean Sea temperatures. Forecasts for both the national-scale forecasts made by the NWSs and CIMH's regional-scale forecast amalgamate output from several forecasting tools. These currently include: (1) statistical models such as Canonical Correlation Analysis run with the Climate Predictability Tool, providing tercile rainfall forecasts at weather station scale; (2) a global outlooks published by the WMO appointed Global Producing

  19. INDICATORS OF CHANGE IN THE MID-ATLANTIC WATERSHEDS AND CONSEQUENCES OF CLIMATE IN UPPER CHESAPEAKE BAY

    EPA Science Inventory

    The rate of change in Northern Hemisphere atmospheric temperature in the past century relative to the preceding millennium strongly suggests that we are in a period of rapid global climate change. The mid-Atlantic region is quite sensitive to larger scale climate variation, which...

  20. The East Atlantic - West Russia Teleconnection in the North Atlantic: Climate Impact and Relation to Rossby Wave Propagation

    NASA Technical Reports Server (NTRS)

    Lim, Young-Kwon

    2014-01-01

    Large-scale winter teleconnection of the East Atlantic - West Russia (EA-WR) over the Atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence. A rotated empirical orthogonal function (REOF) analysis of the upper-tropospheric monthly height field captures successfully the EA-WR pattern and its interannual variation, with the North Atlantic Oscillation as the first mode. EA-WRs climate impact extends from eastern North America to Eurasia. The positive (negative) EA-WR produces positive (negative) temperature anomalies over the eastern US, western Europe and Russia east of Caspian Sea, with negative (positive) anomalies over eastern Canada, eastern Europe including Ural Mountains and the Middle East. These anomalies are largely explained by lower-tropospheric temperature advections. Positive (negative) precipitation anomalies are found over the mid-latitude Atlantic and central Russia around 60E, where lower-level cyclonic (anticyclonic) circulation anomaly is dominant. The eastern Canada and the western Europe are characterized by negative (positive) precipitation anomalies.The EA-WR is found to be closely associated with Rossby wave propagation. Wave activity fluxes show that it is strongly tied to large-scale stationary waves. Furthermore, a stationary wave model (SWM) forced with vorticity transients in the mid-latitude Atlantic (approximately 40N) or diabatic heat source over the subtropical Atlantic near the Caribbean Sea produces well-organized EA-WR-like wave patterns, respectively. Sensitivity tests with the SWM indicate improvement in the simulation of the EA-WR when the mean state is modified to have a positive NAO component that enhances upper-level westerlies between 40-60N.

  1. Salt transport in the Subpolar Gyre amplifies North Atlantic climate variability

    NASA Astrophysics Data System (ADS)

    Born, Andreas; Stocker, Thomas F.; Britt Sandø, Anne

    2016-04-01

    Transport of salt in the Irminger Current, the northern branch of the Atlantic Subpolar Gyre coupling the eastern and western subpolar North Atlantic, plays an important role for climate variability across a wide range of time scales. High-resolution ocean modeling and observations indicate that salinities in the eastern subpolar North Atlantic decrease with enhanced circulation of the North Atlantic subpolar gyre. This has led to the perception that a stronger SPG also transports less salt westward, which would weaken deep convection in the Labrador Sea and thus the gyre itself. In this study, we analyze a regional ocean model and a comprehensive global coupled climate model, and show that a stronger SPG transports more salt in the Irminger Current irrespective of lower salinities in its source region. The additional salt converges in the Labrador Sea and the Irminger Basin by eddy transports, increases surface salinity in the western SPG, and favors more intense deep convection. This is part of a positive feedback mechanism with large implications for climate variability and predictability.

  2. Collaborative Project: Understanding Climate Model Biases in Tropical Atlantic and Their Impact on Simulations of Extreme Climate Events

    SciTech Connect

    Chang, Ping

    2016-01-04

    Recent studies have revealed that among all the tropical oceans, the tropical Atlantic has experienced the most pronounced warming trend over the 20th century. Many extreme climate events affecting the U.S., such as hurricanes, severe precipitation and drought events, are influenced by conditions in the Gulf of Mexico and the Atlantic Ocean. It is therefore imperative to have accurate simulations of the climatic mean and variability in the Atlantic region to be able to make credible projections of future climate change affecting the U.S. and other countries adjoining the Atlantic Ocean. Unfortunately, almost all global climate models exhibit large biases in their simulations of tropical Atlantic climate. The atmospheric convection simulation errors in the Amazon region and the associated errors in the trade wind simulations are hypothesized to be a leading cause of the tropical Atlantic biases in climate models. As global climate models have resolutions that are too coarse to resolve some of the atmospheric and oceanic processes responsible for the model biases, we propose to use a high-resolution coupled regional climate model (CRCM) framework to address the tropical bias issue. We propose to combine the expertise in tropical coupled atmosphere-ocean modeling at Texas A&M University (TAMU) and the coupled land-atmosphere modeling expertise at Pacific Northwest National Laboratory (PNNL) to develop a comprehensive CRCM for the Atlantic sector within a general and flexible modeling framework. The atmospheric component of the CRCM will be the NCAR WRF model and the oceanic component will be the Rutgers/UCLA ROMS. For the land component, we will use CLM modified at PNNL to include more detailed representations of vegetation and soil hydrology processes. The combined TAMU-PNNL CRCM model will be used to simulate the Atlantic climate, and the associated land-atmosphere-ocean interactions at a horizontal resolution of 9 km or finer. A particular focus of the model

  3. North Atlantic overturning and climate response to meltwater forcing during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Muschitiello, Francesco; Dokken, Trond; Väliranta, Minna; Björck, Svante; Davies, Siwan; Luoto, Tomi; Schenk, Frederik; Smittenberg, Rienk; Reimer, Paula; Wohlfarth, Barbara

    2016-04-01

    The last deglaciation (˜18-11 kyr BP) is an important analog to investigate the response of the Atlantic Meridional Overturning Circulation (AMOC) to future ice-sheet melting and its impact on regional climate change. In this study we present synchronised terrestrial and marine proxy records that provide insight into freshwater run-off and climate variability in the eastern North Atlantic during the last deglaciation. The reconstructions show that atmospheric circulation rather than freshwater forcing primarily controls the stability of the AMOC. However, catastrophic meltwater drainage from the Scandinavian continent may have solicited complex feedbacks necessary to account for the rapid large-scale hydro-climate shifts and the major weakening of the overturning circulation system at the onset of the Younger Dryas stadial.

  4. Tropical Atlantic climate response to different freshwater input in high latitudes with an ocean-only general circulation model

    NASA Astrophysics Data System (ADS)

    Men, Guang; Wan, Xiuquan; Liu, Zedong

    2016-10-01

    Tropical Atlantic climate change is relevant to the variation of Atlantic meridional overturning circulation (AMOC) through different physical processes. Previous coupled climate model simulation suggested a dipole-like SST structure cooling over the North Atlantic and warming over the South Tropical Atlantic in response to the slowdown of the AMOC. Using an ocean-only global ocean model here, an attempt was made to separate the total influence of various AMOC change scenarios into an oceanic-induced component and an atmospheric-induced component. In contrast with previous freshwater-hosing experiments with coupled climate models, the ocean-only modeling presented here shows a surface warming in the whole tropical Atlantic region and the oceanic-induced processes may play an important role in the SST change in the equatorial south Atlantic. Our result shows that the warming is partly governed by oceanic process through the mechanism of oceanic gateway change, which operates in the regime where freshwater forcing is strong, exceeding 0.3 Sv. Strong AMOC change is required for the gateway mechanism to work in our model because only when the AMOC is sufficiently weak, the North Brazil Undercurrent can flow equatorward, carrying warm and salty north Atlantic subtropical gyre water into the equatorial zone. This threshold is likely to be model-dependent. An improved understanding of these issues may have help with abrupt climate change prediction later.

  5. The Impact of North-South Shifts in the Sahel on North Atlantic Climate

    NASA Astrophysics Data System (ADS)

    Murphy, L.; Clement, A. C.; Mahowald, N. M.; Albani, S.; Swart, P. K.; Arienzo, M. M.

    2013-12-01

    Cool periods in the North Atlantic have been linked to hydrological changes over the Sahel region. It has been postulated that the Sahara-Sahel border shifted southwards during the last Heinrich event, which resulted in the semi-arid Sahel becoming more arid. This would drive changes in dust emission rates over North Africa. In fact proxy data indicates North Africa was dustier during the last Heinrich event than during the LGM. Recent analysis of CMIP5 models suggests the Western Sahel may become drier later this century. This may be analogous to past changes that have occurred in this region. Here we examine the implications of a southward shift in the Sahara-Sahel border in the Community Earth System Model version 1 (CESM1). Imposed changes in soil erodibility over the Sahel region results in greater dust emission rates and transport across the tropical Atlantic. Greater dust loading cools local sea surface temperatures and may have implications on the Atlantic Meridional Overturning Circulation. Our idealized runs can be used to understand how changes in dust forced climate change during the past as well as how potential future hydrological changes over the western Sahel can impact Atlantic climate.

  6. Effects of Atlantic warm pool variability over climate of South America tropical transition zone

    NASA Astrophysics Data System (ADS)

    Ricaurte Villota, Constanza; Romero-Rodríguez, Deisy; Andrés Ordoñez-Zuñiga, Silvio; Murcia-Riaño, Magnolia; Coca-Domínguez, Oswaldo

    2016-04-01

    Colombia is located in the northwestern corner of South America in a climatically complex region due to the influence processes modulators of climate both the Pacific and Atlantic region, becoming in a transition zone between phenomena of northern and southern hemisphere. Variations in the climatic conditions of this region, especially rainfall, have been attributed to the influence of the El Nino Southern Oscillation (ENSO), but little is known about the interaction within Atlantic Ocean and specifically Caribbean Sea with the environmental conditions of this region. In this work We studied the influence of the Atlantic Warm Pool (AWP) on the Colombian Caribbean (CC) climate using data of Sea Surface Temperature (SST) between 1900 - 2014 from ERSST V4, compared with in situ data SIMAC (National System for Coral Reef Monitoring in Colombia - INVEMAR), rainfall between 1953-2013 of meteorological stations located at main airports in the Colombian Caribbean zone, administered by IDEAM, and winds data between 2003 - 2014 from WindSat sensor. The parameters analyzed showed spatial differences throughout the study area. SST anomalies, representing the variability of the AWP, showed to be associated with Multidecadal Atlantic Oscillation (AMO) and with the index of sea surface temperature of the North-tropical Atlantic (NTA), the variations was on 3 to 5 years on the ENSO scale and of approximately 11 years possibly related to solar cycles. Rainfall anomalies in the central and northern CC respond to changes in SST, while in the south zone these are not fully engage and show a high relationship with the ENSO. Finally, the winds also respond to changes in SST and showed a signal approximately 90 days possibly related to the Madden-Julian Oscillation, whose intensity depends on the CC region being analyzed. The results confirm that region is a transition zone in which operate several forcing, the variability of climate conditions is difficult to attribute only one, as ENSO

  7. The Relationship between Atlantic Overturning and Climate in the Pleistocene

    NASA Astrophysics Data System (ADS)

    Howe, J. N. W.; Piotrowski, A. M.

    2015-12-01

    Changes in Atlantic Meridional Overturning Circulation play an important role in modulating global climate by controlling northward heat transport in the surface ocean and carbon storage in the deep ocean. We present a new high resolution 1.2 Myr record of neodymium isotopes (ɛNd) - a proxy for water mass mixing - measured on foraminifera and fish debris from site ODP 929 [6.0°N, 43.7°W, 4356 m] on the Ceara Rise in the western equatorial Atlantic Ocean. This record reveals a fundamental step-change in the nature of glacial Atlantic overturning across the Mid-Pleistocene Transition as well as providing new insight into the relationship between ocean circulation and greenhouse gas forcing during the period known as the "lukewarm" interglacials.Comparison with benthic foraminiferal carbon isotopes from the same core reveals periods of significant decoupling between ɛNd and δ13C, demonstrating that deep Atlantic water mass mixing proportions and nutrient chemistry can vary independently of one another. In contrast, comparison of the ɛNd record with benthic foraminiferal oxygen isotopes reveals a tight coupling, exhibiting the control of Northern Hemisphere climate on both ice volume and Atlantic overturning. The high resolution of the records allows cross spectral analysis of the phasing between authigenic ɛNd and both benthic foraminiferal δ13C and δ18O. This reveals that the different proxy records are coherent at time periods of 100-, 40- and 23-kyr which correlate with orbital forcing. However, the changes in each variable at these periods are not always in phase, indicating that the proxies exhibit different temporal responses to climatic forcings.

  8. Abrupt cooling over the North Atlantic in modern climate models

    PubMed Central

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-01-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy. PMID:28198383

  9. Abrupt cooling over the North Atlantic in modern climate models.

    PubMed

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-02-15

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy.

  10. Abrupt cooling over the North Atlantic in modern climate models

    NASA Astrophysics Data System (ADS)

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-02-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy.

  11. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Lynch-Stieglitz, Jean

    2017-01-01

    Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

  12. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change.

    PubMed

    Lynch-Stieglitz, Jean

    2017-01-03

    Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

  13. Pleistocene climates in the atlantic and pacific oceans: a comparison based on deep-sea sediments.

    PubMed

    Ericson, D B; Wollin, G

    1970-03-13

    Comparison of Pleistocene climatic records defined by variations in abundance of planktonic Foraminifera in three cores from the southeastern Pacific with similar records in cores from the Atlantic suggests that times of warm surface water in this region of the Pacific were at least partly synchronous with times of cool water in the Altantic. This conclusion opposes the Milankovitch theory of the causation of ice ages, but it harmonizes with a modified form of Simpson's hypothesis.

  14. The Reduced Effectiveness of Protected Areas under Climate Change Threatens Atlantic Forest Tiger Moths

    PubMed Central

    Ferro, Viviane G.; Lemes, Priscila; Melo, Adriano S.; Loyola, Rafael

    2014-01-01

    Climate change leads to species' range shifts, which may end up reducing the effectiveness of protected areas. These deleterious changes in biodiversity may become amplified if they include functionally important species, such as herbivores or pollinators. We evaluated how effective protected areas in the Brazilian Atlantic Forest are in maintaining the diversity of tiger moths (Arctiinae) under climate change. Specifically, we assessed whether protected areas will gain or lose species under climate change and mapped their locations in the Atlantic Forest, in order to assess potential spatial patterns of protected areas that will gain or lose species richness. Comparisons were completed using modeled species occurrence data based on the current and projected climate in 2080. We also built a null model for random allocation of protected areas to identify where reductions in species richness will be more severe than expected. We employed several modern techniques for modeling species' distributions and summarized results using ensembles of models. Our models indicate areas of high species richness in the central and southern regions of the Atlantic Forest both for now and the future. However, we estimate that in 2080 these regions should become climatically unsuitable, decreasing the species' distribution area. Around 4% of species were predicted to become extinct, some of them being endemic to the biome. Estimates of species turnover from current to future climate tended to be high, but these findings are dependent on modeling methods. Our most important results show that only a few protected areas in the southern region of the biome would gain species. Protected areas in semideciduous forests in the western region of the biome would lose more species than expected by the null model employed. Hence, current protected areas are worse off, than just randomly selected areas, at protecting species in the future. PMID:25229422

  15. The reduced effectiveness of protected areas under climate change threatens Atlantic forest tiger moths.

    PubMed

    Ferro, Viviane G; Lemes, Priscila; Melo, Adriano S; Loyola, Rafael

    2014-01-01

    Climate change leads to species' range shifts, which may end up reducing the effectiveness of protected areas. These deleterious changes in biodiversity may become amplified if they include functionally important species, such as herbivores or pollinators. We evaluated how effective protected areas in the Brazilian Atlantic Forest are in maintaining the diversity of tiger moths (Arctiinae) under climate change. Specifically, we assessed whether protected areas will gain or lose species under climate change and mapped their locations in the Atlantic Forest, in order to assess potential spatial patterns of protected areas that will gain or lose species richness. Comparisons were completed using modeled species occurrence data based on the current and projected climate in 2080. We also built a null model for random allocation of protected areas to identify where reductions in species richness will be more severe than expected. We employed several modern techniques for modeling species' distributions and summarized results using ensembles of models. Our models indicate areas of high species richness in the central and southern regions of the Atlantic Forest both for now and the future. However, we estimate that in 2080 these regions should become climatically unsuitable, decreasing the species' distribution area. Around 4% of species were predicted to become extinct, some of them being endemic to the biome. Estimates of species turnover from current to future climate tended to be high, but these findings are dependent on modeling methods. Our most important results show that only a few protected areas in the southern region of the biome would gain species. Protected areas in semideciduous forests in the western region of the biome would lose more species than expected by the null model employed. Hence, current protected areas are worse off, than just randomly selected areas, at protecting species in the future.

  16. Holocene climate changes in the Cape Hatteras region

    NASA Astrophysics Data System (ADS)

    Naughton, F.; Keigwin, L. D.; Peteet, D. M.; Desprat, S.; Oliveira, D.; Abrantes, F.

    2013-12-01

    In the last century many studies have been done in various naturally occurring archives to understand the nature, timing and causes of Holocene natural climate oscillations. Most of the available Holocene climatic reconstructions are however, not based on a direct comparison of terrestrial, marine and ice records making it difficult to obtain an accurate understanding of the interactions of the atmosphere-ocean-land systems and their relationship in global climate variability. Few studies based on direct sea land comparison have been reported for some key areas of the eastern North Atlantic but almost none in the western North Atlantic. Here we present a direct comparison between terrestrial (pollen) and marine (planktonic δ18O) proxies from a well dated (ten AMS 14C dates on planktonic foraminifera and seaweed) slope core (KNR 178-2 JPC 32), retrieved close to Cape Hatteras (35°58.58'N, 74°42.77'W, 1006 m). This study provides information on eastern North America vegetation and on the northwestern Atlantic sea surface response to both Holocene long-term and rapid climate changes. Five intervals, marked mainly by changes in temperate trees are associated with long term climate shifts (12000-9150 ka; 9150-7250 ka; 7250-5350 ka; 5350-2800 ka; 2800-700 ka). Over these intervals, several abrupt cooling events are noted, as well as several indications of shifts in moisture. The comparison of our data with those available and unpublished records from several key sites of the North Atlantic region, gives insights into the nature, timing and causes of Holocene climate oscillations in the North Atlantic region and in particular off Cape Hatteras.

  17. Annually resolved North Atlantic marine climate over the last millennium

    NASA Astrophysics Data System (ADS)

    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.

  18. Annually resolved North Atlantic marine climate over the last millennium

    PubMed Central

    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.

    2016-01-01

    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. PMID:27922004

  19. Linking North Atlantic Teleconnections to Latitudinal Variability of Wave Climate Along the North American Atlantic Coast

    NASA Astrophysics Data System (ADS)

    Provancha, C.; Adams, P. N.; Hegermiller, C.; Storlazzi, C. D.

    2015-12-01

    Shoreline change via coastal erosion and accretion is largely influenced by variations in ocean wave climate. Identifying the sources of these variations is challenging because the timing of wave energy delivery varies over multiple timescales within ocean basins. We present the results of an investigation of USACE Wave Information Studies hindcast hourly wave heights, periods, and directions along the North American Atlantic coast from 1980-2012, designed to explore links between wave climate and teleconnection patterns. Trends in median and extreme significant wave heights (SWHs) demonstrate that mean monthly SWHs increased from 1 to 5 cm/yr along the roughly 3000 km reach of study area, with changes in hurricane season waves appearing to be most influential in producing the overall trends. Distributions of SWHs categorized by North Atlantic Oscillation (NAO) phase, show that positive-period NAO SWHs are greater than negative-period NAO SWHs along the entire eastern seaboard (25°N to 45°N). The most prominent wave direction off Cape Cod, MA during positive-period NAO is approximately 105°, as compared to approximately 75° during negative-period NAO. Prominent wave directions between Cape Canaveral, FL, and Savannah, GA exhibit a similar shift but during opposite phases of the NAO. The results of this analysis suggest that the atmosphere-ocean interactions associated with contrasting NAO phases can significantly change the wave climate observed offshore along the North American Atlantic coast, altering alongshore wave energy fluxes and sediment transport patterns along the coast.

  20. Adjustment of the global climate to an abrupt slowdown of the Atlantic meridional overturning circulation

    NASA Astrophysics Data System (ADS)

    Cheng, Wei; Bitz, Cecilia M.; Chiang, John C. H.

    We explore the adjustment of the global climate to an abrupt slowdown of the Atlantic Meridional Circulation (AMOC), with a particular focus on the energetics. The slowdown is induced by a sudden freshwater perturbation in the North Atlantic. Reduction in the AMOC decreases northward ocean heat transport (OHT) and leads to cooling in the northern high latitudes. This cooling results in a local reduction to the top of atmosphere (TOA) radiative heat loss and an increase in northward atmospheric heat transport (AHT). The energy for the increased northward AHT comes from a combination of increased downward radiative flux at the TOA in the southern tropics and anomalous heating from the ocean in the northern tropics, both of which are consequences of the southward shift in the Intertropical Convergence Zone. Hence, viewed in the energetics framework, the atmospheric response to an AMOC slowdown extends throughout the Northern Hemisphere and into the tropics, and suggests an intimate coupling between the two regions. The mechanisms for the high-latitude-tropical coupling are examined. When comparing freshwater perturbation experiments in modern and Last Glacial Maximum (LGM) background states, we found that the changes to the northward OHT, and the mechanisms of global adjustment to the AMOC slowdown, were qualitatively similar in both instances. The one major difference is that freshening in the LGM climate induces a significantly stronger sea ice feedback than in a modern climate, allowing greater local cooling of the North Atlantic, and causing a commensurately larger global climate adjustment.

  1. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic

    2008-11-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.

  2. Review article. Studying climate effects on ecology through the use of climate indices: the North Atlantic Oscillation, El Niño Southern Oscillation and beyond.

    PubMed Central

    Stenseth, Nils Chr; Ottersen, Geir; Hurrell, James W; Mysterud, Atle; Lima, Mauricio; Chan, Kung-Sik; Yoccoz, Nigel G; Adlandsvik, Bjørn

    2003-01-01

    Whereas the El Niño Southern Oscillation (ENSO) affects weather and climate variability worldwide, the North Atlantic Oscillation (NAO) represents the dominant climate pattern in the North Atlantic region. Both climate systems have been demonstrated to considerably influence ecological processes. Several other large-scale climate patterns also exist. Although less well known outside the field of climatology, these patterns are also likely to be of ecological interest. We provide an overview of these climate patterns within the context of the ecological effects of climate variability. The application of climate indices by definition reduces complex space and time variability into simple measures, 'packages of weather'. The disadvantages of using global climate indices are all related to the fact that another level of problems are added to the ecology-climate interface, namely the link between global climate indices and local climate. We identify issues related to: (i) spatial variation; (ii) seasonality; (iii) non-stationarity; (iv) nonlinearity; and (v) lack of correlation in the relationship between global and local climate. The main advantages of using global climate indices are: (i) biological effects may be related more strongly to global indices than to any single local climate variable; (ii) it helps to avoid problems of model selection; (iii) it opens the possibility for ecologists to make predictions; and (iv) they are typically readily available on Internet. PMID:14561270

  3. North Atlantic climate evolution through the Plio-Pleistocene climate transitions

    NASA Astrophysics Data System (ADS)

    Lawrence, K. T.; Sosdian, S.; White, H. E.; Rosenthal, Y.

    2010-12-01

    During the Plio-Pleistocene, the Earth witnessed the growth of large northern hemisphere ice sheets and profound changes in both North Atlantic and global climate. Here, we present a ~ 3.2 Myr long, orbitally-resolved alkenone sea surface temperature (SST) record from Deep Sea Drilling Project (DSDP) Site 607 (41°N, 33°W, water depth 3427 m) in the North Atlantic Ocean. We employ a multi-proxy approach comparing these new observations with existing bottom water temperature (BWT) and stable isotope time series from the same site and SST time series from other sites, shedding new light on Plio-Pleistocene climate change. North Atlantic temperature records show a long-term cooling with two major steps occurring during the late Pliocene (3.1 to 2.4 Ma) and the mid-Pleistocene (1.5 to 0.8 Ma), closely timed with intervals of major change in northern hemisphere ice sheets. Existing evidence suggests that the late Pliocene cooling may have been caused by a thresholded response to secular changes in atmospheric carbon dioxide (CO 2). While an explanation for the mid-Pleistocene cooling may involve glacial-interglacial changes in atmospheric CO 2, it seems to also require a change in the behavior of the ice sheets themselves. North Atlantic climate responses were closely phased with benthic oxygen isotope (δ 18O) changes during the "41 kyr world," indicating a strong common northern hemisphere high latitude imprint on North Atlantic climate signals. After the mid-Pleistocene transition (MPT), North Atlantic SST records and the Site 607 benthic carbon isotope (δ 13C) record are more closely phased with δ 18O, whereas BWT significantly leads δ 18O in the 100 kyr band, suggesting a shift from a northern to a southern hemisphere influence on North Atlantic BWT. We propose that the expansion of the West Antarctic ice sheet (WAIS) across the MPT increased the production and export of Antarctic Bottom Water from the Southern Ocean and subsequently controlled its incursion

  4. Multidecadal Atlantic climate variability and its impact on marine pelagic communities

    NASA Astrophysics Data System (ADS)

    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

  5. Path Dependence of Regional Climate Change

    NASA Astrophysics Data System (ADS)

    Herrington, Tyler; Zickfeld, Kirsten

    2013-04-01

    Path dependence of the climate response to CO2 forcing has been investigated from a global mean perspective, with evidence suggesting that long-term global mean temperature and precipitation changes are proportional to cumulative CO2 emissions, and independent of emissions pathway. Little research, however, has been done on path dependence of regional climate changes, particularly in areas that could be affected by tipping points. Here, we utilize the UVic Earth System Climate Model version 2.9, an Earth System Model of Intermediate Complexity. It consists of a 3-dimensional ocean general circulation model, coupled with a dynamic-thermodynamic sea ice model, and a thermodynamic energy-moisture balance model of the atmosphere. This is then coupled with a terrestrial carbon cycle model and an ocean carbon-cycle model containing an inorganic carbon and marine ecosystem component. Model coverage is global with a zonal resolution of 3.6 degrees and meridional resolution of 1.8 degrees. The model is forced with idealized emissions scenarios across five cumulative emission groups (1300 GtC, 2300 GtC, 3300 GtC, 4300 GtC, and 5300 GtC) to explore the path dependence of (and the possibility of hysteresis in) regional climate changes. Emission curves include both fossil carbon emissions and emissions from land use changes, and span a variety of peak and decline scenarios with varying emission rates, as well as overshoot and instantaneous pulse scenarios. Tipping points being explored include those responsible for the disappearance of summer Arctic sea-ice, the irreversible melt of the Greenland Ice Sheet, the collapse of the Atlantic Thermohaline Circulation, and the dieback of the Amazonian Rainforest. Preliminary results suggest that global mean climate change after cessation of CO2 emissions is independent of the emissions pathway, only varying with total cumulative emissions, in accordance with results from earlier studies. Forthcoming analysis will investigate path

  6. Climate change velocity underestimates climate change exposure in mountainous regions

    PubMed Central

    Dobrowski, Solomon Z.; Parks, Sean A.

    2016-01-01

    Climate change velocity is a vector depiction of the rate of climate displacement used for assessing climate change impacts. Interpreting velocity requires an assumption that climate trajectory length is proportional to climate change exposure; longer paths suggest greater exposure. However, distance is an imperfect measure of exposure because it does not quantify the extent to which trajectories traverse areas of dissimilar climate. Here we calculate velocity and minimum cumulative exposure (MCE) in degrees Celsius along climate trajectories for North America. We find that velocity is weakly related to MCE; each metric identifies contrasting areas of vulnerability to climate change. Notably, velocity underestimates exposure in mountainous regions where climate trajectories traverse dissimilar climates, resulting in high MCE. In contrast, in flat regions velocity is high where MCE is low, as these areas have negligible climatic resistance to movement. Our results suggest that mountainous regions are more climatically isolated than previously reported. PMID:27476545

  7. Climate change velocity underestimates climate change exposure in mountainous regions

    NASA Astrophysics Data System (ADS)

    Dobrowski, Solomon Z.; Parks, Sean A.

    2016-08-01

    Climate change velocity is a vector depiction of the rate of climate displacement used for assessing climate change impacts. Interpreting velocity requires an assumption that climate trajectory length is proportional to climate change exposure; longer paths suggest greater exposure. However, distance is an imperfect measure of exposure because it does not quantify the extent to which trajectories traverse areas of dissimilar climate. Here we calculate velocity and minimum cumulative exposure (MCE) in degrees Celsius along climate trajectories for North America. We find that velocity is weakly related to MCE; each metric identifies contrasting areas of vulnerability to climate change. Notably, velocity underestimates exposure in mountainous regions where climate trajectories traverse dissimilar climates, resulting in high MCE. In contrast, in flat regions velocity is high where MCE is low, as these areas have negligible climatic resistance to movement. Our results suggest that mountainous regions are more climatically isolated than previously reported.

  8. Regional climate impacts of a possible future grand solar minimum

    PubMed Central

    Ineson, Sarah; Maycock, Amanda C.; Gray, Lesley J.; Scaife, Adam A.; Dunstone, Nick J.; Harder, Jerald W.; Knight, Jeff R.; Lockwood, Mike; Manners, James C.; Wood, Richard A.

    2015-01-01

    Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations. PMID:26102364

  9. Regional climate impacts of a possible future grand solar minimum.

    PubMed

    Ineson, Sarah; Maycock, Amanda C; Gray, Lesley J; Scaife, Adam A; Dunstone, Nick J; Harder, Jerald W; Knight, Jeff R; Lockwood, Mike; Manners, James C; Wood, Richard A

    2015-06-23

    Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations.

  10. Reliability of regional climate simulations

    NASA Astrophysics Data System (ADS)

    Ahrens, W.; Block, A.; Böhm, U.; Hauffe, D.; Keuler, K.; Kücken, M.; Nocke, Th.

    2003-04-01

    Quantification of uncertainty becomes more and more a key issue for assessing the trustability of future climate scenarios. In addition to the mean conditions, climate impact modelers focus in particular on extremes. Before generating such scenarios using e.g. dynamic regional climate models, a careful validation of present-day simulations should be performed to determine the range of errors for the quantities of interest under recent conditions as a raw estimate of their uncertainty in the future. Often, multiple aspects shall be covered together, and the required simulation accuracy depends on the user's demand. In our approach, a massive parallel regional climate model shall be used on the one hand to generate "long-term" high-resolution climate scenarios for several decades, and on the other hand to provide very high-resolution ensemble simulations of future dry spells or heavy rainfall events. To diagnosis the model's performance for present-day simulations, we have recently developed and tested a first version of a validation and visualization chain for this model. It is, however, applicable in a much more general sense and could be used as a common test bed for any regional climate model aiming at this type of simulations. Depending on the user's interest, integrated quality measures can be derived for near-surface parameters using multivariate techniques and multidimensional distance measures in a first step. At this point, advanced visualization techniques have been developed and included to allow for visual data mining and to qualitatively identify dominating aspects and regularities. Univariate techniques that are especially designed to assess climatic aspects in terms of statistical properties can then be used to quantitatively diagnose the error contributions of the individual used parameters. Finally, a comprehensive in-depth diagnosis tool allows to investigate, why the model produces the obtained near-surface results to answer the question if the

  11. Flood events across the North Atlantic region - past development and future perspectives

    NASA Astrophysics Data System (ADS)

    Matti, Bettina; Dieppois, Bastien; Lawler, Damian; Dahlke, Helen E.; Lyon, Steve W.

    2016-04-01

    Flood events have a large impact on humans, both socially and economically. An increase in winter and spring flooding across much of northern Europe in recent years opened up the question of changing underlying hydro-climatic drivers of flood events. Predicting the manifestation of such changes is difficult due to the natural variability and fluctuations in northern hydrological systems caused by large-scale atmospheric circulations, especially under altered climate conditions. Improving knowledge on the complexity of these hydrological systems and their interactions with climate is essential to be able to determine drivers of flood events and to predict changes in these drivers under altered climate conditions. This is particularly true for the North Atlantic region where both physical catchment properties and large-scale atmospheric circulations have a profound influence on floods. This study explores changes in streamflow across North Atlantic region catchments. An emphasis is placed on high-flow events, namely the timing and magnitude of past flood events, and selected flood percentiles were tested for stationarity by applying a flood frequency analysis. The issue of non-stationarity of flood return periods is important when linking streamflow to large-scale atmospheric circulations. Natural fluctuations in these circulations are found to have a strong influence on the outcome causing natural variability in streamflow records. Long time series and a multi-temporal approach allows for determining drivers of floods and linking streamflow to large-scale atmospheric circulations. Exploring changes in selected hydrological signatures consistency was found across much of the North Atlantic region suggesting a shift in flow regime. The lack of an overall regional pattern suggests that how catchments respond to changes in climatic drivers is strongly influenced by their physical characteristics. A better understanding of hydrological response to climate drivers is

  12. Atlantic overturning responses to Late Pleistocene climate forcings.

    PubMed

    Lisiecki, Lorraine E; Raymo, Maureen E; Curry, William B

    2008-11-06

    The factors driving glacial changes in ocean overturning circulation are not well understood. On the basis of a comparison of 20 climate variables over the past four glacial cycles, the SPECMAP project proposed that summer insolation at high northern latitudes (that is, Milankovitch forcing) drives the same sequence of ocean circulation and other climate responses over 100-kyr eccentricity cycles, 41-kyr obliquity cycles and 23-kyr precession cycles. SPECMAP analysed the circulation response at only a few sites in the Atlantic Ocean, however, and the phase of circulation response has been shown to vary by site and orbital band. Here we test the SPECMAP hypothesis by measuring the phase of orbital responses in benthic delta(13)C (a proxy indicator of ocean nutrient content) at 24 sites throughout the Atlantic over the past 425 kyr. On the basis of delta(13)C responses at 3,000-4,010 m water depth, we find that maxima in Milankovitch forcing are associated with greater mid-depth overturning in the obliquity band but less overturning in the precession band. This suggests that Atlantic overturning is strongly sensitive to factors beyond ice volume and summer insolation at high northern latitudes. A better understanding of these processes could lead to improvements in model estimates of overturning rates, which range from a 40 per cent increase to a 40 per cent decrease at the Last Glacial Maximum and a 10-50 per cent decrease over the next 140 yr in response to projected increases in atmospheric CO(2) (ref. 4).

  13. Climate history in the south Atlantic subtropical gyre over the last 4 Ma

    NASA Astrophysics Data System (ADS)

    Wojcieszek, D. E.; Dekens, P. S.

    2010-12-01

    The early Pliocene (3-5 Ma) is the most recent time in the Earth’s history when climate was significantly warmer than today. Even though the climatic boundary conditions (i.e. incoming solar radiation, distribution of continents, atmospheric pCO2) were similar to today, the average global temperature was about 3-4°C warmer, ice sheets were smaller, and the sea level was about 35 m higher. Previous studies show that in the early Pliocene, in both Pacific and Atlantic Oceans, sea surface temperatures (SST) of the eastern equatorial and coastal upwelling regions were warmer than today (by ~2-9°C), while western equatorial warm pools had SST similar to today. As a consequence, zonal and meridional SST gradients were reduced. According to atmospheric modeling studies, the reduced gradients played a role in sustaining Pliocene warmth and the increasing gradients, caused by the cooling of the upwelling regions, favored the northern hemisphere glaciation. However, the lack of data from non-upwelling regions forces these models to interpolate SSTs based on the gradients in the modern ocean. This research is the first to provide data from a non-upwelling region in the south Atlantic subtropical gyre. We present G.sacculifer Mg/Ca and δ18O records at the ODP site 1264 (28.53°S; 2.85°E, 2505 m water depth), located on the Walvis Ridge in the south Atlantic subtropical gyre. The Mg/Ca SST record displays no long-term trend over the past 4 Ma. The south Atlantic subtropical gyre was not affected by the forcing that caused the 8-9°C cooling of the Benguela upwelling, as recorded at ODP sites 1082 and 1084. The difference between SST trends at ODP sites 1082 and 1084 and the ODP site 1264 indicate a significant change in SST gradients between south Atlantic subtropical gyre and the Benguela upwelling region. The complementary δ18O record will provide information about local salinity changes due to ice volume changes. The combined records will give us a thorough picture of

  14. Pairwise comparisons to reconstruct mean temperature in the Arctic Atlantic Region over the last 2,000 years

    NASA Astrophysics Data System (ADS)

    Hanhijärvi, Sami; Tingley, Martin P.; Korhola, Atte

    2013-10-01

    Existing multi-proxy climate reconstruction methods assume the suitably transformed proxy time series are linearly related to the target climate variable, which is likely a simplifying assumption for many proxy records. Furthermore, with a single exception, these methods face problems with varying temporal resolutions of the proxy data. Here we introduce a new reconstruction method that uses the ordering of all pairs of proxy observations within each record to arrive at a consensus time series that best agrees with all proxy records. The resulting unitless composite time series is subsequently calibrated to the instrumental record to provide an estimate of past climate. By considering only pairwise comparisons, this method, which we call PaiCo, facilitates the inclusion of records with differing temporal resolutions, and relaxes the assumption of linearity to the more general assumption of a monotonically increasing relationship between each proxy series and the target climate variable. We apply PaiCo to a newly assembled collection of high-quality proxy data to reconstruct the mean temperature of the Northernmost Atlantic region, which we call Arctic Atlantic, over the last 2,000 years. The Arctic Atlantic is a dynamically important region known to feature substantial temperature variability over recent millennia, and PaiCo allows for a more thorough investigation of the Arctic Atlantic regional climate as we include a diverse array of terrestrial and marine proxies with annual to multidecadal temporal resolutions. Comparisons of the PaiCo reconstruction to recent reconstructions covering larger areas indicate greater climatic variability in the Arctic Atlantic than for the Arctic as a whole. The Arctic Atlantic reconstruction features temperatures during the Roman Warm Period and Medieval Climate Anomaly that are comparable or even warmer than those of the twentieth century, and coldest temperatures in the middle of the nineteenth century, just prior to the onset

  15. Solar Forcing of Regional Climate Change During the Maunder Minimum

    NASA Technical Reports Server (NTRS)

    Shindell, Drew T.; Schmidt, Gavin A.; Mann, Michael E.; Rind, David; Waple, Anne; Hansen, James E. (Technical Monitor)

    2002-01-01

    We examine the climate response to solar irradiance changes between the late 17th century Maunder Minimum and the late 18th century. Global average temperature changes are small (about 0.3 to 0.4 C) in both a climate model and empirical reconstructions. However, regional temperature changes are quite large. In the model, these occur primarily through a forced shift toward the low index state of the Arctic Oscillation/North Atlantic Oscillation. This leads to colder temperatures over the Northern Hemisphere continents, especially in winter (1 to 2 C), in agreement with historical records and proxy data for surface temperatures.

  16. Climate impact on plankton ecosystems in the Northeast Atlantic.

    PubMed

    Richardson, Anthony J; Schoeman, David S

    2004-09-10

    It is now widely accepted that global warming is occurring, yet its effects on the world's largest ecosystem, the marine pelagic realm, are largely unknown. We show that sea surface warming in the Northeast Atlantic is accompanied by increasing phytoplankton abundance in cooler regions and decreasing phytoplankton abundance in warmer regions. This impact propagates up the food web (bottom-up control) through copepod herbivores to zooplankton carnivores because of tight trophic coupling. Future warming is therefore likely to alter the spatial distribution of primary and secondary pelagic production, affecting ecosystem services and placing additional stress on already-depleted fish and mammal populations.

  17. Tropical Rain Forest and Climate Dynamics of the Atlantic Lowland, Southern Brazil, during the Late Quaternary

    NASA Astrophysics Data System (ADS)

    Behling, Hermann; Negrelle, Raquel R. B.

    2001-11-01

    Palynological analysis of a core from the Atlantic rain forest region in Brazil provides unprecedented insight into late Quaternary vegetational and climate dynamics within this southern tropical lowland. The 576-cm-long sediment core is from a former beach-ridge "valley," located 3 km inland from the Atlantic Ocean. Radio-carbon dates suggest that sediment deposition began prior to 35,000 14C yr B.P. Between ca. 37,500 and ca. 27,500 14C yr B.P. and during the last glacial maximum (LGM; ca. 27,500 to ca. 14,500 14C yr B.P.), the coastal rain forest was replaced by grassland and patches of cold-adapted forest. Tropical trees, such as Alchornea, Moraceae/Urticaceae, and Arecaceae, were almost completely absent during the LGM. Furthermore, their distributions were shifted at least 750 km further north, suggesting a cooling between 3°C and 7°C and a strengthening of Antarctic cold fronts during full-glacial times. A depauperate tropical rain forest developed as part of a successional sequence after ca. 12,300 14C yr B.P. There is no evidence that Araucaria trees occurred in the Atlantic lowland during glacial times. The rain forest was disturbed by marine incursions during the early Holocene period until ca. 6100 14C yr B.P., as indicated by the presence of microforaminifera. A closed Atlantic rain forest then developed at the study site.

  18. Decreased frequency of North Atlantic polar lows associated with future climate warming.

    PubMed

    Zahn, Matthias; von Storch, Hans

    2010-09-16

    Every winter, the high-latitude oceans are struck by severe storms that are considerably smaller than the weather-dominating synoptic depressions. Accompanied by strong winds and heavy precipitation, these often explosively developing mesoscale cyclones-termed polar lows-constitute a threat to offshore activities such as shipping or oil and gas exploitation. Yet owing to their small scale, polar lows are poorly represented in the observational and global reanalysis data often used for climatological investigations of atmospheric features and cannot be assessed in coarse-resolution global simulations of possible future climates. Here we show that in a future anthropogenically warmed climate, the frequency of polar lows is projected to decline. We used a series of regional climate model simulations to downscale a set of global climate change scenarios from the Intergovernmental Panel of Climate Change. In this process, we first simulated the formation of polar low systems in the North Atlantic and then counted the individual cases. A previous study using NCEP/NCAR re-analysis data revealed that polar low frequency from 1948 to 2005 did not systematically change. Now, in projections for the end of the twenty-first century, we found a significantly lower number of polar lows and a northward shift of their mean genesis region in response to elevated atmospheric greenhouse gas concentration. This change can be related to changes in the North Atlantic sea surface temperature and mid-troposphere temperature; the latter is found to rise faster than the former so that the resulting stability is increased, hindering the formation or intensification of polar lows. Our results provide a rare example of a climate change effect in which a type of extreme weather is likely to decrease, rather than increase.

  19. Influence of the North Atlantic on climate change in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Glok, Natalia; Alekseev, Genrikh; Smirnov, Aleksander; Vyasilova, Anastasia

    2015-04-01

    This study is based on the observations taken from the meteorological archives, satellite and historic visual observations of sea ice, global SST, data of water temperature in the upper layer on the section in the Barents Sea. For processing data was used factor analysis, calculation of correlation matrices with different delay between the Barents Sea and selected areas in North Atlantic. It is shown that the inflow of Atlantic water into the Barents Sea has a major influence on the climate of the region and its changes affect the variations of all climate characteristics. Decadal and interannual changes of air temperature in the Barents Sea are closely related (correlation over 0.8) with temperature of water, coming from the Norwegian Sea. The effect of these changes is seen in the air temperature in the Kara Sea. Atlantic water inflow especially impact on winter sea ice in the Barents Sea. The correlation between the average water temperature at section along the Kola meridian and sea ice extent in the Barents Sea in May reaches values of -0.86. To enhance the predictive capability established dependence, the study was extended to the area of the North Atlantic, where temperature anomalies are formed. In the North Atlantic from the equator to 80 ° N were identified 6 areas where the average annual SST anomalies are associated with SST anomalies and sea ice extent (SIE) in the Barents Sea. Detailed analysis with monthly SST from HadISST for 1951 - 2013 identified two areas with the greatest influence on the Barents Sea. One area is the northern region of the Gulf Stream and other is the equatorial region. The corresponding delays amounted to 26 months and 4-5 years. The relationship between changes AMO index, averaged over August-October, and SIE in the Barents Sea in January is evaluated. Correlation coefficient between them with 3 year delay is -0.54. Implemented study revealed the importance of teleconnection between SST anomalies in the North Atlantic and SST

  20. Multicentennial Agulhas leakage variability and links to North Atlantic climate during the past 80,000 years

    NASA Astrophysics Data System (ADS)

    Dyez, Kelsey A.; Zahn, Rainer; Hall, Ian R.

    2014-12-01

    New high-resolution sea surface temperature (SST) and sea surface salinity (SSS) estimates are presented from the Agulhas Bank slope in the Atlantic sector of the Agulhas Corridor using planktic foraminiferal (Globigerinoides ruber) δ18O and Mg/Ca-derived SST. By focusing on the last 80,000 years, this is the first fine-scale Agulhas leakage record that overlaps in time with much of the Greenland ice core record of abrupt climate changes in the North Atlantic region. The multicentennial profiles indicate instances of warm SST and/or increased SSS coincident with Northern Hemisphere cool periods, followed by Northern Hemisphere warming. These periods of enhanced SST and SSS in the Agulhas Corridor occur at the last glacial termination (T1) and during North Atlantic cold episodes associated with Heinrich (H) meltwater events. To a first-order approximation, the timing of maximal salinity events in relation to periods of North Atlantic freshwater perturbation is consistent with the concept suggested by climate models that enhanced Agulhas leakage provides for buoyancy compensation and can potentially trigger increased convective activity in the North Atlantic, thereby restoring Atlantic overturning circulation after relatively weak states.

  1. Why were Past North Atlantic Warming Conditions Associated with Drier Climate in the Western United States?

    NASA Astrophysics Data System (ADS)

    Wong, C. I.; Potter, G. L.; Montanez, I. P.; Otto-Bliesner, B. L.; Behling, P.; Oster, J. L.

    2014-12-01

    Investigating climate dynamics governing rainfall over the western US during past warmings and coolings of the last glacial and deglaciation is pertinent to understanding how precipitation patterns might change with future global warming, especially as the processes driving the global hydrological reorganization affecting this drought-prone region during these rapid temperature changes remain unresolved. We present model climates of the Bølling warm event (14,500 years ago) and Younger Dryas cool event (12,200 years ago) that i) uniquely enable the assessment of dueling hypothesis about the atmospheric teleconnections responsible for abrupt temperature shifts in the North Atlantic region to variations in moisture conditions across the western US, and ii) show that existing hypotheses about these teleconnections are unsupported. Modeling results show no evidence for a north-south shift of the Pacific winter storm track, and we argue that a tropical moisture source with evolving trajectory cannot explain alternation between wet/dry conditions, which have been reconstructed from the proxy record. Alternatively, model results support a new hypothesis that variations in the intensity of the winter storm track, corresponding to its expansion/contraction, can account for regional moisture differences between warm and cool intervals of the last deglaciation. Furthermore, we demonstrate that the mechanism forcing the teleconnection between the North Atlantic and western US is the same across different boundary conditions. In our simulation, during the last deglaciation, and in simulations of future warming, perturbation of the Rossby wave structure reconfigures the atmospheric state. This reconfiguration affects the Aleutian Low and high-pressure ridge over and off of the northern North American coastline driving variability in the storm track. Similarity between the processes governing the climate response during these distinct time intervals illustrates the robust nature

  2. Causes of Ocean Surface temperature Changes in Atlantic andPacific Topical Cyclogenesis Regions

    SciTech Connect

    Santer, B.D.; Wigley, T.M.L.; Gleckler, P.J.; Bonfils, C.; Wehner, M.F.; AchutaRao, K.; Barnett, T.P.; Boyle, J.S.; Bruggemann, W.; Fiorino, M.; Gillett, N.; Hansen, J.E.; Jones, P.D.; Klein, S.A.; Meehl,G.A.; Raper, S.C.B.; Reynolds, R.W.; Stott, P.A.; Taylor, K.E.; Washington, W.M.

    2006-01-31

    Previous research has identified links between changes in sea surface temperature (SST) and hurricane intensity. We use climate models to study the possible causes of SST changes in Atlantic and Pacific tropical cyclogenesis regions. The observed SST increases in these regions range from 0.32 to 0.67 C over the 20th century. The 22 climate models examined here suggest that century-timescale SST changes of this magnitude cannot be explained solely by unforced variability of the climate system, even under conservative assumptions regarding the magnitude of this variability. Model simulations that include external forcing by combined anthropogenic and natural factors are generally capable of replicating observed SST changes in both tropical cyclogenesis regions.

  3. Climate Dynamics of Regional US Southeastern drought

    NASA Astrophysics Data System (ADS)

    Arrigo, J.

    2008-12-01

    The phenomena of droughts both regional and continental have received considerable attention from both science and policy. Understanding the larger scale dynamics of these events is critical to improving predictability, management and mitigation strategies. The history of drought in the United States shows both long (multi-decadal) and short (seasonal or yearly) droughts in various regions. Some of the most severe droughts, such as those with the largest economic losses or that have received the most attention both from the scientific and broader communities have occurred in the Midwest/Great Plains (e.g. the "Dust Bowl" years, the 1988 drought) and generally correlate with continent-wide anomalies. The Southeast region of the US, while generally having a more humid temperature climate than the rest of the country, also is subject to periods of drought conditions. In this study we analyze long term records of PDSI in the southeastern United States. While some occurrences correlate with larger continental scale droughts, many severe southeastern droughts occur during a synoptic pattern correlating with wetter conditions through the greater Midwest, have a seasonal pattern different than larger continental scale anomalies, and show correlations with patterns in Atlantic tropical activity. While winter and spring deficits may initiate a drought, we find a proportionally larger decrease in summertime precipitation during severe drought periods. Some of this decrease may be related to the contribution of tropical systems, which increases in the periods following droughts. We suggest that the dynamics of drought in this region differ from the larger US pattern, and particularly need to account for the interaction between continental and tropical contributions. With an increasing population and areas of high agricultural productivity, we argue this region deserves further attention from both the scientific and larger community, that understanding these dynamics will

  4. Frequency and intensity of palaeofloods at the interface of Atlantic and Mediterranean climate domains

    NASA Astrophysics Data System (ADS)

    Wilhelm, Bruno; Vogel, Hendrik; Crouzet, Christian; Etienne, David; Anselmetti, Flavio S.

    2016-04-01

    The long-term response of the flood activity to both Atlantic and Mediterranean climatic influences was explored by studying a lake sequence (Lake Foréant) of the Western European Alps. High-resolution sedimentological and geochemical analysis revealed 171 event layers, 168 of which result from past flood events over the last millennium. The layer thickness was used as a proxy of intensity of past floods. Because the Foréant palaeoflood record is in agreement with the documented variability of historical floods resulting from local and mesoscale, summer-to-autumn convective events, it is assumed to highlight changes in flood frequency and intensity related to such events typical of both Atlantic (local events) and Mediterranean (meso-scale events) climatic influences. Comparing the Foréant record with other Atlantic-influenced and Mediterranean-influenced regional flood records highlights a common feature in all flood patterns that is a higher flood frequency during the cold period of the Little Ice Age (LIA, AD 1300-1900). In contrast, high-intensity flood events are apparent during both, the cold LIA and the warm Medieval Climate Anomaly (MCA, AD 950-1250). However, there is a tendency towards higher frequencies of high-intensity flood events during the warm MCA. The MCA extremes could mean that under the global warming scenario, we might see an increase in intensity (not in frequency). However, the flood frequency and intensity in course of 20th century warming trend did not change significantly. Uncertainties in future evolution of flood intensity lie in the interpretation of the lack of 20th century extremes (transition or stable?) and the different climate forcing factors between the two periods (greenhouse gases vs. solar/volcanic eruptions).

  5. Regional Climate Modeling: Progress, Challenges, and Prospects

    SciTech Connect

    Wang, Yuqing; Leung, Lai R.; McGregor, John L.; Lee, Dong-Kyou; Wang, Wei-Chyung; Ding, Yihui; Kimura, Fujio

    2004-12-01

    Regional climate modeling with regional climate models (RCMs) has matured over the past decade and allows for meaningful utilization in a broad spectrum of applications. In this paper, latest progresses in regional climate modeling studies are reviewed, including RCM development, applications of RCMs to dynamical downscaling for climate change assessment, seasonal climate predictions and climate process studies, and the study of regional climate predictability. Challenges and potential directions of future research in this important area are discussed, with the focus on those to which less attention has been given previously, such as the importance of ensemble simulations, further development and improvement of regional climate modeling approach, modeling extreme climate events and sub-daily variation of clouds and precipitation, model evaluation and diagnostics, applications of RCMs to climate process studies and seasonal predictions, and development of regional earth system models. It is believed that with both the demonstrated credibility of RCMs’ capability in reproducing not only monthly to seasonal mean climate and interannual variability but also the extreme climate events when driven by good quality reanalysis and the continuous improvements in the skill of global general circulation models (GCMs) in simulating large-scale atmospheric circulation, regional climate modeling will remain an important dynamical downscaling tool for providing the needed information for assessing climate change impacts and seasonal climate predictions, and a powerful tool for improving our understanding of regional climate processes. An internationally coordinated effort can be developed with different focuses by different groups to advance regional climate modeling studies. It is also recognized that since the final quality of the results from nested RCMs depends in part on the realism of the large-scale forcing provided by GCMs, the reduction of errors and improvement in

  6. Relationship between solar irradiance and climatic variability in the subpolar North Atlantic since the Medieval Warm Period

    NASA Astrophysics Data System (ADS)

    Alonso-Garcia, M.; Flower, B. P.; Kleiven, H. F.; Andrews, J. T.

    2011-12-01

    The potential role of solar irradiance as a climate forcing during the Medieval Warm Period (MWP)-Little Ice Age (LIA)-20th Century interval can be tested using several proxies. In this work we use the occurrence of fine sand sized lithic grains (63-150 μm) in North Atlantic marine sediments to study the climatic history of high latitudes because these lithic grains were ice-rafted either by icebergs or sea-ice. The Holocene ice-rafted debris (IRD) flux is much lower than the IRD flux during glacial periods but the occurrence of hematite-stained grains (HSG) from Paleozoic red beds, Icelandic volcanic glass, and detrital carbonate in the fine sand fraction has been used to track climatic variability at several North Atlantic areas: Feni Drift off Ireland, off eastern Greenland near Denmark Strait, and off Newfoundland (Bond et al, 2001). This controversial work suggested that during the Holocene major ice-rafting discharges matched solar irradiance variability patterns inferred from cosmogenic nuclides (10Be fluxes measured in Greenland ice cores and 14C records from tree rings) and hence, variations in the solar output may have paced centennial- to millennial-scale climate variability in the North Atlantic region. Since 2001 improved 10Be and 14C records have been released and several new sedimentological studies of subpolar North Atlantic marine sites suggested that other climatic forcings may have been involved in Holocene climate variability rather than solar activity (e.g. Moros et al., 2006; Andrews et al., 2009). Moreover, even the ice-rafted origin of the debris has been questioned at some sites. Here we present new high resolution North Atlantic IRD records from Denmark Strait off eastern Greenland and the Labrador Sea, in addition to recounts of sites on the Feni Drift off Ireland (Bond et al., 2001), to study climate variability in the subpolar North Atlantic since MWP. IRD counts are performed using the same technique as in Bond et al. (2001) to (1

  7. North Atlantic / Arctic Oscillations in the Pliocene: A Mechanism for Regional Warming?

    NASA Astrophysics Data System (ADS)

    Hill, Daniel; Csank, Adam; Lunt, Daniel; Haywood, Alan

    2010-05-01

    Pliocene climate is significantly warmer than modern globally, but particularly so in the North Atlantic and adjacent portions of the Arctic. In order to fully understand these changes we must examine not only the mean climate state, but also changes to the significant oscillatory modes of regional climate. The Arctic and North Atlantic Oscillations (AO/NAO) are the primary atmospheric oscillatory modes in the North Atlantic / Eastern Arctic region, observed mainly in mean sea level pressure, but accounting for typically a third of all climate variability in the Northern Hemisphere. Advanced General Circulation Models (GCMs) of both the modern and Mid-Pliocene Warm Period (MPWP) enable the study of AO/NAO changes between the two intervals and the examination of the causes and significance of any changes. Models show that there is a large change in the mean state of the pressure systems in the North Atlantic, on which the NAO index is based. While the mean Azores High remains relatively constant throughout Pliocene and modern simulations, the mean Icelandic Low is much deeper in MPWP models. By changing the various parameters that are different between the modern and Pliocene simulations, the cause of this change can be examined. The observed changes in mean AO/NAO state can be largely attributed to changes in the orography of the Rocky Mountains. Changes in the Pliocene NAO also include the seasonal and interannual variability seen in the indexes. While the Hadley Centre GCM, used in this study, consistently performs well in studies of regional climate change and atmospheric phenomenon, different GCMs have been shown to produce different NAO responses to climate change. Multiple models can be used to find patterns that are robust between different GCMs, which should be possible in the new PlioMIP study. Secondly, comparison with palaeoclimate proxy data can be used to ground truth the modelled changes. Although this will always be difficult with an interannual

  8. TRICARE Mid-Atlantic Region Business Planning Initiatives

    DTIC Science & Technology

    1999-06-01

    This paper discusses the business planning processes and the development of a business plan. A business plan reflects the ultimate goal of an...provides valuable information about business operations. An assessment of business planning initiatives within the TRICARE Mid-Atlantic Region is provided

  9. The Atlantic Multi-Decadal Oscillation Climate Impact - Zonal and Meridional Coupling

    NASA Astrophysics Data System (ADS)

    Werner, Rolf; Kirillov, Andrey; Valev, Dimitar; Atanassov, Atanas; Danov, Dimitar; Guineva, Veneta

    2016-07-01

    The Atlantic multi-decadal oscillation (AMO) shows a period of about 60-70 years. Over the time span from 1860 up to 2014 the AMO has had a strong climate impact on the Northern Hemisphere. The AMO is considered to be related to the Atlantic overturning circulation, but the origin of the oscillation is not fully understood up till now. To study the AMO impact on climate, the Hadcrut4, Crut4 and HadSST3 temperature data sets have been employed in the current study. The influence of the AMO on the zonal and meridional temperature distribution has been investigated in detail. The strongest zonal AMO impact was obtained in the Arctic region. The results indicated that the AMO influence on temperature at Southern latitudes was opposite in phase compared to the temperature influence in the Northern Hemisphere, in agreement with the well known heat transfer phenomenon from South to North Atlantic. In the Northern Hemisphere the strongest AMO temperature impact was found over the Atlantic and America. In the West from American continent, over the Pacific, the AMO impact was the lowest obtained over the whole Northern Hemisphere. The Rocky Mountains and Sierra Madre, connected with it southwards, built up an atmospheric circulation barrier preventing a strong propagation of the AMO temperature signal westerly. The amplitude of the AMO index itself was greater during summer-fall. However stronger AMO influence on the Northern Hemisphere temperatures was found during the fall-winter season, when the differences between the Northern Hemisphere temperatures and the temperatures in the tropics were the greatest.

  10. Effects of orbital-scale ITCZ fluctuations on the mid Cretaceous tropical Atlantic region

    NASA Astrophysics Data System (ADS)

    Hofmann, P.; Beckmann, B.; Flögel, S.; Wagner, T.

    2009-04-01

    Shifts of the Inter Tropic Convergence Zone (ITCZ) on Milankovitch time scales have profound effects on the climate-ocean system of tropical regions. Changes in wind systems, regional hydrology and continental runoff linked to past fluctuations of the ITCZ are well known to have triggered a complex chain of forcing and feedback mechanisms between the regional biosphere and geosphere. In our study we explore these relationships for the mid-Cretaceous super-greenhouse. We present proxy records from two regions of the Coniacian tropical Atlantic, ODP Site 959 (West Africa off Ivory Coast) and ODP Site 1261 (Northern South America off Suriname) and compare them with results of GENESIS Atmospheric General Circulation modeling. Our data suggest that bioproductivity in the eastern tropical Atlantic mainly followed a precession controlled cyclic pattern which was closely linked to changes in nutrient and freshwater supply via continental runoff from the African continent. Different from that bioproductivity in the western tropical Atlantic shows a strong obliquity and eccentricity cycle pattern. We propose that these differences in the west were mainly caused by fluctuations in wind-driven upwelling off northern South America with a constant and high supply of nutrients from the continent maintaining the ocean redox system anoxic without interruption. Bioproductivity from wind-driven upwelling in the west would have pushed the water column into repetitive sulfidic conditions (euxinia), as confirmed by geochemical evidence. Overall bioproductivity east and west of the tropical Atlantic was high supporting deposition of extensive black shale deposits. The observed differences in depositional patterns on both sides of the Coniacian tropical Atlantic support that (orbital-driven) fluctuations of the ITCZ were mainly responsible, with strong contrasts in regional moisture distribution over Africa and South America and local strengthening of the trade wind system causing

  11. Sensitivity of modern climate to the presence, strength and salinity of Mediterranean-Atlantic exchange in a global general circulation model

    NASA Astrophysics Data System (ADS)

    Ivanovic, Ruza F.; Valdes, Paul J.; Gregoire, Lauren; Flecker, Rachel; Gutjahr, Marcus

    2014-02-01

    Mediterranean Outflow Water (MOW) is thought to be a key contributor to the strength and stability of Atlantic Meridional Overturning Circulation (AMOC), but the future of Mediterranean-Atlantic water exchange is uncertain. It is chiefly dependent on the difference between Mediterranean and Atlantic temperature and salinity characteristics, and as a semi-enclosed basin, the Mediterranean is particularly vulnerable to future changes in climate and water usage. Certainly, there is strong geologic evidence that the Mediterranean underwent dramatic salinity and sea-level fluctuations in the past. Here, we use a fully coupled atmosphere-ocean General Circulation Model to examine the impact of changes in Mediterranean-Atlantic exchange on global ocean circulation and climate. Our results suggest that MOW strengthens and possibly stabilises the AMOC not through any contribution towards NADW formation, but by delivering relatively warm, saline water to southbound Atlantic currents below 800 m. However, we find almost no climate signal associated with changes in Mediterranean-Atlantic flow strength. Mediterranean salinity, on the other hand, controls MOW buoyancy in the Atlantic and therefore affects its interaction with the shallow-intermediate circulation patterns that govern surface climate. Changing Mediterranean salinity by a factor of two reorganises shallow North Atlantic circulation, resulting in regional climate anomalies in the North Atlantic, Labrador and Greenland-Iceland-Norwegian Seas of ±4 °C or more. Although such major variations in salinity are believed to have occurred in the past, they are unlikely to occur in the near future. However, our work does suggest that changes in the Mediterranean's hydrological balance can impact global-scale climate.

  12. MID-ATLANTIC REGIONAL VULNERABILITY ASSESSMENT

    EPA Science Inventory

    ORD's Regional Vulnerability Assessment (REVA) Program is developing and demonstrating approaches to assess current and future environmental vulnerabilities so that risk management activities can be targeted. The sister program to EMA.P (Environmental Monitoring Assessment Progr...

  13. Variability of tropical cyclone rapid intensification in the North Atlantic and its relationship with climate variations

    NASA Astrophysics Data System (ADS)

    Wang, Chunzai; Wang, Xidong; Weisberg, Robert H.; Black, Michael L.

    2017-02-01

    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

  14. Advancing climate dynamics toward reliable regional climate projections

    NASA Astrophysics Data System (ADS)

    Xie, Shang-Ping

    2013-06-01

    With a scientific consensus reached regarding the anthropogenic effect on global mean temperature, developing reliable regional climate projections has emerged as a new challenge for climate science. A national project was launched in China in 2012 to study ocean's role in regional climate change. This paper starts with a review of recent advances in the study of regional climate response to global warming, followed by a description of the Chinese project including the rationale, objectives, and plan for field observations. The 15 research articles that follow in the special issue are highlighted, representing some of the initial results from the project.

  15. On the Tropical Atlantic SST warm bias in the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Wahl, Sebastian; Latif, Mojib; Park, Wonsun; Keenlyside, Noel

    2011-03-01

    Most of the current coupled general circulation models show a strong warm bias in the eastern Tropical Atlantic. In this paper, various sensitivity experiments with the Kiel Climate Model (KCM) are described. A largely reduced warm bias and an improved seasonal cycle in the eastern Tropical Atlantic are simulated in one particular version of KCM. By comparing the stable and well-tested standard version with the sensitivity experiments and the modified version, mechanisms contributing to the reduction of the eastern Atlantic warm bias are identified and compared to what has been proposed in literature. The error in the spring and early summer zonal winds associated with erroneous zonal precipitation seems to be the key mechanism, and large-scale coupled ocean-atmosphere feedbacks play an important role in reducing the warm bias. Improved winds in boreal spring cause the summer cooling in the eastern Tropical Atlantic (ETA) via shoaling of the thermocline and increased upwelling, and hence reduced sea surface temperature (SST). Reduced SSTs in the summer suppress convection and favor the development of low-level cloud cover in the ETA region. Subsurface ocean structure is shown to be improved, and potentially influences the development of the bias. The strong warm bias along the southeastern coastline is related to underestimation of low-level cloud cover and the associated overestimation of surface shortwave radiation in the same region. Therefore, in addition to the primarily wind forced response at the equator both changes in surface shortwave radiation and outgoing longwave radiation contribute significantly to reduction of the warm bias from summer to fall.

  16. Climate and recruitment of rocky shore intertidal invertebrates in the eastern North Atlantic.

    PubMed

    Broitman, Bernardo R; Mieszkowska, Nova; Helmuth, Brian; Blanchette, Carol A

    2008-11-01

    Studies of the impacts of climate and climate change on biological systems often attempt to correlate ecological responses with basin-scale indices such as the North Atlantic Oscillation (NAO). However, such correlations, while useful for detecting long-term trends, are unable to provide a mechanism linking the physical environment and ecological processes. Here we evaluate the effects of the NAO on recruitment variability of rocky intertidal invertebrates in the North Atlantic examining two possible climate-related pathways. Using a highly conservative test we interpret associations with the NAO integrated over a season (three months) as an indicator of atmospheric effects on newly settled recruits (NAO3), and the effects of the NAO integrated over six months (NAO6) as an indicator of changes in ocean circulation affecting patterns of larval transport. Through an extensive literature survey we found 13 time series, restricted to southwest Ireland and Britain and comprising five species, that could be used for statistical analysis. Significant correlations with NAO3, our proxy for atmospheric effects, were observed in the south-central domain of our study region (southwest Ireland and south England). Significant correlations with NAO6, the proxy for ocean circulation effects, were detected on southwest Ireland. The associations were detected for three (two barnacles and a topshell) at two sites. These results suggest that the NAO can have effects on the recruitment of intertidal invertebrates through different pathways linked to climate and be distributed heterogeneously in space. Based on previous evidence and the sign and geographic location of significant correlations, we suggest that winter NAO effects are likely to occur as a result of effects on the survival of early life stages settling during spring or through changes in phenology. Our results argue that a combination of modeling and synthesis can be used to generate hypotheses regarding the effects of

  17. Global scale climate trends associated with variable Atlantic thermohaline transport as inferred from changes in intense hurricane activity

    SciTech Connect

    Gray, W.M.; Sheaffer, J.D.

    1996-12-31

    This paper presents a review of the most recent 100 years of data of hurricane activity in the tropical Atlantic, and proposes that decadal variations of hurricane activity are but one of a host of observed concurrent global climate trends which may all link to multi-decadal scale variations of the Atlantic thermohaline circulation. The data reviews shows that long term multi-decadal variations in hurricane activity appear to be linked (1) to mode-like variations of regional and global sea surface temperatures (SSTs) and (2) to concurrent trends in global air temperature, pressure anomalies, and atmospheric circulations. Many of these effects extend well beyond the tropical Atlantic. The pre-eminent effect which seems to dominate all others as a unifying process for these multi-decadal changes is variations in the Atlantic thermohaline circulation. A synthesis process is suggested for specifying physically consistent global interactions linking the Atlantic conveyor and decadal trend associations in global climate data. In this way, some of the global data may yield factors which are useful for forecasting the onset and termination of new decadal trends of hurricane activity. 30 refs., 4 figs.

  18. A Long, Consistent Surface Wind Dataset for Climate Change Analysis: Application over the Equatorial Atlantic

    NASA Astrophysics Data System (ADS)

    Tokinaga, H.; Xie, S.

    2010-12-01

    Surface wind change is a principal factor for spatial patterns of sea surface temperature (SST) warming through changes in surface evaporation, ocean vertical mixing and wind-driven ocean circulation. However, historical ship-based measurements of sea surface wind speed displays a spurious upward trend due to increases in anemometer height. To correct this bias, we construct the Wave and Anemometer-based Sea-surface Wind (WASWind) dataset for the last six decades from ICOADS ship reports, applying height correction for anemometer measured winds, rejecting spurious Beaufort winds, and using wind wave height to estimate wind speed. WASWind substantially reduces the upward trend in wind speed and its trend patterns are quite similar to satellite-measured surface wind changes for the recent two decades. Surface wind changes in WASWind are consistent with historical sea level pressure observations over the global oceans, illustrating its utility for climate change analysis. As an example, WASWind captures relaxation of the equatorial trade winds coupled with a weakening of the equatorial Atlantic cold tongue over the last six decades. The surface wind changes are also consistent with those in atmospheric convection and subsurface temperature in this region, indicating that thermocline feedback plays a key role in recent climate change over the equatorial Atlantic.

  19. The influence of solar variability past, present and future, on North Atlantic climate.

    NASA Astrophysics Data System (ADS)

    Dunstone, Nick; Scaife, Adam; Ineson, Sarah; Gray, Lesley; Knight, Jeff; Lockwood, Mike; Maycock, Amanda

    2014-05-01

    There has long existed observational evidence for a link between solar activity (both the semi-regular 11-yr cycle and longer term variability) and regional climate variability. In the last few years progress is starting to be made in understanding such observational correlations from physical mechanistic viewpoint. Firstly, new observations of solar spectral irradiance from the SORCE satellite have raised the possibility of much larger variability in the UV than previously appreciated. Secondly, state of the art computer climate models now explicitly resolve the Earth's stratosphere allowing the influence of solar variability to be simulated here. By driving such climate models with the larger solar UV variability implied by the latest satellite observations, surface climate impacts have been shown in the Northern Hemisphere winter that are consistent with late 20th century climate data. Low solar activity is associated with the negative phase of the North Atlantic Oscillation (NAO) and hence colder winters over northern Europe and the USA. We discuss the implications for seasonal/decadal climate prediction. Further work has examined the role of ocean feedbacks in amplifying this tropospheric response. There is robust statistical evidence that such a feedback operates in the observations and gives a lag of 3-4 years for the maximum tropospheric response after the maximum solar forcing. This lag does not generally appear to be reproduced by current climate models. We discuss how this observational evidence may be a valuable way of assessing the relative strength of ocean-atmosphere coupling in the present generation of climate models. The prolonged solar minimum during the transition between solar cycles 23 & 24, combined with the relatively low maximum activity of cycle 24, have increased suggestions that we may be coming to the end of the grand solar maximum which dominated the 20th century. A return to Maunder Minimum like solar activity is therefore a possible

  20. Frequency and intensity of palaeofloods at the interface of Atlantic and Mediterranean climate domains

    NASA Astrophysics Data System (ADS)

    Wilhelm, B.; Vogel, H.; Crouzet, C.; Etienne, D.; Anselmetti, F. S.

    2016-02-01

    Mediterranean climatic influences was explored by studying a lake sequence (Lake Foréant) of the Western European Alps. High-resolution sedimentological and geochemical analysis revealed 171 event layers, 168 of which result from past flood events over the last millennium. The layer thickness was used as a proxy of intensity of past floods. Because the Foréant palaeoflood record is in agreement with the documented variability of historical floods resulting from local and mesoscale, summer-to-autumn convective events, it is assumed to highlight changes in flood frequency and intensity related to such events typical of both Atlantic (local events) and Mediterranean (mesoscale events) climatic influences. Comparing the Foréant record with other Atlantic-influenced and Mediterranean-influenced regional flood records highlights a common feature in all flood patterns that is a higher flood frequency during the cold period of the Little Ice Age (LIA, AD 1300-1900). In contrast, high-intensity flood events are apparent during both the cold LIA and the warm Medieval Climate Anomaly (MCA, AD 950-1250). However, there is a tendency towards higher frequencies of high-intensity flood events during the warm MCA. The MCA extremes could mean that under the global warming scenario, we might see an increase in intensity (not in frequency). However, the flood frequency and intensity in the course of the 20th century warming trend did not change significantly. Uncertainties in future evolution of flood intensity lie in the interpretation of the lack of 20th century extremes (transition or stable?) and the different climate forcing factors between the two periods (greenhouse gases vs. solar and/or volcanic eruptions).

  1. Evidence for multiple drivers of North Atlantic multi-decadal climate variability using CMIP5 models

    NASA Astrophysics Data System (ADS)

    Terray, L.

    2012-12-01

    Observed North Atlantic Ocean surface temperatures have changed in a non-monotonic and non-uniform fashion over the last century. While future North Atlantic decadal-to-multi-decadal climate change will be driven by a combination of internal variability and anthropogenic as well as natural forcings, the relative importance of these effects is still unclear for the 20th century [Ting et al., 2009; Knight 2009; Ottera et al. 2010; DelSole et al., 2011; Booth et al. 2012]. Here we assess the relative roles of greenhouses gases, anthropogenic aerosols, natural forcings and internal variability to the North Atlantic surface temperature decadal fluctuations using CMIP5 multi-model historical simulations driven by estimates of observed external forcings. While the latter are the main source of decadal variability in the tropics and subtropics, there is a large contribution from the unforced component to subpolar Atlantic variations. Reconstruction of forced response patterns suggests that anthropogenic forcings are the main causes of the accelerated warming of the last three decades while internal variability has a dominant contribution to the early 20th-century temperature multi-decadal swings and recent abrupt changes in the subpolar Atlantic. Significant inter-model spread with regard to the spatial response patterns to anthropogenic forcing leads to substantial uncertainty as to robust attribution statements for the mid-to-late 20th century North Atlantic warm and cold periods. Comparing internal variability from preindustrial simulations with that estimated from the observed residual after removing the best estimate of the total forced response leads to a consistency metric which allows to identify models with a biased forced response.; CMIP5 multi-model ratio (ρ_LF) of the externally forced -natural and anthropogenic- variance, σ_EF to the total variance, σ_T, of fluctuations with a period greater than 10 years. Stippling indicates regions where the null

  2. A Hierarchical Evaluation of Regional Climate Simulations

    SciTech Connect

    Leung, Lai-Yung R.; Ringler, Todd; Collins, William D.; Taylor, Mark; Ashfaq, Moetasim

    2013-08-20

    Global climate models (GCMs) are the primary tools for predicting the evolution of the climate system. Through decades of development, GCMs have demonstrated useful skill in simulating climate at continental to global scales. However, large uncertainties remain in projecting climate change at regional scales, which limit our ability to inform decisions on climate change adaptation and mitigation. To bridge this gap, different modeling approaches including nested regional climate models (RCMs), global stretch-grid models, and global high-resolution atmospheric models have been used to provide regional climate simulations (Leung et al. 2003). In previous efforts to evaluate these approaches, isolating their relative merits was not possible because factors such as dynamical frameworks, physics parameterizations, and model resolutions were not systematically constrained. With advances in high performance computing, it is now feasible to run coupled atmosphere-ocean GCMs at horizontal resolution comparable to what RCMs use today. Global models with local refinement using unstructured grids have become available for modeling regional climate (e.g., Rauscher et al. 2012; Ringler et al. 2013). While they offer opportunities to improve climate simulations, significant efforts are needed to test their veracity for regional-scale climate simulations.

  3. A simple coupled model of tropical Atlantic decadal climate variability

    NASA Astrophysics Data System (ADS)

    Kushnir, Yochanan; Seager, Richard; Miller, Jennifer; Chiang, John C. H.

    2002-12-01

    A linear, zonally averaged model of the interaction between the tropical Atlantic (TA) atmosphere and ocean is presented. A balance between evaporation and meridional heat advection in the mixed layer determines the sea surface temperature tendency. The atmosphere is a fixed-depth, sub-cloud layer in which the specific humidity anomaly is determined by a steady-state balance between evaporation, meridional advection, and a parameterized humidity exchange with the free atmosphere. When the model is integrated, forced with observed surface wind anomalies from 1965 to the present, its simulation of the observed sea surface temperature (SST) is realistic and comparable to a simulation with a full ocean GCM. A statistical representation of surface winds and their relationship to the SST gradient across the equator is used to formulate and test a coupled model of their regional variability. Forced on both sides of the equator, in the trade-wind regions, with ``white-noise'' windspeed perturbations, the SST-wind relationship in the near-equatorial region feeds back positively on existing SST anomalies and gives rise to decadal variability.

  4. Impact of the Atlantic Warm Pool on Climate and Hurricanes: An Overview of Recent Understanding

    NASA Astrophysics Data System (ADS)

    Wang, C.; Lee, S.; Enfield, D.

    2007-05-01

    The Atlantic Warm Pool (AWP) with a large body of warm water is comprised of the Intra-Americas Sea (i.e., the Gulf of Mexico and the Caribbean Sea) and the western tropical North Atlantic. Located to its northeastern side is the North Atlantic Subtropical High (NASH) that produces the tropical easterly trade winds. The easterly trade winds carry moisture from the tropical North Atlantic into the Caribbean Sea where the flow intensifies forming the Caribbean Low-Level Jet (CLLJ). The CLLJ then splits into two branches: One turning northward and connecting with the Great Plains Low-Level Jet (GPLLJ), and the other one continuing westward across Central America into the eastern North Pacific. The easterly CLLJ and its moisture transport are maximized in the summer and winter, whereas they are minimized in the fall and spring. This semi-annual feature results from the semi-annual variation of sea level pressure in the Caribbean region owing to the westward extension and eastward retreat of the NASH. The summertime strong easterly CLLJ is associated with a maximum of sea level pressure, a relative minimum of rainfall (the mid-summer drought), and a minimum of tropical cyclogenesis in July in the Caribbean Sea. The NCAR community atmospheric model ensemble runs show that climate response to the AWP heating extends beyond the AWP region to the eastern North Pacific and North America, owing to the westward propagation of Rossby wave response. The effect of the AWP is to weaken the summertime NASH, especially at its southwestern edge. The AWP also strengthens the summertime continental low over the North American monsoon region. In response to these pressure changes, the easterly CLLJ and its moisture transport are weakened, but its semi-annual feature does not change. The AWP-induced change of atmospheric circulation changes the moisture convergence that results in increased rainfall in the AWP region and the eastern North Pacific. The model runs also show that the effect

  5. A link between North Atlantic cooling and dry events in the core SW monsoon region in Lonar Lake, central India

    NASA Astrophysics Data System (ADS)

    Menzel, Philip; Gaye, Birgit; Prasad, Sushma; Plessen, Birgit; Stebich, Martina; Anoop, Ambili; Riedel, Nils; Basavaiah, Nathani

    2014-05-01

    A sediment core from Lonar Lake in central India covers the complete Holocene and was used to reconstruct the monsoon history of the core SW-monsoon region. We compare C/N ratios, stable carbon and nitrogen isotopes, grain size, as well as amino acid derived degradation proxies with climatically sensitive proxies of other records from South Asia and the North Atlantic region. The comparison reveals some more or less contemporaneous climate shifts. At Lonar Lake, a general long term climate transition from wet conditions during the early Holocene to drier conditions during the late Holocene, delineating the insolation curve, can be reconstructed. Several phases of shorter term climate alteration that superimpose the general climate trend correlate with cold phases in the North Atlantic region. The most pronounced climate deteriorations indicated by our data occurred between 6.2 - 5.2, 4.65 - 3.9, and 2.05 - 0.55 cal ka BP. The strong dry phase between 4.65 - 3.9 cal ka BP at Lonar Lake corroborates the hypothesis that severe climate deterioration contributed to the decline of the Indus Civilisation about 3.9 ka BP.

  6. How Synchronous was the Transition into the Younger Dryas across the Euro-Atlantic Region?

    NASA Astrophysics Data System (ADS)

    Schenk, F.; Muschitiello, F.; Heikkilä, M. P.; Väliranta, M.; Tarasov, L.; Brandefelt, J.; Johansson, A. V.; Naslund, J. O.; Wohlfarth, B.

    2015-12-01

    Observations of a currently weakening subpolar gyre south of Greenland has again increased scientific attention regarding the role of the Atlantic Meridional Overturning Circulation (AMOC) for the regional to global climate. The rapid climate shift of the Younger Dryas (YD, GS-1) cold reversal during the last deglaciation is attributed to an abrupt slowdown or collapse of the AMOC due to a strong meltwater pulse and/or the rapid disintegration of the Laurentide Ice sheet. Although such a dramatic event is not expected for the future, the spatiotemporal climatic response to such a slowdown is an interesting test case. Two recently well dated proxy records around the North Sea region suggest a non-synchronous early cooling/onset of the YD compared to Greenland (NGRIP). Presentation #61803 discusses the hypothesis of a local cooling as a response to increased ice berg calving and/or meltwater from Fenno-Scandinavian Ice Sheet (FIS) during the late Alleröd warm phase (GI-1a). Here we study CCSM3 model output from the quasi-transient atmosphere-ocean simulation (TraCE) where no strong contribution from FIS is considered from the late Alleröd into the YD. We evaluate to which extent the spatiotemporal temperature response to the AMOC slowdown of the simulation is synchronous over the Euro-Atlantic region and how atmospheric teleconnections reorganize during the rapid shift into the YD. In addition, we run time-slice experiments at high spatial resolution of around 100 km with the Community Earth System Model CESM1.0.5 for the late Alleröd and YD to compare spatial climatic differences for both periods taking into account the regional influence from continental ice sheets in more detail.

  7. The North Atlantic Oscillation as a driver of rapid climate change in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Delworth, Thomas L.; Zeng, Fanrong; Vecchi, Gabriel A.; Yang, Xiaosong; Zhang, Liping; Zhang, Rong

    2016-07-01

    Pronounced climate changes have occurred since the 1970s, including rapid loss of Arctic sea ice, large-scale warming and increased tropical storm activity in the Atlantic. Anthropogenic radiative forcing is likely to have played a major role in these changes, but the relative influence of anthropogenic forcing and natural variability is not well established. The above changes have also occurred during a period in which the North Atlantic Oscillation has shown marked multidecadal variations. Here we investigate the role of the North Atlantic Oscillation in these rapid changes through its influence on the Atlantic meridional overturning circulation and ocean heat transport. We use climate models to show that observed multidecadal variations of the North Atlantic Oscillation can induce multidecadal variations in the Atlantic meridional overturning circulation and poleward ocean heat transport in the Atlantic, extending to the Arctic. Our results suggest that these variations have contributed to the rapid loss of Arctic sea ice, Northern Hemisphere warming, and changing Atlantic tropical storm activity, especially in the late 1990s and early 2000s. These multidecadal variations are superimposed on long-term anthropogenic forcing trends that are the dominant factor in long-term Arctic sea ice loss and hemispheric warming.

  8. Millennial-scale climate instabilities in the subtropical Atlantic during MIS 6 and 7

    NASA Astrophysics Data System (ADS)

    Scheinwald, A.; Billups, K.

    2012-12-01

    We have constructed a high resolution (~200 year) planktonic foraminiferal stable isotope record spanning Marine Isotope Stages (MIS) 6 and 7 in the subtropical Atlantic (ODP Site 1059). The record fills a gap in a ~1 million year long time series of millennial-scale surface ocean hydrography in this region. Our ultimate goal is to test the hypothesis that millennial-scale climate signals in the northwestern subtropical Atlantic are linked to external driving factors such as the harmonics of precession. Results show that longer-term trends in the oxygen isotope data spanning MIS 6-7 closely follow precessional forcing allowing us to refine the original age model of Grützner et al. (2002). High frequency variations are superimposed on the long-term trend during both the glacial MIS 6 and the interglacial MIS 7. Spectral analyses indicate high concentration of power at millennial-scale periodicities of 10.9 kyr, 5.2 kyr, and 2.8 kyr. These periodicities are close to those expected from harmonics of precessional forcing during this interval of time (11.5 kyr, 5.8 kyr, 2.8 kyr). We will show the evolution of the millennial-scale periodicities in this region over the past 1 million years by splicing the record into published ones and unifying the age model.

  9. Particulate Matter Pollution and its Regional Transport in the Mid-Atlantic States

    NASA Astrophysics Data System (ADS)

    He, H.; Goldberg, D. L.; Hembeck, L.; Canty, T. P.; Vinciguerra, T.; Ring, A.; Salawitch, R. J.; Dickerson, R. R.

    2015-12-01

    Particulate matter (PM) causes negative effects on human health, impair visibility in scenic areas, and affect regional/global climate. PM can be formed through chemical changes of precursors, including biogenic VOCs and anthropogenic SO2 and NOx often from fossil fuel combustion. In the past decades, PM pollution in the US has improved substantially. However, some areas in the Mid-Atlantic States are still designated as 'moderate' nonattainment by EPA. We utilize datasets obtained during the NASA 2011 DISCOVER-AQ campaign to characterize the composition and distribution of summertime PM pollution in the Mid-Atlantic States. Aircraft measurements and OMI satellite retrieval of major anthropogenic precursors (NO2 and SO2) are analyzed to investigate the regional transport of PM precursors from upwind sources. We compare PM concentration and chemical composition observed during the field campaign to CMAQ simulations with the latest EPA emission inventory. Specifically, we focus on the secondary organic aerosol (SOA) chemistry in CMAQ simulations using various biogenic VOCs estimates from the MEGAN and BEIS models. Airborne PM observations including PILS measurements from DISCOVER-AQ campaign and OMI retrievals of HCHO are also used to validate and improve the representation of SOA chemistry and PM pollution within CMAQ. The comparison reveals the source and evolution of PM pollution in the Mid-Atlantic States.

  10. Regional Changes in Extreme Climatic Events

    NASA Astrophysics Data System (ADS)

    Bell, J. L.; Sloan, L. C.; Snyder, M. A.

    2002-12-01

    This study focuses on California as a climatically complex region that is vulnerable to changes in water supply and delivery. A regional climate model is employed to assess changes in the frequency and intensity of extreme temperatures and precipitation. Significant increases in daily minimum and maximum temperatures occur with a doubling of atmospheric carbon dioxide concentration. Increases in daily temperatures lead to increases in prolonged heat waves and length of the growing season. Changes in total and extreme precipitation vary by geographic region.

  11. Land use and environmental assessment in the central Atlantic region

    NASA Technical Reports Server (NTRS)

    Alexander, R. H.; Fitzpatrick, K.; Lins, H. F., Jr.; Mcginty, H. K., III

    1975-01-01

    Data from high altitude aircraft, LANDSAT and Skylab were used in a comprehensive regional survey of land use and its associated environmental impact in the Central Atlantic Regional Ecological Test Site (CARETS). Each sensor system has advantages that were demonstrated by producing experimental land use maps and other data products, applying them to typical problems encountered in regional planning and environmental impact assessment, and presenting the results to prospective users for evaluation. An archival collection of imagery, maps, data summaries, and technical reports was assembled, constituting an environmental profile of the central Atlantic region. The investigation was organized into four closely-related modules, a land use information module, an environmental impact module, a user interaction and evaluation module, and a geographic information systems module. Results revealed a heterogeneous user community with diverse information needs, tending, however, definitely toward the higher-resolution sensor data and the larger-scale land use maps and related information products. Among project recommendations are greater efforts toward improving compatibility of federal, state, and local land use information programs, and greater efforts toward a broader exchange of imagery, computer tapes, and land use information derived therefrom.

  12. FY08 LDRD Final Report Regional Climate

    SciTech Connect

    Bader, D C; Chin, H; Caldwell, P M

    2009-05-19

    An integrated, multi-model capability for regional climate change simulation is needed to perform original analyses to understand and prepare for the impacts of climate change on the time and space scales that are critical to California's future environmental quality and economic prosperity. Our intent was to develop a very high resolution regional simulation capability to address consequences of climate change in California to complement the global modeling capability that is supported by DOE at LLNL and other institutions to inform national and international energy policies. The California state government, through the California Energy Commission (CEC), institutionalized the State's climate change assessment process through its biennial climate change reports. The bases for these reports, however, are global climate change simulations for future scenarios designed to inform international policy negotiations, and are primarily focused on the global to continental scale impacts of increasing emissions of greenhouse gases. These simulations do not meet the needs of California public and private officials who will make major decisions in the next decade that require an understanding of climate change in California for the next thirty to fifty years and its effects on energy use, water utilization, air quality, agriculture and natural ecosystems. With the additional development of regional dynamical climate modeling capability, LLNL will be able to design and execute global simulations specifically for scenarios important to the state, then use those results to drive regional simulations of the impacts of the simulated climate change for regions as small as individual cities or watersheds. Through this project, we systematically studied the strengths and weaknesses of downscaling global model results with a regional mesoscale model to guide others, particularly university researchers, who are using the technique based on models with less complete parameterizations or

  13. Bahamian speleothems reveal Atlantic climate variability during Heinrich Events

    NASA Astrophysics Data System (ADS)

    Arienzo, M. M.; Swart, P. K.; Broad, K.; Clement, A. C.; Eisenhauer, A.; Kakuk, B.

    2010-12-01

    During the last glacial period there is confounding evidence for global millennial scale variability in climate, dominated by Heinrich events and Dansgaard-Oeschger (D/O) events. These events have been documented in the ice core records, deep-sea sediment records and speleothems. Speleothem records have been studied from diverse localities such as South and Central America, Continental United States, Europe, and China, however, there is a significant lack of paleoclimate data from the subtropical Atlantic. Our analyses of stalagmites from the Bahamas reveal that Heinrich events are preserved in the geochemical signature of our samples. To date, over 15 stalagmites have been collected and dated from Blue Holes in the Bahamas. Currently submerged, the speleothems are collected using advanced diving technologies at depths ranging from 10-40 meters below sea level. Sample DC-09 was collected at 16.5 meters below sea level from Dan’s Cave, Abaco Island, Bahamas and was forming from approximately 13,700 to 30,000 ybp, determined from U/Th age dates. Sample DC-14 was collected at 23.5 meters below sea level from the same cave and was dated from 13,800 to 54,000 ybp. These samples provide a continuous record and replicate records from the same cave aid in the interpretation of the geochemical data. These samples have been analyzed for stable carbon and oxygen isotopes as well as trace elements at a 20 μm resolution. Preliminary analysis reveals enrichment in the carbon and oxygen isotope values with amplitudes as large as 4.5‰ associated with Heinrich events. This reflects a change from relatively arid to wetter conditions, which occur over periods as short as 50 years. When comparing the record from DC-09 to DC-14, DC-09 consists of a greater C and O change associated with each Heinrich Event. This is possibly driven in part by the differences in depth at which the samples were forming. There is a greater amount of material overlying the deeper sample, therefore

  14. Towards predictive understanding of regional climate change

    NASA Astrophysics Data System (ADS)

    Xie, Shang-Ping; Deser, Clara; Vecchi, Gabriel A.; Collins, Matthew; Delworth, Thomas L.; Hall, Alex; Hawkins, Ed; Johnson, Nathaniel C.; Cassou, Christophe; Giannini, Alessandra; Watanabe, Masahiro

    2015-10-01

    Regional information on climate change is urgently needed but often deemed unreliable. To achieve credible regional climate projections, it is essential to understand underlying physical processes, reduce model biases and evaluate their impact on projections, and adequately account for internal variability. In the tropics, where atmospheric internal variability is small compared with the forced change, advancing our understanding of the coupling between long-term changes in upper-ocean temperature and the atmospheric circulation will help most to narrow the uncertainty. In the extratropics, relatively large internal variability introduces substantial uncertainty, while exacerbating risks associated with extreme events. Large ensemble simulations are essential to estimate the probabilistic distribution of climate change on regional scales. Regional models inherit atmospheric circulation uncertainty from global models and do not automatically solve the problem of regional climate change. We conclude that the current priority is to understand and reduce uncertainties on scales greater than 100 km to aid assessments at finer scales.

  15. Pliocene planktic foraminifer census data from the North Atlantic region

    USGS Publications Warehouse

    ,

    1996-01-01

    INTRODUCTION: The U.S. Geological Survey is conducting a long-term study of the climatic and oceanographic conditions of the Pliocene known as PRISM (Pliocene Research, Interpretation, and Synoptic Mapping). One of the major elements of the study involves the use of quantitative composition of planktic foraminifer assemblages to estimate seasurface temperatures and identify major oceanographic boundaries and water masses (Dowsett, 1991; Dowsett and Poore, 1991; Dowsett et al., 1992; Dowsett et al., 1994). We have analyzed more than 900 samples from 19 core sites in the North Atlantic Basin (Fig. 1) resulting in a large volume of raw census data. These data are presented here together to facilitate comparison of North Atlantic faunal assemblages. Latitude, longitude, water depth, source of faunal data and source of data used to construct age model (or publication from which age model was taken) are provided for each locality in Table 1. All ages refer to the geomagnetic polarity time scale of Berggren et al. (1985). Counts of species tabulated in each sample are given in Tables 2-20. DSDP and ODP sample designations are abbreviated in Tables 2-20 as core-section, depth within section in centimeters (eg. 10-5, 34 = core 10, section 5, 34 cm below top of section 5).

  16. Solar influences on climate over the Atlantic / European sector

    NASA Astrophysics Data System (ADS)

    Gray, Lesley J.; Ball, Will; Misios, Stergios

    2017-02-01

    There is growing evidence that variability associated with the 11-year solar cycle has an impact at the Earth's surface and influences its weather and climate. Although the direct response to the Sun's variability is extremely small, a number of different mechanisms have been suggested that could amplify the signal, resulting in regional signals that are much larger than expected. In this paper the observed solar cycle signal at the Earth's surface is described, together with proposed mechanisms that involve modulation via the total incoming solar irradiance and via modulation of the ultra-violet part of the solar spectrum that influences ozone production in the stratosphere.

  17. Impact of the Atlantic Warm Pool on the Summer Climate of the Western Hemisphere

    NASA Astrophysics Data System (ADS)

    Wang, C.; Lee, S.; Enfield, D.

    2006-12-01

    The North Atlantic subtropical high (NASH), being the strongest during the summer, determines the strength of the tropical easterly trade winds at its southern flank. The easterly trade winds carry moisture from the tropical North Atlantic into the Caribbean Sea where the flow intensifies forming the Caribbean low-level jet (CLLJ). The CLLJ then splits into two branches: one turning northward and connecting with the Great Plains low-level jet (GPLLJ), and the other one continuing westward across Central America into the eastern North Pacific. This paper finds that the easterly CLLJ is maximized in the summer and winter, whereas it is minimized in the fall and spring. The semi-annual feature of the CLLJ results from the semi-annual variation of sea level pressure in the Caribbean region owing to the westward extension and eastward retreat of the NASH. The Atlantic warm pool (AWP) with a large body of warm water is comprised of the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic. The NCAR community atmospheric model and observational data are used to investigate the impact of the AWP on the summer climate of the Western Hemisphere. Two groups of the model ensemble runs with and without the AWP are performed and compared. The model results show that the AWP is to weaken the summertime NASH, especially at its southwestern edge. The AWP also strengthens the summertime continental low over the North American monsoon region. In response to these pressure changes, the strength of the CLLJ is weakened, but its semi-annual feature does not change. The weakening of the CLLJ decreases the westward moisture transport from the AWP and thus suppresses rainfall in the eastern North Pacific. Our model runs show that the effect of the AWP is to weaken the southerly wind of the GPLLJ. However, the AWP strengthens the northward moisture transport of the GPLLJ in the summer because the AWP-induced increase of specific humidity overcomes the weakening of

  18. Great plains regional climate assessment technical report

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Great Plains region (GP) plays important role in providing food and energy to the economy of the United States. Multiple climatic and non-climatic stressors put multiple sectors, livelihoods and communities at risk, including agriculture, water, ecosystems and rural and tribal communities. The G...

  19. Regional Climate Change Hotspots over Africa

    NASA Astrophysics Data System (ADS)

    Anber, U.; Zakey, A.; Abd El Wahab, M.

    2009-04-01

    Regional Climate Change Index (RCCI), is developed based on regional mean precipitation change, mean surface air temperature change, and change in precipitation and temperature interannual variability. The RCCI is a comparative index designed to identify the most responsive regions to climate change, or Hot- Spots. The RCCI is calculated for Seven land regions over North Africa and Arabian region from the latest set of climate change projections by 14 global climates for the A1B, A2 and B1 IPCC emission scenarios. The concept of climate change can be approaches from the viewpoint of vulnerability or from that of climate response. In the former case a Hot-Spot can be defined as a region for which potential climate change impacts on the environment or different activity sectors can be particularly pronounced. In the other case, a Hot-Spot can be defined as a region whose climate is especially responsive to global change. In particular, the characterization of climate change response-based Hot-Spot can provide key information to identify and investigate climate change Hot-Spots based on results from multi-model ensemble of climate change simulations performed by modeling groups from around the world as contributions to the Fourth Assessment Report of Intergovernmental Panel on Climate Change (IPCC). A Regional Climate Change Index (RCCI) is defined based on four variables: change in regional mean surface air temperature relative to the global average temperature change ( or Regional Warming Amplification Factor, RWAF ), change in mean regional precipitation (P % , of present day value ), change in regional surface air temperature interannual variability (T % ,of present day value), change in regional precipitation interannual variability (P % ,of present day value ). In the definition of the RCCI it is important to include quantities other than mean change because often mean changes are not the only important factors for specific impacts. We thus also include inter

  20. Regional Climate Change Hotspots over Africa

    NASA Astrophysics Data System (ADS)

    Anber, U.

    2009-04-01

    Regional Climate Change Index (RCCI), is developed based on regional mean precipitation change, mean surface air temperature change, and change in precipitation and temperature interannual variability. The RCCI is a comparative index designed to identify the most responsive regions to climate change, or Hot- Spots. The RCCI is calculated for Seven land regions over North Africa and Arabian region from the latest set of climate change projections by 14 global climates for the A1B, A2 and B1 IPCC emission scenarios. The concept of climate change can be approaches from the viewpoint of vulnerability or from that of climate response. In the former case a Hot-Spot can be defined as a region for which potential climate change impacts on the environment or different activity sectors can be particularly pronounced. In the other case, a Hot-Spot can be defined as a region whose climate is especially responsive to global change. In particular, the characterization of climate change response-based Hot-Spot can provide key information to identify and investigate climate change Hot-Spots based on results from multi-model ensemble of climate change simulations performed by modeling groups from around the world as contributions to the Assessment Report of Intergovernmental Panel on Climate Change (IPCC). A Regional Climate Change Index (RCCI) is defined based on four variables: change in regional mean surface air temperature relative to the global average temperature change ( or Regional Warming Amplification Factor, RWAF ), change in mean regional precipitation ( , of present day value ), change in regional surface air temperature interannual variability ( ,of present day value), change in regional precipitation interannual variability ( , of present day value ). In the definition of the RCCI it is important to include quantities other than mean change because often mean changes are not the only important factors for specific impacts. We thus also include inter annual

  1. How Well Do Global Climate Models Simulate the Variability of Atlantic Tropical Cyclones Associated with ENSO?

    NASA Technical Reports Server (NTRS)

    Wang, Hui; Long, Lindsey; Kumar, Arun; Wang, Wanqiu; Schemm, Jae-Kyung E.; Zhao, Ming; Vecchi, Gabriel A.; LaRow, Timorhy E.; Lim, Young-Kwon; Schubert, Siegfried D.; Shaevitz, Daniel A.; Camargo, Suzana J.; Henderson, Naomi; Kim, Daehyun; Jonas, Jeffrey A.; Walsh, Kevin J. E.

    2013-01-01

    The variability of Atlantic tropical cyclones (TCs) associated with El Nino-Southern Oscillation (ENSO) in model simulations is assessed and compared with observations. The model experiments are 28-yr simulations forced with the observed sea surface temperature from 1982 to 2009. The simulations were coordinated by the U.S. CLIVAR Hurricane Working Group and conducted with five global climate models (GCMs) with a total of 16 ensemble members. The model performance is evaluated based on both individual model ensemble means and multi-model ensemble mean. The latter has the highest anomaly correlation (0.86) for the interannual variability of TCs. Previous observational studies show a strong association between ENSO and Atlantic TC activity, as well as distinctions in the TC activities during eastern Pacific (EP) and central Pacific (CP) El Nino events. The analysis of track density and TC origin indicates that each model has different mean biases. Overall, the GCMs simulate the variability of Atlantic TCs well with weaker activity during EP El Nino and stronger activity during La Nina. For CP El Nino, there is a slight increase in the number of TCs as compared with EP El Nino. However, the spatial distribution of track density and TC origin is less consistent among the models. Particularly, there is no indication of increasing TC activity over the U.S. southeast coastal region as in observations. The difference between the models and observations is likely due to the bias of vertical wind shear in response to the shift of tropical heating associated with CP El Nino, as well as the model bias in the mean circulation.

  2. Forced and unforced ocean temperature changes in Atlantic and Pacific tropical cyclogenesis regions.

    PubMed

    Santer, B D; Wigley, T M L; Gleckler, P J; Bonfils, C; Wehner, M F; Achutarao, K; Barnett, T P; Boyle, J S; Brüggemann, W; Fiorino, M; Gillett, N; Hansen, J E; Jones, P D; Klein, S A; Meehl, G A; Raper, S C B; Reynolds, R W; Taylor, K E; Washington, W M

    2006-09-19

    Previous research has identified links between changes in sea surface temperature (SST) and hurricane intensity. We use climate models to study the possible causes of SST changes in Atlantic and Pacific tropical cyclogenesis regions. The observed SST increases in these regions range from 0.32 degrees C to 0.67 degrees C over the 20th century. The 22 climate models examined here suggest that century-timescale SST changes of this magnitude cannot be explained solely by unforced variability of the climate system. We employ model simulations of natural internal variability to make probabilistic estimates of the contribution of external forcing to observed SST changes. For the period 1906-2005, we find an 84% chance that external forcing explains at least 67% of observed SST increases in the two tropical cyclogenesis regions. Model "20th-century" simulations, with external forcing by combined anthropogenic and natural factors, are generally capable of replicating observed SST increases. In experiments in which forcing factors are varied individually rather than jointly, human-caused changes in greenhouse gases are the main driver of the 20th-century SST increases in both tropical cyclogenesis regions.

  3. Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate.

    PubMed

    Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang

    2017-01-01

    Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term climate projection.

  4. North Atlantic and Arctic Ocean Climate Change in Pliocene Simulations Using the GISS ModelE2-R GCM

    NASA Astrophysics Data System (ADS)

    Chandler, M. A.; Sohl, L. E.; Jonas, J.; Kelley, M.; Rind, D.

    2013-12-01

    As part of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2, twelve research groups simulated the middle Pliocene climate using fully coupled versions of their ocean-atmosphere GCMs. Under the conditions prescribed by PlioMIP Experiment 2 (especially 25 meters of sea level rise, 405 ppm CO2, and reduced ice sheets) most coupled GCMs still underestimate ocean temperatures in the North Atlantic and Arctic Ocean regions. The GISS ModelE (AR5-version) originally produced the coolest results in these regions out of all the Pliocene simulations, with a greatly decreased AMOC and colder temperatures than modern in a large portion of the North Atlantic. However, improvements in the formulation of mesoscale mixing in the GISS ModelE, which have been incorporated in a more recent model update, led to significant changes in the simulation of the Pliocene (Chandler et al., 2013), including a warmer North Atlantic ocean, decreased Arctic sea ice, increased Atlantic meridional overturning circulation (AMOC) relative to the control run, and generally a more favorable comparison to proxy data. Despite these results, the relative role of the various forcings and the numerous boundary condition changes was not analyzed. Zhang et al. (2013) did show that the increase in ocean heat transport is small compared to the change in the AMOC and was not likely to be the direct cause of the North Atlantic warming. Furthermore, using a subset of the PlioMIP models they showed that the role of ocean heat flux in the models, in general, is not strongly correlated to either the strengthening of the Pliocene AMOC or the warming of the North Atlantic. We have now run a series of sensitivity tests with the newer version of the GISS model and will discuss the relative effects of Pliocene CO2, ice sheets (Greenland and Antarctica separately), orbit, vegetation and the change in the mesoscale mixing parameterization as a means of better understanding the role of various factors that

  5. The role of the North Atlantic Oscillation in European climate projections

    NASA Astrophysics Data System (ADS)

    Deser, Clara; Hurrell, James W.; Phillips, Adam S.

    2016-12-01

    This study highlights the expected range of projected winter air temperature and precipitation trends over the next 30-50 years due to unpredictable fluctuations of the North Atlantic Oscillation (NAO) superimposed upon forced anthropogenic climate change. The findings are based on a 40-member initial-condition ensemble of simulations covering the period 1920-2100 conducted with the Community Earth System Model version 1 (CESM1) at 1° spatial resolution. The magnitude (and in some regions, even the sign) of the projected temperature and precipitation trends over Europe, Russia and parts of the Middle East vary considerably across the ensemble depending on the evolution of the NAO in each individual member. Thus, internal variability of the NAO imparts substantial uncertainty to future changes in regional climate over the coming decades. To validate the model results, we apply a simple scaling approach that relates the margin-of-error on a trend to the statistics of the interannual variability. In this way, we can obtain the expected range of projected climate trends using the interannual statistics of the observed NAO record in combination with the model's radiatively-forced response (given by the ensemble-mean of the 40 simulations). The results of this observationally-based estimate are similar to those obtained directly from the CESM ensemble, attesting to the fidelity of the model's representation of the NAO and the utility of this approach. Finally, we note that the interannual statistics of the NAO and associated surface climate impacts are subject to uncertainty due to sampling fluctuations, even when based on a century of data.

  6. One regional ARM guide for climatic evaluation

    SciTech Connect

    Brown, R.M.

    1990-04-01

    One of the early tasks of the Atmospheric Radiation Measurements (ARM) Program is to provide climatic guides for site selection purposes including possible continental, regional, local and on-site locations. The first guide A Preliminary ARM Guide for Climatic Evaluations'' provided some climate data on a continental scale; this one is an attempt to show the variability that exists over a region. Kansas was chosen for this particular guide because it satisfies most of the requirements given in the ARM Program Plan, i.e., climatic significance, potential for synergism with other programs and scientific and logistical viability. Kansas has extreme climatic variations, is centrally located, is compatible with other large scale programs (Fife), has good airfields and accommodations to minimize time and effort in planning and operating an ARM site for continuous use and special campaigns.

  7. One regional ARM guide for climatic evaluation

    SciTech Connect

    Brown, R.M.

    1990-04-01

    One of the early tasks of the Atmospheric Radiation Measurements (ARM) Program is to provide climatic guides for site selection purposes including possible continental, regional, local and on-site locations. The first guide ``A Preliminary ARM Guide for Climatic Evaluations`` provided some climate data on a continental scale; this one is an attempt to show the variability that exists over a region. Kansas was chosen for this particular guide because it satisfies most of the requirements given in the ARM Program Plan, i.e., climatic significance, potential for synergism with other programs and scientific and logistical viability. Kansas has extreme climatic variations, is centrally located, is compatible with other large scale programs (Fife), has good airfields and accommodations to minimize time and effort in planning and operating an ARM site for continuous use and special campaigns.

  8. Relationship between the Pacific and Atlantic stepwise climate change during the 1990s

    NASA Astrophysics Data System (ADS)

    Chikamoto, Y.; Kimoto, M.; Watanabe, M.; Ishii, M.; Mochizuki, T.

    2012-11-01

    A linkage between climate change in the Atlantic and the Pacific oceans during the 1990s is investigated using three versions of the coupled climate model MIROC and CMIP5 multi-model ensemble. From the early 1990s to the early 2000s, the observed sea surface temperature (SST) shows warming in the North Atlantic and a La Niña-like pattern in the Pacific. Associated with the SST pattern, the observations indicate a strengthened Walker circulation in the tropical Pacific and enhanced precipitation in the tropical Atlantic. These SST and precipitation patterns are simulated well by hindcast experiments with external forcing and an initialized ocean anomaly state but are poorly simulated by uninitialized simulation with external forcing only. In particular, the observed La Niña-like SST pattern becomes prominent in ensemble members with large amplitudes of Atlantic Multidecadal Oscillation (AMO) index during 1996-1998. Our results suggest that ocean initialization in both the Pacific and the Atlantic plays an important role in predicting the Pacific stepwise climate change during the 1990s, which contributes to the accurate estimation of global temperature change in the coming decade. Forecasting typhoon frequency or marine fisheries production in the coming decade may be possible by improving the predictive skill of stepwise climate change.

  9. "Climate Matters Documoments": Enabling Regionally-Specific Climate Awareness

    NASA Astrophysics Data System (ADS)

    Keener, V. W.; Finucane, M.

    2012-12-01

    The Pacific Regional Integrated Sciences & Assessments (RISA) is a multidisciplinary program that enhances the ability of Pacific Island communities to understand, plan for, and adapt to climate-induced change. Using both social and physical science research methods, the Pacific RISA engages a network of regional decision-makers and stakeholders to help solve climate-related issues. Pacific RISA has a broad audience of local and regional decision-makers (i.e. natural resource managers, community planners, state and federal government agencies) and stakeholders (i.e. farmers and ranchers, fishermen, community and native islander groups). The RISA program engages with this audience through a mixed-method approach of two-way communication, including one-on-one interviews, workshops, consensus discussions and public presentations that allow us to tailor our efforts to the needs of specific stakeholders. A recent Pacific RISA project was the creation and production of four short, educational "documoment" videos that explore the different ways in which climate change in Hawaii affects stakeholders from different sectors. The documoments, generally titled "Climate Matters", start with a quote about why climate matters to each stakeholder: a rancher, a coastal hotel owner, the manager of a landfill, and the local branch of the National Weather Service. The narratives then have each stakeholder discussing how climate impacts their professional and personal lives, and describing the types of climate change they have experienced in the islands. Each video ends with a technical fact about how different climate variables in Hawaii (sea level, precipitation, ENSO) have actually changed within the last century of observational data. Freely available on www.PacificRISA.org, the Documoments have been viewed over 350 times, and have inspired similar video projects and received positive attention from different audiences of stakeholders and scientists. In other assessment work the

  10. The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean

    USGS Publications Warehouse

    Cronin, T. M.; Hayo, K.; Thunell, R.C.; Dwyer, G.S.; Saenger, C.; Willard, D.A.

    2010-01-01

    A new 2400-year paleoclimate reconstruction from Chesapeake Bay (CB) (eastern US) was compared to other paleoclimate records in the North Atlantic region to evaluate climate variability during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Using Mg/Ca ratios from ostracodes and oxygen isotopes from benthic foraminifera as proxies for temperature and precipitation-driven estuarine hydrography, results show that warmest temperatures in CB reached 16-17. ??C between 600 and 950. CE (Common Era), centuries before the classic European Medieval Warm Period (950-1100. CE) and peak warming in the Nordic Seas (1000-1400. CE). A series of centennial warm/cool cycles began about 1000. CE with temperature minima of ~. 8 to 9. ??C about 1150, 1350, and 1650-1800. CE, and intervening warm periods (14-15. ??C) centered at 1200, 1400, 1500 and 1600. CE. Precipitation variability in the eastern US included multiple dry intervals from 600 to 1200. CE, which contrasts with wet medieval conditions in the Caribbean. The eastern US experienced a wet LIA between 1650 and 1800. CE when the Caribbean was relatively dry. Comparison of the CB record with other records shows that the MCA and LIA were characterized by regionally asynchronous warming and complex spatial patterns of precipitation, possibly related to ocean-atmosphere processes. ?? 2010.

  11. The Challenge of Simulating the Regional Climate over Florida

    NASA Astrophysics Data System (ADS)

    Misra, V.; Mishra, A. K.

    2015-12-01

    In this study we show that the unique geography of the peninsular Florida with close proximity to strong mesoscale surface ocean currents among other factors warrants the use of relatively high resolution climate models to project Florida's hydroclimate. In the absence of such high resolution climate models we highlight the deficiencies of two relatively coarse spatial resolution CMIP5 models with respect to the warm western boundary current of the Gulf Stream. As a consequence it affects the coastal SST and the land-ocean contrast, affecting the rainy summer seasonal precipitation accumulation over peninsular Florida. We also show this through two sensitivity studies conducted with a regional coupled ocean atmosphere model with different bathymetries that dislocate and modulate the strength of the Gulf Stream that locally affects the SST in the two simulations. These studies show that a stronger and more easterly displaced Gulf Stream produces warmer coastal SST's along the Atlantic coast of Florida that enhances the precipitation over peninsular Florida relative to the other regional climate model simulation. However the regional model simulations indicate that variability of wet season rainfall variability in peninsular Florida becomes less dependent on the land-ocean contrast with a stronger Gulf Stream current.

  12. Clean Coal Technology: Region 4 Market Description, South Atlantic. Summary

    SciTech Connect

    Not Available

    1993-09-01

    The Region 4 Market Description Summary provides information that can be used in developing an understanding of the potential markets for clean coal technologies (CCTs) in the South Atlantic Region. This region (which geographically is Federal Region 4) consists of the following eight states: Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee. In order to understand the potential market. A description is provided of the region`s energy use, power generation capacity, and potential growth. Highlights of state government activities that could have a bearing on commercial deployment of CCTs are also presented. The potential markets characterized in this summary center on electric power generation by investor-owned, cooperative, and municipal electric utilities and involve planned new capacity additions and actions taken by utilities to comply with Phases I and II of the Clean Air Act Amendments (CAAA) of 1990. Regulations, policies, utility business strategies, and organizational changes that could impact the role of CCTs as a utility option are identified and discussed. The information used to develop the Region 4 Market Description is based mainly on an extensive review of plans and annual reports of 29 investor-owned, cooperative, and municipal coal-using electric utilities and public information on strategies and actions for complying with the CAAA of 1990.

  13. Impact of fluctuation of hydro-physical regime in the North Atlantic on the climate of Eurasia

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Anisimov, Mikhail; Byshev, Vladimir; Neiman, Victor; Romanov, Juri

    2015-04-01

    In the mid-1970s a heat content in the North Atlantic Ocean has substantially changed. Because of its high energy value the event appears to have a significant impact on the regional environment. To verify this suggestion we analyzed the global ocean-atmosphere data related to the negative (1950-1970) and positive (1980-1999) phases of the North Atlantic Oscillation (NAO). The analysis of these data have shown the existence of a thermal dipole in the North Atlantic upper layer which can be interpreted in a sense as an oceanic counterpart of atmospheric NAO. To identify this North Atlantic Dipole (NAD) its index was considered as the ocean 0-100-m layer temperature difference between regions (20°-40°N; 80°-30°W) and (50°-70°N; 60°-10°W). Then the NAD index was suggested a possible physical mechanism factor of the regional ocean-atmosphere system variability which in turn could produce a draw effect on the recent climate of Eurasia. The study showed that the current phase (2000-2013) of the climate in the North Atlantic region becomes qualitatively similar to the situation, typical for period 1950-1970, when the index of continentality in the Eurasian region was a very high. There is a reason to believe that in the coming decades this index is likely to increase, that would be primarily manifested by relatively cold weather in winters and by hot-dry summer seasons. To assess the variability of ocean heat content it was used a General Ocean Circulation model developed at the Institute of numerical mathematics, Russian Academy of Sciences. This model belongs to the class of σ-models, and its distinguishing feature is the splitting of the physical processes and spatial coordinates. By using the model there were performed numerical experiments for the evolution of hydrophysical regime of the North Atlantic Ocean at the period of 1958-2006, with a spatial resolution of 0.25°x0.25° for 25 horizons with time window of 1 hour. As initial conditions for the

  14. CLIMATE IMPACTS ON REGIONAL WATER

    EPA Science Inventory

    The New England region (including the 6 New England
    states plus upstate New York) offers a very diverse geography,
    matched by an equally diverse economy and human
    population. Livelihoods throughout the region are based
    on service industries that depend heavily on comm...

  15. Passive margin uplift around the North Atlantic region and its role in Northern Hemisphere late Cenozoic glaciation

    NASA Astrophysics Data System (ADS)

    Eyles, Nicholas

    1996-02-01

    Tectonic-climatic models of late Cenozoic global cooling emphasize the importance of middle latitude uplifts (e.g., Tibetan Plateau and the American west) but ignore widespread tectonic events on the margins of the North Atlantic Ocean. Pleistocene glaciations, after 2.5 Ma, are characterized by circum North Atlantic continental ice sheets that formed by the coalescence of perennial snow fields on extensive plateau surfaces in eastern Canada, northwest Britain, and Scandinavia. Plateaus record Cenozoic uplift of peneplains in response to semisynchronous magmatic underplating and thermal buoyancy of rifted continental margins. High-standing plateaus are very sensitive to small reductions in summer temperature. As late Cenozoic climate cooling proceeded, driven by uplift in regions external to the North Atlantic region, elevated plateaus became sites for extensive snow fields and ultimately ice sheets. Circum-Atlantic uplift took place in the key latitudinal belt that is most sensitive to orbitally forced changes in solar irradiation; this, together with albedo effects from large snow fields, could have amplified the relatively weak Milankovitch signal.

  16. Selecting global climate models for regional climate change studies.

    PubMed

    Pierce, David W; Barnett, Tim P; Santer, Benjamin D; Gleckler, Peter J

    2009-05-26

    Regional or local climate change modeling studies currently require starting with a global climate model, then downscaling to the region of interest. How should global models be chosen for such studies, and what effect do such choices have? This question is addressed in the context of a regional climate detection and attribution (D&A) study of January-February-March (JFM) temperature over the western U.S. Models are often selected for a regional D&A analysis based on the quality of the simulated regional climate. Accordingly, 42 performance metrics based on seasonal temperature and precipitation, the El Nino/Southern Oscillation (ENSO), and the Pacific Decadal Oscillation are constructed and applied to 21 global models. However, no strong relationship is found between the score of the models on the metrics and results of the D&A analysis. Instead, the importance of having ensembles of runs with enough realizations to reduce the effects of natural internal climate variability is emphasized. Also, the superiority of the multimodel ensemble average (MM) to any 1 individual model, already found in global studies examining the mean climate, is true in this regional study that includes measures of variability as well. Evidence is shown that this superiority is largely caused by the cancellation of offsetting errors in the individual global models. Results with both the MM and models picked randomly confirm the original D&A results of anthropogenically forced JFM temperature changes in the western U.S. Future projections of temperature do not depend on model performance until the 2080s, after which the better performing models show warmer temperatures.

  17. Selecting global climate models for regional climate change studies

    PubMed Central

    Pierce, David W.; Barnett, Tim P.; Santer, Benjamin D.; Gleckler, Peter J.

    2009-01-01

    Regional or local climate change modeling studies currently require starting with a global climate model, then downscaling to the region of interest. How should global models be chosen for such studies, and what effect do such choices have? This question is addressed in the context of a regional climate detection and attribution (D&A) study of January-February-March (JFM) temperature over the western U.S. Models are often selected for a regional D&A analysis based on the quality of the simulated regional climate. Accordingly, 42 performance metrics based on seasonal temperature and precipitation, the El Nino/Southern Oscillation (ENSO), and the Pacific Decadal Oscillation are constructed and applied to 21 global models. However, no strong relationship is found between the score of the models on the metrics and results of the D&A analysis. Instead, the importance of having ensembles of runs with enough realizations to reduce the effects of natural internal climate variability is emphasized. Also, the superiority of the multimodel ensemble average (MM) to any 1 individual model, already found in global studies examining the mean climate, is true in this regional study that includes measures of variability as well. Evidence is shown that this superiority is largely caused by the cancellation of offsetting errors in the individual global models. Results with both the MM and models picked randomly confirm the original D&A results of anthropogenically forced JFM temperature changes in the western U.S. Future projections of temperature do not depend on model performance until the 2080s, after which the better performing models show warmer temperatures. PMID:19439652

  18. Extreme storm activity in North Atlantic and European region

    NASA Astrophysics Data System (ADS)

    Vyazilova, N.

    2010-09-01

    The extreme storm activity study over North Atlantic and Europe includes the analyses of extreme cyclone (track number, integral cyclonic intensity) and extreme storm (track number) during winter and summer seasons in the regions: 1) 55°N-80N, 50°W-70°E; 2) 30°N-55°N, 50°W-70°E. Extreme cyclones were selected based on cyclone centre pressure (P<=970 mbar). Extreme storms were selected from extreme cyclones based on wind velocity on 925 mbar. The Bofort scala was used for this goal. Integral cyclonic intensity (for region) includes the calculation cyclone centers number and sum of MSLP anomalies in cyclone centers. The analyses based on automated cyclone tracking algorithm, 6-hourly MSLP and wind data (u and v on 925 gPa) from the NCEP/NCAR reanalyses from January 1948 to March 2010. The comparision of mean, calculated for every ten years, had shown, that in polar region extreme cyclone and storm track number, and integral cyclonic intensity gradually increases and have maximum during last years (as for summer, as for winter season). Every ten years means for summer season are more then for winter season, as for polar, as for tropical region. Means (ten years) for tropical region are significance less then for polar region.

  19. Integrating Climate Information and Decision Processes for Regional Climate Resilience

    NASA Astrophysics Data System (ADS)

    Buizer, James; Goddard, Lisa; Guido, Zackry

    2015-04-01

    An integrated multi-disciplinary team of researchers from the University of Arizona and the International Research Institute for Climate and Society at Columbia University have joined forces with communities and institutions in the Caribbean, South Asia and West Africa to develop relevant, usable climate information and connect it to real decisions and development challenges. The overall objective of the "Integrating Climate Information and Decision Processes for Regional Climate Resilience" program is to build community resilience to negative impacts of climate variability and change. We produce and provide science-based climate tools and information to vulnerable peoples and the public, private, and civil society organizations that serve them. We face significant institutional challenges because of the geographical and cultural distance between the locale of climate tool-makers and the locale of climate tool-users and because of the complicated, often-inefficient networks that link them. To use an accepted metaphor, there is great institutional difficulty in coordinating the supply of and the demand for useful climate products that can be put to the task of building local resilience and reducing climate vulnerability. Our program is designed to reduce the information constraint and to initiate a linkage that is more demand driven, and which provides a set of priorities for further climate tool generation. A demand-driven approach to the co-production of appropriate and relevant climate tools seeks to meet the direct needs of vulnerable peoples as these needs have been canvassed empirically and as the benefits of application have been adequately evaluated. We first investigate how climate variability and climate change affect the livelihoods of vulnerable peoples. In so doing we assess the complex institutional web within which these peoples live -- the public agencies that serve them, their forms of access to necessary information, the structural constraints

  20. Tropical climate variability: interactions across the Pacific, Indian, and Atlantic Oceans

    NASA Astrophysics Data System (ADS)

    Kajtar, Jules B.; Santoso, Agus; England, Matthew H.; Cai, Wenju

    2016-06-01

    Complex interactions manifest between modes of tropical climate variability across the Pacific, Indian, and Atlantic Oceans. For example, the El Niño-Southern Oscillation (ENSO) extends its influence on modes of variability in the tropical Indian and Atlantic Oceans, which in turn feed back onto ENSO. Interactions between pairs of modes can alter their strength, periodicity, seasonality, and ultimately their predictability, yet little is known about the role that a third mode plays. Here we examine the interactions and relative influences between pairs of climate modes using ensembles of 100-year partially coupled experiments in an otherwise fully coupled general circulation model. In these experiments, the air-sea interaction over each tropical ocean basin, as well as pairs of ocean basins, is suppressed in turn. We find that Indian Ocean variability has a net damping effect on ENSO and Atlantic Ocean variability, and conversely they each promote Indian Ocean variability. The connection between the Pacific and the Atlantic is most clearly revealed in the absence of Indian Ocean variability. Our model runs suggest a weak damping influence by Atlantic variability on ENSO, and an enhancing influence by ENSO on Atlantic variability.

  1. The importance of the South Atlantic high pressure system for the Tropical Atlantic annual cycle: experiments with a regionally coupled model

    NASA Astrophysics Data System (ADS)

    Cabos, William; Sein, Dmitry; Jacob, Daniela; Wang, Qiang; Jung, Thomas

    2014-05-01

    Conditions in the Tropical Atlantic (TA) are important for the climate in many regions. Because of this, it is important to simulate accurately the seasonal and interannual variability in this region. Currently, most of the coupled models suffer from serious biases in the TA. Identifying the causes of these biases is an important issue. Using a high-resolution fully coupled ocean-atmosphere regional model MPIOM- REMO (ROM) we explore the importance of the South Atlantic high pressure (SAH) for the simulated TA variability. In ROM a global ocean model with regionally high horizontal resolution is coupled to an atmospheric regional model and global terrestrial hydrology. The coupling is active in the region covered by REMO, whereas in the rest of the ocean its circulation is driven by prescribed atmospheric forcing without any feedbacks. Here we analyze two set of simulations that differ by the coupled area. In one of the setups, the atmospheric model domain includes the SAH, whereas in the second, the SAH is outside the region of active coupling. The first setup shows a much reduced warm bias in sea surface temperature (SST) in the warm pool and in the Angola-Bengela front. We analyze the contribution of the ocean and the atmosphere to these differences

  2. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.

    PubMed

    Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L

    2012-09-04

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition.

  3. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures

    PubMed Central

    Schmidt, Matthew W.; Chang, Ping; Hertzberg, Jennifer E.; Them, Theodore R.; Ji, Link; Otto-Bliesner, Bette L.

    2012-01-01

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256

  4. The Climate Shift and the Climate Variability in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Lopez Parages, Jorge; Rodriguez-Fonseca, Belen

    2010-05-01

    The so-called "climate shift" (CS) was defined at the beginning of the nineties as a dramatic change between 1976-77 in the basic state of the tropical Pacific and in the ENSO dynamics. Nowadays, the 1976-1977 shift is interpreted as a phase change in a decadal scale oscillation (the Pacific Decadal Oscillation, PDO, Mantua et al. 1997) lasting from about 1976 to 1988 (Trenberth and Hurrell 1994, Miller et al. 1994). However, several changes in the global climate have been reported after the CS; as changes in the air-sea interactions and in the tropical and extratropical teleconnection patterns. The climate variability of the Mediterranean area is influenced by the North Atlantic Oscillation (NAO, Hurrell, 2003), which frequency and positive phase intensity has suffered an increase after the CS unprecedented in the instrumental period, in coincidence with extreme drought conditions in the Mediterranean region. This results remark the non-stationary variability of the NAO (Vicente-Serrano and López-Moreno, 2008b) and the existence of changes in the underlying dynamics. In addition, Tropical Atlantic Variability (TAV) and ENSO have also shown to exhibit a strong and non- stationary influence in the Mediterranean basin, with maximum correlations at the beginning of the twenty century and since the CS (Mariotti et al. 2002), in concordance with the Atlantic Multidecadal Oscillation (AMO) evolution. A recent singular discovery show the influence of the Atlantic Niño on its Pacific counterpart (Rodríguez-Fonseca et al. 2009; Losada et al. 2009), a relation that was statistically pointed out in Polo et al. (2008a). These results remark the increasing importance of the TAV on the global climate and on the observed change, from the late 70's, in the global teleconnections. Although some studies point out the seasonal dependence of the leading modes of precipitation variability over Europe (Zveryaev, 2006), in this work, a gridded monthly terrestrial gauge

  5. A composite annual-resolution stalagmite record of North Atlantic climate over the last three millennia

    PubMed Central

    Baker, Andy; C. Hellstrom, John; Kelly, Bryce F. J.; Mariethoz, Gregoire; Trouet, Valerie

    2015-01-01

    Annually laminated stalagmites can be used to construct a precise chronology, and variations in laminae thickness provide an annual growth-rate record that can be used as a proxy for past climate and environmental change. Here, we present and analyse the first composite speleothem annual growth-rate record based on five stalagmites from the same cave system in northwest Scotland, where precipitation is sensitive to North Atlantic climate variability and the winter North Atlantic Oscillation (NAO). Our 3000-year record confirms persistently low growth-rates, reflective of positive NAO states, during the Medieval Climate Anomaly (MCA). Another persistently low growth period occurring at 290-550 CE coincides with the European Migration Period, and a subsequent period of sustained fast growth-rate (negative NAO) from 600-900 AD provides the climate context for the Viking Age in northern and western Europe. PMID:26068805

  6. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change.

  7. North Atlantic ocean circulation and abrupt climate change during the last glaciation

    NASA Astrophysics Data System (ADS)

    Henry, L. G.; McManus, J. F.; Curry, W. B.; Roberts, N. L.; Piotrowski, A. M.; Keigwin, L. D.

    2016-07-01

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ13C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean’s persistent, central role in abrupt glacial climate change.

  8. Climate impacts of regional SO2 emissions

    NASA Astrophysics Data System (ADS)

    Lamarque, J. F.; Fiore, A. M.; Shindell, D. T.

    2015-12-01

    Climate impacts of regional SO2 emissions J.-F. Lamarque, A. M. Fiore and D. Shindell In this talk, we present the analysis of constant -forcing present-day simulations pertaining to the perturbation of SO2 emissions over the United States and China. Using 3 chemistry-climate models (CESM, GFDL and GISS), we show that the removal of SO2 anthropogenic emissions over each region leads to significant (at the 95% or above; significance is also assessed relative to internal variability as determined from a 200-year control simulation with perpetual year 2000 conditions) perturbations in temperature over multiple regions of the Northern Hemisphere. While more limited, significant perturbations in regional precipitation are also found. While the overall (global and zonal means) forcing from Chinese emissions is similar to the US case, we found that the regional response to the emissions has different regional distributions.

  9. The Opening of the Arctic-Atlantic Gateway: Tectonic, Oceanographic and Climatic Dynamics - an IODP Initiative

    NASA Astrophysics Data System (ADS)

    Geissler, W. H.; Knies, J.; Nielsen, T.; Gaina, C.; Matthiessen, J. J.; Gebhardt, C.; Damm, V.; Forwick, M.; Hjelstuen, B. O.; Hopper, J. R.; Husum, K.; Laberg, J. S.; Kuerschner, W.; Morigi, C.; Schreck, M.; Tripati, A. K.; Vogt, C. M.; Rebesco, M.; Nam, S. I.; Carlson, A. E.; De Schepper, S.; Lucchi, R.; Mattingsdal, R.; Jokat, W.; Stein, R. H.

    2014-12-01

    The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with stepwise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The opening of the Drake Passage finalized the oceanographic isolation of Antarctica, some 40 Ma ago. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth's past and modern climate, little is known about its Cenozoic development. However, the opening history and AAG's consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic Ocean and the North Atlantic. To study the AAG's complete history, ocean drilling at two primary sites and one alternate site located between 73°N and 78°N are proposed. These sites will provide unprecedented sedimentary records that will unveil (1) the history of shallow-water exchange between the Arctic Ocean and the North Atlantic, and (2) the development of the AAG to a deep-water connection and its influence on the global climate system. The specific overarching goals of our proposal are to study: • the influence of distinct tectonic events in the development of the AAG and the formation of deep water passage on the North Atlantic and Arctic paleoceanography, and • the role of the AAG in the climate transition from the Paleogene greenhouse to the Neogene icehouse for the long-term (~50 Ma) climate history of the northern North Atlantic.

  10. COLLABORATIVE RESEARCH, MONITORING AND ASSESSMENT IN THE MID-ATLANTIC REGION

    EPA Science Inventory

    EPA Region 3 to implement a long-term research, monitoring, and assessment program in the Mid-Atlantic region - the Mid-Atlantic Integrated Assessment (MAIA). The MAIA mission is to develop a broad-based partnership to integrate scientific knowledge into the decision-making proc...

  11. Investigation of IPCC AR4 coupled climate model North Atlantic mode water formation

    NASA Astrophysics Data System (ADS)

    Carman, Jessie C.; McClean, Julie L.

    The formation of mode waters in the North Atlantic was examined in the suite of ocean models that comprise the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3). We constructed model climatologies for 1980-1999 from the 20th century simulations, and compared their mode water properties (temperature, salinity, formation rate, volume, turnover time, heat content) with data. In these models, we found biases in both the properties of the mode waters and their formation rates. For Subpolar Mode Water (SPMW), property biases principally involved salinity errors; additionally, some models form SPMW in an anomalous region west of the British Isles, shifting the source location of waters entering the overturning cell and altering the Nordic Seas' involvement in the Meridional Overturning Circulation. For Subtropical Mode Water (STMW), property biases involved both salinity and temperature errors, while positioning of heat and water fluxes relative to the Gulf Stream and northwest Sargasso Sea influenced STMW formation rate. Deficiencies in STMW formation rate and volume produced a turnover time of 1-2 years, approximately half of that observed; these variations in mode water bulk properties imply variation in ocean heat storage and advection, and hence deficiencies in all the models' abilities to adequately respond to changes in climatic forcing.

  12. Climate reconstruction for the last two millennia in central Iberia: The role of East Atlantic (EA), North Atlantic Oscillation (NAO) and their interplay over the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Sánchez-López, G.; Hernández, A.; Pla-Rabes, S.; Trigo, R. M.; Toro, M.; Granados, I.; Sáez, A.; Masqué, P.; Pueyo, J. J.; Rubio-Inglés, M. J.; Giralt, S.

    2016-10-01

    A multi-proxy characterization of the uppermost sedimentary infill of an Iberian alpine lake (Cimera, 2140 m a.s.l.) was performed to establish the climatic and environmental conditions for the Iberian Central Range (ICR) over the last two millennia. This multi-proxy characterization was used to reconstruct the intense runoff events, lake productivity and soil erosion in the lake catchment and interpret these factors in terms of temperature and precipitation variability. The Roman Period (RP; 200 BCE - 500 CE) beginning was characterized by an alternation between cold and warm periods as indicated by short-lived oscillations of intense runoff conditions and soil erosion, although warm conditions dominated the end of the period and the Early Middle Age (EMA; 500-900 CE) onset in the ICR. A noticeable decrease in intense runoff events and a progressive decrease in soil erosion during the late EMA indicated a shift to colder temperatures. In terms of precipitation, both the RP and EMA climate periods displayed a transition from dry to wet conditions that led to a decrease in lake productivity. The Medieval Climate Anomaly (MCA; 900-1300 CE) was characterized by warm and dry conditions with frequent intense runoff episodes and increases in lake productivity and soil erosion, whereas the Little Ice Age (LIA; 1300-1850 CE) showed the opposite characteristics. The Industrial Era (1850-2012 CE) presented an increase in lake productivity that likely demonstrates the influence of global warming. The spatio-temporal integration of the Cimera record with other Iberian reconstructions has been used to identify the main climate drivers over this region. During the RP and EMA, N-S and E-W humidity gradients were dominant, whereas during the MCA and LIA, these gradients were not evident. These differences could be ascribed to interactions between the North Atlantic Oscillation (NAO) and East Atlantic (EA) phases. During the RP, the general warm conditions and the E-W humidity

  13. A coupled regional climate-biosphere model for climate studies

    SciTech Connect

    Bossert, J.; Winterkamp, J.; Barnes, F.; Roads, J.

    1996-04-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project has been to develop and test a regional climate modeling system that couples a limited-area atmospheric code to a biosphere scheme that properly represents surface processes. The development phase has included investigations of the impact of variations in surface forcing parameters, meteorological input data resolution, and model grid resolution. The testing phase has included a multi-year simulation of the summer climate over the Southwest United States at higher resolution than previous studies. Averaged results from a nine summer month simulation demonstrate the capability of the regional climate model to produce a representative climatology of the Southwest. The results also show the importance of strong summertime thermal forcing of the surface in defining this climatology. These simulations allow us to observe the climate at much higher temporal and spatial resolutions than existing observational networks. The model also allows us to see the full three-dimensional state of the climate and thereby deduce the dominant physical processes at any particular time.

  14. Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal

    PubMed Central

    Jueterbock, Alexander; Tyberghein, Lennert; Verbruggen, Heroen; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

    2013-01-01

    The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600 km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or “unit” and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem. PMID:23762521

  15. Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal.

    PubMed

    Jueterbock, Alexander; Tyberghein, Lennert; Verbruggen, Heroen; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

    2013-05-01

    The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600 km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or "unit" and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem.

  16. Sulfate Aerosol Control of Tropical Atlantic Climate over the Twentieth Century

    NASA Technical Reports Server (NTRS)

    Chang, C.-Y.; Chiang, J. C. H.; Wehner, M. F.; Friedman, A. R.; Ruedy, R.

    2011-01-01

    The tropical Atlantic interhemispheric gradient in sea surface temperature significantly influences the rainfall climate of the tropical Atlantic sector, including droughts over West Africa and Northeast Brazil. This gradient exhibits a secular trend from the beginning of the twentieth century until the 1980s, with stronger warming in the south relative to the north. This trend behavior is on top of a multi-decadal variation associated with the Atlantic multi-decadal oscillation. A similar long-term forced trend is found in a multimodel ensemble of forced twentieth-century climate simulations. Through examining the distribution of the trend slopes in the multimodel twentieth-century and preindustrial models, the authors conclude that the observed trend in the gradient is unlikely to arise purely from natural variations; this study suggests that at least half the observed trend is a forced response to twentieth-century climate forcings. Further analysis using twentieth-century single-forcing runs indicates that sulfate aerosol forcing is the predominant cause of the multimodel trend. The authors conclude that anthropogenic sulfate aerosol emissions, originating predominantly from the Northern Hemisphere, may have significantly altered the tropical Atlantic rainfall climate over the twentieth century

  17. Ibero Atlantic Forested Wetlands: Plant-Abiotic Interactions at a Regional Scale

    NASA Astrophysics Data System (ADS)

    Gonzalez, P. R.; Ferreira, T.; Albuquerque, A.; Espirito-Santo, D.; Ramil-Rego, P.

    2005-05-01

    In biogeographical terms, forested wetlands are considered azonal ecosystems due to their special edaphic conditions. Duration of waterlogging decreases the effect of regional climate in vegetation communities. In this work we test this hypothesis by studying the relative contribution of spatial and environmental variation. Plant community composition and vertical structure were inventoried in inland forested wetlands along the Atlantic coast of the Iberian Peninsula. The study area ranges from latitude N 44° to 38° and includes Temperate and Mediterranean climate. Forested wetlands area was delimitated and sampled using plots where all the vascular plants and bryophytes were registered and their percentage cover estimated. Collected environmental regional variables included geographic, climatic, geologic and hydro geomorphologic data. Multivariate analysis was used to interpret species abundance data to assess the relative weight of environmental conditions and the spatial structure in the species data variation. Results of species-environment treatment revealed that tree overstorey species were determinant for vegetation types and that hydroperiod was the key abiotic variable classifying forested wetlands.

  18. Pesticides in surface water of the Mid-Atlantic region

    USGS Publications Warehouse

    Ferrari, Matthew J.; Ator, Scott W.; Blomquist, Joel D.; Dysart, Joel E.

    1997-01-01

    Water-quality data from 463 surface-water sites were compiled and analyzed to document the occurrence and distribution of pesticides in surface water of the Mid-Atlantic region as part of the Mid-Atlantic Integrated Assessment program of the U.S. Environmental Protection Agency. Those data collected by the U.S. Geological Survey from October 1973 through March 1997 were used in the analyses. Data are available for a large part of the Mid-Atlantic region, but large spatial gaps in the data do exist. USGS data bases contained analyses of surface-water samples for 127 pesticide compounds, including 12 degradates, but only 16 of the compounds were commonly detected. Atrazine, metolachlor, simazine, prometon, alachlor, tebuthiuron, cyanazine, diazinon, carbaryl, chlorpyrifos, pendimethalin, 2,4-D, dieldrin, DCPA, metribuzin, and desethylatrazine (an atrazine degradate) were detected in more than 100 of the samples analyzed. At least one pesticide was detected in about 75 percent of the samples collected and at more than 90 percent of the sites sampled. Concentrations greater than the Federal Maximum Contaminant Level (MCL) for drinking water of 3 micrograms per liter (ug/L) for atrazine were found in 67 of 2,076 samples analyzed; concentrations greater than the MCL of 2ug/L for alachlor were found in 13 of 1,693 samples analyzed, and concentrations greater than the MCL of 4 ug/L for simazine were found in 17 of 1,995 samples analyzed. Concentrations of four pesticides were greater than Federal Health Advisory levels for drinking water, and concentrations of nine pesticides were greater than Federal Ambient Water-Quality Criteria for the Protection of Aquatic Organisms. Streams draining basins with different land uses tend to have different pesticide detection frequencies and median concentrations. Median concentrations of herbicides tend to be highest in streams draining basins in which the major land use is agriculture, whereas median concentrations of insecticides

  19. Climatic variability between SST and river discharge at Amazon region

    NASA Astrophysics Data System (ADS)

    Silva, M. E.; Silva, E. R. L.

    2012-04-01

    Climatic variability, related both to precipitation and river discharge, has been associated to ocean variability. Authors commonly relate Pacific sea surface temperature (SST) variation to South America (SA) precipitation. Zonal displacement of Walker cell, with intensified subsidence over northern portion of SA, Subtropical Jet strengthening/weakening over extratropical latitudes of SA are, respectively, dynamical reasons scientifically accepted for increasing and depletion of precipitation at the respective areas. Many studies point out the influence of tropical Atlantic SST anomalies in relation to precipitation/river discharge variability over northeast of Brazil. Aliseos variability at tropical Atlantic is also a physic process that contributes to explain precipitation and river flow variability over SA, mainly over the north portion. In this study, we aim to investigate the temporal correlation between SST, mainly from Pacific and Atlantic oceans, and rivers discharge at the Amazon region. Ji-Parana, Madeira and Tapajós river discharge in monthly and annual scale, between 1968 and 2008, were the time series selected to reach the purpose. Time series for river discharge were obtained from Agência Nacional de Águas (ANA, in Portuguese) and, SST data were obtained from CDC/NOAA. Before linear correlation computations between river discharge and SST have been made, seasonal cycle and linear tendency were removed from all original time series. Areas better correlated to river discharge at Amazon region show oceanic patterns apparently associated to PDO (Pacific Decadal Oscillation) and ENSO (El Niño-South Oscillation) variability, with absolute values greater than 0.3 and reaching 0.5 or 0.6. The spatial pattern observed at Pacific basin is similar to that showed by the first mode of PCA (Principal Component Analysis), such seen in many studies (the "horse shoe" pattern). In general, negative correlation values appear far more to the west of Pacific basin

  20. Sensitivity of climate and Atlantic overturning circulation to uncertain ocean gateway configurations for the late Miocene

    NASA Astrophysics Data System (ADS)

    Bradshaw, C.; Lunt, D. J.; Flecker, R.; Martinez-Mendez, G.

    2013-12-01

    The palaeorecord documents late Miocene (11.6-5.3 Ma) climate to be much warmer and wetter than today yet CO2 reconstructions are similar to modern levels. Given the apparent decoupling between CO2 and warmth for this period we investigate here the role of the oceans. The late Miocene experienced significant tectonic change including the restriction of some of the last ocean gateways to close (Panama Gateway and Indonesian Seaway) and open (Bering Strait and Barents/Kara Sea). However, the timing and configuration of these tectonic changes is uncertain. The final closure of the Panama Gateway is dated to the Pliocene, but continental mammal exchange suggests the existence of a Central American archipelago from the mid-late Miocene. The Bering Strait is typically assumed to have opened at the very end of the late Miocene/early Pliocene based on diatom exchange, but other marine and terrestrial evidence points to a much earlier, perhaps intermittent, opening. The timing of the restriction of the Indonesian Seaway is very poorly constrained at middle Miocene to Pliocene. The Barents Sea and Kara Sea shelves are documented as having being subject to extensive glacial erosion and post-glacial uplift since the Pliocene and throughout the Quaternary but records of uplift and erosion during the earlier Cenozoic are limited. However, the presence of significant preglacial sediments suggests that this region underwent tectonic uplift, volcanism and subsequent erosion during the Eocene-Miocene period although the age assignment of the data remains controversial. The Panama Gateway has been suggested to influence North Atlantic Deep Water (NADW) production through numerous modelling studies, the Bering Strait has been suggested to greatly impact NADW during the Quaternary, and the strength of Indonesian Throughflow is hypothesised to influence Agulhas Leakage, which, in turn, has been speculated to influence Atlantic meridional overturning and thus NADW production. Here, we

  1. North Atlantic Meridional Overturning Circulation (AMOC) and Abrupt Climate Change through the Last Glaciation

    NASA Astrophysics Data System (ADS)

    Henry, G., III; McManus, J. F.; Curry, W. B.; Keigwin, L. D.; Giosan, L.

    2014-12-01

    The climate of the glacial North Atlantic was punctuated by catastrophic discharges of icebergs (Heinrich events), as well as by more mysterious, abrupt warming events associated with Dansgaard-Oeschger oscillations. These events are suspected to be related to changes in AMOC and its influence on heat transport and the regional and global heat budget. Investigation of these rapid oscillations is often limited by the resolution of sediment records. High accumulation rates at our study site (33.69°N, 57.58°W, 4583m water depth) on the Bermuda Rise allow improved resolution by one to two orders of magnitude. Cores CDH19 (38.81m) and CDH13 (36.70m), were recovered during KNR191, the initial deployment of the RV Knorr's long coring system developed at the Woods Hole Oceanographic Institution with support from the NSF. These cores contain high quality sediment sections that allow high resolution studies extending through the last glacial cycle at a key location for monitoring past oceanographic and climatic variability. Here we present detailed multi-proxy data from Bermuda Rise sediments reflecting deep ocean chemistry and dynamics of the last glaciation, and combine them with published data to produce a continuous, high resolution record spanning the last 70,000 years. CaCO3 burial fluxes, foraminifera stable isotopes, and sedimentary uranium-series disequilibria (including seawater-derived 231Pa /230Th), display coherent, complementary variability throughout the last glaciation. Glacial values in each proxy are consistent with reduced ventilation and overturning compared to the Holocene, with intervals that indicate substantial millennial reductions in each, and others when they briefly approach Holocene levels. In multiple instances, particularly spanning interstadials eight through twelve (IS8-IS12) our results are consistent with an abrupt, subcentennial acceleration in the export of excess 231Pa from the North Atlantic during stadial-interstadial transitions

  2. Robust features of Atlantic multi-decadal variability and its climate impacts

    NASA Astrophysics Data System (ADS)

    Ting, Mingfang; Kushnir, Yochanan; Seager, Richard; Li, Cuihua

    2011-09-01

    Atlantic Multi-decadal Variability (AMV), also known as the Atlantic Multi-decadal Oscillation (AMO), is characterized by a sharp rise and fall of the North Atlantic basin-wide sea surface temperatures (SST) on multi-decadal time scales. Widespread consequences of these rapid temperature swings were noted in many previous studies. Among these are the drying of Sahel in the 1960-70s and change in the frequency and intensity of Atlantic hurricanes on multi-decadal time scales. Given the short instrumental data records (about a century long) the central question is whether these climate fluctuations are robustly linked with the AMV and to what extent are these connections subject to changes in a changing climate. Here we address this issue by using the CMIP3 simulations for the 20th, 21st, and pre-industrial eras with 23 IPCC models. While models tend to produce AMV of shorter time scales and less periodic than suggested by the observations, the spatial structures of the SST anomaly patterns, and their association with worldwide precipitation, are surprisingly similar between models (with differing external forcing) and observations. Our results confirm the strong link between AMV and Sahel rainfall and suggest a clear physical mechanism for the linkage in terms of meridional shifts of the Atlantic ITCZ. The results also help clarify influences that may not be robust, such as the impacts over North America, India, and Australia.

  3. The Opening of the Arctic-Atlantic Gateway: Tectonic, Oceanographic and Climatic Dynamics - an IODP Initiative

    NASA Astrophysics Data System (ADS)

    Geissler, Wolfram; Knies, Jochen

    2016-04-01

    The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with stepwise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The opening of the Drake Passage finalized the oceanographic isolation of Antarctica, some 40 Ma ago. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth's past and modern climate, little is known about its Cenozoic development. However, the opening history and AAG's consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic Ocean and the North Atlantic. To study the AAG's complete history, ocean drilling at two primary sites and one alternate site located between 73°N and 78°N in the Boreas Basin and along the East Greenland continental margin are proposed. These sites will provide unprecedented sedimentary records that will unveil (1) the history of shallow-water exchange between the Arctic Ocean and the North Atlantic, and (2) the development of the AAG to a deep-water connection and its influence on the global climate system. The specific overarching goals of our proposal are to study: (1) the influence of distinct tectonic events in the development of the AAG and the formation of deep water passage on the North Atlantic and Arctic paleoceanography, and (2) the role of the AAG in the climate transition from the Paleogene greenhouse to the Neogene icehouse for the long-term (~50 Ma) climate history of the northern North Atlantic. Getting a continuous record of the

  4. Regional climate change and national responsibilities

    NASA Astrophysics Data System (ADS)

    Hansen, James; Sato, Makiko

    2016-03-01

    Global warming over the past several decades is now large enough that regional climate change is emerging above the noise of natural variability, especially in the summer at middle latitudes and year-round at low latitudes. Despite the small magnitude of warming relative to weather fluctuations, effects of the warming already have notable social and economic impacts. Global warming of 2 °C relative to preindustrial would shift the ‘bell curve’ defining temperature anomalies a factor of three larger than observed changes since the middle of the 20th century, with highly deleterious consequences. There is striking incongruity between the global distribution of nations principally responsible for fossil fuel CO2 emissions, known to be the main cause of climate change, and the regions suffering the greatest consequences from the warming, a fact with substantial implications for global energy and climate policies.

  5. Investigation into regional climate variability using tree-ring reconstruction, climate diagnostics and prediction

    NASA Astrophysics Data System (ADS)

    Barandiaran, Daniel A.

    This document is a summary of research conducted to develop and apply climate analysis tools toward a better understanding of the past and future of hydroclimate variability in the state of Utah. Two pilot studies developed data management and climate analysis tools subsequently applied to our region of interest. The first investigated the role of natural atmospheric forcing in the inter-annual variability of precipitation of the Sahel region in Africa, and found a previously undocumented link with the East Atlantic mode, which explains 29% of variance in regional precipitation. An analysis of output from an operational seasonal climate forecast model revealed a failure in the model to reproduce this linkage, thus highlighting a shortcoming in model performance. The second pilot study studied long-term trends in the strength of the Great Plains low-level jet, an driver of storm development in the region's wet spring season. Our analysis showed that since 1979 the low-level jet has strengthened as shifted the timing of peak activity, resulting in shifts both in time and location for peak precipitation, possibly the result of anthropogenic forcing. Our third study used a unique tree-ring dataset to create a reconstruction of April 1 snow water equivalent, an important measure of water supply in the Intermountain West, for the state of Utah to 1850. Analysis of the reconstruction shows the majority of snowpack variability occurs monotonically over the whole state at decadal to multidecadal frequencies. The final study evaluated decadal prediction performance of climate models participating in the Coupled Model Intercomparison Project 5. We found that the analyzed models exhibit modest skill in prediction of the Pacific Decadal Oscillation and better skill in prediction of global temperature trends post 1960.

  6. Response of the North Atlantic surface and intermediate ocean structure to climate warming of MIS 11

    PubMed Central

    Kandiano, Evgenia S.; van der Meer, Marcel T. J.; Schouten, Stefan; Fahl, Kirsten; Sinninghe Damsté, Jaap S.; Bauch, Henning A.

    2017-01-01

    Investigating past interglacial climates not only help to understand how the climate system operates in general, it also forms a vital basis for climate predictions. We reconstructed vertical stratification changes in temperature and salinity in the North Atlantic for a period some 400 ka ago (MIS11), an interglacial time analogue of a future climate. As inferred from a unique set of biogeochemical, geochemical, and faunal data, the internal upper ocean stratification across MIS 11 shows distinct depth-dependent dynamical changes related to vertical as well as lateral shifts in the upper Atlantic meridional circulation system. Importantly, transient cold events are recognized near the end of the long phase of postglacial warming at surface, subsurface, mid, and deeper water layers. These data demonstrate that MIS 11 coolings over the North Atlantic were initially triggered by freshwater input at the surface and expansion of cold polar waters into the Subpolar Gyre. The cooling signal was then transmitted downwards into mid-water depths. Since the cold events occurred after the main deglacial phase we suggest that their cause might be related to continuous melting of the Greenland ice sheet, a mechanism that might also be relevant for the present and upcoming climate. PMID:28393849

  7. Atmosphere Processes Dynamic and Mountain Region Climate

    NASA Astrophysics Data System (ADS)

    Davitashvili, T.; Khvedelidze, Z.; Javakhishvili, Kh.; Sharikadze, I.

    As is known, on the whole regional climate is depended on the Sun's lope relation to the horizon and the characteristics of the Earth relief. In the mountain regions (Caucasian region) compound relief conduce additional turbulence craetion and flow round stream increasing or decreasing. All that bring climate change special feature in the mountain regions. Climate formation and change internal factors are enough interconnected. We had study reverse connection between temperature, moisture, cloudness radiation balance, the Sun's activity and its components on the basis of the data over last 140 years. For the central months of the seasons, there was comparison day-night, monthly an annual motion of the radiation and temperature, temperature and Sun's activity, with account of cloud and moisture. Reverse connection between climate elements was valuated with help of correlation coefficient (r>0.8), but period of its reiteration analysis of the calculated fields the available natural data and the semiempirical calculation it was shown, that in the Western Georgia temperature was not increased unlike the Eastern Georgia.

  8. Different regional climatic drivers of Holocene large wildfires in boreal forests of northeastern America

    NASA Astrophysics Data System (ADS)

    Remy, Cécile C.; Hély, Christelle; Blarquez, Olivier; Magnan, Gabriel; Bergeron, Yves; Lavoie, Martin; Ali, Adam A.

    2017-03-01

    Global warming could increase climatic instability and large wildfire activity in circumboreal regions, potentially impairing both ecosystem functioning and human health. However, links between large wildfire events and climatic and/or meteorological conditions are still poorly understood, partly because few studies have covered a wide range of past climate-fire interactions. We compared palaeofire and simulated climatic data over the last 7000 years to assess causes of large wildfire events in three coniferous boreal forest regions in north-eastern Canada. These regions span an east-west cline, from a hilly region influenced by the Atlantic Ocean currently dominated by Picea mariana and Abies balsamea to a flatter continental region dominated by Picea mariana and Pinus banksiana. The largest wildfires occurred across the entire study zone between 3000 and 1000 cal. BP. In western and central continental regions these events were triggered by increases in both the fire-season length and summer/spring temperatures, while in the eastern region close to the ocean they were likely responses to hydrological (precipitation/evapotranspiration) variability. The impact of climatic drivers on fire size varied spatially across the study zone, confirming that regional climate dynamics could modulate effects of global climate change on wildfire regimes.

  9. Southern Hemisphere water mass conversion linked with North Atlantic climate variability.

    PubMed

    Pahnke, Katharina; Zahn, Rainer

    2005-03-18

    Intermediate water variability at multicentennial scales is documented by 340,000-year-long isotope time series from bottom-dwelling foraminifers at a mid-depth core site in the southwest Pacific. Periods of sudden increases in intermediate water production are linked with transient Southern Hemisphere warm episodes, which implies direct control of climate warming on intermediate water conversion at high southern latitudes. Coincidence with episodes of climate cooling and minimum or halted deepwater convection in the North Atlantic provides striking evidence for interdependence of water mass conversion in both hemispheres, with implications for interhemispheric forcing of ocean thermohaline circulation and climate instability.

  10. Abrupt climate fluctuations in the tropics: the influence of Atlantic Ocean circulation

    NASA Astrophysics Data System (ADS)

    Street-Perrott, F. Alayne; Perrott, R. Alan

    1990-02-01

    Several prolonged droughts in the Sahel and tropical Mexico during the past 14,000 years were coincident with large injections of fresh water into the northern North Atlantic Ocean. The link between these phenomena lies in the thermohaline circulation of the oceans: input of fresh water decreases salinity leading to reduced North Atlantic Deep Water formation and anomalies of sea surface temperature of the kind associated with decreased rainfall in the northern tropics. Ice-sheet disintegration, the most important source of fresh-water input to the oceans, should therefore be considered explicitly in models of past and future climate.

  11. Combined influences of seasonal East Atlantic Pattern and North Atlantic Oscillation to excite Atlantic multidecadal variability in a climate model

    NASA Astrophysics Data System (ADS)

    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

  12. A Subtropical North Atlantic Regional Atmospheric Moisture Budget

    NASA Astrophysics Data System (ADS)

    Bingham, F.; D'Addezio, J. M.

    2014-12-01

    The synergistic effects of evaporation (E), precipitation (P), and Ekman transport make the SPURS (Salinity Processes in the Upper Ocean Regional Study) region in the subtropical North Atlantic (15-30°N, 30-45°W) the ideal location for the world's highest open ocean sea surface salinity. Using the MERRA and ERA-Interim atmospheric reanalyses, we reproduce the mean hydrologic state of the atmosphere over the SPURS region since 1979 and roughly deduce the change in salinity across the meridional domain due solely to interactions between E-P and Ekman transport. Our findings suggest a region that is highly evaporative at a mean rate of 4.87 mm/day with a standard deviation of 1.2 mm/day and little seasonality. Precipitation is much more variable with an annual fall maximum around 3 mm/day but only a mean rate of 1.37 mm/day with a standard deviation of 1.46 mm/day. The resulting E-P variable has a mean rate of 3.50 mm/day with a standard deviation of 1.92 mm/day and matches well with the moisture flux divergence term although the former is typically larger by a small margin. Strong prevailing easterly trade winds generate northward Ekman transports that advect water northward to the salinity maximum around 25°N. A short calculation shows that atmospheric moisture dynamics could potentially account for almost half of the change in salinity between 15°N and 25°N giving an estimate of the role that surface freshwater flux plays in the maintenance of the salinity maximum.

  13. A subtropical North Atlantic regional atmospheric moisture budget

    NASA Astrophysics Data System (ADS)

    D'Addezio, Joseph M.; Bingham, Frederick M.

    2014-12-01

    The synergistic effects of evaporation (E), precipitation (P), and Ekman transport make the Salinity Processes in the Upper Ocean Regional Study (SPURS-1) region in the subtropical North Atlantic (15-30°N, 30-45°W) the natural location for the world's highest open ocean SSS maximum. Using the MERRA and ERA-Interim atmospheric reanalyses, we reproduce the mean hydrologic state of the atmosphere over the SPURS-1 region since 1979 and roughly deduce the change in salinity across the meridional domain due solely to interactions between E-P and Ekman transport. Our findings suggest a region that is highly evaporative at a mean rate of 4.87 mm/d with a standard deviation of 1.2 mm/d and little seasonality. Precipitation is much more variable with an annual fall maximum around 3 mm/d but only a mean rate of 1.37 mm/d with a standard deviation of 1.46 mm/d. The resulting E-P variable has a mean rate of 3.50 mm/d with a standard deviation of 1.92 mm/d and matches well with the moisture flux divergence term although the former is typically larger by a small margin. Strong prevailing easterly trade winds generate northward Ekman transports that advect water toward the salinity maximum around 25°N. A short calculation shows that atmospheric moisture dynamics could potentially account for about one third of the change in salinity between 15°N and 25°N giving an estimate of the role that surface freshwater flux plays in the maintenance of the salinity maximum.

  14. Detection and Attribution of Regional Climate Change

    SciTech Connect

    Bala, G; Mirin, A

    2007-01-19

    We developed a high resolution global coupled modeling capability to perform breakthrough studies of the regional climate change. The atmospheric component in our simulation uses a 1{sup o} latitude x 1.25{sup o} longitude grid which is the finest resolution ever used for the NCAR coupled climate model CCSM3. Substantial testing and slight retuning was required to get an acceptable control simulation. The major accomplishment is the validation of this new high resolution configuration of CCSM3. There are major improvements in our simulation of the surface wind stress and sea ice thickness distribution in the Arctic. Surface wind stress and ocean circulation in the Antarctic Circumpolar Current are also improved. Our results demonstrate that the FV version of the CCSM coupled model is a state of the art climate model whose simulation capabilities are in the class of those used for IPCC assessments. We have also provided 1000 years of model data to Scripps Institution of Oceanography to estimate the natural variability of stream flow in California. In the future, our global model simulations will provide boundary data to high-resolution mesoscale model that will be used at LLNL. The mesoscale model would dynamically downscale the GCM climate to regional scale on climate time scales.

  15. Ekman transport and upwelling during Younger Dryas estimated from wind stress from GENESIS Climate model experiments with variable North Atlantic heat convergence

    NASA Astrophysics Data System (ADS)

    Ágústsdóttir, Anna María; Alley, Richard B.; Pollard, David; Peterson, William H.

    Reconstructed climatic changes during the Younger Dryas interval are similar to, but somewhat larger and more wide-spread than, those expected based on the direct atmospheric effects of reduced North Atlantic oceanic heat transport. The paleoclimatic data show that North Atlantic cooling during the Younger Dryas was accompanied by stronger winds in many regions, suggesting that enhanced wind-driven ocean upwelling may have served as a positive feedback on the cooling. We test this hypothesis using the GENESIS atmospheric general circulation model, and find that Younger Dryas-age specified reduction in North Atlantic oceanic heat transport increases tropical Ekman divergence by ≈10% in regions and at times of prominent upwelling, sufficient to affect tropical temperatures.

  16. Contrasted climatic trends in the Atlantic vs. Pacific gateways of the Arctic Ocean during the Holocene

    NASA Astrophysics Data System (ADS)

    de Vernal, A.; Hillaire-Marcel, C.; Rochon, A.

    2013-12-01

    The reconstruction of sea-surface conditions including sea ice cover was undertaken based on about 20 marine sediment cores collected in the Arctic Ocean and subarctic seas. The approach has been standardized and mostly relies on the modern analogue technique applied to dinoflagellate cyst assemblages, which permit simultaneous estimates of sea ice cover, summer sea-surface temperature and salinity. The results show some regionalism in both trends, amplitude and overall variability. In general, changes of small amplitude are recorded in the Canadian Arctic whereas a slight cooling trend with an increasing sea ice cover characterizes the Northern Baffin Bay and Fram Strait areas from mid to late Holocene. In contrast, the Chukchi Sea records show large amplitude variations with millennial pacing making difficult to define any trend. The Chukchi Sea data indicate reduced sea ice and warmer conditions during the mid-Holocene, notably around 6.5 and 3.5 ka, and also point to important variations during the last millennium. The overall results suggest a higher variability thus sensitivity to climate change, in the Chukchi Sea area than in the Eastern parts of the Arctic and subarctic regions, which are largely influenced by northern branches of the North Atlantic Drift. The climate sensitivity of the Chukchi Sea area may be related to the proximity of the Pacific gateway. Strong linkages between sea-surface conditions, sea ice cover and export rate seem tightly linked there with large scale atmospheric synopses in the North Pacific and possibly the tropical Pacific. The apparent consistency of the Mount Logan record (Fisher et al., the Holocene 2008) with those of the Chukchi Sea (de Vernal et al., Quat. Sci. Rev. 2013) tends to support the hypothesis of a strong influence of North Pacific atmospheric teleconnections on sea-surface conditions in the Western Arctic.

  17. Regional Actions to Address Climate Change Impacts on Water

    EPA Pesticide Factsheets

    EPA's ten regions work to address climate change on a local level, implementing regionally important solutions and working with stakeholders on the ground. Many regional partners work closely with EPA to better implement climate solutions

  18. Atlantic and Pacific Influences on Mesoamerican Climate Over the Past Millennium (Invited)

    NASA Astrophysics Data System (ADS)

    Stahle, D. W.; Burnette, D. J.; Villanueva, J.; Cleaveland, M. K.

    2010-12-01

    Montezuma baldcypress (Taxodium mucronatum) trees in Queretaro have been used to develop the first exactly dated millennium-long tree-ring chronology in central Mexico. The chronology is sensitive to both precipitation and temperature, and has been used to reconstruct the Palmer Drought Severity Index (PDSI) for June from AD 771-2008 for a large sector of Mesoamerica (most of central and southern Mexico). Fourier-transform spectral analyses of the 1,238-year long reconstruction indicate strong concentrations of variance at frequencies associated with the El Nino/Southern Oscillation (ENSO; representing over 14% of the total reconstructed variance between periods of 4.5 and 5.5 years), and at multi-decadal frequencies potentially associated with the Atlantic Multidecadal Oscillation (AMO; representing over 10% of the total variance between periods of 50 and 75 years). Weaker but statistically significant concentrations of variance are also detected with the Multi-Taper Method of spectral analysis at subdecadal timescales potentially linked with the North Atlantic Oscillation (NAO; 7.5 years) and at timescales possibly associated with the Pacific Decadal Oscillation (~33 years). The reconstruction is significantly correlated with sea surface temperatures (SST) in the ENSO cold tongue region from 1871-2008 (during the boreal cool season, DJFM), and this SST correlation strengthens in the 20th Century (1931-2008). Summer drought tends to develop over central Mexico during El Nino events, and the record warm events observed in 1983 and 1998 were associated with the two most extremely dry June PDSI conditions in the past 1,238 years (reconstructed ranks 1 and 2 for 1983 and 1998, respectively). The reconstruction is also significantly correlated with SSTs over the tropical North Atlantic, and is coherent with long instrument-based indices of the NAO at periods near 7.5 years, but only during the 20th century. The June PDSI reconstruction is coherent (P<0.05) with a 600

  19. Warm water events in the southeast Atlantic and their impact on regional and large-scale atmospheric conditions in the CMIP5 model output

    NASA Astrophysics Data System (ADS)

    Ott, Irena; Lutz, Karin; Rathmann, Joachim; Jacobeit, Jucundus

    2013-04-01

    Two types of El Niño-like events are described in the South Atlantic: the Atlantic Niño in the equatorial Atlantic and the Benguela Niño off the Namibian and Angolan coast. These warm water events are known to be associated with rainfall anomalies at the West and Southwest African coastal region and harm marine ecosystems and fish populations. The two phenomena are handled separately so far, but the identification of warm water events in our study - via similar variabilities of sea surface temperatures (SST) - based on observed SST data (HadISST1.1) as well as global climate model output from CMIP5, involved the definition of an area mean index that includes both Niño types from the Atlantic region. A multi-model ensemble of the CMIP5 output is used to investigate the impact of Atlantic Niño events on regional atmospheric conditions. Based on the Atlantic SST index, composite analyses give information about anomalous precipitation, air pressure, humidity, evaporation, horizontal wind and vertical air motion patterns over the African continent and the South Atlantic. The Atlantic variability mode is similar to the Pacific El Niño system, but more irregular and less intense. However, recent studies show that the Atlantic influences the El Niño Southern Oscillation (ENSO) in the Pacific Ocean by the modification of the Walker and Hadley circulations and associated wind stress, thermocline and SST anomalies, further amplified by the Bjerknes positive feedback. As a result, an Atlantic Niño is followed by a La Niña-like phenomenon in the Pacific area with a lag of six months. In our study, the CMIP5 output is considered with respect to its ability of describing the complex connection between the Atlantic and Pacific variability modes. For that purpose, the inter-ocean teleconnection is studied with correlation analyses of the ensemble members of the CMIP5 output by means of the Atlantic index, the Southern Oscillation (SOI) and the Pacific El Niño indices (Ni

  20. HISTORICAL CHANGES IN GLOBAL SCALE CIRCULATION PATTERNS, MID-ATLANTIC CLIMATE STREAM FLOW AND NUTRIENT FLUXES TO THE CHESAPEAKE BAY

    EPA Science Inventory

    The rate of change in Northern Hemisphere temperature in the past century strongly suggests that we are now in a period of rapid global climate change. Also, the climate in the mid-Atlantic is quite sensitive to larger scale climate variation, which affects the frequency and seve...

  1. Sensitivity of the North Atlantic Basin to cyclic climatic forcing during the early Cretaceous

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.

    1999-01-01

    Striking cyclic interbeds of laminated dark-olive to black marlstone and bioturbated white to light-gray limestone of Neocomian (Early Cretaceous) age have been recovered at Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) sites in the North Atlantic. These Neocomian sequences are equivalent to the Maiolica Formation that outcrops in the Tethyan regions of the Mediterranean and to thick limestone sequences of the Vocontian Trough of France. This lithologic unit marks the widespread deposition of biogenic carbonate over much of the North Atlantic and Tethyan seafloor during a time of overall low sealevel and a deep carbonate compensation depth. The dark clay-rich interbeds typically are rich in organic carbon (OC) with up to 5.5% OC in sequences in the eastern North Atlantic. These eastern North Atlantic sequences off northwest Africa, contain more abundant and better preserved hydrogen-rich, algal organic matter (type II kerogen) relative to the western North Atlantic, probably in response to coastal upwelling induced by an eastern boundary current in the young North Atlantic Ocean. The more abundant algal organic matter in sequences in the eastern North Atlantic is also expressed in the isotopic composition of the carbon in that organic matter. In contrast, organic matter in Neocomian sequences in the western North Atlantic along the continental margin of North America has geochemical and optical characteristics of herbaceous, woody, hydrogen-poor, humic, type III kerogen. The inorganic geochemical characteristics of the dark clay-rich (80% CaCO3) interbeds in both the eastern and western basins of the North Atlantic suggest that they contain minor amounts of relatively unweathered eolian dust derived from northwest Africa during dry intervals.

  2. Ice-Sheet Dynamics and Millennial-Scale Climate Variability in the North Atlantic across the Middle Pleistocene Transition (Invited)

    NASA Astrophysics Data System (ADS)

    Hodell, D. A.; Nicholl, J.

    2013-12-01

    During the Middle Pleistocene Transition (MPT), the climate system evolved from a more linear response to insolation forcing in the '41-kyr world' to one that was decidedly non-linear in the '100-kyr world'. Smaller ice sheets in the early Pleistocene gave way to larger ice sheets in the late Pleistocene with an accompanying change in ice sheet dynamics. We studied Sites U1308 (49° 52.7'N, 24° 14.3'W; 3871 m) and U1304 (53° 3.4'N, 33° 31.8'W; 3024 m) in the North Atlantic to determine how ice sheet dynamics and millennial-scale climate variability evolved as glacial boundary conditions changed across the MPT. The frequency of ice-rafted detritus (IRD) in the North Atlantic was greater during glacial stages prior to 650 ka (MIS 16), reflecting more frequent crossing of an ice volume threshold when the climate system spent more time in the 'intermediate ice volume' window, resulting in persistent millennial scale variability. The rarity of Heinrich Events containing detrital carbonate and more frequent occurrence of IRD events prior to 650 ka may indicate the presence of 'low-slung, slippery ice sheets' that flowed more readily than their post-MPT counterparts (Bailey et al., 2010). Ice volume surpassed a critical threshold across the MPT that permitted ice sheets to survive boreal summer insolation maxima, thereby increasing ice volume and thickness, lengthening glacial cycles, and activating the dynamical processes responsible for Laurentide Ice Sheet instability in the region of Hudson Strait (i.e., Heinrich events). The excess ice volume during post-MPT glacial maxima provided a large, unstable reservoir of freshwater to be released to the North Atlantic during glacial terminations with the potential to perturb Atlantic Meridional Overtunring Circulation. We speculate that orbital- and millennial-scale variability co-evolved across the MPT and the interaction of processes on orbital and suborbital time scales gave rise to the changing patterns of glacial

  3. Satellite-based climate information within the WMO RA VI Regional Climate Centre on Climate Monitoring

    NASA Astrophysics Data System (ADS)

    Obregón, A.; Nitsche, H.; Körber, M.; Kreis, A.; Bissolli, P.; Friedrich, K.; Rösner, S.

    2014-05-01

    The World Meteorological Organization (WMO) established Regional Climate Centres (RCCs) around the world to create science-based climate information on a regional scale within the Global Framework for Climate Services (GFCS). The paper introduces the satellite component of the WMO Regional Climate Centre on Climate Monitoring (RCC-CM) for Europe and the Middle East. The RCC-CM product portfolio is based on essential climate variables (ECVs) as defined by the Global Climate Observing System (GCOS), spanning the atmospheric (radiation, clouds, water vapour) and terrestrial domains (snow cover, soil moisture). In the first part, the input data sets are briefly described, which are provided by the EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) Satellite Application Facilities (SAF), in particular CM SAF, and by the ESA (European Space Agency) Climate Change Initiative (CCI). In the second part, the derived RCC-CM products are presented, which are divided into two groups: (i) operational monitoring products (e.g. monthly means and anomalies) based on near-real-time environmental data records (EDRs) and (ii) climate information records (e.g. climatologies, time series, trend maps) based on long-term thematic climate data records (TCDRs) with adequate stability, accuracy and homogeneity. The products are provided as maps, statistical plots and gridded data, which are made available through the RCC-CM website (www.dwd.de/rcc-cm).

  4. Simulation by CMIP5 models of the atlantic multidecadal oscillation and its climate impacts

    NASA Astrophysics Data System (ADS)

    Han, Zhe; Luo, Feifei; Li, Shuanglin; Gao, Yongqi; Furevik, Tore; Svendsen, Lea

    2016-12-01

    This study focuses on the climatic impacts of the Atlantic Multidecadal Oscillation (AMO) as a mode of internal variability. Given the difficulties involved in excluding the effects of external forcing from internal variation, i.e., owing to the short record length of instrumental observations and historical simulations, we assess and compare the AMO and its related climatic impacts both in observations and in the "Pre-industrial" experiments of models participating in CMIP5. First, we evaluate the skill of the 25 CMIP5 models' "Historical" simulations in simulating the observational AMO, and find there is generally a considerable range of skill among them in this regard. Six of the models with higher skill relative to the other models are selected to investigate the AMO-related climate impacts, and it is found that their "Pre-industrial" simulations capture the essential features of the AMO. A positive AMO favors warmer surface temperature around the North Atlantic, and the Atlantic ITCZ shifts northward leading to more rainfall in the Sahel and less rainfall in Brazil. Furthermore, the results confirm the existence of a teleconnection between the AMO and East Asian surface temperature, as well as the late withdrawal of the Indian summer monsoon, during positive AMO phases. These connections could be mainly caused by internal climate variability. Opposite patterns are true for the negative phase of the AMO.

  5. 600 yr High-Resolution Climate Reconstruction of the Atlantic Multidecadal Oscillation deduced from a Puerto Rican Speleothem

    NASA Astrophysics Data System (ADS)

    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

  6. Probabilistic Predictions of Regional Climate Change

    NASA Astrophysics Data System (ADS)

    Harris, G. R.; Sexton, D. M.; Booth, B. B.; Brown, K.; Collins, M.; Murphy, J. M.

    2009-12-01

    We present a methodology for quantifying the leading sources of uncertainty in climate change projections that allows more robust prediction of probability distribution functions (PDFs) for transient regional climate change than is possible, for example, with the multimodel ensemble in the the CMIP3 archive used for the IPCC Fourth Assessment. Uncertainty in equilibrium climate response has been systematically explored by varying uncertain parameters in the atmosphere, sea-ice and surface components in a ensemble of simulations with the third version of the Hadley Centre model coupled to a slab ocean. The ensemble is used to emulate the response for one million parameter combinations, ensuring robust prediction of the prior distributions of equilibrium response for this model. Posterior PDFs are estimated using a weighting scheme that calculates the likelihood for each model version, based upon its ability to reproduce a large set of observed seasonal-mean climate variables. Information from the CMIP3 simulations is used to assess the effect of structural uncertainty, and this is included as an additional variance in the weighting. The posterior distributions of equilibrium response are shown to be relatively robust to variation in key assumptions of the method. A time-scaling technique that maps equilibrium to transient change is then used to predict PDFs for transient regional climate change for specified emissions scenarios. The scaling uses a simple climate model (SCM), with global climate feedbacks and local response sampled from the equilibrium response, and other SCM parameters tuned to the response of other AOGCM ensembles. Use of the SCM allows efficient sampling of uncertainties not fully sampled by expensive GCM simulation, including uncertainty in aerosol radiative forcing, the rate of ocean heat uptake, and the strength of carbon-cycle feedbacks. Uncertainties arising from statistical components of the method, such as emulation or scaling, are

  7. Origin of millennial-scale climate signals in the subtropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Billups, K.

    2011-12-01

    In this study, I am testing the hypothesis that millennial-scale climate signals in the northwestern subtropical Atlantic are linked to external driving factors such as the harmonics of precession. The test is based on the observation that the precession period is not stationary through time. For example, between 900 and 340 Ka the time interval between successive precession minima (or maxima) ranges primarily from 17 kyr to 21 kyr with discrete intervals lasting up to ~30 kyr (spectral power centered on the 23 kyr and 19 kyr periodicities). After 340 Ka, however, precession minima (or maxima) consistently occur at longer intervals, between 21 kyr and 25 kyr (spectral power focused at the 23 kyr period). If in proxy records millennial-scale variations reflect the harmonics of precession, I expect that the millennial-scale periodicity associated with the 19 kyr precession period (e.g., the 4.8 kyr peak) loses power as the primary orbital peak loses power at 340 Ka. First order tests of this idea can be made using published planktic foraminiferal δ18O records from ODP Site 1059 (Hagen and Keigwin, 2002; Oppo et al., 2001) in the northwestern subtropical Atlantic spanning Marine Isotope Stages 2-6 (~20-150 Ka) and Site 1058 spanning MIS 12-22 (~450-900 Ka, Weirauch et al., 2008). After filtering the records to remove the 100 kyr cycle, the older time slice contains both precession peaks (23 and 19 kyr). Significant (95% confidence interval) suborbital peaks occur at 12 kyr, 5.7 kyr and 5.0 kyr, which are close to the periodicities of the expected harmonics. The younger time slice shows only one precession peak centered at ~23 kyr and significant (95% confidence interval) sub-orbital peaks at 11.2 kyr, and 5 kyr. Only the 11.2 kyr peak agrees with the expected period of the second harmonic of the 23 kyr precession peak. We are currently generating high resolution planktic foraminiferal stable isotope records in this region to span MIS 7, which, together with data from

  8. Last Glacial - Holocene climate variability in the Atlantic sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Xiao, Wenshen; Esper, Oliver; Gersonde, Rainer

    2016-03-01

    The Southern Ocean plays a major role in the glacial/interglacial global carbon cycle. However, there is a substantial lack of information from its Antarctic Zone south of the Polar Front (PF) to understand key climate processes (e.g., sea ice variability, productivity changes, CO2 source region, shifts of the Southern Westerly Wind) active in this region during the glacial/interglacial transition, due to the limited high-resolution sediment records from this area. To close this gap, we investigated high resolution diatom records from a series of sediment cores from the Atlantic and Western Indian sectors of the Southern Ocean between the modern PF and the Winter Sea Ice (WSI) edge. Summer Sea Surface Temperature (SSST) and sea ice information spanning the past 30 thousand years were derived from diatom transfer functions and indicators, which augment comprehensive information on past surface ocean conditions and related ocean and atmospheric circulation, as well as opal deposition. These complementary lines of evidences also provide important environmental boundary conditions for climate simulations understanding the past climate development in the high latitudes Southern Ocean. Our reconstructions show that the Last Glacial (LG) SSSTs south of the modern PF are 1-3 °C colder than modern conditions, WSI expanded to the modern PF. Our data suggests effective carbon export in the Antarctic Zone during the LG. Deglacial two steps of warming support the bipolar seesaw mechanism. Antarctic Zone is an important source region for the CO2 deglacial increase. The warming was more suppressed towards south, due to continuous ice discharge from Antarctica. The SSSTs exceeded modern values during the early Holocene optimum, when WSI extent probably retreated south of its modern position. The southern boundary of maximum opal deposition zone may have shifted to south of 55°S in the Bouvet Island area at this time. The mid-late Holocene cooling with WSI re-expanding to the

  9. Climate variability and wine quality over Portuguese regions

    NASA Astrophysics Data System (ADS)

    Gouveia, Célia M.; Gani, Érico A.; Liberato, Margarida L. R.

    2015-04-01

    The relationship between the characteristics of wine and its geographic origin is frequently used to explain the hierarchy of high-quality wines. Port wine is produced from grapes grown in selected areas of the Douro valley, in Portugal, the so-called Região Demarcada do Douro, the first wine-producing region of the world (dating from 1758). The Douro region presents distinctive climatic, topographic and soil characteristics. Moreover Portugal possesses a large array of native varietals, producing an abundant diversity of different wines. The most protected wines, produced only with some authorised grape varietals in the demarcated regions, are labelled D.O.C. (Denominação de Origem Controlada, similar to the French Appellation d'Origine Contrôlée (AOC)) which secures a superior wine quality. Recent warming trends in Portugal are associated with the significant increase in the frequency and duration of heat waves, and the increase in the frequency of hot days and tropical nights, especially in spring and summer, together with a significant decrease in the frequency of cold waves and frost days (Santo et al., 2014). Moreover a predominantly negative tendency in precipitation indices was also found (de Lima et al., 2014). These trends and associated changes in temperature and precipitation regimes may exert strong influences on agriculture systems. In this work we have performed an analysis of the distinct behaviour of several meteorological fields in vintage versus non-vintage years for Port Wine on one hand and Alentejo and Dão/Bairrada DOC regions on the other hand, during the period spanning from 1964-1995. The relative importance of maximum and minimum temperature, precipitation and frost days is assessed for each individual month of the vegetative cycle and their importance to the wine quality is evaluated. Furthermore, composites of 500 hPa geopotential height and sea level pressure fields over the Euro Atlantic region are also compared for years

  10. North Atlantic Tropical Cyclone Activity over the last 2000 years: Patterns, Consequences and Potential Climatic Forcing

    NASA Astrophysics Data System (ADS)

    Donnelly, J. P.; Lane, P.; Hawkes, A.; van Hengstum, P. J.; Ranasinghe, P. N.; Toomey, M.; MacDonald, D.

    2011-12-01

    1300 years ago. A reconstruction of intense hurricane landfalls from the Gulf coast documents some similar patterns that likely point to large scale climate forcing; however, some significant differences are evident. For example, the Gulf frequently experienced intense hurricanes during the 13th and 14th centuries, but a subsequent decline in activity has persisted through the historic period. This antiphasing of intense hurricane activity between the East and Gulf coasts may point to basin-wide changes in hurricane tracks, but regional controls on the frequency of intense hurricanes (e.g., loop current penetration in the Gulf of Mexico) may also have driven spatial variability in Atlantic paleohurricane records.

  11. Regional and inter-annual variability in Atlantic zooplankton en route to the Arctic Ocean: potential effects of multi-path Atlantic water advection through Fram Strait and the Barents Sea

    NASA Astrophysics Data System (ADS)

    Kwasniewski, Slawomir; Gluchowska, Marta; Trudnowska, Emilia; Ormanczyk, Mateusz; Walczowski, Waldemar; Beszczynska-Moeller, Agnieszka

    2016-04-01

    The Arctic is among the regions where the climate change effects on ecosystem will be the most rapid and consequential, with Arctic amplification recognized as an integral part of the process. Great part of the changes are forced by advection of warm waters from the North Atlantic and the expected modifications of Arctic marine ecosystem will be induced not only by changing environmental conditions but also as a result of introducing Atlantic biota. Thus, the knowledge of physical and biological heterogeneity of Atlantic inflow is requisite for understanding the effects of climate change on biological diversity and ecosystem functioning in the Arctic. The complex and variable two-branched structure of the Atlantic Water flow via Fram Strait and the Barents Sea most likely has a strong influence on the ocean biology in these regions, especially in the pelagic realm. Zooplankton are key components of marine ecosystems which form essential links between primary producers and grazer/predator consumers, thus they are important for functioning of the biological carbon pump. Changes in zooplankton distribution and abundance may have cascading effects on ecosystem functioning, with regulatory effects on climate. Based on data collected in summers of 2012-2014, within the scope of the Polish-Norwegian PAVE research project, we investigate zooplankton distribution, abundance and selected structural characteristics of communities, in relation to water mass properties in the Atlantic Water complex flow to the Arctic Ocean. The main questions addressed here are: what are the differences in zooplankton patterns between the Fram Strait and Barents Sea branches, and how does the inter-annual variability of Atlantic Water advection relate to changes in zooplankton? The results of the investigation are precondition for foreseeing changes in the pelagic realm in the Arctic Ocean and are necessary for constructing and tuning plankton components of ecosystem models.

  12. Climatic Effects of Regional Nuclear War

    NASA Technical Reports Server (NTRS)

    Oman, Luke D.

    2011-01-01

    We use a modern climate model and new estimates of smoke generated by fires in contemporary cities to calculate the response of the climate system to a regional nuclear war between emerging third world nuclear powers using 100 Hiroshima-size bombs (less than 0.03% of the explosive yield of the current global nuclear arsenal) on cities in the subtropics. We find significant cooling and reductions of precipitation lasting years, which would impact the global food supply. The climate changes are large and longlasting because the fuel loadings in modern cities are quite high and the subtropical solar insolation heats the resulting smoke cloud and lofts it into the high stratosphere, where removal mechanisms are slow. While the climate changes are less dramatic than found in previous "nuclear winter" simulations of a massive nuclear exchange between the superpowers, because less smoke is emitted, the changes seem to be more persistent because of improvements in representing aerosol processes and microphysical/dynamical interactions, including radiative heating effects, in newer global climate system models. The assumptions and calculations that go into these conclusions will be described.

  13. Climatic Impact of a Change in North Atlantic Deep Water Formation

    NASA Technical Reports Server (NTRS)

    Rind, D.

    1984-01-01

    The response of the ocean to climate changes is one of the most uncertain questions regarding the impact of increasing CO2 on climate and society. North Atlantic deep water (NADW) formation apparently depends on a complex confluence of different water masses originating in different areas, all of which will presumably be affected by changes in wind, evaporation, etc., as the atmosphere warms. To analyze from first principles what the effect will be on NADW formation is a task which requires an ocean modeling capability not yet available. As a substitute, past climates can be investigated to see if there is any evidence for alterations in NADW formation. In addition, the possible impact of such changes on climate can be explored. An estimate of NADW sensitivity (at least in the past) and of the climate consequences can be studied. The North Atlantic surface water temperatures can be reconstructed to indicate a substantial cooling between 11,000 and 10,000 years B.P. Were NADW formation to have ceased, it would have resulted in cooler surface waters; whether the reconstructed temperatures were due to this or some other effect cannot be determined at this time. Nevertheless, it was decided that it would be useful to see what the effect these colder temperatures would have had on the climate.

  14. Regional climate downscaling: What's the point?

    NASA Astrophysics Data System (ADS)

    Pielke, Roger A., Sr.; Wilby, Robert L.

    2012-01-01

    Dynamical and statistical downscaling of multidecadal global climate models provides finer spatial resolution information for climate impact assessments [Wilby and Fowler, 2010]. Increasingly, some scientists are using the language of "prediction" with respect to future regional climate change and impacts [e.g., Hurrell et al., 2009; Shapiro et al., 2010], yet others note serious reservations about the capability of downscaling to provide detailed, accurate predictions [see Kerr, 2011]. Dynamic downscaling is based on regional climate models (usually just the atmospheric part) that have finer horizontal grid resolution of surface features such as terrain [Castro et al., 2005]. Statistical downscaling uses transfer functions (e.g., regression relationships) representing observed relationships between larger-scale atmospheric variables and local quantities such as daily precipitation and/or temperature [Wilby and Fowler, 2010]. These approaches have been successful in improving the skill of numerical weather prediction. Statistical downscaling can also be used as the benchmark (the control) against which dynamic downscaling skill is judged [Landsea and Knaff, 2000

  15. North American Regional Climate Change Assessment Program (NARCCAP): Producing Regional Climate Change Projections for Climate Impacts Studies

    NASA Astrophysics Data System (ADS)

    Arritt, R. W.; Mearns, L.; Anderson, C.; Bader, D.; Buonomo, E.; Caya, D.; Duffy, P.; Elguindi, N.; Giorgi, F.; Gutowski, W.; Held, I.; Nunes, A.; Jones, R.; Laprise, R.; Leung, L. R.; Middleton, D.; Moufouma-Okia, W.; Nychka, D.; Qian, Y.; Roads, J.; Sain, S.; Snyder, M.; Sloan, L.; Takle, E.

    2006-12-01

    The North American Regional Climate Change Assessment Program (NARCCAP) is constructing projections of regional climate change over the coterminous United States and Canada in order to provide climate change information at decision relevant scales. A major goal of NARCCAP is to estimate uncertainties in regional scale projections of future climate by using multiple regional climate models (RCMs) nested within multiple atmosphere-ocean general circulation models (AOGCMs). NARCCAP is using six nested regional climate models at 50 km resolution to dynamically downscale realizations of current climate (1971-2000) and future climate (2041-2070, following the A2 SRES emission scenario) from four AOGCMs. Global time slice simulations, also at 50 km resolution, will be performed using the GFDL AM2.1 and NCAR CAM3 atmospheric models forced by the AOGCM sea surface temperatures and will be compared with results of the regional models. Results from this multiple-RCM, multiple-AOGCM suite will be statistically analyzed to investigate the cascade of uncertainty as one type of model draws information from another. All output will be made available to the climate analysis and climate impacts assessment communities through an archiving and data distribution plan. The climate impacts community will have these data at unprecedented spatial and temporal (hourly to six-hourly) resolution to support decision-relevant evaluations for public policy. As part of our evaluation of uncertainties, simulations are presently being concluded that nest the participating RCMs within reanalyses of observations. These simulations can be viewed as nesting the RCMs within a GCM that is nearly perfect (constrained by available observations), allowing us to separate errors attributable to the RCMs from those attributable to the driving AOGCMs. Results to date indicate that skill is greater in winter than in summer, and greater for temperature than for precipitation. Temperature and precipitation errors

  16. A reversal of climatic trends in the North Atlantic since 2005

    NASA Astrophysics Data System (ADS)

    Robson, Jon; Ortega, Pablo; Sutton, Rowan

    2016-07-01

    In the mid-1990s the North Atlantic subpolar gyre warmed rapidly, which had important climate impacts such as increased hurricane numbers and changes to rainfall over Africa, Europe and North America. Evidence suggests that the warming was largely due to a strengthening of the ocean circulation, particularly the Atlantic Meridional Overturning Circulation. Since the mid-1990s direct and indirect measurements have suggested a decline in the strength of the ocean circulation, which is expected to lead to a reduction in northward heat transport. Here we show that since 2005 a large volume of the upper North Atlantic Ocean has cooled significantly by approximately 0.45 °C or 1.5 × 1022 J, reversing the previous warming trend. By analysing observations and a state-of-the-art climate model, we show that this cooling is consistent with a reduction in the strength of the ocean circulation and heat transport, linked to record low densities in the deep Labrador Sea. The low density in the deep Labrador Sea is primarily due to deep ocean warming since 1995, but a long-term freshening also played a role. The observed upper ocean cooling since 2005 is not consistent with the hypothesis that anthropogenic aerosols directly drive Atlantic temperatures.

  17. Abrupt climate changes and the effects of North Atlantic deepwater formation: Results from the GENESIS global climate model and comparison with data from the Younger Dryas event and the event at 8200 years bp and the present

    NASA Astrophysics Data System (ADS)

    Agustsdottir, Anna Maria

    1998-10-01

    Abrupt changes in climate towards glacial conditions have occurred several times during the last tens of thousands of years. A reduction in ocean heat transport to the high-latitude North Atlantic, associated with reduction, shutdown, or southward shift in formation of North Atlantic Deepwater, is hypothesized to have caused or amplified abrupt cooling events. The model-data comparisons reported here provide strong support for this hypothesis for the Younger Dryas interval and the cold event about 8200 years ago, and show likely changes were such an oceanic change to occur in the near future. Different levels of North Atlantic ocean heat transport were specified in age-appropriate simulations using the GENESIS GCM climate model. For the Younger Dryas, simulated reduction in GENESIS ocean heat transport (in versions 1.02A and 2.0) from modern levels produces climate-anomaly patterns, including many seasonal changes, that closely match observations, however, observed changes far from the North Atlantic are somewhat larger than modeled. Both model and data indicate stronger winds during cold times. Modeled cold-time winds produce about 10% more tropical-ocean Ekman divergence in regions and at times of prominent upwelling. The cooling associated with this, but not calculated for the mixed- layer GENESIS model ocean, probably is important in model-data differences. Because of the success of GENESIS in simulating Younger Dryas changes around the North Atlantic but underestimating those beyond this region, the large changes simulated for a modern reduction of North Atlantic ocean heat transport likely march or underestimate those that would occur if such a change occurred in the near future. Reduction in ocean heat transport for 8200 years ago form modern levels produces an anomaly pattern somewhat like observations, but reduction form heat transport higher than modern produces a much better match. Together with other evidence, this suggests that this cold climate event

  18. Building Partnerships and Research Collaborations to Address the Impacts of Arctic Change: The North Atlantic Climate Change Collaboration (NAC3)

    NASA Astrophysics Data System (ADS)

    Polk, J.; North, L. A.; Strenecky, B.

    2015-12-01

    Changes in Arctic warming influence the various atmospheric and oceanic patterns that drive Caribbean and mid-latitude climate events, including extreme events like drought, tornadoes, and flooding in Kentucky and the surrounding region. Recently, the establishment of the North Atlantic Climate Change Collaboration (NAC3) project at Western Kentucky University (WKU) in partnership with the University of Akureyri (UNAK), Iceland Arctic Cooperation Network (IACN), and Caribbean Community Climate Change Centre (CCCCC) provides a foundation from which to engage students in applied research from the local to global levels and more clearly understand the many tenets of climate change impacts in the Arctic within both a global and local community context. The NAC3 project encompasses many facets, including joint international courses, student internships, economic development, service learning, and applied research. In its first phase, the project has generated myriad outcomes and opportunities for bridging STEM disciplines with other fields to holistically and collaboratively address specific human-environmental issues falling under the broad umbrella of climate change. WKU and UNAK students desire interaction and exposure to other cultures and regions that are threatened by climate change and Iceland presents a unique opportunity to study influences such as oceanic processes, island economies, sustainable harvest of fisheries, and Arctic influences on climate change. The project aims to develop a model to bring partners together to conduct applied research on the complex subject of global environmental change, particularly in the Arctic, while simultaneously focusing on changing how we learn, develop community, and engage internationally to understand the impacts and find solutions.

  19. Climate-driven range expansion of a critically endangered top predator in northeast Atlantic waters.

    PubMed

    Wynn, Russell B; Josey, Simon A; Martin, Adrian P; Johns, David G; Yésou, Pierre

    2007-10-22

    Global climate change is driving rapid distribution shifts in marine ecosystems; these are well established for lower trophic levels, but are harder to quantify for migratory top predators. By analysing a 25-year sightings-based dataset, we found evidence for rapid northwards range expansion of the critically endangered Balearic shearwater Puffinus mauretanicus in northeast Atlantic waters. A 0.6 degrees C sea surface temperature increase in the mid-1990s is interpreted as an underlying controlling factor, while simultaneous northward shifts of plankton and prey fish species suggests a strong bottom-up control. Our results have important conservation implications and provide new evidence for climate-driven regime shift in Atlantic ecosystems.

  20. Coupled decadal variability of the North Atlantic Oscillation, regional rainfall and karst spring discharges in the Campania region (southern Italy)

    NASA Astrophysics Data System (ADS)

    De Vita, P.; Allocca, V.; Manna, F.; Fabbrocino, S.

    2012-05-01

    Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation. In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period. Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index. Although the effects of the North Atlantic Oscillation (NAO) had already been demonstrated in the long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results

  1. A role for land surface forcing of North Atlantic climate and isotope signals during the 8.2kyr event?

    NASA Astrophysics Data System (ADS)

    Hopcroft, Peter; Valdes, Paul

    2014-05-01

    An important example of abrupt climate change occurred 8200 years ago in the North Atlantic and is generally known as the 8.2kyr event. This abrupt ~160 year cooling appears to coincide with the final drainage of the ice-dammed Lakes Agassiz and Ojibway. The resultant influx of meltwater to the North Atlantic is assumed to have perturbed the Atlantic Meridional Overturning circulation, reducing northward heat transport and causing widespread cooling. Numerous lines of evidence support this theory, with reconstructions showing changes in deep water formation, reductions in salinity and evidence of sea-level rise. Coupled general circulation model (GCM) simulations driven with realistic estimates of the meltwater flux show a regional cooling but fail to replicate the duration or the magnitude of this event in comparison with proxy archives. Meltwater injection was not the only rapid climate forcing in operation at this time. Drainage of the pro-glacial lakes would have had a profound effect on the boundary layer heat fluxes over North America, with potential teleconnections further afield. In this work we use an isotope-enabled version of the coupled GCM HadCM3 with boundary conditions appropriate for the time period of 9kyr (including ice sheets, greenhouse gases and orbital parameters). This model tracks oxygen isotopes throughout the hydrological cycle allowing more robust comparison with proxy archives. We analyse the impact of the removal of a lake area corresponding to Lakes Agassiz and Ojibway at this time and present sensitivity tests designed to analyse the contributions from lake removal, orographic change and the assumed isotopic content of the pro-glacial lakes. The results show a distinct pattern of cooling across North America (in the annual mean) with an apparent teleconnection to the Barents Sea, where there is warming associated with sea-ice reduction. The isotopic implications depend on the initial isotopic content of the pro-glacial lake. Assuming

  2. A STRATEGY FOR INTEGRATED ECOLOGICAL RESTORATION OF RIPARIAN BUFFERS IN THE MID-ATLANTIC REGION

    EPA Science Inventory

    Increased sediments, nutrients, and other contaminants in the Mid-Atlantic region contribute to environmental problems ranging from stream degradation to possibly Pfiesteria attacks in Chesapeake Bay. Restoring riparian areas - the filters between terrestrial watersheds and aquat...

  3. Climate-scale sea surface height variability over the Northwest Atlantic slope

    NASA Astrophysics Data System (ADS)

    Han, Guoqi; Chen, Nancy; Yen Kuo, Chun; Shum, Ck; Ma, Zhimin

    2016-04-01

    The Northwest Atlantic continental slope features strong interactions among the western boundary currents of the subpolar and subtropical gyres, and thus the sea level variability over the slope may have important implications for the large-scale ocean circulation. In this study, temporal and spatial sea level variability in the Northwest Atlantic continental slope has been investigated based on a merged satellite altimetry dataset and a monthly temperature and salinity dataset. The altimetric results are compared with steric height anomalies calculated from the temperature and salinity dataset. The study shows significant interannual and decadal sea level variability and secular change, with prominent regional differences and seemingly varying linkages to large-scale atmospheric and oceanic variability in the North Atlantic. The interannual sea level variability in the western Labrador Sea is negatively correlated with the North Atlantic Oscillation primarily via the wintertime deep convection; whereas that over the Laurentian Fan is positively correlated with the North Atlantic Oscillation. The thermosteric height anomalies are negatively (positively) correlated with the winter NAO index in the Labrador Sea (Laurentian Fan); while the halosteric height anomalies show opposite. The along-slope differences in the interannual and decadal variations and the secular trend of the sea surface height anomalies is compatible with an important interior pathway of the Labrador Sea Intermediate Water toward the central North Atlantic Basin reported in literature.

  4. Chapter 3. Effects of climate change and commercial fishing on Atlantic cod Gadus morhua.

    PubMed

    Mieszkowska, Nova; Genner, Martin J; Hawkins, Stephen J; Sims, David W

    2009-01-01

    During the course of the last century, populations of Atlantic cod Gadus morhua L. have undergone dramatic declines in abundance across their biogeographic range, leading to debate about the relative roles of climatic warming and overfishing in driving these changes. In this chapter, we describe the geographic distributions of this important predator of North Atlantic ecosystems and document extensive evidence for limitations of spatial movement and local adaptation from population genetic markers and electronic tagging. Taken together, this evidence demonstrates that knowledge of spatial population ecology is critical for evaluating the effects of climate change and commercial harvesting. To explore the possible effects of climate change on cod, we first describe thermal influences on individual physiology, growth, activity and maturation. We then evaluate evidence that temperature has influenced population-level processes including direct effects on recruitment through enhanced growth and activity, and indirect effects through changes to larval food resources. Although thermal regimes clearly define the biogeographic range of the species, and strongly influence many aspects of cod biology, the evidence that population declines across the North Atlantic are strongly linked to fishing activity is now overwhelming. Although there is considerable concern about low spawning stock biomasses, high levels of fishing activity continues in many areas. Even with reduced fishing effort, the potential for recovery from low abundance may be compromised by unfavourable climate and Allee effects. Current stock assessment and management approaches are reviewed, alongside newly advocated methods for monitoring stock status and recovery. However, it remains uncertain whether the rebuilding of cod to historic population sizes and demographic structures will be possible in a warmer North Atlantic.

  5. Objective calibration of regional climate models

    NASA Astrophysics Data System (ADS)

    Bellprat, O.; Kotlarski, S.; Lüthi, D.; SchäR, C.

    2012-12-01

    Climate models are subject to high parametric uncertainty induced by poorly confined model parameters of parameterized physical processes. Uncertain model parameters are typically calibrated in order to increase the agreement of the model with available observations. The common practice is to adjust uncertain model parameters manually, often referred to as expert tuning, which lacks objectivity and transparency in the use of observations. These shortcomings often haze model inter-comparisons and hinder the implementation of new model parameterizations. Methods which would allow to systematically calibrate model parameters are unfortunately often not applicable to state-of-the-art climate models, due to computational constraints facing the high dimensionality and non-linearity of the problem. Here we present an approach to objectively calibrate a regional climate model, using reanalysis driven simulations and building upon a quadratic metamodel presented by Neelin et al. (2010) that serves as a computationally cheap surrogate of the model. Five model parameters originating from different parameterizations are selected for the optimization according to their influence on the model performance. The metamodel accurately estimates spatial averages of 2 m temperature, precipitation and total cloud cover, with an uncertainty of similar magnitude as the internal variability of the regional climate model. The non-linearities of the parameter perturbations are well captured, such that only a limited number of 20-50 simulations are needed to estimate optimal parameter settings. Parameter interactions are small, which allows to further reduce the number of simulations. In comparison to an ensemble of the same model which has undergone expert tuning, the calibration yields similar optimal model configurations, but leading to an additional reduction of the model error. The performance range captured is much wider than sampled with the expert-tuned ensemble and the presented

  6. Portuguese wine regions under a changing climate

    NASA Astrophysics Data System (ADS)

    Santos, João A.; Fraga, Helder; Malheiro, Aureliano C.; Moutinho-Pereira, José; Jones, Gregory V.; Pinto, Joaquim G.

    2014-05-01

    Viticulture and wine production are among the most important sectors of the Portuguese economy. However, as grapevines are strongly affected by weather and climate, climate change may represent an important threat to wine production. The current (1950-2000) and future (2041-2070) bioclimatic conditions in Portugal are discussed by analyzing a number of indices suitable for viticultural zoning, including a categorized bioclimatic index. A two-step method of spatial pattern downscaling is applied in order to achieve a very high spatial resolution (of approximately 1 km) throughout Portugal. Future projections are based on an ensemble of 13 climate model transient experiments, forced by the SRES A1B emission scenario. Results for the recent past are in clear agreement with the current distribution of vineyards and of the established Denomination of Origin regions. Furthermore, the typical climatic conditions associated with each grapevine variety that are currently grown in Portugal are assessed. Under future scenarios, nevertheless, the current conditions are projected to change significantly towards a lower bioclimatic diversity. This can be explained by the projected warming and drying in future decades. The resulting changes in varietal suitability and wine characteristics of each region may thereby bring important challenges for the Portuguese winemaking sector. As such, new measures need to be timely implemented to adapt to these climate change projections and to mitigate their likely detrimental impacts on the Portuguese economy. Acknowledgments: this work is supported by European Union Funds (FEDER/COMPETE - Operational Competitiveness Programme) and by national funds (FCT - Portuguese Foundation for Science and Technology) under the project ClimVineSafe (PTDC/AGR-ALI/110877/2009).

  7. Structure and impact of atmospheric blocking over the Euro-Atlantic region in present-day and future simulations

    NASA Astrophysics Data System (ADS)

    Masato, G.; Woollings, T.; Hoskins, B. J.

    2014-02-01

    The spatial structure of winter atmospheric blocking and its impact on the surface temperatures are analyzed for the current climate and a strong CO2 emission scenario over the Euro-Atlantic sector, using four different global circulation models. The models perform very well in describing the spatial pattern of meteorological fields associated with blocking, despite the well-known negative bias associated with the European blocking frequency. While a slight increase in the frequency of the Atlantic blocking is observed for the future climate, the European blocking frequency remains unchanged, with a net eastward shift apparent for the European warm blocking events. Under enhanced CO2 forcing, Atlantic blocking is associated with reduced amplitudes for positive and negative anomalies both in the geopotential height at 500 hPa and in the surface temperature, in particular for the latter. The anomalies associated with the occurrence of the two types of European blocking (those dominated by warm and cold air masses) exhibit changed shapes and locations in both the geopotential height and surface temperature fields, with only the cold cases leading to severe cold weather conditions over Europe and most of the polar region. Moreover, the eastward shift and amplification of the anticyclone associated with the warm events in the future is found to generate strong positive surface temperature anomalies over the entire polar cap. As a whole, the results show a marked increase in the sensitivity of Arctic temperatures to blocking in the future.

  8. Tropical Atlantic Impacts on the Decadal Climate Variability of the Tropical Ocean and Atmosphere.

    NASA Astrophysics Data System (ADS)

    Li, X.; Xie, S. P.; Gille, S. T.; Yoo, C.

    2015-12-01

    Previous studies revealed atmospheric bridges between the tropical Pacific, Atlantic, and Indian Ocean. In particular, several recent works indicate that the Atlantic sea surface temperature (SST) may contribute to the climate variability over the equatorial Pacific. Inspired by these studies, our work aims at investigating the impact of the tropical Atlantic on the entire tropical climate system, and uncovering the physical dynamics under these tropical teleconnections. We first performed a 'pacemaker' simulation by restoring the satellite era tropical Atlantic SST changes in a fully coupled model - the CESM1. Results reveal that the Atlantic warming heats the Indo-Western Pacific and cools the Eastern Pacific, enhances the Walker circulation and drives the subsurface Pacific to a La Niña mode, contributing to 60-70% of the above tropical changes in the past 30 years. The same pan-tropical teleconnections have been validated by the statistics of observations and 106 CMIP5 control simulations. We then used a hierarchy of atmospheric and oceanic models with different complexities, to single out the roles of atmospheric dynamics, atmosphere-ocean fluxes, and oceanic dynamics in these teleconnections. With these simulations we established a two-step mechanism as shown in the schematic figure: 1) Atlantic warming generates an atmospheric deep convection and induces easterly wind anomalies over the Indo-Western Pacific in the form of Kelvin waves, and westerly wind anomalies over the eastern equatorial Pacific as Rossby waves, in line with Gill's solution. This circulation changes warms the Indo-Western Pacific and cools the Eastern Pacific with the wind-evaporation-SST effect, forming a temperature gradient over the Indo-Pacific basins. 2) The temperature gradient further generates a secondary atmospheric deep convection, which reinforces the easterly wind anomalies over the equatorial Pacific and enhances the Walker circulation, triggering the Pacific to a La Ni

  9. Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate

    PubMed Central

    Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang

    2017-01-01

    Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term climate projection. PMID:28070560

  10. Using WRF for Regional Climate Modeling: An Emphasis on the Southeast U.S. for Future Air Quality

    EPA Science Inventory

    This presentation describes preliminary analysis of a five-member regional climate ensemble (developed by AMAD and its contractors, including UNC) to determine if there is any consensus on projected changes to the placement of the North Atlantic Subtropical High (NASH, or Bermuda...

  11. Eliciting climate experts' knowledge to address model uncertainties in regional climate projections: a case study of Guanacaste, Northwest Costa Rica

    NASA Astrophysics Data System (ADS)

    Grossmann, I.; Steyn, D. G.

    2014-12-01

    Global general circulation models typically cannot provide the detailed and accurate regional climate information required by stakeholders for climate adaptation efforts, given their limited capacity to resolve the regional topography and changes in local sea surface temperature, wind and circulation patterns. The study region in Northwest Costa Rica has a tropical wet-dry climate with a double-peak wet season. During the dry season the central Costa Rican mountains prevent tropical Atlantic moisture from reaching the region. Most of the annual precipitation is received following the northward migration of the ITCZ in May that allows the region to benefit from moist southwesterly flow from the tropical Pacific. The wet season begins with a short period of "early rains" and is interrupted by the mid-summer drought associated with the intensification and westward expansion of the North Atlantic subtropical high in late June. Model projections for the 21st century indicate a lengthening and intensification of the mid-summer drought and a weakening of the early rains on which current crop cultivation practices rely. We developed an expert elicitation to systematically address uncertainties in the available model projections of changes in the seasonal precipitation pattern. Our approach extends an elicitation approach developed previously at Carnegie Mellon University. Experts in the climate of the study region or Central American climate were asked to assess the mechanisms driving precipitation during each part of the season, uncertainties regarding these mechanisms, expected changes in each mechanism in a warming climate, and the capacity of current models to reproduce these processes. To avoid overconfidence bias, a step-by-step procedure was followed to estimate changes in the timing and intensity of precipitation during each part of the season. The questions drew upon interviews conducted with the regions stakeholders to assess their climate information needs. This

  12. Interannual Rainfall Variability in the Tropical Atlantic Region

    NASA Technical Reports Server (NTRS)

    Gu, Guojun

    2005-01-01

    Rainfall variability on seasonal and interannual-to-interdecadal time scales in the tropical Atlantic is quantified using a 25-year (1979-2003) monthly rainfall dataset from the Global Precipitation Climatology Project (GPCP). The ITCZ measured by monthly rainfall between 15-37.5 deg W attains its peak as moving to the northernmost latitude (4-10 deg N) during July-September in which the most total rainfall is observed in the tropical Atlantic basin (17.5 deg S-22.5 deg N, 15 deg-37.5 deg W); the ITCZ becomes weakest during January-February with the least total rainfall as it moves to the south. In contrast, rainfall variability on interannual to interdecadal time scales shows a quite different seasonal preference. The most intense interannual variability occurs during March-May when the ITCZ tends to be near the equator and becomes weaker. Significant, negative correlations between the ITCZ strength and latitude anomalies are observed during boreal spring and early summer. The ITCZ strength and total rainfall amount in the tropical Atlantic basin are significantly modulated by the Pacific El Nino and the Atlantic equatorial mode (or Atlantic Nino) particularly during boreal spring and summer; whereas the impact of the Atlantic interhemispheric mode is considerably weaker. Regarding the anomalous latitudes of the ITCZ, the influence can come from both local, i.e., the Atlantic interhemispheric and equatorial modes, and remote forcings, i. e., El Nino; however, a direct impact of El Nino on the latitudes of the ITCZ can only be found during April-July, not in winter and early spring in which the warmest SST anomalies are usually observed in the equatorial Pacific.

  13. The Plio-Pleistocene development of Atlantic deep-water circulation and its influence on climate trends

    NASA Astrophysics Data System (ADS)

    Bell, David B.; Jung, Simon J. A.; Kroon, Dick

    2015-09-01

    Using benthic stable isotope records from 10 sites in the Atlantic Ocean, including two new records from Walvis Ridge in the Southeast Atlantic (Sites 1264 and 1267), we review changes in Atlantic deep-water circulation in the context of Plio-Pleistocene climate. Overall, we find non-linear responses of Atlantic deep-water circulation to a cooling climate, with differently evolving glacial and interglacial states. Our main conclusion is that peak North Atlantic Deep Water (NADW) production was reached between ˜2.0 and 1.5 Ma, most prominently seen by a maximum in ventilated (high δ13C) conditions in the mid-depth Southeast Atlantic (Site 1264). We infer that a major source of NADW at this time was the export of dense overflow water from the Nordic Seas into the abyssal East Atlantic. Sea surface temperature records from the North and South Atlantic support this notion and indicate that the peak NADW production between ˜2.0 and 1.5 Ma was compensated by a stronger warm surface-water return flow (i.e. Atlantic Meridional Overturning Circulation (AMOC) was enhanced), causing long-term (>105 year) heat piracy from the South to the North Atlantic. In the wider picture of Plio-Pleistocene climate evolution, we find that a long-term enhancement in the average state of AMOC (˜2.4-1.3 Ma) coincides with the "41-kyr world". Hence, we speculate that the transitory negative feedback response of enhanced AMOC to a cooling climate supplied heat to key areas of ice-sheet growth, acting to limit their size and maintain the "41-kyr world". Once a threshold in global cooling was reached, the strength of AMOC lessened, providing a positive feedback for the Early-Middle Pleistocene Transition and the associated build-up of northern hemisphere ice-sheets.

  14. A framework for regional modeling of past climates

    NASA Astrophysics Data System (ADS)

    Sloan, L. C.

    2006-09-01

    The methods of reconstructing ancient climate information from the rock record are summarized, and the climate forcing factors that have been active at global and regional scales through Earth history are reviewed. In this context, the challenges and approaches to modeling past climates by using a regional climate model are discussed. A significant challenge to such modeling efforts arises if the time period of interest occurred prior to the past ˜3 5 million years, at which point land sea distributions and topography markedly different from present must be specified at the spatial resolution required by regional climate models. Creating these boundary conditions requires a high degree of geologic knowledge, and also depends greatly upon the global climate model driving conditions. Despite this and other challenges, regional climate models represent an important and unique tool for paleoclimate investigations. Application of regional climate models to paleoclimate studies may provide another way to assess the overall performance of regional climate models.

  15. Influence of the North Atlantic dipole on climate changes over Eurasia

    NASA Astrophysics Data System (ADS)

    Serykh, I. V.

    2016-11-01

    In this paper, some hydrophysical and meteorological characteristics of negative (1948-1976 and 1999-2015) and positive (1977-1998) phases of the Pacific Decadal Oscillation (PDO) and Interdecadal Pacific Oscillation (IPO) in the North Atlantic and Eurasia are constructed and investigated. Specifically, the near-surface temperature, sea-level atmospheric pressure, wind speed, heat content of the upper 700 m ocean layer, water temperature and salinity at various depths, the latent and sensible heat fluxes from the ocean to the atmosphere are analyzed. The fields obtained are in good agreement and complement each other. This gives important information about the hydrometeorological conditions in the region under study. Analysis of these data has shown that in the upper 1000 m North Atlantic layer there is a thermal dipole which can be interpreted as an oceanic analog of the atmospheric North Atlantic Oscillation (NAO). An index of the North Atlantic Dipole (NAD) as the difference between the mean heat contents in the upper 700 m oceanic layer between the regions (50°-70° N; 60°-10° W) and (20°-40° N; 80°-30° W) is proposed. A possible physical mechanism of the internal oscillations with a quasi-60-year period in the North Atlantics- Eurasia system of ocean-atmosphere interactions is discussed.

  16. Observations of Saharan dust in the Caribbean and Implications for Regional Climate Variability

    NASA Technical Reports Server (NTRS)

    Remer, L.; Einaudi, Franco

    2001-01-01

    Massive quantities of dust aerosol, originating at source locations in the Saharan desert are frequently transported westward across the Atlantic. Saharan dust has been frequently identified at ground-based stations in South America, on Barbados, in Florida and in Texas. Recently, in July of 2000, the Puerto Rican Dust Experiment (PRiDE), consisting of researchers from the U.S. Navy, NASA, the University of Miami and the University of Puerto Rico joined together to study this important phenomenon. Numerical forecast models tracked each dust event as the dust left the African continent and transversed the Atlantic. Ground-based, ship-based, airborne and satellite sensors were used to characterize the physical and radiative properties of the dust aerosol. The dust plays an important role in terms of radiative forcing of regional climate. Satellite sensors such as NASA's EOS-MODIS aboard the Terra satellite will provide important continuing information on the dust aerosol and its climatic effects.

  17. Climate impacts on northern Canada: regional background.

    PubMed

    Prowse, Terry D; Furgal, Chris; Bonsal, Barrie R; Peters, Daniel L

    2009-07-01

    Understanding the implications of climate change on northern Canada requires a background about the size and diversity of its human and biogeophysical systems. Occupying an area of almost 40% of Canada, with one-third of this contained in Arctic islands, Canada's northern territories consist of a diversity of physical environments unrivaled around the circumpolar north. Major ecozones composed of a range of landforms, climate, vegetation, and wildlife include: Arctic, boreal and taiga cordillera; boreal and taiga plains; taiga shield; and northern and southern Arctic. Although generally characterized by a cold climate, there is an enormous range in air temperature with mean annual values being as high as -5 degrees C in the south to as low as -20 degrees C in the high Arctic islands. A similar contrast characterizes precipitation, which can be > 700 mm y(-1) in some southern alpine regions to as low as 50 mm y(-1) over islands of the high Arctic. Major freshwater resources are found within most northern ecozones, varying from large glaciers or ice caps and lakes to extensive wetlands and peat lands. Most of the North's renewable water, however, is found within its major river networks and originates in more southerly headwaters. Ice covers characterize the freshwater systems for multiple months of the year while permafrost prevails in various forms, dominating the terrestrial landscape. The marine environment, which envelops the Canadian Arctic Archipelago, is dominated by seasonal to multiyear sea ice often several meters thick that plays a key role in the regional climate. Almost two-thirds of northern Canadian communities are located along coastlines with the entire population being just over 100 000. Most recent population growth has been dominated by an expansion of nonaboriginals, primarily the result of resource development and the growth of public administration. The economies of northern communities, however, remain quite mixed with traditional land

  18. Climate Change and Climate Variability in the Latin American Region

    NASA Astrophysics Data System (ADS)

    Magrin, G. O.; Gay Garcia, C.; Cruz Choque, D.; Gimenez-Sal, J. C.; Moreno, A. R.; Nagy, G. J.; Nobre, C.; Villamizar, A.

    2007-05-01

    Over the past three decades LA was subjected to several climate-related impacts due to increased El Niño occurrences. Two extremely intense episodes of El Niño and other increased climate extremes happened during this period contributing greatly to augment the vulnerability of human systems to natural disasters. In addition to weather and climate, the main drivers of the increased vulnerability are demographic pressure, unregulated urban growth, poverty and rural migration, low investment in infrastructure and services, and problems in inter-sector coordination. As well, increases in temperature and increases/decreases in precipitation observed during the last part of 20th century have yet led to intensification of glaciers melting, increases in floods/droughts and forest fires frequency, increases in morbidity and mortality, increases in plant diseases incidence; lost of biodiversity, reduction in dairy cattle production, and problems with hydropower generation, highly affecting LA human system. For the end of the 21st century, the projected mean warming for LA ranges from 1 to 7.5ºC and the frequency of weather and climate extremes could increase. Additionally, deforestation is projected to continue leading to a reduction of 25 percent in Amazonia forest in 2020 and 40 percent in 2050. Soybeans planted area in South America could increase by 55 percent by 2020 enhancing aridity/desertification in many of the already water- stressed regions. By 2050 LA population is likely to be 50 percent larger than in 2000, and migration from the country sides to the cities will continue. In the near future, these predicted changes are very likely to severely affect a number of ecosystems and sectors distribution; b) Disappearing most tropical glaciers; c) Reducing water availability and hydropower generation; d) Increasing desertification and aridity; e) Severely affecting people, resources and economic activities in coastal areas; f) Increasing crop's pests and diseases

  19. Ocean circulation in the southern Benguela region from the Pliocene to the Pleistocene: tracking Agulhas leakage into the SE Atlantic

    NASA Astrophysics Data System (ADS)

    Petrick, Benjamin; McClymont, Erin; Felder, Sojna; Leng, Melanie

    2013-04-01

    The transition from the warmth of the middle Pliocene to the large amplitude, 100 kyr glacial-interglacial cycles of the late Pleistocene provides a way to understand the forcings and impacts of regional and global climate change. Here, we investigate changes in ocean circulation over the period from 3.5 Ma to present using a marine sediment core, ODP Site 1087 (31o28'S, 15o19'E, 1374m water depth). ODP 1087 is located in the South-east Atlantic Ocean, outside the Benguela upwelling region. Its location allows investigation of the history of the heat and salt transfer to the Atlantic Ocean from the Indian Ocean ("Agulhas leakage"), which plays an important part in the global thermohaline circulation. It is not known how this transfer reacted to generally warmer global temperatures during the mid-Pliocene, nor to the transition to a globally cooler climate in the early Pleistocene. Our approach is to apply several organic geochemistry proxies and foraminiferal analyses to reconstruct the history of ODP 1087. These include the U37K' index to reconstruct sea surface temperatures, pigment analysis for understanding productivity changes, and foraminifera assemblage analysis to detect the presence of different water masses at the site. We have identified changes in SSTs and biological productivity that we argue to reflect shifts in the position of the Benguela upwelling cells, and a changing influence of Agulhas leakage. Our new data reveal a different organization in the Southeast Atlantic. It shows that during the Pliocene ODP 1087 was dominated by Benguela upwelling which had shifted south. We find no evidence for Agulhas leakage during the mid Pliocene, which could mean that Agulhas Leakage was severely reduced during the mid Pliocene. The implications of these results for understanding Plio-Pleistocene climate changes will be explored here.

  20. Aerosol-cloud interactions in the South-East Atlantic: knowledge gaps, planned observations to address them, and implications for global climate change modeling

    NASA Astrophysics Data System (ADS)

    Redemann, Jens; Wood, Robert; Zuidema, Paquita; Haywood, James; Luna, Bernadette; Abel, Steven

    2015-04-01

    Southern Africa produces almost a third of the Earth's biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. Particles lofted into the mid-troposphere are transported westward over the South-East (SE) Atlantic, home to one of the three permanent subtropical Stratocumulus (Sc) cloud decks in the world. The stratocumulus "climate radiators" are critical to the regional and global climate system. They interact with dense layers of BB aerosols that initially overlay the cloud deck, but later subside and are mixed into the clouds. These interactions include adjustments to aerosol-induced solar heating and microphysical effects. As emphasized in the latest IPCC report, the global representation of these aerosol-cloud interaction processes in climate models is one of the largest uncertainty in estimates of future climate. Hence, new observations over the SE Atlantic have significant implications for global climate change scenarios. We discuss the current knowledge of aerosol and cloud property distributions based on satellite observations and sparse suborbital sampling, and describe planned field campaigns in the region. Specifically, we describe the scientific objectives and implementation of the following four synergistic, international research activities aimed at providing a process-level understanding of aerosol-cloud interactions over the SE Atlantic: 1) ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS), a five-year investigation between 2015 and 2019 with three Intensive Observation Periods (IOP), recently funded by the NASA Earth-Venture Suborbital Program, 2) CLARIFY-2016 (CLoud-Aerosol-Radiation Interactions and Forcing: Year 2016), a comprehensive observational and modeling programme funded by the UK's Natural Environment Research Council (NERC), and supported by the UK Met Office. 3) LASIC (Layered Atlantic Smoke Interactions with Clouds), a funded

  1. Aerosol-Cloud Interactions in the South-East Atlantic: Knowledge Gaps, Planned Observations to Address Them, and Implications for Global Climate Change Modeling

    NASA Technical Reports Server (NTRS)

    Redemann, Jens; Wood, R.; Zuidema, P.; Haywood, J.; Luna, B.; Abel, S.

    2015-01-01

    Southern Africa produces almost a third of the Earth's biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. Particles lofted into the mid-troposphere are transported westward over the South-East (SE) Atlantic, home to one of the three permanent subtropical Stratocumulus (Sc) cloud decks in the world. The stratocumulus "climate radiators" are critical to the regional and global climate system. They interact with dense layers of BB aerosols that initially overlay the cloud deck, but later subside and are mixed into the clouds. These interactions include adjustments to aerosol-induced solar heating and microphysical effects. As emphasized in the latest IPCC report, the global representation of these aerosol-cloud interaction processes in climate models is one of the largest uncertainty in estimates of future climate. Hence, new observations over the SE Atlantic have significant implications for global climate change scenarios. We discuss the current knowledge of aerosol and cloud property distributions based on satellite observations and sparse suborbital sampling, and describe planned field campaigns in the region. Specifically, we describe the scientific objectives and implementation of the following four synergistic, international research activities aimed at providing a process-level understanding of aerosol-cloud interactions over the SE Atlantic: 1) ORACLES (Observations of Aerosols above Clouds and their interactions), a five-year investigation between 2015 and 2019 with three Intensive Observation Periods (IOP), recently funded by the NASA Earth-Venture Suborbital Program, 2) CLARIFY-2016 (Cloud-Aerosol-Radiation Interactions and Forcing: Year 2016), a comprehensive observational and modeling programme funded by the UK's Natural Environment Research Council (NERC), and supported by the UK Met Office. 3) LASIC (Layered Atlantic Smoke Interactions with Clouds), a funded

  2. Decadal-Scale Tropical North Atlantic Climate Variability Recorded in Slow Growing Cape Verde Corals

    NASA Astrophysics Data System (ADS)

    Moses, C. S.; Swart, P. K.; Dodge, R. E.; Helmle, K. P.; Thorrold, S.

    2002-12-01

    The decadal to century scale climate variability of the tropical North Atlantic has major implications for both neighboring coastal and inland areas. Changes in patterns of sea surface temperature (SST) and SST anomalies (SSTA) in the tropical North Atlantic are known to affect rainfall in Florida, South America, and sub-Saharan Africa, as well as the number of major hurricanes formed in the Atlantic. Because of the significance of these connections, it is important to further increase our predictive capacity for the recognition of trends and cycles in tropical North Atlantic SST and SSTA. Located at 15° N latitude off the west coast of sub-Saharan Africa, the Cape Verde Islands are an ideal geographic location to search for records of the Tropical North Atlantic Index (TNA). Such patterns are present in proxy indicators of climate (O, C, Sr/Ca and Mg/Ca) recorded in the skeletons of slow growing corals, such as Siderastrea radians, found in Cape Verde (growth rate = 1-2 mm/yr). These corals represent an archive for SST and SSTA records that exceed the instrumental period of the eastern tropical North Atlantic. We cored corals from several different locations within the Cape Verde archipelago and analyzed them for stable isotopes (δ13C and δ18O) and minor elements (Sr, Mg, and Ba). The δ18O signal present in these corals shows a distinct relationship to the TNA over the better part of the last 100 years. In addition, the δ18O record in several of these corals also records the onset of the latest Sahel (11°-18° N in Africa) drought which began in 1970. The Sr/Ca and Mg/Ca records of these corals indicate a slight warming of the waters around Cape Verde during the last 100 years, as well as accurately recording the El Niño events of 1982-83 and 1997-98. The correlations present between the records in these corals and the known instrumental record for the eastern tropical North Atlantic suggests that the fluctuations recorded in the proxy indicators may be

  3. Drivers of diel and regional variations of halocarbon emissions from the tropical North East Atlantic

    NASA Astrophysics Data System (ADS)

    Hepach, H.; Quack, B.; Ziska, F.; Fuhlbrügge, S.; Atlas, E. L.; Peeken, I.; Krüger, K.; Wallace, D. W. R.

    2013-07-01

    Methyl iodide (CH3I}, bromoform (CHBr3) and dibromomethane (CH2Br2), which are produced naturally in the oceans, take part in ozone chemistry both in the troposphere and the stratosphere. The significance of oceanic upwelling regions for emissions of these trace gases in the global context is still uncertain although they have been identified as important source regions. To better quantify the role of upwelling areas in current and future climate, this paper analyzes major factors that influenced halocarbon emissions from the tropical North East Atlantic including the Mauritanian upwelling during the DRIVE expedition. Diel and regional variability of oceanic and atmospheric CH3I, CHBr3 and CH2Br2 was determined along with biological and meteorological parameters at six 24 h-stations. Low oceanic concentrations of CH3I from 0.1-5.4 pmol L-1 were equally distributed throughout the investigation area. CHBr3 of 1.0-42.4 pmol L-1 and CH2Br2 of 1.0-9.4 pmol L-1 were measured with maximum concentrations close to the Mauritanian coast. Atmospheric mixing rations of CH3I of up to 3.3, CHBr3 to 8.9 and CH2Br2 to 3.1 ppt above the upwelling and 1.8, 12.8, respectively 2.2 ppt at a Cape Verdean coast were detected during the campaign. While diel variability in CH3I emissions could be mainly ascribed to oceanic non-biological production, no main driver was identified for its emissions in the entire study region. In contrast, oceanic bromocarbons resulted from biogenic sources which were identified as regional drivers of their sea-to-air fluxes. The diel impact of wind speed on bromocarbon emissions increased with decreasing distance to the coast. The height of the marine atmospheric boundary layer (MABL) was determined as an additional factor influencing halocarbon emissions. Oceanic and atmospheric halocarbons correlated well in the study region and in combination with high oceanic CH3I, CHBr3 and CH2Br2 concentrations, local hot spots of atmospheric halocarbons could solely

  4. 600 yr High-Resolution Climate Reconstruction of the Atlantic Multidecadal Variability deduced from a Puerto Rican Speleothem

    NASA Astrophysics Data System (ADS)

    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

  5. The relationship of boundary layer clouds in the tropical southeast Atlantic to absorbing aerosols, meteorology and climate change

    NASA Astrophysics Data System (ADS)

    Zuidema, P.; Adebiyi, A. A.; Ramajiguru, L.

    2015-12-01

    Ascension Island, a remote island located in the middle of the Atlantic Ocean within the trade-wind region oat 8S, 14.5W, experiences the outflow of biomass-burning aerosols from continental Africa, over 2000 km away, from July through November, peaking in August and September. The shortwave-absorbing free-tropospheric aerosols, located in a region of high solar irradiance, provide a climate warming that is poorly represented in global aerosol climate models. The low clouds can respond to the smoke layer in myriad possible ways that are not yet well-documented. The shortwave-warming can stabilize the free-troposphere, enhancing the low cloud fraction. The deepening boundary layer and subsiding smoke layer also increase the likelihood of aerosol-cloud microphysical interactions. Interest in this climate regime is supporting an observational strategy of a year-long DOE ARM Mobile Facility deployment to Ascension (Layered Atlantic Smoke Interactions with Clouds, or LASIC), and an NSF aircraft campaign (ObservatioNs of Fire's Impact on the southeast atlantic REgion, or ONFIRE) based on Sao Tome Island. These campaigns will be integrated with NASA, UK and African activities sharing similar goals based further south in Namibia. Initial analysis is distinguishing meteorology from aerosol impacts on the boundary layer cloud fields. The forward trajectories of emissions from over 24,000 fire sources on continental Africa show that a free-tropospheric jet can advect aerosols to above Ascension island in just one-two days. The fast transport time encourages retention of signatures of the fire sources, in particular the radiatively-crucial single-scattering albedo value. Thereafter, a deep land-based anticyclonic high recirculates over one-third of these trajectories back to the African continent, explaining the widespread extent of the aerosol layer. The free-tropospheric jet also reduces the mean atmospheric subsidence independently of shortwave absorption by the aerosols

  6. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities.

    PubMed

    Barton, Andrew D; Irwin, Andrew J; Finkel, Zoe V; Stock, Charles A

    2016-03-15

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951-2000) and future (2051-2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec(-1)), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec(-1) The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles.

  7. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities

    PubMed Central

    Barton, Andrew D.; Finkel, Zoe V.; Stock, Charles A.

    2016-01-01

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951–2000) and future (2051–2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec−1), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec−1. The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles. PMID:26903635

  8. Program for Arctic Regional Climate Assessment (PARCA)

    NASA Technical Reports Server (NTRS)

    Gogineni, Sivaprasad; Thomas, Robert H.; Abdalati, Waleed (Editor)

    1999-01-01

    The Program for Arctic Regional Climate Assessment (PARCA) is a NASA-sponsored initiative with the prime objective of understanding the mass balance of the Greenland ice sheet. In October 1998, PARCA investigators met to review activities of the previous year, assess the program's progress, and plan future investigations directed at accomplishing that objective. Some exciting results were presented and discussed, including evidence of dramatic thinning of the ice sheet near the southeastern coast. Details of the investigations and many of the accomplishments are given in this report, but major highlights are given in the Executive Summary of the report.

  9. The Barrier Layer of the Atlantic Warmpool: Formation Mechanism and Influence on the Mean Climate

    SciTech Connect

    Balaguru, Karthik; Chang, P.; Saravanan, R.; Jang, C. J.

    2012-04-20

    Many Coupled General Circulation Models (CGCMs) tend to overestimate the salinity in the Atlantic warm pool or the Northwestern Tropical Atlantic (NWTA) and underestimate the surface salinity in the subtropical salinity maxima region. Most of these models also suffer from a sea-surface temperature (SST) bias in the NWTA region, leading to suggestions that the upper ocean salinity stratification may need to be improved in order to improve the Barrier Layer (BL) simulations and thus the SST through BL-SST-Intertropical Convergence Zone (ITCZ) feedbacks. In the present study, we use a CGCM to perform a set of idealized numerical experiments to test and understand the sensitivity of the BL and consequently SST in the NWTA region to freshwater flux and hence the upper ocean salinity stratification. We find that the BL of the NWTA is sensitive to upper ocean salinity changes in the Amazon river discharge region and the subtropical salinity maxima region. The BL phenomenon is further manifested by the formation of winter temperature inversions in our model simulations, the maximum magnitude of inversions being about 0.20 C. The atmo- spheric response causes a statistically significant reduction of mean precipitation and SST in the equatorial Atlantic region and helps improve the respective biases by 10-15 %. In the region of improved BL simulation, the SST change is positive and in the right direction of bias correction, albeit weak.

  10. Climatic and limnological changes associated with the Younger Dryas in Atlantic Canada

    SciTech Connect

    Wilson, S.E.; Smol, J.P.; Walker, I.R.

    1993-03-01

    Pollen, diatom and chironomid fossils from the sediments of a core from Brier Island Bog Lake, Nova Scotia were studied in an attempt to relate changes in microfossil composition to a climatic cooling in Atlantic Canada correlative with the European Younger Dryas ca. 10 to 11 ka. Our paleolimnological data were then compared to similar types of data from Splan Pond, New Brunswick to determine if there were any significant differences between a coastal and a more inland site. Nonarboreal pollen was dominant throughout the Brier Island core and the interval 10.0-11.0 ka did not show the typical decline in Picea and increases in tundra-like vegetation characteristic of many sites in Atlantic Canada. However, the limnological indicators did undergo marked changes in taxon composition. The chironomid assemblage was initially dominated by shallow-water, warm-adapted chironomid taxa followed by abundant Sergentia (a cold stenotherm) during 10-11 ka. Sergentia disappeared in the {open_quotes}post Younger Dryas{close_quotes} interval and the warm-adapted genera resumed dominance. Chironomid-inferred paleotemperature reconstructions revealed that at both Brier Island Bog Lake and Splan Pond, summer surface-water temperatures dropped abruptly to between 13 and 17{degrees}C during the 10-11 ka interval, suggesting that a cooler climate was present in Atlantic Canada correlative with the European Younger Dryas. Diatom assemblage changes during the same period corroborate the occurrence of limnological fluctuations. 40 refs., 8 figs., 1 tab.

  11. Biogeochemical and ecosystem responses of the North Atlantic subtropical gyre to atmospheric forcing and climate variability

    NASA Astrophysics Data System (ADS)

    Bates, N. R.; Lomas, M. L.; Johnson, R. J.; Knap, A. H.

    2003-04-01

    Long-term oceanographic time-series near Bermuda and Hawaii have generated new insights about the responses of and interactions between ocean biogeochemistry, ecosystem dynamics, and physical variability of the atmosphere and climate. Over the last 14 years, physical, chemical and biological measurements have been collected each month at the Bermuda Atlantic Time-series Study (BATS) site in the oligotrophic subtropical gyre of the North Atlantic. On seasonal time-scales, complex interactions between physical forcing, nutrient and carbon cycling, and biological community dynamics have been demonstrated. On interannual time-scales, significant coupling has been observed between physical forcing, which is linked to modes of climate variability such as the North Atlantic Oscillation (NAO), and variability of biogeochemical and ecosystem community structure. Much of the variance of temperature, mixed layer depth, nutrient inputs, primary production, and phytoplankton community dynamics appear related to NAO variability. Over the past decade, a shift in the fate of the carbon fixed during primary production has occurred. This change in the partitioning of primary production correlates with changes in phytoplankton community structure and variability in NAO phase. The magnitude and temporal variability of the oceanic sink for atmospheric CO2 in the subtropical gyre also appears linked to NAO variability and it's influence on shallow mode water formation in the northern fringes of the subtropical gyre.

  12. Educator Effectiveness Series: Assessing School Climate. Q&A with Jonathan Cohen, Ph.D. REL Mid-Atlantic Webinar

    ERIC Educational Resources Information Center

    Cohen, Jonathan

    2015-01-01

    The REL Mid-Atlantic Webinar discussed the elements in a positive school climate and shared different methods for assessing school data, including the Comprehensive School Climate Inventory. The Q&A presented in this document address the questions participants had for Dr. Cohen following the webinar. The webinar recording and PowerPoint…

  13. Climate services within a regional climate adaptation project

    NASA Astrophysics Data System (ADS)

    Hänsel, Stephanie; Heidenreich, Majana; Franke, Johannes; Riedel, Kathrin; Matschullat, Jörg; Bernhofer, Christian

    2013-04-01

    In recent years the demand for adapting to climate variability and change became more and more obvious. Thus a multitude of projects dealing with climate adaptation strategies and concrete measures was launched. Commonly, developing adaptation options is based on downscaled climate model outputs. These outputs have to be provided within the projects, but just providing the data is far from being sufficient. Obstacles connected with using climate projections for climate adaptation include uncertainties and bandwidths of climate projections and the inability of models to describe parameters such as extreme weather events, which are particularly relevant for many climate adaptation decisions. Climate scientists know that model outputs are no climate data and cannot be treated as observational data were treated in the past. Still, many practitioners demand precise values for future climate to replace past CLINO-values and to run their applications. Thus, climate adaptation involves adapting the instruments and processes used in deriving climate-related decisions. Communicating the challenges arising from this need in rethinking common procedures is of outstanding significance for any successful adaptation practice. Dealing with uncertainties of climate projections is a constant necessity, since they are always based on several simplifications, parameterisations and assumptions, e.g., on the future socioeconomic development or on climate sensitivity. Future climate should thus be communicated in bandwidths. Working with just one scenario, one climate model, or even working with ensemble means is risky as it evokes a higher than appropriate perceived confidence in the results. It encourages using familiar tools in processing climate information, rather than caution. Consequences are suboptimal adaption and misallocation of finances. We encourage working with bandwidths and testing climate adaptation options against a broad range of possible future climates. Climate

  14. Regional projection of climate impact indices over the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Casanueva, Ana; Frías, M.; Dolores; Herrera, Sixto; Bedia, Joaquín; San Martín, Daniel; Gutiérrez, José Manuel; Zaninovic, Ksenija

    2014-05-01

    Climate Impact Indices (CIIs) are being increasingly used in different socioeconomic sectors to transfer information about climate change impacts and risks to stakeholders. CIIs are typically based on different weather variables such as temperature, wind speed, precipitation or humidity and comprise, in a single index, the relevant meteorological information for the particular impact sector (in this study wildfires and tourism). This dependence on several climate variables poses important limitations to the application of statistical downscaling techniques, since physical consistency among variables is required in most cases to obtain reliable local projections. The present study assesses the suitability of the "direct" downscaling approach, in which the downscaling method is directly applied to the CII. In particular, for illustrative purposes, we consider two popular indices used in the wildfire and tourism sectors, the Fire Weather Index (FWI) and the Physiological Equivalent Temperature (PET), respectively. As an example, two case studies are analysed over two representative Mediterranean regions of interest for the EU CLIM-RUN project: continental Spain for the FWI and Croatia for the PET. Results obtained with this "direct" downscaling approach are similar to those found from the application of the statistical downscaling to the individual meteorological drivers prior to the index calculation ("component" downscaling) thus, a wider range of statistical downscaling methods could be used. As an illustration, future changes in both indices are projected by applying two direct statistical downscaling methods, analogs and linear regression, to the ECHAM5 model. Larger differences were found between the two direct statistical downscaling approaches than between the direct and the component approaches with a single downscaling method. While these examples focus on particular indices and Mediterranean regions of interest for CLIM-RUN stakeholders, the same study

  15. Climate change. Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures.

    PubMed

    Steinman, Byron A; Mann, Michael E; Miller, Sonya K

    2015-02-27

    The recent slowdown in global warming has brought into question the reliability of climate model projections of future temperature change and has led to a vigorous debate over whether this slowdown is the result of naturally occurring, internal variability or forcing external to Earth's climate system. To address these issues, we applied a semi-empirical approach that combines climate observations and model simulations to estimate Atlantic- and Pacific-based internal multidecadal variability (termed "AMO" and "PMO," respectively). Using this method, the AMO and PMO are found to explain a large proportion of internal variability in Northern Hemisphere mean temperatures. Competition between a modest positive peak in the AMO and a substantially negative-trending PMO are seen to produce a slowdown or "false pause" in warming of the past decade.

  16. Early warning signals of Atlantic Meridional Overturning Circulation collapse in a fully coupled climate model.

    PubMed

    Boulton, Chris A; Allison, Lesley C; Lenton, Timothy M

    2014-12-08

    The Atlantic Meridional Overturning Circulation (AMOC) exhibits two stable states in models of varying complexity. Shifts between alternative AMOC states are thought to have played a role in past abrupt climate changes, but the proximity of the climate system to a threshold for future AMOC collapse is unknown. Generic early warning signals of critical slowing down before AMOC collapse have been found in climate models of low and intermediate complexity. Here we show that early warning signals of AMOC collapse are present in a fully coupled atmosphere-ocean general circulation model, subject to a freshwater hosing experiment. The statistical significance of signals of increasing lag-1 autocorrelation and variance vary with latitude. They give up to 250 years warning before AMOC collapse, after ~550 years of monitoring. Future work is needed to clarify suggested dynamical mechanisms driving critical slowing down as the AMOC collapse is approached.

  17. Destabilization of glacial climate by the radiative impact of Atlantic Meridional Overturning Circulation disruptions

    NASA Astrophysics Data System (ADS)

    Galbraith, Eric D.; Merlis, Timothy M.; Palter, Jaime B.

    2016-08-01

    During each of the dramatic global warmings that ended the Pleistocene ice ages, the Atlantic Meridional Overturning Circulation (AMOC) was disrupted. It is not clear whether this was a contributing cause or simply an effect of deglaciation. Here we show that in an ensemble of simulations with a global climate model, AMOC disruption causes a consistent and sustained positive radiative imbalance of 0.4 W m-2. The imbalance is accommodated by heat accumulation in the ocean interior, representing an overall planetary warming, subsequently released by deep convection in the North Atlantic when the AMOC resumes. The results suggest a means by which AMOC disruptions could have helped to tip the planet out of stable glaciated states. However, the fact that AMOC disruptions occurred during prior Heinrich Stadials without causing deglaciation shows that other factors, such as ice sheet dynamics, or controls on CO2, were also key for deglaciation.

  18. Regional monitoring of environmental physics climate related anomalies

    NASA Astrophysics Data System (ADS)

    El-Askary, Hesham

    2004-11-01

    sensing using the Moderate Resolution Imaging Spectroradiometer (MODIS) on board Terra, with microwave sensing using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). This approach has the potential to be superior to currently used methods by distinguishing aerosol particles from dust particles based on their grain sizes. The Middle East, particularly Egypt and the Gulf region, is selected for such application since it is located on the northern part of the desert belt, and hence is considered to be an excellent location for dust measurements. Egypt is subject to industrial pollution and therefore the complex interactions of dust with industrial aerosols can affect precipitation and Earth's radiation budget. Another location, Indo-Gangetic basin, India is also selected since it experiences heavy dust storms that originate from the Saharan desert during the pre-monsoon period. In the application over India, the Multi-angle Imaging SpectroRadiometer (MISR) technology was used. The second application in this dissertation is the study of precipitation variability over the Mid-Atlantic region to help understanding the behavior causing anomalies like flooding and drought events. The impacts of global climate phenomena such as El Nino and La-Nina are studied emphasizing how strongly they affect or cause these events on regional scales.

  19. Climate change in Central America and Mexico: regional climate model validation and climate change projections

    NASA Astrophysics Data System (ADS)

    Karmalkar, Ambarish V.; Bradley, Raymond S.; Diaz, Henry F.

    2011-08-01

    Central America has high biodiversity, it harbors high-value ecosystems and it's important to provide regional climate change information to assist in adaptation and mitigation work in the region. Here we study climate change projections for Central America and Mexico using a regional climate model. The model evaluation shows its success in simulating spatial and temporal variability of temperature and precipitation and also in capturing regional climate features such as the bimodal annual cycle of precipitation and the Caribbean low-level jet. A variety of climate regimes within the model domain are also better identified in the regional model simulation due to improved resolution of topographic features. Although, the model suffers from large precipitation biases, it shows improvements over the coarse-resolution driving model in simulating precipitation amounts. The model shows a dry bias in the wet season and a wet bias in the dry season suggesting that it's unable to capture the full range of precipitation variability. Projected warming under the A2 scenario is higher in the wet season than that in the dry season with the Yucatan Peninsula experiencing highest warming. A large reduction in precipitation in the wet season is projected for the region, whereas parts of Central America that receive a considerable amount of moisture in the form of orographic precipitation show significant decreases in precipitation in the dry season. Projected climatic changes can have detrimental impacts on biodiversity as they are spatially similar, but far greater in magnitude, than those observed during the El Niño events in recent decades that adversely affected species in the region.

  20. Origin of millennial-scale climate instabilities in the subtropical Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Billups, K.; Scheinwald, A.; Dahl, P.

    2013-12-01

    We have generated a high resolution (~250-500 year) planktonic foraminiferal stable isotope record (Globigerinoides ruber white, senso lato) spanning Marine Isotope Stages (MIS) 6 through 8 in the northwestern subtropical Atlantic (Ocean Drilling Program Leg 172 Site 1059). The record fills a gap in an about 1.3 million year long time series of millennial-scale surface ocean hydrography in this region. We test the hypothesis that sub-orbital climate signals are linked to a response to precession forcing in tropical latitudes. Power spectra provide evidence for an increase in the length of half precession cycles as the 19 kyr precession period disappears from the insolation forcing at about 320 Ka in first order support of the hypothesis. In the time series, half precession (and quarter precession cycles when present) are evident as double (and quadruple) peaks within the given precession framework. However, in the time series there is no match between the amplitude modulation of the precession signal and its harmonics. During the time interval between 340-0 Ka (MIS 9-1) when the temporal resolution is high (250 year time step), the power spectra also contain significant peaks in the Dansgaard-Oeschger band (~1-8-1.5 kyr). Comparison of filter output with the time series, however, illustrates that there are only few instances where these types of variations are distinct in the foraminiferal δ18O record. We conclude that the evolution of half precession cycles over the time interval is largely consistent with a response to low latitude insolation, such as introduced by insolation maxima at the equinoxes and solstices (e.g., Short et al., 1991). Our analysis also shows that quarter precession cycles are present in the time series, at least intermittently, but we cannot uniquely tie them to changes in the primary precession signal. Our study highlights the importance of evaluating variations in the original time series to guide interpretations of significant peaks in

  1. Decoupling of Northern North Atlantic Sea Surface Temperature and Deep Circulation during Abrupt Glacial Climate Change

    NASA Astrophysics Data System (ADS)

    Jonkers, L.; Barker, S.; Hall, I. R.

    2014-12-01

    Abrupt climate change is a prominent feature of the ice ages. The prevailing view is that these changes are related to fluctuations in ocean circulation, possibly triggered by changes in freshwater forcing as a result of ice-rafting events in the North Atlantic. Here we investigate this view by presenting results from a sediment core in the Northern North Atlantic (ODP 983 60.4°N, 23.6°W, 1984m depth, ~12-35 kyr), which is ideally positioned to monitor changes in the flow speed of Iceland-Scotland Overflow Waters. The mean size of silt (10-63 μm) has been proposed as a useful flow speed indicator, but can be influenced the presence of ice-rafted detritus (IRD). We present grain size data obtained using a Coulter counter as well as a laser diffraction particle sizer, which we compare to the proportion of Neogloboquadrina pachyderma (proxy for sea surface temperature) and manually counted coarse IRD. Grain size results are comparable for the two techniques and the influence of IRD is clearly visible in the mean size data. We use end-member modelling to derive an IRD-free estimate of flow speed variability and find clear reductions in the flow speed associated with IRD input. Sea surface temperature however, appears to vary independently from IRD input and hence deep circulation. In particular, IRD appears and current speed decreases after the onset of cooling and additional temperature variability is observed that is not associated with IRD events or changes in the deep circulation. These results question the classical view of freshwater forcing as the driver of abrupt climate change. We suggest that North Atlantic temperature variability may be related to shifts in position of the polar front and that, while IRD events may be coeval with changes in the deep circulation, these changes are not required to explain the abrupt temperature variability in the Northern North Atlantic.

  2. Climate programs update: USDA Southwest Regional Climate Hub update

    Technology Transfer Automated Retrieval System (TEKTRAN)

    PROGRAM OVERVIEW: The overarching goal of the USDA SW Climate Hub is to assist farmers, ranchers and foresters in addressing the effects of climate change including prolonged drought, increased insect outbreaks and severe wildfires. In the first year of operations, the SW Climate Hub (est. Februa...

  3. Response of winter North Atlantic storm track to climate change in the CNRM-CM5 simulations

    NASA Astrophysics Data System (ADS)

    Chauvin, Fabrice; Oudar, Thomas; Sanchez-Gomez, Emilia; Terray, Laurent

    2016-04-01

    Climate variability in Europe in winter is largely controlled by North Atlantic storm tracks. These are associated with transport of energy, momentum, and water vapour, between the equator and mid latitudes. Extratropical cyclones have caused severe damages over some regions in north-western Europe, since they can combine extreme precipitation and strong winds. This is why it is relevant to study the impact of climate change on the extratropical cyclones, principally on their intensity, position or lifespan. Indeed, several recent studies have focused on this subject by using atmospheric reanalysis and general circulation models (GCMs). The main conclusions from the CMIP3 simulations showed a decreasing of the total number of cyclones and a poleward shift of their tracks in response to global warming. In the recent CMIP5 exercise, the consensus is not so clear, probably due to more complex feedbacks acting in the different models. Thus, the question of changes in North Atlantic storm-tracks with warming remains open. The main goal of this work is to explore the changes in the North Atlantic storm-tracks in the past and future decades and to analyze the contributions of the different external forcings (natural and anthropogenic) versus the internal variability. On this purpose, we use the Detection and Attribution (D&A) simulations performed with the coupled model CNRM-CM5. To characterize the extratropical cyclones and their tracks, a tracking scheme based on the detection of maximum of relative vorticity at 850 hPa is conducted. We show that the coupled model fairly well reproduces the storm genesis locations as well as the tracks pathways comparing to several atmospheric reanalysis products. In the recent historical period (1950-2005), the model shows a decrease in the number of storms in the southern North-Atlantic, when all the forcings (anthropogenic and natural) are prescribed. Even if the role of internal variability is important in the last decades (the

  4. Health and climate benefits of offshore wind facilities in the Mid-Atlantic United States

    NASA Astrophysics Data System (ADS)

    Buonocore, Jonathan J.; Luckow, Patrick; Fisher, Jeremy; Kempton, Willett; Levy, Jonathan I.

    2016-07-01

    Electricity from fossil fuels contributes substantially to both climate change and the health burden of air pollution. Renewable energy sources are capable of displacing electricity from fossil fuels, but the quantity of health and climate benefits depend on site-specific attributes that are not often included in quantitative models. Here, we link an electrical grid simulation model to an air pollution health impact assessment model and US regulatory estimates of the impacts of carbon to estimate the health and climate benefits of offshore wind facilities of different sizes in two different locations. We find that offshore wind in the Mid-Atlantic is capable of producing health and climate benefits of between 54 and 120 per MWh of generation, with the largest simulated facility (3000 MW off the coast of New Jersey) producing approximately 690 million in benefits in 2017. The variability in benefits per unit generation is a function of differences in locations (Maryland versus New Jersey), simulated years (2012 versus 2017), and facility generation capacity, given complexities of the electrical grid and differences in which power plants are offset. This work demonstrates health and climate benefits of offshore wind, provides further evidence of the utility of geographically-refined modeling frameworks, and yields quantitative insights that would allow for inclusion of both climate and public health in benefits assessments of renewable energy.

  5. The Influence of Glacial Ice Sheets on Atlantic Meridional Overturning Circulation Through Atmospheric Circulation Change under Glacial Climate

    NASA Astrophysics Data System (ADS)

    Sherriff-Tadano, S.; Abe-Ouchi, A.; Yoshimori, M.; Oka, A.; Chan, W. L.

    2014-12-01

    It is well known that glacial ice sheets (Laurentide, Fennoscandian and Antarctic ice sheets) exert a large influence on the climate including the atmospheric circulation. Moreover, recent climate modeling studies suggest that glacial ice sheets have a large impact on the Atlantic meridional overturning circulation (AMOC). However, the process by which the ice sheets impact on the AMOC is not yet fully understood. On the other hand, recent studies showed that surface wind changes play a crucial role on changes to the AMOC under glacial climate. Therefore, in this study, we investigate in detail, the process by which the ice sheet modifies the AMOC through surface wind change. Here we conduct numerical experiments using an atmospheric general circulation model (AGCM) and an ocean general circulation model (OGCM) separately. Our method consists of 2 steps. First, from AGCM experiments, we evaluate the effect of glacial ice sheets on the surface wind. Second, from OGCM experiments, we evaluate the influence of the wind stress change on the AMOC by applying the surface wind change as a boundary condition, while leaving other boundary conditions (surface heat and water fluxes) unchanged. In addition, we conduct several sensitivity experiments. Using the AGCM, we explore individual ice sheet effect, ice sheet topography effect and albedo effect on surface wind change. Moreover, using the OGCM, we change the surface wind gradually or apply the surface wind change only at a specific region in order to explore the wind change effect in detail. We find that glacial ice sheets largely intensify the AMOC by surface wind change under glacial climate. Compare to other regions, it reveals that the wind change at the North Atlantic (NA) is a key region. There, the northern glacial ice sheet topography intensifies the Icelandic Low and anti-cyclonic circulation over the Laurentide ice sheet. However, this wind effect is effective only when the NA is not widely covered by sea ice

  6. Equilibrium of vegetation and climate at the European rear edge. A reference for climate change planning in mountainous Mediterranean regions.

    PubMed

    Ruiz-Labourdette, Diego; Martínez, Felipe; Martín-López, Berta; Montes, Carlos; Pineda, Francisco D

    2011-05-01

    Mediterranean mountains harbour some of Europe's highest floristic richness. This is accounted for largely by the mesoclimatic variety in these areas, along with the co-occurrence of a small area of Eurosiberian, Boreal and Mediterranean species, and those of Tertiary Subtropical origin. Throughout the twenty-first century, we are likely to witness a climate change-related modification of the biogeographic scenario in these mountains, and there is therefore a need for accurate climate regionalisations to serve as a reference of the abundance and distribution of species and communities, particularly those of a relictic nature. This paper presents an objective mapping method focussing on climate regions in a mountain range. The procedure was tested in the Cordillera Central Mountains of the Iberian Peninsula, in the western Mediterranean, one of the ranges occupying the largest area of the Mediterranean Basin. This regionalisation is based upon multivariate analyses and upon detailed cartography employing 27 climatic variables. We used spatial interpolation of data based on geographic information. We detected high climatic diversity in the mountain range studied. We identified 13 climatic regions, all of which form a varying mosaic throughout the annual temperature and rainfall cycle. This heterogeneity results from two geographically opposed gradients. The first one is the Mediterranean-Euro-Siberian variation of the mountain range. The second gradient involves the degree of oceanicity, which is negatively related to distance from the Atlantic Ocean. The existing correlation between the climatic regions detected and the flora existing therein enables the results to be situated within the projected trends of global warming, and their biogeographic and ecological consequences to be analysed.

  7. Mid-Atlantic Region: A Report Identifying and Addressing the Educational Needs

    ERIC Educational Resources Information Center

    US Department of Education, 2011

    2011-01-01

    This report presents the deliberations of the Mid-Atlantic Regional Advisory Committee (RAC), one of 10 RACs established under the Educational Technical Assistance Act of 2002 (20 U.S.C. sections 9601 et. seq.) to assess the educational needs of the region. The committee's report outlines the educational needs across the District of Columbia and…

  8. Regional climates in GCMs. Final report

    SciTech Connect

    Crane, R.G.

    1995-12-31

    This research describes empirical methods developed to obtain short-term, regional results from global climate models. Observational data sets were compared to the GENESIS climate model; spatial and temporal variability were examined to validate the circulation model on the synoptic scale. A feed-forward neural network was used to determine transfer functions for circulation-precipitation relationships. The empirical methodologies derived were then applied to the analysis of mountain snowpack in the upper Colorado Basin. The comparison of observational data and the model showed that the synoptic scale circulation of the GENESIS model is realistic over the eastern United States; however, the model features are displaced south by about five degrees and actual pressures in the model are much lower than observed pressures. Preliminary results from the neural network produced correlations between observed and predicted rainfall of about 0.7 to 0.8, depending on the net configuration. Similar results were obtained for the upper Colorado Basin study in the prediction of winter snowfall. 6 refs., 3 figs.

  9. Regional Collaborations to Combat Climate Change: The Climate Science Centers as Strategies for Climate Adaptation

    NASA Astrophysics Data System (ADS)

    Morelli, T. L.; Palmer, R. N.

    2014-12-01

    The Department of Interior Northeast Climate Science Center (NE CSC) is part of a federal network of eight Climate Science Centers created to provide scientific information, tools, and techniques that managers and other parties interested in land, water, wildlife and cultural resources can use to anticipate, monitor, and adapt to climate change. The consortium approach taken by the CSCs allows the academic side of the Centers to gather expertise across departments, disciplines, and even institutions. This interdisciplinary approach is needed for successfully meeting regional needs for climate impact assessment, adaptive management, education, and stakeholder outreach. Partnership with the federal government facilitates interactions with the key on-the-ground stakeholders who are able to operationalize the results and conclusions of that research, monitor the progress of management actions, and provide feedback to refine future methodology and decisions as new information on climate impacts is discovered. For example, NE CSC researchers are analyzing the effect of climate change on the timing and volume of seasonal and annual streamflows and the concomitant effects on ecological and cultural resources; developing techniques to monitor tree range dynamics as affected by natural disturbances which can enable adaptation of projected climate impacts; studying the effects of changes in the frequency and magnitude of drought and stream temperature on brook trout habitats, spatial distribution and population persistence; and conducting assessments of northeastern regional climate projections and high-resolution downscaling. Project methods are being developed in collaboration with stakeholders and results are being shared broadly with federal, state, and other partners to implement and refine effective and adaptive management actions.

  10. Activities of the Climate Forecast Unit (CFU) on regional decadal prediction

    NASA Astrophysics Data System (ADS)

    Guemas, V.; Prodhomme, C.; Doblas-Reyes, F.; Volpi, D.; Caron, L. P.; Davis, M.; Menegoz, M.; Saurral, R. I.; Bellprat, O.

    2014-12-01

    The Climate Forecasting Unit (CFU) is a research unit devoted to develop climate forecast systems to contribute to the creation of climate services that aims to 1) develop climate forecast systems and prediction methodologies, 2) investigate the potential sources of skill and understand the limitation of state-of-the-art forecast systems, 3) formulate reliable climate forecasts that meet specific user needs and 4) contribute to the development of climate services. This presentation will provide an overview of the latest results of this research unit in the field of regional decadal prediction focusing on 1) an assessment of the relative merits of the full-field and the anomaly initialisation techniques, 2) a description of the forecast quality of North Atlantic tropical cyclone activity and South Pacific climate, 3) an evaluation of the impact of volcanic aerosol prescription during decadal forecasts, and 4) the strategy for the development of a climate service to ensure that forecasts are both useful and action-oriented. Results from several European projects, SPECS, PREFACE and EUPORIAS, will be used to illustrate these findings.

  11. Impact of tropical Atlantic sea-surface temperature biases on the simulated atmospheric circulation and precipitation over the Atlantic region: An ECHAM6 model study

    NASA Astrophysics Data System (ADS)

    Eichhorn, Astrid; Bader, Jürgen

    2016-11-01

    As many coupled atmosphere-ocean general circulation models, the coupled Earth System Model developed at the Max Planck Institute for Meteorology suffers from severe sea-surface temperature (SST) biases in the tropical Atlantic. We performed a set of SST sensitivity experiments with its atmospheric model component ECHAM6 to understand the impact of tropical Atlantic SST biases on atmospheric circulation and precipitation. The model was forced by a climatology of observed global SSTs to focus on simulated seasonal and annual mean state climate. Through the superposition of varying tropical Atlantic bias patterns extracted from the MPI-ESM on top of the control field, this study investigates the relevance of the seasonal variation and spatial structure of tropical Atlantic biases for the simulated response. Results show that the position and structure of the Intertropical Convergence Zone (ITCZ) across the Atlantic is significantly affected, exhibiting a dynamically forced shift of annual mean precipitation maximum to the east of the Atlantic basin as well as a southward shift of the oceanic rain belt. The SST-induced changes in the ITCZ in turn affect seasonal rainfall over adjacent continents. However not only the ITCZ position but also other effects arising from biases in tropical Atlantic SSTs, e.g. variations in the wind field, change the simulation of precipitation over land. The seasonal variation and spatial pattern of tropical Atlantic SST biases turns out to be crucial for the simulated atmospheric response and is essential for analyzing the contribution of SST biases to coupled model mean state biases. Our experiments show that MPI-ESM mean-state biases in the Atlantic sector are mainly driven by SST biases in the tropical Atlantic while teleconnections from other basins seem to play a minor role.

  12. Regional climate simulations over Vietnam using the WRF model

    NASA Astrophysics Data System (ADS)

    Raghavan, S. V.; Vu, M. T.; Liong, S. Y.

    2016-10-01

    We present an analysis of the present-day (1961-1990) regional climate simulations over Vietnam. The regional climate model Weather Research and Forecasting (WRF) was driven by the global reanalysis ERA40. The performance of the regional climate model in simulating the observed climate is evaluated with a main focus on precipitation and temperature. The regional climate model was able to reproduce the observed spatial patterns of the climate, although with some biases. The model also performed better in reproducing the extreme precipitation and the interannual variability. Overall, the WRF model was able to simulate the main regional signatures of climate variables, seasonal cycles, and frequency distributions. This study is an evaluation of the present-day climate simulations of a regional climate model at a resolution of 25 km. Given that dynamical downscaling has become common for studying climate change and its impacts, the study highlights that much more improvements in modeling might be necessary to yield realistic simulations of climate at high resolutions before they can be used for impact studies at a local scale. The need for a dense network of observations is also realized as observations at high resolutions are needed when it comes to evaluations and validations of models at sub-regional and local scales.

  13. A new plate motions model for the central Atlantic region

    NASA Astrophysics Data System (ADS)

    Tassi, L.; Schettino, A.

    2010-12-01

    Although the plate kinematics associated with the opening of the central Atlantic ocean after the break-up of Pangaea has been the subject of several studies since the late 1960s, there are still open problems and debated solutions to the tectonic evolution of this area. In particular, the initial fit of Pangaea, the spreading directions during the early stages of opening, the existence of ridge jumps, and the entity of deformation processes in northwest Africa are still subject to different interpretations by distinct research groups. We performed a reassessment of the central Atlantic plate kinematics since the early Jurassic through a re-examination of marine magnetic anomalies and fracture zone trends. A total of 432 ship tracks from the NGDC GEODAS database for the time interval from 1964 through 1994 in the area comprised between the Fifteen-Twenty FZ and the Azores triple junction were analyzed. The data quality was assessed through the examination of Kp indices, and 191 magnetic profiles were extracted having an azimuth that differed from the fracture zones trend by less than 30° and did not cross any fracture zone. Magnetic data collected during moderately disturbed days (Kp > 5) were also filtered away. The 191 ship track segments were projected onto flow lines that parallel existing fracture zones in order to avoid shape distortion of the magnetic anomalies. Finally, the magnetic data were high-pass filtered to remove trends. A new advanced software tool for the analysis and interpretation of the anomalies was developed in order to improve the reliability of magnetic anomaly identifications. The main result of this work is a new map of the magnetic lineations in the central Atlantic, which overcomes the flaws of previous maps. The structural pattern that results from this study evidences that: 1) a unique spreading direction existed during the early and middle Jurassic, and until the M25 - M21 time interval in the late Jurassic. Such a spreading

  14. First Evaluation of the CCAM Aerosol Simulation over Africa: Implications for Regional Climate Modeling

    NASA Astrophysics Data System (ADS)

    Horowitz, H.; Garland, R. M.; Thatcher, M. J.; Naidoo, M.; van der Merwe, J.; Landman, W.; Engelbrecht, F.

    2015-12-01

    An accurate representation of African aerosols in climate models is needed to understand the regional and global radiative forcing and climate impacts of aerosols, at present and under future climate change. However, aerosol simulations in regional climate models for Africa have not been well-tested. Africa contains the largest single source of biomass-burning smoke aerosols and dust globally. Although aerosols are short-lived relative to greenhouse gases, black carbon in particular is estimated to be second only to carbon dioxide in contributing to warming on a global scale. Moreover, Saharan dust is exported great distances over the Atlantic Ocean, affecting nutrient transport to regions like the Amazon rainforest, which can further impact climate. Biomass burning aerosols are also exported from Africa, westward from Angola over the Atlantic Ocean and off the southeastern coast of South Africa to the Indian Ocean. Here, we perform the first extensive quantitative evaluation of the Conformal-Cubic Atmospheric Model (CCAM) aerosol simulation against monitored data, focusing on aerosol optical depth (AOD) observations over Africa. We analyze historical regional simulations for 1999 - 2012 from CCAM consistent with the experimental design of CORDEX at 50 km global horizontal resolution, through the dynamical downscaling of ERA-Interim data reanalysis data, with the CMIP5 emissions inventory (RCP8.5 scenario). CCAM has a prognostic aerosol scheme for organic carbon, black carbon, sulfate, and dust, and non-prognostic sea salt. The CCAM AOD at 550nm was compared to AOD (observed at 440nm, adjusted to 550nm with the Ångström exponent) from long-term AERONET stations across Africa. Sites strongly impacted by dust and biomass burning and with long continuous records were prioritized. In general, the model captures the monthly trends of the AERONET data. This presentation provides a basis for understanding how well aerosol particles are represented over Africa in

  15. Stability of the Atlantic meridional overturning circulation during Marine Isotope Stage 3 in a comprehensive climate model

    NASA Astrophysics Data System (ADS)

    Prange, Matthias; Zhang, Xiao; Merkel, Ute; Schulz, Michael

    2013-04-01

    The origin of millennial-scale Dansgaard-Oeschger events during Marine Isotope Stage 3 (MIS3) is controversial, but there is strong evidence that variations in the strength of the Atlantic meridional overturning circulation (AMOC) were involved. Here, the stability of the AMOC to North Atlantic freshwater perturbations is systematically studied using a state-of-the-art comprehensive coupled climate model (Community Climate System Model version 3, CCSM3) under MIS3 boundary conditions. Results from a series of equilibrium freshwater hosing/extraction experiments forced with 38 ka before present boundary conditions and freshwater perturbations ranging from -0.2 to +0.2 Sverdrups (Sv) are used to construct an AMOC stability diagram. Without freshwater perturbation, the model simulates an equilibrium North Atlantic overturning-maximum of 15 Sv under MIS3 boundary conditions, which is 1 Sv stronger than in the pre-industrial control run, and the southward flow of North Atlantic deepwater occurs at shallower levels than under modern conditions. This MIS3 climate state is remarkably unstable with respect to minor North Atlantic freshwater perturbations, dropping to 9 Sv in response to a 0.04 Sv freshwater hosing and increasing to 18 Sv upon a 0.02 Sv freshwater extraction. The associated changes in global climate are largely consistent with MIS3 stadial-interstadial climate differences suggested by proxy records. Moreover, no evidence for multiple climate equilibria under MIS3 boundary conditions is found in the coupled atmosphere-ocean system. Instead, our results suggest substantial global climate shifts associated with a non-catastrophic threshold for freshwater perturbations varying in the narrow interval between -0.02 and +0.04 Sv. Thus, minor perturbations in the hydrologic cycle (e.g. related to ice-sheet processes) had the potential to trigger global Dansgaard-Oeschger climate transitions.

  16. Assessments of regional climate change and its impacts in Northern Europe

    NASA Astrophysics Data System (ADS)

    Omstedt, Anders; von Storch, Hans; Reckermann, Marcus; Quante, Markus

    2015-04-01

    Regional climate change assessments are urgently needed to complement the big picture with regional results and scenarios of higher resolution and with relevance for local decision makers and stakeholders. A new type of assessment report originated in the original BACC report of 2008 (BALTEX Assessment of Climate Change for the Baltic Sea region) which has served as role model for other assessments published or in preparation. It represents an approach to assessing and making available current knowledge on regional climate change and its regional impacts on the physical, biogeochemical and biological environment (ecosystems, socio-economic sphere). Reports of this type which are available or underway are the original BACC book (2008), the second BACC book (2015), the climate report for the greater Hamburg area (2011), and the NOSCCA report (North Sea Climate Change Assessment) which is expected to be published in 2016. The assessments are produced by teams of scientists from the region, led by lead authors who recruit experts from relevant topics to contribute. The process is not externally funded and completely based on published scientific evidence, and not biased by political or economic interest groups. The BACC-type reports aim to bring together consolidated knowledge that has broad consensus in the scientific community, but also acknowledging issues for which contradicting opinions are found in the literature, so that no consensus can be reached ("consensus on dissensus"). An international steering committee is responsible for overlooking the process, and all manuscripts are anonymously peer-reviewed by independent international experts. An outstanding outreach aspect of these reports is the close collaboration with regional stakeholders (for the BACC reports: HELCOM, the intergovernmental Baltic Marine Environment Protection Commission and the major regional science-policy interface in the Baltic Sea region; for the Hamburg climate report: the Hamburg city

  17. A two-tier atmospheric circulation classification scheme for the European-North Atlantic region

    NASA Astrophysics Data System (ADS)

    Guentchev, Galina S.; Winkler, Julie A.

    A two-tier classification of large-scale atmospheric circulation was developed for the European-North-Atlantic domain. The classification was constructed using a combination of principal components and k-means cluster analysis applied to reanalysis fields of mean sea-level pressure for 1951-2004. Separate classifications were developed for the winter, spring, summer, and fall seasons. For each season, the two classification tiers were identified independently, such that the definition of one tier does not depend on the other tier having already been defined. The first tier of the classification is comprised of supertype patterns. These broad-scale circulation classes are useful for generalized analyses such as investigations of the temporal trends in circulation frequency and persistence. The second, more detailed tier consists of circulation types and is useful for numerous applied research questions regarding the relationships between large-scale circulation and local and regional climate. Three to five supertypes and up to 19 circulation types were identified for each season. An intuitive nomenclature scheme based on the physical entities (i.e., anomaly centers) which dominate the specific patterns was used to label each of the supertypes and types. Two example applications illustrate the potential usefulness of a two-tier classification. In the first application, the temporal variability of the supertypes was evaluated. In general, the frequency and persistence of supertypes dominated by anticyclonic circulation increased during the study period, whereas the supertypes dominated by cyclonic features decreased in frequency and persistence. The usefulness of the derived circulation types was exemplified by an analysis of the circulation associated with heat waves and cold spells reported at several cities in Bulgaria. These extreme temperature events were found to occur with a small number of circulation types, a finding that can be helpful in understanding past

  18. North Atlantic Climate Variability: Preliminary Analysis of Historical Weather Data and Stable Isotope Time Series of Cave Dripwater and Holocene-Age Stalagmites from Bermuda

    NASA Astrophysics Data System (ADS)

    Gaurin, S. E.; Burns, S. J.; Woodworth, M.; Wood, J.; Edwards, L.; Cheng, H.

    2008-12-01

    Bermuda, located in the center of the Sargasso Sea of the North Atlantic Ocean, is a unique laboratory for analyzing Holocene climate change. This subtropical area lacks a strong seasonal cycle, making it an ideal place to look for low-frequency cycles identified in observational records of North Atlantic climate. A preliminary statistical analysis of historical climate data, provided by the Bermuda Weather Service and spanning a period from 1852 to 2006, will be presented. Emphasis will be placed on the identification of cycles corresponding to such climate modes as the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). To extend the record back farther than the observational period, it is necessary to identify and analyze paleoclimate proxies. Carbonate caves on the island of Bermuda contain numerous speleothems, which have the potential to serve as extremely high-resolution (sub-decadal) recorders of climate change via the stable oxygen and carbon isotope concentrations contained in their crystalline form. Stalagmite stable isotope data is reflective of changes in stable isotopes of the cave dripwater feeding the stalagmite. Approximately monthly time series of δ18O data from three dripwater sites in each of two Bermuda caves, Fantasy Cave and Leamington Cave, will be presented, covering the period from April 2006 to March 2008. Values from Fantasy Cave range from -4.7 permil to -3.0 permil. Interestingly, a positive excursion of ~0.8 permil in the dripwater δ18O is associated with the passage of Hurricane Florence over the island in September 2006; possible causes of this spike include a change in vapor source or hurricane wind-induced sea spray. The dripwater data will help us to calibrate and interpret the stable isotope data from stalagmite calcite in our samples. Several stalagmites retrieved from caves in the Hamilton Parish region of Bermuda were dated by U-series methods and found to cover a period from 4.7 thousand years

  19. The effect of Congo River freshwater discharge on Tropical Atlantic and Africa climate variability

    NASA Astrophysics Data System (ADS)

    Materia, Stefano; Gualdi, Silvio; Navarra, Antonio

    2010-05-01

    Eastern Tropical Atlantic (ETA) collects a huge quantity of freshwater due to discharge from several rivers. Every year, the Congo river alone releases 1270 km3 of freshwater into the ocean (Weldeab et al., 2007), which is the second-largest flow in the world second only to the Amazon River. This study aims to understand the role of Congo freshwater discharge in driving circulation over ETA. In particular, the effect of the secondary peak discharge at Brazzaville river station is here analysed. This maximum occurs in late spring and releases freshwater into the Gulf of Guinea (GG) during boreal summer, namely the season characterized by the greatest sea surface temperature (SST) variability in the Gulf. 50-year observations show that large peak discharge positive anomalies are preceded by anomalously high SSTs over north-eastern Tropical Atlantic, linked with wet springs over Congo river catchment. Intense freshwater amounts into the ocean provoke a water warming beginning at the African coast in May and extending over the GG during June and July. This SST anomaly is related to highly wet rainy season over western Africa. Conversely, low spring discharges are associated with noticeable positive SST anomalies over Tropical South Atlantic in winter, with maxima around 20-25° S, and warm temperatures persist through the summer. In these years, over April the African coast starts being subject to anomalously cold SSTs which extend to the GG during the succeeding months, with the coldest anomaly registered in June. Western Africa heads toward very dry summer, again suggesting a strong linkage with GG SSTs. The long-term objective of this study is a better understanding of Tropical Atlantic variability and climate variability over Africa, through the introduction of a forcing, the continental freshwater discharge, often neglected by previous studies.

  20. Advanced Regional and Decadal Predictions of Coastal Inundation for the U.S. Atlantic and Gulf Coasts (Invited)

    NASA Astrophysics Data System (ADS)

    Horton, B.; Corbett, D. R.; Donnelly, J. P.; Kemp, A.; Lin, N.; Lindeman, K.; Mann, M. E.; Peltier, W. R.; Rahmstorf, S.

    2013-12-01

    Future inundation of the U.S. Atlantic and Gulf coasts will depend upon sea-level rise and the intensity and frequency of tropical cyclones, each of which will be affected by climate change. Through ongoing, collaborative research we are employing new interdisciplinary approaches to bring about a step change in the reliability of predictions of such inundation. The rate of sea level rise along the U.S. Atlantic and Gulf coasts increased throughout the 20th century. Whilst there is widespread agreement that it continue to accelerate during the 21st century, great uncertainty surrounds its magnitude and geographic variability. Key uncertainties include the role of continental ice sheets, mountain glaciers, and ocean density changes. Insufficient understanding of these complex physical processes precludes accurate prediction of sea-level rise. New approaches using semi-empirical models that relate instrumental records of climate and sea-level rise have projected up to 2 m of sea-level rise by AD 2100. But the time span of instrumental sea-level records is insufficient to adequately constrain the climate:sea-level relationship. We produced new, high-resolution proxy sea-level reconstructions to provide crucial additional constraints to such semi-empirical models. Our dataset spans the alternation between the 'Medieval Climate Anomaly' and 'Little Ice Age'. Before the models can provide appropriate data for coastal management and planning, they must be complemented with regional estimates of sea-level rise. Therefore, the proxy sea-level data has been collected from four study areas (Connecticut, New Jersey, North Carolina and Florida) to accommodate the required extent of regional variability. In the case of inundation arising from tropical cyclones, the historical and observational records are insufficient for predicting their nature and recurrence, because they are such extreme and rare events. Moreover, future storm surges will be superimposed on background sea

  1. The Variability of the Atlantic Meridional Overturning Circulation, the North Atlantic Oscillation, and the El Niño-Southern Oscillation in the Bergen Climate Model.

    NASA Astrophysics Data System (ADS)

    Mignot, Juliette; Frankignoul, Claude

    2005-07-01

    The link between the interannual to interdecadal variability of the Atlantic meridional overturning circulation (AMOC) and the atmospheric forcing is investigated using 200 yr of a control simulation of the Bergen Climate Model, where the mean circulation cell is rather realistic, as is also the location of deep convection in the northern North Atlantic. The AMOC variability has a slightly red frequency spectrum and is primarily forced by the atmosphere. The maximum value of the AMOC is mostly sensitive to the deep convection in the Irminger Sea, which it lags by about 5 yr. The latter is mostly forced by a succession of atmospheric patterns that induce anomalous northerly winds over the area. The impact of the North Atlantic Oscillation on deep convection in the Labrador and Greenland Seas is represented realistically, but its influence on the AMOC is limited to the interannual time scale and is primarily associated with wind forcing. The tropical Pacific shows a strong variability in the model, with too strong an influence on the North Atlantic. However, its influence on the tropical Atlantic is realistic. Based on lagged correlations and the release of fictitious Lagrangian drifters, the tropical Pacific seems to influence the AMOC with a time lag of about 40 yr. The mechanism is as follows: El Niño events induce positive sea surface salinity anomalies in the tropical Atlantic that are advected northward, circulate in the subtropical gyre, and then subduct. In the ocean interior, part of the salinity anomaly is advected along the North Atlantic current, eventually reaching the Irminger and Labrador Seas after about 35 yr where they destabilize the water column and favor deep convection.

  2. Results of APL rain gauge network measurements in mid-Atlantic coast region and comparisons of distributions with CCIR models

    NASA Technical Reports Server (NTRS)

    Goldhirsh, Julius; Gebo, Norman; Rowland, John

    1988-01-01

    In this effort are described cumulative rain rate distributions for a network of nine tipping bucket rain gauge systems located in the mid-Atlantic coast region in the vicinity of the NASA Wallops Flight Facility, Wallops Island, Virginia. The rain gauges are situated within a gridded region of dimensions of 47 km east-west by 70 km north-south. Distributions are presented for the individual site measurements and the network average for the year period June 1, 1986 through May 31, 1987. A previous six year average distribution derived from measurements at one of the site locations is also presented. Comparisons are given of the network average, the CCIR (International Radio Consultative Committee) climatic zone, and the CCIR functional model distributions, the latter of which approximates a log normal at the lower rain rate and a gamma function at the higher rates.

  3. Results of APL rain gauge network measurements in mid-Atlantic coast region and comparisons of distributions with CCIR models

    NASA Astrophysics Data System (ADS)

    Goldhirsh, Julius; Gebo, Norman; Rowland, John

    1988-08-01

    In this effort are described cumulative rain rate distributions for a network of nine tipping bucket rain gauge systems located in the mid-Atlantic coast region in the vicinity of the NASA Wallops Flight Facility, Wallops Island, Virginia. The rain gauges are situated within a gridded region of dimensions of 47 km east-west by 70 km north-south. Distributions are presented for the individual site measurements and the network average for the year period June 1, 1986 through May 31, 1987. A previous six year average distribution derived from measurements at one of the site locations is also presented. Comparisons are given of the network average, the CCIR (International Radio Consultative Committee) climatic zone, and the CCIR functional model distributions, the latter of which approximates a log normal at the lower rain rate and a gamma function at the higher rates.

  4. Characterizing Uncertainty for Regional Climate Change Mitigation and Adaptation Decisions

    SciTech Connect

    Unwin, Stephen D.; Moss, Richard H.; Rice, Jennie S.; Scott, Michael J.

    2011-09-30

    This white paper describes the results of new research to develop an uncertainty characterization process to help address the challenges of regional climate change mitigation and adaptation decisions.

  5. Tree-ring Oxygen Isotope Records of Climate Modes Influencing North Atlantic Tropical Cyclone Activity

    NASA Astrophysics Data System (ADS)

    Mora, C. I.; Miller, D. L.; Grissino-Mayer, H. D.; Kocis, W. N.; Lewis, D. B.

    2006-12-01

    The relatively short instrumental record hinders our ability to discern the linkages between low frequency modes of climate variability and tropical cyclone activity and to differentiate natural versus anthropogenic components of these trends. The development of biological proxies for tropical cyclone activity and climate provides a basis for evaluation of these linkages over much longer time frames. The oxygen isotope composition of tree-ring cellulose, sampled at high resolution (seasonal or better), provides a new proxy for tropical cyclone activity that preserves a concurrent isotope time series reflecting the influence of climate variability. This proxy archive potentially extends many centuries beyond the instrumental and historical (documentary) record of climate and tropical cyclone activity. Isotope time series for longleaf pines (Pinus palustris Mill.) in southern Georgia and South Carolina preserve distinct tropical cyclone histories, yet similar, long term trends in cellulose δ 18O compositions. The isotope time series correlate to various climate modes proposed to impact hurricane formation and frequency. Tree-ring cellulose δ 18O values at the Georgia study site show a significant negative correlation with AMO indices from 1875 to about 1950, and a weaker, positive correlation from about 1965 to 1990. The "crossover" parallels a change in the predominant ontogeny of North Atlantic tropical cyclones from tropical-only to baroclinically-enhanced hurricanes. The intervening 1950s is marked by greater correspondence to ENSO indices. Reduced seasonality in the isotope record (i.e., the difference between earlywood and latewood δ 18O values) corresponds to warm phases of the PDO. An isotope series for 1580 to 1650 suggests little tropical cyclone activity coinciding with a period (1560-1625) of severe drought in the African Sahel. Although preliminary, these results suggest that tree-ring oxygen isotope compositions are sensitive to changes in climate

  6. CLIMATE IMPACTS ON REGIONAL AIR QUALITY (CIRAQ): MODELING OZONE SENSITIVITIES TO FUTURE CLIMATE

    EPA Science Inventory

    Using global and regional modeling tools, predictions of future climate and ozone concentrations are developed for the continental United States. Results suggest that future changes in climate will contribute to an increase in ozone concentrations; however, the future changes in...

  7. Global and regional surface cooling in a warming climate: a multi-model analysis

    NASA Astrophysics Data System (ADS)

    Medhaug, Iselin; Drange, Helge

    2016-06-01

    Instrumental temperature records show that the global climate may experience decadal-scale periods without warming despite a long-term warming trend. We analysed 17 global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5), identifying the likelihood and duration of periods without warming in the four Representative Concentration Pathway (RCP) scenarios RCP2.6, RCP4.5, RCP6.0 and RCP8.5, together with the preindustrial control and historical simulations. We find that non-warming periods may last 10, 15 and 30 years for RCP8.5, RCP6.0 and RCP4.5, respectively. In the models, anomalous ocean heat uptake and storage are the main factors explaining the decadal-scale surface temperature hiatus periods. The low-latitude East Pacific Ocean is a key region for these variations, acting in tandem with basin-scale anomalies in the sea level pressure. During anomalously cold decades, roughly 35-50 % of the heat anomalies in the upper 700 m of the ocean are located in the Pacific Ocean, and 25 % in the Atlantic Ocean. Decadal-scale ocean heat anomalies, integrated over the upper 700 m, have a magnitude of about 7.5 × 1021 J. This is comparable to the ocean heat uptake needed to maintain a 10 year period without increasing surface temperature under global warming. On sub-decadal time scales the Atlantic, Pacific and Southern Oceans all have the ability to store large amounts of heat, contributing to variations in global surface temperature. The likelihood of decadal-scale non-warming periods decrease with global warming, firstly at the low latitude region stretching eastward from the tropical Atlantic towards the western Pacific. The North Atlantic and Southern Oceans have largest likelihood of non-warming decades in a warming world.

  8. The climate influence on the mid-depth Northeast Atlantic gyres viewed by cold-water corals

    NASA Astrophysics Data System (ADS)

    Montero-Serrano, Jean-Carlos; Frank, Norbert; Colin, Christophe; Wienberg, Claudia; Eisele, Markus

    2011-10-01

    The neodymium (Nd) isotopic composition (expressed in epsilon units, $\\varepsilon$Nd) of reef framework-forming cold-water corals provides unique measures of water mass provenance and mixing within the Northeast Atlantic today and in the past. A reconstruction of near thermocline water $\\varepsilon$Nd from cold-water corals of the Gulf of Cádiz and Porcupine Seabight spanning over the past 300,000 years, now revealed that climate cooling during Marine Isotope Stages (MIS) 7.2 and MIS 8/9 led to a retraction of the mid-depth Subpolar Gyre (mSPG) to the west. Conversely, Northern Hemisphere warming and increasing fresh water fluxes to the northwest (Labrador Sea) favor a stronger eastward extension of the mSPG blocking the northward flow of temperate Atlantic water as observed during the early MIS 1 and the early stage MIS 5.5. These changes are likely the result of large-scale south-north displacement of the westerlies similar to present-day observations that the North Atlantic Oscillation (NAO) is linked with mid-depth ocean circulation. Based on these observations, we hypothesize that further climate warming will also strengthen the mSPG leading to a salt and temperature decrease in the Northeast Atlantic whereas salinity and temperature will increase in the temperate Atlantic. However, the amplitude of such changes on North Atlantic overturning remains to be tested.

  9. Local and Remote Influences on Vertical Wind Shear over the Northern Tropical Atlantic Region

    NASA Astrophysics Data System (ADS)

    Saravanan, R.; Zhu, X.

    2009-12-01

    Vertical wind shear is one of the most important parameters controlling the frequency and intensity of Atlantic hurricanes. It has been argued that in global warming scenarios, the mechanical effect of changing vertical wind shear may even trump the thermodynamic effect of increasing Atlantic sea surface temperatures, when it comes to projected trends in Atlantic hurricane activity. Despite its importance, little is known about the connection between vertical shear in the north Atlantic region and the global atmospheric circulation, apart from the well-known positive correlation with El Nino-Southern Oscillation (ENSO). In this study, we analyze the statistical relationship between vertical shear and features of the large-scale circulation such as the distribution of sea surface temperature and vertical motion. We examine whether this relationship is different on interannual timescales associated with ENSO as compared to the decadal timescales associated with the Atlantic Multidecadal Oscillation (AMO). We also investigate how well the global general circulation models manage to simulate the observed vertical shear in this region, and its relationship to the large-scale circulation. Our analyses reveal an interesting sensitivity to air-sea coupling in model simulations of vertical shear. Another interesting property of vertical shear, as defined in the context of hurricane studies, is that it is positive definite, rather like precipitation. This means that it has a very nongaussian probability distribution on short timescales. We analyze how this nongaussianity changes when averaged over longer timescales.

  10. Climate variation and regional gradients in population dynamics of two hole-nesting passerines.

    PubMed Central

    Saether, Bernt-Erik; Engen, Steinar; Møller, Anders Pape; Matthysen, Erik; Adriaensen, Frank; Fiedler, Wolfgang; Leivits, Agu; Lambrechts, Marcel M; Visser, Marcel E; Anker-Nilssen, Tycho; Both, Christiaan; Dhondt, André A; McCleery, Robin H; McMeeking, John; Potti, Jamie; Røstad, Ole Wiggo; Thomson, David

    2003-01-01

    Latitudinal gradients in population dynamics can arise through regional variation in the deterministic components of the population dynamics and the stochastic factors. Here, we demonstrate an increase with latitude in the contribution of a large-scale climate pattern, the North Atlantic Oscillation (NAO), to the fluctuations in size of populations of two European hole-nesting passerine species. However, this influence of climate induced different latitudinal gradients in the population dynamics of the two species. In the great tit the proportion of the variability in the population fluctuations explained by the NAO increased with latitude, showing a larger impact of climate on the population fluctuations of this species at higher latitudes. In contrast, no latitudinal gradient was found in the relative contribution of climate to the variability of the pied flycatcher populations because the total environmental stochasticity increased with latitude. This shows that the population ecological consequences of an expected climate change will depend on how climate affects the environmental stochasticity in the population process. In both species, the effects will be larger in those parts of Europe where large changes in climate are expected. PMID:14667357

  11. Regional-Scale Climate Change: Observations and Model Simulations

    SciTech Connect

    Bradley, Raymond S; Diaz, Henry F

    2010-12-14

    This collaborative proposal addressed key issues in understanding the Earth's climate system, as highlighted by the U.S. Climate Science Program. The research focused on documenting past climatic changes and on assessing future climatic changes based on suites of global and regional climate models. Geographically, our emphasis was on the mountainous regions of the world, with a particular focus on the Neotropics of Central America and the Hawaiian Islands. Mountain regions are zones where large variations in ecosystems occur due to the strong climate zonation forced by the topography. These areas are particularly susceptible to changes in critical ecological thresholds, and we conducted studies of changes in phonological indicators based on various climatic thresholds.

  12. Cetacean range and climate in the eastern North Atlantic: future predictions and implications for conservation.

    PubMed

    Lambert, Emily; Pierce, Graham J; Hall, Karen; Brereton, Tom; Dunn, Timothy E; Wall, Dave; Jepson, Paul D; Deaville, Rob; MacLeod, Colin D

    2014-06-01

    There is increasing evidence that the distributions of a large number of species are shifting with global climate change as they track changing surface temperatures that define their thermal niche. Modelling efforts to predict species distributions under future climates have increased with concern about the overall impact of these distribution shifts on species ecology, and especially where barriers to dispersal exist. Here we apply a bio-climatic envelope modelling technique to investigate the impacts of climate change on the geographic range of ten cetacean species in the eastern North Atlantic and to assess how such modelling can be used to inform conservation and management. The modelling process integrates elements of a species' habitat and thermal niche, and employs "hindcasting" of historical distribution changes in order to verify the accuracy of the modelled relationship between temperature and species range. If this ability is not verified, there is a risk that inappropriate or inaccurate models will be used to make future predictions of species distributions. Of the ten species investigated, we found that while the models for nine could successfully explain current spatial distribution, only four had a good ability to predict distribution changes over time in response to changes in water temperature. Applied to future climate scenarios, the four species-specific models with good predictive abilities indicated range expansion in one species and range contraction in three others, including the potential loss of up to 80% of suitable white-beaked dolphin habitat. Model predictions allow identification of affected areas and the likely time-scales over which impacts will occur. Thus, this work provides important information on both our ability to predict how individual species will respond to future climate change and the applicability of predictive distribution models as a tool to help construct viable conservation and management strategies.

  13. Regional model simulation of the North Atlantic cyclone Caroline and comparisons with satellite data

    NASA Astrophysics Data System (ADS)

    Keup-Thiel, E.; Klepp, C.-Ph.; Raschke, E.; Rockel, B.

    2003-03-01

    An individual regional model simulation of cyclone Caroline has been carried out to study water cycle components over the North Atlantic Ocean. The uncertainties associated with quantitative estimates of the water cycle components are highlighted by a comparison of the model results with SSM/I (Special Sensor Microwave Imager) satellite data.

  14. Connecting Regional Modeling Communities Across the Atlantic: The Air Quality Model Evaluation International Initiative (AQMEII)

    EPA Science Inventory

    As any traveler crossing the Atlantic can attest, there certainly are differences between North America and Europe – differences in language, food, culture, and social attitudes, to name but a few. However, the “Old World” and “New World” have a lot in common as well; both region...

  15. INTEGRATION OF COASTAL ENVIRONMENTAL INDICATORS FOR THE U.S. MID-ATLANTIC REGION

    EPA Science Inventory

    The Mid-Atlantic Integrated Assessment (MAlA) Project began in 1994 as a partnership between USEPA's Region III Office and Office of Research and Development. This multi-year initiative was envisioned to: (1) improve the quality of environmental science and promote the use of sou...

  16. SELF-ORGANIZING MAPS FOR INTEGRATED ASSESSMENT OF THE MID-ATLANTIC REGION

    EPA Science Inventory

    A. new method was developed to perform an environmental assessment for the
    Mid-Atlantic Region (MAR). This was a combination of the self-organizing map (SOM) neural network and principal component analysis (PCA). The method is capable of clustering ecosystems in terms of envi...

  17. GLOBAL CHANGE RESEARCH NEWS #2: MID-ATLANTIC REGIONAL ASSESSMENT (MARA)

    EPA Science Inventory

    As part of this National Assessment effort mandated by the Global Change Research Act of 1990, EPA's Global Change Research Program is sponsoring the Mid-Atlantic Regional Assessment (MARA). With EPA sponsorship, a multi-disciplinary team of faculty members is leading the first a...

  18. DEVELOPMENT OF AN INDEX OF BIOTIC INTEGRITY FOR THE MID-ATLANTIC HIGHLANDS REGION

    EPA Science Inventory

    From 1993 to 1996, fish assemblage data were collected from 309 wadeable streams in the U.S. Mid-Atlantic Highlands region as part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. Stream sites were selected with a probabilistic sampl...

  19. A SURVEY OF FISH CONTAMINATION IN SMALL WADEABLE STREAMS IN THE MID-ATLANTIC REGION

    EPA Science Inventory

    In 1993 and 1994, fish tissue samples were collected from first, second and third order streams in the Mid-Atlantic Region of the United States.The tissue samples were prepared from whole fish from prioritized lists of Small Target Species and Large Target Species. The two types ...

  20. Curriculum Digest for the Training of United States Fisheries Observer Corps Atlantic Region. Marine Bulletin 34.

    ERIC Educational Resources Information Center

    Merdinyan, Mark E.; Mortimer, Christine D.

    This digest is intended to be used in conjunction with the text Manual for the Training of United States Fisheries Observers - Atlantic Region. The digest contains five elements; an organization of the training program into sections that allow cumulative learning experience; provides a chronology of these sections to provide optimum coverage and…

  1. Genetic discontinuity among regional populations of Lophelia pertusa in the North Atlantic Ocean

    USGS Publications Warehouse

    Morrison, C.L.; Ross, S.W.; Nizinski, M.S.; Brooke, S.; Jarnegren, J.; Waller, R.G.; Johnson, R.L.; King, T.L.

    2011-01-01

    Knowledge of the degree to which populations are connected through larval dispersal is imperative to effective management, yet little is known about larval dispersal ability or population connectivity in Lophelia pertusa, the dominant framework-forming coral on the continental slope in the North Atlantic Ocean. Using nine microsatellite DNA markers, we assessed the spatial scale and pattern of genetic connectivity across a large portion of the range of L. pertusa in the North Atlantic Ocean. A Bayesian modeling approach found four distinct genetic groupings corresponding to ocean regions: Gulf of Mexico, coastal southeastern U. S., New England Seamounts, and eastern North Atlantic Ocean. An isolation-by-distance pattern was supported across the study area. Estimates of pairwise population differentiation were greatest with the deepest populations, the New England Seamounts (average FST = 0.156). Differentiation was intermediate with the eastern North Atlantic populations (FST = 0.085), and smallest between southeastern U. S. and Gulf of Mexico populations (FST = 0.019), with evidence of admixture off the southeastern Florida peninsula. Connectivity across larger geographic distances within regions suggests that some larvae are broadly dispersed. Heterozygote deficiencies were detected within the majority of localities suggesting deviation from random mating. Gene flow between ocean regions appears restricted, thus, the most effective management scheme for L. pertusa involves regional reserve networks. ?? 2011 US Government.

  2. Genetic discontinuity among regional populations of Lophelia perfusa in the North Atlantic Ocean

    USGS Publications Warehouse

    Morrison, Cheryl L.

    2011-01-01

    Knowledge of the degree to which populations are connected through larval dispersal is imperative to effective management, yet little is known about larval dispersal ability or population connectivity in Lophelia pertusa, the dominant framework-forming coral on the continental slope in the North Atlantic Ocean. Using nine microsatellite DNA markers, we assessed the spatial scale and pattern of genetic connectivity across a large portion of the range of L. pertusa in the North Atlantic Ocean. A Bayesian modeling approach found four distinct genetic groupings corresponding to ocean regions: Gulf of Mexico, coastal southeastern U.S., New England Seamounts, and eastern North Atlantic Ocean. An isolation-by-distance pattern was supported across the study area. Estimates of pairwise population differentiation were greatest with the deepest populations, the New England Seamounts (average FST = 0.156). Differentiation was intermediate with the eastern North Atlantic populations (FST = 0.085), and smallest between southeastern U.S. and Gulf of Mexico populations (FST = 0.019), with evidence of admixture off the southeastern Florida peninsula. Connectivity across larger geographic distances within regions suggests that some larvae are broadly dispersed. Heterozygote deficiencies were detected within the majority of localities suggesting deviation from random mating. Gene flow between ocean regions appears restricted, thus, the most effective management scheme for L. pertusa involves regional reserve networks

  3. A REGIONAL SCALE TOXICITY ASSESSMENT OF SEDIMENT IN THE MID-ATLANTIC AND SOUTHERN ROCKIES, USA

    EPA Science Inventory

    As part of the Environmental Monitoring and Assessment Program (EMAP), sediment samples were collected to assess toxicity on a regional scale in streams and rivers in the Mid-Atlantic U.S. in 1994, 1997 and 1998, and in the Colorado Rocky Mountains in 1994 and 1995. Sample sites...

  4. SEDIMENT MICROBIAL RESPIRATION IN A SYNOPTIC SURVEY OF MID-ATLANTIC REGION STREAMS

    EPA Science Inventory

    l. The rate of microbial respiration on fine-grained stream sediments was measured at 196 first-to third-order sites in the mid-Atlantic region of the United States.2. Sample collection took place between April and July in 1993, 1994 and 1995.3. Study streams were randomly sele...

  5. ESTIMATING STREAMFLOW AND ASSOCIATED HYDRAULIC GEOMETRY, THE MID-ATLANTIC REGION, USA

    EPA Science Inventory

    Methods to estimate streamflow and channel hydraulic geometry were developed for ungaged streams in the Mid-Atlantic Region. Observed mean annual streamflow and associated hydraulic geometry data from 75 gaging stations located in the Appalachian Plateau, the Ridge and Valley, an...

  6. Manual for the Training of United States Fisheries Observer Corps Atlantic Region. Marine Bulletin 33.

    ERIC Educational Resources Information Center

    Merdinyan, Mark E.; Mortimer, Christine D.

    This manual has been produced for use in a four-week training program developed by University of Rhode Island fisheries educators for the training of United States citizens in the duties and responsibilities of observers placed on foreign fishing vessels operating in the Fisheries Conservation Zone in the Atlantic Region. The program combines…

  7. The Impact of the Atlantic Cold Tongue on West African Monsoon Onset in Regional Model Simulations for 1998-2002

    NASA Technical Reports Server (NTRS)

    Druyan, Leonard M.; Fulakeza, Matthew B.

    2014-01-01

    The Atlantic cold tongue (ACT) develops during spring and early summer near the Equator in the Eastern Atlantic Ocean and Gulf of Guinea. The hypothesis that the ACT accelerates the timing of West African monsoon (WAM) onset is tested by comparing two regional climate model (RM3) simulation ensembles. Observed sea surface temperatures (SST) that include the ACT are used to force a control ensemble. An idealized, warm SST perturbation is designed to represent lower boundary forcing without the ACT for the experiment ensemble. Summer simulations forced by observed SST and reanalysis boundary conditions for each of five consecutive years are compared to five parallel runs forced by SST with the warm perturbation. The article summarizes the sequence of events leading to the onset of the WAM in the Sahel region. The representation of WAM onset in RM3 simulations is examined and compared to Tropical Rainfall Measuring Mission (TRMM), Global Precipitation Climatology Project (GPCP) and reanalysis data. The study evaluates the sensitivity of WAM onset indicators to the presence of the ACT by analysing the differences between the two simulation ensembles. Results show that the timing of major rainfall events and therefore theWAM onset in the Sahel are not sensitive to the presence of the ACT. However, the warm SST perturbation does increase downstream rainfall rates over West Africa as a consequence of enhanced specific humidity and enhanced northward moisture flux in the lower troposphere.

  8. Supplementary report on the ground-water supplies of the Atlantic City region

    USGS Publications Warehouse

    Barksdale, Henry C.; Sundstrom, Raymond W.; Brunstein, Maurice S.

    1936-01-01

    At present more potable water is taken from the Atlantic City 800-foot sand than from any other source of supply for the region. This sand is the sole source for some of the smaller communities on the barrier beaches. The original static head of the water in it at Atlantic City was between 20 and 25 feet above sea level. The head has been lowered more than 50 feet over much of the region,  and in parts of Atlantic City it has been lowered considerably more than 100 feet. A consideration of the principles governing the relation between salt water and fresh water in water-bearing sands indicates that the 800-foot sand probably contained salt water at a distance of 5 or 10 miles out from Atlantic City before any water was pumped from it. The evidence collected in this investigation indicates that the cone of depression created by the pumping from this sand in the Atlantic City region has probably extended inland to the intake area of the sand, the nearest part of which is probably about 40 miles from Atlantic City. If this is so, the conclusion is almost inescapable that it has also extended oceanward for a distance considerably greater than the 5 or 10 miles to the original zone of contact between the fresh and salt waters, and that salt water is probably being drawn toward the Atlantic City region through this sand. The time of its arrival will depend primarily upon the rate of pumping in the region and upon how much of the fresh water that originally lay between the region and the zone of contact must be removed before the salt water can reach the region. It may arrive in the near future if it advances in the form of a narrow tongue. On the other hand, if it advances along a broader front; so that more of the intervening fresh water must be pumped out of the formation, its arrival may be delayed for some time.

  9. Does Nudging Squelch the Extremes in Regional Climate Modeling?

    EPA Science Inventory

    An important question in regional climate downscaling is whether to constrain (nudge) the interior of the limited-area domain toward the larger-scale driving fields. Prior research has demonstrated that interior nudging can increase the skill of regional climate predictions origin...

  10. Applying Descriptive Statistics to Teaching the Regional Classification of Climate.

    ERIC Educational Resources Information Center

    Lindquist, Peter S.; Hammel, Daniel J.

    1998-01-01

    Describes an exercise for college and high school students that relates descriptive statistics to the regional climatic classification. The exercise introduces students to simple calculations of central tendency and dispersion, the construction and interpretation of scatterplots, and the definition of climatic regions. Forces students to engage…

  11. Testing the Effects of Increased Horizontal Resolution in a Regional Climate Model for a Climatically Vulnerable Region

    NASA Astrophysics Data System (ADS)

    Snyder, M. A.; Sloan, L. C.; Bell, J. L.

    2002-12-01

    The need for high-resolution simulations of modern and future climates has driven the use of regional climate models in recent years. Regional climate models use a much higher horizontal resolution than global climate models, allowing more detailed investigations of climate at scales of importance to a wider range of parties. Here we explore the effects of increased horizontal resolution on the simulation of climate over the Western U. S. We performed three experiments of modern day climate, using the same boundary conditions, at three different horizontal resolutions, 20 km, 30 km, and 40 km. We compared the experiments with observations of climate and with each other in order to evaluate any improvement or lack of improvement in using the higher resolution. Initial comparisons suggest that a 20 km resolution produces more accurate snow and precipitation results, with temperature results being more similar and accurate between the 20 and 30 km cases.

  12. Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic

    PubMed Central

    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

  13. Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic.

    PubMed

    Vezzulli, Luigi; Grande, Chiara; Reid, Philip C; Hélaouët, Pierre; Edwards, Martin; Höfle, Manfred G; Brettar, Ingrid; Colwell, Rita R; Pruzzo, Carla

    2016-08-23

    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.

  14. Advanced Regional and Decadal Predictions of Coastal Inundation for the U.S. Atlantic and Gulf Coasts

    NASA Astrophysics Data System (ADS)

    Horton, B. P.; Donnelly, J. P.; Corbett, D. R.; Kemp, A.; Lindeman, K.; Mann, M. E.; Peltier, W. R.; Rahmstorf, S.

    2012-12-01

    Future inundation of the US Atlantic and Gulf coasts will depend upon both sea-level rise and the intensity and frequency of tropical cyclones, each of which will be affected by climate change. In this proposal, we will employ new interdisciplinary approaches to bring about a step change in the reliability of predictions of such inundation. The rate of sea-level rise along the US Atlantic and Gulf coasts has increased throughout the 20th century. Whilst there is widespread agreement that it continue to accelerate during the 21st century, great uncertainty surrounds its magnitude and geographic distribution. Key uncertainties include the role of continental ice sheets, mountain glaciers and ocean density changes. Insufficient understanding of these complex physical processes precludes accurate prediction of sea-level rise. New approaches using semi-empirical models that relate instrumental records of climate and sea-level rise have projected up to 2 m of sea-level rise by AD 2100. But the time span of instrumental sea-level records is insufficient to adequately constrain the climate:sea-level relationship. Here, we produce new high resolution proxy data of sea-level and temperature to provide crucial additional constraints to such semi-empirical models. Our dataset will span the alternation between the "Medieval Climate Anomaly" and "Little Ice Age". Before the models can provide appropriate data for coastal management and planning, they must be complemented with regional estimates of sea-level rise. Therefore, the proxy sea-level data has been collected from six study areas (Massachusetts, New Jersey, North Carolina, Georgia and Atlantic and Gulf coasts of Florida) to accommodate the required extent of regional variability. In the case of inundation arising from tropical cyclones, the historical and observational records are insufficient for predicting their nature and recurrence, because they are such extreme and rare events. Moreover, in the future, the resultant

  15. Dynamic, Large-Magnitude CCD Changes in the Atlantic During the Middle Eocene Climatic Optimum

    NASA Astrophysics Data System (ADS)

    Kordesch, W.; Bohaty, S. M.; Palike, H.; Wilson, P. A.; Edgar, K. M.; Agnini, C.; Westerhold, T.; Roehl, U.

    2015-12-01

    The Middle Eocene Climatic Optimum (MECO; ~40.1 Ma) is a transient global warming event that abruptly reversed the long-term Eocene cooling trend. The primary driving mechanism(s) must be linked to a CO2 increase; however, geochemical modeling experiments show that prevailing hypotheses are incompatible with the paleoclimate record. To further examine changes in deep-sea carbonate burial, we identify the MECO for the first time at ODP Site 929 (Equatorial Atlantic; ~3935 m paleodepth) and present new lithological and geochemical data for this site, including benthic foraminiferal stable isotopes (δ18O and δ13C), XRF scanning data, and an orbitally tuned age model. We combine these records with data from a suite of Atlantic sites to form a depth transect between ~2-4 km (DSDP Site 523, ODP Site 1260 and 1263, IODP Site U1404) representing the first detailed record of carbonate dissolution in the Atlantic spanning the MECO. This compilation reveals dissolution at water depths as shallow as ~2 km (>1 km shallower than previous estimates) with multiple and discrete short-lived (<100 kyr) phases of carbonate compensation depth (CCD) shoaling during and after the event. Careful reevaluation of the Pacific CCD records combined with new results suggests similar short-term variability and magnitude of shoaling globally. These data provide new constraints on carbon release history during the MECO and, potentially, the forcing mechanisms for warming. The transient CCD shoaling events indicate multiple pulses of carbon input and acidification decoupled from deep-sea δ18O and δ13C records, indicating that these events must not have been driven directly by changes in temperature or carbon burial/storage - potentially reconciling some of the data-model discrepancies.

  16. North Atlantic Water Mass Formation as Depicted by Coupled Climate Models

    NASA Astrophysics Data System (ADS)

    Ivanova, D.; McClean, J.

    2008-12-01

    We evaluate the realism of North Atlantic (NA) water mass properties in two fully coupled one-degree class Community Climate System Model 3.0 (CCSM3) simulations using Eulerian spectral (CCSM-T85) and finite- volume (CCSM-FV) atmospheric dynamical cores. We calculate the water mass transformation rates (WMTR) for the entire North Atlantic (NA) and separately for the Nordic Seas using 20-year monthly time series of sea surface temperature, sea surface salinity, surface heat and freshwater fluxes due to the atmosphere-ocean and ice-ocean interactions. Compared to the CCSM3-T85 the CCSM3-FV has higher WMTR in narrower density ranges. It's subpolar mode water (σθ= 27.5 kg.m-3) formation rate is 25Sv while in CCSM-T85 it is 20Sv. In the Nordic Seas the CCSM-FV formation rate is about 7.5 Sv versus 6 Sv in CCSM-T85 in the σθ range 27.-28.35 kg.m-3. These results will be validated with observational estimates based on surface fluxes and sea surface temperature from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data and Polar science center Hydrographic Climatology (PHC) sea surface salinity monthly climatology. As expected the dominant formation process is the buoyancy flux caused by the atmosphere-ocean heat exchange. The effect of ice-ocean buoyancy fluxes is to reduce the WMTR mainly due to the freshwater component (freshening during melting). We investigate the interannual variability of the NA WMTR related to the North Atlantic Oscillation (NAO) for both models. The ocean response to the NAO mode is better simulated in the CCSM-FV with intensified water mass production during the negative phase when the winter convection in the Nordic Seas is stronger.

  17. Influences of large- and regional-scale climate on fish recruitment in the Skagerrak-Kattegat over the last century

    NASA Astrophysics Data System (ADS)

    Linderholm, Hans W.; Cardinale, Massimiliano; Bartolino, Valerio; Chen, Deliang; Ou, Tinghai; Svedäng, Henrik

    2014-06-01

    Dynamics of commercial fish stocks are generally associated with fishing pressure and climate variability. Due to short time series, past studies of the relationships between fish stock dynamics and climate have mainly been restricted to the last few decades. Here we analyzed a century-long time series of plaice, cod and haddock from the Skagerrak-Kattegat, to assess the long-term influence of climate on recruitment. Recruitment success (RS) was compared against sea-surface temperature (SST) and atmospheric circulation indices on large (North Atlantic) and regional (Skagerrak-Kattegat) scales. Our results show that the influence of climate on RS was more pronounced on longer, than on shorter timescales. Over the century-long period, a shift from low to high climate sensitivity was seen from the early to the late part for plaice and cod, while the opposite was found for haddock. This shift suggests that the increasing fishing pressure and the climate change in the Skagerrak-Kattegat have resulted in an increased sensitivity of RS to climate for plaice and cod. The diminishing of climate sensitivity in haddock RS, on the other hand, may be linked to the early twentieth century collapse of the stock in the region. While no long-term relationship between RS and the Atlantic Multidecadal Oscillation (AMO) could be found, large RS fluctuations during the positive phase of the AMO (1935-1960), relative to the cold phases, suggests a changed pattern in recruitment during warm periods. On the other hand, this could be due to the increased fishing pressure in the area. Thus, reported correlations between climate and fish may be caused by strong trends in climate in the late-twentieth century, and coincident reduction in fish stocks caused by intense fishing, rather than a stable relationship between climate and fish recruitment per se.

  18. A space-time statistical climate model for hurricane intensification in the North Atlantic basin

    NASA Astrophysics Data System (ADS)

    Fraza, Erik; Elsner, James B.; Jagger, Thomas H.

    2016-08-01

    Climate influences on hurricane intensification are investigated by averaging hourly intensification rates over the period 1975-2014 in 8° × 8° latitude-longitude grid cells. The statistical effects of hurricane intensity and sea-surface temperature (SST), along with the climatic effects of El Niño-Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO) and the Madden-Julian Oscillation (MJO), are quantified using a Bayesian hierarchical model fit to the averaged data. As expected, stronger hurricanes tend to have higher intensification rates, especially over the warmest waters. Of the three climate variables considered, the NAO has the largest effect on intensification rates after controlling for intensity and SST. The model shows an average increase in intensification rates of 0.18 [0.06, 0.31] m s-1 h-1 (95 % credible interval) for every 1 standard deviation decrease in the NAO index. Weak trade winds associated with the negative phase of the NAO might result in less vertical wind shear and thus higher mean intensification rates.

  19. Long-term responses of North Atlantic calcifying plankton to climate change

    NASA Astrophysics Data System (ADS)

    Beaugrand, Gregory; McQuatters-Gollop, Abigail; Edwards, Martin; Goberville, Eric

    2013-03-01

    The global increase in atmospheric carbon dioxide concentration is potentially threatening marine biodiversity in two ways. First, carbon dioxide and other greenhouse gases accumulating in the atmosphere are causing global warming. Second, carbon dioxide is altering sea water chemistry, making the ocean more acidic. Although temperature has a cardinal influence on all biological processes from the molecular to the ecosystem level, acidification might impair the process of calcification or exacerbate dissolution of calcifying organisms. Here, we show however that North Atlantic calcifying plankton primarily responded to climate-induced changes in temperatures during the period 1960-2009, overriding the signal from the effects of ocean acidification. We provide evidence that foraminifers, coccolithophores, both pteropod and non-pteropod molluscs and echinoderms exhibited an abrupt shift circa 1996 at a time of a substantial increase in temperature and that some taxa exhibited a poleward movement in agreement with expected biogeographical changes under sea temperature warming. Although acidification may become a serious threat to marine calcifying organisms, our results suggest that over the study period the primary driver of North Atlantic calcifying plankton was oceanic temperature.

  20. Bias reduction in decadal predictions of West African monsoon rainfall using regional climate models

    NASA Astrophysics Data System (ADS)

    Paxian, A.; Sein, D.; Panitz, H.-J.; Warscher, M.; Breil, M.; Engel, T.; Tödter, J.; Krause, A.; Cabos Narvaez, W. D.; Fink, A. H.; Ahrens, B.; Kunstmann, H.; Jacob, D.; Paeth, H.

    2016-02-01

    The West African monsoon rainfall is essential for regional food production, and decadal predictions are necessary for policy makers and farmers. However, predictions with global climate models reveal precipitation biases. This study addresses the hypotheses that global prediction biases can be reduced by dynamical downscaling with a multimodel ensemble of three regional climate models (RCMs), a RCM coupled to a global ocean model and a RCM applying more realistic soil initialization and boundary conditions, i.e., aerosols, sea surface temperatures (SSTs), vegetation, and land cover. Numerous RCM predictions have been performed with REMO, COSMO-CLM (CCLM), and Weather Research and Forecasting (WRF) in various versions and for different decades. Global predictions reveal typical positive and negative biases over the Guinea Coast and the Sahel, respectively, related to a southward shifted Intertropical Convergence Zone (ITCZ) and a positive tropical Atlantic SST bias. These rainfall biases are reduced by some regional predictions in the Sahel but aggravated by all RCMs over the Guinea Coast, resulting from the inherited SST bias, increased westerlies and evaporation over the tropical Atlantic and shifted African easterly waves. The coupled regional predictions simulate high-resolution atmosphere-ocean interactions strongly improving the SST bias, the ITCZ shift and the Guinea Coast and Central Sahel precipitation biases. Some added values in rainfall bias are found for more realistic SST and land cover boundary conditions over the Guinea Coast and improved vegetation in the Central Sahel. Thus, the ability of RCMs and improved boundary conditions to reduce rainfall biases for climate impact research depends on the considered West African region.

  1. [Climatic suitability of single cropping rice planting region in China].

    PubMed

    Duan, Ju-Qi; Zhou, Guang-Sheng

    2012-02-01

    To clarify the leading climate factors affecting the distribution of single cropping rice planting region in China at national and annual temporal scales and to reveal the potential distribution and climatic suitability divisions of this planting region in China could not only provide scientific basis for optimizing the allocation of single cropping rice production, modifying planting pattern, and introducing fine varieties, but also ensure the food security of China. In this paper, the potential climate factors affecting the single cropping rice distribution in China at regional and annual scales were selected from related literatures, and the single cropping rice geographic information from the national agro-meteorological observation stations of China Meteorological Administration (CMA), together with the maximum entropy model (MaxEnt) and spatial analyst function of Arc-GIS software, were adopted to clarify the leading climate factors affecting the potential distribution of single cropping rice planting region in China, and to construct a model about the relationships between the potential distribution of the planting region and the climate. The results showed that annual precipitation, moisture index, and days of not less than 18 degrees C stably were the leading climate factors affecting the potential distribution of single cropping rice planting region in China, with their cumulative contribution rate reached 94.5% of all candidate climate factors. The model constructed in this paper could well simulate the potential distribution of single cropping rice planting region in China. According to the appearance frequency, the low, medium and high climatic suitability divisions of single cropping rice planting region in China were clarified, and the climate characteristics of the planting region in each climatic suitability division were analyzed.

  2. Predicting the Timing of Cherry Blossoms in Washington, DC and Mid-Atlantic States in Response to Climate Change

    PubMed Central

    Chung, Uran; Mack, Liz; Yun, Jin I.; Kim, Soo-Hyung

    2011-01-01

    Cherry blossoms, an icon of spring, are celebrated in many cultures of the temperate region. For its sensitivity to winter and early spring temperatures, the timing of cherry blossoms is an ideal indicator of the impacts of climate change on tree phenology. Here, we applied a process-based phenology model for temperate deciduous trees to predict peak bloom dates (PBD) of flowering cherry trees (Prunus×yedoensis ‘Yoshino’ and Prunus serrulata ‘Kwanzan’) in the Tidal Basin, Washington, DC and the surrounding Mid-Atlantic States in response to climate change. We parameterized the model with observed PBD data from 1991 to 2010. The calibrated model was tested against independent datasets of the past PBD data from 1951 to 1970 in the Tidal Basin and more recent PBD data from other locations (e.g., Seattle, WA). The model performance against these independent data was satisfactory (Yoshino: r2 = 0.57, RMSE = 6.6 days, bias = 0.9 days and Kwanzan: r2 = 0.76, RMSE = 5.5 days, bias = −2.0 days). We then applied the model to forecast future PBD for the region using downscaled climate projections based on IPCC's A1B and A2 emissions scenarios. Our results indicate that PBD at the Tidal Basin are likely to be accelerated by an average of five days by 2050 s and 10 days by 2080 s for these cultivars under a mid-range (A1B) emissions scenario projected by ECHAM5 general circulation model. The acceleration is likely to be much greater (13 days for 2050 s and 29 days for 2080s ) under a higher (A2) emissions scenario projected by CGCM2 general circulation model. Our results demonstrate the potential impacts of climate change on the timing of cherry blossoms and illustrate the utility of a simple process-based phenology model for developing adaptation strategies to climate change in horticulture, conservation planning, restoration and other related disciplines. PMID:22087317

  3. Efficient Multifamily Homes in a Hot Humid Climate by Atlantic Housing Partners

    SciTech Connect

    Chaser, Dave; Martin, Eric

    2013-04-01

    With assistance from the Florida Solar Energy Center (FSEC) and its Building America Partnership for Improved Residential Construction (BA-PIRC), Atlantic Housing Partners (AHP) has implemented a high performance, systems engineered package of measures. This report demonstrates how the initiative achieves Building America (BA) goals of 30%-50% energy savings. Specifically, the goals are documented as being achieved in the new construction multifamily housing sector in the hot humid climate. Results from energy modeling of the high performance package are presented. The role of utility allowance calculations, used as part of the low-income housing tax credit process, to value those energy savings is discussed, as is customer satisfaction with heat pump water heaters.

  4. Efficient Multifamily Homes in a Hot-Humid Climate by Atlantic Housing Partners

    SciTech Connect

    Chasar, D.; Martin, E.

    2013-04-01

    With assistance from the Florida Solar Energy Center (FSEC) and its Building America Partnership for Improved Residential Construction (BA-PIRC), Atlantic Housing Partners (AHP) has implemented a high performance, systems engineered package of measures. This report demonstrates how the initiative achieves Building America (BA) goals of 30%-50% energy savings. Specifically, the goals are documented as being achieved in the new construction multifamily housing sector in the hot humid climate. Results from energy modeling of the high performance package are presented. The role of utility allowance calculations, used as part of the low-income housing tax credit process, to value those energy savings is discussed, as is customer satisfaction with heat pump water heaters.

  5. Meeting in the MIDDLE:BUILDING off Regional Policies to Promote Climate Education Partnerships on and off Campus

    NASA Astrophysics Data System (ADS)

    Griswold, M.; Stylinski, C.; Shea, N.; Veron, D. E.; Merrill, J.

    2013-12-01

    Both the impacts of climate change and the choices available to adapt and mitigate climate change largely function at the regional scale. Understanding and addressing climate change will require a concerted campaign involving a diverse array of educations from small to large organizations. By focusing on a specific region's climate impacts, adaptation and mitigation options, and existing policies, climate education networks will likely have a higher likelihood of sustainability. Building on this concept, we have developed a climate education partnership, Maryland Delaware Climate Change Education, Assessment and Research (MADE CLEAR), to better understand effective ways to support formal-, informal- and higher-education practitioners in climate change education in this Mid-Atlantic region. We do so largely through face-to-face and web based professional development for each education practitioner group to improve their capacity to incorporate rigorous regionally-based climate science and solutions into their education strategies. We are promoting communities-of-practice within and across these groups as they share their successes and challenges and consider common messages and approaches. Our training and resources focus on impacts and solutions most relevant to our region including sea level rise, extreme events, and urban heat impacts. Our professional development approach aligns directly with existing education and natural resource, including the region's environmental literacy initiatives, the Next Generation Science Standards, and state climate adaptation and mitigation plans. We anticipate that by building off of existing policy, we will build the success of the network into the future. Our project includes design-based research of all three education groups, and thus we will identify effective climate change education strategies, in and out of schools, that are applicable in other regions.

  6. Sensitivity of northwestern North Atlantic shelf circulation to surface and boundary forcing: A regional model assessment

    NASA Astrophysics Data System (ADS)

    Brennan, Catherine E.; Bianucci, Laura; Fennel, Katja

    2014-05-01

    The northwestern North Atlantic shelf circulation, influenced by both North Atlantic subpolar and subtropical gyres, is one of the hydrographically most variable regions in the North Atlantic Ocean and hosts biologically rich and productive fishing grounds. With the goal of simulating conditions in this productive and complex region, we implemented a nested regional ocean model for the northwest North Atlantic shelves including the Gulf of Maine, the Scotian Shelf, the Gulf of St. Lawrence, the Grand Banks, and the adjacent deep ocean. Configuring such a model requires choosing external data to supply surface forcing and initial and boundary conditions, as well as the consideration of nesting options. Although these selections can greatly affect model performance and results, often they are not systematically investigated. Here we assessed the sensitivity of our regional model to a suite of atmospheric forcing datasets, to sets of initial and boundary conditions constructed from multiple global ocean models and a larger scale regional ocean model, and to two variants of the model grid - one extending further off-shelf and resolving Flemish Cap topography. We conducted model simulations for a 6-year period and assessed model performance relative to a regional climatological dataset of temperature and salinity, observations collected from multiple monitoring stations and cruise transect lines, satellite sea surface temperature (SST) data, and descriptions of regional currents from literature. Based on this model assessment, we determined the model configuration that best reproduces observations. We find that while all surface forcing datasets are capable of producing model SST close to observed, the different datasets result in significant differences in model sea surface salinity (SSS). We find that initial and boundary conditions based on global ocean models do not necessary produce realistic circulation, and climatological initial and boundary conditions can

  7. Pathways of fish invasions in the Mid-Atlantic region of the United States

    USGS Publications Warehouse

    Lapointe, Nicolas W. R.; Fuller, Pam; Neilson, Matthew; Murphy, Brian R.; Angermeier, Paul

    2016-01-01

    Non-native fish introductions are a major threat to biodiversity and fisheries, and occur through numerous pathways that vary regionally in importance. A key strategy for managing invasions is to focus prevention efforts on pathways posing the greatest risk of future introductions. We identified high-risk pathways for fish establishment in the Mid-Atlantic region of the United States based on estimates of probability of establishment and records of previous introductions, which were considered in the context of emerging socioeconomic trends. We used estimates of propagule pressure, species’ environmental tolerance, and size of species pool to assess the risk of establishment by pathway. Pathways varied considerably in historic importance and species composition, with the majority of species introduced intentionally via stocking (primarily for sport, forage, or biocontrol) or bait release. Bait release, private stocking, illegal introductions intended to establish reproducing populations (e.g., of sport fish), aquaculture, and the sale of live organisms all create risks for future invasions in the Mid-Atlantic region. Of these pathways, bait release probably poses the greatest risk of introductions for the Mid-Atlantic region because propagule pressure is moderate, most released species are tolerant of local environmental conditions, and the pool of species available for transplantation is large. Our findings differ considerably from studies in other regions (e.g., bait release is a dominant pathway in the Mid-Atlantic region, whereas illegal introduction of sport fish is dominant in the western US and aquarium releases are dominant in Florida), demonstrating the need for regional-scale assessments of, and management strategies for, introduction pathways.

  8. Analysis of the decadal predictability of the North Atlantic volume and heat transport in a future climate projection

    NASA Astrophysics Data System (ADS)

    Fischer, Matthias; Müller, Wolfgang A.; Domeisen, Daniela I. V.; Baehr, Johanna

    2015-04-01

    The North Atlantic ocean is predicted to change considerably with climate change. An analysis of the North Atlantic meridional overturning circulation (AMOC) and the meridional heat transport (OHT) in CMIP5 climate projections in the global coupled Max Planck Institute Earth System Model (MPI-ESM-LR) has shown potential changes in the AMOC's and OHT's seasonal cycle in a future climate. From the CMIP5 historical simulation to RCP4.5, both the AMOC and the OHT indicate latitude dependent temporal shifts of about 1 month until 2050. Based on these results, we here examine potential changes in the decadal predictability of the AMOC and OHT under climate change. In MPI-ESM-LR, we generate two hindcast ensembles with 20 start dates and 10 ensemble members per start date for (i) the current climate state in the CMIP5 historical simulation starting in 1995 and (ii) a future climate state in RCP4.5 starting in 2045. These two hindcast ensembles are compared against the historical simulation and RCP4.5 as control simulation, respectively, using anomaly correlation, root-mean-square error (RMSE) and the Brier skill score decomposition. We investigate whether the decadal predictability of the AMOC and OHT might change under future climate conditions both for the annual mean and individual seasons or climate indices (e.g. for the NAO).

  9. Strengthening Climate Services Capabilities and Regional Engagement at NOAA's National Climatic Data Center

    NASA Astrophysics Data System (ADS)

    Shea, E.

    2008-12-01

    The demand for sector-based climate information is rapidly expanding. In order to support this demand, it is crucial that climate information is managed in an effective, efficient, and user-conscious manner. NOAA's National Climatic Data Center is working closely with numerous partners to develop a comprehensive interface that is authoritative, accessible, and responsive to a variety of sectors, stakeholders, and other users. This talk will explore these dynamics and activities, with additional perspectives on climate services derived from the regional and global experiences of the NOAA Integrated Data and Environmental Applications (IDEA) Center in the Pacific. The author will explore the importance of engaging partners and customers in the development, implementation and emergence of a national climate service program. The presentation will draw on the author's experience in climate science and risk management programs in the Pacific, development of regional and national climate services programs and insights emerging from climate services development efforts in NCDC. In this context, the author will briefly discuss some of guiding principles for effective climate services and applications including: - Early and continuous dialogue, partnership and collaboration with users/customers; - Establishing and sustaining trust and credibility through a program of shared learning and joint problem- solving; - Understanding the societal context for climate risk management and using a problem-focused approach to the development of products and services; - Addressing information needs along a continuum of timescales from extreme events to long-term change; and - Embedding education, outreach and communications activities as critical program elements in effective climate services. By way of examples, the author will reference lessons learned from: early Pacific Island climate forecast applications and climate assessment activities; the implementation of the Pacific Climate

  10. Transient Adjustment of the global climate to an abrupt Northern North Atlantic cooling

    NASA Astrophysics Data System (ADS)

    Tang, G.; Chang, P.; Panetta, R.; Saravanan, R.

    2013-12-01

    The Thermohaline Circulation (THC) is thought to play a key role in abrupt changes in Earth climate. In cold periods such as the Younger Dryas, the THC was much weaker than today. In an experiment with a fully coupled CCSM3 model an artificial freshwater flux is added to the Northern North Atlantic Ocean surface, which weakens the THC. The North Atlantic Ocean surface cools almost instantly after the freshwater flux onset. This cooling is subsequently spread throughout the Northern Hemisphere, resulting in the ITCZ moving southward. In the weakening THC, heat carried by the THC from Southern Hemisphere to the Northern Hemisphere is reduced, resulting in a cooler Northern Hemisphere. It is still questioned what role the atmosphere plays in this process. There are two possible ways the atmosphere may change the ocean surface temperature. One is that the wind changes the ocean surface wind-driven circulation, leading to a change to the ocean heat budget. Another is that the atmosphere changes the ocean-atmosphere heat flux directly. Here we look into the second possibility by comparing the effects of freshwater flux in a fully coupled model to the effects of the same flux in a model constructed by coupling an atmospheric general circulation model (CAM3) to a thermodynamic slab ocean model. With use of appropriate Q-fluxes, the coupled model with the slab ocean has the same climatology as the fully coupled CCSM3 model. Perturbation Q-fluxes are constructed for the fresh water flux experiments using a restoring technique. We find that the atmosphere interacting with a thermodynamic slab ocean can spread the cooling from the Northern North Atlantic and cause the ITCZ to move southward, and that there is a cooling front propagating southward with a speed depending on the mixed layer depth: a deeper mixed layer depth results in a slower propagation. By applying the Q-flux perturbation only in the Northern North Atlantic Ocean, the effect of the ocean circulation change on

  11. North Atlantic Regional Water Resources Study. Main Report

    DTIC Science & Technology

    1972-06-01

    which provide habitats for many types of sweet gale, dogwoods, elder, witch hazel and organisms and interact in a vital way with the alder. This varied...the Region’s longer kinds of native aquatics found in the Region rivers originate in the higher elevations of the are water lilies, arrowheads, sweet ...and pro- forests and cultivated the land, trade with duced grain, potatoes and fruit as well as Europe increased and the port cities grew, livestock

  12. Savannah River Region: Transition between the Gulf and Atlantic Coastal Plains. Proceedings

    SciTech Connect

    Zullo, V.A.; Harris, W.B.; Price, V.

    1990-12-31

    The focus of the this conference of Coastal Plains geologists was on the Savannah River region of Georgia and South Carolina, and particularly on the geology of the US Department of Energy`s 300 square mile Savannah River Site (SRS) in western South Carolina. Current geological studies indicate that the Mesozoic-Cenozoic section in the Savannah River region is transitional between that of the Gulf Coastal Plain to the southwest and that of the Atlantic Coastal Plain to the northeast. With the transitional aspect of the region as its theme, the first session was devoted to overviews of Cretaceous and Paleogene geology in the Gulf and Atlantic Coastal Plains. Succeeding presentations and resulting discussions dealt with more specific problems in structural, lithostratigraphic, hydrological, biostratigraphic, and cyclostratigraphic analysis, and of correlation to standard stratigraphic frameworks. For these conference proceedings, individual papers have been processed separately for the Energy Data Base.

  13. Multi-scale approach to Euro-Atlantic climatic cycles based on phenological time series, air temperatures and circulation indexes.

    PubMed

    Mariani, Luigi; Zavatti, Franco

    2017-03-24

    The spectral periods in North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO) and El Nino Southern Oscillation (ENSO) were analyzed and has been verified how they imprint a time series of European temperature anomalies (ETA), two European temperature time series and some phenological series (dates of cherry flowering and grapevine harvest). Such work had as reference scenario the linear causal chain MCTP (Macroscale Circulation→Temperature→Phenology of crops) that links oceanic and atmospheric circulation to surface air temperature which in its turn determines the earliness of appearance of phenological phases of plants. Results show that in the three segments of the MCTP causal chain are present cycles with the following central period in years (the % of the 12 analyzed time series interested by these cycles are in brackets): 65 (58%), 24 (58%), 20.5 (58%), 13.5 (50%), 11.5 (58%), 7.7 (75%), 5.5 (58%), 4.1 (58%), 3 (50%), 2.4 (67%). A comparison with short term spectral peaks of the four El Niño regions (nino1+2, nino3, nino3.4 and nino4) show that 10 of the 12 series are imprinted by periods around 2.3-2.4yr while 50-58% of the series are imprinted by El Niño periods of 4-4.2, 3.8-3.9, 3-3.1years. The analysis highlights the links among physical and biological variables of the climate system at scales that range from macro to microscale whose knowledge is crucial to reach a suitable understanding of the ecosystem behavior. The spectral analysis was also applied to a time series of spring - summer precipitation in order to evaluate the presence of peaks common with other 12 selected series with result substantially negative which brings us to rule out the existence of a linear causal chain MCPP (Macroscale Circulation→Precipitation→Phenology).

  14. Potential Economic Impacts from Offshore Wind in the Mid-Atlantic Region (Fact Sheet)

    SciTech Connect

    Keyser, D.; Tegen, S.; Flores, F.; Zammit, D.; Kraemer, M.; Miles, J.

    2014-01-01

    Offshore wind is a clean, renewable source of energy and can be an economic driver in the United States. To better understand the employment opportunities and other potential regional economic impacts from offshore wind development, the U.S. Department of Energy (DOE) funded research that focuses on four regions of the country. The studies use multiple scenarios with various local job and domestic manufacturing content assumptions. Each regional study uses the new offshore wind Jobs and Economic Development Impacts (JEDI) model, developed by the National Renewable Energy Laboratory. This fact sheet summarizes the potential economic impacts for the Mid-Atlantic region.

  15. Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar).

    PubMed

    Otero, Jaime; L'Abée-Lund, Jan Henning; Castro-Santos, Ted; Leonardsson, Kjell; Storvik, Geir O; Jonsson, Bror; Dempson, Brian; Russell, Ian C; Jensen, Arne J; Baglinière, Jean-Luc; Dionne, Mélanie; Armstrong, John D; Romakkaniemi, Atso; Letcher, Benjamin H; Kocik, John F; Erkinaro, Jaakko; Poole, Russell; Rogan, Ger; Lundqvist, Hans; Maclean, Julian C; Jokikokko, Erkki; Arnekleiv, Jo Vegar; Kennedy, Richard J; Niemelä, Eero; Caballero, Pablo; Music, Paul A; Antonsson, Thorolfur; Gudjonsson, Sigurdur; Veselov, Alexey E; Lamberg, Anders; Groom, Steve; Taylor, Benjamin H; Taberner, Malcolm; Dillane, Mary; Arnason, Fridthjofur; Horton, Gregg; Hvidsten, Nils A; Jonsson, Ingi R; Jonsson, Nina; McKelvey, Simon; Naesje, Tor F; Skaala, Oystein; Smith, Gordon W; Saegrov, Harald; Stenseth, Nils C; Vøllestad, Leif Asbjørn

    2014-01-01

    Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater ('parr') stage to the migratory stage where they descend streams and enter salt water ('smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the

  16. Norse Greenland settlement: reflections on climate change, trade, and the contrasting fates of human settlements in the North Atlantic Islands.

    PubMed

    Dugmore, Andrew J; Keller, Christian; McGovern, Thomas H

    2007-01-01

    Changing economies and patterns of trade, rather than climatic deterioration, could have critically marginalized the Norse Greenland settlements and effectively sealed their fate. Counter-intuitively, the end of Norse Greenland might not be symptomatic of a failure to adapt to environmental change, but a consequence of successful wider economic developments of Norse communities across North Atlantic. Data from Greenland, the Faroe Islands, and medieval Iceland is used to explore the interplay of Norse society with climate, environment, settlement, and other circumstances. Long term increases in vulnerability caused by economic change and cumulative climate changes sparked a cascading collapse of integrated interdependent settlement systems, bringing the end of Norse Greenland.

  17. Regional Wave Climates along Eastern Boundary Currents

    NASA Astrophysics Data System (ADS)

    Semedo, Alvaro; Soares, Pedro

    2016-04-01

    Two types of wind-generated gravity waves coexist at the ocean surface: wind sea and swell. Wind sea waves are waves under growing process. These young growing waves receive energy from the overlaying wind and are strongly coupled to the local wind field. Waves that propagate away from their generation area and no longer receive energy input from the local wind are called swell. Swell waves can travel long distances across entire ocean basins. A qualitative study of the ocean waves from a locally vs. remotely generation perspective is important, since the air sea interaction processes is strongly modulated by waves and vary accordingly to the prevalence of wind sea or swell waves in the area. A detailed climatology of wind sea and swell waves along eastern boundary currents (EBC; California Current, Canary Current, in the Northern Hemisphere, and Humboldt Current, Benguela Current, and Western Australia Current, in the Southern Hemisphere), based on the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis will be presented. The wind regime along EBC varies significantly from winter to summer. The high summer wind speeds along EBC generate higher locally generated wind sea waves, whereas lower winter wind speeds in these areas, along with stronger winter extratropical storms far away, lead to a predominance of swell waves there. In summer, the coast parallel winds also interact with coastal headlands, increasing the wind speed through a process called "expansion fan", which leads to an increase in the height of locally generated waves downwind of capes and points. Hence the spatial patterns of the wind sea or swell regional wave fields are shown to be different from the open ocean along EBC, due to coastal geometry and fetch dimensions. Swell waves will be shown to be considerably more prevalent and to carry more energy in winter along EBC, while in summer locally generated wind sea waves are either more comparable to swell waves or

  18. Climate warming causes life-history evolution in a model for Atlantic cod (Gadus morhua)

    PubMed Central

    Holt, Rebecca E.; Jørgensen, Christian

    2014-01-01

    Climate change influences the marine environment, with ocean warming being the foremost driving factor governing changes in the physiology and ecology of fish. At the individual level, increasing temperature influences bioenergetics and numerous physiological and life-history processes, which have consequences for the population level and beyond. We provide a state-dependent energy allocation model that predicts temperature-induced adaptations for life histories and behaviour for the North-East Arctic stock (NEA) of Atlantic cod (Gadus morhua) in response to climate warming. The key constraint is temperature-dependent respiratory physiology, and the model includes a number of trade-offs that reflect key physiological and ecological processes. Dynamic programming is used to find an evolutionarily optimal strategy of foraging and energy allocation that maximizes expected lifetime reproductive output given constraints from physiology and ecology. The optimal strategy is then simulated in a population, where survival, foraging behaviour, growth, maturation and reproduction emerge. Using current forcing, the model reproduces patterns of growth, size-at-age, maturation, gonad production and natural mortality for NEA cod. The predicted climate responses are positive for this stock; under a 2°C warming, the model predicted increased growth rates and a larger asymptotic size. Maturation age was unaffected, but gonad weight was predicted to more than double. Predictions for a wider range of temperatures, from 2 to 7°C, show that temperature responses were gradual; fish were predicted to grow faster and increase reproductive investment at higher temperatures. An emergent pattern of higher risk acceptance and increased foraging behaviour was also predicted. Our results provide important insight into the effects of climate warming on NEA cod by revealing the underlying mechanisms and drivers of change. We show how temperature-induced adaptations of behaviour and several life

  19. Investigating the Feedbacks between Land Surface Cover and North Atlantic Climate Variability in the HadCM3 Coupled Climate Model

    NASA Astrophysics Data System (ADS)

    Armstrong, E.; Valdes, P.; House, J.; Singarayer, J. S.

    2015-12-01

    The North Atlantic displays a number of major modes of decadal variability, namely the North Atlantic Oscillation (NAO) and the Atlantic Meridional Overturning Circulation (AMOC). On decadal to multi-decadal timescales, this unforced climate variability is expected to be more influential on the overall pattern of climate than anthropogenic forcing. Greater understanding of this decadal-scale variability is essential to improve its predictability, which in turn is vital to constrain uncertainty in decadal to centennial climate change predictions. Numerous studies have investigated how oceanic and atmospheric forcing modulates climate variability. However the feedbacks between the land surface and decadal variability have not been examined to the same degree. The land surface influences climate via biogeophysical and biogeochemical processes which interact and vary across a wide range of spatial and temporal scales. Increasing concentrations of CO2 are expected to drive a change in the distribution and physiology (i.e. stomatal conductance and leaf area index) of vegetation, which can alter land surface structure and influence biogeophysical processes. It is important to more accurately constrain if/how land surface cover influences decadal variability and the associated feedback mechanisms and how these may change in a warming climate. This sensitivity study will use the HadCM3 climate model to investigate the impact of a range of vegetation distributions on the strength and variability of the AMOC/NAO at increasing CO2 concentrations. We aim to elucidate feedbacks between the land surface, ocean and atmosphere in a coupled climate model and potential implications for decadal modelling studies.

  20. Implication of Agricultural Land Use Change on Regional Climate Projection

    NASA Astrophysics Data System (ADS)

    Wang, G.; Ahmed, K. F.; You, L.

    2015-12-01

    Agricultural land use plays an important role in land-atmosphere interaction. Agricultural activity is one of the most important processes driving human-induced land use land cover change (LULCC) in a region. In addition to future socioeconomic changes, climate-induced changes in crop yield represent another important factor shaping agricultural land use. In feedback, the resulting LULCC influences the direction and magnitude of global, regional and local climate change by altering Earth's radiative equilibrium. Therefore, assessment of climate change impact on future agricultural land use and its feedback is of great importance in climate change study. In this study, to evaluate the feedback of projected land use changes to the regional climate in West Africa, we employed an asynchronous coupling between a regional climate model (RegCM) and a prototype land use projection model (LandPro). The LandPro model, which was developed to project the future change in agricultural land use and the resulting shift in natural vegetation in West Africa, is a spatially explicit model that can account for both climate and socioeconomic changes in projecting future land use changes. In the asynchronously coupled modeling framework, LandPro was run for every five years during the period of 2005-2050 accounting for climate-induced change in crop yield and socioeconomic changes to project the land use pattern by the mid-21st century. Climate data at 0.5˚ was derived from RegCM to drive the crop model DSSAT for each of the five-year periods to simulate crop yields, which was then provided as input data to LandPro. Subsequently, the land use land cover map required to run RegCM was updated every five years using the outputs from the LandPro simulations. Results from the coupled model simulations improve the understanding of climate change impact on future land use and the resulting feedback to regional climate.

  1. Atmospheric Extreme Events in the North Atlantic Region

    NASA Astrophysics Data System (ADS)

    Franzke, C.

    2012-04-01

    An important part of European weather and climate are storms. European winter storms cause economic damage and insurance losses on the order of billions of Euro per year. European winter storms rank as the second highest cause of global natural catastrophe insurance loss. Many of these hazard events are not independent; for instance, severe storms can occur in trains of storms. Recent examples of such subsequently occurring storms include January 2008 (Paula and Resi) and March 2008 (Emma, Johanna and Kirsten). Each of these trains of storms caused damages on the order of ~€1bn. Extreme value statistics are based on the premise that extreme events are iid but this is rarely the case in natural systems where extreme events tend to cluster. Thus, no account is taken of memory and correlation that characterise many natural time series; this fundamentally limits our ability to forecast and to estimate return periods of extreme events. In my presentation I will discuss two possible causes of this clustering: (i) The propensity of extreme events to depend on large-scale circulation regimes and (ii) the long-range correlation properties of surface windspeeds enhances the likelihood of extreme events to cluster. These two characteristics affect the return periods of atmospheric extreme events and thus insurance pricing.

  2. Identifying predictors for regional climate in the Apalachicola-Chattahoochee-Flint (ACF) and Alabama-Coosa-Tallapoosa (ACT) River Basins

    NASA Astrophysics Data System (ADS)

    Maleski, J.; Martinez, C. J.

    2015-12-01

    Statistical climate models of a regional scale are useful for understanding local processes affecting climate and to improving seasonal forecasting. We explore local historical weather station precipitation and temperature measurements from the United States Historical Climatology Network (1895-2012) for 21 stations in the study area. Teleconnections considered as predictors include: Southern Oscillation Index (SOI), Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), Tropical North Atlantic (TNA), Pacific North American pattern (PNA), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Bermuda High Index (BHI). Wilcoxon rank sum testing revealed a strong effect of ENSO on precipitation in the southern part of the study area and a weaker or opposite effect in middle to northern parts of the study area. Warm AMO and warm PDO phases greatly reduced the effect of El Nino rainfall in the study area. Rainfall, temperature and climate indices were examined using nonlinear time series analysis including singular spectrum analysis, convergent cross mapping and granger causality. Aside form seasonality we did not identify strong nonlinear effects. Seasonality was found to be an important factor for selecting lagged predictors in a multivariate time series regression model. Time series clustering was used to reduce the study area to four regions.

  3. A framework for modeling uncertainty in regional climate change

    EPA Science Inventory

    In this study, we present a new modeling framework and a large ensemble of climate projections to investigate the uncertainty in regional climate change over the United States associated with four dimensions of uncertainty. The sources of uncertainty considered in this framework ...

  4. Regional Climate Variations and Change for Terrestrial Ecosystems Workshop Review

    EPA Science Inventory

    North Carolina State University, the University of North Carolina at Chapel Hill, and the U.S. Environmental Protection Agency, in partnership with the U.S. Department of the Interior Southeast Climate Science Center (SECSC), hosted the Regional Climate Variations and Change for ...

  5. Surge in North Atlantic hurricanes due to detectors, not climate change

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2011-07-01

    A spate of research has indicated there may be a link between climate change and the prevalence of North Atlantic tropical cyclones. In a new paper, researchers note upon closer inspection that the prominent upswing in tropical cyclone detections beginning in the midtwentieth century is attributable predominantly to the detection of “shorties” tropical cyclones with durations of less than 2 days. That the apparent surge in cyclone activity could be attributable to changes in the quality and quantity of detections has gained ground as a potential alternative explanation. Using a database of hurricane observations stretching back to 1878, Villarini et al. try to tease out any detectable climate signal from the records. The authors note that between 1878 and 1943 there were 0.58 shorty detections per year, and between 1944 and 2008 there were 2.58 shorty detections per year. This increase in shorties, which the authors propose may be related to the end of World War II and the dawn of air-based reconnaissance and weather tracking, was not mirrored by an increase in tropical cyclone activity for storms longer than 2 days. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2010JD015493, 2011

  6. Building a Regional Collaborative for Climate Literacy

    NASA Astrophysics Data System (ADS)

    Shcherba, O.; Carlton, C.

    2015-12-01

    The San Francisco Bay Area has a strong community of environmental educators with an articulated interest in expanding, elevating, and strengthening climate change programming. Based in this community, a group of educators identified a strong need for and interest in collaborating to increase capacity and knowledge, support pilot testing, and implement climate change best practices in educational and interpretive programs. Since its inception, the Bay Area Climate Literacy Collaborative has brought together over 25 organizations, ranging from wildlife refuges to nonprofit education centers and city park agencies. While still in its nascent phase, the Bay Area Climate Literacy Collaborative exemplifies the power of collective impact. With the backbone support of the Institute at the Golden Gate, the Collaborative has developed a common agenda and is making strides towards developing common measures of success. The initial development stages of this group present an interesting case study and highlight some of the challenges, opportunities, and lessons learned for others seeking to build their own collective impact initiative.

  7. Ensemble-based Regional Climate Prediction: Political Impacts

    NASA Astrophysics Data System (ADS)

    Miguel, E.; Dykema, J.; Satyanath, S.; Anderson, J. G.

    2008-12-01

    Accurate forecasts of regional climate, including temperature and precipitation, have significant implications for human activities, not just economically but socially. Sub Saharan Africa is a region that has displayed an exceptional propensity for devastating civil wars. Recent research in political economy has revealed a strong statistical relationship between year to year fluctuations in precipitation and civil conflict in this region in the 1980s and 1990s. To investigate how climate change may modify the regional risk of civil conflict in the future requires a probabilistic regional forecast that explicitly accounts for the community's uncertainty in the evolution of rainfall under anthropogenic forcing. We approach the regional climate prediction aspect of this question through the application of a recently demonstrated method called generalized scalar prediction (Leroy et al. 2009), which predicts arbitrary scalar quantities of the climate system. This prediction method can predict change in any variable or linear combination of variables of the climate system averaged over a wide range spatial scales, from regional to hemispheric to global. Generalized scalar prediction utilizes an ensemble of model predictions to represent the community's uncertainty range in climate modeling in combination with a timeseries of any type of observational data that exhibits sensitivity to the scalar of interest. It is not necessary to prioritize models in deriving with the final prediction. We present the results of the application of generalized scalar prediction for regional forecasts of temperature and precipitation and Sub Saharan Africa. We utilize the climate predictions along with the established statistical relationship between year-to-year rainfall variability in Sub Saharan Africa to investigate the potential impact of climate change on civil conflict within that region.

  8. The AWI Climate Model: response to increased resolution in dynamically active regions

    NASA Astrophysics Data System (ADS)

    Sidorenko, Dmitry; Semmler, Tido; Rackow, Thomas; Goessling, Helge F.; Danilov, Sergey; Wang, Qiang; Sein, Dmitry; Jung, Thomas

    2016-04-01

    State-of-the-art climate models do still exhibit pronounced deviations from the measured climate. Those deviations are often common between those models. The challenging problems in the Northern hemisphere include warming and salinization of the deep ocean being most pronounced in the northern North Atlantic, reduced deep water formation in the Labrador Sea which is sometimes accomplished by the sporadic ice coverage of the whole Labrador Sea, and an extensive ice presence in the Barents Sea. All these biases are often attributed in literature to the lack of oceanic resolution. The multi-resolution approach used in the ocean component of the AWI climate model (ECHAM6-FESOM) allows to use enhanced horizontal resolution in dynamical active regions while keeping a coarse-resolution setup everywhere else. In this study we develop strategies for improving the climate model biases by means of increasing resolution in the ocean. The current computations have been performed on multi-centennial time scales using refinement in the different parts of the global ocean. Benefits from the local refinement have been analyzed. It is found that already with moderate refinement of the unstructured ocean grid, AWI-CM performs as well as some of the most sophisticated climate models participating in CMIP5.

  9. Response of the North Atlantic dynamic sea level and circulation to Greenland meltwater and climate change in an eddy-permitting ocean model

    NASA Astrophysics Data System (ADS)

    Saenko, Oleg A.; Yang, Duo; Myers, Paul G.

    2016-12-01

    The response of the North Atlantic dynamic sea surface height (SSH) and ocean circulation to Greenland Ice Sheet (GrIS) meltwater fluxes is investigated using a high-resolution model. The model is forced with either present-day-like or projected warmer climate conditions. In general, the impact of meltwater on the North Atlantic SSH and ocean circulation depends on the surface climate. In the two major regions of deep water formation, the Labrador Sea and the Nordic Seas, the basin-mean SSH increases with the increase of the GrIS meltwater flux. This SSH increase correlates with the decline of the Atlantic meridional overturning circulation (AMOC). However, while in the Labrador Sea the warming forcing and GrIS meltwater input lead to sea level rise, in the Nordic Seas these two forcings have an opposite influence on the convective mixing and basin-mean SSH (relative to the global mean). The warming leads to less sea-ice cover in the Nordic Seas, which favours stronger surface heat loss and deep mixing, lowering the SSH and generally increasing the transport of the East Greenland Current. In the Labrador Sea, the increased SSH and weaker deep convection are reflected in the decreased transport of the Labrador Current (LC), which closes the subpolar gyre in the west. Among the two major components of the LC transport, the thermohaline and bottom transports, the former is less sensitive to the GrIS meltwater fluxes under the warmer climate. The SSH difference across the LC, which is a component of the bottom velocity, correlates with the long-term mean AMOC rate.

  10. The stratigraphic record of recent climate change in mid-Atlantic USA

    SciTech Connect

    Brush, G.S.; Hilgartner, W.B.; Khan, H. )

    1994-06-01

    The Medieval Warm Period and Little Ice Age recorded in sediments deposited in tributaries and marshes surrounding the Chesapeake and Delaware Bays in the mid-Atlantic region of USA, by changes in pollen and seeds of terrestrial and aquatic plants, and changes in influxes of charcoal, sediment, metals and nutrients. Fossil pollen and seeds portray a regional landscape characterized by conditions drier that present from about 1000 to 1200 AD. During the same period, high charcoal and sediment influxes indicate high fire frequency. This short dry interval was followed by an expansion of submerged aquatic plants, low marsh plants, and terrestrial plants that occupy wet habitats. Charcoal influxes are extremely low during the latter interval, which extended from about 1200 AD to 1500 AD. Plant macrofossil and pollen distributions indicate a second dry period extending from 1550 to 1650 AD, which appears similar to the earlier Medieval Warm interval.

  11. Regional Climate Model Sensitivity to Domain Size

    NASA Astrophysics Data System (ADS)

    Leduc, M.; Laprise, R.

    2006-05-01

    Regional Climate Models are increasingly used to add small-scale features that are not present in their lateral boundary conditions (LBCs). It is well known that the limited area over which a model integrates must be large enough to allow the full development of small scales features (Jones et al., 1995). On the other hand, integrations on very large domains have shown important departures from the driving data, unless large-scale nudging is applied (e.g., Castro and Pielke, 2005). Here the effects of domain size on the development of small-scales are examined using the "Big-Brother" approach developed by Denis et al. (2002). This method consists of generating a high-resolution simulation over a large domain (the Big-Brother). The next step is to degrade this dataset with a low-pass filter based on discrete cosine transform (DCT; Denis et al., 2002) to emulate coarse-resolution LBCs that are usually taken from GCMs or reanalyses. A second simulation (the Little-Brother) is driven by the coarse-resolution LBCs and generates its own small-scale features inside the new smaller domain. Nested and added scales of the Little- Brother can then be compared with the Big-Brother (unfiltered) ones by using the DCT-filter again. Three February months (1990,1991 and 1992) were integrated over a continental grid (Big-Brother: 196x196 gridpoints) with a spatial resolution of 45 km covering almost the entire North-America. After filtering, this dataset is used to drive five simulations with varying domain size (48x48, 72x72, 96x96, 120x120 and 144x144) centred on the same geographic location; all other parameters are kept constant. Monthly statistics of the five Little-Brothers are compared with the virtual reference (Big-Brother) over the common domain (28x28) corresponding to the smallest Little-Brother but without its sponge zone. Results show that temporal correlation of large-scale events increases when the domain size is reduced from 144x144 to 48x48. For the same domain

  12. The Intensification of Global and Regional Climate Variability and Change

    NASA Astrophysics Data System (ADS)

    Weaver, S. J.

    2015-12-01

    Recent evidence from the IPCC and National Climate Assessment reports indicate that extreme climate events are increasing in many regions of the world. Interestingly, the nature and causes of the changes in extremes may be expressed differently for the global and regional scales, and also amongst climate variables (e.g., precipitation and temperature). For instance, over the last several decades the temperature probability density function on the global scale exhibits a mean shift to the warmer side, as opposed to a change in it's variability. Conversely, the interannual variability of precipitation is intensifying on the regional scale, especially over the U.S. during spring. Although the statistical characteristics of the temperature and precipitation changes may have a varied expression they both contribute to the potential for increases in extreme events. The causes and physical mechanisms for the intensification of mean global temperature and regional precipitation variability are explored using observationally constrained datasets and non-traditional climate model approaches.

  13. What caused the 2009 cold event in the Atlantic cold tongue region?

    NASA Astrophysics Data System (ADS)

    Burmeister, Kristin; Brandt, Peter; Lübbecke, Joke F.

    2016-04-01

    The tropical Atlantic (TA) exhibits sea surface temperature (SST) variability on seasonal to inter-annual time scales. This variability is associated with changes of atmospheric dynamics, linking it to severe flooding or droughts in South America and West Africa. This study investigates processes in the TA that might have caused the extreme cold event in the Atlantic cold tongue (ACT) region in 2009. During boreal spring, a strong negative Atlantic meridional mode event developed in the TA associated with northwesterly wind anomalies along the equator. Contrary to what would be expected from ENSO-like dynamics, these wind anomalies did not lead to a warming in the eastern equatorial Atlantic in boreal summer. Instead, from May to August 2009, an abrupt cooling took place in the ACT region resulting in the coldest August ACT SST on record. In the literature, two processes - equatorial wave reflection and meridional advection of subsurface temperatures - are discussed as potential causes of such an event. Whereas previous studies are mainly based on satellite data, reanalysis products and model output, we here use in situ measurements (data from Argo floats, PIRATA buoys, and TACE moorings, as well as CTD data of various ship cruises) in addition to satellite and reanalysis products to investigate the contribution of both processes to the strong surface cooling in the ACT region in 2009. Results based on the Argo float data confirm previous findings that equatorial wave reflection contributed to the cold event in the ACT region in 2009. They further indicate that higher baroclinic mode waves played an important role. The analysis of in situ and reanalysis temperature and velocity data does not suggest a significant contribution of meridional advection of subsurface temperatures for the onset of the 2009 cold event. The results indicate an asymmetry in the importance of meridional advection for non-ENSO-like cold and warm events with warm events more strongly affected

  14. SPURS: Salinity Processes in the Upper-Ocean Regional Study: THE NORTH ATLANTIC EXPERIMENT

    NASA Technical Reports Server (NTRS)

    Lindstrom, Eric; Bryan, Frank; Schmitt, Ray

    2015-01-01

    In this special issue of Oceanography, we explore the results of SPURS-1, the first part of the ocean process study Salinity Processes in the Upper-ocean Regional Study (SPURS). The experiment was conducted between August 2012 and October 2013 in the subtropical North Atlantic and was the first of two experiments (SPURS come in pairs!). SPURS-2 is planned for 20162017 in the tropical eastern Pacific Ocean.

  15. THE RESPONSE OF MARINE ECOSYSTEMS TO CLIMATE VARIABILITY ASSOCIATED WITH THE NORTH ATLANTIC OSCILLATION

    EPA Science Inventory

    A strong association is documented between variability of the North Atlantic Oscillation (NAO) and changes in various trophic levels of the marine ecosystems of the North Atlantic. Examples are presented for phytoplankton, zooplankton, benthos, fish, marine diseases, whales and s...

  16. Inter-annual Tropospheric Aerosol Variability in Late Twentieth Century and its Impact on Tropical Atlantic and West African Climate by Direct and Semi-direct Effects

    SciTech Connect

    Evans, Katherine J; Hack, James J; Truesdale, John; Mahajan, Salil; Lamarque, J-F

    2012-01-01

    A new high-resolution (0.9$^{\\circ}$x1.25$^{\\circ}$ in the horizontal) global tropospheric aerosol dataset with monthly resolution is generated using the finite-volume configuration of Community Atmosphere Model (CAM4) coupled to a bulk aerosol model and forced with recent estimates of surface emissions for the latter part of twentieth century. The surface emissions dataset is constructed from Coupled Model Inter-comparison Project (CMIP5) decadal-resolution surface emissions dataset to include REanalysis of TROpospheric chemical composition (RETRO) wildfire monthly emissions dataset. Experiments forced with the new tropospheric aerosol dataset and conducted using the spectral configuration of CAM4 with a T85 truncation (1.4$^{\\circ}$x1.4$^{\\circ}$) with prescribed twentieth century observed sea surface temperature, sea-ice and greenhouse gases reveal that variations in tropospheric aerosol levels can induce significant regional climate variability on the inter-annual timescales. Regression analyses over tropical Atlantic and Africa reveal that increasing dust aerosols can cool the North African landmass and shift convection southwards from West Africa into the Gulf of Guinea in the spring season in the simulations. Further, we find that increasing carbonaceous aerosols emanating from the southwestern African savannas can cool the region significantly and increase the marine stratocumulus cloud cover over the southeast tropical Atlantic ocean by aerosol-induced diabatic heating of the free troposphere above the low clouds. Experiments conducted with CAM4 coupled to a slab ocean model suggest that present day aerosols can shift the ITCZ southwards over the tropical Atlantic and can reduce the ocean mixed layer temperature beneath the increased marine stratocumulus clouds in the southeastern tropical Atlantic.

  17. Late Eocene to middle Miocene (33 to 13 million years ago) vegetation and climate development on the North American Atlantic Coastal Plain (IODP Expedition 313, Site M0027)

    NASA Astrophysics Data System (ADS)

    Kotthoff, U.; Greenwood, D. R.; McCarthy, F. M. G.; Müller-Navarra, K.; Prader, S.; Hesselbo, S. P.

    2014-08-01

    C higher than today, but ∼1.5 °C lower than preceding and following phases of the Miocene. We conclude that vegetation and regional climate in the hinterland of the New Jersey shelf did not react as sensitively to Oligocene and Miocene climate changes as other regions in North America or Europe due to the moderating effects of the North Atlantic. An additional explanation for the relatively low regional temperatures reconstructed for the mid-Miocene climatic optimum could be an uplift of the Appalachian Mountains during the Miocene, which would also have influenced the catchment area of our pollen record.

  18. Current climate and climate change over India as simulated by the Canadian Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Alexandru, Adelina; Sushama, Laxmi

    2014-09-01

    The performance of the fifth generation of the Canadian Regional Climate Model (CRCM5) in reproducing the main climatic characteristics over India during the southwest (SW)-, post- and pre-monsoon seasons are presented in this article. To assess the performance of CRCM5, European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and Interim re-analysis (ERA-Interim) driven CRCM5 simulation is compared against independent observations and reanalysis data for the 1971-2000 period. Projected changes for two future periods, 2041-2070 and 2071-2100, with respect to the 1971-2000 current period are assessed based on two transient climate change simulations of CRCM5 spanning the 1950-2100 period. These two simulations are driven by the Canadian Earth System Model version 2 (CanESM2) and the Max Planck Institute for Meteorology's Earth System Low Resolution Model (MPI-ESM-LR), respectively. The boundary forcing errors associated with errors in the driving global climate models are also studied by comparing the 1971-2000 period of the CanESM2 and MPI-ESM-LR driven simulations with that of the CRCM5 simulation driven by ERA-40/ERA-Interim. Results show that CRCM5 driven by ERA-40/ERA-Interim is in general able to capture well the temporal and spatial patterns of 2 m-temperature, precipitation, wind, sea level pressure, total runoff and soil moisture over India in comparison with available reanalysis and observations. However, some noticeable differences between the model and observational data were found during the SW-monsoon season within the domain of integration. CRCM5 driven by ERA-40/ERA-Interim is 1-2 °C colder than CRU observations and generates more precipitation over the Western Ghats and central regions of India, and not enough in the northern and north-eastern parts of India and along the Konkan west coast in comparison with the observed precipitation. The monsoon onset seems to be relatively well captured over the southwestern coast of India

  19. Current climate and climate change over India as simulated by the Canadian Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Alexandru, Adelina; Sushama, Laxmi

    2015-08-01

    The performance of the fifth generation of the Canadian Regional Climate Model (CRCM5) in reproducing the main climatic characteristics over India during the southwest (SW)-, post- and pre-monsoon seasons are presented in this article. To assess the performance of CRCM5, European Centre for Medium- Range Weather Forecasts (ECMWF) Re- Analysis (ERA- 40) and Interim re-analysis (ERA-Interim) driven CRCM5 simulation is compared against independent observations and reanalysis data for the 1971-2000 period. Projected changes for two future periods, 2041-2070 and 2071-2100, with respect to the 1971-2000 current period are assessed based on two transient climate change simulations of CRCM5 spanning the 1950-2100 period. These two simulations are driven by the Canadian Earth System Model version 2 (CanESM2) and the Max Planck Institute for Meteorology's Earth System Low Resolution Model (MPI-ESM-LR), respectively. The boundary forcing errors associated with errors in the driving global climate models are also studied by comparing the 1971-2000 period of the CanESM2 and MPI-ESM-LR driven simulations with that of the CRCM5 simulation driven by ERA-40/ERA-Interim. Results show that CRCM5 driven by ERA-40/ERA-Interim is in general able to capture well the temporal and spatial patterns of 2 m-temperature, precipitation, wind, sea level pressure, total runoff and soil moisture over India in comparison with available reanalysis and observations. However, some noticeable differences between the model and observational data were found during the SW-monsoon season within the domain of integration. CRCM5 driven by ERA-40/ERA-Interim is 1-2 °C colder than CRU observations and generates more precipitation over the Western Ghats and central regions of India, and not enough in the northern and north-eastern parts of India and along the Konkan west coast in comparison with the observed precipitation. The monsoon onset seems to be relatively well captured over the southwestern coast of

  20. The North American Regional Climate Change Assessment Program: Overview of Climate Change Results

    NASA Astrophysics Data System (ADS)

    Mearns, L. O.

    2011-12-01

    The North American Regional Climate Change Assessment Program (NARCCAP) is an international program that is serving the climate scenario needs of the United States, Canada, and northern Mexico. We are systematically investigating the uncertainties in regional scale projections of future climate and producing high resolution climate change scenarios using multiple regional climate models (RCMs) and multiple global model responses by nesting the RCMs within atmosphere ocean general circulation models (AOGCMs) forced with a medium-high emissions scenario, over a domain covering the conterminous US, northern Mexico, and most of Canada. The project also includes a validation component through nesting the participating RCMs within the NCEP reanalysis R2. The basic spatial resolution of the RCM simulations is 50 km. This program includes six different RCMs that have been used in various intercomparison programs in Europe and the United States. Four different AOGCMs provide boundary conditions to drive the RCMS for 30 years in the current climate and 30 years for the mid 21st century. The resulting climate model simulations form the basis for multiple high resolution climate scenarios that can be used in climate change impacts and adaptation assessments over North America. Eleven of the planned 12 sets of current and future simulations have been completed. Measures of uncertainty across the multiple simulations are being developed by geophysical statisticians. In this overview talk, results from the climate change experiments for various subregions, along with measures of uncertainty, will be presented.

  1. The North American Regional Climate Change Assessment Program: Overview of Climate Change Results

    NASA Astrophysics Data System (ADS)

    Mearns, L. O.

    2012-12-01

    The North American Regional Climate Change Assessment Program (NARCCAP) is an international program that is serving the climate scenario needs of the United States, Canada, and northern Mexico. We are systematically investigating the uncertainties in regional scale projections of future climate and producing high resolution climate change scenarios using multiple regional climate models (RCMs) and multiple global model responses by nesting the RCMs within atmosphere ocean general circulation models (AOGCMs) forced with a medium-high emissions scenario, over a domain covering the conterminous US, northern Mexico, and most of Canada. The project also includes a validation component through nesting the participating RCMs within the NCEP reanalysis R2. The basic spatial resolution of the RCM simulations is 50 km. This program includes six different RCMs that have been used in various intercomparison programs in Europe and the United States. Four different AOGCMs provide boundary conditions to drive the RCMS for 30 years in the current climate and 30 years for the mid 21st century. The resulting climate model simulations form the basis for multiple high resolution climate scenarios that can be used in climate change impacts and adaptation assessments over North America. All 12 sets of current and future simulations have been completed. Measures of uncertainty across the multiple simulations are being developed by geophysical statisticians. In this overview talk, results from the various climate change experiments for various subregions, along with measures of uncertainty, will be presented

  2. Regional Scale Analyses of Climate Change Impacts on Agriculture

    NASA Astrophysics Data System (ADS)

    Wolfe, D. W.; Hayhoe, K.

    2006-12-01

    New statistically downscaled climate modeling techniques provide an opportunity for improved regional analysis of climate change impacts on agriculture. Climate modeling outputs can often simultaneously meet the needs of those studying impacts on natural as well as managed ecosystems. Climate outputs can be used to drive existing forest or crop models, or livestock models (e.g., temperature-humidity index model predicting dairy milk production) for improved information on regional impact. High spatial resolution climate forecasts, combined with knowledge of seasonal temperatures or rainfall constraining species ranges, can be used to predict shifts in suitable habitat for invasive weeds, insects, and pathogens, as well as cash crops. Examples of climate thresholds affecting species range and species composition include: minimum winter temperature, duration of winter chilling (vernalization) hours (e.g., hours below 7.2 C), frost-free period, and frequency of high temperature stress days in summer. High resolution climate outputs can also be used to drive existing integrated pest management models predicting crop insect and disease pressure. Collectively, these analyses can be used to test hypotheses or provide insight into the impact of future climate change scenarios on species range shifts and threat from invasives, shifts in crop production zones, and timing and regional variation in economic impacts.

  3. DEVELOPMENT AND EVALUATION OF A MACROINVERTEBRATE BIOTIC INTEGRITY INDEX (MBII) FOR REGIONALLY ASSESSING MID-ATLANTIC HIGHLANDS STREAMS

    EPA Science Inventory

    The multimetric Macroinvertebrate Biotic Integrity Index (MBII) was developed from data collected at 574 wadeable stream reaches in the Mid-Atlantic Highlands region (MAHR) by the USEPA's Environmental Monitoring and Assessment Program (EMAP). Over 100 candidate metrics were eval...

  4. An objective tropical Atlantic sea surface temperature gradient index for studies of south Amazon dry-season climate variability and change.

    PubMed

    Good, Peter; Lowe, Jason A; Collins, Mat; Moufouma-Okia, Wilfran

    2008-05-27

    Future changes in meridional sea surface temperature (SST) gradients in the tropical Atlantic could influence Amazon dry-season precipitation by shifting the patterns of moisture convergence and vertical motion. Unlike for the El Niño-Southern Oscillation, there are no standard indices for quantifying this gradient. Here we describe a method for identifying the SST gradient that is most closely associated with June-August precipitation over the south Amazon. We use an ensemble of atmospheric general circulation model (AGCM) integrations forced by observed SST from 1949 to 2005. A large number of tropical Atlantic SST gradient indices are generated randomly and temporal correlations are examined between these indices and June-August precipitation averaged over the Amazon Basin south of the equator. The indices correlating most strongly with June-August southern Amazon precipitation form a cluster of near-meridional orientation centred near the equator. The location of the southern component of the gradient is particularly well defined in a region off the Brazilian tropical coast, consistent with known physical mechanisms. The chosen index appears to capture much of the Atlantic SST influence on simulated southern Amazon dry-season precipitation, and is significantly correlated with observed southern Amazon precipitation. We examine the index in 36 different coupled atmosphere-ocean model projections of climate change under a simple compound 1% increase in CO2. Within the large spread of responses, we find a relationship between the projected trend in the index and the Amazon dry-season precipitation trends. Furthermore, the magnitude of the trend relationship is consistent with the inter-annual variability relationship found in the AGCM simulations. This suggests that the index would be of use in quantifying uncertainties in climate change in the region.

  5. Astronomical tuning for the upper Messinian Spanish Atlantic margin: Disentangling basin evolution, climate cyclicity and MOW

    NASA Astrophysics Data System (ADS)

    van den Berg, B. C. J.; Sierro, F. J.; Hilgen, F. J.; Flecker, R.; Larrasoaña, J. C.; Krijgsman, W.; Flores, J. A.; Mata, M. P.; Bellido Martín, E.; Civis, J.; González-Delgado, J. A.

    2015-12-01

    We present a new high-resolution cyclostratigraphic age model for the Messinian sediments of the Montemayor-1 core. This core was drilled in the Guadalquivir Basin in southern Spain, which formed part of the marine corridor linking the Mediterranean with the Atlantic in the Late Miocene. Tuning of high-resolution geochemical records reveals a strong precessional cyclicity, with maximum clastic supply from river run off coinciding with maximum summer insolation. We recognize a gradual change in the nature of the typical cyclic fluctuations in elemental compositions of the sediments through the core, which is associated with a gradual change in depositional environment as the basin infilled. After applying the new age model, the upper Messinian glacial stages and deglaciation are clearly identified in the oxygen isotope records of the Montemayor-1 core. Reinterpretation of existing planktonic and benthic oxygen isotope records for the core and comparison with equivalent successions in the Rifian Corridor in northern Morocco allow the re-evaluation of the influence of the different water masses in the region: North Atlantic Central Water and Mediterranean Outflow Water. We observe no direct influence of MOW immediately before or during the Messinian Salinity Crisis.

  6. Initialized near-term regional climate change prediction

    PubMed Central

    Doblas-Reyes, F. J.; Andreu-Burillo, I.; Chikamoto, Y.; García-Serrano, J.; Guemas, V.; Kimoto, M.; Mochizuki, T.; Rodrigues, L. R. L.; van Oldenborgh, G. J.

    2013-01-01

    Climate models are seen by many to be unverifiable. However, near-term climate predictions up to 10 years into the future carried out recently with these models can be rigorously verified against observations. Near-term climate prediction is a new information tool for the climate adaptation and service communities, which often make decisions on near-term time scales, and for which the most basic information is unfortunately very scarce. The Fifth Coupled Model Intercomparison Project set of co-ordinated climate-model experiments includes a set of near-term predictions in which several modelling groups participated and whose forecast quality we illustrate here. We show that climate forecast systems have skill in predicting the Earth's temperature at regional scales over the past 50 years and illustrate the trustworthiness of their predictions. Most of the skill can be attributed to changes in atmospheric composition, but also partly to the initialization of the predictions. PMID:23591882

  7. Initialized near-term regional climate change prediction.

    PubMed

    Doblas-Reyes, F J; Andreu-Burillo, I; Chikamoto, Y; García-Serrano, J; Guemas, V; Kimoto, M; Mochizuki, T; Rodrigues, L R L; van Oldenborgh, G J

    2013-01-01

    Climate models are seen by many to be unverifiable. However, near-term climate predictions up to 10 years into the future carried out recently with these models can be rigorously verified against observations. Near-term climate prediction is a new information tool for the climate adaptation and service communities, which often make decisions on near-term time scales, and for which the most basic information is unfortunately very scarce. The Fifth Coupled Model Intercomparison Project set of co-ordinated climate-model experiments includes a set of near-term predictions in which several modelling groups participated and whose forecast quality we illustrate here. We show that climate forecast systems have skill in predicting the Earth's temperature at regional scales over the past 50 years and illustrate the trustworthiness of their predictions. Most of the skill can be attributed to changes in atmospheric composition, but also partly to the initialization of the predictions.

  8. Satellite-Derived Water Vapor Winds for Regional Climate Studies

    NASA Technical Reports Server (NTRS)

    Jedlovce, Gary J.; Lerner, Jeffery A.; Iwai, Hisaki; Haines, Stephanie

    1999-01-01

    The retrieval of winds and humidity in the upper-troposphere has matured to the point where it may now be possible to better understand and diagnose regional climate variations from geostationary satellites than from conventional measurements or model analysis, especially in data sparse regions. In this poster paper, upper-tropospheric circulation features and moisture transport covering ENSO periods are presented and discussed. Precursor and other detectable interannual climate signals are analyzed and compared to model diagnosed features. Estimates of winds and humidity over data-rich regions (from conventional measurements) are used to show the robustness of the data and its value over regions which are currently poorly sampled.

  9. Evaluation of regional climate simulations for air quality modelling purposes

    NASA Astrophysics Data System (ADS)

    Menut, Laurent; Tripathi, Om P.; Colette, Augustin; Vautard, Robert; Flaounas, Emmanouil; Bessagnet, Bertrand

    2013-05-01

    In order to evaluate the future potential benefits of emission regulation on regional air quality, while taking into account the effects of climate change, off-line air quality projection simulations are driven using weather forcing taken from regional climate models. These regional models are themselves driven by simulations carried out using global climate models (GCM) and economical scenarios. Uncertainties and biases in climate models introduce an additional "climate modeling" source of uncertainty that is to be added to all other types of uncertainties in air quality modeling for policy evaluation. In this article we evaluate the changes in air quality-related weather variables induced by replacing reanalyses-forced by GCM-forced regional climate simulations. As an example we use GCM simulations carried out in the framework of the ERA-interim programme and of the CMIP5 project using the Institut Pierre-Simon Laplace climate model (IPSLcm), driving regional simulations performed in the framework of the EURO-CORDEX programme. In summer, we found compensating deficiencies acting on photochemistry: an overestimation by GCM-driven weather due to a positive bias in short-wave radiation, a negative bias in wind speed, too many stagnant episodes, and a negative temperature bias. In winter, air quality is mostly driven by dispersion, and we could not identify significant differences in either wind or planetary boundary layer height statistics between GCM-driven and reanalyses-driven regional simulations. However, precipitation appears largely overestimated in GCM-driven simulations, which could significantly affect the simulation of aerosol concentrations. The identification of these biases will help interpreting results of future air quality simulations using these data. Despite these, we conclude that the identified differences should not lead to major difficulties in using GCM-driven regional climate simulations for air quality projections.

  10. Modeling dust emission response to North Atlantic millennial-scale climate variations from the perspective of East European MIS 3 loess deposits

    NASA Astrophysics Data System (ADS)

    Sima, A.; Kageyama, M.; Rousseau, D.-D.; Ramstein, G.; Balkanski, Y.; Antoine, P.; Hatté, C.

    2013-07-01

    European loess sequences of the Marine Isotope Stage 3 (~60-25 kyr BP) show periods of strong dust accumulation alternating with episodes of reduced sedimentation, favoring soil development. In the western part of the loess belt centered around 50° N, these variations appear to have been related to the North Atlantic rapid climate changes: the Dansgaard-Oeschger (DO) and Heinrich (H) events. It has been recently suggested that the North Atlantic climate signal can be detected further east, in loess deposits from Stayky (50°05.65' N, 30°53.92' E), Ukraine. Here we use climate and dust emission modeling to investigate this data interpretation. We focus on the areas north and northeast of the Carpathians, where loess deposits can be found, and the corresponding main dust sources must have been located as well. The simulations were performed with the LMDZ atmospheric general circulation model and the ORCHIDEE land surface model. They represent a reference "Greenland stadial" state and two perturbations, seen as sensitivity tests with respect to changes in the North Atlantic surface conditions between 30° and 63° N: a "Greenland interstadial" and an "H event". The main source for the loess deposits in the studied area is identified as a dust deflation band, with two very active spots located west-northwest from our reference site. Emissions only occur between February and June. Differences from one deflation spot to another, and from one climate state to another, are explained by analyzing the relevant meteorological and surface variables. Over most of the source region, the annual emission fluxes in the "interstadial" experiment are 30 to 50% lower than the "stadial" values; they would only be about 20% lower if the inhibition of dust uplift by the vegetation were not taken into account. Assuming that lower emissions result in reduced dust deposition leads us to the conclusion that the loess-paleosol stratigraphic succession in the Stayky area reflects indeed

  11. Breakup of Pangaea and plate kinematics of the central Atlantic and Atlas regions

    NASA Astrophysics Data System (ADS)

    Schettino, Antonio; Turco, Eugenio

    2009-08-01

    and the conjugate margin of Nova Scotia. The inversion of the Atlas rift and the subsequent formation of the Atlas mountain belt occurred during the Oligocene-early Miocene time interval. In the central Atlantic, this event was associated with higher spreading rates of the ridge segments north of the Atlantis FZ. An estimate of 170 km of dextral offset of Morocco relative to northwest Africa, in the central Atlantic, is required by an analysis of marine magnetic anomalies. Five plate tectonic reconstructions and a computer animation are proposed to illustrate the late Triassic and Jurassic process of breakup of Pangaea in the central Atlantic and Atlas regions.

  12. Climatic variability of river outflow in the Pantanal region and the influence of sea surface temperature

    NASA Astrophysics Data System (ADS)

    Silva, Carlos Batista; Silva, Maria Elisa Siqueira; Ambrizzi, Tércio

    2016-03-01

    This paper investigates possible linear relationships between climate, hydrology, and oceanic surface variability in the Pantanal region (in South America's central area), over interannual and interdecadal time ranges. In order to verify the mentioned relations, lagged correlation analysis and linear adjustment between river discharge at the Pantanal region and sea surface temperature were used. Composite analysis for atmospheric fields, air humidity flux divergence, and atmospheric circulation at low and high levels, for the period between 1970 and 2003, was analyzed. Results suggest that the river discharge in the Pantanal region is linearly associated with interdecadal and interannual oscillations in the Pacific and Atlantic oceans, making them good predictors to continental hydrological variables. Considering oceanic areas, 51 % of the annual discharge in the Pantanal region can be linearly explained by mean sea surface temperature (SST) in the Subtropical North Pacific, Tropical North Pacific, Extratropical South Pacific, and Extratropical North Atlantic over the period. Considering a forecast approach in seasonal scale, 66 % of the monthly discharge variance in Pantanal, 3 months ahead of SST, is explained by the oceanic variables, providing accuracy around 65 %. Annual discharge values in the Pantanal region are strongly related to the Pacific Decadal Oscillation (PDO) variability (with 52 % of linear correlation), making it possible to consider an interdecadal variability and a consequent subdivision of the whole period in three parts: 1st (1970-1977), 2nd (1978-1996), and 3rd (1997-2003) subperiods. The three subperiods coincide with distinct PDO phases: negative, positive, and negative, respectively. Convergence of humidity flux at low levels and the circulation pattern at high levels help to explain the drier and wetter subperiods. During the wetter 2nd subperiod, the air humidity convergence at low levels is much more evident than during the other two

  13. Potential for shoreline changes due to sea-level rise along the U.S. mid-Atlantic region

    USGS Publications Warehouse

    Gutierrez, Benjamin T.; Williams, S. Jeffress; Thieler, E. Robert

    2007-01-01

    Sea-level rise over the next century is expected to contribute significantly to physical changes along open-ocean shorelines. Predicting the form and magnitude of coastal changes is important for understanding the impacts to humans and the environment. Presently, the ability to predict coastal changes is limited by the scientific understanding of the many variables and processes involved in coastal change, and the lack of consensus regarding the validity of existing conceptual, analytical, or numerical models. In order to assess potential future coastal changes in the mid-Atlantic U.S. for the U.S. Climate Change Science Program (CCSP), a workshop was convened by the U.S. Geological Survey. Assessments of future coastal change were made by a committee of coastal scientists with extensive professional experience in the mid-Atlantic region. Thirteen scientists convened for a two-day meeting to exchange information and develop a consensus opinion on potential future coastal changes for the mid-Atlantic coast in response to sea-level rise. Using criteria defined in past work, the mid-Atlantic coast was divided into four geomorphic compartments: spits, headlands, wave-dominated barriers, and mixed-energy barriers. A range of potential coastal responses was identified for each compartment based on four sea-level rise scenarios. The four scenarios were based on the assumptions that: a) the long-term sea-level rise rate observed over the 20th century would persist over the 21st century, b) the 20th century rate would increase by 2 mm/yr, c) the 20th century rate would increase by 7 mm/yr, or d) sea-level would rise by 2 m over the next few hundred years. Potential responses to these sea-level rise scenarios depend on the landforms that occur within a region and include increased likelihood for erosion and shoreline retreat for all coastal types, increased likelihood for erosion, overwash and inlet breaching for barrier islands, as well as the possibility of a threshold

  14. Climate change impacts on water availability: developing regional scenarios for agriculture of the Former Soviet Union countries of Central Asia

    NASA Astrophysics Data System (ADS)

    Kirilenko, A.; Dronin, N.

    2010-12-01

    Water is the major factor, limiting agriculture of the five Former Soviet Union (FSU) of Central Asia. Elevated topography prevents moist and warm air from the Atlantic and Indian Oceans from entering the region.With exception of Kazakhstan, agriculture is generally restricted to oases and irrigated lands along the major rivers and canals. Availability of water for irrigation is the major factor constraining agriculture in the region, and conflicts over water are not infrequent. The current water crisis in the region is largely due to human activity; however the region is also strongly impacted by the climate. In multiple locations, planned and autonomous adaptations to climate change have already resulted in changes in agriculture, such as a dramatic increase in irrigation, or shift in crops towards the ones better suited for warmer and dryer climate; however, it is hard to differentiate between the effects of overall management improvement and the avoidance of climate-related losses. Climate change will contribute to water problems, escalating irrigation demand during the drought period, and increasing water loss with evaporation. The future of the countries of the Aral Sea basin then depends on both the regional scenario of water management policy and a global scenario of climate change, and is integrated with global socioeconomic scenarios. We formulate a set of regional policy scenarios (“Business as Usual”, “Falling Behind” and “Closing the Gap”) and demonstrate how each of them corresponds to IPCC SRES scenarios, the latter used as an input to the General Circulation Models (GCMs). Then we discuss the relative effectiveness of the introduced scenarios for mitigating water problems in the region, taking into account the adaptation through changing water demand for agriculture. Finally, we introduce the results of multimodel analysis of GCM climate projections, especially in relation to the change in precipitation and frequency of droughts, and

  15. Global and regional cooling in a warming climate from CMIP5 models

    NASA Astrophysics Data System (ADS)

    Medhaug, Iselin; Drange, Helge

    2015-04-01

    Instrumental temperature records show that the global climate may experience decadal-scale (hiatus) periods without warming despite an indisputable long-term warming trend. A large range of factors have been proposed to explain these non-warming decades, like volcanic cooling, reduced solar energy input, low stratospheric water vapor content, elevated tropospheric aerosols, internal variability of the climate system, or a combination thereof. We have analysed 17 global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5), identifying the likelihood and duration of periods without warming in the four Representative Concentration Pathway (RCP) scenarios RCP2.6, RCP4.5, RCP6.0 and RCP8.5, together with the preindustrial control and historical simulations. We find that non-warming periods, when the effect of volcanic eruptions and variations in the solar cycle are neglected, may last for up to 10, 15 and 30 years for RCP8.5, RCP6.0 and RCP 4.5, respectively. Regionally, the likelihood of a decadal-scale hiatus periods decrease first in the tropical Atlantic, Indian Ocean and western Pacific with increasing global temperatures in the RCP scenarios. The North Atlantic and the Southern Ocean are the regions with largest variability relative to the regional warming signal. As a response to the global temperature increase, the radiative imbalance at top of the atmosphere increases and the global oceans warm. This holds for both the upper and the deep ocean in all scenarios. In the CMIP5 simulations, anomalous uptake and storage of ocean heat are the main factors explaining the decadal-scale surface temperature hiatus periods. The tropical East Pacific is a key region for these variations, acting in tandem with basin-scale anomalies in the sea level pressure. On sub-decadal time scales, ocean storage of heat is largest and comparable in magnitude in the Pacific and Southern Oceans, followed by the Atlantic Ocean. We find no relation

  16. Impacts on regional climate of Amazon deforestation

    SciTech Connect

    Dickinson, R.E.; Kennedy, P. NCAR, Boulder, CO )

    1992-10-01

    A simulation of the climate response to Amazon deforestation has been carried out. Precipitation is decreased on the average by 25 percent or 1.4 mm/day, with ET and runoff both decreasing by 0.7 mm/day. Modifications of surface energy balance through change of albedo and roughness are complicated by cloud feedbacks. The initial decrease of the absorption of solar radiation by higher surface albedos is largely cancelled by a reduction in cloud cover, but consequent reduction in downward longwave has a substantial impact on surface energy balance. Smoke aerosols might have an effect comparable to deforestation during burning season. 8 refs.

  17. Wave climate model of the Mid-Atlantic shelf and shoreline (Virginian Sea): Model development, shelf geomorphology, and preliminary results

    NASA Technical Reports Server (NTRS)

    Goldsmith, V.; Morris, W. D.; Byrne, R. J.; Whitlock, C. H.

    1974-01-01

    A computerized wave climate model is developed that applies linear wave theory and shelf depth information to predict wave behavior as they pass over the continental shelf as well as the resulting wave energy distributions along the coastline. Reviewed are also the geomorphology of the Mid-Atlantic Continental Shelf, wave computations resulting from 122 wave input conditions, and a preliminary analysis of these data.

  18. Cold-climate slope deposits and landscape modifications of the Mid-Atlantic Coastal Plain, Eastern USA

    USGS Publications Warehouse

    Newell, W.L.; Dejong, B.D.

    2011-01-01

    The effects of Pleistocene cold-climate geomorphology are distributed across the weathered and eroded Mid-Atlantic Coastal Plain uplands from the Wisconsinan terminal moraine south to Tidewater Virginia. Cold-climate deposits and landscape modifications are superimposed on antecedent landscapes of old, weathered Neogene upland gravels and Pleistocene marine terraces that had been built during warm periods and sea-level highstands. In New Jersey, sequences of surficial deposits define a long history of repeating climate change events. To the south across the Delmarva Peninsula and southern Maryland, most antecedent topography has been obscured by Late Pleistocene surficial deposits. These are spatially variable and are collectively described as a cold-climate alloformation. The cold-climate alloformation includes time-transgressive details of climate deterioration from at least marine isotope stage (MIS) 4 through the end of MIS 2. Some deposits and landforms within the alloformation may be as young as the Younger Dryas. Southwards along the trend of the Potomac River, these deposits and their climatic affinities become diffused. In Virginia, a continuum of erosion and surficial deposits appears to be the product of ‘normal’ temperate, climate-forced processes. The cold-climate alloformation and more temperate deposits in Virginia are being partly covered by Holocene alluvium and bay mud.

  19. Protecting Health from Climate Change in the WHO European Region

    PubMed Central

    Wolf, Tanja; Sanchez Martinez, Gerardo; Cheong, Hae-Kwan; Williams, Eloise; Menne, Bettina

    2014-01-01

    “How far are we in the WHO European Region in implementing action to counter the health impacts of climate change?” This was the question posed to representatives of Member States in the WHO European Region of in the WHO working group on health in climate change (HIC). Twenty-two Member States provided answers to a comprehensive 2012 questionnaire that focused on eight thematic areas (governance; vulnerability, impact and adaptation (health) assessments (VIA); adaptation strategies and action plans; climate change mitigation; strengthening health systems; raising awareness and building capacity; greening health services; and sharing best practices). Strong development has been in climate change vulnerability and impact assessments, as well as strengthening health systems and awareness raising. Areas where implementation would benefit from further action are the development of national health adaptation plans, greening health systems, sharing best practices and reducing greenhouse gas (GHG) emissions in other sectors. At the Fifth Ministerial Conference on Environment and Health in Parma, Itatly in 2010, the European Commitment to Act on climate change and health and the European Regional Framework for Action to protect health from climate change were endorsed by the fifty-three European Member States. The results of this questionnaire present the most comprehensive assessment so far of progress made by European Member States to protect public health from climate change since the Parma Conference agreements. PMID:24937528

  20. Regional climate model performance in the Lake Victoria basin

    NASA Astrophysics Data System (ADS)

    Williams, Karina; Chamberlain, Jill; Buontempo, Carlo; Bain, Caroline

    2015-03-01

    Lake Victoria, the second largest freshwater lake in the world, plays a crucial role in the hydrology of equatorial eastern Africa. Understanding how climate change may alter rainfall and evaporation patterns is thus of vital importance for the economic development and the livelihood of the region. Regional rainfall distribution appears, up to a large extent, to be controlled by local drivers which may be not well resolved in general circulation model simulations. We investigate the performance over the Lake Victoria basin of an ensemble of UK Met Office Hadley Centre regional climate model (HadRM3P) simulations at 50 km, driven by five members of the Hadley Centre global perturbed-physics ensemble (QUMP). This is part of the validation of an ensemble of simulations that has been used to assess the impacts of climate change over the continent over the period 1950-2099. We find that the regional climate model is able to simulate a lake/land breeze over Lake Victoria, which is a significant improvement over the driving global climate model and a vital step towards reproducing precipitation characteristics in the region. The local precipitation correlates well with large-scale processes in the Pacific Ocean and Indian Ocean, which is in agreement with observations. We find that the spatial pattern of precipitation in the region and the diurnal cycle of convection is well represented although the amount of rainfall over the lake appears to be overestimated in most seasons. Reducing the observational uncertainty in precipitation over the lake through future field campaigns would enable this model bias to be better quantified. We conclude that increasing the spatial resolution of the model significantly improves its ability to simulate the current climate of the Lake Victoria basin. We suggest that, despite the higher computational costs, the inclusion of a model which allows two-way interactions between the lake and its surroundings should be seriously considered for

  1. Perceptible changes in regional precipitation in a future climate

    NASA Astrophysics Data System (ADS)

    Mahlstein, Irina; Portmann, Robert W.; Daniel, John S.; Solomon, Susan; Knutti, Reto

    2012-03-01

    Evidence is strong that the changes observed in the Earth's globally averaged temperature over the past half-century are caused to a large degree by human activities. Efforts to document accompanying precipitation changes in observations have met with limited success, and have been primarily focussed on large-scale regions in order to reduce the relative impact of the natural variability of precipitation as compared to any potential forced change. Studies have not been able to identify statistically significant changes in observed precipitation on small spatial scales. General circulation climate models offer the possibility to extend the analysis of precipitation changes into the future, to determine when simulated changes may emerge from the simulated variability locally as well as regionally. Here we estimate the global temperature increase needed for the precipitation “signal” to emerge from the “noise” of interannual variability within various climatic regions during their wet season. The climatic regions are defined based on cluster analysis. The dry season is not included due to poor model performance as compared to measurements during the observational period. We find that at least a 1.4°C warmer climate compared with the early 20th century is needed for precipitation changes to become statistically significant in any of the analysed climate regions. By the end of this century, it is likely that many land regions will experience statistically significant mean precipitation changes during wet season relative to the early 20th century based on an A1B scenario.

  2. An observational and modeling study of the regional impacts of climate variability

    NASA Astrophysics Data System (ADS)

    Horton, Radley M.

    during El Nino events. Based on the results from Chapter One, the analysis is expanded in several ways in Chapter Two. To gain a more complete and statistically meaningful understanding of ENSO, a 25 year time period is used instead of a single event. To gain a fuller understanding of climate variability, additional patterns are analyzed. Finally analysis is conducted at the regional scales that are of interest to farmers and agricultural planners. Key findings are that GISS ModelE can reproduce: (1) the spatial pattern associated with two additional related modes, the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO); (2) rainfall patterns in Indonesia; and (3) dynamical features such as sea level pressure (SLP) gradients and wind in the study regions. When run in coupled mode, the same model reproduces similar modes spatially but with reduced variance and weak teleconnections. Since Chapter Two identified Western Indonesia as the region where GCMs hold the most promise for agricultural applications, in Chapter Three a finer spatial and temporal scale analysis of ENSO's effects is presented. Agricultural decision-making is also linked to ENSO's climate effects. Early rainy season precipitation and circulation, and same-season planting and harvesting dates, are shown to be sensitive to ENSO. The locus of ENSO convergence and rainfall anomalies is shown to be near the axis of rainy season establishment, defined as the 6--8 mm/day isohyet, an approximate threshold for irrigated rice cultivation. As the axis tracks south and east between October and January, so do ENSO anomalies. Circulation anomalies associated with ENSO are shown to be similar to those associated with rainfall anomalies, suggesting that long lead-time ENSO forecasts may allow more adaptation than 'wait and see' methods, with little loss of forecast skill. Additional findings include: (1) rice and corn yields are lower (higher) during dry (wet) trimesters and El Nino (La Nina) years; and (2

  3. Size Scaling in Western North Atlantic Loggerhead Turtles Permits Extrapolation between Regions, but Not Life Stages

    PubMed Central

    Marn, Nina; Klanjscek, Tin; Stokes, Lesley; Jusup, Marko

    2015-01-01

    Introduction Sea turtles face threats globally and are protected by national and international laws. Allometry and scaling models greatly aid sea turtle conservation and research, and help to better understand the biology of sea turtles. Scaling, however, may differ between regions and/or life stages. We analyze differences between (i) two different regional subsets and (ii) three different life stage subsets of the western North Atlantic loggerhead turtles by comparing the relative growth of body width and depth in relation to body length, and discuss the implications. Results and Discussion Results suggest that the differences between scaling relationships of different regional subsets are negligible, and models fitted on data from one region of the western North Atlantic can safely be used on data for the same life stage from another North Atlantic region. On the other hand, using models fitted on data for one life stage to describe other life stages is not recommended if accuracy is of paramount importance. In particular, young loggerhead turtles that have not recruited to neritic habitats should be studied and modeled separately whenever practical, while neritic juveniles and adults can be modeled together as one group. Even though morphometric scaling varies among life stages, a common model for all life stages can be used as a general description of scaling, and assuming isometric growth as a simplification is justified. In addition to linear models traditionally used for scaling on log-log axes, we test the performance of a saturating (curvilinear) model. The saturating model is statistically preferred in some cases, but the accuracy gained by the saturating model is marginal. PMID:26629702

  4. Regional climate impacts of a biofuels policy projection

    NASA Astrophysics Data System (ADS)

    Anderson, Christopher J.; Anex, Robert P.; Arritt, Raymond W.; Gelder, Brian K.; Khanal, Sami; Herzmann, Daryl E.; Gassman, Phillip W.

    2013-03-01

    The potential for regional climate change arising from adoption of policies to increase production of biofuel feedstock is explored using a regional climate model. Two simulations are performed using the same atmospheric forcing data for the period 1979-2004, one with present-day land use and monthly phenology and the other with land use specified from an agro-economic prediction of energy crop distribution and monthly phenology consistent with this land use change. In Kansas and Oklahoma, where the agro-economic model predicts 15-30% conversion to switchgrass, the regional climate model simulates locally lower temperature (especially in spring), slightly higher relative humidity in spring and slightly lower relative humidity in summer, and summer depletion of soil moisture. This shows the potential for climate impacts of biofuel policies and raises the question of whether soil water depletion may limit biomass crop productivity in agricultural areas that are responsive to the policies. We recommend the use of agronomic models to evaluate the possibility that soil moisture depletion could reduce productivity of biomass crops in this region. We conclude, therefore, that agro-economic and climate models should be used iteratively to examine an ensemble of agricultural land use and climate scenarios, thereby reducing the possibility of unforeseen consequences from rapid changes in agricultural production systems.

  5. Modeled regional climate change and California endemic oak ranges

    PubMed Central

    Kueppers, Lara M.; Snyder, Mark A.; Sloan, Lisa C.; Zavaleta, Erika S.; Fulfrost, Brian

    2005-01-01

    In the coming century, anthropogenic climate change will threaten the persistence of restricted endemic species, complicating conservation planning. Although most efforts to quantify potential shifts in species' ranges use global climate model (GCM) output, regional climate model (RCM) output may be better suited to predicting shifts by restricted species, particularly in regions with complex topography or other regionally important climate-forcing factors. Using a RCM-based future climate scenario, we found that potential ranges of two California endemic oaks, Quercus douglasii and Quercus lobata, shrink considerably (to 59% and 54% of modern potential range sizes, respectively) and shift northward. This result is markedly different from that obtained by using a comparable GCM-based scenario, under which these species retain 81% and 73% of their modern potential range sizes, respectively. The difference between RCM- and GCM-based scenarios is due to greater warming and larger precipitation decreases during the growing season predicted by the RCM in these species' potential ranges. Based on the modeled regional climate change, <50% of protected land area currently containing these species is expected to contain them under a future midrange “business-as-usual” path of greenhouse gas emissions. PMID:16260750

  6. Potential climatic impacts of vegetation change: A regional modeling study

    USGS Publications Warehouse

    Copeland, J.H.; Pielke, R.A.; Kittel, T.G.F.

    1996-01-01

    The human species has been modifying the landscape long before the development of modern agrarian techniques. Much of the land area of the conterminous United States is currently used for agricultural production. In certain regions this change in vegetative cover from its natural state may have led to local climatic change. A regional climate version of the Colorado State University Regional Atmospheric Modeling System was used to assess the impact of a natural versus current vegetation distribution on the weather and climate of July 1989. The results indicate that coherent regions of substantial changes, of both positive and negative sign, in screen height temperature, humidity, wind speed, and precipitation are a possible consequence of land use change throughout the United States. The simulated changes in the screen height quantities were closely related to changes in the vegetation parameters of albedo, roughness length, leaf area index, and fractional coverage. Copyright 1996 by the American Geophysical Union.

  7. A catalog of moisture sources for continental climatic regions

    NASA Astrophysics Data System (ADS)

    Nieto, Raquel; Castillo, Rodrigo; Drumond, Anita; Gimeno, Luis

    2014-06-01

    This technical note describes a catalog of moisture sources for two sets of continental climatic regions: one based on regions with similar late 20th century mean climate and similar projected late 21st century precipitation changes, and the other widely used in IPCC assessment reports. By illustrating with one region by classification, the European one was selected and we identify and characterize all the major sources of moisture, and analyze their interannual variability and the role of the three dominant modes of global climate variability, including the El Niño-Southern Oscillation (ENSO) and the Northern and Southern Annular Modes (NAM, SAM). We also estimate the influence of those oceanic regions that will see the greatest increases in evaporation rate in future years.

  8. Atmospheric and Climate Aspects of Russian Regions Sustainability

    NASA Astrophysics Data System (ADS)

    Golitsyn, G. S.; Dubovsky, S. V.; Ginzburg, A. S.; Mokhov, I. I.; Khomyakov, P. M.

    Russia is one of the first countries created the national program of sustainable devel- opment. The Presidential Decree SOn the national strategy of the Russian Federation & cedil;in the environment protection and sustainable developmentT was issued by in 1994. Atmospheric and climate aspects play very important roles in the sustainable devel- opment at the regional level in Russia as well as at national one. Last year Russian Academy of Sciences in collaboration with some leaders of the local Russian au- thorities started the Project SSustainable development of Russia and its regionsT. In & cedil; this project the problems of Russian socio-economical development are considered together with regional atmospheric and climate changes, environmental and natural resources, population, urbanization, energetic and new technology development, and so on. The main problems of Russian regions socio-economical development related to global and local climate changes, environmental and natural resources, urbanization will be discussed.

  9. Origin of millennial-scale climate signals in the subtropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Billups, Katharina; Scheinwald, Andre

    2014-06-01

    We present a high-resolution planktonic foraminiferal stable isotope record (Globigerinoides ruber) spanning marine oxygen isotope stages (MISs) 6 through 8 in the northwestern subtropical Atlantic Ocean (Ocean Drilling Program Leg 172 Site 1059). The record fills a gap to produce an about 1.3 Myr long continuous time series of high-frequency (> ~1/12 kyr) surface ocean hydrography, the first of this kind. We test the hypothesis that the suborbital climate signals (i.e., half and quarter precession cycles) are linked to precession forcing in tropical latitudes. Semiprecession cycles present between 0 and 320 ka are of the right periodicity to relate to the dominant precession forcing (23 kyr). These cycles are evident as double peaks within the given precession framework, and there is good match in the amplitude modulation of the filter output and the δ18O time series. Quarter precession cycles dominate the suborbital spectra between 320 ka and 1.3 Ma. Periodicities are close to those expected from the harmonics of the dominant precession peaks in the δ18O record, but present in the time series only intermittently, and their amplitude modulation does not match that of the primary precession period. Thus, only the half precession cycles evidence a response to low-latitude insolation such as that introduced by insolation maxima at the equinoxes or solstices during the course of a precession cycle. Additionally, we find well-defined, rapid (~1.5-2 kyr) variations across the first of the interglacial maxima of MIS 7 adding to evidence of non-ice sheet-related forcing factors in driving climate instabilities.

  10. Impact of observed North Atlantic multidecadal variations to European summer climate: a linear baroclinic response to surface heating

    NASA Astrophysics Data System (ADS)

    Ghosh, Rohit; Müller, Wolfgang A.; Baehr, Johanna; Bader, Jürgen

    2016-07-01

    The observed prominent multidecadal variations in the central to eastern (C-E) European summer temperature are closely related to the Atlantic multidecadal variability (AMV). Using the Twentieth Century Reanalysis project version 2 data for the period of 1930-2012, we present a mechanism by which the multidecadal variations in the C-E European summer temperature are associated to a linear baroclinic atmospheric response to the AMV-related surface heat flux. Our results suggest that over the north-western Atlantic, the positive heat flux anomaly triggers a surface baroclinic pressure response to diabatic heating with a negative surface pressure anomaly to the east of the heat source. Further downstream, this response induces an east-west wave-like pressure anomaly. The east-west wave-like response in the sea level pressure structure, to which we refer as North-Atlantic-European East West (NEW) mode, is independent of the summer North Atlantic Oscillation and is the principal mode of variations during summer over the Euro-Atlantic region at multidecadal time scales. The NEW mode causes warming of the C-E European region by creating an atmospheric blocking-like situation. Our findings also suggest that this NEW mode is responsible for the multidecadal variations in precipitation over the British Isles and north-western Europe.

  11. Simulation of Climatic Changes in the Arctic and North Atlantic During Recent Decades

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    The interactions of the atmosphere and ice-ocean system in the Arctic will be studied using a coupled ice-ocean model which will also use ice drift derived from microwave observations as forcing. We especially search for linkages between the recent large climatic shifts in the Arctic Ocean and atmosphere for which period we also have microwave sea ice data. The coupled model area covers the whole N. Atlantic thus interactions between the lower latitudes are also investigated because we anticipate that the same large scale atmospheric patterns which dominate the midlatitudes extend their influence on the Arctic. The model hindcast for 1951-1993 shows clear decadal variability in the leading modes of ocean circulation. No specific low-freq modes are expected for the ice drift because its spectrum is white. However, the ice drift exhibits two see-saw patterns in response to the leading atmospheric circulation mode ('Arctic Oscillation'), one of them is the well-known out of phase relationship between Baffin Bay and Barents-Kara Seas, the other one is between Siberian shelf and Alaskan Coast (Hakkinen and Geiger, 2000).

  12. Regional Climate Model Projections for the State of Washington

    SciTech Connect

    Salathe, E.; Leung, Lai-Yung R.; Qian, Yun; Zhang, Yongxin

    2010-05-05

    Global climate models do not have sufficient spatial resolution to represent the atmospheric and land surface processes that determine the unique regional heterogeneity of the climate of the State of Washington. If future large-scale weather patterns interact differently with the local terrain and coastlines than current weather patterns, local changes in temperature and precipitation could be quite different from the coarse-scale changes projected by global models. Regional climate models explicitly simulate the interactions between the large-scale weather patterns simulated by a global model and the local terrain. We have performed two 100-year climate simulations using the Weather and Research Forecasting (WRF) model developed at the National Center for Atmospheric Research (NCAR). One simulation is forced by the NCAR Community Climate System Model version 3 (CCSM3) and the second is forced by a simulation of the Max Plank Institute, Hamburg, global model (ECHAM5). The mesoscale simulations produce regional changes in snow cover, cloudiness, and circulation patterns associated with interactions between the large-scale climate change and the regional topography and land-water contrasts. These changes substantially alter the temperature and precipitation trends over the region relative to the global model result or statistical downscaling. To illustrate this effect, we analyze the changes from the current climate (1970-1999) to the mid 21st century (2030-2059). Changes in seasonal-mean temperature, precipitation, and snowpack are presented. Several climatological indices of extreme daily weather are also presented: precipitation intensity, fraction of precipitation occurring in extreme daily events, heat wave frequency, growing season length, and frequency of warm nights. Despite somewhat different changes in seasonal precipitation and temperature from the two regional simulations, consistent results for changes in snowpack and extreme precipitation are found in

  13. Vegetation and climate development on the Atlantic Coastal Plain during the late Mid-Miocene Climatic Optimum (IODP Expedition 313)

    NASA Astrophysics Data System (ADS)

    Prader, Sabine; Kotthoff, Ulrich; McCarthy, Francine; Greenwood, David

    2015-04-01

    which was reminiscent of Oligocene and early Miocene ecosystems analyzed in previous studies (e.g. Kotthoff et al. 2014). The ecosystem was characterized by oak-hickory forests which probably dominated in the lowlands, while frequent occurrence of conifer pollen (Pinus, Picea, Abies, Sciadopitys, and Tsuga canadensis) indicate that conifer forests prevailed in higher altitudes during the MMCO. We assume that the Miocene uplift of the Appalachian Mountains (e.g. Gallen et al., 2013) led to the proliferation of mountainous taxa and thus to an increase of related pollen taxa in the palynological record. References: Gallen, S. F., Wegmann, K. W., Bohnenstieh, D. W. R.: Miocene rejuvenation of topographic relief in the southern Appalachians, GSA Today, 23, 4-10, 2013. Kotthoff, U., McCarthy, F.M.G., Greenwood, D.R., Müller-Navarra, K., Prader, S., Hesselbo, S.P., (2014): Vegetation and climate development on the Atlantic Coastal Plain from 33 to 13 million years ago (IODP expedition 313). Climate of the Past 10, 1523-1539.

  14. Verification of regional climate models over the territory of Ukraine

    NASA Astrophysics Data System (ADS)

    Krakovska, S.; Palamarchuk, L.; Shedemenko, I.; Djukel, G.; Gnatjuk, N.

    2009-04-01

    Verification of regional climate models (RCMs) over the territory of Ukraine was the first stage of the National project for assessment of possible climate change and its impact on the economic and social life in Ukraine in XXI century. Since Ukraine has pretty different climates in different parts, the territory of Ukraine was divided on 11 regions with more or less uniform climate conditions: 7 almost equal in space regions in plain terrain, 2 - in coastal zones near the Black and Azov seas and 2 - in the Carpathian and the Crimean mountains. Verification of RCMs for climate characteristics was carried out for each defined region separately. Data of meteorological network in Ukraine (187 stations) and the Climate Research Unit (CRU 10-min global data-set) for multy-year monthly, season and annual means of temperature and precipitation for the period 1961-90 were used for verification of models' results. Two RCMs were used in the analysis of the past climate of Ukraine: REMO (MPI-M, Hamburg) and RegCM3 (ICTP, Trieste). Both models were constructed with initial and boundary conditions from ERA-40 data-set with horizontal spacing of ~25 km and vertically 27 (REMO) and 18 (RegCM3) Z-σ levels. In a whole, both models demonstrated better ability for temperature than precipitation characteristics. Very high correlation of 0.9 was found between models, network and CRU for temperatures and 0.7-0.8 for precipitation. Generally, models were warmer especially for summer months up to 2 oC. More precipitation in the models was found for winter season and less - for summer and in the mountainous subregions comparably with observations. In perspective we intend to run RCMs initialized with GCMs for the same period and for XXI century and account for the obtained systematic models' errors in the analysis of possible climate change over the territory of Ukraine.

  15. The WASCAL regional climate simulations for West Africa - how to add value to existing climate projections

    NASA Astrophysics Data System (ADS)

    Arnault, J.; Heinzeller, D.; Klein, C.; Dieng, D.; Smiatek, G.; Bliefernicht, J.; Sylla, M. B.; Kunstmann, H.

    2015-12-01

    With climate change being one of the most severe challenges to rural Africa in the 21st century, West Africa is facing an urgent need to develop effective adaptation and mitigation measures to protect its constantly growing population. WASCAL (West African Science Service Center on Climate Change and Adapted Land Use) is a large-scale research-focused program designed to enhance the resilience of human and environmental systems to climate change and increased variability. An integral part of its climate services is the provisioning of a new set of high resolution, ensemble-based regional climate change scenarios for the region of West Africa. In this contribution, we present the overall concept of the WASCAL regional climate projections and provide information on the dissemination of the data. We discuss the model performance over the validation period for two of the three regional climate models employed, the Weather Research & Forecasting Tool (WRF) and the Consortium for Small-scale Modeling Model COSMO in Climate Mode (COSMO-CLM), and give details about a novel precipitation database used to verify the models. Particular attention is paid to the representation of the dynamics of the West African Summer Monsoon and to the added value of our high resolution models over existing data sets. We further present results on the climate change signal obtained from the WRF model runs for the periods 2020-2050 and 2070-2100 and compare them to current state-of-the-art projections from the CORDEX project. As an example, the figure shows the different climate change signals obtained for the total annual rainfall with respect to the 1980-2010 mean (WRF-E: WASCAL 12km high-resolution run MPI-ESM + WRFV3.5.1, CORDEX-E: 50km medium-resolution run MPI-ESM + RCA4, CORDEX-G: 50km medium-resolution run GFDL-ESM + RCA4).

  16. Sensitivity of regional climate to global temperature and forcing

    NASA Astrophysics Data System (ADS)

    Tebaldi, Claudia; O'Neill, Brian; Lamarque, Jean-François

    2015-07-01

    The sensitivity of regional climate to global average radiative forcing and temperature change is important for setting global climate policy targets and designing scenarios. Setting effective policy targets requires an understanding of the consequences exceeding them, even by small amounts, and the effective design of sets of scenarios requires the knowledge of how different emissions, concentrations, or forcing need to be in order to produce substantial differences in climate outcomes. Using an extensive database of climate model simulations, we quantify how differences in global average quantities relate to differences in both the spatial extent and magnitude of climate outcomes at regional (250-1250 km) scales. We show that differences of about 0.3 °C in global average temperature are required to generate statistically significant changes in regional annual average temperature over more than half of the Earth’s land surface. A global difference of 0.8 °C is necessary to produce regional warming over half the land surface that is not only significant but reaches at least 1 °C. As much as 2.5 to 3 °C is required for a statistically significant change in regional annual average precipitation that is equally pervasive. Global average temperature change provides a better metric than radiative forcing for indicating differences in regional climate outcomes due to the path dependency of the effects of radiative forcing. For example, a difference in radiative forcing of 0.5 W m-2 can produce statistically significant differences in regional temperature over an area that ranges between 30% and 85% of the land surface, depending on the forcing pathway.

  17. Regional projections of North Indian climate for adaptation studies.

    PubMed

    Mathison, Camilla; Wiltshire, Andrew; Dimri, A P; Falloon, Pete; Jacob, Daniela; Kumar, Pankaj; Moors, Eddy; Ridley, Jeff; Siderius, Christian; Stoffel, Markus; Yasunari, T

    2013-12-01

    Adaptation is increasingly important for regions around the world where large changes in climate could have an impact on populations and industry. The Brahmaputra-Ganges catchments have a large population, a main industry of agriculture and a growing hydro-power industry, making the region susceptible to changes in the Indian Summer Monsoon, annually the main water source. The HighNoon project has completed four regional climate model simulations for India and the Himalaya at high resolution (25km) from 1960 to 2100 to provide an ensemble of simulations for the region. In this paper we have assessed the ensemble for these catchments, comparing the simulations with observations, to give credence that the simulations provide a realistic representation of atmospheric processes and therefore future climate. We have illustrated how these simulations could be used to provide information on potential future climate impacts and therefore aid decision-making using climatology and threshold analysis. The ensemble analysis shows an increase in temperature between the baseline (1970-2000) and the 2050s (2040-2070) of between 2 and 4°C and an increase in the number of days with maximum temperatures above 28°C and 35°C. There is less certainty for precipitation and runoff which show considerable variability, even in this relatively small ensemble, spanning zero. The HighNoon ensemble is the most complete data for the region providing useful information on a wide range of variables for the regional climate of the Brahmaputra-Ganges region, however there are processes not yet included in the models that could have an impact on the simulations of future climate. We have discussed these processes and show that the range from the HighNoon ensemble is similar in magnitude to potential changes in projections where these processes are included. Therefore strategies for adaptation must be robust and flexible allowing for advances in the science and natural environmental changes.

  18. US regional tornado outbreaks and their links to spring ENSO phases and North Atlantic SST variability

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Ki; Wittenberg, Andrew T.; Enfield, David B.; Weaver, Scott J.; Wang, Chunzai; Atlas, Robert

    2016-04-01

    Recent violent and widespread tornado outbreaks in the US, such as occurred in the spring of 2011, have caused devastating societal impact with significant loss of life and property. At present, our capacity to predict US tornado and other severe weather risk does not extend beyond seven days. In an effort to advance our capability for developing a skillful long-range outlook for US tornado outbreaks, here we investigate the spring probability patterns of US regional tornado outbreaks during 1950-2014. We show that the four dominant springtime El Niño-Southern Oscillation (ENSO) phases (persistent versus early-terminating El Niño and resurgent versus transitioning La Niña) and the North Atlantic sea surface temperature tripole variability are linked to distinct and significant US regional patterns of outbreak probability. These changes in the probability of outbreaks are shown to be largely consistent with remotely forced regional changes in the large-scale atmospheric processes conducive to tornado outbreaks. An implication of these findings is that the springtime ENSO phases and the North Atlantic SST tripole variability may provide seasonal predictability of US regional tornado outbreaks.

  19. Informing Decisions with a Climate Synthesis Product: Implications for Regional Climate Services

    NASA Astrophysics Data System (ADS)

    Guido, Z.; Hill, D.; Crimmins, M.; Ferguson, D. B.

    2012-12-01

    The demand for regional climate information is increasing and spurring efforts to provide a broad slate of climate services that inform policy and resource management and elevate general knowledge. Routine syntheses of existing climate-related information may be an effective strategy for connecting climate information to decision making, but few studies have formally assessed their contribution to informing decisions. During the 2010-2011 winter, drought conditions expanded and intensified in Arizona and New Mexico, creating an opportunity to develop and evaluate a pithy, monthly regional climate communication product—La Niña Drought Tracker—that synthesized and interpreted drought and climate information. Six issues were published and subsequently evaluated through an online survey. On average, 417 people consulted the publication each month. Many of the survey respondents indicated that they made at least one drought-related decision, and the product at least moderately influenced the majority of those decisions, some of which helped mitigate economic losses and reduce climate vulnerability. The product also improved understanding of climate and drought for more than 90 percent of the respondents and helped the majority of them better prepare for drought. These, and other results demonstrate that routine interpretation and synthesis of existing climate information can help enhance access to and understanding and use of climate information in decision-making. Moreover, developing regional, contextual knowledge within climate service programs can facilitate the implementation of activities like the Tracker that enhance the use of climate information without engaging in time-consuming collaborative processes that can prevent the timely production of the services. We present results from the case study of the Tracker and place it within the context of the challenges and opportunities associated with providing climate services, particularly those services that

  20. Regional analysis of ground and above-ground climate

    SciTech Connect

    Not Available

    1981-12-01

    The regional suitability of underground construction as a climate control technique is discussed with reference to (1) a bioclimatic analysis of long-term weather data for 29 locations in the United States to determine appropriate above ground climate control techniques, (2) a data base of synthesized ground temperatures for the coterminous United States, and (3) monthly dew point ground temperature comparisons for identifying the relative likelihood of condensation from one region to another. It is concluded that the suitability of earth tempering as a practice and of specific earth-sheltered design stereotypes varies geographically; while the subsurface almost always provides a thermal advantage on its own terms when compared to above ground climatic data, it can, nonetheless, compromise the effectiveness of other, regionally more important climate control techniques. Also contained in the report are reviews of above and below ground climate mapping schemes related to human comfort and architectural design, and detailed description of a theoretical model of ground temperature, heat flow, and heat storage in the ground. Strategies of passive climate control are presented in a discussion of the building bioclimatic analysis procedure which has been applied in a computer analysis of 30 years of weather data for each of 29 locations in the United States.

  1. Regional analysis of ground and above-ground climate

    NASA Astrophysics Data System (ADS)

    1981-12-01

    The regional suitability of underground construction as a climate control technique is discussed with reference to (1) a bioclimatic analysis of long term weather data for 29 locations in the United States to determine appropriate above ground climate control techniques, (2) a data base of synthesized ground temperatures for the coterminous United States, and (3) monthly dew point ground temperature comparisons for identifying the relative likelihood of condensation from one region to another. It is concluded that the suitability of Earth tempering as a practice and of specific Earth sheltered design stereotypes varies geographically; while the subsurface almost always provides a thermal advantage on its own terms when compared to above ground climatic data, it can, nonetheless, compromise the effectiveness of other, regionally more important climate control techniques. Reviews of above and below ground climate mapping schemes related to human comfort and architectural design, and detailed description of a theoretical model of ground temperature, heat flow, and heat storage in the ground are included. Strategies of passive climate control are presented in a discussion of the building bioclimatic analysis procedure which has been applied in a computer analysis of 30 years of weather data for each of 20 locations in the United States.

  2. A regional approach to climate adaptation in the Nile Basin

    NASA Astrophysics Data System (ADS)

    Butts, Michael B.; Buontempo, Carlo; Lørup, Jens K.; Williams, Karina; Mathison, Camilla; Jessen, Oluf Z.; Riegels, Niels D.; Glennie, Paul; McSweeney, Carol; Wilson, Mark; Jones, Richard; Seid, Abdulkarim H.

    2016-10-01

    The Nile Basin is one of the most important shared basins in Africa. Managing and developing the water resources within the basin must not only address different water uses but also the trade-off between developments upstream and water use downstream, often between different countries. Furthermore, decision-makers in the region need to evaluate and implement climate adaptation measures. Previous work has shown that the Nile flows can be highly sensitive to climate change and that there is considerable uncertainty in climate projections in the region with no clear consensus as to the direction of change. Modelling current and future changes in river runoff must address a number of challenges; including the large size of the basin, the relative scarcity of data, and the corresponding dramatic variety of climatic conditions and diversity in hydrological characteristics. In this paper, we present a methodology, to support climate adaptation on a regional scale, for assessing climate change impacts and adaptation potential for floods, droughts and water scarcity within the basin.

  3. Impact of regional climate change on human health.

    PubMed

    Patz, Jonathan A; Campbell-Lendrum, Diarmid; Holloway, Tracey; Foley, Jonathan A

    2005-11-17

    The World Health Organisation estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30 years already claim over 150,000 lives annually. Many prevalent human diseases are linked to climate fluctuations, from cardiovascular mortality and respiratory illnesses due to heatwaves, to altered transmission of infectious diseases and malnutrition from crop failures. Uncertainty remains in attributing the expansion or resurgence of diseases to climate change, owing to lack of long-term, high-quality data sets as well as the large influence of socio-economic factors and changes in immunity and drug resistance. Here we review the growing evidence that climate-health relationships pose increasing health risks under future projections of climate change and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world. Potentially vulnerable regions include the temperate latitudes, which are projected to warm disproportionately, the regions around the Pacific and Indian oceans that are currently subjected to large rainfall variability due to the El Niño/Southern Oscillation sub-Saharan Africa and sprawling cities where the urban heat island effect could intensify extreme climatic events.

  4. Impact of regional climate change on human health

    NASA Astrophysics Data System (ADS)

    Patz, Jonathan A.; Campbell-Lendrum, Diarmid; Holloway, Tracey; Foley, Jonathan A.

    2005-11-01

    The World Health Organisation estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30years already claim over 150,000 lives annually. Many prevalent human diseases are linked to climate fluctuations, from cardiovascular mortality and respiratory illnesses due to heatwaves, to altered transmission of infectious diseases and malnutrition from crop failures. Uncertainty remains in attributing the expansion or resurgence of diseases to climate change, owing to lack of long-term, high-quality data sets as well as the large influence of socio-economic factors and changes in immunity and drug resistance. Here we review the growing evidence that climate-health relationships pose increasing health risks under future projections of climate change and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world. Potentially vulnerable regions include the temperate latitudes, which are projected to warm disproportionately, the regions around the Pacific and Indian oceans that are currently subjected to large rainfall variability due to the El Niño/Southern Oscillation sub-Saharan Africa and sprawling cities where the urban heat island effect could intensify extreme climatic events.

  5. Regional Analysis of Energy, Water, Land and Climate Interactions

    NASA Astrophysics Data System (ADS)

    Tidwell, V. C.; Averyt, K.; Harriss, R. C.; Hibbard, K. A.; Newmark, R. L.; Rose, S. K.; Shevliakova, E.; Wilson, T.

    2014-12-01

    Energy, water, and land systems interact in many ways and are impacted by management and climate change. These systems and their interactions often differ in significant ways from region-to-region. To explore the coupled energy-water-land system and its relation to climate change and management a simple conceptual model of demand, endowment and technology (DET) is proposed. A consistent and comparable analysis framework is needed as climate change and resource management practices have the potential to impact each DET element, resource, and region differently. These linkages are further complicated by policy and trade agreements where endowments of one region are used to meet demands in another. This paper reviews the unique DET characteristics of land, energy and water resources across the United States. Analyses are conducted according to the eight geographic regions defined in the 2014 National Climate Assessment. Evident from the analyses are regional differences in resources endowments in land (strong East-West gradient in forest, cropland and desert), water (similar East-West gradient), and energy. Demands likewise vary regionally reflecting differences in population density and endowment (e.g., higher water use in West reflecting insufficient precipitation to support dryland farming). The effect of technology and policy are particularly evident in differences in the energy portfolios across the eight regions. Integrated analyses that account for the various spatial and temporal differences in regional energy, water and land systems are critical to informing effective policy requirements for future energy, climate and resource management. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Co