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Sample records for climatic record deduced

  1. Proxy late Holocene climatic record deduced from northwest Alaska beach ridges

    SciTech Connect

    Mason, O.K.; Jordan, J.W.

    1992-03-01

    A climatically sensitive, oscillatory pattern of progradation and erosion is revealed in late Holocene accretionary sand ridge and barrier island complexes of Seward Peninsula, northwest Alaska. Archaeological and geological radiocarbon dates constrain the chronology for the Cape Espenberg beach ridge plain and the Shishmaref barrier islands, 50 km to the southwest. Cape Espenberg, the depositional sink for the northeastward longshore transport system, contains the oldest sedimentary deposits: 3700 +/- 90 B.P. (B-23170) old grass from a paleosol in a low dune. The oldest date on the Shishmaref barrier islands is 1550 +/- 70 B.P. (B-23183) and implies that the modern barrier is a comparatively recent phenomenon. Late Holocene sedimentation along the Seward Peninsula varied between intervals of rapid progradation and erosion. Rapid progradation predominated from 4000-3300 B.P. and from 2000-1200 B.P., with the generation of low beach ridges without dunes, separated by wide swales. During erosional periods higher dunes built atop beach ridges: as between 3300-2000 B.P. and intermittently from 1000 B.P. to the present. Dune formation correlates with the Neoglacial and Little Ice Age glacial advances and increased alluviation in northern and central Alaska, while rapid progradation is contemporaneous with warmer intervals of soil and/or, peat formation atop alluvial terraces, dated to 4000-3500 and 2000-1000 B.P.

  2. Climate change in the Turkana basin as deduced from a 4000 year long δO 18 record

    NASA Astrophysics Data System (ADS)

    Ricketts, R. D.; Johnson, T. C.

    1996-07-01

    A model of the oxygen isotopic composition of Lake Turkana waters sheds insight into the paleoclimatic interpretation of a δ 18O profile of inorganic calcite from a core taken from the lake. The model indicates that high frequency fluctuations seen in the isotopic record are probably due to shifts in lake level, while the long term increase of 1.4‰ seen from 4 to 2 kyr BP cannot be due solely to lake level change. It must be due to changes in other climatic parameters, such as the isotopic composition of the inflow. These findings suggests that the abrupt change observed in Lake Turkana (and many other African lakes) at 4 ka was the precursor to a 2000 year long adjustment in the climate over the Ethiopian Plateau. The isotopic record from Lake Turkana agrees with other paleoclimate records from the basin, including the diatom stratigraphy and radiocarbon dates on exposed shoreline deposits.

  3. Terrestrial climate variability and seasonality changes in the Mediterranean region between 15 000 and 4000 years BP deduced from marine pollen records

    NASA Astrophysics Data System (ADS)

    Dormoy, I.; Peyron, O.; Combourieu Nebout, N.; Goring, S.; Kotthoff, U.; Magny, M.; Pross, J.

    2009-10-01

    Pollen-based climate reconstructions were performed on two high-resolution pollen marines cores from the Alboran and Aegean Seas in order to unravel the climatic variability in the coastal settings of the Mediterranean region between 15 000 and 4000 years BP (the Lateglacial, and early to mid-Holocene). The quantitative climate reconstructions for the Alboran and Aegean Sea records focus mainly on the reconstruction of the seasonality changes (temperatures and precipitation), a crucial parameter in the Mediterranean region. This study is based on a multi-method approach comprising 3 methods: the Modern Analogues Technique (MAT), the recent Non-Metric Multidimensional Scaling/Generalized Additive Model method (NMDS/GAM) and Partial Least Squares regression (PLS). The climate signal inferred from this comparative approach confirms that cold and dry conditions prevailed in the Mediterranean region during the Oldest and Younger Dryas periods, while temperate conditions prevailed during the Bølling/Allerød and the Holocene. Our records suggest a West/East gradient of decreasing precipitation across the Mediterranean region during the cooler Late-glacial and early Holocene periods, similar to present-day conditions. Winter precipitation was highest during warm intervals and lowest during cooling phases. Several short-lived cool intervals (i.e. Older Dryas, another oscillation after this one (GI-1c2), Gerzensee/Preboreal Oscillations, 8.2 ka event, Bond events) connected to the North Atlantic climate system are documented in the Alboran and Aegean Sea records indicating that the climate oscillations associated with the successive steps of the deglaciation in the North Atlantic area occurred in both the western and eastern Mediterranean regions. This observation confirms the presence of strong climatic linkages between the North Atlantic and Mediterranean regions.

  4. Terrestrial climate variability and seasonality changes in the Mediterranean region between 15000 and 4000 years BP deduced from marine pollen records

    NASA Astrophysics Data System (ADS)

    Dormoy, I.; Peyron, O.; Combourieu-Neboutb, N.; Goring, S.; Kotthoff, U.; Magny, M.; Pross, J.

    2009-02-01

    Pollen-based climate reconstructions were performed on two high-resolution pollen - marines cores from the Alboran and Aegean Seas in order to unravel the climatic variability in the coastal settings of the Mediterranean region between 15 000 and 4000 cal yrs BP (the Lateglacial, and early to mid-Holocene). The quantitative climate reconstructions for the Alboran and Aegean Sea records focus mainly on the reconstruction of the seasonality changes (temperatures and precipitation), a crucial parameter in the Mediterranean region. This study is based on a multi-method approach comprising 3 methods: the Modern Analogues Technique (MAT), the recent Non-Metric Multidimensional Scaling/Generalized Additive Model method (NMDS/GAM) and Partial Least Squares regression (PLS). The climate signal inferred from this comparative approach confirms that cold and dry conditions prevailed in the Mediterranean region during the Heinrich event 1 and Younger Dryas periods, while temperate conditions prevailed during the Bølling/Allerød and the Holocene. Our records suggest a West/East gradient of decreasing precipitation across the Mediterranean region during the cooler Late-glacial and early Holocene periods, similar to present-day conditions. Winter precipitation was highest during warm intervals and lowest during cooling phases. Several short-lived cool intervals (i.e., Older Dryas, another oscillation after this one (GI-1c2), Gerzensee/Preboreal Oscillations, 8.2 ka event, Bond events) connected to the North Atlantic climate system are documented in the Alboran and Aegean Sea records indicating that the climate oscillations associated with the successive steps of the deglaciation in the North Atlantic area occurred in both the western and eastern Mediterranean regions. This observation confirms the presence of strong climatic linkages between the North Atlantic and Mediterranean regions.

  5. Seasonal climate variability in historical and prehistorical times deduced from varved lake sediments: Calibration of records from Lakes Woseriner See and Tiefer See

    NASA Astrophysics Data System (ADS)

    Czymzik, Markus; Kienel, Ulrike; Dreibrodt, Stefan; Brauer, Achim

    2013-04-01

    Societies are susceptible to the effects of even short-term climate variations on water supply, health, and agricultural productivity. However, understanding of human-climate interactions is limited due to the lack of high-resolution climate records in space and time. Varved lake sediments provide long time-series of seasonal climate variability directly from populated areas that can be compared to historical and archeological records. Calibration against meteorological data enables process-based insights into sediment deposition within the lake that can be extrapolated into the past using transfer functions. Lakes Woseriner See (53°40'N/12°2'E; 37 m asl.) and Tiefer See (53°23'N/13°97'E, 65 m asl.) in northeastern Germany are located only 35 km apart. Situated within the former settlement areas, the lakes are well suited for studying climate influences on society related to the Neolithic Funnelbeaker culture or the Slavic colonization. Sub-recent annual laminations allow to establish climate proxy data-series at seasonal resolution that can be calibrated against the long meteorological record from the nearby City of Schwerin. Seasonal climate proxy data-series covering the last 90 years have been obtained from short sediment cores applying a combination of microfacies analyses, X-ray fluorescence scanning (µ-XRF), and varve counting. Main sediment microfacies in both lakes are endogenic calcite varves comprising calcite and organic layer couplets of varying thickness, diatom layers, and dispersed detrital grains. Calibration against meteorological data indicates that variations in sediment layer thickness and composition are not stationary through time but influenced by inter-annual variations in meteorological conditions.

  6. Climate variability during the deglaciation and Holocene in a high-altitude alpine lake deduced from the sedimentary record from Laguna Seca, Sierra Nevada, southern Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Camuera, Jon; Jiménez-Moreno, Gonzalo; José Ramos-Román, María; García-Alix, Antonio; Jiménez-Espejo, Francisco; Anderson, R. Scott

    2017-04-01

    High-resolution X-ray fluorescence (XRF), magnetic susceptibility (MS), color and lithological analyses have been carried out on a 3.6 m-long sediment core from Laguna Seca, a high-elevation dry lake from Sierra Nevada mountain range, southern Spain. This is the longest sedimentary record retrieved from an alpine lake in southern Iberian Peninsula. Besides, alpine lakes are very sensitive environments to climate changes and previous studies showed that Laguna Seca could provide an excellent record to identify millennial-scale climate variations during deglaciation and the whole Holocene. XRF analyses, in particular high calcium and low K/Ca ratios, show aridity phases, very well represented during Last Glacial Maximum (LGM) and the Younger Dryas (YD). Arid events are also shown at ca. 8.1 ka BP, ca. 4.4 ka BP and the latest Holocene. On the other hand, negative values in calcium and positive values in K/Ca appear in the Bølling-Allerød (BA) and during the early Holocene until ca. 6 ka BP, indicating more humidity and higher run-off. A progressive aridification trend is also observed in the Holocene, changing from more humid conditions during the early Holocene to more aridity during the late Holocene.

  7. Climate change deduced from isotopes in tree rings

    SciTech Connect

    Pendall, E.G.; Leavitt, S.W.

    1997-11-01

    This paper describes the theory of carbon, hydrogen, and oxygen isotopic signatures in cellulose for the purpose of paleoclimatic reconstruction. Mechanisms governing tree ring cellulose isotopic variability are investigated, and applications to the southwestern United States are delineated. A monitoring program of pinyon trees and comparison to climatic parameters is briefly described. Variables measured included deviations in hydrogen and oxygen-18 isotopic composition in precipitation, soil water, stem and leaf water, and atmospheric vapor. Water from phloem tissue was found to be isotopically identical to the xylem sap, suggesting that cellulose precursors can exchange isotopically with source water before cellulose is made in the trunk, thus removing most of the isotopic signal from the leaves. Overall results suggest that, on arid sites in the southwestern US receiving adequate summer rain, a precipitation seasonality signal may be recorded. 21 refs., 2 figs.

  8. Corals as climate recorders

    USGS Publications Warehouse

    Flannery, Jennifer A.; Poore, Richard Z.

    2010-01-01

    The U.S. Geological Survey (USGS) Coral Reef Ecosystem Studies (CREST) Project is analyzing corals from various sites in the Caribbean region, Dry Tortugas National Park, Biscayne National Park, other areas of the Florida Keys, and the Virgin Islands. The objective of this project is to develop records of past environmental change to better our understanding of climate variability. The records are being used to document changes over the last few centuries and to determine how corals and coral reefs have responded to any changes.

  9. Precipitation Climate Data Records

    NASA Astrophysics Data System (ADS)

    Nelson, B. R.; Prat, O.; Vasquez, L.

    2015-12-01

    Five precipitation CDRs are now or soon will be transitioned to NOAA's CDR program. These include the PERSIANN data set, which is a 30-year record of daily adjusted global precipitation based on retrievals from satellite microwave data using artificial neural networks. The AMSU-A/B/Hydrobundle is an 11-year record of precipitable water, cloud water, ice water, and other variables. CMORPH (the NOAA Climate Prediction Center Morphing Technique) is a 17-year record of daily and sub-daily adjusted global precipitation measured from passive microwave and infrared data at high spatial and temporal resolution. GPCP (the Global Precipitation Climatology Project) is an approximately 30-year record of monthly and pentad adjusted global precipitation and a 17-year record of daily adjusted global precipitation. The NEXRAD Reanalysis is a 10-year record of high resolution NEXRAD radar based adjusted CONUS-wide hourly and daily precipitation. This study provides an assessment of the existing and transitioned long term precipitation CDRs and includes the verification of the five precipitation CDRs using various methods including comparison with in-situ data sets and trend analysis. As all of the precipitation related CDRs are transitioned, long term analyses can be performed. Comparisons at varying scales (hourly, daily and longer) of the precipitation CDRs with in-situ data sets are provided as well as a first look at what could be an ensemble long term precipitation data record.

  10. 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

  11. 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

  12. A Record of Climate Change

    ERIC Educational Resources Information Center

    Smith, Zach

    2007-01-01

    The hydrologic cycle is a very basic scientific principle. In this article, background information is presented on how the hydrologic cycle provides scientists with clues to understanding the history of Earth's climate. Also detailed is a web-based activity that allows students to learn about how scientists are able to piece together a record of…

  13. A Record of Climate Change

    ERIC Educational Resources Information Center

    Smith, Zach

    2007-01-01

    The hydrologic cycle is a very basic scientific principle. In this article, background information is presented on how the hydrologic cycle provides scientists with clues to understanding the history of Earth's climate. Also detailed is a web-based activity that allows students to learn about how scientists are able to piece together a record of…

  14. Submarine paleoseismology of the northern Hikurangi subduction margin of New Zealand as deduced from Turbidite record since 16 ka

    NASA Astrophysics Data System (ADS)

    Pouderoux, Hugo; Proust, Jean-Noël; Lamarche, Geoffroy

    2014-01-01

    Paleoseismic studies seek to characterise the signature of pre-historical earthquakes by deriving quantitative information from the geological record such as the source, magnitude and recurrence of moderate to large earthquakes. In this study, we provide a ˜16,000 yr-long paleo-earthquake record of the 200 km-long northern Hikurangi Margin, New Zealand, using cm-thick deep-sea turbidites identified in sediment cores. Cores were collected in strategic locations across the margin within three distinct morphological re-entrants - the Poverty, Ruatoria and Matakaoa re-entrants. The turbidite facies vary from muddy to sandy with evidence for rare hyperpycnites interbedded with hemipelagites and tephra. We use the Oxal probabilistic software to model the age of each turbidite, using the sedimentation rate of hemipelagite deduced from well-dated tephra layers and radiocarbon ages measurements on planktonic foraminifera.

  15. Climate stability as deduced from an idealized coupled atmosphere-ocean model

    SciTech Connect

    Tang, B.; Weaver, A.J.

    1995-04-01

    The stability of an idealized climate system is investigated using a simple coupled atmosphere-ocean box model. Motivated by the results from general circulation models. the main physical constraint imposed on the system is that the net radiation at the top of the atmosphere is fixed. The specification of an invariant equatorial atmospheric temperature. Consistent with paleoclimatic data, allows the hydrological cycle to be internally determined from the poleward heat transport budget, resulting in a model that has a plausible representation of the hydrological cycle-thermohaline circulation interaction. The model suggests that the stability and variability of the climate system depends fundamentally on the mean climatic state (total heat content of the system). When the total heat content of the climate system is low, a stable present-day equilibrium exists with high-latitude sinking. Conversely, when the total heat content is high, a stable equatorial sinking equilibrium exists. For a range of intermediate values of the total heat content, internal climatic oscillations can occur through a hydrological cycle-thermohaline circulation feedback process. Experiments conducted with the model reveal that under a 100-year 2xCO{sub 2} warming, the thermohaline circulation first collapses but then recovers. Under a 100-year 4 x CO{sub 2} warming, the thermohaline circulation collapses and remains collapsed. Recent paleoclimatic data suggest that the climate system may behave very differently for warmer climate. Our results suggest that this may be attributed to the enhanced poleward freshwater transport, which causes increased instability of the present-day thermohaline circulation. 50 refs., 4 figs., 1 tab.

  16. Petrographically deduced triassic climate for the Deep River Basin, eastern piedmont of North Carolina

    SciTech Connect

    McCarn, S.T.; Mansfield, C.F.

    1985-01-01

    A petrographic comparison of Triassic, fluvial sandstones from the Deep River Basin in the eastern piedmont of North Carolina with nearby Holocene stream sands (1) indicates that he Triassic climate was more arid than today's and (2) distinguishes an eastern, more plutonic terrane from a western, more metamorphic source terrane. The paleoclimatic interpretation is based on differences in framework composition between modern and ancient sands of the same grain size, derived from the same rock type, transported similar distances and deposited in similar settings. The Triassic sandstones contain more lithic-fragments but less quartz than otherwise equivalent, modern sand in the Deep River Basin. Feldspar content is more complex, controlled by both source-rock composition and climate. Sand from the more plutonic terrane contains more feldspar and plutonic lithic-fragments than sand from the more metamorphic terrane, which contains more quartz and metamorphic lithic-fragments. This petrographic interpretation of the Triassic sandstones along with the presence of coal, limestone, chert and caliche in the middle of the section suggests that the Triassic climate was cyclic, changing from arid to humid and back to arid. Plate-tectonic reconstructions place the Deep River Basin between the Triassic equator and Tropic of cancer, where the easterly trade winds would predominate. Therefore, the arid portions of the cycle could have been due to a periodic, orographic, rain shadow formed as the result of intermittent movement along the Jonesboro Fault, creating a highland area east of the Deep River Basin.

  17. Atmospheric carbon dioxide and the climate record

    SciTech Connect

    Ellsaesser, H.W.

    1989-04-01

    This paper is an attempt to provide a summary review of conclusions from previous studies on this subject. Subject headings include: conceptualization of the greenhouse effect, the climatic effect of doubled CO/sub 2/, interpretation of the climatic record, diagnosis of apparent and possible model deficiencies, and the palaeoclimatic record.

  18. Landsat Surface Reflectance Climate Data Records

    USGS Publications Warehouse

    ,

    2014-01-01

    Landsat Surface Reflectance Climate Data Records (CDRs) are high level Landsat data products that support land surface change studies. Climate Data Records, as defined by the National Research Council, are a time series of measurements with sufficient length, consistency, and continuity to identify climate variability and change. The U.S. Geological Survey (USGS) is using the valuable 40-year Landsat archive to create CDRs that can be used to document changes to Earth’s terrestrial environment.

  19. Multi-scale Holocene Asian monsoon variability deduced from a twin-stalagmite record in southwestern China

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Wang, Yongjin; Cheng, Hai; Edwards, Richard Lawrence; Shen, Chuan-Chou; Liu, Dianbing; Shao, Qingfeng; Deng, Chao; Zhang, Zhenqiu; Wang, Quan

    2016-07-01

    We present two isotopic (δ18O and δ13C) sequences of a twin-stalagmite from Zhuliuping Cave, southwestern China, with 230Th dates from 14.6 to 4.6 ka. The stalagmite δ18O record characterizes orbital- to decadal-scale variability of Asian summer monsoon (ASM) intensity, with the Holocene optimum period (HOP) between 9.8 and 6.8 ka BP which is reinforced by its co-varying δ13C data. The large multi-decadal scale amplitude of the cave δ18O indicates its high sensitivity to climate change. Four centennial-scale weak ASM events during the early Holocene are centered at 11.2, 10.8, 9.1 and 8.2 ka. They can be correlated to cold periods in the northern high latitudes, possibly resulting from rapid dynamics of atmospheric circulation associated with North Atlantic cooling. The 8.2 ka event has an amplitude more than two-thirds that of the Younger Dryas (YD), and is significantly stronger than other cave records in the Asia monsoon region, likely indicating a more severe dry climate condition at the cave site. At the end of the YD event, the δ13C record lags the δ18O record by 300-500 yr, suggesting a multi-centennial slow response of vegetation and soil processes to monsoon enhancement.

  20. Changing seasonality patterns in Central Europe from Miocene Climate Optimum to Miocene Climate Transition deduced from the Crassostrea isotope archive

    NASA Astrophysics Data System (ADS)

    Harzhauser, Mathias; Piller, Werner E.; Müllegger, Stefan; Grunert, Patrick; Micheels, Arne

    2011-03-01

    The Western Tethyan estuarine oyster Crassostrea gryphoides is an excellent climate archive due to its large size and rapid growth. It is geologically long lived and allows a stable isotope-based insight into climatic trends during the Miocene. Herein we utilised the climate archive of 5 oyster shells from the Miocene Climate Optimum (MCO) and the subsequent Miocene Climate Transition (MCT) to evaluate changes of seasonality patterns. MCO shells exhibit highly regular seasonal rhythms of warm-wet and dry-cool seasons. Optimal conditions resulted in extraordinary growth rates of the oysters. δ 13C profiles are in phase with δ 18O although phytoplankton blooms may cause a slight offset. Estuarine waters during the MCO in Central Europe display a seasonal temperature range of c. 9-10 °C. Absolute water temperatures have ranged from 17 to 19 °C during cool seasons and up to 28 °C in warm seasons. Already during the early phase of the MCO, the growth rates are distinctly declining, although gigantic and extremely old shells have been formed at that time. Still, a very regular and well expressed seasonality is dominating the isotope profiles, but episodically occurring extreme climate events influence the environments. The seasonal temperature range is still c. 9 °C but the cool season temperature seems to be slightly lower (16 °C) and the warm season water temperature does not exceed c. 25 °C. In the later MCT at c. 12.5-12.0 Ma the seasonality pattern is breaking down and is replaced by successions of dry years with irregular precipitation events. No correlation between δ 18O and δ 13C is documented maybe due to a suboptimal nutrition level which would explain the low growth rates and small sizes. The amplitude of seasonal temperature range is decreasing to 5-8 °C. No clear cooling trend can be postulated for that time as the winter season water temperatures range from 15 to 20 °C. This may point to unstable precipitation rhythms on a multi-annual to

  1. Inferring climate variability from skewed proxy records

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Tingley, M.

    2013-12-01

    Many paleoclimate analyses assume a linear relationship between the proxy and the target climate variable, and that both the climate quantity and the errors follow normal distributions. An ever-increasing number of proxy records, however, are better modeled using distributions that are heavy-tailed, skewed, or otherwise non-normal, on account of the proxies reflecting non-normally distributed climate variables, or having non-linear relationships with a normally distributed climate variable. The analysis of such proxies requires a different set of tools, and this work serves as a cautionary tale on the danger of making conclusions about the underlying climate from applications of classic statistical procedures to heavily skewed proxy records. Inspired by runoff proxies, we consider an idealized proxy characterized by a nonlinear, thresholded relationship with climate, and describe three approaches to using such a record to infer past climate: (i) applying standard methods commonly used in the paleoclimate literature, without considering the non-linearities inherent to the proxy record; (ii) applying a power transform prior to using these standard methods; (iii) constructing a Bayesian model to invert the mechanistic relationship between the climate and the proxy. We find that neglecting the skewness in the proxy leads to erroneous conclusions and often exaggerates changes in climate variability between different time intervals. In contrast, an explicit treatment of the skewness, using either power transforms or a Bayesian inversion of the mechanistic model for the proxy, yields significantly better estimates of past climate variations. We apply these insights in two paleoclimate settings: (1) a classical sedimentary record from Laguna Pallcacocha, Ecuador (Moy et al., 2002). Our results agree with the qualitative aspects of previous analyses of this record, but quantitative departures are evident and hold implications for how such records are interpreted, and

  2. A Solar Irradiance Climate Data Record

    NASA Astrophysics Data System (ADS)

    Coddington, O.; Lean, J. L.; Pilewskie, P.; Snow, M.; Lindholm, D.

    2016-08-01

    We present a new climate data record for total solar irradiance and solar spectral irradiance between 1610 and the present day with associated wavelength and time-dependent uncertainties and quarterly updates. The data record, which is part of the National Oceanic and Atmospheric Administration’s (NOAA) Climate Data Record (CDR) program, provides a robust, sustainable, and scientifically defensible record of solar irradiance that is of sufficient length, consistency, and continuity for use in studies of climate variability and climate change on multiple time scales and for user groups spanning climate modeling, remote sensing, and natural resource and renewable energy industries. The data record, jointly developed by the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP) and the Naval Research Laboratory (NRL), is constructed from solar irradiance models that determine the changes with respect to quiet sun conditions when facular brightening and sunspot darkening features are present on the solar disk where the magnitude of the changes in irradiance are determined from the linear regression of a proxy magnesium (Mg) II index and sunspot area indices against the approximately decade-long solar irradiance measurements of the Solar Radiation and Climate Experiment (SORCE). To promote long-term data usage and sharing for a broad range of users, the source code, the dataset itself, and supporting documentation are archived at NOAA's National Centers for Environmental Information (NCEI). In the future, the dataset will also be available through the LASP Interactive Solar Irradiance Data Center (LISIRD) for user-specified time periods and spectral ranges of interest.

  3. NOAA's Portfolio of Operational Climate Data Records

    NASA Astrophysics Data System (ADS)

    Newport, B. J.; Cecil, D.; Hutchins, C.; Preston, C.; Stachniewicz, J. S.; Wunder, D.

    2015-12-01

    NOAA's Climate Data Record (CDR) Program was established by the National Centers for Environmental Information (NCEI) (formerly the National Climatic Data Center) in order to develop and implement a robust, sustainable, and scientifically defensible approach to producing and preserving climate records from satellite data. Since its inception in 2009 the CDR Program has transitioned 30 CDRs developed by various research groups to an initial operational state at NCEI. As a result of this transition the CDR dataset, metadata, documentation, and source code are archived by NCEI and accessible to the public, and most of the datasets are being extended by the Principal Investigator with CDR Program support. Consistency is maintained by using a formal change control process, with reprocessing and re-archiving as needed. The current portfolio of operational CDRs includes 15 Atmospheric CDRs, four Oceanic CDRs, four Terrestrial CDRs, and seven Fundamental CDRs. The main features of the portfolio will be presented, along with some potential and emerging uses.

  4. Modern climate challenges and the geological record

    USGS Publications Warehouse

    Cronin, Thomas M.

    2010-01-01

    Today's changing climate poses challenges about the influence of human activity, such as greenhouse gas emissions and land use changes, the natural variability of Earth's climate, and complex feedback processes. Ice core and instrumental records show that over the last century, atmospheric carbon dioxide (CO2) concentrations have risen to 390 parts per million volume (ppmv), about 40% above pre-Industrial Age concentrations of 280 ppmv and nearly twice those of the last glacial maximum about 22,000 years ago. Similar historical increases are recorded in atmospheric methane (CH4) and nitrous oxide (N2O). There is general agreement that human activity is largely responsible for these trends. Substantial evidence also suggests that elevated greenhouse gas concentrations are responsible for much of the recent atmospheric and oceanic warming, rising sea level, declining Arctic sea-ice cover, retreating glaciers and small ice caps, decreased mass balance of the Greenland and parts of the Antarctic ice sheets, and decreasing ocean pH (ocean "acidification"). Elevated CO2 concentrations raise concern not only from observations of the climate system, but because feedbacks associated with reduced reflectivity from in land and sea ice, sea level, and land vegetation relatively slowly (centuries or longer) to elevated 2 levels. This means that additional human-induced climate change is expected even if the rate of CO2 emissions is reduced or concentrations immediately stabilized.

  5. Sustained Satellite Missions for Climate Data Records

    NASA Astrophysics Data System (ADS)

    Halpern, David

    2012-07-01

    Global change is a daunting grand challenge and provides great opportunities in science, technology, and management. Observations are a key to understanding global change. Climate change knowledge will be limited without sustainable, high accuracy, well-calibrated, long-period observations with adequate spatial and temporal resolutions for regional applications. Operational or continuous measurements recorded for predictions of weather-to-climate events, such as hurricanes, El Nino, and sea level rise, are critically important for advancing the science of global change. Examples of global observations are sea surface temperature, sea level, and sea ice. This talk will review progress in transitioning previous observations recorded for high signal-to-noise weather events to data sets for low signal-to-noise climate events. In addition, the talk will describe managerial advances for sustaining research-type observations by operational systems. GEOSS is an important instrument to improve integration of long-term global observations carried out by operational agencies and limited-duration observations recorded by research agencies.

  6. Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall

    NASA Astrophysics Data System (ADS)

    Enzel, Yehouda; Bookman (Ken Tor), Revital; Sharon, David; Gvirtzman, Haim; Dayan, Uri; Ziv, Baruch; Stein, Mordechai

    2003-11-01

    The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr -1 average isohyet during 1940-1990 are largely synchronous and in phase (˜70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between

  7. The fluvial record of climate change.

    PubMed

    Macklin, M G; Lewin, J; Woodward, J C

    2012-05-13

    Fluvial landforms and sediments can be used to reconstruct past hydrological conditions over different time scales once allowance has been made for tectonic, base-level and human complications. Field stratigraphic evidence is explored here at three time scales: the later Pleistocene, the Holocene, and the historical and instrumental period. New data from a range of field studies demonstrate that Croll-Milankovitch forcing, Dansgaard-Oeschger and Heinrich events, enhanced monsoon circulation, millennial- to centennial-scale climate variability within the Holocene (probably associated with solar forcing and deep ocean circulation) and flood-event variability in recent centuries can all be discerned in the fluvial record. Although very significant advances have been made in river system and climate change research in recent years, the potential of fluvial palaeohydrology has yet to be fully realized, to the detriment of climatology, public health, resource management and river engineering.

  8. Glacial records of global climate: A 1500-year tropical ice core record of climate

    SciTech Connect

    Thompson, L.G.; Davis, M.E.; Mosley-Thompson, E. )

    1994-03-01

    A general discussion is given of climate variability over the last 1500 years as interpreted from two ice cores from the Quelccaya ice cap, Peru. The possible role of climatic variability in prehistory over this period is discussed with emphases on (1) relationships between climate and the rise and decline of coastal and highland cultures; (2) the possible causes of two major dust events recorded in the quelccaya ice cores around AD 920 and AD 600; (3) implications of climatic variation for the occupation and abandonment of the Gran Pajaten area. The remarkable similarity between changes in highland and coastal cultures and changes in accumulation as determined from the Quelccaya ice cores implies a strong connection between human activities and climate in this region of the globe. Two ice cores drilled to bedrock from the 6047 masl col of Huascaran in the Cordillera Blanca, Peru in 1993 offer the potential of an annual to decadal climatic and environmental record which should allow the study of human-climate and human-environmental relationships over 10,000+ years. The 1991 and 1993 evidence from the Quelccaya ice cap indicates that recent and rapid warming is currently underway in the tropical Andes. Thus, many of the unique glacier archives are in imminent danger of being lost forever.

  9. 2016 Climate Trends Continue to Break Records

    NASA Image and Video Library

    2017-09-28

    Two key climate change indicators -- global surface temperatures and Arctic sea ice extent -- have broken numerous records through the first half of 2016, according to NASA analyses of ground-based observations and satellite data. Each of the first six months of 2016 set a record as the warmest respective month globally in the modern temperature record, which dates to 1880, according to scientists at NASA's Goddard Institute for Space Studies (GISS) in New York. The six-month period from January to June was also the planet's warmest half-year on record, with an average temperature 1.3 degrees Celsius (2.4 degrees Fahrenheit) warmer than the late nineteenth century. Read more: go.nasa.gov/29SQngq Credit: NASA/Goddard NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  10. Early to Middle Pleistocene Climate Records off Southern Iberia Reveal two Types of Interglacial Climate Evolution

    NASA Astrophysics Data System (ADS)

    Voelker, Antje; Rodrigues, Teresa; Padilha, Maria; Jimenez-Espejo, Francisco J.; Salgueiro, Emilia; Kuhnert, Henning

    2017-04-01

    The Gulf of Cadiz off southern Iberia is an ideal place to study the interaction between North Atlantic and Mediterranean Sea climate variations with surface waters reflecting subtropical gyre conditions and the intermediate-depth Mediterranean Outflow Water (MOW) combining Mediterranean Sea and North Atlantic signals. Using centennial-scale records from IODP Site U1387 (36.8°N, 7.7°W; 559 m w.d.) we evaluate interglacial surface-water and MOW conditions during the interval from Marine Isotope Stage (MIS) 16 to 48 (630-1470 ka). Surface-water changes are deduced from alkenone-derived sea-surface temperature (SST) and G. bulloides stable isotope records and MOW conditions from the benthic foraminifer stable isotope data and the wt% sand. The surface water records clearly allow distinguishing two groups of interglacial climate evolution that can be defined by the shape of the deglaciation and the timing of the interglacial SST maximum. An abrupt glacial/interglacial transition and maximum SST at the beginning of the respective interglacial period are recorded for MIS 17 to MIS 27 and for MIS 47, whereas MIS 29 to MIS 45 exhibit a more gradual transition and a SST maximum later on during the interglacial period. The change in interglacial climate evolution roughly coincides with the Mid-Pleistocene Transition, during which the step to a higher, glacial ice-volume occurred in MIS 22. The shift to cooler interglacial SST occurred already earlier, i.e. between MIS 31 and MIS 29. MIS 29 and younger interglacials experienced SSTs around 22°C (exception is MIS 23 with 19.5°C), whereas MIS 31 and older show values of 23-23.5°C, even reaching 24.5-25°C during MIS 37 and MIS 41. All glacial periods experienced millennial-scale oscillations and extreme cold events during glacial periods happened throughout the record. In contrast, the interglacial MOW shows no major shifts at either MIS 25 or MIS 31. Interglacial MOW conditions are strongly linked to the insolation maxima

  11. Climate records recovering the last deglaciation

    SciTech Connect

    Sowers, T.; Bender, M.

    1995-07-14

    The oxygen-18/oxygen-16 ratio of molecular oxygen trapped in ice cores provides a time-stratigraphic marker for transferring the absolute chronology for the Greenland Ice Sheet Project (GISP)II ice core to the Vostok and Byrd ice cores in Antarctica. Comparison of the climate records from these cores suggests that, near the beginning of the last deglaciation, warming in Antarctica began approximately 3000 years before the onset of the warm Bolling period in Greenland. Atmospheric carbon dioxide and methane concentrations began to rise 2000 to 3000 years before the warming began in Greenland and must have contributed to deglaciation and warming of temperate and boreal regions in the Northern Hemisphere. 60 refs., 3 figs.

  12. Early to Middle Pleistocene Climate Records off Southern Iberia Reveal two Types of Interglacial Climate Evolution

    NASA Astrophysics Data System (ADS)

    Voelker, A. H. L.; Rodrigues, T.; Padilha, M.; Jiménez-Espejo, F. J. J.; Salgueiro, E.; Kuhnert, H.

    2016-12-01

    The Gulf of Cadiz off southern Iberia is an ideal place to study the interaction between North Atlantic and Mediterranean Sea climate variations with surface waters reflecting subtropical gyre conditions and the intermediate-depth Mediterranean Outflow Water (MOW) combining Mediterranean Sea and North Atlantic signals. Using centennial-scale records from IODP Site U1387 (36.8°N, 7.7°W; 559 m w.d.) we evaluate interglacial surface-water and MOW conditions during the interval from Marine Isotope Stage (MIS) 16 to 46 (630-1430 ka). Surface-water changes are deduced from alkenone-derived sea-surface temperature (SST) and G. bulloides stable isotope records and MOW conditions from the benthic foraminifer stable isotope data and the wt% sand. The surface water records clearly allow distinguishing two groups of interglacial climate evolution that can be defined by the shape of the deglaciation and the timing of the interglacial SST maximum. An abrupt glacial/interglacial transition and maximum SST at the beginning of the respective interglacial period are recorded for MIS 17 to MIS 23, whereas MIS 25 to MIS 45 exhibit a more gradual transition and a SST maximum later on during the interglacial period. This change in interglacial climate evolution coincides with the frequently observed, Mid-Pleistocene Transition related shift between MIS 24 and 22. The shift to cooler interglacial SST, however, occurred already earlier, between MIS 31 and MIS 29. MIS 29 and younger experienced interglacial SSTs around 22°C (exception is MIS 23 with 19.5°C), whereas MIS 31 and older show values of 23-23.5°C, even reaching 24.5-25°C during MIS 37 and MIS 41. In contrast, the interglacial MOW shows no major shifts at either MIS 25 or MIS 31. Interglacial MOW conditions are strongly linked to the insolation maxima and the related, African monsoon induced changes in Mediterranean Sea hydrology (e.g., sapropel formation). Thus, the interglacial MOW is a poorly ventilated, sluggish current

  13. Climatic Teleconnections Recorded By Tropical Mountain Glaciers

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Permana, D.; Mosley-Thompson, E.; Davis, M. E.

    2014-12-01

    Information from ice cores from the world's highest mountains in the Tropics demonstrates both local climate variability and a high degree of teleconnectivity across the Pacific basin. Here we examine recently recovered ice core records from glaciers near Puncak Jaya in Papua, Indonesia, which lie on the highest peak between the Himalayas and the South American Andes. These glaciers are located on the western side of the Tropical Pacific warm pool, which is the "center of action" for interannual climate variability dominated by El Niño-Southern Oscillation (ENSO). ENSO either directly or indirectly affects most regions of Earth and their populations. In 2010, two ice cores measuring 32.13 m and 31.25 m were recovered to bedrock from the East Northwall Firn ice field. Both have been analyzed in high resolution (~3 cm sample length, 1156 and 1606 samples, respectively) for stable isotopes, dust, major ions and tritium concentrations. To better understand the controls on the oxygen isotopic (δ18 O) signal for this region, daily rainfall samples were collected between January 2013 and February 2014 at five weather stations over a distance of ~90 km ranging from 9 meters above sea level (masl) on the southern coast up to 3945 masl. The calculated isotopic lapse rate for this region is 0.24 ‰/100m. Papua, Indonesian ice core records are compared to ice core records from Dasuopu Glacier in the central Himalayas and from Quelccaya, Huascarán, Hualcán and Coropuna ice fields in the tropical Andes of Peru on the eastern side of the Pacific Ocean. The composite of the annual isotopic time series from these cores is significantly (R2 =0.53) related to tropical Pacific sea surface temperatures (SSTs), reflecting the strong linkage between tropical Pacific SSTs associated with ENSO and tropospheric temperatures in the low latitudes. New data on the already well-documented concomitant loss of ice on Quelccaya, Kilimanjaro in eastern Africa and the ice fields near Puncak

  14. NOAA Climate Data Records Access for Applications

    NASA Astrophysics Data System (ADS)

    Stachniewicz, J. S.; Cecil, D.; Hollingshead, A.; Newport, B. J.; Wunder, D.

    2015-12-01

    There are many potential uses of NOAA Climate Data Records (CDRs) for decision-making and catastrophic risk management assessment activities in the federal, state, and local government and private sectors, in addition to their traditional uses by the academic/scientific community. There is growing interest in using NOAA CDRs for such applications and straightforward access to the data is essential if these applications are to be successful. User engagement activities determine the types of data that users need, as well as the spatial and temporal subsets. This talk will present the access methods currently available and in development. Alternate representations and sources of some CDRs will also be discussed. Recent improvements include: 1. CDR information web page 2. Dataset types, sizes, growth, latency, grid/swath 3. Dataset discovery, data access, and sub-setting. 4. Knowing our users and their needs. 5. Known uses of some CDRs. 6. Migration to CLASS. 7. Other representations - GeoTIFF, Obs4MIPS 8. Cloud applications - Google, Microsoft

  15. Sustained production of multi-decadal climate records - Lessons from the NOAA Climate Data Record Program

    NASA Astrophysics Data System (ADS)

    Bates, J. J.

    2015-12-01

    NOAA's Climate Data Record (CDR) Program was designed to be responsive to the needs of climate monitoring, research, and services with the ultimate aim of serving decision making across a spectrum of users for the long term. It requires the sustained production of high quality, multidecadal time series data describing the global atmosphere, oceans, and land surface that can be used for informed decision making. The challenges of a long-term program of sustaining CDRs, as contrasted with short-term efforts of traditional three-year research programs, are substantial and different. The sustained production of CDRs requires collaboration between experts in the climate community, data management, and software development and maintenance. It is also informed by scientific application and associated user feedback on the accessibility and usability of the produced CDRs. The CDR Program has developed a metric for assessing the maturity of CDRs with respect to data management, software, and user application and applied it to over 28 CDRs. The main/primary lesson learned over the past seven years is that a rigorous, team approach to data management, employing subject matter experts at every step, is critical to open and transparent production. This approach also makes it much easier to support the needs of users who want near-real-time production of "interim" CDRs for monitoring and users who want to use CDRs for tailored authoritative information, such as a drought index. This talk will review of the history of the CDR program, current status, and plans.

  16. Sustained Satellite Missions for Climate Data Records

    NASA Technical Reports Server (NTRS)

    Halpern, David

    2012-01-01

    Satellite CDRs possess the accuracy, longevity, and stability for sustained moni toring of critical variables to enhance understanding of the global integrated Earth system and predict future conditions. center dot Satellite CDRs are a critical element of a global climate observing system. center dot Satellite CDRs are a difficult challenge and require high - level managerial commitment, extensive intellectual capital, and adequate funding.

  17. Sustained Satellite Missions for Climate Data Records

    NASA Technical Reports Server (NTRS)

    Halpern, David

    2012-01-01

    Satellite CDRs possess the accuracy, longevity, and stability for sustained moni toring of critical variables to enhance understanding of the global integrated Earth system and predict future conditions. center dot Satellite CDRs are a critical element of a global climate observing system. center dot Satellite CDRs are a difficult challenge and require high - level managerial commitment, extensive intellectual capital, and adequate funding.

  18. The geologic record of climatic change

    NASA Technical Reports Server (NTRS)

    Crowley, T. J.

    1982-01-01

    Major results from paleoclimatic investigations are investigated, and background material is included. The time interval surveyed extends from the formation of the Earth 4.6 billion years ago to the development of the instrumental record.

  19. Untangling climatic and autogenic signals in peat records

    NASA Astrophysics Data System (ADS)

    Morris, Paul J.; Baird, Andrew J.; Young, Dylan M.; Swindles, Graeme T.

    2016-04-01

    Raised bogs contain potentially valuable information about Holocene climate change. However, autogenic processes may disconnect peatland hydrological behaviour from climate, and overwrite and degrade climatic signals in peat records. How can genuine climate signals be separated from autogenic changes? What level of detail of climatic information should we expect to be able to recover from peat-based reconstructions? We used an updated version of the DigiBog model to simulate peatland development and response to reconstructed Holocene rainfall and temperature reconstructions. The model represents key processes that are influential in peatland development and climate signal preservation, and includes a network of feedbacks between peat accumulation, decomposition, hydraulic structure and hydrological processes. It also incorporates the effects of temperature upon evapotranspiration, plant (litter) productivity and peat decomposition. Negative feedbacks in the model cause simulated water-table depths and peat humification records to exhibit homeostatic recovery from prescribed changes in rainfall, chiefly through changes in drainage. However, the simulated bogs show less resilience to changes in temperature, which cause lasting alterations to peatland structure and function and may therefore be more readily detectable in peat records. The network of feedbacks represented in DigiBog also provide both high- and low-pass filters for climatic information, meaning that the fidelity with which climate signals are preserved in simulated peatlands is determined by both the magnitude and the rate of climate change. Large-magnitude climatic events of an intermediate frequency (i.e., multi-decadal to centennial) are best preserved in the simulated bogs. We found that simulated humification records are further degraded by a phenomenon known as secondary decomposition. Decomposition signals are consistently offset from the climatic events that generate them, and decomposition

  20. The paleoclimate record of long-term climate variability

    SciTech Connect

    Webb, R.S.; Bartlein, P.J.; Overpeck, J.T. Univ. of Oregon, Eugene )

    1993-06-01

    Climate variability occurs on time scales ranging from decades or shorter to millions of years. An important step in determining the effects of trace-gas-induced warming on climate variability and ecosystems is characterizing past natural variability and change. Throughout the Quaternary long-term climate variability has been dominated by Milankovitch forcing of glacial/interglacial cycles. Superimposed on this millennia-scale orbitally forced variability have been more rapid climate events (e.g. Younger Dryas, Little Ice Age, Medieval Warm Period, Sahelian droughts). Although highly relevant to understanding possible responses of ecosystems to future climate change, most decade to century scale climate variability remains poorly understood. Insights into mechanisms and responses can be obtained from tree rings, ice cores, corals, marine, lake and fluvial sediments, pollen, and macrofossils. These paleoclimate records reveal that the range of natural climate variability is much larger than indicated by the instrumental record of the past 150 years. Global networks of well-dated, high-resolution paleocrunate records for key intervals of the past are currently being assembled. These networks should provide the baseline of natural variability required to understand climate-ecosystem dynamics and to identify anthropogenic-induced change.

  1. The geologic record of climatic change

    NASA Technical Reports Server (NTRS)

    Crowley, T. J.

    1983-01-01

    Major results from paleoclimatic investigations are investigated, and background material is included. The time interval surveyed extends from the formation of the earth 4.6 billion years ago to the development of the instrumental record. Previously announced in STAR as N82-33946

  2. Interpretation of our present terrestrial climatic record

    SciTech Connect

    Ellsaesser, H.W.

    1987-09-01

    Detailed studies of profiles of delta/sup 18/O in oceanic and glacial cores and of pollen deposits in bogs indicate that the terrestrial climatic system, consisting of the atmosphere, hydrosphere, lithosphere and biosphere, is capable of oscillations with amplitudes, such as that of the Melisey II stadial of northern France, approaching or equaling that of the glacial-interglacial cycle but on time scales too short for the usually envisioned transfer of mass between the oceans and continental glaciers. Abrupt oscillations or shifts to new equilibrium are well documented in the Boelling-Aleroed warming and Younger Dryas readvance, the 0.4/sup 0/C rise in NH continental air temperature circa 1920 and the year-to-year oscillations in NH continental air temperatures from 1976 to 1984. Such abrupt oscillations defy explanation in terms of external forcing functions and suggest rather internal rearrangements within the climate system as the driving mechanism. Suggestions are made as to mechanisms for possible internal rearrangements which might lead to different hemispheric or global mean surface temperatures.

  3. Climatic change and permafrost. Record from surficial deposits

    USGS Publications Warehouse

    Carter, L. David

    1990-01-01

    The physical and chemical characteristics of surficial deposits and the floral and faunal remains they contain provide information that is useful for interpreting both paleoclimatic and past permafrost conditions. Surficial deposits thus provide a record of climatic change and permafrost history. This record suggests that initiation of permafrost in lowland areas of the Southern Arctic Archipelago and continents of the northern hemisphere may have occurred about 2,400,000 years ago during the pronounced cooling that led to the first major glaciation of late Cenozoic time. Since then, climate has been relatively cold but cyclically variable, characterized by the growth and shrinkage of large, continental ice sheets. Permafrost has expanded and contracted in response to these climatic changes, and we can expect the present permafrost conditions to change in response to future climatic changes. To predict the response of permafrost and the landscape to future climatic change we should: (1) Define relations between climate and the modern landscape; (2) establish long-term records of past climatic change and landscape response; and (3) determine the paleoenvironments of past warm periods as possible analogs for future global warming.

  4. Regional difference of the start time of the recent warming in Eastern China: prompted by a 165-year temperature record deduced from tree rings in the Dabie Mountains

    NASA Astrophysics Data System (ADS)

    Cai, Qiufang; Liu, Yu; Duan, Bingchuang; Sun, Changfeng

    2017-06-01

    Tree-ring studies from tropical to subtropical regions are rarer than that from extratropical regions, which greatly limit our understanding of some critical climate change issues. Based on the tree-ring-width chronology of samples collected from the Dabie Mountains, we reconstructed the April-June mean temperature for this region with an explained variance of 46.8%. Five cold (1861-1869, 1889-1899, 1913-1920, 1936-1942 and 1952-1990) and three warm (1870-1888, 1922-1934 and 2000-2005) periods were identified in the reconstruction. The reconstruction not only agreed well with the instrumental records in and around the study area, but also showed good resemblance to previous temperature reconstructions from nearby regions, indicating its spatial and temporal representativeness of the temperature variation in the central part of eastern China. Although no secular warming trend was found, the warming trend since 1970 was unambiguous in the Dabie Mountains (0.064 °C/year). Further temperature comparison indicated that the start time of the recent warming in eastern China was regional different. It delayed gradually from north to south, starting at least around 1940 AD in the north part, around 1970 AD in the central part and around 1980s in the south part. This work enriches the high-resolution temperature reconstructions in eastern China. We expect that climate warming in the future would promote the radial growth of alpine Pinus taiwanensis in the subtropical areas of China, therefore promote the carbon capture and carbon storage in the Pinus taiwanensis forest. It also helps to clarify the regional characteristic of recent warming in eastern China.

  5. NSIDC Contributions to Cryospheric Climate Data Records

    NASA Astrophysics Data System (ADS)

    Barry, R. G.; Armstrong, R. L.; Weaver, R. L.

    2008-12-01

    We assess NSIDC holdings as they relate to the development of consistent, calibrated time series - Earth Science Data Records for the cryosphere. Gaps in the documentation of the major cryospheric elements are identified in the Integrated Global Observing Strategy- Partnership (IGOS-P) cryosphere theme report. Filling these gaps will be a focus of the planned World Meteorological Organization's Global Cryosphere Watch (GCW). Snow cover extent from 1966 is the longest satellite record, and this data product is available from NSIDC as the Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 3. The main gap in snow cover data is the absence in freely accessible archives of station snow depths, especially for European countries.. There is no uniformly reliable data set of in situ snow water equivalent although since 1979 global products from passive microwave satellite data are available from NSIDC as the Global EASE-Grid Monthly Snow Water Equivalent Climatology Product . Corresponding data on global sea ice extent and concentration are also available from 1979 and most earlier operational chart products are accessible via the Global Digital Sea Ice Data Base at NSIDC. Snapshots of Arctic ice thickness exist from 1958 to present from submarine and moored upward-looking sonars, although not all of the Arctic Ocean is covered by these data. The World Glacier Inventory lists about 100,000 (two-thirds of all) glaciers but there are major gaps around Greenland and Antarctica, in the Himalayas and the United States. There are outlines (shapefiles and associated metadata) for over 65,000 glaciers in the NSIDC Global Land Ice Measurements from Space (GLIMS) data base and work is underway to complete these databases. However, there are globally only about 30 continuous mass balance records and larger glaciers are poorly represented. There are piecemeal records of lake and river ice in national archives but those available from NSIDC number 748 water

  6. Achieving Global Ocean Color Climate Data Records

    NASA Technical Reports Server (NTRS)

    Franz, Bryan

    2010-01-01

    Ocean color, or the spectral distribution of visible light upwelling from beneath the ocean surface, carries information on the composition and concentration of biological constituents within the water column. The CZCS mission in 1978 demonstrated that quantitative ocean color measurements could be. made from spaceborne sensors, given sufficient corrections for atmospheric effects and a rigorous calibration and validation program. The launch of SeaWiFS in 1997 represents the beginning of NASA's ongoing efforts to develop a continuous ocean color data record with sufficient coverage and fidelity for global change research. Achievements in establishing and maintaining the consistency of the time-series through multiple missions and varying instrument designs will be highlighted in this talk, including measurements from NASA'S MODIS instruments currently flying on the Terra and Aqua platforms, as well as the MERIS sensor flown by ESA and the OCM-2 sensor recently launched by ISRO.

  7. Climatic Changes on Tibetan Plateau Based on Ice Core Records

    NASA Astrophysics Data System (ADS)

    Yao, T.

    2008-12-01

    Climatic changes have been reconstructed for the Tibetan Plateau based on ice core records. The Guliya ice core on the Tibetan Plateau presents climatic changes in the past 100,000 years, thus is comparative with that from Vostok ice core in Antarctica and GISP2 record in Arctic. These three records share an important common feature, i.e., our climate is not stable. It is also evident that the major patterns of climatic changes are similar on the earth. Why does climatic change over the earth follow a same pattern? It might be attributed to solar radiation. We found that the cold periods correspond to low insolation periods, and warm periods to high insolation periods. We found abrupt climatic change in the ice core climatic records, which presented dramatic temperature variation of as much as 10 °C in 50 or 60 years. Our major challenge in the study of both climate and environment is that greenhouse gases such as CO2, CH4 are possibly amplifying global warming, though at what degree remains unclear. One of the ways to understand the role of greenhouse gases is to reconstruct the past greenhouse gases recorded in ice. In 1997, we drilled an ice core from 7100 m a.s.l. in the Himalayas to reconstruct methane record. Based on the record, we found seasonal cycles in methane variation. In particular, the methane concentration is high in summer, suggestiing active methane emission from wet land in summer. Based on the seasonal cycle, we can reconstruct the methane fluctuation history in the past 500 years. The most prominent feature of the methane record in the Himalayan ice core is the abrupt increase since 1850 A.D.. This is closely related to the industrial revolution worldwide. We can also observe sudden decrease in methane concentration during the World War I and World War II. It implies that the industrial revolution has dominated the atmospheric greenhouse gas emission for about 100 years. Besides, the average methane concentration in the Himalayan ice core is

  8. Developing Climate Data Records (CDRs) From NPOESS Data

    NASA Astrophysics Data System (ADS)

    Privette, J. L.; Bates, J. J.; Karl, T.; Markham, D.; Kearns, E. J.

    2008-12-01

    As part of its climate mandate, NOAA has a responsibility to provide the Nation with objective data and tools to help it characterize, understand, predict, mitigate and adapt to climate change and variability. To help fulfill that responsibility, NOAA has begun coordinating its Climate Data Record (CDR) activities with other agencies through the U.S. Climate Change Science Program (CCSP). The National Research Council (NRC, 2004) defines a CDR as "a time series of measurements of sufficient length, consistency, and continuity to determine climate variability and change." Since NPOESS represents a critical CDR data source, new efforts are underway to ensure NPOESS data can be used efficiently and economically to achieve climate goals -- particularly product reprocessing. NOAA's National Climatic Data Center (NCDC) initiated the Scientific Data Stewardship (SDS) Project to lead the Agency's CDR activities and to coordinate with the partner agencies. Given that early algorithm development is supported elsewhere, the SDS Project is focused on the generalization and application of mature algorithms to multiple satellites and sensors which together span climate-relevant time periods. It will also emphasize development and generation of Climate Information Records (CIRs), defined as time series, derived from CDRs and related long-term measurements, that provide specific information about environmental phenomena of particular importance to science and society (e.g., Tropical and Extra-Tropical Storm Intensity, Arctic Ozone Hole Area and Magnitude, Drought Severity). The SDS Project expects to execute its responsibilities in partnership with the larger scientific community through annual NOAA Announcements of Opportunity -- open to academic, commercial, non-profit and government proposers -- as well as through community reviews and working groups. This presentation will describe NOAA's climate product plans for NPOESS, initial SDS goals and objectives, and vision for the

  9. Ice Core Records of Recent Northwest Greenland Climate

    NASA Astrophysics Data System (ADS)

    Osterberg, E. C.; Wong, G. J.; Ferris, D.; Lutz, E.; Howley, J. A.; Kelly, M. A.; Axford, Y.; Hawley, R. L.

    2014-12-01

    Meteorological station data from NW Greenland indicate a 3oC temperature rise since 1990, with most of the warming occurring in fall and winter. According to remote sensing data, the NW Greenland ice sheet (GIS) and coastal ice caps are responding with ice mass loss and margin retreat, but the cryosphere's response to previous climate variability is poorly constrained in this region. We are developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate change and cryospheric response in NW Greenland to improve projections of future ice loss and sea level rise in a warming climate. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 21 m) from the coastal region of the GIS (2Barrel site; 76.9317o N, 63.1467o W, 1685 m el.) and the summit of North Ice Cap (76.938o N, 67.671o W, 1273 m el.) in 2011, 2012 and 2014. The 2Barrel ice core record has statistically significant relationships with regional spring and fall Baffin Bay sea ice extent, summertime temperature, and annual precipitation. Here we evaluate relationships between the 2014 North Ice Cap firn core glaciochemical record and climate variability from regional instrumental stations and reanalysis datasets. We compare the coastal North Ice Cap record to more inland records from 2Barrel, Camp Century and NEEM to evaluate spatial and elevational gradients in recent NW Greenland climate change.

  10. Calculation of average landslide frequency using climatic records

    Treesearch

    L. M. Reid

    1998-01-01

    Abstract - Aerial photographs are used to develop a relationship between the number of debris slides generated during a hydrologic event and the size of the event, and the long-term average debris-slide frequency is calculated from climate records using the relation.

  11. Identifying climate change threats to the arctic archaeological record

    NASA Astrophysics Data System (ADS)

    Murray, Maribeth; Jensen, Anne; Friesen, Max

    2011-05-01

    Global Climate Change and the Polar Archaeological Record; Tromsø, Norway, 15-16 February 2011 ; A workshop was held at the Institute of Archaeology and Social Anthropology, University of Tromsø, in Norway, to catalyze growing concern among polar archaeologists about global climate change and attendant threats to the polar archaeological and paleoecological records. Arctic archaeological sites contain an irreplaceable record of the histories of the many societies that have lived in the region over past millennia. Associated paleoecological deposits provide powerful proxy evidence for paleoclimate and ecosystem structure and function and direct evidence of species diversity, distributions, and genetic variability. Archaeological records can span most of the Holocene (the past ∼12,000 years), depending upon location, and paleoecological records extend even further. Most are largely unstudied, and, although extremely vulnerable to destruction, they are poorly monitored and not well protected. Yet these records are key to understanding how the Arctic has functioned as a system, how humans were integrated into it, and how humans may have shaped it. Such records provide a wide range of data that are not obtainable from sources such as ice and ocean cores; these data are needed for understanding the past, assessing current and projecting future conditions, and adapting to ongoing change.

  12. Late Pliocene-Quaternary humidity fluctuations on the NE Tibetan Plateau deduced from the magnetic record in lacustrine sediments of the Qaidam paleolake (Invited)

    NASA Astrophysics Data System (ADS)

    Herb, C.; Zhang, W.; Appel, E.; Koutsodendris, A.; Pross, J.; Fang, X.

    2013-12-01

    The Qaidam Basin on the NE fringe of the Tibetan Plateau is well-suited for studying past environmental changes as it contains a thick sediment sequence that was deposited almost continuously since the Eocene. The deep drilling core SG-1 (~940-m-long) from the Chahansilatu sub-basin in the western part of the Qaidam Basin offers a time span from 2.8 Ma to the complete drying of the lake near the drilling location at ~0.1 Ma (average sedimentation rate 35.1 cm/kyr). The presently hyper-arid Qaidam Basin is located in the area of influence of the Westerlies and may have been reached by the East Asian and possible even the Indian monsoon in the past. The integrated observation of several magnetic proxies recorded in drill core SG-1 allows detecting magnetic susceptibility (χ) as a useful high-resolution (~1 ka) climate proxy with supporting information from other parameters. Long-term trends of χ can be attributed to changing lake levels inferred from the comparison to lithological studies of SG-1 and to local tectonic activity. Short-term cyclic variation of χ, which exceed the magnitude of the long-term shift, can be correlated to marine oxygen isotope records. Spectral analysis suggests that the χ variation contains a response to orbital forcing. The cyclic χ variation can be attributed to a mixture between (i) low-temperature oxidation (LTO) in the catchment area and (ii) a change of the catchment area during past times. LTO in the catchment implies strong weathering and accordingly higher lake levels in times of low χ values and vice versa. In contrast, a spatial change of the catchment area points to more humid times with prevailing surface erosion in lower elevations accompanied by sediment supply with higher χ values. We compared the magnetic signature to palynological results in order to confirm the link between χ in the lacustrine sediments of drill core SG-1 and past environmental changes and to use lows and highs of χ for high

  13. METEOSAT IR and WV channels Fundamental Climate Data Record

    NASA Astrophysics Data System (ADS)

    Roebeling, Rob; John, Viju; Hewison, Tim; Lattanzio, Alessio; Schulz, Joerg

    2015-04-01

    The detection of climate change and analysis of climate variability at inter-annual scales requires long-term, well calibrated observations that are homogenised in time and space. Observations from EUMETSAT's series of Meteosat First Generation (MFG) and Meteosat Second Generation (MSG) geostationary satellites span a period from 1982 to today. Although these satellites provide data for climate analysis at multi-decadal scales, their applicability for such analysis is hampered by heterogeneities in the time series due to successive radiometers having different filter functions and changes in the calibration methodology. EUMETSAT initiated the activity to improve the quality of these data, and generates a Fundamental Climate Data Record (FCDR) of Water Vapour (WV) and Infrared (IR) channel radiances, i.e., a long-term data record of calibrated and quality-controlled sensor data designed to allow the generation of homogeneous products that are accurate and stable enough for climate monitoring. The generation of this FCDR is part of EUMETSATs activities in the European Re-Analysis of global CLIMate observations 2 (ERA-CLIM2) project. We present a method to inter-calibrate the complete time series of WV (6.3 µm) and IR (11.8 µm) channel radiances from MFG-MVIRI and MSG-SEVIRI observations. Our method is based on the principles of the Global Space-based Inter-Calibration System (GSICS). A systematic review of spectral conversion functions, which often dominate the errors, indicates that spectral changes of the WV channel from HIRS/2 to HIRS/3 triples the uncertainty of inter-calibrated METEOSAT WV radiances. We will show that these issues can be circumvented by using HIRS/2, AIRS, and IASI as reference instruments, and thus keeping the uncertainties due to spectral conversion similar throughout the time series. Finally we will present an evaluation of 30 years of recalibrated HIRS, MVIRI and /SEVIRI radiances from the IR and WV channels, and demonstrate their improved

  14. Tropical Glaciers: Recorders and Indicators of Climate Change

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E. S.; Buffen, A.; Urmann, D.; Davis, M. E.; Lin, P.

    2008-12-01

    Tropical climate is dominated on interannual time scales by monsoons and especially by ENSO, which is responsible for meteorological phenomena that directly or indirectly affect most regions on the planet and their populations. Common tropical teleconnections to the extra tropics include a stronger Aleutian low, stronger westerlies, variations in convective activity (flooding and drought), and modulation of tropical storm intensities. New ice core records from the Quelccaya and Coropuna ice caps provide 1700 years of continuous, annually-resolved records of climate and environmental variability expressed in the oxygen and hydrogen isotopic ratios, concentrations of mineral dust and various chemical species and net mass accumulation. These records provide an opportunity to examine the nature of tropical climate variability in greater detail, and to extract new information on ENSO and monsoon-linked climate phenomena. Quelccaya records display a prominent Little Ice Age isotopic depletion from 1520 to 1880 A.D. and a muted Medieval Warming between 1100 and 1300 AD. Drier conditions dominated from 300 to 500 AD, 1190 to 1470 AD and 1710 to 1910 with slightly wetter conditions from 500 to 1190 AD, and much wetter conditions from 1470 to 1710 A.D. and from 1910 A.D. to the present. The major cation and anion concentrations record other environmental changes over the past 1700 years. The longer tropical climate histories from Coropuna and Huascarán (Peru), Sajama (Bolivia), and Kilimanjaro (Tanzania) document abrupt climate disruptions such as the 4.2 ka drought and an extreme cold and wet period centered at 5.2 ka. The well documented ongoing ice loss on Quelccaya and Kilimanjaro paint a grim future for glacier histories from the tropics. The current melting of high-altitude, low-latitude ice fields is consistent with model predictions for a vertical amplification of temperature in the tropics. The ongoing glacier retreat in the Andes, Himalayas and Africa has

  15. Biomarker records of Holocene climate variations in Asian interior

    NASA Astrophysics Data System (ADS)

    Song, M.; Liu, Z.; Liu, W.; Zhao, C.; Li, S.; He, Y.

    2012-12-01

    Understanding Holocene climate fluctuation may provide clues to projection of future climate change. Lake sediments in the arid central Asia (ACA), as an archive of past climate information, keep attracting considerable interest. We have retrieved several sediment cores from Lake Manas, an endorheic lake in Zunggar desert, Xinjiang Province, China. Biomarker proxies including alkenone Uk'37, %C37:4 and C37 concentration (C37 Conc), and physical proxies including density and magnetic susceptibility (MS) have been analyzed. We have found substantial climatic and environmental changes during the late Holocene. Density, MS and Uk'37 values are high during Medieval Warm Period (MWP) and C37 Conc is very low. During the Little Ice Age, density and MS decrease, Uk'37 values drop to near 0.1, C37 Conc is increased by 2 to 3 magnitude. Thus, warm and dry conditions dominated MWP while cold and wet conditions dominated LIA, a typical "Westerly" pattern which is opposite to the hydrological variation in Asian monsoonal regions. Biomarker records' correlation with solar irradiance (SI), the North Atlantic Oscillation (NAO), the 1000year ACA Moisture Index (ACAM), and the North Hemisphere Temperature (NHT) suggests SI as one of the forcing factor on temperature fluctuation and cold and wet LIA possibly resulting from westerly-jet shift, negative NAO oscillation and the lower evaporation induced by the decrease of temperature. Biomarker records for the whole Holocene will be also presented.

  16. Solar driven climate changes recorded in Holocene alpine speleothems

    NASA Astrophysics Data System (ADS)

    Frisia, S.; Borsato, A.; Preto, N.; McDermott, F.

    2003-04-01

    Inter-annual variations in the growth rate of three annually laminated speleothems from Grotta di Ernesto, an alpine cave located at 1160 m a.s.l. in northern Italy, reveal significant periodicities at ca. 1/11 and 1/22 cycles/yr, related to changes in solar irradiance. Additional frequency components may be related to the influence of NAO/AO mode changes. In the late Holocene, reduced calcite deposition during historic minima of solar output is indicative of the influence of solar forcing on Alpine climate and environment. Annual growth laminae thickness, controlled by cave drip-water supersaturation with respect to calcite, primarily reflects changes in soil pCO_2 production modulated by incoming solar radiation. The preservation of high-frequency signals, and the rapid response of speleothem climate proxy series to changes in solar radiation, favor atmospheric amplification of solar variability, rather than mechanisms involving changes in oceanic circulation. In the early- to mid-Holocene, only the lower frequency components of solar variability are preserved. Periods of reduced calcite deposition roughly correspond to the ca. 10^3-yrs-scale cycles of North Atlantic drift-ice records. Lowest growth rates are recorded at about 3200 and 6800 years BP. If the lamina thickness-climate relationships assessed for the Recent (through present-day monitoring, and by correlation with 200 years of instrumental records) held also for the mid and early Holocene, these episodes were characterized by very cold winters and relatively dry summers.

  17. Progress and Processes for Generating NOAA's Climate Data Records

    NASA Astrophysics Data System (ADS)

    Johnston, S. S.; Glance, W. J.; Bates, J. J.; Kearns, E. J.

    2011-12-01

    NOAA established a satellite Climate Data Record Program (CDRP) at its National Climatic Data Center (NCDC) to provide a systematic reprocessing capability which will generate sustained and authoritative climate information from 30+ years of satellite data. CDRP implements a unique approach in archiving not only the data products themselves, but also the software, ancillary data, and enough documentation to allow any user with the processing power, to reproduce the data. Best practices, such as a common maturity matrix, software guidelines, and format standards, are employed to facilitate both the transition of research algorithms to operational software, and the long-term maintenance of the software. Throughout the implementation and execution of the program, CDRP seeks to adhere to production guidelines from Global Climate Observing System (GCOS) and World Meteorological Organization's (WMO's) Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM activity. Elements of the CDR Adaptive Processing System (CAPS) are described, along with the system's implementation approach, performance expectations, and plans for growth to accommodate increased CDR processing. In addition, a cost model has been implemented to capture the cost of CDR generation and maintenance, considering variables such as CDR complexity, source, and maturity at the beginning of the process.

  18. Antarctic climate signature in the Greenland ice core record

    PubMed Central

    Barker, Stephen; Knorr, Gregor

    2007-01-01

    A numerical algorithm is applied to the Greenland Ice Sheet Project 2 (GISP2) dust record from Greenland to remove the abrupt changes in dust flux associated with the Dansgaard–Oeschger (D–O) oscillations of the last glacial period. The procedure is based on the assumption that the rapid changes in dust are associated with large-scale changes in atmospheric transport and implies that D–O oscillations (in terms of their atmospheric imprint) are more symmetric in form than can be inferred from Greenland temperature records. After removal of the abrupt shifts the residual, dejumped dust record is found to match Antarctic climate variability with a temporal lag of several hundred years. It is argued that such variability may reflect changes in the source region of Greenland dust (thought to be the deserts of eastern Asia). Other records from this region and more globally also reveal Antarctic-style variability and suggest that this signal is globally pervasive. This provides the potential basis for suggesting a more important role for gradual changes in triggering more abrupt transitions in the climate system. PMID:17954910

  19. Reconciliation of the Devils Hole climate record with orbital forcing

    NASA Astrophysics Data System (ADS)

    Moseley, Gina E.; Edwards, R. Lawrence; Wendt, Kathleen A.; Cheng, Hai; Dublyansky, Yuri; Lu, Yanbin; Boch, Ronny; Spötl, Christoph

    2016-01-01

    The driving force behind Quaternary glacial-interglacial cycles and much associated climate change is widely considered to be orbital forcing. However, previous versions of the iconic Devils Hole (Nevada) subaqueous calcite record exhibit shifts to interglacial values ~10,000 years before orbitally forced ice age terminations, and interglacial durations ~10,000 years longer than other estimates. Our measurements from Devils Hole 2 replicate virtually all aspects of the past 204,000 years of earlier records, except for the timing during terminations, and they lower the age of the record near Termination II by ~8000 years, removing both ~10,000-year anomalies. The shift to interglacial values now broadly coincides with the rise in boreal summer insolation, the marine termination, and the rise in atmospheric CO2, which is consistent with mechanisms ultimately tied to orbital forcing.

  20. Coralline red algae as high-resolution climate recorders

    NASA Astrophysics Data System (ADS)

    Halfar, J.; Steneck, R. S.; Joachimski, M.; Kronz, A.; Wanamaker, A. D., Jr.

    2008-06-01

    Most high-resolution, proxy-based paleoclimate research hasconcentrated on tropical oceans, while mid- and high-latitudemarine regions have received less attention, despite their importancein the global climate system. At present, sclerochronologicalanalyses of bivalve mollusks supply the bulk of annual- to subannual-resolutionextratropical marine climate data, even though interpretationis complicated by a slowdown of growth with increasing shellage. Hence, in order to address the need for additional high-resolutionproxy climate data from extratropical regions, we conductedthe first year-long in situ field calibration of the corallinered alga Clathromorphum compactum in the Gulf of Maine, UnitedStates. Coralline red algae are widely distributed in coastalregions worldwide, and individual calcified plants can livecontinuously for several centuries in temperate and subarcticoceans. Stable oxygen isotopes extracted at subannual resolutionfrom growth increments of monitored specimens of C. compactumrelate well to in situ-measured sea-surface temperaturesduring the May to December calcification period, highlightingthe suitability of coralline red algae as an extratropical climatearchive. Furthermore, there is a strong correlation betweena 30 yr {sigma}18O record of C. compactum and an instrumental sea-surfacetemperature record (r = -0.58, p = 0.0008) and a proxyreconstruction derived from the bivalve Arctica islandica collectedin the central Gulf of Maine (r = 0.54, p = 0.002).

  1. New Unified Sea Ice Thickness Climate Data Record

    NASA Astrophysics Data System (ADS)

    Lindsay, Ron

    2010-11-01

    With the recent dramatic record­low ice extent of 2007 and with the third-lowest extent having been recorded in 2010, the changing Arctic climate, and particularly the rapidly changing sea ice cover, is often in the news. The climate models of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report forecast that rising Arctic temperatures and the reduction of sea ice will be the earliest and strongest indications of global warming. However, these models generally underestimate the observed rate of change in summer ice cover over the past 3 decades [Stroeve et al., 2007]. To better understand, predict, and adapt to the changing conditions in the Arctic, more and better organized observations of the state of the sea ice cover are needed by a variety of groups, including coastal communities, shipping interests, the fishing industry, the Arctic Council, and contributors to the IPCC's upcoming Fifth Assessment Report and the U.S. National Oceanic and Atmospheric Administration's (NOAA) ongoing Arctic Report Card.

  2. Break and trend analysis of EUMETSAT Climate Data Records

    NASA Astrophysics Data System (ADS)

    Doutriaux-Boucher, Marie; Zeder, Joel; Lattanzio, Alessio; Khlystova, Iryna; Graw, Kathrin

    2016-04-01

    EUMETSAT reprocessed imagery acquired by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat 8-9. The data covers the period from 2004 to 2012. Climate Data Records (CDRs) of atmospheric parameters such as Atmospheric Motion Vectors (AMV) as well as Clear and All Sky Radiances (CSR and ASR) have been generated. Such CDRs are mainly ingested by ECMWF to produce a reanalysis data. In addition, EUMETSAT produced a long CDR (1982-2004) of land surface albedo exploiting imagery acquired by the Meteosat Visible and Infrared Imager (MVIRI) on board Meteosat 2-7. Such CDR is key information in climate analysis and climate models. Extensive validation has been performed for the surface albedo record and a first validation of the winds and clear sky radiances have been done. All validation results demonstrated that the time series of all parameter appear homogeneous at first sight. Statistical science offers a variety of analyses methods that have been applied to further analyse the homogeneity of the CDRs. Many breakpoint analysis techniques depend on the comparison of two time series which incorporates the issue that both may have breakpoints. This paper will present a quantitative and statistical analysis of eventual breakpoints found in the MVIRI and SEVIRI CDRs that includes attribution of breakpoints to changes of instruments and other events in the data series compared. The value of different methods applied will be discussed with suggestions how to further develop this type of analysis for quality evaluation of CDRs.

  3. Antarctic Cenozoic climate history from sedimentary records: ANDRILL and beyond.

    PubMed

    McKay, R M; Barrett, P J; Levy, R S; Naish, T R; Golledge, N R; Pyne, A

    2016-01-28

    Mounting evidence from models and geological data implies that the Antarctic Ice Sheet may behave in an unstable manner and retreat rapidly in response to a warming climate, which is a key factor motivating efforts to improve estimates of Antarctic ice volume contributions to future sea-level rise. Here, we review Antarctic cooling history since peak temperatures of the Middle Eocene Climatic Optimum (approx. 50 Ma) to provide a framework for future initiatives to recover sediment cores from subglacial lakes and sedimentary basins in Antarctica's continental interior. While the existing inventory of cores has yielded important insights into the biotic and climatic evolution of Antarctica, strata have numerous and often lengthy time breaks, providing a framework of 'snapshots' through time. Further cores, and more work on existing cores, are needed to reconcile Antarctic records with the more continuous 'far-field' records documenting the evolution of global ice volume and deep-sea temperature. To achieve this, we argue for an integrated portfolio of drilling and coring missions that encompasses existing methodologies using ship- and sea-ice-/ice-shelf-based drilling platforms as well as recently developed seafloor-based drilling and subglacial access systems. We conclude by reviewing key technological issues that will need to be overcome.

  4. Climatic records over the past 30 ka from temperate Australia - a synthesis from the Oz-INTIMATE workgroup

    NASA Astrophysics Data System (ADS)

    Petherick, L.; Bostock, H.; Cohen, T. J.; Fitzsimmons, K.; Tibby, J.; Fletcher, M.-S.; Moss, P.; Reeves, J.; Mooney, S.; Barrows, T.; Kemp, J.; Jansen, J.; Nanson, G.; Dosseto, A.

    2013-08-01

    Temperate Australia sits between the heat engine of the tropics and the cold Southern Ocean, encompassing a range of rainfall regimes and falling under the influence of different climatic drivers. Despite this heterogeneity, broad-scale trends in climatic and environmental change are evident over the past 30 ka. During the early glacial period (˜30-22 ka) and the Last Glacial Maximum (˜22-18 ka), climate was relatively cool across the entire temperate zone and there was an expansion of grasslands and increased fluvial activity in regionally important Murray-Darling Basin. The temperate region at this time appears to be dominated by expanded sea ice in the Southern Ocean forcing a northerly shift in the position of the oceanic fronts and a concomitant influx of cold water along the southeast (including Tasmania) and southwest Australian coasts. The deglacial period (˜18-12 ka) was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records, while there is some evidence for climatic reversals (e.g. the Antarctic Cold Reversal) in high resolution marine sediment cores through this period. The high spatial density of Holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after ˜12 ka, presumably in response to increasing temperature, while hydrological records reveal spatially heterogeneous hydro-climatic trends. Patterns after ˜6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by the El Niño/Southern Oscillation.

  5. Developing climate data records and essential climate variables from landsat data

    USGS Publications Warehouse

    Dwyer, John; Dinardo, Thomas P.; Muchoney, Douglas M.

    2011-01-01

    The series of Landsat missions has compiled the longest record of satellite observation of the Earth’s land surface, extending for more than 38 years for most areas of the globe. Landsat data are particularly important as long term climate data records because the scale of observation is sufficient to differentiate between natural and human drivers of land cover change. The USGS has established consistent radiometric calibration across the Landsat TM and ETM+ sensors, and have extended the calibration back to the earlier MSS sensors. The USGS is developing capabilities to create fundamental climate data records (FCDRs), thematic climate data records (TCDRs), and essential climate variables (ECVs) from the Landsat data archive. Two high priority TCDRs were identified: surface reflectance and land surface temperature because they have direct application or are required as input to the generation of ECVs. We will focus development on a few of the terrestrial ECVs that have a high potential for being derived from Landsat data, that include land cover, albedo, fire disturbance, surface water, snow and ice, and leaf area index (LAI). We are collaborating with scientists who have demonstrated successful algorithm development and application of these science products to develop a framework of processing capabilities to support research projects and land management applications, along with an independent strategy for product validation. Our goal is to scale the creation and validation of these products from specific sites in the conterminous U.S. and Alaska, for extension to continental and global scales.

  6. Evidence for climate change in the satellite cloud record

    NASA Astrophysics Data System (ADS)

    Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; Zelinka, Mark D.; O'Dell, Christopher W.; Klein, Stephen A.

    2016-08-01

    Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

  7. Evidence for climate change in the satellite cloud record.

    PubMed

    Norris, Joel R; Allen, Robert J; Evan, Amato T; Zelinka, Mark D; O'Dell, Christopher W; Klein, Stephen A

    2016-08-04

    Clouds substantially affect Earth's energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

  8. Evidence for climate change in the satellite cloud record

    SciTech Connect

    Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; Zelinka, Mark D.; O'Dell, Christopher W.; Klein, Stephen A.

    2016-07-11

    Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space1. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming2, 3. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts4, 5. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. Here, these results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

  9. Evidence for climate change in the satellite cloud record

    SciTech Connect

    Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; Zelinka, Mark D.; O'Dell, Christopher W.; Klein, Stephen A.

    2016-07-11

    Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space1. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming2, 3. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts4, 5. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. Here, these results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

  10. Evidence for climate change in the satellite cloud record

    DOE PAGES

    Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; ...

    2016-07-11

    Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space1. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming2, 3. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts4, 5. Here we show that several independent, empirically corrected satellitemore » records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. Here, these results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.« less

  11. Using satellite microwave sensors to develop climate data records

    NASA Astrophysics Data System (ADS)

    Ferraro, Ralph; Meng, Huan; Luo, Zhengzhao

    2011-08-01

    NOAA Workshop on Climate Data Records From Satellite Passive Microwave Sounders: AMSU/MHS/SSMT2; College Park, Maryland, 2-3 March 2011 ; The National Oceanic and Atmospheric Administration's (NOAA) Climate Data Record (CDR) program (http://www.ncdc.noaa.gov/cdr/index.html) is an effort to create long-term homogeneous records of satellite measurements and derived products. As part of this effort, scientists at two related projects that focus on passive microwave sensors with the goal of hydrological applications—one led by a National Environmental Satellite, Data, and Information Service/Center for Satellite Applications and Research (STAR) team and one led by the City College of New York (CCNY)—held a joint workshop with the following objectives: To allow the CDR teams to interact with satellite data and product users and other CDR developers on relevant aspects of sensor characteristics and intercalibration that will lead to mature CDRs; To provide a formal mechanism for input by subject matter experts, in particular, sensor scientists and engineers; and> To move toward a community consensus approach for NOAA microwave sounder CDRs.

  12. Homogeneity of a Global Multisatellite Soil Moisture Climate Data Record

    NASA Technical Reports Server (NTRS)

    Su, Chun-Hsu; Ryu, Dongryeol; Dorigo, Wouter; Zwieback, Simon; Gruber, Alexander; Albergel, Clement; Reichle, Rolf H.; Wagner, Wolfgang

    2016-01-01

    Climate Data Records (CDR) that blend multiple satellite products are invaluable for climate studies, trend analysis and risk assessments. Knowledge of any inhomogeneities in the CDR is therefore critical for making correct inferences. This work proposes a methodology to identify the spatiotemporal extent of the inhomogeneities in a 36-year, global multisatellite soil moisture CDR as the result of changing observing systems. Inhomogeneities are detected at up to 24 percent of the tested pixels with spatial extent varying with satellite changeover times. Nevertheless, the contiguous periods without inhomogeneities at changeover times are generally longer than 10 years. Although the inhomogeneities have measurable impact on the derived trends, these trends are similar to those observed in ground data and land surface reanalysis, with an average error less than 0.003 cubic meters per cubic meter per year. These results strengthen the basis of using the product for long-term studies and demonstrate the necessity of homogeneity testing of multisatellite CDRs in general.

  13. Decadal and centennial cycles revealed in two climate isotopic records

    NASA Astrophysics Data System (ADS)

    Taricco, C.; Alessio, S.

    We measured the delta 13C profile of Globigerinoides Ruber in a shallow water Ionian sea core dated with high precision by means of radiometric and tephroanalysis methods. The time series, covering the period 200-1979 AD with a resolution of 3.87 years, is analyzed using the Wavelet Transform (WT). The same analysis is performed also on another climatic record, the tree-rings delta 13C of a Japanese cedar, spanning a similar time interval (125-1952 AD). The Wavelet Spectra (WS) of the two series and the Cross Wavelet Spectrum (CWS) between them allow highlighting the common spectral content on different time scales and investigating a possible link between climate and solar variations.

  14. Homogeneity of a Global Multisatellite Soil Moisture Climate Data Record

    NASA Technical Reports Server (NTRS)

    Su, Chun-Hsu; Ryu, Dongryeol; Dorigo, Wouter; Zwieback, Simon; Gruber, Alexander; Albergel, Clement; Reichle, Rolf H.; Wagner, Wolfgang

    2016-01-01

    Climate Data Records (CDR) that blend multiple satellite products are invaluable for climate studies, trend analysis and risk assessments. Knowledge of any inhomogeneities in the CDR is therefore critical for making correct inferences. This work proposes a methodology to identify the spatiotemporal extent of the inhomogeneities in a 36-year, global multisatellite soil moisture CDR as the result of changing observing systems. Inhomogeneities are detected at up to 24 percent of the tested pixels with spatial extent varying with satellite changeover times. Nevertheless, the contiguous periods without inhomogeneities at changeover times are generally longer than 10 years. Although the inhomogeneities have measurable impact on the derived trends, these trends are similar to those observed in ground data and land surface reanalysis, with an average error less than 0.003 cubic meters per cubic meter per year. These results strengthen the basis of using the product for long-term studies and demonstrate the necessity of homogeneity testing of multisatellite CDRs in general.

  15. Homogeneity of a global multisatellite soil moisture climate data record

    NASA Astrophysics Data System (ADS)

    Su, Chun-Hsu; Ryu, Dongryeol; Dorigo, Wouter; Zwieback, Simon; Gruber, Alexander; Albergel, Clement; Reichle, Rolf H.; Wagner, Wolfgang

    2016-11-01

    Climate Data Records (CDR) that blend multiple satellite products are invaluable for climate studies, trend analysis and risk assessments. Knowledge of any inhomogeneities in the CDR is therefore critical for making correct inferences. This work proposes a methodology to identify the spatiotemporal extent of the inhomogeneities in a 36 year, global multisatellite soil moisture CDR as the result of changing observing systems. Inhomogeneities are detected at up to 24% of the tested pixels with spatial extent varying with satellite changeover times. Nevertheless, the contiguous periods without inhomogeneities at changeover times are generally longer than 10 years. Although the inhomogeneities have measurable impact on the derived trends, these trends are similar to those observed in ground data and land surface reanalysis, with an average error less than 0.003 m3 m-3 y-1. These results strengthen the basis of using the product for long-term studies and demonstrate the necessity of homogeneity testing of multisatellite CDRs in general.

  16. Evaluation of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    NASA Astrophysics Data System (ADS)

    Lattanzio, Alessio; Schulz, Joerg; Roebeling, Rob; Fell, Frank; Bennartz, Ralf; Cahill, Brownwyn; Muller, Jan-Peter; Shane, Neville; Trigo, Isabel; Watson, Gill

    2013-04-01

    Understanding the climate system, with its variability and changes, requires a joint long-term international commitment from research and governmental institutions. The Global Climate Observing System (GCOS) formulated scientific requirements for the needed global observations and products including a list of relevant parameters, the so called Essential Climate Variables (ECVs). The Sustained and Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) activity, is answering to these requirements by establishing an international network of facilities to ensure a continuous and sustained generation of high-quality Climate Data Records (CDR) from satellite data in compliance with the GCOS principles and guidelines. Currently, SCOPE-CM represents a partnership between operational space agencies to coordinate the generation of CDRs. Within the SCOPE-CM framework the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) has generated the Meteosat Surface Albedo (MSA) Climate Data Record that comprises up to 25 years (1982-2010) of continuous surface albedo coverage for large areas of the Earth. As part of the SCOPE-CM activity on land surface albedo, involving the operational meteorological satellite agencies in Europe (EUMETSAT), in Japan (JMA: Japanese Meteorological Agency) and in the USA (NOAA: National Oceanic and Atmospheric Administration), the MSA CDR contributes to the creation of a global harmonised surface albedo record derived from all satellites in geostationary orbit. This presentation discusses the results of an evaluation study for the MSA CDR that has been performed by independent researchers in Europe and the US. The MSA CDR has been evaluated in terms of its internal consistency, its compatibility to other satellite-derived surface albedo products, its validity against in-situ observations of superior quality, and its temporal homogeneity. The evaluation of the MSA data record has revealed a

  17. Past freeze and thaw cycling in the margin of the El'gygytgyn crater deduced from a 141 m long permafrost record

    NASA Astrophysics Data System (ADS)

    Schwamborn, G.; Meyer, H.; Schirrmeister, L.; Fedorov, G.

    2014-06-01

    The continuous sediment record from Lake El'gygytgyn in the northeastern Eurasian Arctic spans the last 3.6 Ma and for much of this time permafrost dynamics and lake level changes have likely played a crucial role for sediment delivery to the lake. Changes in the ground-ice hydrochemical composition (δ18O, δD, pH, electrical conductivity, Na+, Mg2+, Ca2+, K+, HCO3-, Cl-, SO4-) of a 141 m long permafrost record from the western crater plain are examined to reconstruct repeated periods of freeze and thaw at the lake edge. Stable water isotope and major ion records of ground ice in the permafrost reflect both a synsedimentary palaeo-precipitation signal preserved in the near-surface permafrost (0.0-9.1 m core depth) and a post-depositional record of thawing and refreezing in deeper layers of the core (9.1-141.0 m core depth). These lake marginal permafrost dynamics were controlled by lake level changes that episodically flooded the surfaces and induced thaw in the underlying frozen ground. During times of lake level fall these layers froze over again. At least three cycles of freeze and thaw are identified and the hydrochemical data point to a vertical and horizontal talik refreezing through time. Past permafrost thaw and freeze may have destabilised the basin slopes of Lake El'gygytgyn and this has probably promoted the release of mass movements from the lake edge to the deeper basin as known from frequently occurring turbidite layers in the lake sediment column.

  18. Uncertainty information in climate data records from Earth observation

    NASA Astrophysics Data System (ADS)

    Merchant, Christopher J.; Paul, Frank; Popp, Thomas; Ablain, Michael; Bontemps, Sophie; Defourny, Pierre; Hollmann, Rainer; Lavergne, Thomas; Laeng, Alexandra; de Leeuw, Gerrit; Mittaz, Jonathan; Poulsen, Caroline; Povey, Adam C.; Reuter, Max; Sathyendranath, Shubha; Sandven, Stein; Sofieva, Viktoria F.; Wagner, Wolfgang

    2017-07-01

    The question of how to derive and present uncertainty information in climate data records (CDRs) has received sustained attention within the European Space Agency Climate Change Initiative (CCI), a programme to generate CDRs addressing a range of essential climate variables (ECVs) from satellite data. Here, we review the nature, mathematics, practicalities, and communication of uncertainty information in CDRs from Earth observations. This review paper argues that CDRs derived from satellite-based Earth observation (EO) should include rigorous uncertainty information to support the application of the data in contexts such as policy, climate modelling, and numerical weather prediction reanalysis. Uncertainty, error, and quality are distinct concepts, and the case is made that CDR products should follow international metrological norms for presenting quantified uncertainty. As a baseline for good practice, total standard uncertainty should be quantified per datum in a CDR, meaning that uncertainty estimates should clearly discriminate more and less certain data. In this case, flags for data quality should not duplicate uncertainty information, but instead describe complementary information (such as the confidence in the uncertainty estimate provided or indicators of conditions violating the retrieval assumptions). The paper discusses the many sources of error in CDRs, noting that different errors may be correlated across a wide range of timescales and space scales. Error effects that contribute negligibly to the total uncertainty in a single-satellite measurement can be the dominant sources of uncertainty in a CDR on the large space scales and long timescales that are highly relevant for some climate applications. For this reason, identifying and characterizing the relevant sources of uncertainty for CDRs is particularly challenging. The characterization of uncertainty caused by a given error effect involves assessing the magnitude of the effect, the shape of the

  19. Application of microwave radiometry to improving climate data records.

    SciTech Connect

    Liljegren, J. C.; Cadeddu, M. P.; Decision and Information Sciences

    2007-01-01

    Microwave radiometers deployed by the U. S. Department of Energy's Atmospheric Radiation Measurement (ARM) Program provide crucial data for a wide range of research applications. The accuracy and stability of these instruments also makes them ideal for improving climate data records: to detect and correct discontinuities in the long-term climate records, to validate and calibrate the climate data, to characterize errors in the climate records, and to plan for the future Global Climate Observing System (GCOS) Reference Upper-Air network. This paper presents an overview of these capabilities with examples from ARM data. Two-channel microwave radiometers (MWR) operating at 23.8 and 31.4 GHz are deployed at each of eleven ARM Climate Research Facility (ACRF) field sites in the U.S. Southern Great Plains (SGP), Tropical Western Pacific (TWP), North Slope of Alaska (NSA), and with the ARM Mobile Facility in Niamey, Niger for the purpose of retrieving precipitable water vapor (PWV) and liquid water path (LWP). At these locations PWV ranges from as low as 1 mm (1 kg/m{sup 2}) at the NSA to 70 mm or more in the TWP; LWP can exceed 2 mm at many sites. The MWR accommodates this wide dynamic range for all non-precipitating conditions with a root-mean-square error of about 0.4 mm for PWV and 0.02 mm (20 g/m{sup 2}) for LWP. The calibration of the MWR is continuously and autonomously monitored and updated to maintain accuracy. Comparisons of collocated MWRs will be presented. Site-specific linear statistical retrievals are used operationally; more sophisticated retrievals are applied in post-processing the data. Because PWV is an integral measure, derived from both the relative humidity and temperature profiles of the radiosonde, it is a particularly useful reference quantity. Comparison of PWV measured by the MWR with PWV from radiosondes reveals dry biases and diurnal trends as well as general calibration variability in the radiosondes. To correct the bias and reduce the

  20. Herbivory, plant resistance, and climate in the tree ring record: Interactions distort climatic reconstructions

    PubMed Central

    Trotter, R. Talbot; Cobb, Neil S.; Whitham, Thomas G.

    2002-01-01

    To understand climate change, dendrochronologists have used tree ring analyses to reconstruct past climates, as well as ecological processes such as herbivore population dynamics. Such reconstructions, however, have been hindered by a lack of experiments that separate the influences of confounding impacts on tree rings, such as herbivores and the interactions of multiple factors. Our long-term experiments with scale insects on resistant and susceptible pines demonstrate three major points that are important to the application of this commonly used tool. (i) Herbivory reduced tree ring growth by 25–35%. (ii) The impact on ring growth distorted climate reconstruction, resulting in the overestimation of past moisture levels by more than 2-fold. Our data suggest that, if distortion because of herbivory has been a problem in previous reconstructions, estimates of the magnitude of recent climate changes are likely to be conservative. (iii) Our studies support a detectible plant resistance × herbivore × climate interaction in the tree ring record. Because resistance and susceptibility to herbivory are known to be genetically based in many systems, the potential exists to incorporate plant genetics into the field of dendrochronology, where it may be used to screen distortions from the tree ring record. PMID:12110729

  1. Herbivory, plant resistance, and climate in the tree ring record: interactions distort climatic reconstructions.

    PubMed

    Trotter, R Talbot; Cobb, Neil S; Whitham, Thomas G

    2002-07-23

    To understand climate change, dendrochronologists have used tree ring analyses to reconstruct past climates, as well as ecological processes such as herbivore population dynamics. Such reconstructions, however, have been hindered by a lack of experiments that separate the influences of confounding impacts on tree rings, such as herbivores and the interactions of multiple factors. Our long-term experiments with scale insects on resistant and susceptible pines demonstrate three major points that are important to the application of this commonly used tool. (i) Herbivory reduced tree ring growth by 25-35%. (ii) The impact on ring growth distorted climate reconstruction, resulting in the overestimation of past moisture levels by more than 2-fold. Our data suggest that, if distortion because of herbivory has been a problem in previous reconstructions, estimates of the magnitude of recent climate changes are likely to be conservative. (iii) Our studies support a detectible plant resistance x herbivore x climate interaction in the tree ring record. Because resistance and susceptibility to herbivory are known to be genetically based in many systems, the potential exists to incorporate plant genetics into the field of dendrochronology, where it may be used to screen distortions from the tree ring record.

  2. Towards a satellite-based sea ice climate data record

    NASA Astrophysics Data System (ADS)

    Meier, W. N.; Fetterer, F.; Stroeve, J.; Cavalieri, D.; Parkinson, C.; Comiso, J.; Weaver, R.

    2005-12-01

    Sea ice plays an important role in the Earth's climate through its influence on the surface albedo, heat and moisture transfer between the ocean and the atmosphere, and the thermohaline circulation. Satellite data reveal that since 1979, summer Arctic sea ice has, overall, been declining at a rate of almost 8%/decade, with recent summers (beginning in 2002) being particularly low. The receding sea ice is having an effect on wildlife and indigenous peoples in the Arctic, and concern exists that these effects may become increasingly severe. Thus, a long-term, ongoing climate data record of sea ice is crucial for tracking the changes in sea ice and for assessing the significance of long-term trends. Since the advent of passive microwave satellite instruments in the early 1970s, sea ice has been one of the most consistently monitored climate parameters. There is now a 27+ year record of sea ice extent and concentration from multi-channel passive microwave radiometers that has undergone inter-sensor calibration and other quality controls to ensure consistency throughout the record. Several algorithms have been developed over the years to retrieve sea ice extent and concentration and two of the most commonly used algorithms, the NASA Team and Bootstrap, have been applied to the entire SMMR-SSM/I record to obtain a consistent time series. These algorithms were developed at NASA Goddard Space Flight Center and are archived at the National Snow and Ice Data Center. However, the complex surface properties of sea ice affect the microwave signature, and algorithms can yield ambiguous results; no single algorithm has been found to work uniformly well under all sea ice conditions. Thus there are ongoing efforts to further refine the algorithms and the time series. One approach is to develop data fusion methods to optimally combine sea ice fields from two or more algorithms. Another approach is to take advantage of the improved capabilities of JAXA's AMSR-E sensor on NASA's Aqua

  3. Climatic record of the Iberian peninsula from lake Moncortes' sediments

    NASA Astrophysics Data System (ADS)

    Cao, Min; Huguet, Carme; Rull, Valenti; Valero, Blas; Rosell-Mele, Antoni

    2014-05-01

    Climatic record of the Iberian peninsula from lake Moncortes' sediments Min Cao1, Carme Huguet1, Valenti Rull2, Blas L. Valero-Garces3, Antoni Rosell-Melé1,4 1Institut de Ciència i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Catalonia, Spain; 2Institut de Botanic de Barcelona (CSIC), Passeig del Migdia s/n, 08038, Barcelona, Spain, 3 Instituto Pirenaico de Ecologıa (CSIC), Avda. Montañana 1005, 50059 Zaragoza, Spain, 4Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Catalonia, Spain. The continuing buildup of industrial greenhouse gases in the atmosphere and concomitant increase in global temperatures has made much of the world's society aware that decades to centuries of environmental change lie ahead, and that these will have profound economic, political and societal impacts. The Iberian Peninsula lies in the boundary between tropical and subtropical climates and seems to amplify the climatic signals form the northern hemisphere through both atmospheric and water circulation feedbacks, making it an ideal site to monitor Northern hemisphere climate changes. This extreme sensitivity to climatic changes also makes the Iberian Peninsula extremely vulnerable to future climate changes. This is why understanding sensitivity to climate change and the consequences it will have on both climate and the hydrological cycle is key to implement preventive measures. The aim of our study is to come up with a high resolution quantitative reconstruction of climate variability (temperature, production and precipitation) in the Iberian Peninsula from lake sediments. We also want to establish the relation between those changes and the ones observed in both ice cores from Greenland and paleotemperature records from marine sediments of the continental Iberian margin. For these reasons we sampled a core in Moncortes (42.3N, 0.99E), a lake of karstic origin with an average depth of 25m and an area of 0

  4. Downslope strengthening millennial-scale climatic change signals deduced from high-resolution clay mineralogy during the last glaciation in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Liu, Z.; Wang, X.; Xie, X.; Shi, J.; Christophe, C.

    2015-12-01

    Clay mineralogy provides a powerful tool to reconstruct glacial-cyclic paleoceanographic and paleoclimatic changes in the South China Sea. However, whether the clay mineralogy could also reserve millennial-scale climatic change is still poorly understood, because clay minerals usually produced through the long-term chemical weathering are not sensitive to the fast environmental change. This study presents the high-resolution clay mineralogy of three high-quality sediment cores, which were retrieved from a transect on the continental slope of the northern South China Sea during the cruise of MD190 (2012). Our results show that time series changes of clay mineral assemblages display a clear occurrence of millennial-scale climatic change events, such as Younger Dryas, Bolling-Allerod, and Heinrich events 1-6. The reconstructed relative contributions of clay minerals from their source areas of Taiwan and Luzon are closely related to the millennial-scale climatic changes, while the clay mineral contribution from the source area of the Pearl River presents a relationship to the sea level change. Following the transect with increasing water depths, the Pearl River contribution decreases, whereas the Taiwan and Luzon contributions present more complex changes, and the millennial-scale climatic change signals are also gradually strengthened. The Luzon/Taiwan contribution ratio is used for the proxy of the millennial-scale paleoclimate evolution. The lower ratio presents colder events, while the high ratio indicates warmer periods. The distinct downslope strengthening millennial-scale climatic change indicates that deepwater sediments in the South China Sea could well reserve fast climatic change events that usually occurred in high latitudes.

  5. Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and lidar data - Case study from Drangajökull ice cap, NW Iceland

    NASA Astrophysics Data System (ADS)

    Magnússon, E.; Muñoz-Cobo Belart, J.; Pálsson, F.; Ágústsson, H.; Crochet, P.

    2016-01-01

    In this paper we describe how recent high-resolution digital elevation models (DEMs) can be used to extract glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne lidar in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high-resolution lidar DEM. The lidar DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice- and snow-free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical semivariogram model, which along with the derived errors in ice- and snow-free areas were used as inputs into 1000 sequential Gaussian simulations (SGSims). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM and the 95 % confidence level of this bias. This results in bias correction varying in magnitude between 0.03 m (in 1975) and 1.66 m (in 1946) and uncertainty values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2-4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional seasonal bias correction was therefore estimated using a degree-day model to obtain the volume change between the start of 2 glaciological years (1 October). This correction was largest for the 1960 DEM, corresponding to an average elevation change of -3.5 m or approx. three-quarters of the volume change between the 1960 and the 1975 DEMs. The total uncertainty of the derived mass balance record is dominated by uncertainty in the volume

  6. Climatic variability in sclerochronological records from the northern North Sea

    NASA Astrophysics Data System (ADS)

    Trofimova, T.; Andersson Dahl, C.; Bonitz, F. G. W.

    2016-12-01

    Highly resolved palaeoreconstructions that can extend instrumental records back through time is a fundament for our understanding of a climate of the last millennia. Only a few established extratropical marine paleo archives enable the reconstruction of key ocean processes at annual to sub-annual time scales. Bivalves have been shown to provide a useful archive with high temporal resolution. The species Arctica islandica is unique proxy due to its exceptional longevity combined with sensitivity to changes in environmental conditions. In this study, we investigate the impact of climate variability on sclerochronological records of A. islandica from the Viking Bank in the northern North Sea. The hydrographical characteristics of this location are mainly controlled by the major inflow of Atlantic water in the North Sea and can potentially be reflected in the shell composition and growth of A. islandica. To reconstruct environment conditions, we use shells of living and subfossil specimens of A. islandica collected by dredging at depths around 100 meters. The annual growth bands within the shells were determined and growth increments widths were measured. By cross-matching 30 individual increment-width time series, we built an absolutely dated 265-year long shell-growth chronology spanning the time interval 1748-2013 AD. The relatively high Rbar (>0.5) and EPS (>0.85) values indicate a common environmental forcing on the shell growth within the population. The growth chronology preserves a 20-30 yr variability prior to 1900 which fades out towards the present. That change suggests a possible regime shift at the beginning of a 20th century. Ongoing work mainly focuses on comparing the shell-growth chronology with existing observational time series of climatic parameters to determine controlling factors and test the use of growth chronologies for climate reconstruction in this area. For reconstructing seasonality, we analyse the stable oxygen isotope composition of the

  7. Lacustrine Records of Holocene Climate Change From Southernmost South America

    NASA Astrophysics Data System (ADS)

    Moy, C. M.; Francois, J.; Moreno, P. I.; Dunbar, R. B.; Villa-Martinez, R.; Waldmann, N.; Ariztegui, D.

    2005-12-01

    The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere, which has a major impact on the climate of southern South America and hydrographic conditions in the Southern Ocean. Recent studies have argued that latitudinal shifts in the westerly boundaries during the LGM played a role in the modulation of atmospheric CO2 through positive feedback mechanisms within the Southern Ocean. However, significant discrepancies exist among paleoclimate records and GCM simulations. Here we present lacustrine records of late Holocene climate variability from two sites in southern South America. The first, a 4.75 meter sediment core from Laguna Guanacos (51°S, 72°W) in Southern Patagonia, provides a continuous record of climatic change related to the westerly wind regime during the last ~11,000 14C yrs. The sediment cores obtained from this small, shallow closed-basin lake reveal high concentrations of organic mater and biogenic carbonate. Eleven AMS radiocarbon dates on organic and carbonate fractions indicate that the record spans the last ~13,000 calendar years and modern dates from core tops suggest little influence by old or dead carbon sources. Combined pollen, stable isotope and elemental data indicate that significant shifts in the forest-steppe ecotone have occurred during the late Holocene. Increases in C/N and Nothofagus/Graminae index values culminating between 100 and 550 14C yrs BP are indicative of forest expansion related to cooler and moister conditions during the Little Ice Age. A large >2‰ decrease in bulk organic δ13C and a concomitant decrease in Nothofagus and rise in Rumex during the last 100 years, marks extensive burning of the region and the replacement of a forested landscape by an anthropogenic-set steppe. A positive linear relationship between δ18O and δ13C on bi-valves and ostracodes indicates that the lake behaves as a closed system and will be sensitive to changes in moisture balance

  8. The mass balance record and surge behavior of Drangajökull Ice Cap (Iceland) from 1946 to 2011 deduced from aerial photographs and LiDAR DEM

    NASA Astrophysics Data System (ADS)

    Muñoz-Cobo Belart, Joaquín; Magnússon, Eyjólfur; Pálsson, Finnur

    2014-05-01

    High resolution and accuracy (e.g. based on LiDAR survey) Digital Elevation Models (DEMs) of glaciers and their close vicinity have significantly improved the methods for calculation of geodetic mass balance and study of changes in glacier dynamics. However additional data is needed to extend such studies back in time. Here we present a geodetically derived mass balance record for Drangajökull ice cap (NW-Iceland) since 1946 to present. The mass balance is calculated from a series of DEMs derived by photogrammetric processing of aerial photographs (years: 1946, 1975, 1985, 1994) and a LiDAR DEM (2011). All Ground Control Points (GCPs) used to constrain the orientation of the aerial photographs, used in the photogrammetric processing, are picked from the LiDAR derived DEM, thus eliminating the time consuming and expensive in situ survey of GCPs. The LiDAR DEM also helps to assess the accuracy of the photogrammetrically derived DEMs, by analyzing the residuals in elevation in ice-free areas. For the DEMs of 1975, 1985 and 1994 the Root Mean Square Error (RMSE) of the residuals is less than 2 m, whereas the accuracy of the DEM of 1946 is worse, with RMSE of 5.5 m, caused by the deteriorated images. The geodetic mass balance yields a negative specific mass balance of ~-0.5 m w.e.a-¹ for the period 1946-1975, followed by periods of positive mass balance: ~0.2 m w.e.a-¹ for the period 1975-1985 and ~0.3 m w.e.a-¹ for the period 1985-1994. Negative specific mass balance of ~-0.6 m w.e.a-¹ is derived for the period 1994-2011. High mass redistribution is observed during 1985-1994 and 1994-2011 on the three main outlets of the ice cap, related to surges. The derived orthophotographs allow tracking of stable features at individual locations on the northern part of Drangajökull, indicating an average velocity of 5-10 m a-¹ for the period 1946-1985 and speeding up in the last two periods due to a surge.

  9. Reading the climate record of the martian polar layered deposits

    USGS Publications Warehouse

    Hvidberg, C.S.; Fishbaugh, K.E.; Winstrup, M.; Svensson, A.; Byrne, S.; Herkenhoff, K. E.

    2012-01-01

    The martian polar regions have layered deposits of ice and dust. The stratigraphy of these deposits is exposed within scarps and trough walls and is thought to have formed due to climate variations in the past. Insolation has varied significantly over time and caused dramatic changes in climate, but it has remained unclear whether insolation variations could be linked to the stratigraphic record. We present a model of layer formation based on physical processes that expresses polar deposition rates of ice and dust in terms of insolation. In this model, layer formation is controlled by the insolation record, and dust-rich layers form by two mechanisms: (1) increased summer sublimation during high obliquity, and (2) variations in the polar deposition of dust modulated by obliquity variations. The model is simple, yet physically plausible, and allows for investigations of the climate control of the polar layered deposits (PLD). We compare the model to a stratigraphic column obtained from the north polar layered deposits (NPLD) (Fishbaugh, K.E., Hvidberg, C.S., Byrne, S., Russel, P.S., Herkenhoff, K.E., Winstrup, M., Kirk, R. [2010a]. Geophys. Res. Lett., 37, L07201) and show that the model can be tuned to reproduce complex layer sequences. The comparison with observations cannot uniquely constrain the PLD chronology, and it is limited by our interpretation of the observed stratigraphic column as a proxy for NPLD composition. We identified, however, a set of parameters that provides a chronology of the NPLD tied to the insolation record and consistently explains layer formation in accordance with observations of NPLD stratigraphy. This model dates the top 500 m of the NPLD back to ∼1 million years with an average net deposition rate of ice and dust of 0.55 mm a−1. The model stratigraphy contains a quasi-periodic ∼30 m cycle, similar to a previously suggested cycle in brightness profiles from the NPLD (Laskar, J., Levrard, B., Mustard, F. [2002]. Nature, 419, 375

  10. Evidence of climate change in the 1949-2010 historical climate record of the Fort Cobb experimental watershed, Oklahoma

    USDA-ARS?s Scientific Manuscript database

    Seasonal and annual precipitation and air temperature records of the Fort Cobb watershed and the Fort Cobb climate division were analyzed to identify climatic trends over the last 30 to 40 years and infer if these trends could potentially be a sign of climate change due to global warming. Findings s...

  11. Climatic ice core records from the tropical quelccaya ice cap.

    PubMed

    Thompson, L G; Hastenrath, S; Arnao, B M

    1979-03-23

    The Quelccaya Ice Cap in the easternmost glaciated mountain chain of the Peruvian Andes has been studied in four recentfield seasons. Ice cores to a depth of 15 meters have been retrieved at the summit dome (elevation, 5650 meters) and two other locations and used for microparticle, isotope, and beta radioactivity measurements. A concurrent study of the present climate and the heat and mass budgets is being made to permit a paleoclimatic interpretation of deep core records. The results indicate the need for a revision of the isotope "thermometry" for application in the tropics. However, the seasonality of the beta radioactivity, microparticle content, and isotope ratios offers the prospect of a mass balance chronology. This is important in that precipitation is believed to be a more indicative paleoclimatic parameter than temperature in the tropics.

  12. Temporal Insights on Biomarker-Based Climate Records (Invited)

    NASA Astrophysics Data System (ADS)

    Drenzek, N.; Stanley, R. H.; Santos, G. M.; Southon, J. R.; Druffel, E. R.; Montlucon, D.; Hughen, K. A.; Eglinton, T. I.

    2010-12-01

    Biomarker reconstructions of climate events usually assume that the incorporation of these molecular fossils into the sedimentary archive is both synchronous with those events and temporally discrete. Studies of marine and terrigenous-sourced lipids have nonetheless uncovered significant lags between initial biosynthesis and ultimate deposition, largely owing to intervening transport processes. Here we quantitatively apportion such residence times for vascular plant leaf waxes, commonly used as proxies for various continental climate parameters, into several components by comparing the radiocarbon profiles of individual long chain fatty acids extracted from sediments to the radiocarbon evolution of atmospheric carbon dioxide using a nonlinear optimization model. We then incorporate these findings into a simplified forward box model in order to reinterpret leaf wax reconstructions of environmental changes at orbital to decadal timescales. Results from case studies in the Caribbean Sea (Cariaco Basin) and coastal British Columbia (Saanich Inlet) indicate that at least two pools of plant wax material can be defined by markedly different residence times in these systems. Fully sixty to ninety percent of long chain fatty acids in study site sediments were sequestered on land for an average of some 3340 and 4860 years, respectively, with the remainder encumbering a much shorter time of nominally ten to fifteen years. The fraction of each homologue passing through these ‘millennial’ and ‘decadal’ reservoirs systematically decreased at shorter chain length, possibly reflecting the influence of varying molecular-level properties such as degradation rate and physiochemical speciation. Viewed through this prism, the record of low frequency (orbital) climate shifts preserved in sediments will appear lagged relative to their actual timing while the magnitude of millennial to higher frequency activity will be muted. These findings indicate that a premium should be placed

  13. Evaluating and Extending the Ocean Wind Climate Data Record.

    PubMed

    Wentz, Frank J; Ricciardulli, Lucrezia; Rodriguez, Ernesto; Stiles, Bryan W; Bourassa, Mark A; Long, David G; Hoffman, Ross N; Stoffelen, Ad; Verhoef, Anton; O'Neill, Larry W; Farrar, J Tomas; Vandemark, Douglas; Fore, Alexander G; Hristova-Veleva, Svetla M; Turk, F Joseph; Gaston, Robert; Tyler, Douglas

    2017-05-01

    Satellite microwave sensors, both active scatterometers and passive radiometers, have been systematically measuring near-surface ocean winds for nearly 40 years, establishing an important legacy in studying and monitoring weather and climate variability. As an aid to such activities, the various wind datasets are being intercalibrated and merged into consistent climate data records (CDRs). The ocean wind CDRs (OW-CDRs) are evaluated by comparisons with ocean buoys and intercomparisons among the different satellite sensors and among the different data providers. Extending the OW-CDR into the future requires exploiting all available datasets, such as OSCAT-2 scheduled to launch in July 2016. Three planned methods of calibrating the OSCAT-2 σo measurements include 1) direct Ku-band σo intercalibration to QuikSCAT and RapidScat; 2) multisensor wind speed intercalibration; and 3) calibration to stable rainforest targets. Unfortunately, RapidScat failed in August 2016 and cannot be used to directly calibrate OSCAT-2. A particular future continuity concern is the absence of scheduled new or continuation radiometer missions capable of measuring wind speed. Specialized model assimilations provide 30-year long high temporal/spatial resolution wind vector grids that composite the satellite wind information from OW-CDRs of multiple satellites viewing the Earth at different local times.

  14. Evaluating and Extending the Ocean Wind Climate Data Record

    PubMed Central

    Ricciardulli, Lucrezia; Rodriguez, Ernesto; Stiles, Bryan W.; Bourassa, Mark A.; Long, David G.; Hoffman, Ross N.; Stoffelen, Ad; Verhoef, Anton; O'Neill, Larry W.; Farrar, J. Tomas; Vandemark, Douglas; Fore, Alexander G.; Hristova-Veleva, Svetla M.; Turk, F. Joseph; Gaston, Robert; Tyler, Douglas

    2017-01-01

    Satellite microwave sensors, both active scatterometers and passive radiometers, have been systematically measuring near-surface ocean winds for nearly 40 years, establishing an important legacy in studying and monitoring weather and climate variability. As an aid to such activities, the various wind datasets are being intercalibrated and merged into consistent climate data records (CDRs). The ocean wind CDRs (OW-CDRs) are evaluated by comparisons with ocean buoys and intercomparisons among the different satellite sensors and among the different data providers. Extending the OW-CDR into the future requires exploiting all available datasets, such as OSCAT-2 scheduled to launch in July 2016. Three planned methods of calibrating the OSCAT-2 σo measurements include 1) direct Ku-band σo intercalibration to QuikSCAT and RapidScat; 2) multisensor wind speed intercalibration; and 3) calibration to stable rainforest targets. Unfortunately, RapidScat failed in August 2016 and cannot be used to directly calibrate OSCAT-2. A particular future continuity concern is the absence of scheduled new or continuation radiometer missions capable of measuring wind speed. Specialized model assimilations provide 30-year long high temporal/spatial resolution wind vector grids that composite the satellite wind information from OW-CDRs of multiple satellites viewing the Earth at different local times. PMID:28824741

  15. Rapid climate changes recorded in Greenland ice cores

    SciTech Connect

    Alley, R.B.

    1995-12-31

    Exceptionally large, rapid climate changes have repeatedly affected the North Atlantic basin and beyond over the last 100,000 years, as recorded in Greenlandic ice cores. The changes involve regional or global conditions (large changes in methane, in storm tracks, and in atmospheric loading of windblown sea salt and continental dust) as well as local conditions (several degrees C in temperature, twofold change in snow accumulation). Changes occurred over decades to as little as a single year. {open_quotes}Flickering{close_quotes} behavior occurred at some transitions, with rapid fluctuations between two states over years to decades before longer-term stabilization in one of the states. Such changes almost certainly are linked to large-scale reorganizations of the atmosphere-ocean system. One significant event occurred as recently as 8,000 years ago, after the low-latitude ice sheets had largely melted, casting doubt on the hypothesis that the low-latitude ice sheets are necessary to destabilize North Atlantic climate.

  16. Global patterns and climate drivers of water-use efficiency in terrestrial ecosystems deduced from satellite-based datasets and carbon cycle models

    SciTech Connect

    Sun, Yan; Piao, Shilong; Huang, Mengtian; Ciais, Philippe; Zeng, Zhenzhong; Cheng, Lei; Li, Xiran; Zhang, Xinping; Mao, Jiafu; Peng, Shushi; Poulter, Benjamin; Shi, Xiaoying; Wang, Xuhui; Wang, Ying-Ping; Zeng, Hui

    2015-12-23

    Our aim is to investigate how ecosystem water-use efficiency (WUE) varies spatially under different climate conditions, and how spatial variations in WUE differ from those of transpiration-based water-use efficiency (WUEt) and transpiration-based inherent water-use efficiency (IWUEt). LocationGlobal terrestrial ecosystems. We investigated spatial patterns of WUE using two datasets of gross primary productivity (GPP) and evapotranspiration (ET) and four biosphere model estimates of GPP and ET. Spatial relationships between WUE and climate variables were further explored through regression analyses. Global WUE estimated by two satellite-based datasets is 1.9 ± 0.1 and 1.8 ± 0.6g C m-2mm-1 lower than the simulations from four process-based models (2.0 ± 0.3g C m-2mm-1) but comparable within the uncertainty of both approaches. In both satellite-based datasets and process models, precipitation is more strongly associated with spatial gradients of WUE for temperate and tropical regions, but temperature dominates north of 50 degrees N. WUE also increases with increasing solar radiation at high latitudes. The values of WUE from datasets and process-based models are systematically higher in wet regions (with higher GPP) than in dry regions. WUEt shows a lower precipitation sensitivity than WUE, which is contrary to leaf- and plant-level observations. IWUEt, the product of WUEt and water vapour deficit, is found to be rather conservative with spatially increasing precipitation, in agreement with leaf- and plant-level measurements. In conclusion, WUE, WUEt and IWUEt produce different spatial relationships with climate variables. In dry ecosystems, water losses from evaporation from bare soil, uncorrelated with productivity, tend to make WUE lower than in wetter regions. Yet canopy conductance is intrinsically efficient in those ecosystems and maintains a

  17. Global patterns and climate drivers of water-use efficiency in terrestrial ecosystems deduced from satellite-based datasets and carbon cycle models

    DOE PAGES

    Sun, Yan; Piao, Shilong; Huang, Mengtian; ...

    2015-12-23

    Our aim is to investigate how ecosystem water-use efficiency (WUE) varies spatially under different climate conditions, and how spatial variations in WUE differ from those of transpiration-based water-use efficiency (WUEt) and transpiration-based inherent water-use efficiency (IWUEt). LocationGlobal terrestrial ecosystems. We investigated spatial patterns of WUE using two datasets of gross primary productivity (GPP) and evapotranspiration (ET) and four biosphere model estimates of GPP and ET. Spatial relationships between WUE and climate variables were further explored through regression analyses. Global WUE estimated by two satellite-based datasets is 1.9 ± 0.1 and 1.8 ± 0.6g C m-2mm-1 lower than the simulations frommore » four process-based models (2.0 ± 0.3g C m-2mm-1) but comparable within the uncertainty of both approaches. In both satellite-based datasets and process models, precipitation is more strongly associated with spatial gradients of WUE for temperate and tropical regions, but temperature dominates north of 50 degrees N. WUE also increases with increasing solar radiation at high latitudes. The values of WUE from datasets and process-based models are systematically higher in wet regions (with higher GPP) than in dry regions. WUEt shows a lower precipitation sensitivity than WUE, which is contrary to leaf- and plant-level observations. IWUEt, the product of WUEt and water vapour deficit, is found to be rather conservative with spatially increasing precipitation, in agreement with leaf- and plant-level measurements. In conclusion, WUE, WUEt and IWUEt produce different spatial relationships with climate variables. In dry ecosystems, water losses from evaporation from bare soil, uncorrelated with productivity, tend to make WUE lower than in wetter regions. Yet canopy conductance is intrinsically efficient in those ecosystems and maintains a higher IWUEt. This suggests that the responses of each component flux of evapotranspiration should be analysed

  18. Steps Toward an Aerosol-Type Global Climate Data Record

    NASA Astrophysics Data System (ADS)

    Kahn, R. A.

    2015-12-01

    Earth-observing satellites have produced a global record of aerosol optical depth approaching two decades in length. However a global record of aerosol properties at the level-of-detail required for constraining aerosol radiative forcing, aerosol-cloud interaction assessments, and many air quality applications is as yet lacking. Some aerosol-type information is derived from surface-based photometers, and qualitative classification is possible under favorable conditions from MISR, POLDER, and CALIPSO. More detailed particle microphysical properties are obtained from in situ measurements, but sampling is poor, and the suite of coincident measurements required for many applications is rarely acquired. Aerosol transport models can connect remote-sensing and in situ observations to specific aerosol sources, and extrapolate limited observational sampling in space and time. The biggest challenges to producing a global aerosol-type data record are filling gaps in detailed observations, maintaining global observing capabilities, and putting the pieces together. Obtaining detailed particle properties is probably the leading observational gap. One simplifying factor is that, for a given aerosol source and season, aerosol amounts can vary, but the particle properties tend to be repeatable. So an aircraft payload designed and deployed frequently enough to acquire the PDFs of the key variables could fill this gap; the SAM-CAAM (Systematic Aircraft Measurements to Characterize Aerosol Air Masses) concept aims at meeting this objective. Such data would add value to the entire satellite data record, improving the aerosol property assumptions in retrievals, and providing quantitative mass extinction efficiencies to translate between remote-sensing optical constraints and the aerosol mass book-kept in climate models. This will also help putting the pieces together in other ways, by improving the connection between remote-sensing particle types and those defined in models. The

  19. A Climate Record of Enhanced Spatial Resolution Radiometer Data (Invited)

    NASA Astrophysics Data System (ADS)

    Paget, A. C.; Long, D. G.; Brodzik, M.

    2013-12-01

    Satellite radiometers, such SMMR, SSM/I, SSMIS, and AMSR, provide a multi-decadal time series of observations of the globe to support studies of climate change. Unfortunately, spatial resolution and sampling characteristics differ between sensors, which complicate compiling a single climate record. Resolution concerns can be ameliorated by reconstructing radiometer brightness temperature measurement (Tb) data onto daily-averaged compatible grids. We consider and contrast two widely used methods for image reconstruction: a radiometer version of the scatterometer image reconstruction (SIR) algorithm and Backus-Gilbert (BG). Both require detailed information about the spatial response function (antenna gain pattern) and the sampling geometry. We discuss considerations for an optimum gridding scheme based on the EASE-Grid 2.0 map projection. The EASE-Grid 2.0 simplifies the application of the Tb images in derived products since the reconstruction for each radiometer channel is implement on the same grid. This has the effect of optimally interpolating low-resolution measurements to locations of the highest resolution measurements. By employing reconstruction techniques rather than 'drop in the bucket' (dib) gridding, the effective resolution of the images is spatially enhanced compared to dib images, at the expense of additional computation required for the reconstruction processing. We evaluate the sensitivity of the radiometric accuracy of the resulting Tb images to uncertainties in the antenna gain pattern as well as variations in local-time-of-day. We briefly consider a number of applications of reconstructed Tb images. As part of the NASA-MEASUREs project 'An improved, enhanced-resolution, gridded passive microwave ESDR for monitoring cryospheric and hydrologic time series' we are processing all available satellite radiometer data to generate a consistently calibrated and processed time series of gridded images spanning from the 1970's to the present.

  20. What the Sunspot Record Tells Us About Space Climate

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Wilson, Robert M.

    2004-01-01

    The records concerning the number, sizes, and positions of sunspots provide a direct means of characterizing solar activity over nearly 400 years. Sunspot numbers are strongly correlated with modem measures of solar activity including: 10.7-cm radio flux, total irradiance, x-ray flares, sunspot area, the baseline level of geomagnetic activity, and the flux of galactic cosmic rays. The Group Sunspot Number provides information on 27 sunspot cycles, far more than any of the modem measures of solar activity, and enough to provide important details about long-term variations in solar activity or Space Climate. The sunspot record shows: 1) sunspot cycles have periods of 131 plus or minus 14 months with a normal distribution; 2) sunspot cycles are asymmetric with a fast rise and slow decline; 3) the rise time from minimum to maximum decreases with cycle amplitude; 4) large amplitude cycles are preceded by short period cycles; 5 ) large amplitude cycles are preceded by high minima; 6) although the two hemispheres remain linked in phase, there are significant asymmetries in the activity in each hemisphere; 7) the rate at which the active latitudes drift toward the equator is anti-correlated with the cycle period, 8) the rate at which the active latitudes drift toward the equator is positively correlated with the amplitude of the cycle after the next; 9) there has been a significant secular increase in the amplitudes of the sunspot cycles since the end of the Maunder Minimum (1715); and 10) there is weak evidence for a quasi-periodic variation in the sunspot cycle amplitudes with a period of about 90 years. These characteristics indicate that the next solar cycle should have a maximum smoothed sunspot number of about 1.45 plus or minus 30 in 2010 while the following cycle should have a maximum of about 70 plus or minus 30 in 2023.

  1. The EUMETSAT sea ice concentration climate data record

    NASA Astrophysics Data System (ADS)

    Tonboe, Rasmus T.; Eastwood, Steinar; Lavergne, Thomas; Sørensen, Atle M.; Rathmann, Nicholas; Dybkjær, Gorm; Toudal Pedersen, Leif; Høyer, Jacob L.; Kern, Stefan

    2016-09-01

    An Arctic and Antarctic sea ice area and extent dataset has been generated by EUMETSAT's Ocean and Sea Ice Satellite Application Facility (OSISAF) using the record of microwave radiometer data from NASA's Nimbus 7 Scanning Multichannel Microwave radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager and Sounder (SSMIS) satellite sensors. The dataset covers the period from October 1978 to April 2015 and updates and further developments are planned for the next phase of the project. The methodology for computing the sea ice concentration uses (1) numerical weather prediction (NWP) data input to a radiative transfer model for reduction of the impact of weather conditions on the measured brightness temperatures; (2) dynamical algorithm tie points to mitigate trends in residual atmospheric, sea ice, and water emission characteristics and inter-sensor differences/biases; and (3) a hybrid sea ice concentration algorithm using the Bristol algorithm over ice and the Bootstrap algorithm in frequency mode over open water. A new sea ice concentration uncertainty algorithm has been developed to estimate the spatial and temporal variability in sea ice concentration retrieval accuracy. A comparison to US National Ice Center sea ice charts from the Arctic and the Antarctic shows that ice concentrations are higher in the ice charts than estimated from the radiometer data at intermediate sea ice concentrations between open water and 100 % ice. The sea ice concentration climate data record is available for download at www.osi-saf.org, including documentation.

  2. Climatic influences on species: Evidence from the fossil record

    USGS Publications Warehouse

    Cronin, T. M.; Schneider, C.E.

    1990-01-01

    The detailed Neogene and Quaternary paleoclimatic reconstructions now available provide a means to test how species respond to environmental change. Paleontologic studies of marine organisms show that climatic change causes evolution (via cladogenesis and anagenesis), ecophenotypic variation, migration, morphologic stasis and extinction. Evolution during climatic change is a rare event relative to the number of climatic cycles that have occurred, but climate-related environmental barriers, usually temperature, may play an important role in the isolation of populations during allopatric speciation.

  3. A Guatemalan Speleothem Record Of Climate Of The Past Millennium

    NASA Astrophysics Data System (ADS)

    Miller, T.; Winter, A.; Burnett, A.; Haug, G. H.; Kelly, M. J.; Edwards, R.

    2012-12-01

    during the tilt interval. Other nearby climate records include stalagmites from Belize. The closest (Macal Chasm) speleothem record 30 km to the north reported a coarse δ18O resolution of 50 years, and suggest a long arid period ending about 1150 AD, and another centered about 1500 [mean δ18O -4‰]. The luminescence record [organic acid concentration indicating greater rainfall] of this speleothem supports the presence of the first long arid period, but not that of about 1500; a long modern drying began about 1800. A second stalagmite [Yok Balum] a similar distance to the south also recorded its "most pronounced dry period" between 1000-1100 AD, with elevated rainfall in about half of the subsequent millennium. The final years from 1840 to the present have been drier. A wider Caribbean comparison is possible with speleothem from the northern Yucatan and one as far east as Puerto Rico. Like that of GUXI-1, the period from 1100-1550 appears relatively wetter than preceding centuries, declining to a minimum about 1600, recovering by 1750, then dropping rapidly after 1800. Each of the three also experienced a brief wet interval about 1900. In summary, Central America and the Caribbean appeared to be recovering from dry conditions in the first centuries of the past millennium, encountered a deep rainfall decline in the middle followed by wetter conditions until ~1800, and since then have been experiencing increasing dryness.

  4. New approaches for extending the twentieth century climate record

    NASA Astrophysics Data System (ADS)

    Brönnimann, S.; Compo, G. P.; Sardeshmukh, P. D.; Jenne, R.; Sterin, A.

    Studying twentieth century climate is a key to understanding future climate change. Relatively little is still known, however, about climate variability in the first half of the century. Much could be learned from the relatively large climatic variations that occurred during that first half, including the decade-long “Dust Bowl” droughts of the 1930s and the warming of the Arctic from 1920 to 1945.Poor digital data availability prior to around 1948 has hindered previous work to understand these important climatic variations.

  5. Evaluation of Little Ice Age cooling in Western Central Andes, suggested by paleoELAs, in contrast with global warming since late 19th century deduced from instrumental records

    NASA Astrophysics Data System (ADS)

    Ubeda, Jose; Palacios, David; Campos, Néstor; Giraldez, Claudia; García, Eduardo; Quiros, Tatiana

    2015-04-01

    This paper attempts to evaluate climate cooling (°C) during the glacial expansion phases using the product GTV•ΔELA, where GTV is the vertical air temperature gradient (°C/m) and ΔELA (m) the difference in level observed between the Equilibrium Line Altitude (ELA) reconstructions for current and past glaciers. With this aim the Area x Altitude Balance Ratio-(AABR) method was used to produce reconstructions of present ELAs (2002-2010) and paleoELAs corresponding to the last glacier advance phase. The reconstructions were produced in three study areas located along a N-S transect of the western cordillera in the Central Andes: the south-western sector of the Nevado Hualcán (9°S, 77°W; Giráldez 2011); the southern slope of the Cordillera Pariaqaqa (12°S, 76°W; Quirós, 2013) and the NW, NE, SE and SW quadrants of the Nevado Coropuna (16°S, 72°W; García 2013; Úbeda 2011; Campos, 2012). The three mountains exceed 6000 m altitude, their summit areas are covered by glaciers, and on their slopes there are existing well-conserved moraines deposited by the last advances near the present front of the ice masses. Although there are no absolute dates to confirm this hypothesis, it has been assumed that the last glacial advances occurred during the Little Ice Age (LIA), which the oxygen isotopes of the Nevado Huascarán (9°S, 77°W) date to the period 1500-1890. For the Hualcán and Pariaqaqa the mean global value of the Earth's GTV (6.5°C/km) was used, considered valid for the Tropics. On the Coropuna a GTV=8.4°C/km was used, based on high resolution sensors installed in situ since 2007 (Úbeda 2011). This gradient is approaching the upper limit of the dry adiabatic gradient (9.8°C/km), as the Coropuna region is more arid than the other case study areas. The climate cooling estimates deduced from the product GTV•ΔELA were compared with the global warming shown by the 1880-2012 series, ΔT=0.85°C, and 1850/1900-2003/2012, ΔT=0.78°C. The differences are

  6. Beyond MODIS: Developing an aerosol climate data record

    NASA Astrophysics Data System (ADS)

    Levy, R. C.; Mattoo, S.; Munchak, L. A.; Patadia, F.; Laszlo, I.; Holz, R.

    2013-12-01

    As defined by the National Research Council, a climate data record (CDR) is a time series of measurements of sufficient length, consistency, and continuity to determine climate variability and change. As one of our most pressing research questions concerns changes in global direct aerosol radiative forcing (DARF), creating an aerosol CDR is of high importance. To reduce our uncertainties in DARF, we need uncertainty in global aerosol optical depth (AOD) reduced to ×0.02 or better, or about 10% of global mean AOD (~0.15-0.20). To quantify aerosol trends with significance, we also need a stable time series at least 20-30 years. By this Fall-2013 AGU meeting, the Moderate Resolution Imaging Spectrometer (MODIS) has been flying on NASA's Terra and Aqua satellites for 14 years and 11.5 years, respectively. During this time, we have fine-tuned the aerosol retrieval algorithms and data processing protocols, resulting in a well characterized product of aerosol optical depth (AOD). MODIS AOD has been extensively compared to ground-based sunphotometer data, showing per-retrieval expected error (EE) of ×(0.03 + 5%) over ocean, and has been generally adopted as a robust and stable environmental data record (EDR). With the 2011 launch of the Visible and Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP, we have begun a new aerosol time series. The VIIRS AOD product has stabilized to the point where, compared to ground-based AERONET sunphotometer, the VIIRS AOD is within similar EE envelope as MODIS. Thus, if VIIRS continues to perform as expected, it too can provide a robust and stable aerosol EDR. What will it take to stitch MODIS and VIIRS into a robust aerosol CDR? Based on the recent experience of MODIS 'Collection 6' development, there are many details of aerosol retrieval that each lead to ×0.01 uncertainties in global AOD. These include 'radiative transfer' assumptions such as calculations for gas absorption and sea-level Rayleigh optical depth, 'decision

  7. Detection and attribution of climate extremes in the observed record

    SciTech Connect

    Easterling, David R.; Kunkel, Kenneth E.; Wehner, Michael F.; Sun, Liqiang

    2016-01-18

    We present an overview of practices and challenges related to the detection and attribution of observed changes in climate extremes. Detection is the identification of a statistically significant change in the extreme values of a climate variable over some period of time. Issues in detection discussed include data quality, coverage, and completeness. Attribution takes that detection of a change and uses climate model simulations to evaluate whether a cause can be assigned to that change. Additionally, we discuss a newer field of attribution, event attribution, where individual extreme events are analyzed for the express purpose of assigning some measure of whether that event was directly influenced by anthropogenic forcing of the climate system.

  8. Progress on NOAA’s New Climate Data Record Initiatives (Invited)

    NASA Astrophysics Data System (ADS)

    Privette, J. L.; Bates, J. J.; Kearns, E. J.; Karl, T. R.

    2009-12-01

    The National Climatic Data Center (NCDC) recently began executing a new community-based Climate Data Records (CDR) program. The Program provides three core capabilities: 1) POES & GOES Multisatellite Climate Record Development, 2) NPOESS Preparatory Mission (NPP) Climate Record Pre-Processing, and 3) NPOESS/Jason Climate Record Production for “Remanifested” Instruments. In the past year, the Program conducted an open competition for CDR development activities. Following guidance from White House Office of Science and Technology Policy, the National Research Council and others, NOAA sought proposals to generalize mature research algorithms capable of producing Fundamental CDRs, or climate-quality calibration and geolocation of multi-decadal sensor data records, for the heritage instruments to those that will fly on the NPP, NPOESS, and Jason-series satellites. The Program also sought proposals to develop Thematic CDRs that support studies and climate services related to Earth’s Water and Energy Cycles. In this presentation, we will describe the initial CDR activities that are being funded from this competition, as well as systems in development to provide climate record pre-processing for NPP and NPOESS data. We will also describe the maturing Program framework, including the strategies for coding and development standards, community reviews, independent program oversight, research-to-operations algorithm migration and execution, and relationship to the new Cooperative Institute for Climate Satellites - North Carolina (CICS-NC). Finally, we will describe the out-year plans for the systematic and comprehensive production of CDRs which address the Global Climate Observing System’s (GCOS) list of Essential Climate Variables, and Climate Information Records (CIRs), which are time series derived from CDRs and related long-term measurements that provides specific information (e.g., drought area) about complex environmental phenomena in a manner useful to a variety

  9. Climate, atmosphere, and volatile inventory evolution: Polar processes, climate records, volatile inventories

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.

    1988-01-01

    Climate change on Mars was driven by long term changes in the solar luminosity, variations in the partitioning of volatiles between the atmosphere and near-surface reservoirs, and astronomical variations in axial and orbital properties. There are important parallels between these drives for Mars and comparable ones for Earth. In the early history of the solar system, the Sun's luminosity was 25 to 30 percent lower than its current value. It is suggested that an early benign climate on Earth was due to the presence of much more carbon dioxide in its atmosphere at these early times than currently resides there. Such a partitioning of carbon dioxide, at the expense of the carbonate rock reservoir, may have resulted from a more vigorous tectonic and volcanic style at early times. Such a line of reasoning may imply that much more carbon dioxide was present in the Martian atmosphere during the planet's early history than resides there today. It is now widely recognized that astronomical variations of the Earth's axial and orbital characteristics have played a dominant role in causing the succession of glacial and interglacial periods characterizing the last several million years. The magnitude of the axial and eccentricity variations are much larger for Mars than for Earth. Such changes on Mars could result in sizeable variations in atmospheric pressure, dust storm activity, and the stability of perennial carbon dioxide and water ice polar caps. These quasi-periodic climate changes occur on periods of 100,000 to 1,000,000 years and may be recorded in the sedimentary layers of the polar layered terrain.

  10. Climate, atmosphere, and volatile inventory evolution: Polar processes, climate records, volatile inventories

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.

    1988-01-01

    Climate change on Mars was driven by long term changes in the solar luminosity, variations in the partitioning of volatiles between the atmosphere and near-surface reservoirs, and astronomical variations in axial and orbital properties. There are important parallels between these drives for Mars and comparable ones for Earth. In the early history of the solar system, the Sun's luminosity was 25 to 30 percent lower than its current value. It is suggested that an early benign climate on Earth was due to the presence of much more carbon dioxide in its atmosphere at these early times than currently resides there. Such a partitioning of carbon dioxide, at the expense of the carbonate rock reservoir, may have resulted from a more vigorous tectonic and volcanic style at early times. Such a line of reasoning may imply that much more carbon dioxide was present in the Martian atmosphere during the planet's early history than resides there today. It is now widely recognized that astronomical variations of the Earth's axial and orbital characteristics have played a dominant role in causing the succession of glacial and interglacial periods characterizing the last several million years. The magnitude of the axial and eccentricity variations are much larger for Mars than for Earth. Such changes on Mars could result in sizeable variations in atmospheric pressure, dust storm activity, and the stability of perennial carbon dioxide and water ice polar caps. These quasi-periodic climate changes occur on periods of 100,000 to 1,000,000 years and may be recorded in the sedimentary layers of the polar layered terrain.

  11. Climatic controls on hurricane patterns: a 1200-y near-annual record from Lighthouse Reef, Belize

    NASA Astrophysics Data System (ADS)

    Denommee, K. C.; Bentley, S. J.; Droxler, A. W.

    2014-01-01

    Tropical cyclones (TCs) are powerful agents of destruction, and understanding climatic controls on TC patterns is of great importance. Over timescales of seasons to several decades, relationships among TC track, frequency, intensity and basin-scale climate changes are well documented by instrumental records. Over centuries to millennia, climate-shift influence on TC regimes remains poorly constrained. To better understand these relationships, records from multiple locations of TC strikes spanning millennia with high temporal resolution are required, but such records are rare. Here we report on a highly detailed sedimentary proxy record of paleo-TC strikes from the Blue Hole of Lighthouse Reef, Belize. Our findings provide an important addition to other high-resolution records, which collectively demonstrate that shifts between active and inactive TC regimes have occurred contemporaneously with shifts hemispheric-scale oceanic and atmospheric circulation patterns such as MDR SSTs and NAO mode, rather than with changes in local climate phenomena as has previously been suggested.

  12. Climatic controls on hurricane patterns: a 1200-y near-annual record from Lighthouse Reef, Belize.

    PubMed

    Denommee, K C; Bentley, S J; Droxler, A W

    2014-01-27

    Tropical cyclones (TCs) are powerful agents of destruction, and understanding climatic controls on TC patterns is of great importance. Over timescales of seasons to several decades, relationships among TC track, frequency, intensity and basin-scale climate changes are well documented by instrumental records. Over centuries to millennia, climate-shift influence on TC regimes remains poorly constrained. To better understand these relationships, records from multiple locations of TC strikes spanning millennia with high temporal resolution are required, but such records are rare. Here we report on a highly detailed sedimentary proxy record of paleo-TC strikes from the Blue Hole of Lighthouse Reef, Belize. Our findings provide an important addition to other high-resolution records, which collectively demonstrate that shifts between active and inactive TC regimes have occurred contemporaneously with shifts hemispheric-scale oceanic and atmospheric circulation patterns such as MDR SSTs and NAO mode, rather than with changes in local climate phenomena as has previously been suggested.

  13. Detection and attribution of climate extremes in the observed record

    DOE PAGES

    Easterling, David R.; Kunkel, Kenneth E.; Wehner, Michael F.; ...

    2016-01-18

    We present an overview of practices and challenges related to the detection and attribution of observed changes in climate extremes. Detection is the identification of a statistically significant change in the extreme values of a climate variable over some period of time. Issues in detection discussed include data quality, coverage, and completeness. Attribution takes that detection of a change and uses climate model simulations to evaluate whether a cause can be assigned to that change. Additionally, we discuss a newer field of attribution, event attribution, where individual extreme events are analyzed for the express purpose of assigning some measure ofmore » whether that event was directly influenced by anthropogenic forcing of the climate system.« less

  14. Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 years

    NASA Astrophysics Data System (ADS)

    Mills, K.; Ryves, D. B.; Anderson, N. J.; Bryant, C. L.; Tyler, J. J.

    2014-08-01

    Equatorial East Africa has a complex regional patchwork of climate regimes, sensitive to climate fluctuations over a variety of temporal and spatial scales during the late Holocene. Understanding how these changes are recorded in and interpreted from biological and geochemical proxies in lake sedimentary records remains a key challenge to answering fundamental questions regarding the nature, spatial extent and synchroneity of climatic changes seen in East African palaeo-records. Using a paired lake approach, where neighbouring lakes share the same geology, climate and landscape, it might be expected that the systems will respond similarly to external climate forcing. Sediment cores from two crater lakes in western Uganda spanning the last ~1000 years were examined to assess diatom community responses to late Holocene climate and environmental changes, and to test responses to multiple drivers using redundancy analysis (RDA). These archives provide annual to sub-decadal records of environmental change. Lakes Nyamogusingiri and Kyasanduka appear to operate as independent systems in their recording of a similar hydrological response signal via distinct diatom records. However, whilst their fossil diatom records demonstrate an individualistic, indirect response to external (e.g. climatic) drivers, the inferred lake levels show similar overall trends and reflect the broader patterns observed in Uganda and across East Africa. The lakes appear to be sensitive to large-scale climatic perturbations, with evidence of a dry Medieval Climate Anomaly (MCA; ca. AD 1000-1200). The diatom record from Lake Nyamogusingiri suggests a drying climate during the main phase of the Little Ice Age (LIA) (ca. AD 1600-1800), whereas the diatom response from the shallower Lake Kyasanduka is more complex (with groundwater likely playing a key role), and may be driven more by changes in silica and other nutrients, rather than by lake level. The sensitivity of these two Ugandan lakes to regional

  15. Challenges in assessing the contribution of climate change to observed record-breaking heat waves

    NASA Astrophysics Data System (ADS)

    Perlwitz, J.; Xu, T.; Quan, X.; Hoerling, M. P.; Dole, R. M.

    2013-12-01

    Record-setting heat waves have large impacts on public health and society due to increased mortality rate, wild fires, property damages and agricultural loss. There is increasing interest in understanding the causes of such extreme events including the role of climate change. We use the example of the link between atmospheric blocking frequency and summertime seasonal temperature extreme to address some challenges in determining the relative contributions of natural variability and climate change on the occurrence and magnitude of extreme climate-related events. We utilize the 62-year record of observational data from 1960 to 2011 and long integrations with the NCARs Community Climate System Model Version 4 (CCSM4). This climate model represents well atmospheric blocking frequency and related weather features over the European/Ural region. Both observations and long climate integrations suggest that seasonal temperature extremes over the Northern European/Ural region are strongly conditioned by blocking. We illustrate that one challenge in climate event attribution is related to the fact that very long records are necessary to sufficiently sample the frequency of occurrence of the principal driver of a record-setting climate event. We further illustrate that there is a strong regional dependence on how the link between blocking frequency and extreme temperature anomalies is modified due to climate change suggesting that event attribution results are often not transferable from one region to another.

  16. Climate Data Records (CDRs) for Ice Motion and Ice Age

    NASA Astrophysics Data System (ADS)

    Tschudi, M. A.; Fowler, C.; Maslanik, J. A.; Stroeve, J. C.

    2011-12-01

    Climate Data Records (CDRs) for remotely-sensed Arctic sea ice motion and sea ice age are under development by our group at the University of Colorado, Boulder. The ice motion product, archived at NSIDC, has a considerable history of use, while sea ice age is a relatively new product. Our technique to estimate sea ice motion utilizes images from SSM/I, as well as SMMR and the series of AVHRR sensors to estimate the daily motion of ice parcels. This method is augmented by incorporating ice motion observations from the network of drifting buoys deployed as part of the International Arctic Buoy Program. Our technique to calculate ice age relies on following the actual age of the ice for each ice parcel, categorizing the parcel as first-year ice, second-year, ice, etc. based on how many summer melt seasons the ice parcel survives. Both of these research-grade products have been interpolated onto 25x25 km grid points spanning the entire Arctic Ocean using the Equal-Area Scalable Earth (EASE) grid. Datasets generated from this program have shown that the Arctic ice cover has experienced a significant (> 70%) decline in multiyear ice over the last 20 years, leaving a younger ice cover in 2011. By comparing ice age derived by the Lagrangian tracking method to ice thickness estimated by Ice, Cloud and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) data, it is observed that ice age is linearly related to ice thickness, up to an age of 10 years. Therefore, the shift in dominance of multiyear ice to first-year ice relates to a significant thinning of the ice. This thinning is estimated to correspond to a 40% reduction in ice volume in the last 20 years. An ancillary dataset (APP-X) produced by the University of Wisconsin, Madison has been combined with the ice motion product to monitor the properties of the sea ice parcels tracked by the ice motion product. This dataset includes ice surface and 2-meter air temperature, albedo, downwelling shortwave

  17. Glacial-interglacial climate changes recorded by debris flow fan deposits, Owens Valley, California

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Roda-Boluda, Duna C.; Whittaker, Alexander C.

    2017-08-01

    It is hotly debated whether and how climate changes are recorded by terrestrial stratigraphy. Basin sediments produced by catchment-alluvial fan systems may record past climate over a variety of timescales, and could offer unique information about how climate controls sedimentation. Unfortunately, there are fundamental uncertainties about how climatic variables such as rainfall and temperature translate into sedimentological signals. Here, we examine 35 debris flow fan surfaces in Owens Valley, California, that record deposition throughout the past 125,000 years, during which climate has varied significantly. We show that the last full glacial-interglacial cycle is recorded with high fidelity by the grain size distributions of the debris flow deposits. These flows transported finer sediment during the cooler glacial climate, and became systematically coarser-grained as the climate warmed and dried. We explore the physical mechanisms that might explain this signal, and rule out changes in sediment supply through time. Instead, we propose that grain size records past changes in storm intensity, which is responsible for debris flow initiation in this area and is decoupled from average rainfall rates. This is supported by an exponential Clausius-Clapeyron-style scaling between grain size and temperature, and also reconciles with climate dynamics and the initiation of debris flows. The fact that these alluvial fans exhibit a strong, sustained sensitivity to orbital climate changes sheds new light on how eroding landscapes and their sedimentary products respond to climatic forcing. Finally, our findings highlight the importance of threshold-controlled events, such as storms and debris flows, in driving erosion and sedimentation at the Earth's surface in response to climate change.

  18. Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 yr

    NASA Astrophysics Data System (ADS)

    Mills, K.; Ryves, D. B.; Anderson, N. J.; Bryant, C. L.; Tyler, J. J.

    2013-09-01

    Equatorial East Africa has a complex, regional patchwork of climate regimes, with multiple interacting drivers. Recent studies have focussed on large lakes and reveal signals that are smoothed in both space and time, and, whilst useful at a continental scale, are of less relevance when understanding short-term, abrupt or immediate impacts of climate and environmental changes. Smaller-scale studies have highlighted spatial complexity and regional heterogeneity of tropical palaeoenvironments in terms of responses to climatic forcing (e.g. the Little Ice Age [LIA]) and questions remain over the spatial extent and synchroneity of climatic changes seen in East African records. Sediment cores from paired crater lakes in western Uganda were examined to assess ecosystem response to long-term climate and environmental change as well as testing responses to multiple drivers using redundancy analysis. These archives provide annual to sub-decadal records of environmental change. The records from the two lakes demonstrate an individualistic response to external (e.g. climatic) drivers, however, some of the broader patterns observed across East Africa suggest that the lakes are indeed sensitive to climatic perturbations such as a dry Mediaeval Climate Anomaly (MCA; 1000-1200 AD) and a relatively drier climate during the main phase of the LIA (1500-1800 AD); though lake levels in western Uganda do fluctuate. The relationship of Ugandan lakes to regional climate drivers breaks down c. 1800 AD, when major changes in the ecosystems appear to be a response to sediment and nutrient influxes as a result of increasing cultural impacts within the lake catchments. The data highlight the complexity of individual lake response to climate forcing, indicating shifting drivers through time. This research also highlights the importance of using multi-lake studies within a landscape to allow for rigorous testing of climate reconstructions, forcing and ecosystem response.

  19. 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

  20. Abundant climatic information in water stable isotope record from a maritime glacier on southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhao, Huabiao; Xu, Baiqing; Li, Zhen; Wang, Mo; Li, Jiule; Zhang, Xiaolong

    2017-02-01

    Climatic significance of ice core stable isotope record in the Himalayas and southern Tibetan Plateau (TP), where the climate is alternately influenced by Indian summer monsoon and mid-latitude westerlies, is still debated. A newly drilled Zuoqiupu ice core from a temperate maritime glacier on the southeastern TP covering 1942-2011 is investigated in terms of the relationships between δ18O and climate parameters. Distinct seasonal variation of δ18O is observed due to high precipitation amount in this area. Thus the monsoon (June to September) and non-monsoon (October to May) δ18O records are reconstructed, respectively. The temperature effect is identified in the annual δ18O record, which is predominantly contributed by temperature control on the non-monsoon precipitation δ18O record. Conversely, the negative correlation between annual δ18O record and precipitation amount over part of Northeast India is mostly contributed by the monsoon precipitation δ18O record. The variation of monsoon δ18O record is greatly impacted by the Indian summer monsoon strength, while that of non-monsoon δ18O record is potentially associated with the mid-latitude westerly activity. The relationship between Zuoqiupu δ18O record and Sea Surface Temperature (SST) is found to be inconsistent before and after the climate shift of 1976/1977. In summer monsoon season, the role of SST in the monsoon δ18O record is more important in eastern equatorial Pacific Ocean and tropical Indian Ocean before and after the shift, respectively. In non-monsoon season, however, the Atlantic Multidecadal Oscillation has a negative impact before but positive impact after the climate shift on the non-monsoon δ18O record.

  1. Forest fire and climate change in western North America: insights from sediment charcoal records.

    Treesearch

    Daniel G Gavin; Douglas J Hallett; Feng Sheng Hu; Kenneth P Lertzman; Susan J Prichard; Kendrick J Brown; Jason A Lynch; Patrick Bartlein; David L. Peterson

    2007-01-01

    Millennial-scale records of forest fire provide important baseline information for ecosystem management, especially in regions with too few recent fires to describe the historical range of variability. Charcoal records from lake sediments and soil profiles are well suited for reconstructing the incidence of past fire and its relationship to changing climate and...

  2. The GOME-type Total Ozone Essential Climate Variable (GTO-ECV) data record from the ESA Climate Change Initiative

    NASA Astrophysics Data System (ADS)

    Coldewey-Egbers, M.; Loyola, D. G.; Koukouli, M.; Balis, D.; Lambert, J.-C.; Verhoelst, T.; Granville, J.; van Roozendael, M.; Lerot, C.; Spurr, R.; Frith, S. M.; Zehner, C.

    2015-09-01

    We present the new GOME-type Total Ozone Essential Climate Variable (GTO-ECV) data record which has been created within the framework of the European Space Agency's Climate Change Initiative (ESA-CCI). Total ozone column observations - based on the GOME-type Direct Fitting version 3 algorithm - from GOME (Global Ozone Monitoring Experiment), SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY), and GOME-2 have been combined into one homogeneous time series, thereby taking advantage of the high inter-sensor consistency. The data record spans the 15-year period from March 1996 to June 2011 and it contains global monthly mean total ozone columns on a 1°× 1° grid. Geophysical ground-based validation using Brewer, Dobson, and UV-visible instruments has shown that the GTO-ECV level 3 data record is of the same high quality as the equivalent individual level 2 data products that constitute it. Both absolute agreement and long-term stability are excellent with respect to the ground-based data, for almost all latitudes apart from a few outliers which are mostly due to sampling differences between the level 2 and level 3 data. We conclude that the GTO-ECV data record is valuable for a variety of climate applications such as the long-term monitoring of the past evolution of the ozone layer, trend analysis and the evaluation of chemistry-climate model simulations.

  3. The GOME-type Total Ozone Essential Climate Variable (GTO-ECV) data record from the ESA Climate Change Initiative

    NASA Astrophysics Data System (ADS)

    Coldewey-Egbers, M.; Loyola, D. G.; Koukouli, M.; Balis, D.; Lambert, J.-C.; Verhoelst, T.; Granville, J.; van Roozendael, M.; Lerot, C.; Spurr, R.; Frith, S. M.; Zehner, C.

    2015-05-01

    We present the new GOME-type Total Ozone Essential Climate Variable (GTO-ECV) data record which has been created within the framework of the European Space Agency's Climate Change Initiative (ESA-CCI). Total ozone column observations - based on the GOME-type Direct Fitting version 3 algorithm - from GOME (Global Ozone Monitoring Experiment), SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY), and GOME-2 have been combined into one homogeneous time series, thereby taking advantage of the high inter-sensor consistency. The data record spans the 15-year period from March 1996 to June 2011 and it contains global monthly mean total ozone columns on a 1° × 1° grid. Geophysical ground-based validation using Brewer, Dobson, and UV-visible instruments has shown that the GTO-ECV level 3 data record is of the same high quality as the equivalent individual level 2 data products that constitute it. Both absolute agreement and long-term stability are excellent with respect to the ground-based data, for almost all latitudes apart from a few outliers which are mostly due to sampling differences between the level 2 and level 3 data. We conclude that the GTO-ECV data record is valuable for a variety of climate applications such as the long-term monitoring of the past evolution of the ozone layer, trend analysis and the evaluation of Chemistry-Climate Model simulations.

  4. Abrupt Climate Events Recorded in Chinese and Central Asian Loess Sequences

    NASA Astrophysics Data System (ADS)

    Machalett, Bjoern; Oches, Eric A.; Haam, Eddie; Lai, Zhongping; Endlicher, Wilfried

    2013-04-01

    Past climate dynamics associated with the Eurasian continent have been extensively studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of investigation . While western Atlantic polar and tropical air masses penetrate into the continent and are transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmospheric and oceanic processes and regulate teleconnection patterns across the Northern Hemisphere. This paper utilizes high resolution particle size data from the Central Asian loess sequence at Remisowka, Kazakhstan, and the long studied, monsoon-influenced Chinese loess sequence at Xifeng, to reconstruct past atmospheric circulation and aeolian dust dynamics within interior Eurasia since the last interglacial period. The observed dynamics in aeolian dust transport closely mirror d18O and fine dust variations measured in Greenland ice cores, suggesting a correlation with short-term climate oscillations (DO events) recorded therein. An Asian origin of fine aeolian dust preserved in Greenland ice cores has been discussed previously, and recent papers reveal a close link between Asian aeolian dust dynamics and DO events recorded in Greenland ice cores. In this context, data presented here represent the first Central and East Asian aeolian dust records in which DO events are recorded, providing a means to test hypothesized links between short-term climate variability recorded in Greenland and associated climate dynamics at Asian dust source areas. Ultimately, the data extend existing hypotheses, suggesting that the Central and High Asian mountains are a crucial element within the sensitive glacier-desert-dust response system in interior Eurasia and may be considered a pacemaker

  5. Abrupt Climate Events Recorded in Chinese and Central Asian Loess Sequences

    NASA Astrophysics Data System (ADS)

    Machalett, B.; Oches, E. A.; Haam, E. K.; Lai, Z.; Endlicher, W.

    2013-12-01

    Past climate dynamics associated with the Eurasian continent have been extensively studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of investigation . While western Atlantic polar and tropical air masses penetrate into the continent and are transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmospheric and oceanic processes and regulate teleconnection patterns across the Northern Hemisphere. This paper utilizes high resolution particle size data from the Central Asian loess sequence at Remisowka, Kazakhstan, and the long studied, monsoon-influenced Chinese loess sequence at Xifeng, to reconstruct past atmospheric circulation and aeolian dust dynamics within interior Eurasia since the last interglacial period. The observed dynamics in aeolian dust transport closely mirror d18O and fine dust variations measured in Greenland ice cores, suggesting a correlation with short-term climate oscillations (DO events) recorded therein. An Asian origin of fine aeolian dust preserved in Greenland ice cores has been discussed previously, and recent papers reveal a close link between Asian aeolian dust dynamics and DO events recorded in Greenland ice cores. In this context, data presented here represent the first Central and East Asian aeolian dust records in which DO events are recorded, providing a means to test hypothesized links between short-term climate variability recorded in Greenland and associated climate dynamics at Asian dust source areas. Ultimately, the data extend existing hypotheses, suggesting that the Central and High Asian mountains are a crucial element within the sensitive glacier-desert-dust response system in interior Eurasia and may be considered a pacemaker

  6. The insect response to climate change: Perspectives from the Quaternary record

    SciTech Connect

    Ashworth, A.C.; Schwert, D.P. . Quaternary Entomology Lab.)

    1993-03-01

    Data based on museum collections of insects are generally inadequate to answer questions related to the response of insects to recent and potential changes in climate. The most important source of information for this purpose is the late Quaternary fossil record. Abundant, well-preserved, [sup 14]C-dated assemblages of insect fossils provide information with which to answer the following questions: (1) will climate change result in speciation--all evidence suggests that species are constant through the climate changes of the late Quaternary, future climate change would not be expected to result in accelerated rates of speciation; (2) will climate change result in extinction--few species became extinct as a result of the large-scale changes in climate and physical environment during the quaternary, although large-scale extirpation might occur, future climate change would not be expected to result in widespread extinction of species; (3) will climate change result in changes in geographic distribution--species survived late Quaternary climatic change through the ability of individuals to disperse into suitable habitats. The result was large changes in geographic distribution of species, as exemplified by the succession of faunal changes that occurred in response to the climatic changes of the late Wisconsinan in the midcontinent, future climate change would be expected to result in significant range changes of species.

  7. Holocene Climate and Catchment-Specific Responses to Climate Change, Recorded in a Transect of Icelandic Lakes

    NASA Astrophysics Data System (ADS)

    Geirsdottir, A.; Axford, Y.; Florian, C. R.; Miller, G. H.; Crump, S. E.; Larsen, D. J.; Olafsdóttir, S.; Thordarson, T.; Blair, C.

    2015-12-01

    Holocene paleoclimate reconstructions from the northern North Atlantic landmasses exhibit greater responses to climate forcings than other Arctic regions presumably tied to changes in North Atlantic ocean-atmosphere circulation. Here we present an overview of high-resolution, precisely dated and PSV synchronized Holocene lake sediment records on Iceland, where we employ diverse proxies at sites spanning a broad modern climate gradient, from the presently glaciated highlands to the coastal lowlands. Despite substantial differences in catchment specific processes that influence each lake record, the multi-proxy reconstructions over the last 10 ka show remarkably consistent trends, especially throughout the mid to late Holocene cooling related to the slow decrease in summer insolation. Of particular note are highly non-linear abrupt departures of centennial scale summer cold periods such as at 5.5 ka, ~4.2 ka; ~3.0 ka, ~1.5 ka, 0.7 ka, and 0.2 ka. Some of the abrupt shifts may be related to Icelandic volcanism influencing catchment stability, but the lack of a full recovery to pre-existing values after the perturbation suggests increased periglacial activity, decreased vegetation cover, and glacier growth in Iceland. That these shifts reflect regional climate changes is also supported by contemporaneous shifts documented elsewhere in the northern North Atlantic region. Although timing and abruptness of these shifts is similar between our Icelandic lake records, their magnitude can differ substantially. Regional-scale factors such as volcanism likely modulate climatic responses to radiative forcing; and at the same time, local watershed characteristics like vegetation cover and soil properties produce site-specific environmental responses to climate change. Our Icelandic lake records provide opportunities to observe the precise timing of local climate shifts and corresponding environmental responses, and thus to disentangle these effects.

  8. Satellite-based climate data records of surface solar radiation from the CM SAF

    NASA Astrophysics Data System (ADS)

    Trentmann, Jörg; Cremer, Roswitha; Kothe, Steffen; Müller, Richard; Pfeifroth, Uwe

    2017-04-01

    The incoming surface solar radiation has been defined as an essential climate variable by GCOS. Long term monitoring of this part of the earth's energy budget is required to gain insights on the state and variability of the climate system. In addition, climate data sets of surface solar radiation have received increased attention over the recent years as an important source of information for solar energy assessments, for crop modeling, and for the validation of climate and weather models. The EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF) is deriving climate data records (CDRs) from geostationary and polar-orbiting satellite instruments. Within the CM SAF these CDRs are accompanied by operational data at a short time latency to be used for climate monitoring. All data from the CM SAF is freely available via www.cmsaf.eu. Here we present the regional and the global climate data records of surface solar radiation from the CM SAF. The regional climate data record SARAH (Surface Solar Radiation Dataset - Heliosat, doi: 10.5676/EUM_SAF_CM/SARAH/V002) is based on observations from the series of Meteosat satellites. SARAH provides 30-min, daily- and monthly-averaged data of the effective cloud albedo, the solar irradiance (incl. spectral information), the direct solar radiation (horizontal and normal), and the sunshine duration from 1983 to 2015 for the full view of the Meteosat satellite (i.e, Europe, Africa, parts of South America, and the Atlantic ocean). The data sets are generated with a high spatial resolution of 0.05° allowing for detailed regional studies. The global climate data record CLARA (CM SAF Clouds, Albedo and Radiation dataset from AVHRR data, doi: 10.5676/EUM_SAF_CM/CLARA_AVHRR/V002) is based on observations from the series of AVHRR satellite instruments. CLARA provides daily- and monthly-averaged global data of the solar irradiance (SIS) from 1982 to 2015 with a spatial resolution of 0.25°. In addition to the solar surface

  9. Climate forcing and Neanderthal extinction in Southern Iberia: insights from a multiproxy marine record

    NASA Astrophysics Data System (ADS)

    Jiménez-Espejo, Francisco J.; Martínez-Ruiz, Francisca; Finlayson, Clive; Paytan, Adina; Sakamoto, Tatsuhiko; Ortega-Huertas, Miguel; Finlayson, Geraldine; Iijima, Koichi; Gallego-Torres, David; Fa, Darren

    2007-04-01

    Paleoclimate records from the western Mediterranean have been used to further understand the role of climatic changes in the replacement of archaic human populations inhabiting South Iberia. Marine sediments from the Balearic basin (ODP Site 975) was analysed at high resolution to obtain both geochemical and mineralogical data. These data were compared with climate records from nearby areas. Baexcces was used to characterize marine productivity and then related to climatic variability. Since variations in productivity were the consequence of climatic oscillations, climate/productivity events have been established. Sedimentary regime, primary marine productivity and oxygen conditions at the time of population replacement were reconstructed by means of a multiproxy approach. Climatic/oceanographic variations correlate well with Homo spatial and occupational patterns in Southern Iberia. It was found that low ventilation (U/Th), high river supply (Mg/Al), low aridity (Zr/Al) and low values of Baexcess coefficient of variation, may be linked with Neanderthal hospitable conditions. We attempt to support recent findings which claim that Neanderthals populations continued to inhabit southern Iberia between 30 and ˜28 ky cal BP and that this persistence was due to the specific characteristics of South Iberian climatic refugia. Comparisons of our data with other marine and continental records appear to indicate that conditions in South Iberia were highly inhospitable at ˜24 ky cal BP. Thus, it is proposed that the final disappearance of Neanderthals in this region could be linked with these extreme conditions.

  10. Smoothing of millennial scale climate variability in European Loess (and other records)

    NASA Astrophysics Data System (ADS)

    Zeeden, Christian; Obreht, Igor; Hambach, Ulrich; Veres, Daniel; Marković, Slobodan B.; Lehmkuhl, Frank

    2017-04-01

    Millennial scale climate variability is seen in various records of the northern hemisphere in the last glacial cycle, and their expression represents a correlation tool beyond the resolution of e.g. luminescence dating. Highest (correlative) dating accuracy is a prerequisite of comparing different geoarchives, especially when related to archaeological findings. Here we attempt to constrain the timing of loess geoarchives representing the environmental context of early humans in south-eastern Europe, and discuss the challenge of dealing with smoothed records. In this contribution, we present rock magnetic and grain size data from the Rasova loess record in the Lower Danube basin (Romania), showing millennial scale climate variability. Additionally, we summarize similar data from the Lower and Middle Danube Basins. A comparison of these loess data and reference records from Greenland ice cores and the Mediterranean-Black Sea region indicates a rather unusual expression of millennial scale climate variability recorded in loess. To explain the observed patterns, we experiment with low-pass filters of reference records to simulate a signal smoothing by natural processes such as e.g. bioturbation and pervasive diagenesis. Low-pass filters avoid high frequency oscillations and focus on the longer period (lower frequency) variability, here using cut-off periods from 1-15 kyr. In our opinion low-pass filters represent simple models for the expression of millennial scale climate variability in low sedimentation environments, and in sediments where signals are smoothed by e.g. bioturbation and/or diagenesis. Using different low-pass filter thresholds allows us to (a) explain observed patterns and their relation to millennial scale climate variability, (b) propose these filtered/smoothed signals as correlation targets for records lacking millennial scale recording, but showing smoothed climate variability on supra-millennial scales, and (c) determine which time resolution

  11. Last Millennium External Forcing Undetectable in Coral Records of Central Pacific Climate

    NASA Astrophysics Data System (ADS)

    Dee, S.; Emile-Geay, J.; Cobb, K. M.; Ault, T.

    2016-12-01

    The El Niño-Southern Oscillation (ENSO) is a primary driver of global climate variability; as such, characterizing past ENSO variability and assessing its response to changes in radiative forcing is of paramount importance for prediction given continued anthropogenic forcing. To investigate the sensitivity of tropical Pacific climate and external forcing - specifically solar and volcanic forcing - we probe a new, monthly-resolved fossil coral record from Palmyra Island spanning from 1150-1460AD together with previously published records from this site. Such records are well-established proxies for ENSO and decadal-scale Pacific climate variability, making them ideal candidates for investigating the relationship between natural external forcing and tropical Pacific climate response. In particular, recent modeling studies suggest that cooling associated with explosive volcanism produces an El Niño-like response in the tropical Pacific in the following year. We investigate the real-world applicability of this response using the new coral record, multiple volcanic forcing reconstructions, Superposed Epoch Analysis, and GCM simulations from the CESM Last-Millennium Ensemble. Using the same toolkit, we evaluate correlations between the coral data and solar forcing variability using a suite of solar forcing reconstructions and singular spectrum analysis. To account for uncertainties in the coral data, we use a proxy system model for coral δ18O and explicitly model coral dating errors. We find no evidence that central tropical Pacific sea surface temperatures, as recorded by Palmyra Island corals, are sensitive to solar and volcanic forcing over the past millennium. Our results imply that if the dynamical links observed in climate models do exist in the real world, their impact is small relative to natural variability. We discuss the implications of our findings on the simulation of ENSO in coupled climate models and the detectability of externally forced signals in

  12. Deconstructing interdecadal climate variability using a network of paleoclimate proxy records

    NASA Astrophysics Data System (ADS)

    Young, S. K.; Okumura, Y.; Partin, J. W.

    2015-12-01

    Interdecadal climate variability is of marked socioeconomic importance around the world and recent studies suggest that it may also affect the rate of global warming (Here, interdecadal variability refers broadly to variability on time scales of 10-100 years.) Our understanding of interdecadal climate variability is at present limited by a short instrumental record constituting only a few cycles. To improve climate prediction over the coming decades, a better understanding of interdecadal climate variability is critical. An increasing number of annually resolved paleoclimate proxy records present a means to extend the temporal coverage of the record of interdecadal variability. In so doing, we may begin to address the following questions. What were the amplitudes and timescales of known modes of interdecadal variability, such as the Interdecadal Pacific Oscillation (IPO) or the Atlantic Multidecadal Oscillation (AMO), before the instrumental era? Is interdecadal variability in different ocean basins related? Are there any yet undiscovered modes of interdecadal variability? To answer these questions we construct a network of annually-resolved proxy records collected from the NOAA paleoclimatology data archive and perform various statistical analyses without any a priori assumptions about modes of variability. During the instrumental period, this network reasonably captures the observed interdecadal variability in the Atlantic and Pacific Oceans. We are currently extending these analyses beyond the instrumental record to reconstruct past variability. The new insight gained from the proxies will be assessed through the analysis of CMIP5 climate model simulations.

  13. What can we learn from the Paleo-Records about Future Arctic Climate Change?

    NASA Astrophysics Data System (ADS)

    Tremblay, B.; Huard, D. B.; Schmidt, G. A.; de Vernal, A.

    2014-12-01

    The Coupled Model Intercomparison Project, Phase 5 (CMIP5), include historical simulations from the 20th century, future climate simulations following different Representative Concentration Pathways (RCPs) for the 21st Century and beyond, and, for the first time in CMIP, three sets of paleo-climate simulations of the recent past for which more paleo-proxi-data exist. We use simulations of the Mid-Holocene (MH) climate (6K BP) from General Circulation Models participating in CMIP5 to constrain future projections of Arctic climate change by the same models. During the Mid-Holocene, the Arctic received approximately 50 W/m2 more solar radiation at the top of the atmosphere during summer, a similar increase to what is projected from greenhouse gas forcing for the middle of the 21st century. The constraint in our analysis arise from a measure of the ability of GCMs to hindcast MH climate using a suite of both land paleo-records - which are much more abundant for high latitudes than ocean proxy - and ocean paleo-record. Results show that GCMs with skill at simulating the MH climate and today's climate give more realistic future projections of the sea ice decline in forced climate simulations of the 21st century participating in the IPCC-AR5.

  14. The secret lives of corals: Climate records from coral chemistry

    SciTech Connect

    Beck, J.W.; Smoker, M.; Burr, G.

    1995-12-01

    Corals can provide archives of a diverse suite of information about the ocean surface mixed layer, including records of ocean surface temperature (via coral Sr/Ca or U/Ca measurements), salinity (via {gamma}{sup 18}O measurements), biologic activity (via {gamma}{sup 13}C measurements), and ocean/atmosphere CO{sub 2} exchange rates (via {sup 14}C/{sup 12}C measurements). Recently, it has been shown that corals record evidence of large seasonal oscillations in {sup 14}C concentration of the ocean surface mixed layer, and that such oscillations are modulated by ENSO. These oscillations are related to seasonal changes in the surface wind velocity field, changes in the patterns of regional upwelling, as well as seasonal changes in the strength of the thermocline. High frequency AMS {sup 14}C analyses of corals shows that ENSO events can dramatically diminish the annual range in ocean mixed layer {sup 14}C concentration in this region. Our work on a coral from Vanuatu in the western equatorial Pacific also documents large seasonal changes in {sup 14}C concentration (3-5%) as well as ENSO modulation of these variations during the 82-83 ENSO event.

  15. Millennial- to century-scale variability in Gulf of Mexico Holocene climate records

    USGS Publications Warehouse

    Poore, R.Z.; Dowsett, H.J.; Verardo, S.; Quinn, T.M.

    2003-01-01

    Proxy records from two piston cores in the Gulf of Mexico (GOM) provide a detailed (50-100 year resolution) record of climate variability over the last 14,000 years. Long-term (millennial-scale) trends and changes are related to the transition from glacial to interglacial conditions and movement of the average position of the Intertropical Convergence Zone (ITCZ) related to orbital forcing. The ??18O of the surface-dwelling planktic foraminifer Globigerinoides ruber show negative excursions between 14 and 10.2 ka (radiocarbon years) that reflect influx of meltwater into the western GOM during melting of the Laurentide Ice Sheet. The relative abundance of the planktic foraminifer Globigerinoides sacculifer is related to transport of Caribbean water into the GOM. Maximum transport of Caribbean surface waters and moisture into the GOM associated with a northward migration of the average position of the ITCZ occurs between about 6.5 and 4.5 ka. In addition, abundance variations of G. sacculifer show century-scale variability throughout most of the Holocene. The GOM record is consistent with records from other areas, suggesting that century-scale variability is a pervasive feature of Holocene climate. The frequency of several cycles in the climate records is similar to cycles identified in proxy records of solar variability, indicating that at least some of the century-scale climate variability during the Holocene is due to external (solar) forcing.

  16. Assessing the continuity of the blue ice climate record at Patriot Hills, Horseshoe Valley, West Antarctica

    NASA Astrophysics Data System (ADS)

    Winter, Kate; Woodward, John; Dunning, Stuart A.; Turney, Chris S. M.; Fogwill, Christopher J.; Hein, Andrew S.; Golledge, Nicholas R.; Bingham, Robert G.; Marrero, Shasta M.; Sugden, David E.; Ross, Neil

    2016-03-01

    We use high-resolution ground-penetrating radar (GPR) to assess the continuity of the Blue Ice Area (BIA) horizontal climate record at Patriot Hills, Horseshoe Valley, West Antarctica. The sequence contains three pronounced changes in deuterium isotopic values at ~18 cal ka, ~12 cal ka, and ~8 cal ka. GPR surveys along the climate sequence reveal continuous, conformable dipping isochrones, separated by two unconformities in the isochrone layers, which correlate with the two older deuterium shifts. We interpret these unconformities as discontinuities in the sequence, rather than direct measures of climate change. Ice sheet models and Internal Layer Continuity Index plots suggest that the unconformities represent periods of erosion occurring, as the former ice surface was scoured by katabatic winds in front of mountains at the head of Horseshoe Valley. This study demonstrates the importance of high-resolution GPR surveys for investigating both paleoflow dynamics and interpreting BIA climate records.

  17. A lacustrine carbonate record of Holocene seasonality and climate

    USGS Publications Warehouse

    Wittkop, Chad A.; Teranes, Jane L.; Dean, Walter E.; Guilderson, Thomas P.

    2009-01-01

    Annually laminated (varved) Holocene sediments from Derby Lake, Michigan, display variations in endogenic calcite abundance reflecting a long-(millennial-scale) decrease in burial punctuated with frequent short- (decadal-scale) oscillations due to carbonate dissolution. Since 6000 cal yr B.P., sediment carbonate abundance has followed a decreasing trend while organic-carbon abundance has increased. The correlation between organic-carbon abundance and the sum of March-April-October-November insolation has an r2 value of 0.58. We interpret these trends to represent a precession-driven lengthening of the Holocene growing season that has reduced calcite burial by enhancing net annual organic-matter production and associated calcite dissolution. Correlations with regional paleoclimate records suggest that changes in temperature and moisture balance have impacted the distribution of short- oscillations in carbonate and organic-matter abundance superimposed on the precession-driven trends.

  18. NOAA SBUV(/2) Ozone Merged Cohesive Climate Data Record

    NASA Astrophysics Data System (ADS)

    Long, C. S.; Wild, J.; Beach, E.

    2015-12-01

    The Solar Backscatter UltraViolet (SBUV) instrument flown on Nimbus-7 and the SBUV/2 instruments flown on the NOAA 09, 11, 14, 16, 17, 18, and 19 satellites have produced a continuous record of nadir profile ozone observations from 1979 through the present (2015). NASA's latest reprocessing of the individual satellite data sets have created a version 8.6 which strives to eliminate inter-satellite biases. However, there still are differences in data quality between the instruments flown on the various satellites. Our goal is to remove the remaining differences. Adjustments are made to individual instrument records based on periods of overlap, to account for any variations in the observed annual cycle as well as an overall bias. Rather than an average of all available observations, a single satellite is chosen for each period based on the best latitudinal coverage allowing the clean retention of satellite characteristics such as time of measurement, solar zenith angle, etc. to be identified with an ozone value. Measurements from NOAA-9 are included in a short period to allow greater global coverage in the bridge from NOAA-11 to -14. Measurements from the NASA BUV on Nimbus-4 are excluded since there is no overlap with the subsequent instruments. We will present examples of the methodology to adjust overlapping satellites. We will contrast the original unadjusted data set with our final data set. We will present results from applying a piece-wise linear trend to the data set dividing the depletion period from the recovery period. These results will be shown in comparison with other trend results from other ozone profile datasets.

  19. The Evolution of Weather Records Archival at NOAA's National Climatic Data Center

    NASA Astrophysics Data System (ADS)

    Cooper, J.

    2011-12-01

    Long-term datasets are among the most essential tools for climate research. As these datasets grow, weather and climate archives face a significant challenge. The research community expects records to be retained in perpetuity, necessitating the vast accumulation of original records to support the longterm datasets. NOAA's National Climatic Data Center (NCDC) is meeting this expectation. NCDC is communicating the importance of permanent retention to the National Archives and Records Administration (NARA), and ensuring that permanent retention is a reasonable and practical requirement. Antiquated retention requirements based on the limitations of the pre-digital age will be discussed, as will the need to ensure that digital data remains readable and independently understandable.

  20. Glacial-Interglacial Climate Changes Recorded by Debris Flow Grain Size, Eastern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    D'Arcy, M. K.; Whittaker, A. C.; Roda Boluda, D. C.

    2015-12-01

    Uncertainties remain about the sensitivity of eroding landscapes to climate changes over a range of frequencies and amplitudes. Numerical models suggest that simple catchment-fan systems should be responsive to glacial-interglacial climate cycles, recording them in both sediment flux and the grain size distribution of their deposits. However these models are largely untested and the propagation of climatic signals through simple sediment routing systems remains contentious. Here, we present detailed sedimentological data from 8 debris flow fans in Owens Valley, eastern California. These fans have an exceptionally well-constrained depositional record spanning the last 120 ka, which we use to examine how sediment export has varied as a function of high-amplitude climate changes. We find a strong and sustained relationship between debris flow grain size and paleoclimate proxies over an entire glacial-interglacial cycle, with significantly coarser-grained deposits correlated with warm and dry conditions. Our data suggest these systems are highly reactive to climate forcing, with a short response timescale of <10 ka and no evidence of signal buffering, which we interpret to be driven by rapid sediment transfer from source to sink. We demonstrate that debris flow grain size follows an exponential relationship with temperature, coarsening at a rate of ~10 % per °C. Using this observation, and a known relationship between temperature and storm intensity, we propose that the climate signal recorded in these fan deposits captures changing storm intensity during the last glacial-interglacial cycle. This study offers a direct test of existing models of catchment-fan systems, confirming that glacial-interglacial climate changes can be clearly expressed in their grain size records. Our results also suggest that these debris flow deposits contain a high-resolution, testable record of past storm intensity, and that storminess is the primary control on their sedimentological

  1. Comparison of St. Elias Ice Core Accumulation Records and Their Relationships to Climate Indices

    NASA Astrophysics Data System (ADS)

    Yalcin, K.; Osterberg, E.; Mayewski, P.; Wake, C.; Kreutz, K.; Holdsworth, G.

    2006-12-01

    Recently recovered ice cores from the St Elias Mountains (Yukon) spanning an elevation range of three (Eclipse Icefield) to more than five kilometers (Mount Logan) offer a unique three-dimensional view of paleoclimate and environmental change in the North Pacific region. The record of net accumulation as deduced from the reconstruction of observed annual layer thicknesses in these cores offers a direct view of moisture flux at various altitudes in the St. Elias. However, a potentially large uncertainty in the representativeness of ice core accumulation records exists due to spatial variability in snow accumulation rates. The availability of multiple cores allows us to address this issue. Accumulation records from Eclipse (three cores) are highly reproducible with 78% of the signal shared between the three cores. The proportion of shared signal between accumulation records from the Logan plateau (Prospector-Russell Col and Northwest Col) is lower (52%). In this work we will compare the Eclipse and Logan accumulation records to each other to understand the spatial variability in net accumulation over time at different altitudes. The possible influence of dating errors on these results will be explored using leads and lags of 1-2 years. We also compare our accumulation records to indices of atmospheric circulation (e.g., strength of the Aleutian Low, the Pacific Decadal Oscillation, the El-Nino Southern Oscillation, Arctic Oscillation) to quantify relationships between snow accumulation and large-scale atmospheric circulation features on time-scales of variability ranging from years to centuries.

  2. 7000 year European climate record from the Ortles ice core

    NASA Astrophysics Data System (ADS)

    Gabrielli, Paolo; Barbante, Carlo; Bertagna, Giuliano; Bertó, Michele; Carturan, Luca; Dinale, Roberto; Dreossi, Giuliano; Festi, Daniela; Mair, Volkmar; Oeggl, Klaus; Seppi, Roberto; Stenni, Barbara; Tonidandel, David

    2017-04-01

    In 2011 four ice cores were extracted from the summit of Alto dell'Ortles (3859 m), the highest glacier of South Tyrol in the Italian Alps. This drilling site is located only 37 km southwest from where the 5.2 kyrs old Tyrolean Iceman was discovered emerging from the ablating ice field of Tisenjoch (3210 m, near the Italian-Austrian border) in 1991. The excellent preservation of this mummy suggested that the Tyrolean Iceman was continuously embedded in coeval prehistoric ice and that additional ancient ice was likely preserved elsewhere in South Tyrol. Dating of the ice cores from Alto dell'Ortles based on 210Pb, 3H, beta activity and 14C determinations, combined with an empirical model (COPRA), provides evidence of a chronologically ordered ice stratigraphy from the modern glacier surface down to the bottom ice layers with an age of ˜7 kyrs, which confirms that ancient ice is preserved in this area of the Alps. Our results indicate that the drilling site was continuously glaciated on frozen bedrock since ˜7 kyrs BP. Absence of older ice on the highest glacier of South Tyrol is consistent with removal of basal ice from bedrock during the Northern Hemisphere Climatic Optimum (NHCO; 6-9 kyrs BP), the warmest interval in the European Alps during the Holocene. At the end of the NHCO temperatures started to decrease allowing the accumulation of cold ice on frozen bedrock. A short increase in precipitation at ˜7 kyrs BP could also have contributed to higher accumulation and ice thickening on Alto dell'Ortles. Although high precipitation did not persist during the mid-Holocene, progressively more favourable glacial conditions characterized the Eastern Alps at the end of the NHCO and glaciers extended in general to lower elevations, including the Tisenjoch (3210 m) where the Tyrolean Iceman was buried in snow and ice since 5.2 kyrs BP.

  3. Solar cycles or random processes? Evaluating solar variability in Holocene climate records.

    PubMed

    Turner, T Edward; Swindles, Graeme T; Charman, Dan J; Langdon, Peter G; Morris, Paul J; Booth, Robert K; Parry, Lauren E; Nichols, Jonathan E

    2016-04-05

    Many studies have reported evidence for solar-forcing of Holocene climate change across a range of archives. These studies have compared proxy-climate data with records of solar variability (e.g. (14)C or (10)Be), or have used time series analysis to test for the presence of solar-type cycles. This has led to some climate sceptics misrepresenting this literature to argue strongly that solar variability drove the rapid global temperature increase of the twentieth century. As proxy records underpin our understanding of the long-term processes governing climate, they need to be evaluated thoroughly. The peatland archive has become a prominent line of evidence for solar forcing of climate. Here we examine high-resolution peatland proxy climate data to determine whether solar signals are present. We find a wide range of significant periodicities similar to those in records of solar variability: periods between 40-100 years, and 120-140 years are particularly common. However, periodicities similar to those in the data are commonly found in random-walk simulations. Our results demonstrate that solar-type signals can be the product of random variations alone, and that a more critical approach is required for their robust interpretation.

  4. Solar cycles or random processes? Evaluating solar variability in Holocene climate records

    PubMed Central

    Turner, T. Edward; Swindles, Graeme T.; Charman, Dan J.; Langdon, Peter G.; Morris, Paul J.; Booth, Robert K.; Parry, Lauren E.; Nichols, Jonathan E.

    2016-01-01

    Many studies have reported evidence for solar-forcing of Holocene climate change across a range of archives. These studies have compared proxy-climate data with records of solar variability (e.g. 14C or 10Be), or have used time series analysis to test for the presence of solar-type cycles. This has led to some climate sceptics misrepresenting this literature to argue strongly that solar variability drove the rapid global temperature increase of the twentieth century. As proxy records underpin our understanding of the long-term processes governing climate, they need to be evaluated thoroughly. The peatland archive has become a prominent line of evidence for solar forcing of climate. Here we examine high-resolution peatland proxy climate data to determine whether solar signals are present. We find a wide range of significant periodicities similar to those in records of solar variability: periods between 40–100 years, and 120–140 years are particularly common. However, periodicities similar to those in the data are commonly found in random-walk simulations. Our results demonstrate that solar-type signals can be the product of random variations alone, and that a more critical approach is required for their robust interpretation. PMID:27045989

  5. Identification of the driving forces of climate change using the longest instrumental temperature record

    NASA Astrophysics Data System (ADS)

    Wang, Geli; Yang, Peicai; Zhou, Xiuji

    2017-04-01

    The identification of causal effects is a fundamental problem in climate change research. Here, a new perspective on climate change causality is presented using the central England temperature (CET) dataset, the longest instrumental temperature record, and a combination of slow feature analysis and wavelet analysis. The driving forces of climate change were investigated and the results showed two independent degrees of freedom —a 3.36-year cycle and a 22.6-year cycle, which seem to be connected to the El Niño-Southern Oscillation cycle and the Hale sunspot cycle, respectively. Moreover, these driving forces were modulated in amplitude by signals with millennial timescales.

  6. Identification of the driving forces of climate change using the longest instrumental temperature record

    PubMed Central

    Wang, Geli; Yang, Peicai; Zhou, Xiuji

    2017-01-01

    The identification of causal effects is a fundamental problem in climate change research. Here, a new perspective on climate change causality is presented using the central England temperature (CET) dataset, the longest instrumental temperature record, and a combination of slow feature analysis and wavelet analysis. The driving forces of climate change were investigated and the results showed two independent degrees of freedom —a 3.36-year cycle and a 22.6-year cycle, which seem to be connected to the El Niño–Southern Oscillation cycle and the Hale sunspot cycle, respectively. Moreover, these driving forces were modulated in amplitude by signals with millennial timescales. PMID:28387247

  7. Influence of mean climate change on climate variability from a 155-year tropical Pacific coral record.

    PubMed

    Urban, F E; Cole, J E; Overpeck, J T

    2000-10-26

    Today, the El Niño/Southern Oscillation (ENSO) system is the primary driver of interannual variability in global climate, but its long-term behaviour is poorly understood. Instrumental observations reveal a shift in 1976 towards warmer and wetter conditions in the tropical Pacific, with widespread climatic and ecological consequences. This shift, unique over the past century, has prompted debate over the influence of increasing atmospheric concentrations of greenhouse gases on ENSO variability. Here we present a 155-year ENSO reconstruction from a central tropical Pacific coral that provides new evidence for long-term changes in the regional mean climate and its variability. A gradual transition in the early twentieth century and the abrupt change in 1976, both towards warmer and wetter conditions, co-occur with changes in variability. In the mid-late nineteenth century, cooler and drier background conditions coincided with prominent decadal variability; in the early twentieth century, shorter-period (approximately 2.9 years) variability intensified. After 1920, variability weakens and becomes focused at interannual timescales; with the shift in 1976, variability with a period of about 4 years becomes prominent. Our results suggest that variability in the tropical Pacific is linked to the region's mean climate, and that changes in both have occurred during periods of natural as well as anthropogenic climate forcing.

  8. New record shows pronounced changes in Arctic Ocean circulation and climate

    NASA Astrophysics Data System (ADS)

    Darby, D.; Bischof, J.; Cutter, G.; de Vernal, A.; Hillaire-Marcel, C.; Dwyer, G.; McManus, J.; Osterman, L.; Polyak, L.; Poore, R.

    Does the Arctic Ocean surface circulation north of Alaska oscillate to and fro like a slow washing machine on millennial timescales? New evidence from the sediment record over the last 10,000 years suggests that it does and that in the recent past, the western Arctic Ocean was much warmer than it is today.Similar Holocene climatic fluctuations are seen in many records worldwide, yet their origin remains enigmatic. Modeling and observational studies suggest that the Arctic may play an important role in these climate fluctuations through changes in surface albedo, modifications of oceanic thermohaline circulation, and changes in biogeochemical cycling of nutrients and radiatively important gases [PARCS, 1999].

  9. Assessing the Pleistocene hemispheric climate links through correlating loess, marine and ice-core records

    NASA Astrophysics Data System (ADS)

    Guo, Z.

    2015-12-01

    Near continuous loess-soil records in China cover the past 22 million years. Here, we compare various independent climate proxies from the terrestrial, marine and ice-core domains to re-evaluate the regional and global significance of the China loess with special emphases to the Quaternary portion. The results confirm that the intensity of loess deposition in China is closely coupled with the northern high latitude climate from the over-orbital to millennial scales, and that loess accumulation rates (LAR) and loess particle-size reflect many features of the northern high latitude ice conditions. Consequently, correlating the loess and marine records could offer the possibility for addressing the hemispheric climate links. Our loess-marine correlations show that both records are broadly coupled during the Pleistocene. However, numerous decoupled features exist between the two records. Marine oxygen isotope record shows a general trend of increased ice-volume during the Pleistocene. This trend has no clear reflection in the loess LAR and grain-size data. A prominent change at ~ 430 ka, referred to as the Mid-Brunhes Event (MBE), is clearly documented in both marine and EPICA ice records while its reflections in loess are rather ambiguous. Both marine and EPICA data show a cooler-than-average interglacial for the marine-oxygen isotope stage 13 (MIS-13) while a series of terrestrial records show a warm-extreme interglacial for the northern hemisphere. During a number of glacial intervals, such as MIS-16, MIS 14, MIS-12 and MIS-3, interglacial-level of loess grain-size are observed while they have no obvious reflections in the marine and EPICA ice records. Based on a multi-proxy approach, we argue that these decoupled features between the loess and marine records are attributable to the asymmetrical behaviors of the Pleistocene climates between the southern and northern hemispheres.

  10. A molecular organic carbon isotope record of miocene climate changes

    SciTech Connect

    Schoell, M. ); Schouten, S.; Sinninghe Damste', J.S.; Leeuw, J.W. de ); Summons, R.E. )

    1994-02-25

    The difference in carbon-13 ([sup 13]C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in [sup 18]O ([delta][sup 18]O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes ([delta][sup 13]C = 25.4 [+-] 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C[sub 35] hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing [sup 13]C concentrations in Middle and Late Miocene samples ([delta][sup 13]C = 29.5 to [minus]31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone.

  11. Climatic controls on hurricane patterns: a 1200-y near-annual record from Lighthouse Reef, Belize

    PubMed Central

    Denommee, K. C.; Bentley, S. J.; Droxler, A. W.

    2014-01-01

    Tropical cyclones (TCs) are powerful agents of destruction, and understanding climatic controls on TC patterns is of great importance. Over timescales of seasons to several decades, relationships among TC track, frequency, intensity and basin-scale climate changes are well documented by instrumental records. Over centuries to millennia, climate-shift influence on TC regimes remains poorly constrained. To better understand these relationships, records from multiple locations of TC strikes spanning millennia with high temporal resolution are required, but such records are rare. Here we report on a highly detailed sedimentary proxy record of paleo-TC strikes from the Blue Hole of Lighthouse Reef, Belize. Our findings provide an important addition to other high-resolution records, which collectively demonstrate that shifts between active and inactive TC regimes have occurred contemporaneously with shifts hemispheric-scale oceanic and atmospheric circulation patterns such as MDR SSTs and NAO mode, rather than with changes in local climate phenomena as has previously been suggested. PMID:24464265

  12. An 8700 Year Record of Holocene Climate Variability from the Yucatan Peninsula

    NASA Astrophysics Data System (ADS)

    Wahl, D.; Byrne, R.; Anderson, L.

    2013-12-01

    Our understanding of Holocene climate change in the Maya lowlands of Central America has improved significantly during the last several decades thanks to the development of proxy climate records from lake cores and speleothems. One important finding is that longer-term climate changes (i.e., millennial scale) were driven primarily by precessional forcing; less clear, however, are the causes of abrupt shifts and higher frequency (centennial to decadal) change recognized in many Holocene climate reconstructions. The mechanisms driving climate change on these time scales have been difficult to identify in the region, in part because the Yucatan peninsula is influenced by climatic conditions linked to both the tropical Atlantic and Pacific oceans. Additional complications arise from the development of dense human populations following the initial introduction of agriculture ~5000 cal yr BP, which had significant impact on the environment as a whole. Here we present the results of analyses (stable isotope, pollen, magnetic susceptibility, and physical properties) of a 7.25 m sediment core from Lago Puerto Arturo, a closed basin lake in the northern Peten, Guatemala. An age-depth model, based on 6 AMS radiocarbon determinations and created using CLAM, indicates the record extends to 8700 cal yr BP. Proxy data suggest that, similar to other low latitude sites, millennial scale climate at Lago Puerto Arturo was driven by changes in insolation. Higher frequency variability is associated with El Niño/Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) dynamics, reflecting latitudinal shifts in the Intertropical Convergence Zone in both the tropical North Atlantic and North Pacific. Solar forcing may also play a role in short-term climate change. The pollen and isotope records show that the entire period of prehispanic settlement and agricultural activity, i.e. ~5000-1000 cal yr B.P., was characterized by relatively dry conditions compared to before or after.

  13. Climatic Change over the 'Third Pole' from Long Tree-Ring Records

    NASA Astrophysics Data System (ADS)

    Cook, E.

    2011-12-01

    Climatic change over the Greater Himalayas and Tibetan Plateau, the 'Third Pole' of the world, is of great concern now as the Earth continues to warm at an alarming rate. While future climatic change over this region and its resulting impacts on humanity and the environment are difficult to predict with much certainty, knowing how climate has varied in the past can provide both an improved understanding of the range of variability and change that could occur in the future and the necessary context for assessing recent observed climatic change there. For this purpose, one of the best natural archives of past climate information available for study of the Third Pole environment is the changing pattern of annual ring widths found in long tree-ring chronologies. The forests of the Third Pole support many long-lived tree species, with some having life spans in excess of 1,000 years. This natural resource is steadily dwindling now due to continuing deforestation caused by human activity, but there is still enough remaining forest cover to produce a detailed network of long tree-ring chronologies for study of climate variability and change covering the past several centuries. The tree-ring records provide a mix of climate information, including that related to both temperature and precipitation. Examples of long drought-sensitive tree-ring records from the more arid parts of the Karakoram and Tibetan Plateau will be presented, along with records that primarily reflect changing temperatures in moister environments such as in Bhutan. Together they provide a glimpse of how climate of the Third Pole has changed over the past several centuries, the range of natural variability that could occur in the future independent of changes caused by greenhouse warming, and how changes during the latter part of the 20th century period of rapid global warming compare to the past.

  14. Comparing records to understand past rapid climate change: An INTIMATE database update

    NASA Astrophysics Data System (ADS)

    Kearney, Rebecca; Bronk Ramsey, Christopher; Staff, Richard A.; Albert, Paul G.

    2017-04-01

    Integrating multi-proxy records from ice, terrestrial and marine records enhances the understanding of the temporal and spatial variation of past rapid climatic changes globally. By handling these records on their own individual timescales and linking them through known chronological relationships (e.g. tephra, 10Be and 14C), regional comparisons can be made for these past climatic events. Furthermore, the use of time-transfer functions enables the chronological uncertainties between different archives to be quantified. The chronological database devised by the working group 1 (WG1) of INTIMATE, exclusively uses this methodology to provide a means to visualise and compare palaeoclimate records. Development of this database is ongoing, with numerous additional records being added to the database with a particular focus on European archives spanning the Late Glacial period. Here we present a new phase of data collection. Through selected cases study sites across Europe, we aim to illustrate the database as a novel tool in understanding spatial and temporal variations in rapid climatic change. Preliminary results allow questions such as time transgression and regional expressions of rapid climate change to be investigated. The development of this database will continue through additional input of raw climate proxy data, linking to other relevant databases (e.g. Fossil Pollen Database) and providing output data that can be analysed in the statistical programming language of R. A major goal of this work to is not only provide a detailed database, but allow researchers to integrate their own climate proxy data with that on the database.

  15. A New Climate Data Record of Solar Spectral Irradiance from 1610 to Present

    NASA Astrophysics Data System (ADS)

    Coddington, O.; Lean, J.; Pilewskie, P.; Snow, M. A.; Lindholm, D. M.

    2015-12-01

    We present a climate data record of Solar Spectral Irradiance (SSI), with associated time and wavelength dependent uncertainties, from 1610 to the present. The data record was developed jointly by the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics (LASP) and the Naval Research Laboratory (NRL) as part of the National Oceanographic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) Climate Data Record (CDR) Program, where the data record, source code, and supporting documentation are archived. SSI is constructed from models that determine the changes from quiet Sun conditions arising from bright faculae and dark sunspots on the solar disk using linear regression of proxies of solar magnetic activity with observations from the SOlar Radiation and Climate Experiment (SORCE) Spectral Irradiance Monitor (SIM); the measurements are assumed to be reliable on solar rotational time scales. We extend the SSI record to longer time scales by reproducing the integral of the SSI with independent measurements of Total Solar Irradiance (TSI) measurements made by the SORCE Total Irradiance Monitor (TIM); TSI can be separately modeled to within TIM's measurement accuracy from solar rotational to solar cycle time scales. We discuss the model formulation, uncertainty estimates, and operational implementation and present comparisons of the modeled SSI with the measurement record and with other solar irradiance models. We also discuss future work to improve the Solar Irradiance Climate Data Record with new measurements from the Total and Spectral Solar Irradiance Sensor (TSIS), different proxy representations of sunspot darkening and facular brightening, including the improved composite record of Mg II index being developed as part of the European-led SOlar Irradiance Data exploitation (SOLID) project, and to expand the uncertainty estimates to include model assumptions.

  16. Records from Lake Qinghai: Holocene climate history of Northeastern Tibetan Plateau linking to global change

    NASA Astrophysics Data System (ADS)

    An, Z.; Colman, S.; Zhou, W.; Brown, E.; Li, X.; Jull, T.; Wang, S.; Liu, W.; Sun, Y.; Lu, X.; Song, Y.; Chang, H.; Cai, Y.; Xu, H.; Wang, X.; Liu, X.; Wu, F.; Han, Y.; Cheng, P.; Ai, L.; Wang, Z.; Qiang, X.; Shen, J.; Zhu, Y.; Wu, Z.; Liu, X.

    2008-12-01

    Lake Qinghai (99°36'-100°16'E, 36°32'-37°15'N ) of the north eastern margin of Tibet Plateau is the largest inland lake of China. It sits on the transitional zone of Asian monsoon- arid areas, receives influences of Asian monsoons and Westerlies, thus sensitive to global climate changes. Although previous studies had investigated Holocene climate change of Lake Qinghai area, it is rare to see precise Holocene climatic sequences of Lake Qinghai, nor in-depth discussions on controlling factors of Lake Qinghai climate changes. In Year 2005, with support from ICDP, Chinese Academy of Sciences (CAS), Chinese Ministry of Science and Technology (MOST) and National Science Foundation of China (NSFC), Drilling, Observation and Sampling of the Earths Continental Crust Corporation (DOSECC) and Institute of Earth Environment, Chinese Academy of Sciences (IEECAS) took a series of shallows cores from the southern basin of Lake Qinghai. West sub-basin sediments display Holocene lacustrine feature for the upper 5m, while the 5-18m are interbeded sediments of shallow lake, eolian-lacustrine and eolian loess. Chinese and US scientists with support from NSFC, MOST, CAS and NSF analysed 1F core from west sub-basin depocenter of the south basin with multiple physical, chemical, biological approaches. By comparing with modern process observation records, we obtained proxies that respectfully reflect precipitation, temperature and lake salinity changes, etc., reconstructed high resolution time sequences of magnetic susceptibility, colour scale, grain size, Corg, C/N, δ13Corg, carbonate, δ13C and δ18O of carbonate and ostracodes, elements, char-soot,Uk'37 and %C37:4 as well as pollen of the last 13Ka. They indicate the climatic change history of Lake Qinghai since past 13Ka, and agreeable evidences are found from adjacent tree ring and stalagmite records. Comparison of Lake Qinghai Holocene climate change sequence with those from high altitude ice core, stalagmites and ocean

  17. Diatom Records of Holocene Environmental and Climatic Change in Southeastern British Columbia

    NASA Astrophysics Data System (ADS)

    Westover, K. S.; Gavin, D. G.; Fritz, S. C.; Hu, F.; Roschen, L. A.

    2004-12-01

    The sediments of three lakes, spanning a latitudinal gradient and situated within the Interior Cedar-Hemlock biogeoclimatic zone of southeast British Columbia, have been analyzed for independent records of Holocene climate and vegetation history in order to evaluate the role of climate as a control on range expansion of western hemlock and western redcedar. Holocene climate reconstructions are based on multiple proxies, including the diatom and biogenic silica stratigraphies presented here. To our knowledge, these sites provide the first continuous Holocene paleoecological and paleoclimatic records from the region between the Interior Plateau and the Rocky Mountains. Stratigraphic variability in the diatom sedimentary records reflects lake response to changes in water balance, catchment development, and atmospheric inputs of silica (i.e. volcanic ash). At Eleanor Lake, the diatom record shows significant assemblage shifts at ˜7500, 6300, and 3700 cal yr BP. Increased abundance of planktonic and tychoplanktonic diatoms and an increase in the abundance of chrysophyte cysts relative to diatoms at 6300 cal yr BP is consistent with an increase in effective moisture at this time. At Mirror Lake, in the south, an assemblage dominated by small benthic species is replaced by a predominantly planktonic assemblage at 6900 cal yr BP, suggesting an earlier increase in lake level. After 6000 cal yr BP, planktonic diatoms further increase in dominance. These dates are consistent with reconstructions of Holocene climate in south-central British Columbia, which suggest a shift to moister conditions ca. 7000 to 6000 cal yr BP. The pollen record indicates the expansion of western hemlock and western redcedar near Mirror Lake at 3550 cal yr BP and 3250 cal yr BP respectively. At Eleanor Lake, hemlock expansion is dated at 4350 cal yr BP. The data indicate a difference of 1950 to > 3000 years between the lacustrine record of increased effective moisture and the vegetation response and

  18. Sampling Impacts on the NVAP-M Global Water Vapor Climate Data Record

    NASA Astrophysics Data System (ADS)

    Vonder Haar, T. H.; Forsythe, J. M.; Cronk, H. Q.

    2015-12-01

    Atmospheric water vapor is a fundamental ingredient both for regulating climate as a greenhouse gas and as a necessary precursor for high impact weather events such as heavy precipitation. Water vapor concentration varies geographically because of its close linkage with surface temperature and as a component of synoptic and mesoscale weather systems. Satellite observations provide the only means to quantify the global occurrence and variability of water vapor. In common with other long-term climate data records such as clouds and precipitation, intercalibrating and blending diverse measurements of water vapor to create a consistent record through time is a challenge. The NASA Making Earth Science Data Records for Research Environments (MEaSUREs) program supported the development of the NASA Water Vapor Project (NVAP-M) dataset. The dataset was released to the science community in 2013 via the NASA Langley Atmospheric Science Data Center. The dataset is a global (land and ocean) water vapor dataset created by merging multiple satellite infrared and microwave sources of atmospheric water vapor along with surface data to form global gridded fields of total and layered precipitable water vapor. NVAP-M spans 22 years (1988-2009) of data. The challenges in creating this multisensor, multidecadal satellite-driven climate data record are illustrative of challenges for all satellite climate data records. While advances in sensor intercalibration and retrieval algorithms have improved the quality of the global water vapor climate data record, uncertainties arise due to sampling biases of the input sensors. These biases are particularly evident on a regional scale, in cloudy regions or over desert surfaces. The changing mixture of sensors with varying sensitivity to clear/cloudy, land/ocean and even day/night conditions can lead to different results on trends and variability of water vapor. We explore this variability via the NVAP-M data set. Connections and collaborations

  19. A long-term Northern Hemisphere snow cover extent data record for climate studies and monitoring

    NASA Astrophysics Data System (ADS)

    Estilow, T. W.; Young, A. H.; Robinson, D. A.

    2015-06-01

    This paper describes the long-term, satellite-based visible snow cover extent National Oceanic and Atmospheric Administration (NOAA) climate data record (CDR) currently available for climate studies, monitoring, and model validation. This environmental data product is developed from weekly Northern Hemisphere snow cover extent data that have been digitized from snow cover maps onto a Cartesian grid draped over a polar stereographic projection. The data have a spatial resolution of 190.6 km at 60° latitude, are updated monthly, and span the period from 4 October 1966 to the present. The data comprise the longest satellite-based CDR of any environmental variable. Access to the data is provided in Network Common Data Form (netCDF) and archived by NOAA's National Climatic Data Center (NCDC) under the satellite Climate Data Record Program (doi:10.7289/V5N014G9). The basic characteristics, history, and evolution of the data set are presented herein. In general, the CDR provides similar spatial and temporal variability to its widely used predecessor product. Key refinements included in the CDR improve the product's grid accuracy and documentation and bring metadata into compliance with current standards for climate data records.

  20. Climate history at Aurora Basin North, East Antarctica: A 2,000 year isotopic record

    NASA Astrophysics Data System (ADS)

    Moy, Andrew; van Ommen, Tas; McConnel, Joe; Curran, Mark; Phipps, Steven; Masson-Delmotte, Valérie; Orsi, Anaïs; Touzeau, Alexandra; Roberts, Jason; Dahl-Jensen, Dorthe; Popp, Trevor; Svensson, Anders; Landais, Amaelle; Vance, Tessa; Liu, Yaping; Arienzo, Monica

    2017-04-01

    In Antarctica, a reasonable coverage of ice core records exist for the last couple of hundred years, however there is poor spatial coverage of high-resolution climate data over the last 2000 years, particularly from East Antarctica (EA). The aim of the Aurora Basin North (ABN) ice core drilling project is to provide a 2000 year climate record from a data sparse area of EA to add to the IPICS 2k array and the PAGES Antarctica2k projects. ABN is a 303m ice core from EA, 550km inland and about half way between the coastal Law Dome and inland Dome C sites. Contiguous measurements of water stable isotope ratios (d18O and dD) have been performed along the entire length of the ABN ice core and provides a climate record at seasonal to decadal resolution for this region of EA spanning the past 2000 years. The isotopic variability at ABN shows clear annual cycles in the upper 50 m and longer-term variability on decadal to centennial timescales. The ABN record shows no long-term isotopic trend over the 2,000 year record length, similar to the four isotopic ice core records used in EA for the PAGES Antarctic 2k temperature reconstruction (PAGES2k, 2013). Mean ABN isotopic values (d18O -40.70 per mille, and dD -321.1 per mille) fall along the modern Antarctic spatial isotope/elevation and isotope/distance from the ocean relationships. The second order isotope parameter, deuterium excess (d) displays a relatively stable record (mean value of 4.4 per mille), with occasional sharp transitions to values as high as 8-10 per mille and as low as 0-1 per mille =. The large deuterium excess variations may reflect changes in moisture origin and evaporation conditions (SST, relative humidity). The isotopic variability at ABN therefore potentially reflects a mix of changes in transport and local climate (acting on precipitation intermittency and distillation strength), as well as local elevation changes. A comparison of the preliminary dated ABN isotope record with the Law Dome isotopic

  1. Proxy records of climate change in subtropical and tropical karst environments

    NASA Astrophysics Data System (ADS)

    Polk, Jason Samuel

    Understanding the paleoclimate of a region is important, especially when trying to determine the extent of natural climate variability within the context of anthropogenic impacts. Recent anomalous periods of climate change in the Late Holocene, including the Little Ice Age and Medieval Warm Period, could possibly repeat in the future, having significant worldwide consequences. This holds especially true for tropical and subtropical karst environments, where limited paleoclimate proxies provide minimal data regarding past climate change. An investigation into past climate change in Belize using fulvic acids from cave sediments shows periods of drought during the collapse of the Maya society around 1400 years ago. Comparison of changes in the carbon isotope data from the fulvic acids agree with speleothem records, but more closely reflect changes in the vegetation above the cave, showing Maya population decline through waning agriculture. Further investigation of using fulvic and other organics acids are examined from cave sediments in Florida. The data show fulvic acid carbon isotopes are the most robust recorders of climate change, agreeing with several nearby speleothem delta18O and delta13C records from west-central Florida. A more detailed record of climate change in Florida through a calibration study of precipitation and cave dripwater oxygen and hydrogen isotopes revealed that the amount effect dominates rainfall in west-central Florida. Homogenization of epikarst dripwater gives average delta18O values representative of the annual amount-weighted average of precipitation delta18O for the area, suggesting speleothem isotope records reflect changes in rainfall amount. Examination of two speleothems from west-central Florida show complex teleconnection and solar forcing mechanisms responsible for past climate changes. A high-resolution stable isotope, trace element, and time series analysis study for the last 1500 years shows variability during the LIA and MWP

  2. Climate Change Detection in the UTLS with the GPS Radio Occultation Record

    NASA Astrophysics Data System (ADS)

    Steiner, A. K.; Kirchengast, G.; Lackner, B. C.; Hegerl, G. C.; Pirscher, B.; Foelsche, U.

    2009-12-01

    Radio Occultation (RO) based on signals from Global Positioning System (GPS) satellites provides a new climate record of high quality and vertical resolution in the upper troposphere and lower stratosphere (UTLS). RO data are considered a climate benchmark data type since they are based on timing with precise atomic clocks and tied to the international definition of the second. Long-term stability and the consistency of RO data stemming from different satellites (without need for inter-calibration) make RO well suited for climate change detection. RO data are available on a continuous basis from Sep 2001 to Sep 2008 from the CHAMP satellite and intermittent periods of observations from the GPS/Met proof-of-concept mission exist in the years 1995-1997, with sufficient data only for Oct 1995 and Feb 1997. We present a climate change detection study based on monthly mean zonal mean RO climatologies in the UTLS region within 9-25 km (300-30 hPa) where we use different detection methods. An optimal fingerprinting technique is applied to the whole record of RO accessible parameters refractivity, geopotential height, and temperature to detect a forced climate signal. Three representative global climate models of the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) are employed to estimate natural climate variability using pre-industrial control runs. The response pattern to the external forcings is presented by an ensemble mean of the models' A2 and B1 scenario runs. Optimal fingerprinting shows that a climate change signal can be detected in the RO refractivity and in the RO temperature record (90 % significance level). Furthermore, standard and multiple linear regression is applied to temperature time series for February (1997 and 2002-2008) and for October (1995 and 2001-2007), taking RO errors into account. In the tropics, we also investigate the influence of stratospheric quasi-biennial oscillation (QBO) and tropospheric El Nino

  3. Late Quaternary climate variability in the Sahel: inferences from marine dust records offshore Senegal

    NASA Astrophysics Data System (ADS)

    Stuut, J. W.; Meyer, I.; Fischer, H.; Mollenhauer, G.; Mulitza, S.; Pittauerova, D.; Zabel, M.; Schulz, M.

    2008-12-01

    Societies and ecosystems in northern Africa are strongly affected by the availability of water. As a consequence, long-term absence of rainfall has very dear effects on the ecosystems, as was dramatically shown in the 70'ies and 80'ies of the 20th century. Recent high-resolution reconstructions of Sahel palaeoclimate allow for new insights into these drastic climate variations and to disentangle the effects of the different components of the climate system on African climate change. In this study we extend the instrumental record of climate variability using marine sediment cores that were retrieved off the coast of Senegal, northwest Africa. The sediment records contain continuous high-resolution records of dust sedimentation ranging from about 4,000 to about 57,000 years. A 210Pb age model for the youngest sediments allows for a matching of the proxy rainfall record with instrumental precipitation data. Specifically, variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997) are used to reconstruct rainfall variability on land throughout the late Quaternary.

  4. A 0.6 million year record of millennial-scale climate variability in the tropics

    NASA Astrophysics Data System (ADS)

    Gibson, Kelly Ann; Peterson, Larry C.

    2014-02-01

    A ~600 kyr long scanning X-ray fluorescence record of redox variability from the Cariaco Basin, Venezuela, provides insight into rapid climate change in the tropics over the past five glacial-interglacial cycles. Variations in the sediment accumulation of the redox-sensitive element molybdenum (Mo) can be linked to changes in Intertropical Convergence Zone migration and reveal that millennial-scale variability is a persistent feature of tropical climate over the past 600 kyr, including during periods of interglacial warmth. This new record supports the idea that high-frequency tropical climate variability is not controlled solely by ice volume changes, with implications for the role of high-latitude forcing of Intertropical Convergence Zone position and tropical hydrology on millennial timescales.

  5. Detailed glaciochemical investigations in southern Victoria Land - a proxy climatic record

    SciTech Connect

    Mayewski, P.A.

    1987-09-01

    Local accumulation-basins in the Transantarctic Mountains possess sites suitable for recovering ice-core records that are valuable for studying climate change. These sites are also unique, because they are close to the sites of other ice-core studies and to areas with established terrestrial records. The objective is to study a snowpit in detail and collect ice cores in southern Victoria Land; this work will be similar to the investigations that the authors has conducted in south Greenland and in the Dominion Range near the Beardmore Glacier. The proposed sites are in Convoy, Asgard, and Royal Society ranges. The authors will select one site at which he will recover two ice cores, each approximately 200 to 300 meters in depth. Samples will be analyzed for major anions (chloride, sulfate, nitrate, fluoride) and cations (sodium, potassium, magnesium, ammonium, silicate), total acidity, conductivity, density, and core stratigraphy with dating provided by cross-calibration of all of the preceding plus total beta-activity, lead-210, oxygen isotopes, and microparticles. This investigation will yield a detailed record of several thousand years of glacial history, climate change, and volcanic activity for southern Victoria Land. This record will be compared to existing terrestrial records to add necessary detail and to other global ice-core records to assess global climatic change. It will also help to document volcanic activity for Mount Erebus as well as other volcanos in the Southern Hemisphere and possibly some in the Northern Hemisphere. With this record, the author will be able to evaluate the influence of volcanic and solar activity on climate as well as add greatly to the understanding of the chemistry of the global atmosphere.

  6. 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

  7. Ice cores record significant 1940s Antarctic warmth related to tropical climate variability.

    PubMed

    Schneider, David P; Steig, Eric J

    2008-08-26

    Although the 20th Century warming of global climate is well known, climate change in the high-latitude Southern Hemisphere (SH), especially in the first half of the century, remains poorly documented. We present a composite of water stable isotope data from high-resolution ice cores from the West Antarctic Ice Sheet. This record, representative of West Antarctic surface temperature, shows extreme positive anomalies in the 1936-45 decade that are significant in the context of the background 20th Century warming trend. We interpret these anomalies--previously undocumented in the high-latitude SH--as indicative of strong teleconnections in part driven by the major 1939-42 El Niño. These anomalies are coherent with tropical sea-surface temperature, mean SH air temperature, and North Pacific sea-level pressure, underscoring the sensitivity of West Antarctica's climate, and potentially its ice sheet, to large-scale changes in the global climate.

  8. Ice cores record significant 1940s Antarctic warmth related to tropical climate variability

    PubMed Central

    Schneider, David P.; Steig, Eric J.

    2008-01-01

    Although the 20th Century warming of global climate is well known, climate change in the high-latitude Southern Hemisphere (SH), especially in the first half of the century, remains poorly documented. We present a composite of water stable isotope data from high-resolution ice cores from the West Antarctic Ice Sheet. This record, representative of West Antarctic surface temperature, shows extreme positive anomalies in the 1936–45 decade that are significant in the context of the background 20th Century warming trend. We interpret these anomalies—previously undocumented in the high-latitude SH—as indicative of strong teleconnections in part driven by the major 1939–42 El Niño. These anomalies are coherent with tropical sea-surface temperature, mean SH air temperature, and North Pacific sea-level pressure, underscoring the sensitivity of West Antarctica's climate, and potentially its ice sheet, to large-scale changes in the global climate. PMID:18697932

  9. Exceptional record of mid-Pleistocene vertebrates helps differentiate climatic from anthropogenic ecosystem perturbations

    PubMed Central

    Barnosky, Anthony D.; Bell, Christopher J.; Emslie, Steven D.; Goodwin, H. Thomas; Mead, Jim I.; Repenning, Charles A.; Scott, Eric; Shabel, Alan B.

    2004-01-01

    Mid-Pleistocene vertebrates in North America are scarce but important for recognizing the ecological effects of climatic change in the absence of humans. We report on a uniquely rich mid-Pleistocene vertebrate sequence from Porcupine Cave, Colorado, which records at least 127 species and the earliest appearances of 30 mammals and birds. By analyzing >20,000 mammal fossils in relation to modern species and independent climatic proxies, we determined how mammal communities reacted to presumed glacial–interglacial transitions between 1,000,000 and 600,000 years ago. We conclude that climatic warming primarily affected mammals of lower trophic and size categories, in contrast to documented human impacts on higher trophic and size categories historically. Despite changes in species composition and minor changes in small-mammal species richness evident at times of climatic change, overall structural stability of mammal communities persisted >600,000 years before human impacts. PMID:15197254

  10. Late Holocene climate and environmental changes in Kamchatka inferred from the subfossil chironomid record

    NASA Astrophysics Data System (ADS)

    Nazarova, Larisa; de Hoog, Verena; Hoff, Ulrike; Dirksen, Oleg; Diekmann, Bernhard

    2013-05-01

    This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomid remains from a 332 cm long composite sediment core recovered from Dvuyurtochnoe Lake (Two-Yurts Lake, TYL) in central Kamchatka. The oldest recovered sediments date to about 4500 cal years BP. Chironomid head capsules from TYL reflect a rich and diverse fauna. An unknown morphotype of Tanytarsini, Tanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomid assemblage zones reflecting four different climatic periods in the Late Holocene. Between 4500 and 4000 cal years BP, the chironomid composition indicates a high lake level, well-oxygenated lake water conditions and close to modern temperatures (˜13 °C). From 4000 to 1000 cal years BP, two consecutive warm intervals were recorded, with the highest reconstructed temperature reaching 16.8 °C between 3700 and 2800 cal years BP. Cooling trend, started around 1100 cal years BP led to low temperatures during the last stage of the Holocene. Comparison with other regional studies has shown that termination of cooling at the beginning of late Holocene is relatively synchronous in central Kamchatka, South Kurile, Bering and Japanese Islands and take place around 3700 cal years BP. From ca 3700 cal years BP to the last millennium, a newly strengthened climate continentality accompanied by general warming trend with minor cool excursions led to apparent spatial heterogeneity of climatic patterns in the region. Some timing differences in climatic changes reconstructed from chironomid record of TYL sediments and late Holocene events reconstructed from other sites and other proxies might be linked to differences in local forcing mechanisms or caused by the different degree of dating precision, the different temporal resolution, and the different sensitive responses of climate proxies to the climate variations. Further high-resolution stratigraphic studies in this region are needed to understand

  11. Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records.

    PubMed

    Martínez-Botí, M A; Foster, G L; Chalk, T B; Rohling, E J; Sexton, P F; Lunt, D J; Pancost, R D; Badger, M P S; Schmidt, D N

    2015-02-05

    Theory and climate modelling suggest that the sensitivity of Earth's climate to changes in radiative forcing could depend on the background climate. However, palaeoclimate data have thus far been insufficient to provide a conclusive test of this prediction. Here we present atmospheric carbon dioxide (CO2) reconstructions based on multi-site boron-isotope records from the late Pliocene epoch (3.3 to 2.3 million years ago). We find that Earth's climate sensitivity to CO2-based radiative forcing (Earth system sensitivity) was half as strong during the warm Pliocene as during the cold late Pleistocene epoch (0.8 to 0.01 million years ago). We attribute this difference to the radiative impacts of continental ice-volume changes (the ice-albedo feedback) during the late Pleistocene, because equilibrium climate sensitivity is identical for the two intervals when we account for such impacts using sea-level reconstructions. We conclude that, on a global scale, no unexpected climate feedbacks operated during the warm Pliocene, and that predictions of equilibrium climate sensitivity (excluding long-term ice-albedo feedbacks) for our Pliocene-like future (with CO2 levels up to maximum Pliocene levels of 450 parts per million) are well described by the currently accepted range of an increase of 1.5 K to 4.5 K per doubling of CO2.

  12. The new climate data record of total and spectral solar irradiance: Current progress and future steps

    NASA Astrophysics Data System (ADS)

    Coddington, Odele; Lean, Judith; Rottman, Gary; Pilewskie, Peter; Snow, Martin; Lindholm, Doug

    2016-04-01

    We present a climate data record of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI), with associated time and wavelength dependent uncertainties, from 1610 to the present. The data record was developed jointly by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder and the Naval Research Laboratory (NRL) as part of the National Oceanographic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) Climate Data Record (CDR) Program, where the data record, source code, and supporting documentation are archived. TSI and SSI are constructed from models that determine the changes from quiet Sun conditions arising from bright faculae and dark sunspots on the solar disk using linear regression of proxies of solar magnetic activity with observations from the SOlar Radiation and Climate Experiment (SORCE) Total Irradiance Monitor (TIM), Spectral Irradiance Monitor (SIM), and SOlar Stellar Irradiance Comparison Experiment (SOLSTICE). We show that TSI can be separately modeled to within TIM's measurement accuracy from solar rotational to solar cycle time scales and we assume that SSI measurements are reliable on solar rotational time scales. We discuss the model formulation, uncertainty estimates, and operational implementation and present comparisons of the modeled TSI and SSI with the measurement record and with other solar irradiance models. We also discuss ongoing work to assess the sensitivity of the modeled irradiances to model assumptions, namely, the scaling of solar variability from rotational-to-cycle time scales and the representation of the sunspot darkening index.

  13. Continuous methane record of abrupt climate change 10-68 ka: sighting Heinrich events in the ice core record

    NASA Astrophysics Data System (ADS)

    Rhodes, Rachael; Brook, Edward; Chiang, John; Blunier, Thomas; Cheng, Hai; Edwards, R. Lawrence; Maselli, Olivia; McConnell, Joseph; Romanini, Daniele; Severinghaus, Jeffrey; Sowers, Todd; Stowasser, Christopher

    2014-05-01

    The Last Glacial period was punctuated by millennial scale abrupt climate changes - Dansgaard-Oeschger (D-O) cycles and Heinrich events. Controls on the magnitude and frequency of these climate perturbations, and how they may be inter-related, remain unclear. Specific problems include the difficulty of dating Heinrich sediment layers and local bias of key paleoclimate archives. We present a highly detailed and precise record of ice core methane (CH4), a globally integrated signal, which resolves climatic features in unprecedented resolution. Abrupt CH4 increases are resolved in Heinrich Stadials (HS) 1, 2, 4 and 5 where, in contrast to all D-O cycles, there are no concurrent abrupt changes in Greenland temperature. Using modern-day tropical rainfall variability as an analog, we propose that strong cooling in the North Atlantic severely restricted the northerly range of the Intertropical Convergence Zone (ITCZ), leading to an enhanced wet season over Southern Hemisphere tropical land areas, and consequently driving production of excess CH4 in tropical wetlands. Our findings place four Heinrich events firmly within ice core chronologies and suggest maximum durations of 778 to 1606 yr. CH4 anomalies are only associated with Heinrich events of Hudson Strait provenance, indicating that the tropical impacts of Heinrich events were not uniform.

  14. Likelihood-based Quantification of Agreement between Climate Model Output and NASA Data Records

    NASA Astrophysics Data System (ADS)

    Braverman, A. J.; Huey, G.; Cressie, N.; Teixeira, J.

    2012-12-01

    In this talk we discuss the use of formal statistical likelihoods to quantify and assess the consistency of an observed data record with climate model predictions of it. The likelihood function is the conditional probability distribution of an unknown quantity as a function of the conditioning quantity. For instance, if P(A|B) (read ``the probability of A given B") is Gaussian with mean B, then the likelihood function for the mean is a function of different candidate values of B: L(b)=P(A|B=b). It shows how the probability of A changes when we assume different values of B are true. Here we let A be an observational statistic, and b be a climate model identifier. We use the time series generated by that climate model to estimate the sampling distribution of A under the hypothesis that the climate model correctly represents the behavior of the atmosphere. Then we ``score" the agreement between observations and models by the likelihood value, L(b). In this talk, we discuss our computational approach to estimating the sampling distributions, and report results achieved thus far in scoring the climate models used in the CMIP5 decadal experiments against water vapor data records from NASA's AIRS instrument.

  15. A 10,300 14C yr Record of Climate and Vegetation Change from Haiti

    NASA Astrophysics Data System (ADS)

    Higuera-Gundy, Antonia; Brenner, Mark; Hodell, David A.; Curtis, Jason H.; Leyden, Barbara W.; Binford, Michael W.

    1999-09-01

    Pleistocene and Holocene vegetation dynamics in the American tropics are inferred largely from pollen in continental lake sediments. Maritime influences may have moderated climate and vegetation changes on Caribbean islands. Stable isotope (δ18O) study of a 7.6-m core from Lake Miragoane, Haiti, provided a high-resolution record of changing evaporation/precipitation (E/P) since ∼10,300 14C yr B.P. The Miragoane pollen record documents climate influences and human impacts on vegetation in Hispaniola. The δ18O and pollen data near the base of the core indicate cool, dry conditions before ∼10,000 14C yr B.P. Lake Miragoane filled with water in the early Holocene as E/P declined and the freshwater aquifer rose. Despite increasing early Holocene moisture, shrubby, xeric vegetation persisted. Forest expanded ∼7000 14C yr B.P. in response to greater effective moisture and warming. The middle Holocene (∼7000-3200 14C yr B.P.) was characterized by high lake levels and greatest relative abundance of pollen from moist forest taxa. Climatic drying that began ∼3200 14C yr B.P. may have driven some mesophilic animal species to extinction. The pollen record of the last millennium reflects pre-Columbian (Taino) and European deforestation. Long-term, Holocene vegetation trends in southern Haiti are comparable to trends from continental, lowland circum-Caribbean sites, suggesting a common response to regional climate change.

  16. Late Holocene climate variability in the Sahel: inferences from a marine dust record offshore Senegal

    NASA Astrophysics Data System (ADS)

    Stuut, Jan-Berend; Mulitza, Stefan; Heslop, David; Pittauerova, Daniela; Fischer, Helmut; Zabel, Matthias; Collins, James; Kuhnert, Henning; Mollenhauer, Gesine; Meyer, Inka

    2010-05-01

    Societies and ecosystems in northern Africa are strongly affected by the availability of water. As a consequence, long-term absence of rainfall has very dear effects on the ecosystems, as was dramatically shown in the 70'ies and 80'ies of the 20 century. Recent high-resolution reconstructions of Sahel palaeoclimate allow for new insights into these drastic climate variations and to disentangle the effects of the different components of the climate system on African climate change. In this study we extend the instrumental record of climate variability using a marine sediment core that was retrieved off the coast of Senegal, northwest Africa. The 530-cm long record covers the last 4,000 years continuously. A Pb age model allows for a matching of the proxy record with instrumental data. Specifically, variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997) are used to reconstruct rainfall variability on land. In addition, chemical data are used to study the effect of human-induced dust production throughout the late Holocene. We show that dust deposition is closely related to monsoonal precipitation in West Africa until the 17th century AD, followed by a sharp increase in dust deposition at the beginning of the 18th century. We hypothesise that this increase in dust mobilisation is related to the advent of commercial agriculture in the Sahel region.

  17. Development, Production and Validation of the NOAA Solar Irradiance Climate Data Record

    NASA Astrophysics Data System (ADS)

    Coddington, O.; Lean, J.; Pilewskie, P.; Snow, M. A.; Lindholm, D. M.

    2015-12-01

    A new climate data record of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI), including source code and supporting documentation is now publicly available as part of the National Oceanographic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) Climate Data Record (CDR) Program. Daily and monthly averaged values of TSI and SSI, with associated time and wavelength dependent uncertainties, are estimated from 1882 to the present with yearly averaged values since 1610, updated quarterly for the foreseeable future. The new Solar Irradiance Climate Data Record, jointly developed by the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics (LASP) and the Naval Research Laboratory (NRL), is constructed from solar irradiance models that determine the changes from quiet Sun conditions when bright faculae and dark sunspots are present on the solar disk. The magnitudes of the irradiance changes that these features produce are determined from linear regression of the proxy Mg II index and sunspot area indices against the approximately decade-long solar irradiance measurements made by instruments on the SOlar Radiation and Climate Experiment (SORCE) spacecraft. We describe the model formulation, uncertainty estimates, operational implementation and validation approach. Future efforts to improve the uncertainty estimates of the Solar Irradiance CDR arising from model assumptions, and augmentation of the solar irradiance reconstructions with direct measurements from the Total and Spectral Solar Irradiance Sensor (TSIS: launch date, July 2017) are also discussed.

  18. Pathfinder Version 5.3 AVHRR Sea Surface Temperature Climate Data Record

    NASA Astrophysics Data System (ADS)

    Baker-Yeboah, S.; Kilpatrick, K. A.

    2016-12-01

    Long-term, climate data records of global sea surface temperature (SST) are important for ocean and climate variability studies. The NOAA National Centers for Environmental Information process, maintain, and continue development of the long-term, Pathfinder climate data record of global SST. These SST values are generated at approximately a 4 km resolution using a consistent algorithm for Advanced Very High Resolution Radiometer (AVHRR) instruments aboard NOAA polar-orbiting satellites dating back to 1981. A new version of the Pathfinder SST products, version 5.3, has recently been produced for a thirty three year period (1981 - 2014). This latest reprocessing used an Amazon Web Service cloud system and a modernized version of the heritage Pathfinder SST codes integrated into the open source NASA SeaWiFS Data Analysis System (SeaDAS6.4). Coefficients for this SST product were generated using regression analyses with co-located in situ and satellite measurements. Validation results corresponding to Pathfinder Level 3 skin SST minus sub-surface buoy SST show a global mean difference of -0.2 K with a standard deviation of 0.5 K. New quality control procedures for the new version of Pathfinder SST Climate Data Record products will be presented along with other improvements made in comparison to previous versions of Pathfinder SST.

  19. A maturity model for assessing the completeness of climate data records

    NASA Astrophysics Data System (ADS)

    Bates, John J.; Privette, Jeffrey L.

    2012-10-01

    The demand for climate information, with long observational records spanning decades to centuries and the information's broad application for decision making across many socioeconomic sectors, requires that geophysicists adopt more rigorous processes for the sustained production of climate data records (CDRs). Such processes, methods, and standards are more typically found in the systems engineering community and have not generally been adopted in the climate science community. We propose the use of a maturity matrix for climate data records that characterizes the process of moving from a basic research product (e.g., raw data and initial product) to a sustained and routinely generated product (e.g., a quality-controlled homogenized data set). This model of increasing product and process maturity is similar to NASA's technical readiness levels for flight hardware and instrumentation and the software industry's capability maturity model. Over time, engineers who have worked on many projects developed a set of best practices that identified the processes required to optimize cost, schedule, and risk. In the NASA maturity model, they identified steps in technology readiness, denoted as the technology readiness level (TRL). TRL 1 occurs when basic research has taken the first steps toward application. TRL 9 is when a technology has been fully proven to work consistently for the intended purpose and is operational.

  20. A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change

    USGS Publications Warehouse

    Peck, J.A.; King, J.W.; Colman, Steven M.; Kravchinsky, V.A.

    1994-01-01

    Rock-magnetic measurements of sediment cores from the Academician Ridge region of Lake Baikal, Siberia show variations related to Late Quaternary climate change. Based upon the well-dated last glacial-interglacial transition, variations in magnetic concentration and mineralogy are related to glacial-interglacial cycles using a conceptual model. Interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals. Glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals. The variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods. We also infer an increased contribution of eolian sediment during the colder, windier, and more arid glacial conditions when extensive loess deposits were formed throughout Europe and Asia. Eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals. Variations in magnetic concentration and mineralogy of Lake Baikal sediment correlate to the SPECMAP marine oxygen-isotope record. The high degree of correlation between Baikal magnetic concentration/mineralogy and the SPECMAP oxygen-isotope record indicates that Lake Baikal sediment preserves a history of climate change in central Asia for the last 250 ka. This correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method. Future work must include providing better age control and additional climate proxy data, thereby strengthening the correlation of continental and marine climate records. ?? 1994.

  1. Fjord sediment record of Holocene climate change in the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Anderson, John; Minzoni, Rebecca; Wellner, Julia; Majewski, Wojciech

    2014-05-01

    High-resolution paleoclimate records were generated from long sediment cores collected in five fjords of drastically different settings in the Antarctic Peninsula (AP), including Maxwell Bay, Firth of Tay, Herbert Sound, Lapeyrère Bay, and Neny Fjord. These results are augmented by published records from open marine settings of the Palmer Deep and Bransfield Basin and from terrestrial studies to obtain sufficient spatial sampling for regional analysis of Holocene climate events and local forcing mechanisms. These records include SHALDRIL cores acquired through some of the thicker (up to 108 meters) Holocene sections in fjords of the northern AP region. Robust radiocarbon chronology has been established for each site, and several paleoclimate proxies have been applied to identify and characterize climate events. These include magnetic susceptibility, sedimentation rates, grain size, pebble content, TOC, stable isotopes, biogenic silica content, and foraminifera and diatom assemblages. Current data analysis, including application of additional proxies and analysis of additional cores, refines our understanding of the nature and timing of climatic events expressed in each site. Five previously recognized climate intervals are recorded throughout the AP: an early Holocene deglacial interval, the Mid-Holocene Climate Optimum, a minor cooling event in the mid-Holocene followed by a minor warming event, and the late Holocene Neoglacial. The magnitude and timing of these events varies widely--up to a few thousand years--across the AP region and reflects differences in factors such as orographic effects, drainage basin size and altitude, wind patterns, oceanography, and sea-ice coverage. These results suggest that the rapid regional warming and widespread glacial retreat observed during the last century is unprecedented in breadth and synchronicity.

  2. A 2000 year varve-based climate record from the central Brooks Range, Alaska

    SciTech Connect

    Bird, B.W.; Abbott, M.B.; Finney, B.P.; Kutchko, Barbara

    2009-01-01

    Varved minerogenic sediments from glacial-fed Blue Lake, northern Alaska, are used to investigate late Holocene climate variability. Varve thickness measurements track summer temperature recorded at Atigun Pass, located 41 km east at a similar elevation (r2 = 0.31, P = 0.08). Results indicate that climate in the Brooks Range from 10 to 730 AD (varve year) was warm with precipitation inferred to be higher than during the twentieth century. The varve-temperature relationship for this period was likely compromised and not used in our temperature reconstruction because the glacier was greatly reduced, or absent, exposing sub-glacial sediments to erosion from enhanced precipitation.

  3. Continuous 500,000-year climate record from vein calcite in devils hole, nevada.

    PubMed

    Winograd, I J; Coplen, T B; Landwehr, J M; Riggs, A C; Ludwig, K R; Szabo, B J; Kolesar, P T; Revesz, K M

    1992-10-09

    Oxygen-18 (delta(18)O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine delta(18)O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

  4. Uranium-series dating of sediments from searles lake: differences between continental and marine climate records.

    PubMed

    Bischoff, J L; Rosenbauer, R J; Smith, G I

    1985-03-08

    One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial delta(18)O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 x 10(6) years. Uraniumseries dates on the salt beds range from 35 x 10(3) to 231x 10(3) years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.

  5. Uranium-series dating of sediments from Searles Lake: Differences between continental and marine climate records

    USGS Publications Warehouse

    Bischoff, J.L.; Rosenbauer, R.J.; Smith, G.I.

    1985-01-01

    One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial ??18O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 ?? 106 years. Uranium-series dates on the salt beds range from 35 ?? 103 to 231 ?? 103 years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.

  6. Continuous 500,000-year climate record from vein calcite in Devils Hole, Nevada

    USGS Publications Warehouse

    Winograd, I.J.; Coplen, T.B.; Landwehr, J.M.; Riggs, A.C.; Ludwig, K. R.; Szabo, B. J.; Kolesar, Peter T.; Revesz, K.M.

    1992-01-01

    Oxygen-18 (??18O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine ??18O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

  7. In Search of Sun-Climate Connection Using Solar Irradiance Measurements and Climate Records

    NASA Technical Reports Server (NTRS)

    Kiang, Richard K.; Kyle, H. Lee

    2000-01-01

    The Earth's temperature has risen approximately 0.5 degree-C in the last 150 years. Because the atmospheric concentration of carbon dioxide has increased nearly 30% since the industrial revolution, a common conjecture, supported by various climate models, is that anthropogenic greenhouse gases have contributed to global warming. Another probable factor for the warming is the natural variation of solar irradiance. Although the variation is as small as 0.1 % it is hypothesized that it contributes to part of the temperature rise. Warmer or cooler ocean temperature at one part of the Globe may manifest as abnormally wet or dry weather patterns some months or years later at another part of the globe. Furthermore, the lower atmosphere can be affected through its coupling with the stratosphere, after the stratospheric ozone absorbs the ultraviolet portion of the solar irradiance. In this paper, we use wavelet transforms based on Morlet wavelet to analyze the time-frequency properties in several datasets, including the Radiation Budget measurements, the long-term total solar irradiance time series, the long-term temperature at two locations for the North and the South Hemisphere. The main solar cycle, approximately 11 years, are identified in the long-term total solar irradiance time series. The wavelet transform of the temperature datasets show annual cycle but not the solar cycle. Some correlation is seen between the length of the solar cycle extracted from the wavelet transform and the North Hemisphere temperature time series. The absence of the 11-year cycle in a time series does not necessarily imply that the geophysical parameter is not affected by the solar cycle; rather it simply reflects the complex nature of the Earth's response to climate forcings.

  8. Climatic correlations in the stable isotope records of silver fir ( Abies pindrow) trees from Kashmir, India

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Bhattacharya, S. K.; Gopalan, K.

    1986-08-01

    A high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the Kashmir Valley has recently been reported by us. Since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site, we have compared the mean δD, δ 13C and δ 18O records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record. A multiple regression analysis of the two records for the period 1903-1932 yields the following: (1) δD is most sensitive to the amount of growing season precipitation, followed by mean maximum temperature. Tree cellulose shows an amount effect analogous to precipitation samples. The temperature coefficient for δD is in good agreement with earlier estimates based on spatial correlations. (2) δ 13C is significantly related to humidity and cloud amount. The signs of the regression coefficients are consistent with the recent model of Francey and Farquhar for 13C/ 12C fractionation in C 3 plants. (3) δ 18O of cellulose appears to be controlled significantly by relative humidity. 18O shows less overall correlation with climatic parameters than δD and δ 13C. (4) δD of carbon bound hydrogen and δ 18O of tree cellulose are linearly related with a slope of7.9 ± 0.3, suggesting evaporative enrichment in leaf water.

  9. Controls, variation, and a record of climate change in detailed stable isotope record in a single bryozoan skeleton

    NASA Astrophysics Data System (ADS)

    Smith, Abigail M.; Key, Marcus M., Jr.

    2004-03-01

    The long-lived (about 20 yr) bryozoan Adeonellopsis sp. from Doubtful Sound, New Zealand, precipitates aragonite in isotopic equilibrium with seawater, exerting no metabolic or kinetic effects. Oxygen isotope ratios (δ 18O) in 61 subsamples (along three branches of a single unaltered colony) range from -0.09 to +0.68‰ PDB (mean = +0.36‰ PDB). Carbon isotope ratios (δ 13C) range from +0.84 to +2.18‰ PDB (mean = +1.69‰ PDB). Typical of cool-water carbonates, δ 18O-derived water temperatures range from 14.2 to 17.5 °C. Adeonellopsis has a minimum temperature growth threshold of 14 °C, recording only a partial record of environmental variation. By correlating seawater temperatures derived from δ 18O with the Southern Oscillation Index, however, we were able to detect major events such as the 1983 El Niño. Interannual climatic variation can be recorded in skeletal carbonate isotopes. The range of within-colony isotopic variability found in this study (0.77‰ in δ 18O and 1.34 in δ 13C) means that among-colony variation must be treated cautiously. Temperate bryozoan isotopes have been tested in less than 2% of described extant species — this highly variable phylum is not yet fully understood.

  10. Solving the Global Climate Monitoring Problem in the Atmosphere: Towards SI-tied Climate Records with Integrated Uncertainty Propagation

    NASA Astrophysics Data System (ADS)

    Kirchengast, G.; Schwaerz, M.; Fritzer, J.; Schwarz, J.; Scherllin-Pirscher, B.; Steiner, A. K.

    2013-12-01

    Monitoring the atmosphere to gain accurate and long-term stable records of essential climate variables (ECVs) such as temperature and greenhouse gases is the backbone of contemporary atmospheric and climate science. Earth observation from space is the key to obtain such data globally in the atmosphere. Currently, however, not any existing satellite-based atmospheric ECV record can serve as authoritative benchmark over months to decades so that climate variability and change in the atmosphere are not yet reliably monitored. Radio occultation (RO) using Global Navigation Satellite System (GNSS) signals provides a unique opportunity to solve this problem in the free atmosphere (from ~1-2 km altitude upwards) for core ECVs: the thermodynamic variables temperature and pressure, and to some degree water vapor, which are key parameters for tracking climate change. On top of RO we have recently conceived next-generation methods, microwave and infrared-laser occultation and nadir-looking infrared-laser reflectometry. These can monitor a full set of thermo-dynamic ECVs (incl. wind) as well as the greenhouse gases such as carbon dioxide and methane as main drivers of climate change; for the latter we also target the boundary layer for tracking carbon sources and sinks. We briefly introduce to why the atmospheric climate monitoring challenge is unsolved so far and why just the above methods have the capabilities to break through. We then focus on RO, which already provided more than a decade of observations. RO accurately measures time delays from refraction of GNSS signals during atmospheric occultation events. This enables to tie RO-derived ECVs and their uncertainty to fundamental time standards, effectively the SI second, and to their unique long-term stability and narrow uncertainty. However, despite impressive advances since the pioneering RO mission GPS/Met in the mid-1990ties no rigorous trace from fundamental time to the ECVs (duly accounting also for relevant side

  11. Climate or land-use change? Complexities in the attribution of trends in river flow records

    NASA Astrophysics Data System (ADS)

    Harrigan, S.; Murphy, C.; Noone, S.; Wilby, R. L.; Hall, J.

    2012-12-01

    Uncertainty associated with projections of regional climate change and the challenge of developing adaptation responses are heightening interest in trend detection from observations. In many studies, attribution of detected trends in river flow has been based on the assessment of correlations with large scale modes of climate variability, with too little emphasis being placed on understanding non-climatic changes within the catchment. The River Boyne in Ireland has been cited as exhibiting a climate driven increase in river flows associated with a shift towards positive anomalies in the North Atlantic Oscillation Index (NAOI) from the mid to late 1970s. However, metadata suggests that the catchment was subjected to extensive arterial drainage during the period 1969-86. This was installed to improve land drainage and reduce the frequency/ extent of overland flooding, particularly through river straightening and channel deepening, complicating the attribution of change linked to climatic drivers. This study uses river flow records from the pre-drainage period along with meteorological data to calibrate conceptual rainfall runoff models in order to reconstruct continuous flow series spanning the pre- and post-drainage eras. Model parameter and structure uncertainties were explored via a suite of conceptually and structurally diverse models. Archival rainfall records dating from the late 1800s were used to further extend the flow series. Reconstructed flows are analyzed for both monotonic and step changes using a variety of statistical tests. Emphasis is placed on a moving windows approach to assess the evolution of trends throughout the reconstructed series. Our results show that the variability of trends (direction, magnitude and significance) is heavily dependent on the choice of record start and end dates. Rather than being associated with a change point in the NAOI, the mid 1970s step change is shown to coincide with the documented changes in arterial drainage

  12. Decadal-scale variability in climate proxy records: a search for tidal and solar forcing

    NASA Astrophysics Data System (ADS)

    Berger, W.; Paetzold, J.; Wefer, G.

    2003-04-01

    Decadal-scale climate- and ocean variability is an unsolved problem. The geologic record holds a number of clues as to possible forcing functions; useful proxy series are in ice cores, corals, biogenic deposits in anaerobic basins, marine varves and small turbidites, in the sea and in lakes. Certain decadal-scale cycles seem to occur more commonly than others, and in a number of records with an entirely different pedigree, suggesting effects from outside forcing. If we assume that both solar forcing and tidal forcing play some role (as supported by spectra from corals and varves), we should expect interference between the respective forcing functions. From such interference, we can calculate the most likely periods to be found. Analysis of an 800-y coral record from Bermuda suggests that such interference periods are expressed in this proxy record.

  13. Maximum rates of climate change are systematically underestimated in the geological record

    NASA Astrophysics Data System (ADS)

    Kemp, David B.; Eichenseer, Kilian; Kiessling, Wolfgang

    2015-11-01

    Recently observed rates of environmental change are typically much higher than those inferred for the geological past. At the same time, the magnitudes of ancient changes were often substantially greater than those established in recent history. The most pertinent disparity, however, between recent and geological rates is the timespan over which the rates are measured, which typically differ by several orders of magnitude. Here we show that rates of marked temperature changes inferred from proxy data in Earth history scale with measurement timespan as an approximate power law across nearly six orders of magnitude (102 to >107 years). This scaling reveals how climate signals measured in the geological record alias transient variability, even during the most pronounced climatic perturbations of the Phanerozoic. Our findings indicate that the true attainable pace of climate change on timescales of greatest societal relevance is underestimated in geological archives.

  14. Maximum rates of climate change are systematically underestimated in the geological record

    PubMed Central

    Kemp, David B.; Eichenseer, Kilian; Kiessling, Wolfgang

    2015-01-01

    Recently observed rates of environmental change are typically much higher than those inferred for the geological past. At the same time, the magnitudes of ancient changes were often substantially greater than those established in recent history. The most pertinent disparity, however, between recent and geological rates is the timespan over which the rates are measured, which typically differ by several orders of magnitude. Here we show that rates of marked temperature changes inferred from proxy data in Earth history scale with measurement timespan as an approximate power law across nearly six orders of magnitude (102 to >107 years). This scaling reveals how climate signals measured in the geological record alias transient variability, even during the most pronounced climatic perturbations of the Phanerozoic. Our findings indicate that the true attainable pace of climate change on timescales of greatest societal relevance is underestimated in geological archives. PMID:26555085

  15. Late Cretaceous climate changes recorded in Eastern Asian lacustrine deposits and North American Epieric sea strata

    NASA Astrophysics Data System (ADS)

    Wang, Chengshan; Scott, Robert W.; Wan, Xiaoqiao; Graham, Stephan A.; Huang, Yongjian; Wang, Pujun; Wu, Huaichun; Dean, Walter E.; Zhang, Laiming

    2013-11-01

    Cretaceous climate data of the long-lived Cretaceous Songliao Basin (SB) in eastern Asia is correlated and compared with the Western Interior Seaway (WIS) on the northern American plate, in order to understand better the dynamics of the Earth's past 'greenhouse' climates. Nearly continuous Late Cretaceous terrestrial deposition in the Songliao Basin is represented by two cores totaling 2431 m in length. The Turonian-Maastrichtian age of the section is based on integrated stratigraphy, and is comparable in age with Upper Cretaceous strata in the WIS. Being consistent with global trends, the dynamic Late Cretaceous climates of both the SB and WIS gradually cooled from the warmest Albian-Cenomanian time to the end of the Maastrichtian with several intervening warm periods as did the global climate. However regional differences existed, the Songliao Basin climate was humid to semi-humid, warm temperate-subtropical and the Western Interior Seaway was in the humid, warm temperate zone and experienced only moderate climatic changes. The shifts of oxygen isotope data in the Songliao Basin were frequent and abrupt, whereas WIS records more gradual change affected mainly by fresh-water runoff mixing with southern Tethyan and northern Arctic waters. Sedimentary cycles of eccentricity, obliquity and precession bands are recorded in both the SB and WIS basins. The sedimentary cycles in the WIS and SB are interpreted to be related to variations of the wet/dry runoff cycles, which indicate that orbital forcing played an important role in global climate change in Late Cretaceous. The most favorable condition for organic carbon burial in both the SB and WIS basin was bottom water anoxia regardless of the cause of the anoxia. But the organic carbon burial rate was usually much higher in the Songliao Lake than in the WI epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric CO2. In both basins organic-rich deposits formed during a rise in water level and

  16. 30,000-Year Record of Climate From the Galapagos Islands and Links With High Latitudes

    NASA Astrophysics Data System (ADS)

    Koutavas, A.; Lynch-Stieglitz, J.; Sachs, J. P.; Marchitto, T. M.

    2001-12-01

    The eastern equatorial Pacific (EEP) upwelling system influences climate on a global scale as manifested by the far-reaching teleconnections of El Nino-Southern Oscillation (ENSO). It is postulated that this system has played a primary role in orbital and millennial scale climate variability of the late Quaternary, but a test of this hypothesis has been hampered by a lack of high-resolution regional climate records. New tools for sea-surface temperature (SST) reconstruction, including Mg/Ca ratios in foraminifera and alkenone unsaturation ratios in bulk sediment, offer the potential for deconvolving the sea-surface temperature signal from oxygen-isotope records dominated by the isotopic composition of seawater. Application of these methods in the EEP upwelling region is beginning to place important constraints on past SST variability, nevertheless a detailed history of regional SST evolution during the last deglaciation has been lacking due to a virtual absence of high-resolution records from the core of the EEP upwelling tongue. We present a radiocarbon-dated, millennial resolution climate record of the last 30,000 years from a sediment core near the Galapagos Islands. This site is unique in its combination of (a) a high sedimentation rate (13 cm/ky), (b) a shallow depth (617 m), and (c) a southern equatorial position (1.2° S). Collectively these characteristics help circumvent bioturbation and dissolution problems in a site proximal to the core of the upwelling tongue that develops primarily south of the equator. Despite a modest glacial-interglacial SST amplitude of \\sim1.5oC based on alkenones and δ 18O, millennial-scale oscillations in SST as well as in foraminiferal δ 18O and δ 13C suggest links with Northern Hemisphere climate involving EEP upwelling variability. However, SST is decoupled from upwelling during parts of the record, which calls for the opposing influence of some other mechanism(s). A key candidate for this role may be advection of climate

  17. Early last glacial intra-interstadial climate variability recorded in a Sardinian speleothem

    NASA Astrophysics Data System (ADS)

    Columbu, Andrea; Drysdale, Russell; Capron, Emilie; Woodhead, Jon; De Waele, Jo; Sanna, Laura; Hellstrom, John; Bajo, Petra

    2017-08-01

    Chemical and physical proxy data from a precisely dated early last glacial (∼113-110 ka, MIS5d) Sardinian stalagmite reveal a sub-millennial-scale, cool-dry climate event centered at 112.0 +0.52/-0.59 ka, followed by a rapid return to warm-wet conditions at 111.76 +0.43/-0.45 ka. Comparison with regional speleothem records and the palaeotemperature proxy record from the NGRIP ice core (Greenland) suggests that this event corresponds to Greenland Interstadial (GI) 25b and 25a, an intra-interstadial climate oscillation within GI-25, according to the recent Greenland stratigraphic framework. The speleothem age is in reasonable agreement (within 0.8 kyr) with that of the corresponding event in Greenland based on the GICC05modelext ice chronology but is older by about 3.7 kyr than the Greenland age based on the AICC2012 chronology.

  18. Annually resolved ice core records of tropical climate variability over the past ~1800 years.

    PubMed

    Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

    2013-05-24

    Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

  19. Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa.

    PubMed

    Thompson, Lonnie G; Mosley-Thompson, Ellen; Davis, Mary E; Henderson, Keith A; Brecher, Henry H; Zagorodnov, Victor S; Mashiotta, Tracy A; Lin, Ping-Nan; Mikhalenko, Vladimir N; Hardy, Douglas R; Beer, Jürg

    2002-10-18

    Six ice cores from Kilimanjaro provide an approximately 11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: approximately 8.3, approximately 5.2, and approximately 4 thousand years ago (ka). The latter is coincident with the "First Dark Age," the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between approximately 11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased approximately 80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020.

  20. Interaction between the ENSO and the Asian monsoon in a coral record of tropical climate

    SciTech Connect

    Charles, C.D.; Hunter, D.E.; Fairbanks, R.G.

    1997-08-15

    The oxygen isotopic composition of a banded coral from the western equatorial Indian Ocean provides a 150-year-long history of the relation between the El Nino-Southern Oscillation (ENSO) phenomenon and the Asian monsoon. Interannual cycles in the coral time series were found to correlate with Pacific coral and instrumental climate records, suggesting a consistent linkage across ocean basins, despite the changing frequency and amplitude of the ENSO. However, decadal variability that is characteristic of the monsoon system also dominates the coral record, which implies important interactions between tropical and midlatitude climate variability. One prominent manifestation of this interaction is the strong amplitude modulation of the quasi-biennial cycle. 26 refs., 4 figs.

  1. Svalbard Climate Variability During the Past 200 Years as Recorded in two Ice Cores

    NASA Astrophysics Data System (ADS)

    Isaksson, E.; Kohler, J.; Igarashi, M.; Motoyama, H.; Martma, T.; Meijer, H.; Kekkonen, T.; Moore, J.; Mulvaney, R.; Pohjola, V.

    2001-12-01

    Ice cores from the relatively low-lying icecaps in Svalbard have not been widely exploited in climatic studies due to uncertainties about the effect of melt water percolation. However, results from two new Svalbard ice cores, at Lomonosovfonna and Austfonna, have shown that with careful site selection, high-resolution sampling and multiple chemical analysis, it is possible to recover ice cores whose annual signals are preserved. The new Svalbard ice core sites are positioned in different parts of Svalbard, with different climatic influences. We compare the two sites' \\delta18O and deuterium records with air temperature and sea ice extent records over the two last centuries. The \\delta18O data from the cores are relatively similar over most of the 20th century, suggesting that they record the same atmospheric signal. Prior to 1920, the Austfonna ice core exhibits more negative \\delta18O values than Lomonosovfonna, but there are intermittent decadal-scale periods throughout the record with similar values. Comparing the ice core and sea ice records from this period suggests that sea ice extent is largely responsible for these differences.

  2. Using image reconstruction methods to enhance gridded resolutionfor a newly calibrated passive microwave climate data record

    NASA Astrophysics Data System (ADS)

    Paget, A. C.; Brodzik, M. J.; Gotberg, J.; Hardman, M.; Long, D. G.

    2014-12-01

    Spanning over 35 years of Earth observations, satellite passive microwave sensors have generated a near-daily, multi-channel brightness temperature record of observations. Critical to describing and understanding Earth system hydrologic and cryospheric parameters, data products derived from the passive microwave record include precipitation, soil moisture, surface water, vegetation, snow water equivalent, sea ice concentration and sea ice motion. While swath data are valuable to oceanographers due to the temporal scales of ocean phenomena, gridded data are more valuable to researchers interested in derived parameters at fixed locations through time and are widely used in climate studies. We are applying recent developments in image reconstruction methods to produce a systematically reprocessed historical time series NASA MEaSUREs Earth System Data Record, at higher spatial resolutions than have previously been available, for the entire SMMR, SSM/I-SSMIS and AMSR-E record. We take advantage of recently released, recalibrated SSM/I-SSMIS swath format Fundamental Climate Data Records. Our presentation will compare and contrast the two candidate image reconstruction techniques we are evaluating: Backus-Gilbert (BG) interpolation and a radiometer version of Scatterometer Image Reconstruction (SIR). Both BG and SIR use regularization to trade off noise and resolution. We discuss our rationale for the respective algorithm parameters we have selected, compare results and computational costs, and include prototype SSM/I images at enhanced resolutions of up to 3 km. We include a sensitivity analysis for estimating sensor measurement response functions critical to both methods.

  3. Abrupt climate changes of the last deglaciation detected in a western Mediterranean forest record

    NASA Astrophysics Data System (ADS)

    Fletcher, W. J.; Sanchez Goñi, M. F.; Peyron, O.; Dormoy, I.

    2009-01-01

    Evidence for abrupt changes in western Mediterranean climate between 20 and 6 cal ka BP is examined in marine core MD95-2043 (Alborán Sea), using pollen data for temperate Mediterranean forest development and pollen-based climate reconstructions using the modern analogue technique (MAT) for annual precipitation (Pann) and mean temperatures of the coldest and warmest months (MTCO and MTWA). Major climatic shifts with parallel temperature and precipitation changes occurred at the onsets of Heinrich Event 1 (equivalent to the Oldest Dryas), the Bölling-Allerød (BA), and the Younger Dryas (YD). Multi-centennial-scale oscillations in forest development related to regional precipitation (Pann) variability occurred throughout the BA, YD, and early Holocene, with drier atmospheric conditions in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas), GI-1b (Intra-Allerød Cold Period) and GS-1 (YD), and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting (events at 11.4, 10.1, 9.3, 8.2 and 7.4 cal ka BP). The forest record also indicates multi-centennial variability within the YD interval and multiple Preboreal climate oscillations. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to western-central Europe relates to the dynamics of the jet stream and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alborán Sea by ~200 years (surface water age ~600 years) during the Lateglacial.

  4. NALPS: a precisely dated European climate record 120-60 ka

    NASA Astrophysics Data System (ADS)

    Boch, R.; Cheng, H.; Spötl, C.; Edwards, R. L.; Wang, X.; Häuselmann, Ph.

    2011-03-01

    Accurate and precise chronologies are essential in understanding the rapid and recurrent climate variations of the Last Glacial - known as Dansgaard-Oeschger (D-O) events - found in the Greenland ice cores and other climate archives. The existing chronological uncertainties during the Last Glacial, however, are still large. Radiometric age data and stable isotopic signals from speleothems are promising to improve the absolute chronology. We present a record of several precisely dated stalagmites from caves located at the northern rim of the Alps (NALPS), a region that favours comparison with the climate in Greenland. The record covers most of the interval from 120 to 60 ka at an average temporal resolution of 2 to 22 a and 2 σ-age uncertainties of ca. 200 to 500 a. The rapid and large oxygen isotope shifts of 1 to 4.5‰ occurred within decades to centuries and strongly mimic the Greenland D-O pattern. Compared to the current Greenland ice-core timescale the NALPS record suggests overall younger ages of rapid warming and cooling transitions between 120 to 60 ka. In particular, there is a discrepancy in the duration of stadial 22 between the ice-core and the stalagmite chronology (ca. 3000 vs. 3650 a). The short-lived D-O events 18 and 18.1 are not recorded in NALPS, provoking questions with regard to the nature and the regional expression of these events. NALPS resolves recurrent short-lived climate changes within the cold Greenland stadial (GS) and warm interstadial (GI) successions, i.e. abrupt warming events preceding GI 21 and 23 (precursor-type events) and at the end of GI 21 and 25 (rebound-type events), as well as intermittent cooling events during GI 22 and 24. Such superimposed Last Glacial events have not been documented in Europe before.

  5. Reconstruction of climate in China during 17th-19th centuries using Chinese chronological records

    NASA Astrophysics Data System (ADS)

    Wang, Pao; Lin, Kuan-Hui; Liao, Yi-Chun; Lee, Shih-Yu; Liao, Hsiung-Ming; Pai, Pi-Ling; Fan, I.-Chun

    2017-04-01

    Chinese historical documents are an extremely useful source from which much climate information can be retrieved if treated carefully. This is especially relevant to the reconstruction of climate in East Asia in the last 2000 years as the Chinese has kept official chronicles since 500BC and China also represents a large portion of East Asia's land. In addition, there are also local records in many cities and counties. When available, such documentary sources are often superior to environmental proxy data, especially in the time resolution as they usually provide at least annual resolution and even as high as daily records in some cases. This research will report on our recent advances on using a new REACHS dataset that collects primarily documented meteorological records from thousands of imperial and local chronicles in the Chinese history for more than 2000 years. The meteorological records were digitized and coded in the relational database management system in which accurate time (from yearly to daily), space (from province to city/county) and event (from meteorological to phonological and social) information is carefully reserved for analysis. We then formed digital climate series and performed time series and spatial analysis on them to obtain their temporal and spatial characteristics. Our present research results on the annual and seasonal temperature reconstruction during 17th-19th indicates lower temperature in the 17th century. There were also strangely high occurrence frequency of summer snowfall records in the lower reaches of Yangtze River during the Maunder Minimum. Reconstructed precipitation series fluctuated with strong regional character in the Northeast, Central-east and Southeast China. Spectral analysis shows that precipitation series have significant periodicity of 3-5 and 8-12 years during the period, suggesting strong interannual variability and different regional signatures. Flood happened frequently but long lasting drought was more

  6. A pathway to generating Climate Data Records of sea-surface temperature from satellite measurements

    NASA Astrophysics Data System (ADS)

    Minnett, Peter J.; Corlett, Gary K.

    2012-11-01

    In addition to having known uncertainty characteristics, Climate Data Records (CDRs) of geophysical variables derived from satellite measurements must be of sufficient length to resolve signals that might reveal the signatures of climate change against a background of larger, unrelated variability. The length of the record requires using satellite measurements from many instruments over several decades, and the uncertainty requirement implies that a consistent approach be used to establish the errors in the satellite retrievals over the entire period. Retrieving sea-surface temperature (SST) from satellite is a relatively mature topic, and the uncertainties of satellite retrievals are determined by comparison with collocated independent measurements. To avoid the complicating effects of near-surface temperature gradients in the upper ocean, the best validating measurements are from ship-board radiometers that measure, at source, the surface emission that is measured in space, after modification by its propagation through the atmosphere. To attain sufficient accuracy, such ship-based radiometers must use internal blackbody calibration targets, but to determine the uncertainties in these radiometric measurements, i.e. to confirm that the internal calibration is effective, it is necessary to conduct verification of the field calibration using independent blackbodies with accurately known emissivity and at very accurately measured temperatures. This is a well-justifiable approach to providing the necessary underpinning of a Climate Data Record of SST.

  7. Continental climate response to orbital forcing from biogenic silica records in Lake Baikal

    USGS Publications Warehouse

    Colman, Steven M.; Peck, J.A.; Karabanov, E.B.; Carter, Susan J.; Bradbury, J.P.; King, J.W.; Williams, D.F.

    1995-01-01

    CHANGES in insolation caused by periodic changes in the Earth's orbital parameters provide the primary forcing for global ice ages1-6. But it is not clear to what extent the climates in continental interiors are controlled directly by regional variations in insolation and to what extent they are driven instead by the highly nonlinear response of the oceans and ice sheets. Here we investigate this question using the record of biogenic silica in Lake Baikal as a proxy for climate change in this high-latitude mid-continental region. We find a good correlation between this record and that of marine oxygen isotopes4. Over the past 250 kyr the Baikal record exhibits both a strongly nonlinear component (manifested in a 100-kyr periodicity) and weaker direct-insolation components (manifested in the 41-kyr (obliquity) and 23- and 19-kyr (precession) orbital cycles). These results show that even though extreme continental climates such as this are influenced directly by insolation variations, they are dominated by the nonlinear rhythm of the oceans and ice sheets.

  8. Atmospheric Climate Change Detection Based on the GPS Radio Occultation Record

    NASA Astrophysics Data System (ADS)

    Steiner, A. K.; Lackner, B. C.; Hegerl, G. C.; Pirscher, B.; Borsche, M.; Foelsche, U.; Kirchengast, G.

    2009-04-01

    Monitoring of global climate change requires high quality observations of the Earth's atmosphere. Radio occultation (RO) measurements based on signals from Global Positioning System (GPS) satellites provide a useful upper air record in this respect. RO data are considered a climate benchmark data type since they are based on timing with precise atomic clocks and tied to the international definition of the second. High quality and vertical resolution in the upper troposphere and lower stratosphere (UTLS), long-term stability, and consistency of RO data stemming from satellites in different orbits without need for inter-calibration make RO well suited for atmospheric observations and climate change detection. RO data are available on a continuous basis since fall of 2001 from the German research satellite CHAMP (CHAllenging Minisatellite Payload for geoscientific research), establishing the first RO climate record covering more than seven years. Intermittent periods of observations from the U.S. GPS/Met proof-of-concept mission exist in the years 1995-1997, with sufficient data only for October 1995 and February 1997. We present a climate change detection study based on monthly mean zonal mean RO climatologies in the UTLS region within 9-25 km (300-30 hPa) where we use different detection methods. An optimal fingerprinting technique is applied to the whole record of RO accessible parameters refractivity, geopotential height, and temperature to detect a forced climate signal. Three representative global climate models of the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) are employed to estimate natural climate variability by making use of pre-industrial control runs. The response pattern to the external forcings is presented by an ensemble mean of the models' A2 and B1 scenario runs. Optimal fingerprinting shows that a climate change signal can be detected at the 90% significance level in the RO refractivity record. Furthermore, simple

  9. Future summer mega-heatwave and record-breaking temperatures in a warmer France climate

    NASA Astrophysics Data System (ADS)

    Bador, Margot; Terray, Laurent; Boé, Julien; Somot, Samuel; Alias, Antoinette; Gibelin, Anne-Laure; Dubuisson, Brigitte

    2017-07-01

    This study focuses on future very hot summers associated with severe heatwaves and record-breaking temperatures in France. Daily temperature observations and a pair of historical and scenario (greenhouse gas radiative concentration pathway 8.5) simulations with the high-resolution (∼12.5 km) ALADIN regional climate model provide a robust framework to examine the spatial distribution of these extreme events and their 21st century evolution. Five regions are identified with an extreme event spatial clustering algorithm applied to observed temperatures. They are used to diagnose the 21st century heatwave spatial patterns. In the 2070s, we find a simulated mega-heatwave as severe as the 2003 observed heatwave relative to its contemporaneous climate. A 20-member initial condition ensemble is used to assess the sensitivity of this future heatwave to the internal variability in the regional climate model and to pre-existing land surface conditions. Even in a much warmer and drier climate in France, late spring dry land conditions may lead to a significant amplification of summer extreme temperatures and heatwave intensity through limitations in evapotranspiration. By 2100, the increase in summer temperature maxima exhibits a range from 6 °C to almost 13 °C in the five regions in France, relative to historical maxima. These projections are comparable with the estimates given by a large number of global climate models.

  10. NOAA's Satellite Climate Data Records: The Research to Operations Process and Current State

    NASA Astrophysics Data System (ADS)

    Privette, J. L.; Bates, J. J.; Kearns, E. J.; NOAA's Climate Data Record Program

    2011-12-01

    In support of NOAA's mandate to provide climate products and services to the Nation, the National Climatic Data Center initiated the satellite Climate Data Record (CDR) Program. The Program develops and sustains climate information products derived from satellite data that NOAA has collected over the past 30+ years. These are the longest sets of continuous global measurements in existence. Data from other satellite programs, including those in NASA, the Department of Defense, and foreign space agencies, are also used. NOAA is now applying advanced analysis techniques to these historic data. This process is unraveling underlying climate trend and variability information and returning new value from the data. However, the transition of complex data processing chains, voluminous data products and documentation into an systematic, configuration controlled context involves many challenges. In this presentation, we focus on the Program's process for research-to-operations transition and the evolving systems designed to ensure transparency, security, economy and authoritative value. The Program has adopted a two-phase process defined by an Initial Operational Capability (IOC) and a Full Operational Capability (FOC). The principles and procedures for IOC are described, as well as the process for moving CDRs from IOC to FOC. Finally, we will describe the state of the CDRs in all phases the Program, with an emphasis on the seven community-developed CDRs transitioned to NOAA in 2011. Details on CDR access and distribution will be provided.

  11. Hemispherical Snow Water Equivalent Records of Satellite-Based Data and CMIP5 Climate Model Simulations

    NASA Astrophysics Data System (ADS)

    Luojus, Kari; Pulliainen, Jouni; Takala, Matias; Lemmetyinen, Juha; Smolander, Tuomo; Ikonen, Jaakko; Cohen, Juval; Derksen, Chris

    2013-04-01

    The European Space Agency (ESA) GlobSnow project has produced a daily hemisphere-scale satellite-based snow water equivalent (SWE) data record spanning more than 30-years. The GlobSnow SWE record, based on methodology by Pulliainen [1] utilizes a data-assimilation based approach for the estimation of SWE which was shown to be superior to the approaches depending solely on satellite-based data [2]. The GlobSnow SWE data record is based on the time-series of measurements by two different space-borne passive radiometers (SMMR and SSM/I) measuring in the microwave region, spanning from 1980 to present day at a spatial resolution of approximately 25 km. We briefly present the on-going efforts taking place for further enhancement of the satellite-based SWE retrieval and the way this transfers to the reliability of the long-term SWE climate record. The development of SWE retrieval are focused on application of a new HUT multi-layer snow emission model and variational snow density scheme for SWE retrieval and efforts carried out to improve the homogeneity of the long-term record of weather station-based snow depth observations that are applied within the SWE retrieval scheme. In addition, the GlobSnow satellite-based dataset is inter-compared with climate model simulations from the CMIP5 archive. The objective of this work is to investigate the performance of the CMIP5 models in capturing the evolution of hemispheric scale snow conditions for the period of 1980 to 2010. The climate model simulations on snow cover extent, snow depth and snow water equivalent are evaluated against the GlobSnow SWE record. The goal is to assess the performance of the CMIP5 models to simulate snow conditions for the time-period that is covered by satellite-based observations. The results indicate a clear decreasing trend in total hemispherical snow mass for the period of 1980 to 2010 in the remote-sensing based data record. The inter-comparison of satellite-based record and climate model

  12. Towards a Seamless Global Long-Term Earth Radiation Budget Climate Data Record

    NASA Astrophysics Data System (ADS)

    Loeb, N. G.; Priestley, K.; Minnis, P.; Smith, W. L., Jr.; Su, W.; Kratz, D. P.; Kato, S.; Doelling, D.

    2015-12-01

    Earth's climate is determined by the exchange of radiant energy between the Sun, Earth and space. The absorbed solar radiation (ASR) fuels the climate system, providing the energy required for atmospheric and oceanic motions, and energy released to space in the form of outgoing longwave radiation (OLR) nearly balances ASR, ensuring a relatively stable climate. Owing to human activities, there is currently less emitted thermal radiation than absorbed solar radiation, leading to an accumulation of energy into the Earth's system, which is driving global warming. Achieving an understanding of Earth's energy flows requires an accurate description of how radiant energy at the top-of-atmosphere (TOA), within the atmosphere, and at the surface is distributed spatially, and how this changes with time. A central objective of the Clouds and the Earth's Radiant Energy System (CERES) project is the production of a long-term global climate data record of Earth's radiation budget from the TOA down to the surface along with the associated atmospheric and surface properties that influence this budget. The CERES team relies on a number of data sources, including broadband radiometers that measure incoming and reflected solar radiation and OLR, high-resolution spectral imagers, meteorological, aerosol and ozone assimilation data, and snow/sea-ice maps based on microwave radiometer data. While TOA radiation budget is determined from accurate broadband radiometer measurements, the surface radiation budget is derived indirectly through radiative transfer model calculations initialized using imager-based cloud and aerosol retrievals and meteorological assimilation data. In order to accurately capture changes in Earth's radiation budget from interannual to decadal timescales, satellite instruments used to produce these data records must be radiometrically stable and the input data stream must be free of artificial discontinuities. Otherwise, distinguishing real climate system changes from

  13. Towards understanding North Pacific climate variabilty with instrumental and ice core records

    NASA Astrophysics Data System (ADS)

    Kelsey, Eric P.

    Reconstructing climate variability prior to the instrumental era is critical to advance our understanding of the Earth's climate system. Although many paleoclimate records from the North Atlantic basin have been studied, relatively few paleoclimate records have been recovered in the North Pacific leaving a gap in our knowledge concerning North Pacific climate variability. The Eclipse and Mount Logan Prospector-Russell ice cores are favorably located in the St. Elias Mountains, Yukon, Canada to document North Pacific climate variability over the late Holocene. Detailed analysis reveals a consistent relationship of surface air temperature (SAT) anomalies associated with extreme Arctic Oscillation (AO) and Pacific-North America (PNA) index values, and a consistent relationship of North Pacific sea level pressure (SLP) anomalies associated with extreme Mt. Logan annual [Na+] and Eclipse cold season accumulation values. Spatial SAT anomaly patterns are most consistent for AO and PNA index values ≥1.5 and ≤-1.5 during the period 1872-2010. The highest and lowest ˜10% of Eclipse warm and cold season stable isotopes are associated with distinct atmospheric circulation patterns. The most-fractionated isotope values occur with a weaker Aleutian Low, and the least-fractionated isotope values occur with an amplification of the Aleutian Low and northwestern North American ridge. The assumption of stationarity between ice core records and sea-level pressure was tested for the Eclipse cold season accumulation and Mt. Logan annual sodium concentration records for 1872-2001. A stationary relationship was found for ≥95% of years when Mt. Logan sodium concentrations were ≤1.32 microg/L, with positive SLP anomalies in the eastern North Pacific. This high frequency supports the use of low sodium values at Mt. Logan for a reconstruction of SLP prior to 1872. Negative SLP anomalies in the North Pacific occurred for extreme high sodium concentration years and positive SLP

  14. The Towuti Drilling Project: A new, long Pleistocene record of Indo-Pacific Climate

    NASA Astrophysics Data System (ADS)

    Russell, James M.; Vogel, Hendrik; Bijaksana, Satria; Melles, Martin

    2016-04-01

    Lake Towuti is the largest tectonic lake in Indonesia, and the longest known terrestrial sediment archive in Southeast Asia. Lake Towuti's location in central Indonesia provides an important opportunity to reconstruct long-term changes in terrestrial climate in the Western Pacific warm pool, heart of the El Niño-Southern Oscillation. Lake Towuti has extremely high rates of floral and faunal endemism and is surrounded by one of the most diverse tropical forests on Earth making it a hotspot of Southeast Asian biodiversity. The ultramafic rocks and soils surrounding Lake Towuti provide high concentrations of metals to the lake and its sediments that feed a diverse, exotic microbial community. From May - July, 2015, the Towuti Drilling Project, consisting of more than 30 scientists from eight countries, recovered over 1,000 meters of new sediment core from 3 different drill sites in Lake Towuti, including cores through the entire sediment column to bedrock. These new sediment cores will allow us to investigate the history of rainfall and temperature in central Indonesia, long-term changes in the composition of the region's rainforests and diverse aquatic ecosystems, and the micro-organisms living in Towuti's exotic, metal-rich sediments. The Indo-Pacific region plays a pivotal role in the Earth's climate system, regulating critical atmospheric circulation systems and the global concentration of atmospheric water vapor- the Earth's most important greenhouse gas. Changes in seasonal insolation, greenhouse gas concentrations, ice volume, and local sea level are each hypothesized to exert a dominant control on Indo-Pacific hydroclimate variations through the Pleistocene. Existing records from the region are short and exhibit fundamental differences and complexity in orbital-scale climate patterns that limit our understanding of the regional climate responses to climate boundary conditions. Our sediment cores, which span much of the past 1 million years, allow new tests of

  15. Combining intermediate complexity models and seasonal palaeo records: how to deal with model and climate variability?

    NASA Astrophysics Data System (ADS)

    de Boer, H. J.; Dekker, S. C.; Wassen, M. J.

    2009-04-01

    Earth System Models of Intermediate Complexity (EMICs) are popular tools for palaeo climate simulations. Recent studies applied these models in comparison to terrestrial proxy records and aimed to reconstruct changes in seasonal climate forced by altered ocean circulation patterns. To strengthen this powerful methodology, we argue that the magnitude of the simulated atmospheric changes should be considered in relation to the internal variability of both the climate system and the intermediate complexity model. To attribute a shift in modelled climate to reality, this ‘signal' should be detectable above the ‘noise' related to the internal variability of the climate system and the internal variability of the model. Both noise and climate signals vary over the globe and change with the seasons. We therefore argue that spatial explicit fields of noise should be considered in relation to the strengths of the simulated signals at a seasonal timescale. We approximated total noise on terrestrial temperature and precipitation from a 29 member simulation with the EMIC PUMA-2 and global temperature and precipitation datasets. To illustrate this approach, we calculate Signal-to-Noise-Ratios (SNRs) in terrestrial temperature and precipitation on simulations of an El Niño warm event, a phase change in Atlantic Meridional Oscillation (AMO) and a Heinrich cooling event. The results of the El Niño and AMO simulations indicate that the chance to accurately detect a climate signal increases with increasing SNRs. Considering the regions and seasons with highest SNRs, the simulated El Niño anomalies show good agreement with observations (r² = 0.8 and 0.6 for temperature and precipitation at SNRs > 4). The AMO signals rarely surpass the noise levels and remain mostly undetected. The simulation of a Heinrich event predicts highest SNRs for temperature (up to 10) over Arabia and Russia during Boreal winter and spring. Highest SNRs for precipitation (up to 12) are predicted over

  16. Connecting the records: exploiting tephra deposits to help understand abrupt climate change

    NASA Astrophysics Data System (ADS)

    Davies, S. M.; Abbott, P. M.; Bourne, A. J.; Chapman, M.; Pearce, N. J. G.; Griggs, A. J.; Cook, E.

    2016-12-01

    The causal mechanism of abrupt climate change during the last glacial period remains a key challenge. Although these events are well-documented in a wide range of proxy records, the triggers and drivers remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is limited by the challenges of synchronising palaeoclimate records on a common timescale. Here we present the potential and the challenges of optimising the use of cryptotephra deposits to precisely correlate the Greenland ice-cores with North Atlantic marine records. A series of new cryptotephra deposits have been identified in Greenland, increasing the scope of identifying coeval isochrons in the marine environment. This new framework, however, brings new challenges in the search for unique and robust geochemical fingerprints for unequivocal tephra correlations. As such, some tephra deposits are proposed to be more valuable than others and underpin key snapshots in time during the last glacial period. The North Atlantic Ash Zone II, for instance, represents the most widespread isochron and constrains the cooling of GI-15. Some tephra deposits in the ice-core record originate from ultra-distal sources beyond the North Atlantic region and we also explore the potential for establishing North Pacific linkages.

  17. From the Cover: Antarctic climate signature in the Greenland ice core record.

    PubMed

    Barker, Stephen; Knorr, Gregor

    2007-10-30

    A numerical algorithm is applied to the Greenland Ice Sheet Project 2 (GISP2) dust record from Greenland to remove the abrupt changes in dust flux associated with the Dansgaard-Oeschger (D-O) oscillations of the last glacial period. The procedure is based on the assumption that the rapid changes in dust are associated with large-scale changes in atmospheric transport and implies that D-O oscillations (in terms of their atmospheric imprint) are more symmetric in form than can be inferred from Greenland temperature records. After removal of the abrupt shifts the residual, dejumped dust record is found to match Antarctic climate variability with a temporal lag of several hundred years. It is argued that such variability may reflect changes in the source region of Greenland dust (thought to be the deserts of eastern Asia). Other records from this region and more globally also reveal Antarctic-style variability and suggest that this signal is globally pervasive. This provides the potential basis for suggesting a more important role for gradual changes in triggering more abrupt transitions in the climate system.

  18. a Marine Record of Holocene Climate Events in Tropical South America

    NASA Astrophysics Data System (ADS)

    Haug, G. H.; Günther, D.; Hughen, K. A.; Peterson, L. C.; Röhl, U.

    2002-12-01

    Metal concentration data (Ti, Fe) from the anoxic Cariaco Basin off the Venezuelan coast record with subdecadal to seasonal resolution variations in the hydrological cycle over tropical South America during the last 14 ka. Following a dry Younger Dryas, a period of increased precipitation and riverine discharge occurred during the Holocene `thermal maximum'. Since ~5.4 ka, a trend towards drier conditions is evident from the data, with high amplitude fluctuations and precipitation minima during the time interval 3.8 to 2.8 ka and during the `Little Ice Age'. O pronouced increase in precipitation coincides with the phase sometimes referred to as the `Medieval Warm Period'. These regional changes in precipitation are best explained by shifts in the mean latitude of the Atlantic Intertropical Convergence Zone (ITCZ), potentially driven by Pacific-based climate variability. The variations recorded in Cariaco Basin sediments coincide with events in societal evolution that have been suggested previously to be motivated by environmental change. Regionally, the Cariaco record supports the notion that the collapse of this civilization between 800 and 1000 AD coincided with an extended period of drier conditions, implying that the rapid growth of Mayan culture from 600 to 800 AD may have resulted in a population operating at the fringes of the environment's carrying capacity. The Cariaco Basin record also hints at tropical climate events similar in timing to high latitude changes in the North Atlantic often invoked as pivotal to societal developments in Europe.

  19. Little Ice Age Climate near Beijing, China, Inferred from Historical and Stalagmite Records

    NASA Astrophysics Data System (ADS)

    Qian, Weihong; Zhu, Yafen

    2002-01-01

    Four data sets yield information about Holocene climatic change in China at different scales of space and time: (a) 120-yr ground temperature and precipitation measurements covering eastern China; (b) two NOAA 10-yr 850 hPa wind records that highlight features of data set a; (c) an 1100-year record of annual calcite accumulation on a stalagmite near Beijing, and (d) Lamb-type average wetness and temperature data from Chinese historical records back to A.D. 1470 and 1450, respectively. Dry-wet fluctuations and cold-warm oscillations are inferred using the long-term stalagmite thickness series. Quasi-70, 140, 450, and 750-yr oscillations have been detected using a wavelet transform technique. A phase relationship between temperature and precipitation oscillations has been identified based on modern observations and historical records. In northern China, relatively lower temperatures correlate with periods when precipitation shifted from above to below normal. Three colder periods during the Little Ice Age (LIA) in China are inferred, centered in the late 14th century (750-yr oscillation), the early 17th century (450-yr), and the 19th century (140-yr). The latest cool period (1950s-1970s) is found at the 70-yr oscillation. Interdecadal drought-flood and cold-warm differences are explained using modern circulation patterns. LIA climate in China was likely controlled by East Asian monsoon circulation anomalies that were affected by variations in continent-ocean thermal contrast.

  20. Postglacial climate-change record in biomarker lipid compositions of the Hani peat sequence, Northeastern China

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Zheng, Yanhong; Meyers, Philip A.; Jull, A. J. Timothy; Xie, Shucheng

    2010-05-01

    The peat sequence at Hani in northeastern China accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system. The molecular compositions of n-alkanes, n-alkanols, and n-alkanoic acids extracted from the Hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat-forming vegetation. Long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n-alkane distributions throughout the Hani peat sequence. The paleoclimate integrity of these biomarker molecules appears to be well preserved. Most of the n-alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants. In contrast, n-alkanoic acid distributions are dominated by secondary components that record the importance of post-depositional microbial activity in this peat sequence, which evidently can be extensive in a percolation mire. Elevated n-alkane Paq values and C 23/C 29 ratios, which are both molecular proxies for water-loving plants, record an especially moist local climate in the Bølling-Allerød (14.5 to 12.9 ka), Younger Dryas (12.9 to 11.5 ka), and Pre-Boreal (11.5 to 10.5 ka) portions of the Hani peat sequence. Depressed Paq values and C 23/C 29 ratios and larger n-alkane average chain length values indicate that the Holocene Climatic Optimum (10.5 to 6 ka) was a period of warmer climate with lower effective precipitation, which contrasts with evidence of wetter climates in most of East Asia.

  1. Coral δ18O records Porites vs. Diploastrea - sampling resolution and climatic signal!

    NASA Astrophysics Data System (ADS)

    Dassie, E. P.; Linsley, B. K.; Lambdin, S.

    2013-12-01

    Narrowing uncertainties in climate prediction is an economical and social need that could partially be addressed by the development of robust paleoclimatic networks. Porites is the most widely used genus in studies using massive corals from the Pacific Ocean, however only a few Pacific Porites records span more than 100 years. A different slower growing coral genius, Diploastrea, has the potential to also generate multi-century length paleo-records. Recent Paleoclimatic studies utilizing this genus have shown promising results (Watanabe et al., 2003; Bagnato et al., 2004, 2005). However, some sampling concerns still remain. Diploastrea has large individual corallites (4-5 times larger than Porites); these corallites include a straight inner portion (columella) surrounded by a radiating portion (septa). The septa portion does not grow perpendicular to the direction of the coral growth, but instead radiates at a 45° angle from the columella. Sampling both the columnar and septal portions simultaneously might produce erroneous climatic reconstructions, reflecting a combination of corallite material precipitated several months apart. Additionally, due to Diploastrea slower growing rate, a millimeter sampling resolution might not be enough to retrieve robust climatic information. This study determined the optimal sampling resolution for Diploastrea from Fiji and verified the fidelity of this archive to reconstruct climatic variability. δ18O and δ13C measurements were made on one Diploastrea and one Porites coral colonies from a lagoon in Kandavu, Fiji. Diploastrea (FKD2) was sampled and analyzed at a 0.25mm resolution and Porites (FKD1) at a one-mm resolution; taking into consideration the growth rate of these two cores, both sampling resolution corresponds to a nearly monthly resolution. We created low-resolution sampling from the high-resolution sampling of the Diploastrea and compared it to the Porites measurements. This leads to determine the optimal sampling

  2. Sedimentary record of recent climate impacts on an insular coastal lagoon in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Cuellar-Martinez, Tomasa; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan-Albert; Alonso-Rodríguez, Rosalba

    2017-03-01

    Sedimentary records are useful to evaluate environmental changes, either from natural or anthropogenic causes, such as global and climate change. The recent changes in accumulation rates and geochemical characteristics (grain size distribution, elemental composition, organic carbon and carbonate concentrations) recorded in a sediment core from San Jose Island Lagoon (SJIL, Gulf of California) were evaluated to determine its relationship with anthropogenic impacts and climatic variability. The 210Pb-derived chronology was corroborated with 239+240Pu and 137Cs stratigraphic markers. The mass accumulation rate increased up to ∼3 times during the past ∼100 years (0.16 ± 0.03 to 0.51 ± 0.06 g cm-2 yr-1). The contents of terrigenous and marine (salinity) indicator elements, as well as fine-grained sediments, also increased considerably, although no anthropization evidences were observed; indeed, the enrichment factor of trace elements indicated that the ecosystem is still a pristine environment. By using multivariate statistical techniques, we inferred that the larger input of fine-grained terrigenous sediments could be related to the enhancement of soil erosion from the catchment, under the influence of higher rainfall rates, especially during the last 20 years. In addition, the higher concentrations of salinity indicator elements most likely resulted from higher evaporation rates in the lagoon, caused by higher minimum atmospheric temperatures. We concluded that recent climate variability has become the main driver for sedimentary geochemical changes in San Jose Island Lagoon. These observations confirmed the usefulness of 210Pb-dated geochemical sediment records to study the impacts of recent climate variability where long-term environmental data is scarce or non-existent.

  3. North Pacific climate recorded in growth rings of geoduck clams: A new tool for paleoenvironmental reconstruction

    NASA Astrophysics Data System (ADS)

    Strom, Are; Francis, Robert C.; Mantua, Nathan J.; Miles, Edward L.; Peterson, David L.

    2004-03-01

    To better understand North Pacific climate variability at interannual to interdecadal scales, we have developed a new tool for paleoenvironmental reconstruction. We show that growth rings in long-lived geoduck clams (Panopea abrupta) can provide high quality, annually resolved records of sea-surface temperature (SST). We used shell samples from the Strait of Juan de Fuca, in Washington State, to extend the coastal SST record back to 1877. The spatial correlation pattern between the growth index and gridded SSTs bears a strong resemblance to the leading pattern of interdecadal global SST variations and underscores the remarkable long-distance coherence evident among coastal SST records in the northeast Pacific. Our results also indicate that the 1990s was the warmest decade in this region since at least the 1850s.

  4. Holocene-Late pleistocene climatic ice core records for Qinghai-Tibetan plateau

    SciTech Connect

    Thompson, L.G.; Mosley-Thompson, E.; Davis, M.E.; Bolzan, J.F.; Dai, J.; Klien, L. ); Yao, T.; Wu, X.; Xie, Z. ); Gundestrup, N. )

    1989-10-27

    Three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau of China provide a detailed record of Holocene and Wisconsin-Wuerm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative {delta}{sup 18}O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly {approximately} 10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago.

  5. Wetlands as a Record of Climate Change and Hydrological Response in Arid Rift Settings

    NASA Astrophysics Data System (ADS)

    Ashley, G. M.

    2004-12-01

    Of all the terrestrial depositional settings, rift basins typically provide the greatest accommodation space, and consequently have some of the longest records of continental sedimentation. Lake deposits were the only rift component studied for records of long-term climatic change and for testing hypotheses of orbital forcing. Recently, the continuing quest for the paleontological and cultural records of human origins entombed in the sedimentary rocks of the East African Rift System raised questions concerning hydrologic and biologic response to climatic change. Additional issues are the impact of climate on paleolandscapes and the environmental stresses that might have affected human evolution. Other important indicators of rift hydrology, such as springs and wetlands are now emerging as viable records of climate change. Rift valley basins are shallow, hydrologically closed systems that are responsive to shifts in climate, and specifically sensitive to changes in the hydrologic budget (P-ET). Long term wet-dry cycles in the low latitudes are thought to be astronomically controlled, i.e. Milankovitch precession cycles (19-23 ka). In the tropics, precipitation (P) varies with changes in solar insolation which fluctuates <8-10 % over a cycle. Stronger insolation drives stronger summer monsoon maxima increasing P. Mean annual temperatures are high, but evapo-transpiration, ET (~ 2500 mm/yr) varies little. Consequently, during wetter periods regional groundwater reservoirs enlarge, the water table rises and springs and wetlands increase in number and in size compared to drier periods. Lake levels are known to fluctuate in response to change in hydrologic budget and wetlands appear to respond similarly. Springs and groundwater-fed wetlands are common, however the sources and sustainability of water or what geologic factors lead to the formation and longevity of wetlands is not well established. It appears that rainfall is trapped on topographic highs (rift fault blocks

  6. Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records

    NASA Astrophysics Data System (ADS)

    Flantua, S. G. A.; Hooghiemstra, H.; Vuille, M.; Behling, H.; Carson, J. F.; Gosling, W. D.; Hoyos, I.; Ledru, M. P.; Montoya, E.; Mayle, F.; Maldonado, A.; Rull, V.; Tonello, M. S.; Whitney, B. S.; González-Arango, C.

    2016-02-01

    An improved understanding of present-day climate variability and change relies on high-quality data sets from the past 2 millennia. Global efforts to model regional climate modes are in the process of being validated against, and integrated with, records of past vegetation change. For South America, however, the full potential of vegetation records for evaluating and improving climate models has hitherto not been sufficiently acknowledged due to an absence of information on the spatial and temporal coverage of study sites. This paper therefore serves as a guide to high-quality pollen records that capture environmental variability during the last 2 millennia. We identify 60 vegetation (pollen) records from across South America which satisfy geochronological requirements set out for climate modelling, and we discuss their sensitivity to the spatial signature of climate modes throughout the continent. Diverse patterns of vegetation response to climate change are observed, with more similar patterns of change in the lowlands and varying intensity and direction of responses in the highlands. Pollen records display local-scale responses to climate modes; thus, it is necessary to understand how vegetation-climate interactions might diverge under variable settings. We provide a qualitative translation from pollen metrics to climate variables. Additionally, pollen is an excellent indicator of human impact through time. We discuss evidence for human land use in pollen records and provide an overview considered useful for archaeological hypothesis testing and important in distinguishing natural from anthropogenically driven vegetation change. We stress the need for the palynological community to be more familiar with climate variability patterns to correctly attribute the potential causes of observed vegetation dynamics. This manuscript forms part of the wider LOng-Term multi-proxy climate REconstructions and Dynamics in South America - 2k initiative that provides the ideal

  7. Numerical Modeling of Climatic Change from the Terminus Record of Lewis Glacier, Mount Kenya.

    NASA Astrophysics Data System (ADS)

    Kruss, Phillip Donald

    Over the last 100 years, the glaciers and lakes of East Africa have undergone dramatic change in response to climatic forcing. However, the available conventional meterological series have not proven sufficient to explain these environmental events. The secular climatic change at Lewis Glacier, Mount Kenya (0(DEGREES)9'S, 37(DEGREES)19'E), is reconstructed from its terminus record documented since 1893. The short-time-step numerical model developed for this study consists of climate and ice dynamics segments. The climate segment directly computes the effect on the net balance of change in the four forcings: precipitation, albedo, cloudiness, and temperature. The flow segment calculates the dynamic glacier response to net balance variation. Climatic change occurs over a wide range of time scales. Each glacier responds in a unique fashion to this spectrum of climatic forcings. The response of the Lewis terminus extent to repeated sinusoidal fluctuation in the net balance is calculated. The net balance versus elevation profile is separately translated along the orthogonal balance and elevation axes. Net balance amplitudes of 0.1 to 0.5 m a('-1) of ice and 10 to 50 m elevation, respectively, and periods ranging from 20 to 1000 years are covered. Consideration of the Lewis response is perspective with similar results for Hintereisferner, Storglaciaren, and Berendon and South Cascade Glaciers identifies general characteristics of the time lag and amplitude of the terminus response. The magnitude and timing of the change in only one of the climatic forcings precipitation, albedo, cloudiness, or temperature necessary to produce the retreat of the Lewis terminus from its late 19th century maximum are computed. Equivalent changes for two scenarios of simultaneous variation, namely precipitation/albedo/cloudiness and temperature/albedo, are also estimated. These numerical results are interpreted in the light of long-term lake level, river flow, and instrumental information. A

  8. Using Coastal Ice Cap Records to Investigate Maritime Climate and Ice Sheet Processes in West Greenland

    NASA Astrophysics Data System (ADS)

    Das, S. B.; Evans, M. J.; Frey, K. E.; Osman, M. B.; Smith, B. E.; Stevens, L. A.; Trusel, L. D.; York, A.; Bingham, M.

    2014-12-01

    Recent changes, including outlet glacier retreat and speedup, and increased rates of surface melting, have dramatically increased the Greenland ice sheet contribution to sea-level rise over the past few decades. Increasingly studies point towards the influence of coupled ocean-ice processes in modulating Greenland ice sheet mass balance and glacier behavior in response to climate change, but many of these studies are limited to the past few years to decades, restricting our ability to understand these ocean-ice relationships over longer time periods. Ice core records have the potential to provide unique, high-resolution records of interest (e.g. accumulation and melt variability, as well as contemporaneous proxy records of regional air temperature and sea surface conditions), but suitable Greenland ice sheet coring regions are often located far inland (>200 km) from many maritime regions of interest. In this study we focus on new records from previously unstudied maritime ice caps (10-30 km from the coast) to reconstruct past environmental conditions in the Disko, Ummannaq and Baffin Bay regions. Here we present results from our recent 2014 field investigation of three high altitude ice caps (1300-2000 m) on Disko Island and the Nuussuaq Peninsula, as well as complementary results from two sites in the western ice sheet accumulation zone. Geophysical observations provide constraints on ice thickness, layering, and ice flow. Physical and chemical stratigraphic observations from snow pits and shallow firn cores are used to reconstruct recent accumulation rate and melt variability, as well as to develop and test environmental proxy relationships over the satellite era. Multi-century records from longer coastal ice cores, to be drilled in 2015, will contribute a key missing component to the existing observational record documenting ice, ocean and atmospheric changes in this region over a time period of dramatic change in Greenland ice sheet behavior (retreat and

  9. 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

  10. High resolution 900 yr volcanic and climatic record from the Vostok area, East Antarctica

    NASA Astrophysics Data System (ADS)

    Osipov, E. Yu.; Khodzher, T. V.; Golobokova, L. P.; Onischuk, N. A.; Lipenkov, V. Ya.; Ekaykin, A. A.; Osipova, O. P.

    2013-05-01

    Detailed volcanic record of the last 900 yr (1093-2010 AD) has been received using high resolution (2-3 samples per accumulation year) sulfate measurements in four snow/firn cores from the Vostok station area, East Antarctica. Totally, 33 volcanic events have been identified in the record, including well-known low latitude eruption signals found in many polar ice cores (e.g., Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Huanaputina 1600, Kuwae 1452), however in comparison with other Antarctic sites the record has more events covering the last 900 yr. The strongest volcanic signals occurred during mid-13th, mid-15th and 18th centuries. The largest volcanic signal of Vostok (both in sulfate concentration and flux) is the 1452 AD Kuwae eruption. Average snow accumulation rate calculated for the period 1093-2010 AD is 21.3 ± 2.3 mm H2O. Accumulation record demonstrates a slight positive trend, however sharply increased accumulation rate during the periods from 1600 to 1815 AD (by 11% from long-term mean) and from 1963 to 2010 AD (by 15%) are typical features of the site. Na+ record shows strong decadal-scale variability probably connected with coupled changes in atmospheric transport patterns over Antarctica (meridional circulation change) and local glaciology. The obtained high resolution climatic records suggest a high sensitivity of the Vostok location to environmental changes in Southern Hemisphere.

  11. Multidecadal climate variability in Brazil's Nordeste during the last 3000 years based on speleothem isotope records

    NASA Astrophysics Data System (ADS)

    Novello, Valdir F.; Cruz, Francisco W.; Karmann, Ivo; Burns, Stephen J.; Stríkis, Nicolás M.; Vuille, Mathias; Cheng, Hai; Lawrence Edwards, R.; Santos, Roberto V.; Frigo, Everton; Barreto, Eline A. S.

    2012-12-01

    We present the first high resolution, approximately ∼4 years sample spacing, precipitation record from northeastern Brazil (hereafter referred to as ‘Nordeste’) covering the last ∼3000 yrs from 230Th-dated stalagmites oxygen isotope records. Our record shows abrupt fluctuations in rainfall tied to variations in the intensity of the South American summer monsoon (SASM), including the periods corresponding to the Little Ice Age (LIA), the Medieval Climate Anomaly (MCA) and an event around 2800 yr B.P. Unlike other monsoon records in southern tropical South America, dry conditions prevailed during the LIA in the Nordeste. Our record suggests that the region is currently undergoing drought conditions that are unprecedented over the past 3 millennia, rivaled only by the LIA period. Using spectral, wavelet and cross-wavelet analyses we show that changes in SASM activity in the region are mainly associated with variations of the Atlantic Multidecadal Oscillation (AMO) and to a lesser degree caused by fluctuations in tropical Pacific SST. Our record also shows a distinct periodicity around 210 years, which has been linked to solar variability.

  12. Climate change research in Massachusetts, U.S.A.: searching for phenology in the historical record.

    NASA Astrophysics Data System (ADS)

    Primack, R.; Miller-Rushing, A.

    2009-04-01

    The United States does not have as many large, well-researched sets of phenological records as can be found in Europe. Such phenological research is important both scientifically to investigate the effects of climate change and, just as importantly, for convincing the public that climate change is really happening and is already affecting our environment. Scientists in the United States are currently uncovering a wealth of data from a variety of unconventional sources on the effects of climate on the phenology of a wide range of organisms, with many studies being published on birds and plants. For the past six years, we have been investigating the impact of climate change in Massachusetts, a region with a particularly strong tradition of science and natural history. We are able to use combinations of herbarium specimens, photographs, diaries of individual naturalists, records from research stations, and current observations of our own to document the effects of climate change. Each of these data sources has certain limitations, but the overall message is the same: a warming climate is causing plants to flower earlier and certain migratory birds to arrive earlier. Such data has to be interpreted carefully due to issues of changing population sizes and changing sampling methods and intensity. The single most valuable source of data for our research has been the observations of flowering times of hundreds of plant species from 1852 to 1858 in Concord, Massachusetts, made by Henry David Thoreau. Thoreau is the most famous environmental philosopher in the United States, and most students read his book Walden. Later botanists also recorded flowering times and the abundance of plant species in Concord, and we recorded flowering times and species abundances in Concord starting in 2004. The project has shown that spring flowering species are the most responsive to temperatures, and that these plant species are now flowering seven days earlier than they were in the 1850s

  13. 500-year climate cycles stacking of recent centennial warming documented in an East Asian pollen record

    NASA Astrophysics Data System (ADS)

    Xu, Deke; Lu, Houyuan; Chu, Guoqiang; Wu, Naiqin; Shen, Caiming; Wang, Can; Mao, Limi

    2014-01-01

    Here we presented a high-resolution 5350-year pollen record from a maar annually laminated lake in East Asia (EA). Pollen record reflected the dynamics of vertical vegetation zones and temperature change. Spectral analysis on pollen percentages/concentrations of Pinus and Quercus, and a temperature proxy, revealed ~500-year quasi-periodic cold-warm fluctuations during the past 5350 years. This ~500-year cyclic climate change occurred in EA during the mid-late Holocene and even the last 150 years dominated by anthropogenic forcing. It was almost in phase with a ~500-year periodic change in solar activity and Greenland temperature change, suggesting that ~500-year small variations in solar output played a prominent role in the mid-late Holocene climate dynamics in EA, linked to high latitude climate system. Its last warm phase might terminate in the next several decades to enter another ~250-year cool phase, and thus this future centennial cyclic temperature minimum could partially slow down man-made global warming.

  14. Climate response to the Samalas volcanic eruption in 1257 revealed by proxy records

    NASA Astrophysics Data System (ADS)

    Guillet, Sébastien; Corona, Christophe; Stoffel, Markus; Khodri, Myriam; Lavigne, Franck; Ortega, Pablo; Eckert, Nicolas; Sielenou, Pascal Dkengne; Daux, Valérie; Churakova (Sidorova), Olga V.; Davi, Nicole; Edouard, Jean-Louis; Zhang, Yong; Luckman, Brian H.; Myglan, Vladimir S.; Guiot, Joël; Beniston, Martin; Masson-Delmotte, Valérie; Oppenheimer, Clive

    2017-01-01

    The eruption of Samalas in Indonesia in 1257 ranks among the largest sulfur-rich eruptions of the Common Era with sulfur deposition in ice cores reaching twice the volume of the Tambora eruption in 1815. Sedimentological analyses of deposits confirm the exceptional size of the event, which had both an eruption magnitude and a volcanic explosivity index of 7. During the Samalas eruption, more than 40 km3 of dense magma was expelled and the eruption column is estimated to have reached altitudes of 43 km. However, the climatic response to the Samalas event is debated since climate model simulations generally predict a stronger and more prolonged surface air cooling of Northern Hemisphere summers than inferred from tree-ring-based temperature reconstructions. Here, we draw on historical archives, ice-core data and tree-ring records to reconstruct the spatial and temporal climate response to the Samalas eruption. We find that 1258 and 1259 experienced some of the coldest Northern Hemisphere summers of the past millennium. However, cooling across the Northern Hemisphere was spatially heterogeneous. Western Europe, Siberia and Japan experienced strong cooling, coinciding with warmer-than-average conditions over Alaska and northern Canada. We suggest that in North America, volcanic radiative forcing was modulated by a positive phase of the El Niño-Southern Oscillation. Contemporary records attest to severe famines in England and Japan, but these began prior to the eruption. We conclude that the Samalas eruption aggravated existing crises, but did not trigger the famines.

  15. Plant Functional Variability in Response to Late-Quaternary Climate Change Recorded in Ancient Packrat Middens

    NASA Astrophysics Data System (ADS)

    Holmgren, C. A.; Potts, D. L.

    2006-12-01

    Responses of plant functional traits to environmental variability are of enduring interest because they constrain organism performance and ecosystem function. However, most inferences regarding plant functional trait response to climatic variability have been limited to the modern period. To better understand plant functional response to long-term climate variability and how adjustments in leaf morphology may contribute to patterns of species establishment, persistence, or extirpation, we measured specific leaf area (SLA) from macrofossils preserved in ancient packrat middens collected along the Arizona/New Mexico border, USA. Our record spanned more than 32,000 years and included six woodland and Chihuahuan Desert species: Berberis cf. haematocarpa, Juniperus cf. coahuilensis, Juniperus osteosperma, Larrea tridentata, Prosopis glandulosa and Parthenium incanum. We predicted that regional climatic warming and drying since the late Pleistocene would result in intraspecific decreases in SLA. As predicted, SLA was positively correlated with midden age for three of the six species (L. tridentata, J. osteosperma, B. cf. haematocarpa). SLA was also negatively correlated with December (L. tridentata, J. cf. coahuilensis) or June (B. cf. haematocarpa, J. osteosperma) insolation. A unique record of vegetation community dynamics, plant macrofossils preserved in packrat middens also represent a rich and largely untapped source of information on long-term trends in species functional response to environmental change.

  16. 500-year climate cycles stacking of recent centennial warming documented in an East Asian pollen record

    PubMed Central

    Xu, Deke; Lu, Houyuan; Chu, Guoqiang; Wu, Naiqin; Shen, Caiming; Wang, Can; Mao, Limi

    2014-01-01

    Here we presented a high-resolution 5350-year pollen record from a maar annually laminated lake in East Asia (EA). Pollen record reflected the dynamics of vertical vegetation zones and temperature change. Spectral analysis on pollen percentages/concentrations of Pinus and Quercus, and a temperature proxy, revealed ~500-year quasi-periodic cold-warm fluctuations during the past 5350 years. This ~500-year cyclic climate change occurred in EA during the mid-late Holocene and even the last 150 years dominated by anthropogenic forcing. It was almost in phase with a ~500-year periodic change in solar activity and Greenland temperature change, suggesting that ~500-year small variations in solar output played a prominent role in the mid-late Holocene climate dynamics in EA, linked to high latitude climate system. Its last warm phase might terminate in the next several decades to enter another ~250-year cool phase, and thus this future centennial cyclic temperature minimum could partially slow down man-made global warming. PMID:24402348

  17. Relationship between Quaternary climate change and Podocarpaceae record: marine pollen record in west pacific area since the last interglacial period

    NASA Astrophysics Data System (ADS)

    Bian, Y.

    2016-12-01

    Tropical vegetation is the most outstanding and obvious feature of South-East Asia. The Podocarpaceae is the most successful gymnosperm family in angiosperm-dominated tropical forests. Tropical podocarps are most abundant in mid to high-elevation forests, suggesting that the habitat requirements of temperate ancestors have been retained as podocarps radiated into the tropics. Then, podocarp pollen was relatively common in lake sediments during the last glacial period but decreased to trace amounts during the Holocene, presumably as a result of climate warming. But, from some marine core in the west pacific area, the genera variation of tropical mid-upper montane pollen record is also distinct during the glacial cycle. A high representation of pollen from tropical upper montane rainforest (mainly Podocarpus) during the last glacial period indicates that this forest type extended to lower attitudes. And the genera variations of the tropical mid-upper montane rainforest exist between the Phyllocladus and Podocarpus with the environment and climate changing. The pollen content of Phyllocladus is much high in marine isotope stage (MIS) 5, but Podocarpus is much higher in the glacial period. During the onset of MIS 5a and 5c, the percentage of Phyllocladus pollen declines dramatically. In Asia, podocarp taxa have apparently dispersed through both lowland and montane habitats. Dacrydium and Podocarpus also occur occasionally in lowland tropical rainforest. On the other hand, Dacrycarpus and Phyllocladus appear to have jumped between islands of montane/alpine habitat. For example, vegetation investigation in Mindanao, shows that Podocarpus exists in altitude ranging from 1,200-1,700 m, and Phyllocladus appear in altitude range from 1700-2100 m, but is more abundant above the 2,400 m. Thus, Phyllocladus might be more sensitive to the temperature change. Then, the pollen content of Phyllocladus is much high during the interglacial period, especially MIS 5, might be caused by

  18. Top of Atmosphere Radiation MVIRI/SEVIRI Data Record within the Climate Monitoring SAF

    NASA Astrophysics Data System (ADS)

    Urbain, Manon; Clerbaux, Nicolas; Ipe, Alessandro; Tornow, Florian; Hollmann, Rainer; Baudrez, Edward; Velazquez Blazquez, Almudena; Moreels, Johan; Trentmann, Jörg

    2017-04-01

    The CM SAF Top of Atmosphere (TOA) Radiation MVIRI/SEVIRI Data Record provides a homogeneous satellite-based climatology of the TOA Reflected Solar (TRS) and Emitted Thermal (TET) radiation in all-sky conditions. The continuous monitoring of these two components of the Earth Radiation Budget is of prime importance to study climate variability and change. The Meteosat Visible and InfraRed Imager (MVIRI - from 1983 until 2004) and the Spinning Enhanced Visible and Infrared Imager (SEVIRI - from 2004 onward) on board the Meteosat First and Second Generation satellites are combined to generate a long Thematic Climate Data Record (TCDR). Combining MVIRI and SEVIRI allows an unprecedented temporal (30 minutes / 15 minutes) and spatial (2.5 km / 3 km) resolution compared to the Clouds and the Earth's Radiant Energy System (CERES) products. This is a step forward as it helps to increase the knowledge of the diurnal cycle and the small-scale spatial variations of radiation. The MVIRI/SEVIRI Data Record covers a 32 years time period from 1 February 1983 to 30 April 2015. The TOA radiation products are provided as daily mean, monthly mean and monthly averages of the hourly integrated values (diurnal cycle). To ensure consistency with other CM SAF products, the data is provided on a regular grid at a spatial resolution of 0.05 degrees (i.e. about 5.5 km) and covers the region between +/- 70° longitude and +/- 70° latitude. Validation of the MVIRI/SEVIRI Data Record has been performed by intercomparison with several references such as the CERES products (EBAF, SYN1deg-Day and SYN1deg-M3Hour), the HIRS OLR Climate Data Record (Daily and Monthly), the reconstructed ERBS WFOV-CERES (or DEEP-C) dataset and the ISCCP FD products. CERES is considered as the best reference from March 2000 onward. The quality of the early part of the Data Record is verified against the other references. In general, the stability of all the TOA radiation products is estimated to be better than 4 W.m-2

  19. Coralline alga reveals first marine record of subarctic North Pacific climate change

    NASA Astrophysics Data System (ADS)

    Halfar, Jochen; Steneck, Robert; Schöne, Bernd; Moore, G. W. K.; Joachimski, Michael; Kronz, Andreas; Fietzke, Jan; Estes, James

    2007-04-01

    While recent changes in subarctic North Pacific climate had dramatic effects on ecosystems and fishery yields, past climate dynamics and teleconnection patterns are poorly understood due to the absence of century-long high-resolution marine records. We present the first 117-year long annually resolved marine climate history from the western Bering Sea/Aleutian Island region using information contained in the calcitic skeleton of the long-lived crustose coralline red alga Clathromorphum nereostratum, a previously unused climate archive. The skeletal δ 18O-time series indicates significant warming and/or freshening of surface waters after the middle of the 20th century. Furthermore, the time series is spatiotemporally correlated with Pacific Decadal Oscillation (PDO) and tropical El Niño-Southern Oscillation (ENSO) indices. Even though the western Bering Sea/Aleutian Island region is believed to be outside the area of significant marine response to ENSO, we propose that an ENSO signal is transmitted via the Alaskan Stream from the Eastern North Pacific, a region of known ENSO teleconnections.

  20. Solar and climate signal records in tree ring width from Chile (AD 1587 1994)

    NASA Astrophysics Data System (ADS)

    Rodolfo Rigozo, Nivaor; Roger Nordemann, Daniel Jean; Evangelista da Silva, Heitor; Pereira de Souza Echer, Mariza; Echer, Ezequiel

    2007-01-01

    Tree growth rings represent an important natural record of past climate variations and solar activity effects registered on them. We performed in this study a wavelet analysis of tree ring samples of Pilgerodendron cupressoides species, from Glaciar Pio XI (Lat: 49°12'S; 74°55'W; Alt: 25 m), Chile. We obtained an average chronology of about 400 years from these trees. The 11-yr solar cycle was present during the whole period in tree ring data, being more intense during Maunder minimum (1645-1715). The short-term periods, around 2-7 yr, that were found are more likely associated with ENSO effects. Further, we found significant periods around 52 and 80-100 yr. These periodicities are coincident with the fourth harmonic (52 yr) of the Suess cycle (208 yr) and Gleissberg (˜80-100 yr) solar cycles. Therefore, the present analysis shows evidence of solar activity effect/modulation on climatic conditions that affect tree ring growth. Although we cannot say with the present analysis if this effect is on local, regional or global climate, these results add evidence to an important role of solar activity over terrestrial climate over the past ˜400 yr.

  1. Coralline alga reveals first marine record of subarctic North Pacific climate change

    USGS Publications Warehouse

    Halfar, J.; Steneck, R.; Schone, B.; Moore, G.W.K.; Joachimski, M.; Kronz, A.; Fietzke, J.; Estes, James

    2007-01-01

    While recent changes in subarctic North Pacific climate had dramatic effects on ecosystems and fishery yields, past climate dynamics and teleconnection patterns are poorly understood due to the absence of century-long high-resolution marine records. We present the first 117-year long annually resolved marine climate history from the western Bering Sea/Aleutian Island region using information contained in the calcitic skeleton of the long-lived crustose coralline red alga Clathromorphum nereostratum, a previously unused climate archive. The skeletal ??18O-time series indicates significant warming and/or freshening of surface waters after the middle of the 20th century. Furthermore, the time series is spatiotemporally correlated with Pacific Decadal Oscillation (PDO) and tropical El Nio??-Southern Oscillation (ENSO) indices. Even though the western Bering Sea/Aleutian Island region is believed to be outside the area of significant marine response to ENSO, we propose that an ENSO signal is transmitted via the Alaskan Stream from the Eastern North Pacific, a region of known ENSO teleconnections. Copyright 2007 by the American Geophysical Union.

  2. Sensitivity of Mid Holocene Global Climate to Changes in Vegetation Reconstructed From the Geologic Record

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.; Sloan, L. C.

    2001-12-01

    The influence of land surface changes upon global and regional climate has been shown both for anthropogenic and non-anthropogenic changes in land surface distribution. Because validation of global climate models (GCMs) is dependent upon the use of accurate boundary conditions, and because changes in land surface distribution have been shown to have effects on climate in areas remote from those changes, we have tested the sensitivity of a GCM to a global Mid Holocene vegetation distribution reconstructed from the fossil record, a first for a 6 ka GCM run. Large areas of the globe exhibit statistically significant seasonal warming of 2 to 4 ° C, with peak warming of 10 ° C over the Middle East in June-July-August (JJA). The patterns of maximum warming over both Northern Asia and the Middle East strongly coincide with the patterns of maximum decrease in albedo in all seasons. Likewise, cooling of up to 4 ° C over Northern Africa associated with the expansion of savanna and broadleaf evergreen forest also coincides with increases in surface heat flux of up to 35 W/m2 in March-April-May (MAM) and 60 W/m2 in JJA. At both the regional and global scale, the magnitude of vegetation forcing is equal to that of 6 ka orbital forcing, emphasizing the importance of accurate land surface distribution for both model validation and future climate prediction.

  3. Climate refugia: joint inference from fossil records, species distribution models and phylogeography.

    PubMed

    Gavin, Daniel G; Fitzpatrick, Matthew C; Gugger, Paul F; Heath, Katy D; Rodríguez-Sánchez, Francisco; Dobrowski, Solomon Z; Hampe, Arndt; Hu, Feng Sheng; Ashcroft, Michael B; Bartlein, Patrick J; Blois, Jessica L; Carstens, Bryan C; Davis, Edward B; de Lafontaine, Guillaume; Edwards, Mary E; Fernandez, Matias; Henne, Paul D; Herring, Erin M; Holden, Zachary A; Kong, Woo-seok; Liu, Jianquan; Magri, Donatella; Matzke, Nicholas J; McGlone, Matt S; Saltré, Frédérik; Stigall, Alycia L; Tsai, Yi-Hsin Erica; Williams, John W

    2014-10-01

    Climate refugia, locations where taxa survive periods of regionally adverse climate, are thought to be critical for maintaining biodiversity through the glacial-interglacial climate changes of the Quaternary. A critical research need is to better integrate and reconcile the three major lines of evidence used to infer the existence of past refugia - fossil records, species distribution models and phylogeographic surveys - in order to characterize the complex spatiotemporal trajectories of species and populations in and out of refugia. Here we review the complementary strengths, limitations and new advances for these three approaches. We provide case studies to illustrate their combined application, and point the way towards new opportunities for synthesizing these disparate lines of evidence. Case studies with European beech, Qinghai spruce and Douglas-fir illustrate how the combination of these three approaches successfully resolves complex species histories not attainable from any one approach. Promising new statistical techniques can capitalize on the strengths of each method and provide a robust quantitative reconstruction of species history. Studying past refugia can help identify contemporary refugia and clarify their conservation significance, in particular by elucidating the fine-scale processes and the particular geographic locations that buffer species against rapidly changing climate.

  4. Stable Isotopic Variations in Columnar Cacti: are Responses to Climate Recorded in Spines?

    NASA Astrophysics Data System (ADS)

    English, N. B.; Dettman, D. L.; Williams, D. G.

    2004-12-01

    The behavior of the North American monsoon (NAM), particularly with respect to times of continental drought and its relationship to the Pacific-North American (PNA) teleconnection pattern and the El Nino/Southern Oscillation (ENSO) is of great interest to paleoclimatologists and water managers. Long-term instrumental precipitation and tree ring records in the southwestern United States and northwestern Mexico at low elevations are sparse and this has hindered research on NAM variability at interannual timescales. Saguaro cacti (Carnegiea gigantea) and other columnar cacti in North and South America are long-lived and have the potential to record climate variability on land with high temporal and spatial resolution. The vertical sequence of spines on the saguaro's exterior represents a high resolution (4 to 6 per year), and long (over 150 years) record of environmental change. We present results from an experiment where we tracked the oxygen isotopic values in the source waters, stem tissue waters and spine tissue for three treatments over the course of three months. These data are then compared to a previously developed mechanistic model of isotopic variation that reflects the physiological responses of Saguaro to climate variation over seasonal to century long time-scales. We also present the rationale for a new method to determine the growth rate of columnar cacti using the radiocarbon bomb spike. Our measurements reveal that oxygen and hydrogen isotopic variation among the sequentially produced and persistent spines covering the saguaro body record fluctuations in saguaro water balance. The model successfully predicts isotopic variation in spines and constrains controlling variables, yielding a powerful and high-resolution stable isotope index of water stress in the low desert. The development and refinement of an isotopic model for saguaro will serve as the basis for models applied to other species of columnar cacti in North and South America. The role of the

  5. An age-calibrated record of upper Campanian - Maastrichtian climate change in the Boreal Realm

    NASA Astrophysics Data System (ADS)

    Thibault, N.; Schovsbo, N.; Harlou, R.; Stemmerik, L.; Surlyk, F.

    2011-12-01

    The latest Cretaceous climate of the Boreal Realm was recorded through high-resolution bulk carbon- and oxygen-stable isotopes and a nannofossil temperature index (NTI) on the Stevns-1 core (Denmark) which recovered 456 m of upper Campanian to basal Danian chalk with ~100% recovery and an excellent continuity. Carbon isotope stratigraphy and nannofossil biostratigraphy were used to correlate Stevns-1 to two sites that bear an excellent magnetostratigraphic record: DSDP Site 525A and ODP Site 762C. The correlation of δ13C trends between the three sites and the use of the recent astronomical calibration of upper Campanian - Maastrichtian magnetochrons (Husson et al., 2011; K-Pg boundary at 66 Ma) led to the establishment of a precise age-model for Stevns-1. The good correlation between bulk δ18O and the NTI (R=-0.81) allows the use of oxygen stable isotopes to estimate past variations of sea surface temperatures (SSTs) in the Boreal Realm. Three warming events punctuate the overall cooling trend of the latest Cretaceous: (1) the late Campanian climatic optimum (73.9-71.6 Ma) is characterized by maximum SSTs of 20°C, (2) the mid-Maastrichtian warming (69.7-68 Ma) is characterized by stable SSTs around 17°C and (3) the end-Maastrichtian warming (66.37-66.03) is characterized by increasing SSTs up to 18°C. The two cooling events of the early (71.6-69.7 Ma) and late Maastrichtian (68-66.37 Ma) are both characterized by stable SSTs around 16°C. This Boreal record of SSTs derived from the δ18O of bulk nannofossil chalk is in agreement with planktic biotic events of the latest Cretaceous and matches well with climatic trends of intermediate- and deep-waters from other oceanic basins recorded through benthic foraminiferal δ18O (Barrera and Savin, 1999). However, most planktic foraminiferal δ18O data do not record well the mid- and end-Maastrichtian warmings. This suggests that the influence of changes in seawater pH and depth habitats of Campanian

  6. A Coral-based Climate Record from the Western Pacific Warm Pool

    NASA Astrophysics Data System (ADS)

    Quinn, T. M.; Taylor, F. W.; Crowley, T. J.; Stephans, C.

    2002-12-01

    The Western Pacific Warm Pool (WPWP) serves as a heat engine for Earth's climate and as a major moisture source for its hydrological cycle. Thermal and hydrologic variations in the WPWP are intimately involved with ENSO variations on the interannual timescale, but the role of these variations on decadal to century timescales remains poorly understood because of the paucity of subannually resolved climate and paleoclimate time series from the WPWP. Coral-based proxy records of thermal and hydrologic variations in the WPWP offer a great opportunity to extend the instrumental record and address the modes and mechanisms of tropical climate variability on decadal to century timescales. Coral-based climate records have been exploited in other regions of the tropical oceans, yet such records are rare from the WPWP. Herein we report the initial results of a stable isotopic and elemental ratio study of a ~1.8 m Porites coral head recovered in ~ 8 m of water from offshore of Rabaul, East New Britain, Papua New Guinea (4°S, 152°E) in September, 1998. Rabaul is a site of active volcanism and has had major eruptive episodes in 1998, 1994, 1943-1937, 1878, 1791 and 1767. Rabaul is located within the 29°C contour of mean annual SST field of the WPWP and seawaters surrounding it experience <1°C seasonal range in SST. In contrast, there is a 1 psu seasonal range in SSS. Average annual rainfall exceeds 2 m per year. X-radiography reveals readily discernable growth bands and we estimate an average extension rate of 10 mm/yr. The coral slab was sampled every 0.625 mm yielding an average sample resolution of 16 samples per year. Coral powder was divided into two samples: one for oxygen and carbon isotopic determinations and one for Sr/Ca ratio determinations. Our initial stable isotope results indicate the existence of a robust annual cycle in addition to large isotopic excursions in 1994, likely the result of the large volcanic event of that year. Stable isotope data acquisition

  7. Floodplain ecohydrology: Discerning climatic v. anthropogenic controls from tree-ring δ18O, dendrochronology, and instrumental climate records

    NASA Astrophysics Data System (ADS)

    Singer, M. B.; Piégay, H.; Stella, J. C.; Wilson, R.

    2012-12-01

    Vegetation of lowland riparian zones in temperate climates is largely determined by floodplain water availability during the growth season. Floodplain water reservoirs are replenished seasonally by lateral hyporheic water from streamflow, which primarily contributes to phreatic zone water and by infiltration of precipitation, which typically controls seasonal vadose zone soil moisture. Water availability to species rooted to particular depths in the floodplain is subject to interannual variability in climate (e.g., precipitation magnitude, timing, and phase). Co-occurring tree species in the riparian zone may express differential adaptation to water availability and shifting water sources, especially if they are rooted at contrasting depths. We have developed an ecohydrologic approach to assess how climatic variability impacts water availability at different depths in the floodplain and corresponding tree growth in the Rhône River basin, France. We combine dendrochronology, tree ring isotopes (δ18O), and instrumental climate records to discern relationships between tree growth and water sources for two contrasting, co-occurring riparian species—the shallowly rooting Fraxinus excelsior and the obligate phreatophyte, Populus nigra (poplar). We developed growth time series via basal area increment (BAI) and extracted alpha-cellulose from tree rings to assess relative responses to water stress via δ18O contained in each annual ring, and we analyzed these data alongside streamflow, precipitation, and groundwater data. Our initial work on a tributary of the Rhône showed that F. excelsior generally indicates water availability in the vadose zone, while P. nigra provides a window into the phreatic zone. However, the rooting depths and water sources for these species overlap on particularly low topographic surfaces, where phreatic water is abundant for both. In contrast to prior assumptions, we found that P. nigra exhibits more growth sensitivity to drought stress

  8. Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and LiDAR data - case study from Drangajökull ice cap, NW-Iceland

    NASA Astrophysics Data System (ADS)

    Magnússon, E.; Belart, J. M. C.; Pálsson, F.; Ágústsson, H.; Crochet, P.

    2015-09-01

    In this paper we describe how recent high resolution Digital Elevation Models (DEMs) can be used as constraints for extracting glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW-Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne LiDAR in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high resolution LiDAR DEM (2 m × 2 m cell size and vertical accuracy < 0.5 m). The LiDAR DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice and snow free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical variogram model, which along with the derived errors in ice and snow free areas were used as inputs into 1000 Sequential Gaussian Simulations (SGSim). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM. The derived bias correction, varying in magnitude between DEMs from 0.03 to 1.66 m (1946 DEM) was then applied. The simulation results were also used to calculate the 95 % confidence level of this bias, resulting in values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2-4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional bias correction was therefore estimated using a degree day model to obtain the volume change between the start of two hydrological years (1 October). This correction corresponds to an average elevation change of ~ -3 m in the worst case for 1960, or about ~ 2/3 of volume change between the 1960 and the 1975 DEMs. The

  9. Tree ring records capture long-term memory in climate systems

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-03-01

    Measuring tree rings is a mainstay technique for estimating ancient climatic conditions, with a tree's year-by-year growth reflecting changes in precipitation and temperature. In some cases, paleoclimatological records compiled from tree ring measurements can stretch for thousands of years. Based on recent research, climatologists have found that hydrological and other systems have long-term memory. Drawing on tree ring measurements compiled from across the continental United States, Bowers et al. sought to determine whether such long-term relationships are preserved in ring width measurements. The authors analyzed the Hurst parameter—a measure of long-term memory—of 697 different tree ring records that were collected from 10 tree species from locations across the United States. They found that though each tree species had a different mean value for its Hurst parameter, meaning that each species recorded long-term trends in the climate differently, they all fell within the range suggestive of their being able to properly represent long-term memory.

  10. Synchrotron X-ray microscopy of marine calcifiers: how plankton record past climate change

    NASA Astrophysics Data System (ADS)

    Redfern, S. A. T.; Branson, O.; Read, E.

    2017-06-01

    We have used STXM and PEEM to reveal the underpinning chemistry and nanoscale structure behind palaeo-climate geochemical signatures, such as trace Mg in shells- proposed proxies for palaeo-ocean temperature. This has allowed us to test the chemical assumptions and mechanisms underpinning the use of such empirical proxies. We have determined the control on driving chemical variations in biogenic carbonates using STXM at the absorption edge of Mg, B, and Na in the shells of modern plankton. The power of these observations lies in their ability to link changes in chemistry, microstructure, and growth process in biogenic carbonate to environmental influences. We have seen that such changes occur at length scales of tens of nanometres and demonstrated that STXM provides an invaluable route to understanding chemical environment and key heterogeneity at the appropriate length scale. This new understanding provides new routes for future measurements of past climate variation in the sea floor fossil record.

  11. Gridded sunshine duration climate data record for Germany based on combined satellite and in situ observations

    NASA Astrophysics Data System (ADS)

    Walawender, Jakub; Kothe, Steffen; Trentmann, Jörg; Pfeifroth, Uwe; Cremer, Roswitha

    2017-04-01

    The purpose of this study is to create a 1 km2 gridded daily sunshine duration data record for Germany covering the period from 1983 to 2015 (33 years) based on satellite estimates of direct normalised surface solar radiation and in situ sunshine duration observations using a geostatistical approach. The CM SAF SARAH direct normalized irradiance (DNI) satellite climate data record and in situ observations of sunshine duration from 121 weather stations operated by DWD are used as input datasets. The selected period of 33 years is associated with the availability of satellite data. The number of ground stations is limited to 121 as there are only time series with less than 10% of missing observations over the selected period included to keep the long-term consistency of the output sunshine duration data record. In the first step, DNI data record is used to derive sunshine hours by applying WMO threshold of 120 W/m2 (SDU = DNI ≥ 120 W/m2) and weighting of sunny slots to correct the sunshine length between two instantaneous image data due to cloud movement. In the second step, linear regression between SDU and in situ sunshine duration is calculated to adjust the satellite product to the ground observations and the output regression coefficients are applied to create a regression grid. In the last step regression residuals are interpolated with ordinary kriging and added to the regression grid. A comprehensive accuracy assessment of the gridded sunshine duration data record is performed by calculating prediction errors (cross-validation routine). "R" is used for data processing. A short analysis of the spatial distribution and temporal variability of sunshine duration over Germany based on the created dataset will be presented. The gridded sunshine duration data are useful for applications in various climate-related studies, agriculture and solar energy potential calculations.

  12. An ikaite record of late Holocene climate at the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Lu, Z.; Rickaby, R. E.; Kennedy, H.; Pancost, R. D.; Shaw, S.; Lennie, A. R.; Wellner, J. S.; Anderson, J. B.

    2011-12-01

    Ikaite is a low temperature polymorph of calcium carbonate which is hydrated with water molecules contained in its crystal lattice (CaCO3:6H2O). Ikaite is thought to rapidly decompose into calcite and water at temperatures above 4°C. The hydration water in ikaite grown in laboratory experiments records the δ18O of ambient water, a feature potentially useful for reconstructing δ18O of local seawater. The most recent melting of the Caley Glacier on the Antarctic Peninsula (AP) during last few decades released meltwater into nearby fjords and left a strong signal of light δ18O values in shallow porewater profiles. If ikaite crystals incorporate ambient porewaters into crystal structure as the hydration water, then crystals grown at different times will record the changes in bottom water δ18O due to waxing and waning of (global or local) ice-sheets. U.S. Antarctic Program cruise NBP0703 collected piston cores around the AP and found ikaite crystals in multiple horizons at the Firth of Tay, suitable for reconstructing a low resolution ikaite record of the last 2000 years. We report the first downcore δ18O record of natural ikaite hydration waters and crystals collected from the AP, a region sensitive to climate fluctuations. We are able to establish the zone of ikaite formation within shallow sediments and derive a climatic signal, related to local changes in fjord δ18O, versus time encoded in this late Holocene ikaite record. Our interpretation, based on ikaite isotopes, provides additional qualitative evidence that both the Medieval Warm Period and Little Ice Age were extended to the Southern Ocean and the Antarctic Peninsula.

  13. Maturity Matrices for Quality of Model- and Observation-Based Climate Data Records

    NASA Astrophysics Data System (ADS)

    Höck, Heinke; Kaiser-Weiss, Andrea; Kaspar, Frank; Stockhause, Martina; Toussaint, Frank; Lautenschlager, Michael

    2015-04-01

    In the field of Software Engineering the Capability Maturity Model is used to evaluate and improve software development processes. The application of a Maturity Matrix is a method to assess the degree of software maturity. This method was adapted to the maturity of Earth System data in scientific archives. The application of such an approach to Climate Data Records was first proposed in the context of satellite-based climate products and applied by NOAA and NASA. The European FP7 project CORE-CLIMAX suggested and tested extensions of the approach in order to allow the applicability to additional climate datasets, e.g. based on in-situ observations as well as model-based reanalysis. Within that project the concept was applied to products of satellite- and in-situ based datasets. Examples are national ground-based data from Germany as an example for typical products of a national meteorological service, the EUMETSAT Satellite Application Facility Network, the ESA Climate Change Initiative, European Reanalysis activities (ERA-CLIM) and international in situ-based climatologies such as GPCC, ECA&D, BSRN, HadSST. Climate models and their related output have some additional characteristics that need specific consideration in such an approach. Here we use examples from the World Data Centre for Climate (WDCC) to discuss the applicability. The WDCC focuses on climate data products, specifically those resulting from climate simulations. Based on these already existing Maturity Matrix models, WDCC developed a generic Quality Assessment System for Earth System data. A self-assessment is performed using a maturity matrix evaluating the data quality for five maturity levels with respect to the criteria data and metadata consistency, completeness, accessibility and accuracy. The classical goals of a quality assessment system in a data processing workflow are: (1) to encourage data creators to improve quality to reach the next quality level, (2) enable data consumers to decide

  14. Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

    PubMed

    Zhang, Wenxiang; Ming, Qingzhong; Shi, Zhengtao; Chen, Guangjie; Niu, Jie; Lei, Guoliang; Chang, Fengqin; Zhang, Hucai

    2014-01-01

    Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

  15. Lake Sediment Records on Climate Change and Human Activities in the Xingyun Lake Catchment, SW China

    PubMed Central

    Zhang, Wenxiang; Ming, Qingzhong; Shi, Zhengtao; Chen, Guangjie; Niu, Jie; Lei, Guoliang; Chang, Fengqin; Zhang, Hucai

    2014-01-01

    Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun′s catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60–1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun’s catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years. PMID:25033404

  16. A 2000 year varve-based climate record from the central Brooks Range, Alaska

    SciTech Connect

    Bird, BW; Abbott, MB; Finney, BP; Kutchko, B

    2009-01-01

    Varved minerogenic sediments from glacial-fed Blue Lake, northern Alaska, are used to investigate late Holocene climate variability. Varve-thickness measurements track summer temperature recorded at Atigun Pass, located 41 km east at a similar elevation (r (2) = 0.31, P = 0.08). Results indicate that climate in the Brooks Range from 10 to 730 AD (varve year) was warm with precipitation inferred to be higher than during the twentieth century. The varvetemperature relationship for this period was likely compromised and not used in our temperature reconstruction because the glacier was greatly reduced, or absent, exposing sub-glacial sediments to erosion from enhanced precipitation. Varve-inferred summer temperatures and precipitation decreased after 730 AD, averaging 0.4A degrees C above the last millennial average (LMA = 4.2A degrees C) from 730 to 850 AD, and 0.1A degrees C above the LMA from 850 to 980 AD. Cooling culminated between 980 and 1030 AD with temperatures 0.7A degrees C below the LMA. Varve-inferred summer temperatures increased between 1030 and 1620 AD to the LMA, though the period between 1260 and 1350 AD was 0.2A degrees C below the LMA. Although there is no equivalent to the European Medieval Warm Period in the Blue Lake record, two warm intervals occurred from 1350 to 1450 AD and 1500 to 1620 AD (0.4 and 0.3A degrees C above the LMA, respectively). During the Little Ice Age (LIA; 1620 to 1880 AD), inferred summer temperature averaged 0.2A degrees C below the LMA. After 1880 AD, inferred summer temperature increased to 0.8A degrees C above the LMA, glaciers retreated, but aridity persisted based on a number of regional paleoclimate records. Despite warming and glacial retreat, varve thicknesses have not achieved pre-730 AD levels. This reflects limited sediment availability and transport due to a less extensive retreat compared to the first millennium, and continued relative aridity. Overall, the Blue Lake record is similar to varve records from the

  17. 1400 yr multiproxy record of climate variability from the northern Gulf of Mexico

    USGS Publications Warehouse

    Richey, J.N.; Poore, R.Z.; Flower, B.P.; Quinn, T.M.

    2007-01-01

    A continuous decadal-scale resolution record of climate variability over the past 1400 yr in the northern Gulf of Mexico was constructed from a box core recovered in the Pigmy Basin, northern Gulf of Mexico. Proxies include paired analyses of Mg/Ca and δ18O in the white variety of the planktic foraminifer Globigerinoides ruber and relative abundance variations of G. sacculifer in the foraminifer assemblages. Two multi-decadal intervals of sustained high Mg/Ca indicate that Gulf of Mexico sea surface temperatures (SSTs) were as warm or warmer than near-modern conditions between 1000 and 1400 yr B.P. Foraminiferal Mg/Ca during the coolest interval of the Little Ice Age (ca. 250 yr B.P.) indicate that SST was 2–2.5 °C below modern SST. Four minima in the Mg/Ca record between 900 and 250 yr B.P. correspond with the Maunder, Spörer, Wolf, and Oort sunspot minima, suggesting a link between changes in solar insolation and SST variability in the Gulf of Mexico. An abrupt shift recorded in both δ18Ocalcite and relative abundance of G. sacculifer occurred ca. 600 yr B.P. The shift in the Pigmy Basin record corresponds with a shift in the sea-salt-sodium (ssNa) record from the Greenland Ice Sheet Project 2 ice core, linking changes in high-latitude atmospheric circulation with the subtropical Atlantic Ocean.

  18. The terrestrial paleoclimatic record of climate-system reorganization over the past 21,000 years (Invited)

    NASA Astrophysics Data System (ADS)

    Bartlein, P. J.

    2009-12-01

    The terrestrial paleoclimatic record of the past 21,000 years provides a range of different paleoclimatic indicators (proxies) that have sufficient time depth and resolution to allow comparisons with the time series of climatic variables generated by transient climate-model simulations. In addition, the terrestrial record can provide documentation of the synchrony or diachrony of particular events or steps in the reorganization of climate, during both the deglaciation and Holocene. When combined with marine and ice-core records, the terrestrial record will allow diagnosis of the spatial expressions of key events or stages in the reorganization of the climate system (such as the beginning and end of the Younger Dryas climate reversal or African Humid Period), and the long-term evolution of short-term variability such ENSO and other climate modes. In addition to the issues raised in “benchmarking” time-slice climate simulations, the joint application of the terrestrial record and the output from transient simulations will require the development of new protocols for data-model comparisons.

  19. Recording of climate and diagenesis through fossil pigments and sedimentary DNA at Laguna Potrok Aike, Argentina

    NASA Astrophysics Data System (ADS)

    Vuillemin, A.; Ariztegui, D.; Leavitt, P. R.; Bunting, L.; Pasado Science Team

    2015-11-01

    Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. Although marine sedimentary microbial assemblages are often defined by their surrounding geochemical conditions, the influence of environmental features upon microbial development and post-depositional survival remains largely unknown in the lacustrine realm. Due to long-term microbial activity, the composition of environmental DNA can be expected to evolve with sediment depth and over time and therefore should reflect both ancient and extant microbial populations, but this hypothesis has rarely been tested using a multiproxy approach. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two well defined climatic intervals whose sediments harboured active microbial populations and measurable ATP were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. Bacterial and archaeal 16S rRNA gene sequences recovered from the Holocene record revealed a microbial community adapted to subsaline conditions actively producing methane during organic matter degradation. These characteristics were associated with sediments resulting from endorheic lake conditions with high evaporative stress and concomitant high algal productivity. Moreover, archaeal clone libraries established throughout the Holocene record indicate an age-related stratification of these populations, consistent with a gradual use of organic substrates after deposition. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. These patterns

  20. An organic geochemical record of Sierra Nevada climate since the LGM from Swamp Lake, Yosemite

    NASA Astrophysics Data System (ADS)

    Street, Joseph H.; Anderson, R. Scott; Paytan, Adina

    2012-04-01

    Sediment records from Swamp Lake (SL) in the central Sierra Nevada, California, provide evidence of climatic change on millennial and centennial timescales over the last ˜20,000 years. Total organic carbon (TOC) abundance varied in concert with elemental and isotopic tracers of organic matter (C/N, δ13Corg, δ15N), biogenic silica content, total magnetic susceptibility, and sediment lithology. We interpret the down-core proxy records as representing the response of the lake environment, in terms of temperature, seasonal ice cover, mixing regimes, runoff and in situ OM and nutrient cycling, to shifting climate states. These environmental factors in turn drove changes in algal productivity, OM sources, microbial OM regeneration and secondary production, and detrital input. The late Pleistocene (˜19.7-10.8 cal. kyr BP) was dominated by fluctuations between relatively warm/dry intervals with high TOC (17.4-16.5, 15.8-15.0, 13.9-13.2, 11.4-11.0 cal. kyr BP) and cold/wet intervals (16.5-15.8, 14.8-13.9, 13.1-11.6, 11.0-10.7 cal. kyr BP) characterized by low TOC and high detrital input. The Holocene (˜10.7 cal. kyr BP - present) was characterized by three abrupt increases in TOC (after ˜10.8, 8.0, and 3.0 cal. kyr BP) and numerous century-scale fluctuations. TOC increases reflected enhanced lake productivity and OM recycling, and reduced detrital input, in response to changing winter temperature and hydrologic regimes. Inferred environmental changes at SL correlate with other Sierra Nevada paleorecords, and with reconstructed sea surface temperatures along the California margin. Parallel changes in the SL and SST records over the past ˜20,000 years provide new evidence that continental climate in the Sierra Nevada and the California Current system have responded, on multiple timescales, to common drivers in North Pacific ocean-atmospheric circulation.

  1. Abrupt climate changes of the last deglaciation detected in a Western Mediterranean forest record

    NASA Astrophysics Data System (ADS)

    Fletcher, W. J.; Sanchez Goñi, M. F.; Peyron, O.; Dormoy, I.

    2010-04-01

    Abrupt changes in Western Mediterranean climate during the last deglaciation (20 to 6 cal ka BP) are detected in marine core MD95-2043 (Alboran Sea) through the investigation of high-resolution pollen data and pollen-based climate reconstructions by the modern analogue technique (MAT) for annual precipitation (Pann) and mean temperatures of the coldest and warmest months (MTCO and MTWA). Changes in temperate Mediterranean forest development and composition and MAT reconstructions indicate major climatic shifts with parallel temperature and precipitation changes at the onsets of Heinrich stadial 1 (equivalent to the Oldest Dryas), the Bölling-Allerød (BA), and the Younger Dryas (YD). Multi-centennial-scale oscillations in forest development occurred throughout the BA, YD, and early Holocene. Shifts in vegetation composition and (Pann reconstructions indicate that forest declines occurred during dry, and generally cool, episodes centred at 14.0, 13.3, 12.9, 11.8, 10.7, 10.1, 9.2, 8.3 and 7.4 cal ka BP. The forest record also suggests multiple, low-amplitude Preboreal (PB) climate oscillations, and a marked increase in moisture availability for forest development at the end of the PB at 10.6 cal ka BP. Dry atmospheric conditions in the Western Mediterranean occurred in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas), GI-1b (Intra-Allerød Cold Period) and GS-1 (YD), and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to Western-central Europe relates to the dynamics of the westerlies and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alboran Sea by 200 years (surface water age 600 years

  2. Combining the AIRS, CrIS and IASI Radiance Records for Climate Level Retrievals

    NASA Astrophysics Data System (ADS)

    Strow, L. L.

    2016-12-01

    The AIRS record is now 14+ years long, and with the addition of CrIS should provide a 30+ year long hyperspectral radiance record that can be supplemented with another two times in the diurnal cycle with IASI starting in 2007. The stability of these sensors can be established by comparisons to CO2 variability and to tropical sea surface temperature trends. At present the observed stabilities are much better than climate requirements of 0.01/year. SNO observations indicate radiometric agreement among these sensors of 0.1 - 0.3K before any empirical adjustments. A 1-year set of SNO overlaps have statistical uncertainties of less than 0.01K between these three sensors. Moreover, we show that IASI can be used as a transfer standard between AIRS and CrIS (or between CrIS-1 and CrIS-2) should there be a gap in overlap of sensors in the PM orbit. We have done these SNO comparisons by converting AIRS and IASI spectral to the CrIS instrument lineshape (ILS). Achieving climate quality retrievals, trends, and anomalies of temperature and humidity is non-trivial and requires error characterization (not validation) that to date has not been done with single-footprint hyperspectral sensor retrievals. We suggest that the infrared hyperspectral community utilize a common ILS radiance product as a first-step in achieving climate-quality retrievals in order to remove uncertainties in differential instrument sensitivies and in different forward radiative transfer models. We propose a very different approach for Level 3 (climate) products where anomalies and trends (one of the main products of interest to the climate community) are derived directly from Level 3 radiance products, giving far superior error traceability and retrieval regularization in the vertical. Tempertature and humidity trends and anomalies for 14-years of AIRS will be presented and compared to those provided by ERA-Interim, AIRS Level3 data, and microwave sensors. A significant advantage of this approach, which

  3. NALPS: a precisely dated European climate record 120-60 ka

    NASA Astrophysics Data System (ADS)

    Boch, R.; Cheng, H.; Spötl, C.; Edwards, R. L.; Wang, X.; Häuselmann, Ph.

    2011-11-01

    Accurate and precise chronologies are essential in understanding the rapid and recurrent climate variations of the Last Glacial - known as Dansgaard-Oeschger (D-O) events - found in the Greenland ice cores and other climate archives. The existing chronological uncertainties during the Last Glacial, however, are still large. Radiometric age data and stable isotopic signals from speleothems are promising to improve the absolute chronology. We present a record of several precisely dated stalagmites from caves located at the northern rim of the Alps (NALPS), a region that favours comparison with the climate in Greenland. The record covers most of the interval from 120 to 60 ka at an average temporal resolution of 2 to 22 yr and 2σ-age uncertainties of ca. 200 to 500 yr. The rapid and large oxygen isotope shifts of 1 to 4.5‰ occurred within decades to centuries and strongly mimic the Greenland D-O pattern. Compared to the updated Greenland ice-core timescale (GICC05modelext) the NALPS record confirms the timing of rapid warming and cooling transitions between 118 and 106 ka, but suggests younger ages for D-O events between 106 and 60 ka. As an exception, the timing of the rapid transitions into and out of the stadial following GI 22 is earlier in NALPS than in the Greenland ice-core timescale. In addition, there is a discrepancy in the duration of this stadial between the ice-core and the stalagmite chronology (ca. 2900 vs. 3650 yr). The short-lived D-O events 18 and 18.1 are not recorded in NALPS, provoking questions with regard to the nature and the regional expression of these events. NALPS resolves recurrent short-lived climate changes within the cold Greenland stadial and warm interstadial successions, i.e. abrupt warming events preceding GI 21 and 23 (precursor-type events) and at the end of GI 21 and 25 (rebound-type events), as well as intermittent cooling events during GI 22 and 24. Such superimposed events have not yet been documented outside Greenland.

  4. A Lake Sediment Record of Climate Change and Human-Environment Interactions in Southwestern China

    NASA Astrophysics Data System (ADS)

    Hillman, A.; Abbott, M.; Yu, J.; Steinman, B. A.

    2012-12-01

    The delivery of precipitation to southwestern China is largely through monsoon circulation which has evolved with changing insolation during the Holocene. Additionally, southwestern China has a long history of human activity including mining, metallurgy, agriculture, and pollution. Here, high-resolution sampling of a sediment core from Lake Xing Yun in the Yunnan Province (24°10'N, 102°46'E), a drought sensitive lake that behaves as a closed basin system, provides a sub-decadal record of changing climate and human activity in the late Holocene. We use δ18O and δ13C measurements of authigenic carbonate precipitated from the lake water, magnetic susceptibility values, and hydrologic mass balance models to document the timing, direction, and magnitude of moisture changes associated with variations in monsoon strength. We also use δ13C and δ15N measurements on organic matter, carbon to nitrogen ratios, and sediment trace metal concentrations to assess the impact of human activity on the Xing Yun watershed. The 2,500 year record highlights several transition periods related to both human and climate forcing. The rise of intensive irrigation of the lake associated with agriculture occurs at 900 AD, coincident with the rise of metallurgy and mining activities. The period from 1200 to 1360 AD is marked by an abrupt decrease in δ18O values indicating that lake-level rose at this time. We attribute this to a shifting demographic change associated with political upheaval, which is supported by the leveling off of trace metal concentrations and the stagnation of metallurgy and mining activities. The most pronounced feature of the record is a rapid transition to substantially lower lake levels that persisted from 1360-1850 AD. This can be attributed to the return of dramatic human modification to the watershed and changing monsoon strength associated with the Little Ice Age. Using hydrologic mass balance models we are able to quantify the change that can be ascribed to

  5. Uncertainty Propagation in a Fundamental Climate Data Record derived from Meteosat Visible Band Data

    NASA Astrophysics Data System (ADS)

    Rüthrich, Frank; John, Viju; Roebeling, Rob; Wagner, Sebastien; Viticchie, Bartolomeo; Hewison, Tim; Govaerts, Yves; Quast, Ralf; Giering, Ralf; Schulz, Jörg

    2016-04-01

    The series of Meteosat First Generation (MFG) Satellites provides a unique opportunity for the monitoring of climate variability and of possible changes. 6 Satellites were operationally employed; all equipped with identical MVIRI radiometers. The time series now covers, for some parts of the globe, more than 34 years with a high temporal (30 minutes) and spatial (2.5 x 2.5 km²) resolution for the visible band. However, subtle differences between the radiometers in terms of the silicon photodiodes, sensor spectral ageing and variability due to other sources of uncertainties have limited the thorough exploitation of this unique time series so far. For instance upper level wind fields and surface albedo data records could be derived and used for the assimilation into Numerical Weather Prediction models for re-analysis and climate studies, respectively. However, the derivation of aerosol depth with high quality has not been possible so far. In order to enhance the quality of MVIRI reflectances for enabling an aerosol and improved surface albedo data record it is necessary to perform a re-calibration of the MVIRI instruments visible bands that corrects for above mentioned effects and results in an improved Fundamental Climate Data Record (FCDR) of Meteosat/MVIRI radiance data. This re-calibration has to be consistent over the entire period, to consider the ageing of the sensor's spectral response functions and to add accurate information about the combined uncertainty of the radiances. Therefore the uncertainties from all different sources have to be thoroughly investigated and propagated into the final product. This presentation aims to introduce all sources of uncertainty present in MVIRI visible data and points on the major mechanisms of uncertainty propagation. An outlook will be given on the enhancements of the calibration procedure as it will be carried out at EUMETSAT in the course of the EU Horizon 2020 FIDUCEO project (FIDelity and Uncertainty in Climate data

  6. Prediction of Arctic plant phenological sensitivity to climate change from historical records.

    PubMed

    Panchen, Zoe A; Gorelick, Root

    2017-03-01

    The pace of climate change in the Arctic is dramatic, with temperatures rising at a rate double the global average. The timing of flowering and fruiting (phenology) is often temperature dependent and tends to advance as the climate warms. Herbarium specimens, photographs, and field observations can provide historical phenology records and have been used, on a localised scale, to predict species' phenological sensitivity to climate change. Conducting similar localised studies in the Canadian Arctic, however, poses a challenge where the collection of herbarium specimens, photographs, and field observations have been temporally and spatially sporadic. We used flowering and seed dispersal times of 23 Arctic species from herbarium specimens, photographs, and field observations collected from across the 2.1 million km(2) area of Nunavut, Canada, to determine (1) which monthly temperatures influence flowering and seed dispersal times; (2) species' phenological sensitivity to temperature; and (3) whether flowering or seed dispersal times have advanced over the past 120 years. We tested this at different spatial scales and compared the sensitivity in different regions of Nunavut. Broadly speaking, this research serves as a proof of concept to assess whether phenology-climate change studies using historic data can be conducted at large spatial scales. Flowering times and seed dispersal time were most strongly correlated with June and July temperatures, respectively. Seed dispersal times have advanced at double the rate of flowering times over the past 120 years, reflecting greater late-summer temperature rises in Nunavut. There is great diversity in the flowering time sensitivity to temperature of Arctic plant species, suggesting climate change implications for Arctic ecological communities, including altered community composition, competition, and pollinator interactions. Intraspecific temperature sensitivity and warming trends varied markedly across Nunavut and could

  7. Climatic conditions for the last Neanderthals: Herpetofaunal record of Gorham’s Cave, Gibraltar.

    PubMed

    Blain, Hugues-Alexandre; Gleed-Owen, Chris P; López-García, Juan Manuel; Carrión, José Sebastian; Jennings, Richard; Finlayson, Geraldine; Finlayson, Clive; Giles-Pacheco, Francisco

    2013-04-01

    Gorham’s Cave is located in the British territory of Gibraltar in the southernmost end of the Iberian Peninsula. Recent excavations, which began in 1997, have exposed an 18 m archaeological sequence that covered the last evidence of Neanderthal occupation and the first evidence of modern human occupation in the cave. By applying the Mutual Climatic Range method on the amphibian and reptile assemblages, we propose here new quantitative data on the terrestrial climatic conditions throughout the latest Pleistocene sequence of Gorham’s Cave. In comparison with current climatic data, all mean annual temperatures were about 1.6-1.8 degrees C lower in this region. Winters were colder and summers were similar to today. Mean annual precipitation was slightly lower, but according to the Aridity Index of Gaussen there were only four dry months during the latest Pleistocene as opposed to five dry months today during the summer. The climate was Mediterranean and semi-arid (according to the Aridity Index of Dantin-Revenga) or semi-humid (according to the Aridity Index of Martonne). The atmospheric temperature range was higher during the latest Pleistocene, mainly due to lower winter temperatures. Such data support recent bioclimatic models, which indicate that high rainfall levels may have been a significant factor in the late survival of Neanderthal populations in southern Iberia. The Solutrean levels of Gorham’s Cave and climate records from cores in the Alboran Sea indicate increasing aridity from Marine Isotope Stage (MIS) 3-2. Because Neanderthals seem to have been associated with woodland habitats, we propose that lessening rainfall may have caused the degradation of large areas of forest and may have made late surviving Neanderthal populations more vulnerable outside southern refuges like the Rock of Gibraltar.

  8. Late Holocene interdecadal climate variability in the Sahel: inferences from a marine dust record offshore Senegal

    NASA Astrophysics Data System (ADS)

    Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.

    2009-04-01

    Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid Sahel belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of Sahel climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4

  9. A speleothem record of rapid climate shifts during the last deglaciation from northern Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Moreno, A.; Stoll, H. M.; Jimenez-Sanchez, M.; Cacho, I.; Valero-Garces, B.; Ito, E.; Edwards, R. L.

    2009-04-01

    We present a high resolution speleothem record of the last deglaciation from NW Spain, which provides as an important link between the millennial climate variability well characterized in the North Atlantic and Greenland, and the correlative abrupt climate changes observed in high accumulation rate marine cores in the western Mediterranean. The nearly continuous record from stalagmite CANDELA, from 25.5 to 11.6 ky BP documents with high resolution and precise chronology the climate change in NW Iberia from the Late Glacial period through the end of the Younger Dryas. By combining trace element indicators of aridity with oxygen and carbon isotopic tracers sensitive to temperature and moisture-source, this record provides an integrated perspective on the climate changes experienced by the region. Carbon isotopic variations reflect temperature and humidity regulation of vegetation and soil respiration and dripwater degassing. Oxygen isotopic variations reflect a more complex array of processes including temperature-driven changes in isotopic fractionation during calcite precipitation, changes in sources of moisture in the hydrological cycle, and changes in seasonality of precipitation. Mg/Ca and Ba/Ca respond to the hydrological balance (P-E) through soil contact times and extent of prior calcite precipitation. This location in NW Spain is particularly sensitive to climate disruptions caused by changes in the North Atlantic Meridional Overturning Circulation (MOC). Stalagmite growth ceases only during the 2 ky shutdown of the MOC known as the Mystery Interval, but not during the preceding glacial maximum or GS-3 stages which are colder in Greenland and are periods in which speleothem growth is absent farther north on the Atlantic or Mediterranean coasts of France. Thus, in NW Iberia this Mystery Interval is potentially the coldest and driest interval of the presented record. Cold interludes in the North Atlantic region, such as Heinrich event 2, were characterized by

  10. Terrestrial and marine records of climatic and environmental changes during the Pliocene in subtropical Florida

    USGS Publications Warehouse

    Willard, D.A.; Cronin, T. M.; Ishman, S.E.; Litwin, R.J.

    1993-01-01

    Pollen, ostracode, and benthic foraminifer assemblages deposited during sea-level highstands in subtropical Florida record a climate change during the period 4.5-1.0 Ma. Before 3.5 Ma, open-shelf marine faunas and pollen assemblages with abundant Pinus, Quercus, Fagus, Carya, and nonarboreal pollen were present, indicating cooler conditions than today. From ~3.5 to 1.0 Ma, marine and terrestrial records indicate warmer conditions, similar to those existing in south Florida today. Combined with evidence for much warmer than modern conditions at high latitudes, these data suggest that increased poleward oceanic heat transport, possibly related to the emergence of the Central American isthmus between ~3.5 and 2.5 Ma, was a major influence on mid-Pliocene warmth. -Authors

  11. Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

    2016-04-01

    The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. Glaciers rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of glacier activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent glacier activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold

  12. Spatio-temporal dynamics of global precipitation and terrestrial vegetation inferred from satellite and climate records

    NASA Astrophysics Data System (ADS)

    Lotsch, Alexander

    A key challenge to climate change research is understanding how different components in the Earth system influence one another. For example, it is well known that the Earth's climate system exhibits variability at a wide range of time scales. However, the effect of such variability on terrestrial ecosystems is less well understood. In this dissertation, satellite observations of vegetation activity are used in conjunction with climate records to investigate seasonal-scale interactions between the Earth's terrestrial biosphere, atmosphere, and oceans. The results from this research show that interannual variation in the ocean-atmosphere system result in significant and geographically extensive ecosystem responses. To characterize spatio-temporal patterns of biospheric activity, multi-decadal (1981--2003) global satellite observations of plant growth were used. Non-linear variance decomposition methods were employed to remove artifacts unrelated to vegetation dynamics and to identify climate-related signatures in the data. Vegetation growth in arid and semi-arid regions exhibits strong correlation with interannual fluctuations in precipitation, and responds most strongly to time-integrated precipitation anomalies. The climate mechanisms that give rise to observed patterns of precipitation-vegetation covariability are associated with perturbations in ocean-atmosphere circulations. Generally, these perturbations are caused by low frequency fluctuations in global sea surface temperatures, which are propagated to remote locations via changes in atmospheric circulation. The analysis shows that distinct patterns of coupled climate-vegetation activity are linked to well-defined circulation features and illustrates the global extent and sensitivity of ecosystems susceptible to perturbations in precipitation regimes. Observations of ecosystem dynamics derived from recent satellite data reveal unprecedented reductions in vegetation growth for large areas of the Northern

  13. Shoreline and Lacustrine Records of Late Quaternary Climate Change in the Chihuahuan Desert, Mexico

    NASA Astrophysics Data System (ADS)

    Castiglia, P. J.; Fawcett, P. J.

    2001-12-01

    Spatial and temporal patterns of Quaternary moisture and temperature variability in northern Mexico are difficult to reconstruct given the paucity of continuous, long-term Quaternary climate records from the region. Preliminary shoreline age dates and a pair of lacustrine sediment cores from Laguna Fresnal in northern Chihuahua, Mexico, record climate-driven variations in both lake level and sedimentologic input. Reeves (1969) first described Laguna Fresnal as part of Pluvial Lake Palomas, a Pleistocene lake composed of 3 interconnected sub-basins: Laguna Guzman, Santa Maria, and Fresnal. Six AMS 14C age dates from previously unrecognized lake fauna on a beach ridge complex indicate a number of Holocene lakes as well. These preserved shorelines increase in age with distance and elevation from the playa surface and include early Holocene (8456\\pm97 14C yrs BP; 1225 m asl), middle Holocene (6180\\pm53, 6401\\pm58, and 6721\\pm68 14C yrs BP; 1200 m asl), and Little Ice Age (435\\pm39 14C yrs BP; 1175 m asl) lake stands. These ages correlate with beach ridge chronologies throughout the western US and northern Mexico. However, during the middle Holocene Laguna Fresnal exhibits a pronounced high stand while other records show a prolonged dry episode. Two 17 m-long cores from the basin center provide a continuous record of sedimentation during the late Quaternary. Several abrupt changes in lake level are indicated by mud cracks preserved as sharp, light gray lineations (487-548 cm and 975-1130 cm), sharply overlain by finely laminated silt and clay. Drying episodes are preserved in the basal section of the cores as several 0.5-2 cm-thick gypsum horizons, overlain by 3-5 cm-thick, carbon-poor (0.02-0.05% TOC), light gray silt. Five distinct zones of coupled, alternating relatively high and low average magnetic susceptibility (MS) and bulk density further reveals changes in lacustrine sedimentation. Peaks in MS generally correlate with peaks in bulk density, with the

  14. Past climate changes and ecophysiological responses recorded in the isotope ratios of saguaro cactus spines.

    PubMed

    English, Nathan B; Dettman, David L; Sandquist, Darren R; Williams, David G

    2007-11-01

    The stable isotope composition of spines produced serially from the apex of columnar cacti has the potential to be used as a record of changes in climate and physiology. To investigate this potential, we measured the delta(18)O, delta(13)C and F(14)C values of spines from a long-lived columnar cactus, saguaro (Carnegiea gigantea). To determine plant age, we collected spines at 11 different heights along one rib from the stem apex (3.77 m height) to the base of a naturally occurring saguaro. Fractions of modern carbon (F(14)C) ranged from 0.9679 to 1.5537, which is consistent with ages between 1950 and 2004. We observed a very strong positive correlation (r = 0.997) between the F(14)C age of spines and the age of spines determined from direct and repeated height measurements taken on this individual over the past 37 years. A series of 96 spines collected from this individual had delta(18)O values ranging from 38 per thousand to 50 per thousand [Vienna standard mean ocean water (VSMOW)] and delta(13)C values from -11.5 per thousand to -8.5 per thousand [Vienna Peedee belemnite (VPDB)]. The delta(18)O and delta(13)C values of spines were positively correlated (r = 0.45, P < 0.0001) and showed near-annual oscillations over the approximately 15-year record. This pattern suggests that seasonal periods of reduced evaporative demand or greater precipitation input may correspond to increased daytime CO(2) uptake. The lowest delta(18)O and delta(13)C values of spines observed occurred during the 1983 and 1993 El Niño years, suggesting that the stable isotope composition recorded in spine tissue may serve as a proxy for these climate events. We compared empirical models and data from potted experimental cacti to validate these observations and test our hypotheses. The isotopic records presented here are the first ever reported from a chronosequence of cactus spines and demonstrate that tissues of columnar cacti, and potentially other long-lived succulents, may contain a

  15. Oxygen isotope records of Holocene climate variability in the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Steinman, Byron A.; Pompeani, David P.; Abbott, Mark B.; Ortiz, Joseph D.; Stansell, Nathan D.; Finkenbinder, Matthew S.; Mihindukulasooriya, Lorita N.; Hillman, Aubrey L.

    2016-06-01

    Oxygen isotope (δ18O) measurements of authigenic carbonate from Cleland Lake (southeastern British Columbia), Paradise Lake (central British Columbia), and Lime Lake (eastern Washington) provide a ∼9000 year Holocene record of precipitation-evaporation balance variations in the Pacific Northwest. Both Cleland Lake and Paradise Lake are small, surficially closed-basin systems with no active inflows or outflows. Lime Lake is surficially open with a seasonally active overflow. Water isotope values from Cleland and Paradise plot along the local evaporation line, indicating that precipitation-evaporation balance is a strong influence on lake hydrology. In contrast, Lime Lake water isotope values plot on the local meteoric water line, signifying minimal influence by evaporation. To infer past hydrologic balance variations at a high temporal resolution, we sampled the Cleland, Paradise, and Lime Lake sediment cores at 1-60 mm intervals (∼3-33 years per sample on average) and measured the isotopic composition of fine-grained (<63 μm) authigenic CaCO3 in each sample. Negative δ18O values, which indicate wetter conditions in closed-basin lakes, occur in Cleland Lake sediment from 7600 to 2200 years before present (yr BP), and are followed by more positive δ18O values, which suggest drier conditions, after 2200 yr BP. Highly negative δ18O values in the Cleland Lake record centered on ∼2400 yr BP suggest that lake levels were high (and that the lake may have been overflowing) at this time as a result of a substantially wetter climate. Similarly, Paradise Lake sediment δ18O values are relatively low from 7600 to 4000 yr BP and increase from ∼4000 to 3000 yr BP and from ∼2000 yr BP to present, indicating that climate became drier from the middle through the late Holocene. The δ18O record from Lime Lake, which principally reflects changes in the isotopic composition of precipitation, exhibits less variability than the closed-basin lake records and follows a

  16. Rock Magnetic Record of the Middle Miocene Climatic Transition at ODP Site 747, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Abrajevitch, A.; Roberts, A. P.; Kodama, K.

    2013-12-01

    ODP Site 747, located on the central Kerguelen Plateau, contains a compete record of the Middle Miocene Climatic Transition (MMCT) - a major cooling event that followed the warm mid-Miocene Climatic Optimum and culminated in an 'icehouse' climate regime. Because of its unusually well preserved and rich foraminiferal assemblages, the MMCT interval at Site 747 has been a focus of several high-resolution paleoclimatic studies that have effectively established this sequence as a reference for the Southern Ocean. Major changes in species abundances across the MMCT are conventionally interpreted to reflect changes in water temperature and salinity. Our XRF and rock magnetic study reveals a good correlation between terrigenous input (likely from local volcanic sources) and the abundances of the dominant planktonic foraminiferal species. Such a correlation suggests that nutrient flux (iron fertilization) played a significant role in controlling microplankton communities during the MMCT at Site 747. Concentration-dependent rock magnetic parameters appear to be a useful proxy for nutrient flux in this pelagic marine environment.

  17. A 30+ Year AVHRR LAI and FAPAR Climate Data Record: Algorithm Description, Validation, and Case Study

    NASA Technical Reports Server (NTRS)

    Claverie, Martin; Matthews, Jessica L.; Vermote, Eric F.; Justice, Christopher O.

    2016-01-01

    In- land surface models, which are used to evaluate the role of vegetation in the context ofglobal climate change and variability, LAI and FAPAR play a key role, specifically with respect to thecarbon and water cycles. The AVHRR-based LAIFAPAR dataset offers daily temporal resolution,an improvement over previous products. This climate data record is based on a carefully calibratedand corrected land surface reflectance dataset to provide a high-quality, consistent time-series suitablefor climate studies. It spans from mid-1981 to the present. Further, this operational dataset is availablein near real-time allowing use for monitoring purposes. The algorithm relies on artificial neuralnetworks calibrated using the MODIS LAI/FAPAR dataset. Evaluation based on cross-comparisonwith MODIS products and in situ data show the dataset is consistent and reliable with overalluncertainties of 1.03 and 0.15 for LAI and FAPAR, respectively. However, a clear saturation effect isobserved in the broadleaf forest biomes with high LAI (greater than 4.5) and FAPAR (greater than 0.8) values.

  18. A 30+ Year AVHRR LAI and FAPAR Climate Data Record: Algorithm Description, Validation, and Case Study

    NASA Technical Reports Server (NTRS)

    Claverie, Martin; Matthews, Jessica L.; Vermote, Eric F.; Justice, Christopher O.

    2016-01-01

    In- land surface models, which are used to evaluate the role of vegetation in the context ofglobal climate change and variability, LAI and FAPAR play a key role, specifically with respect to thecarbon and water cycles. The AVHRR-based LAIFAPAR dataset offers daily temporal resolution,an improvement over previous products. This climate data record is based on a carefully calibratedand corrected land surface reflectance dataset to provide a high-quality, consistent time-series suitablefor climate studies. It spans from mid-1981 to the present. Further, this operational dataset is availablein near real-time allowing use for monitoring purposes. The algorithm relies on artificial neuralnetworks calibrated using the MODIS LAI/FAPAR dataset. Evaluation based on cross-comparisonwith MODIS products and in situ data show the dataset is consistent and reliable with overalluncertainties of 1.03 and 0.15 for LAI and FAPAR, respectively. However, a clear saturation effect isobserved in the broadleaf forest biomes with high LAI (greater than 4.5) and FAPAR (greater than 0.8) values.

  19. Carbonaceous aerosol tracers in ice-cores record multi-decadal climate oscillations.

    PubMed

    Seki, Osamu; Kawamura, Kimitaka; Bendle, James A P; Izawa, Yusuke; Suzuki, Ikuko; Shiraiwa, Takayuki; Fujii, Yoshiyuki

    2015-09-28

    Carbonaceous aerosols influence the climate via direct and indirect effects on radiative balance. However, the factors controlling the emissions, transport and role of carbonaceous aerosols in the climate system are highly uncertain. Here we investigate organic tracers in ice cores from Greenland and Kamchatka and find that, throughout the period covered by the records (1550 to 2000 CE), the concentrations and composition of biomass burning-, soil bacterial- and plant wax- tracers correspond to Arctic and regional temperatures as well as the warm season Arctic Oscillation (AO) over multi-decadal time-scales. Specifically, order of magnitude decreases (increases) in abundances of ice-core organic tracers, likely representing significant decreases (increases) in the atmospheric loading of carbonaceous aerosols, occur during colder (warmer) phases in the high latitudinal Northern Hemisphere. This raises questions about causality and possible carbonaceous aerosol feedback mechanisms. Our work opens new avenues for ice core research. Translating concentrations of organic tracers (μg/kg-ice or TOC) from ice-cores, into estimates of the atmospheric loading of carbonaceous aerosols (μg/m(3)) combined with new model constraints on the strength and sign of climate forcing by carbonaceous aerosols should be a priority for future research.

  20. Carbonaceous aerosol tracers in ice-cores record multi-decadal climate oscillations

    PubMed Central

    Seki, Osamu; Kawamura, Kimitaka; Bendle, James A. P.; Izawa, Yusuke; Suzuki, Ikuko; Shiraiwa, Takayuki; Fujii, Yoshiyuki

    2015-01-01

    Carbonaceous aerosols influence the climate via direct and indirect effects on radiative balance. However, the factors controlling the emissions, transport and role of carbonaceous aerosols in the climate system are highly uncertain. Here we investigate organic tracers in ice cores from Greenland and Kamchatka and find that, throughout the period covered by the records (1550 to 2000 CE), the concentrations and composition of biomass burning-, soil bacterial- and plant wax- tracers correspond to Arctic and regional temperatures as well as the warm season Arctic Oscillation (AO) over multi-decadal time-scales. Specifically, order of magnitude decreases (increases) in abundances of ice-core organic tracers, likely representing significant decreases (increases) in the atmospheric loading of carbonaceous aerosols, occur during colder (warmer) phases in the high latitudinal Northern Hemisphere. This raises questions about causality and possible carbonaceous aerosol feedback mechanisms. Our work opens new avenues for ice core research. Translating concentrations of organic tracers (μg/kg-ice or TOC) from ice-cores, into estimates of the atmospheric loading of carbonaceous aerosols (μg/m3) combined with new model constraints on the strength and sign of climate forcing by carbonaceous aerosols should be a priority for future research. PMID:26411576

  1. Little Ice Age Glaciation in Alaska: A record of recent global climatic change

    SciTech Connect

    Calkin, P.E.; Wiles, G.C.

    1992-03-01

    General global cooling and temperature fluctuation accompanied by expansion of mountain glaciers characterized the Little Ice Age of about A.D. 1200 through A.D. 1900. The effects of such temperature changes appear first and are strongest at high latitudes. Therefore the Little Ice Age record of glacial fluctuation in Alaska may provide a good proxy for these events and a test for models of future climatic change. Holocene expansions began here as early as 7000 B.P. and locally show a periodicity of 350 years after about 4500 years B.P. The Little Ice Age followed a late Holocene interval of minor ice advance and a subsequent period of ice margin recession lasting one to seven centuries. The timing of expansions since about A.D. 1200 have often varied between glaciers, but these are the most pervasive glacial events of the Holocene in Alaska and frequently represent ice marginal maxima for this interval. At least two major expansions are, apparent in forefields of both land-terminating and fjord-calving glaciers, but the former display the most reliable and detailed climatic record. Major maxima occurred by the 16th century and into the mid-18th century. Culmination of advances occurred throughout Alaska during the 19th century followed within a few decades by general glacial retreat. Concurrently, equilibrium line altitudes have been raised 100-400 m, representing a rise of 2-3 deg C in mean summer temperature.

  2. Ecological changes in Miocene mammalian record show impact of prolonged climatic forcing.

    PubMed

    Badgley, Catherine; Barry, John C; Morgan, Michèle E; Nelson, Sherry V; Behrensmeyer, Anna K; Cerling, Thure E; Pilbeam, David

    2008-08-26

    Geohistorical records reveal the long-term impacts of climate change on ecosystem structure. A 5-myr record of mammalian faunas from floodplain ecosystems of South Asia shows substantial change in species richness and ecological structure in relation to vegetation change as documented by stable isotopes of C and O from paleosols. Between 8.5 and 6.0 Ma, C(4) savannah replaced C(3) forest and woodland. Isotopic historical trends for 27 mammalian herbivore species, in combination with ecomorphological data from teeth, show three patterns of response. Most forest frugivores and browsers maintained their dietary habits and disappeared. Other herbivores altered their dietary habits to include increasing amounts of C(4) plants and persisted for >1 myr during the vegetation transition. The few lineages that persisted through the vegetation transition show isotopic enrichment of delta(13)C values over time. These results are evidence for long-term climatic forcing of vegetation structure and mammalian ecological diversity at the subcontinental scale.

  3. Holocene climate variability in the Levant from the Dead Sea pollen record

    NASA Astrophysics Data System (ADS)

    Litt, Thomas; Ohlwein, Christian; Neumann, Frank H.; Hense, Andreas; Stein, Mordechai

    2012-08-01

    The Dead Sea, located at the deepest place on continent and between the subtropical Mediterranean zone and the desert, reflects in its water composition and levels, and sedimentary records the hydrological conditions in the southern Levant region. Temporal variations in rainfall and temperatures of the Holocene Levant are reconstructed here from pollen data recovered from a sediment core drilled at the Ein Gedi shore, applying a novel biome model based on Bayesian statistics. Our results suggest that the region was arid and warm in the early Holocene period (˜10-6.5 ka cal BP), wetter and colder in the mid Holocene (6.3-3.3 ka cal BP), and drier and warmer in the late Holocene (˜3.2 ka cal BP to present). These periods comprise multi-centennial climate cycles that are characterized by rapid changes in temperature and precipitation reflecting Sea Surface Temperature (SST) and atmospheric conditions over the Atlantic Ocean. The pollen record responds within a short time interval to the climate conditions and marks rapid shifts from Mediterranean to desert environmental conditions and back in the southern Levant region. We also evaluate our results in the light of possible disturbances of the natural vegetation, e.g. the possibility of forest decrease, since the Neolithic.

  4. New Holocene tephras and a proxy climate record from a blanket mire in northern Skye, Scotland

    NASA Astrophysics Data System (ADS)

    Langdon, P. G.; Barber, K. E.

    2001-12-01

    Four Holocene tephras of Icelandic origin have been identified and geochemically characterised from a water shedding blanket peat sequence on the Trotternish ridge, Isle of Skye, Scotland. Geochemical characterisation of the shards propose the Glen Garry tephra to be present, a tephra layer of Hekla origin incorporating shards from Hekla-4, as well as two new tephras dated by interpolation from a radiocarbon based chronology to ca. 830 cal. yr BP and ca. 2340 cal. yr BP. The new historic tephra has an ambiguous geochemistry and therefore has not been correlated with other known Icelandic historic tephras. The new prehistoric tephra is suggested as originating from the Snæfellsjökull volcano in northwest Iceland and forms an important stratigraphical marker in this Holocene sequence. A proxy climate record has been derived from humification analyses of the peat, which compares well with other regional palaeoclimatic reconstructions, as well as enabling correlations based on tephra geochemical linkages between sites and climatic records at precise times in the past.

  5. Potential of treeline bristlecone pine as a late Holocene climate record

    NASA Astrophysics Data System (ADS)

    Salzer, M. W.; Hughes, M. K.; Bunn, A. G.; Kipfmueller, K. F.

    2010-12-01

    Due to their length, annual resolution, and sensitivity to climate, bristlecone pine tree-ring records are highly valuable paleoclimate archives. In previous work we have shown that ring widths from three upper-treeline sites in the Great Basin, USA showed ring growth in the second half of the 20th century that was greater than any in the last three and a half millennia and that is well correlated to temperature (Salzer et al. 2009). The changing pattern of growth characteristics with elevation does not support a dominant role for carbon dioxide mediated increased water-use efficiency at these tree-line sites. We have expanded our analyses to create long multimillennial time series of both raw ring-width and standardized ring-width index. These annually-resolved time series extend nearly 5000 years into the past. Our approach allows for both the creation of estimates of uncertainty to assess the reliability of the chronologies through time, and for the retention of decadal- through multicentury-scale variability that is unavailable in most tree-ring records. We discuss these results in the context of western US climate during the second half of the Holocene with particular emphasis on the last 2000 years. Reference: Salzer, M.W., Hughes, M.K., Bunn, A. and Kipfmueller, K. F. Recent unprecedented tree-ring growth in bristlecone pine at the highest elevations and possible causes. Proceedings of the National Academy of Science. doi: 10.1073/pnas.0903029106 (2009).

  6. Climatic changes and anthropogenic pollution as evidenced by two Alpine lacustrine records, Switzerland.

    NASA Astrophysics Data System (ADS)

    Thevenon, Florian; Poté, John; Guédron, Stéphane; Adatte, Thierry; Chiaradia, Massimo; Loizeau, Jean-Luc; Spangenberg, Jorge; Anselmetti, Flavio S.

    2010-05-01

    This study aims to provide high-resolution records of climatic changes and human impacts on two different Alpine environments: Lake Lucerne is a large (114 km2) lake located at 434 m asl in Central Switzerland, whereas Meidsee is a small (<1 km2) remote lake located at 2661 m asl in the Southern Alps. Two short gravity cores (1.2 and 1.6 m) recovering the industrial history and the last millennia were sampled with a resolution of 1 cm, and investigated for organic (13δC, 15δN, C/N) and/or inorganic (δ13C, δ18O) matter contents, and elemental composition (REE compositions, trace elements, and heavy metals). Both sites exhibit 1) rapid hydrological changes related to variations in winter precipitations, and 2) increases in atmospheric pollution due to human activities. Lead enrichment factors combined to changes in lead isotopic composition (206Pb/207Pb ratio) are used to distinguish natural from anthropogenic sources. The greatest mercury and lead atmospheric emissions occurred during the twentieth century, resulting from the extensive combustion of fossil coal and petroleum in Europe. Although the highest heavy metals fluxes are synchronous with major anthropogenic changes (e.g. Roman mining, industrial revolution), proxies show that in absence of such events, the heavy metals deposition in the sedimentary records is primarily influenced by sedimentological processes linked to climate variations (i.e. runoff and erosion processes).

  7. Pliocene climate along a 42-52° North latitude European transect documented by pollen records

    NASA Astrophysics Data System (ADS)

    Popescu, Speranta-Maria; Biltekin, Demet; Winter, Hanna; Suc, Jean-Pierre; Melinte-Dobrinescu, Mihaela Carmen; Klotz, Stefan; Rabineau, Marina

    2010-05-01

    Climate characteristics (temperature, rainfall, seasonality) of Europe were already documented by several pollen records (Suc et al., 1995; Fauquette et al., 1999; Popescu, 2006; Fauquette et al., 2007; Jiménez-Moreno et al., 2007). Two new pollen records at high chronological resolution of the whole Pliocene (5.33 - 2.6 Ma) and early Pleistocene (DSDP Site 380 in the southwestern Black Sea and Wólka Ligezowska in southern Poland, at 42 and 51° North latitude, respectively), provide detailed information in two key-regions. DSDP Site 380 pollen diagram shows a continuous competition between thermophilous forests and Artemisia steppes, while thermophilous-mesophilous forests contrast with coniferous boreal forests then the latter with toundra-park at Wólka Ligezowska (Popescu et al., accepted). The narrow relationship between Site 380 pollen curves (especially the "thermophilous elements / steppe elements" ratio) and the oxygen isotope reference ones allows (1) to accurately characterize the cyclic evolution of climate progressively leading from warm to glacial conditions along a 10° in latitude gradient in Europe, and (2) to define phytogeographical provinces with their distinction both in mean annual temperature with respect to latitude and in seasonality (temperature, precipitations) according to their geographic location.

  8. Multi-proxy records of Eocene vegetation and climatic dynamics from North America

    NASA Astrophysics Data System (ADS)

    Sheldon, N. D.; Smith, S. Y.; Stromberg, C. A.; Hyland, E.; Miller, L. A.

    2010-12-01

    The Eocene is characterized by a “thermal maximum” in the early part, and a shift to “icehouse” conditions by the end of the epoch. Consequently, this is an interesting time to look at vegetation dynamics and understanding plant responses to environmental change, especially as refinement of global climate models is needed if we are to understand future climate change impacts. Paleobotanical evidence, such as phytoliths (plant silica bodies), and paleoenvironmental indicators, such as paleosols, offer an opportunity to study vegetation composition and dynamics in the absence of macrofossils on a variety of spatial and temporal scales. To examine the interaction between paleoclimatic/paleoenvironmental changes and paleovegetation changes, we will compare and contrast two well-dated, high-resolution, multi-proxy records from North America. The margins of the Green River Basin system during the Early Eocene Climatic Optimum (53-50 Ma) are an extremely important location for understanding ecological composition and potential climatic drivers of North American floral diversification, because this area is widely considered the point of origin for many modern grass clades. We examined paleosols preserved in the fluvial, basin-margin Wasatch Formation preserved near South Pass, Wyoming. Field identification of the paleosols indicated a suite that includes Entisols, Inceptisols, and Alfisols. To reconstruct paleovegetation, pedogenic carbonates were analyzed isotopically, and samples were collected and extracted for phytoliths . By combining these paleobotanical proxies with quantitative climatic proxies on whole rock geochemistry, we will present an integrated vegetation-climate history of the EECO at the margins of the Green River Basin. Second, we will present high-resolution record of vegetation patterns based on phytoliths from a section of the Renova Formation, Timberhills region, Montana dated to 39.2 ± 3 Ma. The section is composed of Alfisols, Entisols

  9. Marine record of Holocene climate, ocean, and cryosphere interactions: Herbert Sound, James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Minzoni, Rebecca Totten; Anderson, John B.; Fernandez, Rodrigo; Wellner, Julia Smith

    2015-12-01

    The sediment record offshore James Ross Island, northeast Antarctic Peninsula presents an unparalleled opportunity to directly compare marine and terrestrial climate records spanning the Holocene in maritime Antarctica. An 11 m drill core was collected between Herbert Sound and Croft Bay as part of the SHALDRIL NBP-0502 initiative and produced the southernmost sediment record from the eastern side of the AP. Thirty-eight radiocarbon ages are used to construct an age model of centennial-scale resolution. Multi-proxy records, including magnetic susceptibility, pebble content, particle size, total organic carbon, and diatom assemblages, were interrogated in the context of nearby Holocene-age ice core, lake, and drift records from James Ross Island. Differences in the timing and expression of Holocene events reflect marine controls on tidewater glaciers, such as water mass configurations and sea ice. Glacial behavior mimics ice core paleotemperatures during the Holocene, with the exception of distinct ocean warming events. Herbert Sound was fully occupied by grounded ice during the Last Glacial Maximum, and experienced rapid lift-off, followed by a floating ice phase. The canopy of floating ice receded by 10 ± 2.4 cal kyr BP, presumably in response to Early Holocene warming. Herbert Sound and Croft Bay fully deglaciated by 7.2 cal kyr BP, when the Mid Holocene Hypsithermal commenced and the sound became open and productive. An extreme peak in productivity ∼6.1 cal kyr BP indicates an oceanic warming event that is not reflected in atmospheric temperature or lacustrine sediment records. Increase in sea ice cover and ice rafting mark the onset of the Neoglacial ∼2.5 cal kyr BP, when pronounced atmospheric cooling is documented in the James Ross Island ice core. Our comparison facilitates more holistic understanding of atmosphere-ocean-cryosphere interactions that may aid predictions of glacial response to future warming and sea-level scenarios.

  10. The Integration of SMOS Soil Moisture in a Consistent Soil Moisture Climate Record

    NASA Astrophysics Data System (ADS)

    de Jeu, Richard; Kerr, Yann; Wigneron, Jean Pierre; Rodriguez-Fernandez, Nemesio; Al-Yaari, Amen; van der Schalie, Robin; Dolman, Han; Drusch, Matthias; Mecklenburg, Susanne

    2015-04-01

    Recently, a study funded by the European Space Agency (ESA) was set up to provide guidelines for the development of a global soil moisture climate record with a special emphasis on the integration of SMOS. Three different data fusion approaches were designed and implemented on 10 year passive microwave data (2003-2013) from two different satellite sensors; the ESA Soil Moisture Ocean Salinity Mission (SMOS) and the NASA/JAXA Advanced Scanning Microwave Radiometer (AMSR-E). The AMSR-E data covered the period from January 2003 until Oct 2011 and SMOS data covered the period from June 2010 until the end of 2013. The fusion approaches included a neural network approach (Rodriguez-Fernandez et al., this conference session HS6.4), a regression approach (Wigneron et al., 2004), and an approach based on the baseline algorithm of ESAs current Climate Change Initiative soil moisture program, the Land Parameter Retrieval Model (Van der Schalie et al., this conference session HS6.4). With this presentation we will show the first results from this study including a description of the different approaches and the validation activities using both globally covered modeled datasets and ground observations from the international soil moisture network. The statistical validation analyses will give us information on the temporal and spatial performance of the three different approaches. Based on these results we will then discuss the next steps towards a seamless integration of SMOS in a consistent soil moisture climate record. References Wigneron J.-P., J.-C. Calvet, P. de Rosnay, Y. Kerr, P. Waldteufel, K. Saleh, M. J. Escorihuela, A. Kruszewski, 'Soil Moisture Retrievals from Bi-Angular L-band Passive Microwave Observations', IEEE Trans. Geosc. Remote Sens. Let., vol 1, no. 4, 277-281, 2004.

  11. Extending the Satellite Derived Climate DATA Record of Sea Surface Temperature with VIIRS

    NASA Astrophysics Data System (ADS)

    Kilpatrick, K. A.; Williams, E.; Walsh, S.; Evans, R.; Szczodrak, M.; Izaguirre, M.; Minnett, P. J.

    2014-12-01

    Sea surface temperature (SST) is an essential variable needed to monitor and understand climate change. The global coverage provided by polar orbiting satellites is seen as the basis of SST climate records (CDRs). Such CDRs require accurate and traceable determination of the uncertainty characteristics of the SST retrievals from the long time series of measurements, taken by a sequence of satellite radiometers of evolving design and capabilities. The most recent of these instruments is the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP (National Polar-orbiting Partnership). The results of continuing analyses of the first three years of VIIRS measurements of skin SST are presented. The analyses include assessments of the spatial and temporal characteristics of the uncertainties, and comparisons to other satellite-based infrared sensors. VIIRS that has a swath width >3000km is much wider than either the MODIS or AVHRR, offers potentially gap-free coverage between adjacent swaths. However, current algorithms for retrieving SST from the infrared have increased uncertainty, and typically larger cold biases, at higher viewing angles. Alternative algorithmic approaches were developed at Miami to overcome some of the shortcomings identified in operational algorithms and to provide more accurate retrievals across the entire swath width. Additional terms have been added to a VIIRS atmospheric correction algorithm to account for the effects of the high emission angle and long atmospheric path lengths. We conclude that reprocessed VIIRS SSTs using this enhanced algorithm would be capable of improving upon the accuracies of SSTs from the MODIS's on Terra and Aqua, and AVHRR Pathfinder, and have the potential to contribute to the extension of the satellite-derived Climate Data Records of SST into the future.

  12. Geomorphological records of extreme floods and their relationship to decadal-scale climate change

    NASA Astrophysics Data System (ADS)

    Foulds, S. A.; Griffiths, H. M.; Macklin, M. G.; Brewer, P. A.

    2014-07-01

    Extreme rainfall and flood events in steep upland catchments leave geomorphological traces of their occurrence in the form of boulder berms, debris cones, and alluvial fans. Constraining the age of these features is critical to understanding (i) landscape evolution in response to past, present, and future climate changes; and (ii) the magnitude-frequency of extreme, ungauged floods in small upland catchments. This research focuses on the Cambrian Mountains of Wales, UK, where lichenometric dating of geomorphological features and palaeohydrological reconstructions is combined with climatological data and documentary flood records. Our new data from Wales highlight a distinct flood-rich period between 1900 and 1960, similar to many other UK lichen-dated records. However, this study sheds new light on the underlying climatic controls on upland flooding in small catchments. Although floods can occur in any season, their timing is best explained by the Summer North Atlantic Oscillation (SNAO) and shifts between negative (wetter than average conditions with regular cyclonic flow and flooding) and positive phases (drier than average conditions with less frequent cyclonic flow and flooding), which vary from individual summers to decadal and multidecadal periods. Recent wet summer weather, flooding, and boulder-berm deposition in the UK (2007-2012) are related to a pronounced negative phase shift of the SNAO. There is also increasing evidence that recent summer weather extremes in the mid-latitudes may be related to Arctic amplification and rapid sea ice loss. If this is the case, continuing and future climate change is likely to mean that (i) unusual weather patterns become more frequent; and (ii) upland UK catchments will experience heightened flood risk and significant geomorphological changes.

  13. The Accumulation Record from the GISP2 Core as an Indicator of Climate Change Throughout the Holocene.

    PubMed

    Meese, D A; Gow, A J; Grootes, P; Stuiver, M; Mayewski, P A; Zielinski, G A; Ram, M; Taylor, K C; Waddington, E D

    1994-12-09

    A depth-age scale and an accumulation history for the Holocene have been established on the Greenland Ice Sheet Project 2 (GISP2) deep core, providing the most continuously dated record of annual layer accumulation currently available. The depth-age scale was obtained with the use of various independent techniques to count annual layers in the core. An annual record of surface accumulation during the Holocene was obtained by correcting the observed layer thicknesses for flow-thinning. Fluctuations in accumulation provide a continuous and detailed record of climate variability over central Greenland during the Holocene. Climate events, including "Little Ice Age" type events, are examined.

  14. Enhanced multidecadal climate variability in the seventeenth century from coral isotope records in the western Indian Ocean

    NASA Astrophysics Data System (ADS)

    Damassa, Thomas D.; Cole, Julia E.; Barnett, Heidi R.; Ault, Toby R.; McClanahan, Timothy R.

    2006-06-01

    The slowly growing coral Diploastreaheliopora affords a novel opportunity to obtain multicentury records of paleoclimate, including details of the interannual rhythms associated with the El Niño-Southern Oscillation (ENSO) system. We examine climate variability in an ENSO-teleconnected region using new oxygen isotope records from D. heliopora, spanning most of the twentieth (1896-1998) and seventeenth (1622-1722) centuries, from the Mafia archipelago, Tanzania. The modern record demonstrates coherency with relevant instrumental and proxy time series, documents twentieth century warming, and displays significant power at ENSO periodicities. The seventeenth century record lacks any trend, exhibits interannual variance comparable to the modern record, and displays a pronounced interdecadal signal not evident in the twentieth century that correlates with other tropical and hemispheric climate records. We find no clear evidence of solar irradiance influence on interannual variability in the western Indian Ocean during these intervals, although the mean sea surface temperature appears to vary inversely with insolation.

  15. Long-Term Sun Climate Connections, Revealed by the Analyses of Historical and Other Proxy Records

    NASA Astrophysics Data System (ADS)

    Pang, K. D.; Yau, K.

    2004-12-01

    The Sun, once considered constant, actually goes through 11-year, decadal, centennial, and even longer cycles. Our analysis of historical sunspot and aurora records, carbon-14 and beryllium-10 abundances from long-lived trees and deep polar ice cores, respectively, shows that it has gone through nine long cycles in the past 1800 years. Although these changes amounted to <1% of the total irradiance there is clear evidence they produced corresponding changes in the climate [Pang and Yau, Eos, 83, No. 43, 481, 2002]. For example during the Maunder Minimum (1645-1715) sunspots were rarely seen (about once in ten years from Europe or China). Total solar irradiances, reconstructed from historical sunspot records, were 0.25% lower then. This correlates nicely with an estimated 0.5-degree drop in Northern Hemisphere summer surface temperatures during the Little Ice Age [Lean, GRL 22, 3195, 1995]. We have also analyzed Chinese historical weather records for comparison. Reports of unseasonable cold are classified by the degree of severity: (1) Late (April-June) or early (July-September) killing frosts; (2) Bitter cold/heavy snowfall; and (3) Heavy sustained snowfall, bitter cold with frozen wells, rivers and icebound seas. The latter cases were often widespread and multi-year. All categories occurred most frequently during the coldest part of the Little Ice Age. The Category 3 episodes were in 1652-54, 1656, 1664, 1670-72, 1676-77, 1683, 1688-91, 1716, and 1718-19. For example the Yangtze River and its lakes froze up to 3-4 times in 1650-1700. The coldest period thus coincides with the Maunder Minimum, and is consistent with general circulation model hindcast winter conditions for China [Shindell, Science, 294, 2149, 2001]. There was only one Category 3 episode between the Maunder and Dalton Minima--in 1761 (due to a large volcanic eruption); and two in the Dalton Minimum (1795-1825)--in 1796 and 1814-17. The Sun has gradually brightened since the Dalton Minimum. But the

  16. A Complete Holocene High-resolution Multiproxy Climate Record from the Northern Great Plains

    NASA Astrophysics Data System (ADS)

    Grimm, E. C.; Donovan, J. J.; Brown, K. J.

    2010-12-01

    The decadal-resolution multiproxy (mineralogy, pollen, charcoal) record from Kettle Lake, North Dakota encompasses the entire Holocene, with a chronology established by over 50 AMS radiocarbon dates. This record exhibits millennial scale trends evident in other lower-resolution studies, but with substantially greater detail on the rapidity and timing of major climatic shifts and on short-term climate variability. This record utilizes the rate of endogenic carbonate sedimentation, which depends on the rate of groundwater flow into the lake, as a sensitive proxy for precipitation, especially suitable for lakes supported by water from highly permeable carbonate-rich aquifers. Independent cluster analyses of mineral and pollen data reveal major Holocene mode shifts at 10.73 ka (ka = cal yr BP), 9.25 ka, and 4.44 ka. The early Holocene, 11.7-9.25 ka, is generally wet, with perhaps a trend to higher evaporation associated with warming temperatures. A switch from calcite to aragonite deposition is associated with a severe, but brief, drought at 10.73 ka. From 10.73 ka to 9.25 ka, a generally humid climate is punctuated at 100-300 yr intervals by brief droughts, including the most severe drought of the entire Holocene at 9.25 ka. The number of droughts during this period, including the bracketing droughts at 10.73 ka and 9.25 ka, is comparable to the number of Lake Agassiz recessions and outbursts during this period. Furthermore, the bracketing droughts correspond in age to the largest draw downs (30 and 58 m). Based on this evidence, we propose that droughts evident in the aragonite record at Kettle Lake were induced by either (a) local climate effects related to decreased size of or increased distance from Lake Agassiz, or (b) teleconnections with North Atlantic thermohaline changes associated with Agassiz outbursts. With the retreat of Lake Agassiz far to the north from the Stonewall beach at 9.25 ka, the “Agassiz lake effect” on NGP humidity was removed, and NGP

  17. Cosmogenic production vs. climate for the nitrate record in the TALDICE Antarctic ice core

    NASA Astrophysics Data System (ADS)

    Poluianov, Stepan; Usoskin, Ilya; Traversi, Rita

    Reconstructions of solar activity on the multimillennial scale are based usually on records of two cosmogenic isotopes (14) C and (10) Be, measured in tree trunks or ice cores. In addition to these well-known proxies, a chemical tracer was recently proposed (Traversi et al., 2012), viz. nitrate, measured in an Antarctic ice sheet with moderate snow deposition rate. Tropo-stratospheric production of nitrate by cosmic rays is significant in polar regions because of the effect of energetic galactic cosmic rays. However, some climatic factors can influence a nitrate record there. Since the strongest source of nitrate is located at low and middle latitudes as driven by thunderstorm activity, the possible air transport from the lower latitudes to the polar region may significantly distort the signal of solar activity in a nitrate record. The present work is focused on a statistical study of the relation between the air transport from low and middle latitudes and the nitrate deposition in the polar region. We used the data from the TALDICE drilling project (Talos Dome, Antarctica). As galactic cosmic ray indices we used the reconstructions of heliospheric moderation parameter based on (14) C from INTCAL09 and (10) Be from GRIP. The data series cover the age range from 675 till 12000 years BP (i.e. before 1950). We applied the wavelet coherence analysis to compare the nitrate series with a number of substances/proxies: Na(+) , Ca(2+) , MSA (methanesulphonic acid), delta(18) O, no-sea-salt-SO_4(2-) and reconstructions of heliospheric modulation parameter from the (14) C and (10) Be records. We found (1) a confirmation that the multimillennial variability of nitrate is in inverse relation with cosmic ray flux; (2) no sign of the nitrate transport from lower latitudes to the site of deposition. This suggests that variations in the nitrate record in the time scale of hundreds-thousands of years are most likely caused by local production and deposition processes.

  18. A 50,000-year climatic record from the new coastal TALDICE ice core: consequences on millennial-scale variability features through the Antarctic continent

    NASA Astrophysics Data System (ADS)

    Buiron, Daphné; Stenni, Barbara; Frezzoti, Massimo; Chappellaz, Jerome; Lemieux, Benedicte; Masson-Delmotte, Valérie; Schilt, Adrian

    2010-05-01

    The TALDICE project retrieved a new ice core from a peripheral dome of East Antarctica. Talos Dome (72° 49' S, 159° 11' E; 2315 m; mean accumulation rate 80 kg m-2 yr-1; mean annual temp. -41°C) is located in the Northern Victoria Land, close to the Ross Sea. Back-trajectory analyses suggest that the site is mostly fed by air masses arriving both from the Pacific (and Ross Sea) and Indian Ocean sectors. The drilling team reached the depth of 1619.2 m in December 2007, covering more than 300,000 years of climatic records according to a preliminary age scale. Up to 50,000 years before present, the ice core dating is based on the use of a glaciological model and an inverse method, constrained by numerous and reliable age markers. They are defined from the synchronization of CH4 records of Talos Dome and Greenland ice cores, using in particular the rapid CH4 changes associated with the last termination and the D/O events. Measurements of the CH4 mixing ratio have been performed by LGGE and Bern laboratories using slightly different techniques, with a depth resolution ranging between 0.5 to 4 m. The comparison of water isotopic profiles from Talos Dome, EDC, EDML (Antarctica) and North-GRIP (Greenland) ice cores, once put on a common time scale deduced from CH4 and the optimisation from the inverse method, reveals that during the last deglaciation and the last glacial period, climatic changes at Talos Dome were essentially in phase with the Antarctic plateau, extending the bipolar seesaw sequence to this coastal site. This comparison also highlights different climatic behaviors between sites situated in the Indo/Pacific sector and in the Atlantic sector of the Southern Ocean, the latter showing more abrupt swings toward relatively warm conditions of the Antarctic Isotope Maxima. We will discuss this feature with respect to the bipolar seesaw model of Stocker (2003) and with respect to other climatic proxies.

  19. A Quarter Century Record of Stratospheric Sulfate Aerosol: implication for the past, present and future climates

    NASA Astrophysics Data System (ADS)

    Shaheen, R.; Abaunza, M.; Jackson, T. L.; McCabe, J.; Savarino, J.; Thiemens, M. H.

    2014-12-01

    Stratospheric sulfate aerosol (SSA) plays an important role in the earth climate system by reflecting solar radiation making it an attractive candidate in geoengineering to counter greenhouse warming. However, these planetary scales perturbations demand a priori understanding of SSA over a longer time period to resolve anthropogenic and natural perturbations to the delicate and thin layers- SSA and ozone layers. Here we present a quarter century high resolution seasonal record of SSA and its linkage to the ozone layer. Sulfate was extracted from a (1x1m) and 25m deep snow pit at the South Pole. The combination of cations, anions, O-triple isotopes and S-quadruple isotope measurements allowed us to deconvolve the oxidation history of SSA and tease out natural and anthropogenic components. The period (1980 to 2002) encompasses the largest volcanic eruptions of the century, El-Chichon, Pinatubo, Cerro Hudson and the three largest El-Nino Southern Oscillation events. The highest O-isotope anomaly (∆17O = 3.7‰) in SSA was observed during the super ENSO event (1997-98) and recorded changes in ozone levels of the upper troposphere-lower stratosphere (1). ENSO is another flavor of natural climate variability and is important as it links hydrosphere and the atmosphere in unique ways controlling rainfall and temperature. The highest S-isotope anomaly was observed in 1998-99 and records changes in atmospheric dynamics and transport of sulfur compounds to the stratosphere following intense wild fires as a consequence of the Super ENSO event. The highest S-isotopic anomaly (∆33S = +2.26‰ and ∆36S= +0.51 ‰) is ~ 3 times higher compared to the Pinatubo signal, the largest volcanic eruption of the 20th century. The pattern of S-isotope anomalies in this period fits within the pre-Cambrian record of S-isotopes in three billion year old rock. The generation of such a large S-isotope anomaly in the present day oxygen rich atmosphere may have implications for the

  20. Let's Develop Climate Proxies that Relate to Human Experience, Namely Records of Storm Activity

    NASA Astrophysics Data System (ADS)

    Lawrence, J. R.

    2005-12-01

    The human experience of climate change is not one of gradual changes in seasonal or yearly changes in temperature or rainfall. Despite that most paleoclimatic reconstructions attempt to provide just such information. Humans experience climate change on much shorter time scales. Storms or the lack there of are what we experience. We remember hurricanes, weeks of drought or overwhelming rainy periods. Storms in the tropics, particularly hurricanes and mesoscale convective complexes produce very low isotope ratios in both water vapor in the atmosphere and in rainfall. These low isotope ratios occur as spikes in surface waters and atmospheric water vapor. Two regions of Mexico hold considerable promise for producing paleoclimatic records of storm activity. The coast of northeast Mexico and south Texas is a region of arid climate subject to extensive flooding when there is tropical cyclone activity. The southwest coast of Mexico is adjacent to the most intensive concentration of tropical cyclone activity in the world. In 2001 Tropical Storm Allison stalled over Houston, Texas long enough to produce a meter of rainfall. A lake was produced having an oxygen isotope value of -11.4 permil. This isotopic spike slowly increased to a value of -2 per mil over a three-week period. The carbonate shells of living Ostracoda species, Cypridopsis and Potamocypris, were collected from the lake and have been shown to have recorded the low isotope ratios in the lake. In 1998 in Puerto Escondido, Mexico where relatively little rain fell from July 10 to July 31 compared to the oceanic region to the southwest the isotopic composition of water vapor in the atmosphere reflected the storm activity offshore and the wind patterns in the greater regional area. If the isotopic composition of the water vapor is reflected in the leaf water of trees and then in cellulose the potential exists for reconstructing tropical cyclone activity over the last few centuries. If we as scientists are going to

  1. A 250,000-year climatic record from great basin vein calcite: Implications for Milankovitch theory

    USGS Publications Warehouse

    Winograd, I.J.; Szabo, B. J.; Coplen, T.B.; Riggs, A.C.

    1988-01-01

    A continuous record of oxygen-18 (??18O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole - an open fault zone at Ash Meadows, Nevada - between 50 and 310 ka (thousand years ago). The configuration of the ??18O versus time curve closely resembles the marine and Antarctic ice core (Vostok) ??18O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 ?? 3 ka, at least 17,000 years earlier than indicated by the marine ??18O record and 7,000 years earlier than indicated by the less well dated Antarctic ??18O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine ??18O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

  2. Organic matter preservation: A proxy for Turonian climatic shifts recorded during relative sea-level stillstands

    SciTech Connect

    White, T.S.; Arthur, M.A.; Dean, W.

    1996-12-31

    We performed analyses of organic matter obtained from cores across Utah, Colorado, and Kansas. The results provide a detailed (30 cm sampling interval) record of organic matter preservation in the Turonian seaway during highstand (HST), lowstand (LST) and overlying transgressive systems tract (TST) deposition in the Western Interior Seaway. In general, total organic carbon (TOC) and carbonate (CaCO3) percentages decrease through the HST, with the highest values obtained from strata deposited during maximum transgression. Organic matter within the early- to mid-HST is dominantly marine algae with dinoflagellate and foraminiferal inputs. The late-HST contains small quantities of TOC and CaCO3, characterized as terrestrial organic debris; early-LST sediments have a signature similar to the late-HST. As one might expect, during sea-level fall the basin records mostly terrestrial inputs, whereas during sea-level rise a marine signature prevails. A similarity exists between late-LST and early-HST TOC and CaCO3 contents and is noteable for fluctuations between terrestrial and marine organic matter as indicated by Rockeval pyrolyses, organic petrography, and palynology. We surmise that during mid-HST and late-LST (i.e. during times of little or no variation in rate of sea-level change), the basin is poised to record fluctuations between terrestrial and marine-dominated sediment deposition which may be controlled by changes in climate.

  3. A 250,000-year climatic record from great basin vein calcite: implications for milankovitch theory.

    PubMed

    Winograd, I J; Coplen, T B; Szabo, B J; Riggs, A C

    1988-12-02

    A continuous record of oxygen-18 (delta(18)O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole-an open fault zone at Ash Meadows, Nevada-between 50 and 310 ka (thousand years ago). The configuration of the delta(18)O versus time curve closely resembles the marine and Antarctic ice core (Vostok) delta(18)O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 +/- 3 ka, at least 17,000 years earlier than indicated by the marine delta(18)O record and 7,000 years earlier than indicated by the less well dated Antarctic delta(18)O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine delta(18)O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

  4. Reconstruction of climate dynamics in an Arctic fjord environment: evidence from a multi-proxy high resolution marine record.

    NASA Astrophysics Data System (ADS)

    MacLachlan, S. E.; Howe, J.

    2012-12-01

    The cryosphere is a crucial component of the Earth's climate system, and comprises sea ice, snow, glaciers, ice cap, ice shelves, river and lake ice, ice sheets and frozen ground. The cryosphere has shown ice growth and decay on many timescales associated both with 100,000 year ice age cycles and with shorter-term (<2000 yrs) variations such as the Younger Dryas and the Little Ice Age. Crucially the cyosphere acts as a barometer for climate change because it provides a visible means of assessing the impacts of recent climate warming. Coastal Arctic regions are particularly sensitive to climate change, and records of glacier fluctuations can be used to infer past climate. The western Svalbard margin is a climatically sensitive region presently influenced by the warm and saline Atlantic water of the West Spitsbergen Current. This current is the northernmost extension of the Norwegian Atlantic Current that transports significant quantities of heat northward, maintaining the seas west of the Svalbard shelf increasingly ice free. For the Svalbard area there are currently a number of low-resolution (centennial to multi-decadal) marine records that span the Holocene. Despite their low resolution, several studies have highlighted abrupt environmental shifts and fluctuating glacial conditions during the Holocene. A few low-resolution lake records and other sporadic terrestrial datasets also exist providing a limited insight into the terrestrial environmental changes over the last two millennia. We have generated the first sub-decadal resolution late Holocene climatic record, in order to determine the nature and timing of environmental changes across transient climate events at an unprecedented temporal scale for this region. XRF analyses provides the high-resolution data series, which has been integrated with sedimentological data to better define the environmental processes; thus providing the basis for the reconstruction of climate change in this glaciated fjordic

  5. Recording of climate and diagenesis through sedimentary DNA and fossil pigments at Laguna Potrok Aike, Argentina

    NASA Astrophysics Data System (ADS)

    Vuillemin, Aurèle; Ariztegui, Daniel; Leavitt, Peter R.; Bunting, Lynda; The Pasado Science Team

    2016-04-01

    Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. In theory, benthic microbial community composition should depend on environmental features and geochemical conditions of surrounding sediments, as well as ontogeny of the subsurface environment as sediment degraded. In principle, DNA in sediments should be composed of ancient and extant microbial elements persisting at different degrees of preservation, although to date few studies have quantified the relative influence of each factor in regulating final composition of total sedimentary DNA assemblage. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two climatic intervals (Mid-Holocene, 5 ka BP; Last Glacial Maximum, 25 ka BP) whose sediments harbored active microbial populations were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. The genetic assemblage recovered from the Holocene record revealed a microbial community displaying metabolic complementarities that allowed prolonged degradation of organic matter to methane. The series of Archaea identified throughout the Holocene record indicated an age-related stratification of these populations brought on by environmental selection during early diagenesis. These characteristics were associated with sediments resulting from endorheic lake conditions and stable pelagic regime, high evaporative stress and concomitant high algal productivity. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. Comparison of sedimentary DNA composition

  6. Rapid climate fluctuations over the past millennium: evidence from a lacustrine record of Basomtso Lake, southeastern Tibetan Plateau.

    PubMed

    Li, Kai; Liu, Xingqi; Herzschuh, Ulrike; Wang, Yongbo

    2016-04-19

    Abrupt climate changes and fluctuations over short time scales are superimposed on long-term climate changes. Understanding rapid climate fluctuations at the decadal time scale over the past millennium will enhance our understanding of patterns of climate variability and aid in forecasting climate changes in the future. In this study, climate changes on the southeastern Tibetan Plateau over the past millennium were determined from a 4.82-m-long sediment core from Basomtso Lake. At the centennial time scale, the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Current Warm Period (CWP) are distinct in the Basomtso region. Rapid climate fluctuations inferred from five episodes with higher sediment input and likely warmer conditions, as well as seven episodes with lower sediment input and likely colder conditions, were well preserved in our record. These episodes with higher and lower sediment input are characterized by abrupt climate changes and short time durations. Spectral analysis indicates that the climate variations at the centennial scale on the southeastern Tibetan Plateau are influenced by solar activity during the past millennium.

  7. Rapid climate fluctuations over the past millennium: evidence from a lacustrine record of Basomtso Lake, southeastern Tibetan Plateau

    PubMed Central

    Li, Kai; Liu, Xingqi; Herzschuh, Ulrike; Wang, Yongbo

    2016-01-01

    Abrupt climate changes and fluctuations over short time scales are superimposed on long-term climate changes. Understanding rapid climate fluctuations at the decadal time scale over the past millennium will enhance our understanding of patterns of climate variability and aid in forecasting climate changes in the future. In this study, climate changes on the southeastern Tibetan Plateau over the past millennium were determined from a 4.82-m-long sediment core from Basomtso Lake. At the centennial time scale, the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Current Warm Period (CWP) are distinct in the Basomtso region. Rapid climate fluctuations inferred from five episodes with higher sediment input and likely warmer conditions, as well as seven episodes with lower sediment input and likely colder conditions, were well preserved in our record. These episodes with higher and lower sediment input are characterized by abrupt climate changes and short time durations. Spectral analysis indicates that the climate variations at the centennial scale on the southeastern Tibetan Plateau are influenced by solar activity during the past millennium. PMID:27091591

  8. Rapid climate fluctuations over the past millennium: evidence from a lacustrine record of Basomtso Lake, southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, Kai; Liu, Xingqi; Herzschuh, Ulrike; Wang, Yongbo

    2016-04-01

    Abrupt climate changes and fluctuations over short time scales are superimposed on long-term climate changes. Understanding rapid climate fluctuations at the decadal time scale over the past millennium will enhance our understanding of patterns of climate variability and aid in forecasting climate changes in the future. In this study, climate changes on the southeastern Tibetan Plateau over the past millennium were determined from a 4.82-m-long sediment core from Basomtso Lake. At the centennial time scale, the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Current Warm Period (CWP) are distinct in the Basomtso region. Rapid climate fluctuations inferred from five episodes with higher sediment input and likely warmer conditions, as well as seven episodes with lower sediment input and likely colder conditions, were well preserved in our record. These episodes with higher and lower sediment input are characterized by abrupt climate changes and short time durations. Spectral analysis indicates that the climate variations at the centennial scale on the southeastern Tibetan Plateau are influenced by solar activity during the past millennium.

  9. A Bat's-Eye View of Holocene Climate Change in the Southwest: Resolving Ambiguities in Cave Isotopic Records

    NASA Astrophysics Data System (ADS)

    Cole, J. E.; Truebe, S. A.; Harrington, M. D.; Woodhead, J. D.; Overpeck, J. T.; Hlohowskyj, S.; Henderson, G. M.

    2015-12-01

    In dry environments, speleothems provide an outstanding archive of information on past climate change, particularly since lakes are typically absent or intermittent. Speleothem stable isotopes are widely used for climate reconstruction, but the isotope-climate relationship is complex in arid-region precipitation, and within-cave processes further complicate climate interpretations. Our isotope results from 3 southeastern Arizona caves, spanning the past 3.5-12 kyr, collectively indicate a weakening monsoon from 7kyr to present. These records exhibit substantial multidecadal-multicentury variability that is sometimes shared, and sometimes independent among caves. Strategies to overcome ambiguities in isotope records include long-term monitoring of cave dripwaters, multi-site comparisons, and multiproxy measurements. Monthly dripwater measurements from two caves spanning several years highlight substantial seasonal biases that create distinct differences in the climate sensitivity of individual cave records. These biases can lead to lack of correlation between records, but also creates opportunities for seasonally specific moisture reconstructions. New preliminary analyses suggest that elemental data can help to unravel the multivariate signal contained in speleothem oxygen isotope records.

  10. Deriving a sea surface temperature record suitable for climate change research from the along-track scanning radiometers

    NASA Astrophysics Data System (ADS)

    Merchant, C. J.; Llewellyn-Jones, D.; Saunders, R. W.; Rayner, N. A.; Kent, E. C.; Old, C. P.; Berry, D.; Birks, A. R.; Blackmore, T.; Corlett, G. K.; Embury, O.; Jay, V. L.; Kennedy, J.; Mutlow, C. T.; Nightingale, T. J.; O'Carroll, A. G.; Pritchard, M. J.; Remedios, J. J.; Tett, S.

    We describe the approach to be adopted for a major new initiative to derive a homogeneous record of sea surface temperature for 1991 2007 from the observations of the series of three along-track scanning radiometers (ATSRs). This initiative is called (A)RC: (Advanced) ATSR Re-analysis for Climate. The main objectives are to reduce regional biases in retrieved sea surface temperature (SST) to less than 0.1 K for all global oceans, while creating a very homogenous record that is stable in time to within 0.05 K decade-1, with maximum independence of the record from existing analyses of SST used in climate change research. If these stringent targets are achieved, this record will enable significantly improved estimates of surface temperature trends and variability of sufficient quality to advance questions of climate change attribution, climate sensitivity and historical reconstruction of surface temperature changes. The approach includes development of new, consistent estimators for SST for each of the ATSRs, and detailed analysis of overlap periods. Novel aspects of the approach include generation of multiple versions of the record using alternative channel sets and cloud detection techniques, to assess for the first time the effect of such choices. There will be extensive effort in quality control, validation and analysis of the impact on climate SST data sets. Evidence for the plausibility of the 0.1 K target for systematic error is reviewed, as is the need for alternative cloud screening methods in this context.

  11. Climatic stress events in the source region of modern man - Matching the last 20 ka of the Chew Bahir climate record with occupation history of adjacent refugia

    NASA Astrophysics Data System (ADS)

    Foerster, Verena; Vogelsang, Ralf; Junginger, Annett; Asrat, Asfawossen; Lamb, Henry F.; Viehberg, Finn; Trauth, Martin H.; Schaebitz, Frank

    2014-05-01

    A rapidly changing environment is considered an important driver not just for human evolution but also for cultural and technological innovation and migration. To evaluate the impact that climatic shifts on different timescales might have had on the living conditions of prehistoric humans is one of the cornerstones in current research, but continuous paleo-climate records in the vicinity of archaeological sites are still rare. As a contribution towards a better understanding of this human-climate interaction we here present a match between the last 20 ka of the just recently developed paleo-climate record from Chew Bahir in southern Ethiopia and the settlement history of adjacent possible refugia. The Chew Bahir basin, as a newly explored reliable climatic archive, lies in a biogeographically highly sensitive transition zone between the Main Ethiopian Rift and the Omo-Turkana basin and hence represents an ideal site to study climatic variability in the source region of modern man. The climatic history with a temporal resolution of up to 3 years is showing besides orbitally driven long-term transitions in and out of favourable living conditions several short abrupt excursions towards drier or wetter episodes. Comparing the frequency of archaeological findings as a parameter for human occupation to this close-by climate record that allows us to outline how complex the interplay between humans and environment during the last 20 ka really was, which dynamics might have been involved and which role the temporal dimension of environmental changes could have played for the adaption of humans.

  12. A decadal gridded hyperspectral infrared record for climate Sep 1st 2002--Aug 31st 2012

    NASA Astrophysics Data System (ADS)

    Chapman, David Raymond

    We present a gridded Fundamental Decadal Data Record (FDDR) of Brightness Temperatures (BT) from the NASA Atmospheric Infrared Sounder (AIRS) from ten years of hyperspectral Infrared Radiances onboard the NASA EOS Aqua satellite. Although global surface temperature data records are available for over 130 years, it was not until 1978 when the Microwave Sounding Unit (MSU) was the first instrument series to reliably monitor long-term trends of the upper atmosphere. AIRS, operational on September 1, 2002 is the first successful hyperspectral satellite weather instrument of more than 1 year, and provides a 10 year global hyperspectral IR radiance data record. Our contribution was to prepare a gridded decadal data record of climate resolution from the AIRS Outgoing Longwave Spectrum (OLS). In order to do this, we developed a robust software infrastructure "Gridderama" using large multivariate array storage to facilitate this multi-terabyte parallel data processing task while ensuring integrity, tracking provenance, logging errors, and providing extensive visualization. All of our data, code, logs and visualizations are freely available online and browsable via a real-time "Data Catalog" interface. We show that these global all-sky trends are consistent with the expected radiative forcings from an increase in greenhouse gasses. We have also measured high global correlations with the GISS global surface air temperatures as well as high regional anticorrelations with the NOAA ONI index of El Niño phase. In addition, we have performed inter-annual inter-comparisons with the Moderate Resolution Spectro-radiometer (MODIS) on the same Aqua satellite to examine the relative consistency of their calibrations. The comparisons of the two instruments for the 4µ spectral channels (between 3.9µ and 4.1µ) indicate an inter-annual warming of 0.13K per decade of AIRS more than MODIS. This decadal relative drift is small compared to inter-annual variability but on the order of

  13. Climate elasticity of streamflow revisited - an elasticity index based on long-term hydrometeorological records

    NASA Astrophysics Data System (ADS)

    Andréassian, Vazken; Coron, Laurent; Lerat, Julien; Le Moine, Nicolas

    2016-11-01

    We present a new method to derive the empirical (i.e., data-based) elasticity of streamflow to precipitation and potential evaporation. This method, which uses long-term hydrometeorological records, is tested on a set of 519 French catchments. We compare a total of five different ways to compute elasticity: the reference method first proposed by Sankarasubramanian et al. (2001) and four alternatives differing in the type of regression model chosen (OLS or GLS, univariate or bivariate). We show that the bivariate GLS and OLS regressions provide the most robust solution, because they account for the co-variation of precipitation and potential evaporation anomalies. We also compare empirical elasticity estimates with theoretical estimates derived analytically from the Turc-Mezentsev formula. Empirical elasticity offers a powerful means to test the extrapolation capacity of those hydrological models that are to be used to predict the impact of climatic changes.

  14. RETRACTED: Impacts of past climate variability on marine ecosystems: Lessons from sediment records

    NASA Astrophysics Data System (ADS)

    Emeis, Kay-Christian; Finney, Bruce P.; Ganeshram, Raja; Gutiérrez, Dimitri; Poulsen, Bo; Struck, Ulrich

    2010-02-01

    This article has been retracted at the request of the Editor-in-Chief and Author. Please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy). Reason: Paragraph 3.3 of this article contains text (verbatim) that had already appeared in a book chapter "Variability from scales in marine sediments and other historical records" by David B. Field, Tim R. Baumgartner, Vicente Ferreira, Dimitri Gutierrez, Hector Lozano-Montes, Renato Salvatteci and Andy Soutar. The book is entitled "Climate Change and Small Pelagic Fish", 2009, edited by Dave Checkley, Claude Roy, Jurgen Alheit, and Yoshioki Oozeki (Cambridge University Press; 2009).The authors would like to apologize for this administrative error on their part.

  15. A climatic record from 14C-dated wood fragments from southwestern Colorado

    USGS Publications Warehouse

    Epstein, S.; Xu, X.; Carrara, P.

    1999-01-01

    Deuterium concentrations in trees are related to the climatic temperature at which the trees grew. Deuterium analyses were made on all available (39) 14C-dated (all 14C dates cited are uncorrected) wood fragments collected from Lake Emma sediments. The 14C dates range from 9600 to 5400 'B.P.'. Tree line was above Lake Emma at 9600 'B.P.', was at Lake Emma at about 5000 'B.P.', and is 80 m below Lake Emma at the present time. The isotopic records at the various intervals of time coincide very well with this history. The range of ??D values is maximum at 9600 'B.P.' and is minimum at about 5400 'B.P.'. These data allow us to estimate the temperature range for the area between tree line and Lake Emma between these times. These results confirm previously observed cooling trends from several sources in the Western Hemisphere.

  16. Combining Satellite and in Situ Data with Models to Support Climate Data Records in Ocean Biology

    NASA Technical Reports Server (NTRS)

    Gregg, Watson

    2011-01-01

    The satellite ocean color data record spans multiple decades and, like most long-term satellite observations of the Earth, comes from many sensors. Unfortunately, global and regional chlorophyll estimates from the overlapping missions show substantial biases, limiting their use in combination to construct consistent data records. SeaWiFS and MODIS-Aqua differed by 13% globally in overlapping time segments, 2003-2007. For perspective, the maximum change in annual means over the entire Sea WiFS mission era was about 3%, and this included an El NinoLa Nina transition. These discrepancies lead to different estimates of trends depending upon whether one uses SeaWiFS alone for the 1998-2007 (no significant change), or whether MODIS is substituted for the 2003-2007 period (18% decline, P less than 0.05). Understanding the effects of climate change on the global oceans is difficult if different satellite data sets cannot be brought into conformity. The differences arise from two causes: 1) different sensors see chlorophyll differently, and 2) different sensors see different chlorophyll. In the first case, differences in sensor band locations, bandwidths, sensitivity, and time of observation lead to different estimates of chlorophyll even from the same location and day. In the second, differences in orbit and sensitivities to aerosols lead to sampling differences. A new approach to ocean color using in situ data from the public archives forces different satellite data to agree to within interannual variability. The global difference between Sea WiFS and MODIS is 0.6% for 2003-2007 using this approach. It also produces a trend using the combination of SeaWiFS and MODIS that agrees with SeaWiFS alone for 1998-2007. This is a major step to reducing errors produced by the first cause, sensor-related discrepancies. For differences that arise from sampling, data assimilation is applied. The underlying geographically complete fields derived from a free-running model is unaffected

  17. Lacustrine records of continental climate in northwest Greenland through the Holocene and Last Interglacial

    NASA Astrophysics Data System (ADS)

    McFarlin, J. M.; Axford, Y.; Osburn, M. R.; Lasher, G. E.; Francis, D. R.; Kelly, M. A.; Osterberg, E. C.

    2015-12-01

    Lake sediment records provide opportunities for high-resolution observations of paleoclimate that help to place modern climate change in geologic context. Here we present a terrestrial record of July air temperature for northwest Greenland (Nunatarssuaq, ~25 km east of the Thule Air Base) through the Holocene and a prior warm period, inferred from subfossil insect remains (Chironomidae) preserved in lacustrine sediments. In addition, we discuss ongoing work in characterizing the sources and isotopic composition of leaf waxes preserved in the same sediments. Multiple parallel sediment cores were collected in the summers of 2012 and 2014 from Wax Lips Lake (informal name), a non-glacial lake situated <2 km from the current margin of the Greenland Ice Sheet. Radiocarbon ages were obtained on aquatic mosses from intact laminae, and indicate that the record spans the Holocene, beginning at ~10.4 ka, as well as an interval beyond the range of 14C (>44 ka) and thus predates the Last Glacial Maximum (LGM). Our results demonstrate temperatures warmer than present through the early and mid Holocene followed by cooling in the late Holocene. Material that pre-dates the LGM contains insect assemblages indicating temperatures warmer than the warmest millennia of the Holocene. We interpret this material as most likely dating to the Last Interglacial Period (MIS 5). Along with assemblages of Chironomidae, we find subfossil Chaoboridae in one section of the pre-LGM sediments, suggesting exceptionally warm conditions based upon the distribution of modern-day Chaoborus. We find abundant n-alkanes and n-acids are preserved in the Holocene and pre-LGM sediments, allowing for complementary compound-specific δD analyses and identification of organic matter source in addition to chironomid derived temperature records.

  18. Quaternary Charcoal Records from Western North and South America: Linkages to Fire, Climate, and Vegetation Change

    NASA Astrophysics Data System (ADS)

    Whitlock, C.; Marlon, J.; Bartlein, P.

    2006-12-01

    Particulate charcoal preserved in lake sediments has become an important tool for examining the long-term role of fire as an ecosystem process. The record of microscopic charcoal (100 micron diameter or less) offers information on regional burning patterns, whereas macroscopic particles travel less far and are used to infer local fire history. Reconstruction of past fire activity is based on observations of modern charcoal production, transport, and deposition; modeling; and information on current fire regimes. Approaches and statistics used to interpret charcoal records generally focus on (1) quantifying charcoal content in contiguous samples, (2) determining an appropriate age model, (3) converting raw data to charcoal accumulation rates, and (4) extracting fire signal from noise. Detection of signal in charcoal time series is based on knowledge of recent fires provided by dendrochronological and documentary data. Additional paleofire information is obtained from stratigraphic changes in charcoal composition, pollen assemblages adapted to fire, and other paleoenvironmental proxy. Fire-history studies from western North and South America provide examples of Holocene fire-history reconstructions at spatial scales ranging from watershed to regional. Individual sites show dramatic shifts from crown to surface fire regimes associated with major changes in vegetation. Networks of records reveal regional variations in fire activity and vegetation that are attributed to insolation- driven shifts in atmospheric circulation and changes in short-term climate variability. A global database of paleofire records under development offers an opportunity to consider continental-scale fire patterns and their broad consequences for vegetation dynamics, biogeochemical cycling, and atmospheric chemistry.

  19. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    NASA Astrophysics Data System (ADS)

    Lattanzio, A.; Fell, F.; Bennartz, R.; Trigo, I. F.; Schulz, J.

    2015-07-01

    Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA) Climate Data Record (CDR) currently comprising up to 24 years (1982-2006) of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained and Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS) stability requirements for desert reference sites. The limitation in quality due to non removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. A first step consists on the application of a robust and reliable cloud mask taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers some clouds can still remain undetected. A second step relies on a post processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR Release.

  20. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    NASA Astrophysics Data System (ADS)

    Lattanzio, A.; Fell, F.; Bennartz, R.; Trigo, I. F.; Schulz, J.

    2015-10-01

    Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA) Climate Data Record (CDR) currently comprising up to 24 years (1982-2006) of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS) stability requirements for desert reference sites. The limitation in quality due to non-removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. The first step consists of the application of a robust and reliable cloud mask, taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers, some clouds can still remain undetected. A second step relies on a post-processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high-quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR release.

  1. Impact of Holocene climate variability on lacustrine records and human settlements in South Greenland

    NASA Astrophysics Data System (ADS)

    Guillemot, T.; Bichet, V.; Simonneau, A.; Rius, D.; Massa, C.; Gauthier, E.; Richard, H.; Magny, M.

    2015-11-01

    Due to its sensitivity to climate changes, south Greenland is a particularly suitable area to study past global climate changes and their influence on locale Human settlements. A paleohydrological investigation was therefore carried out on two river-fed lakes: Lake Qallimiut and Little Kangerluluup, both located close to the Labrador Sea in the historic farming center of Greenland. Two sediment cores (QAL-2011 and LKG-2011), spanning the last four millennia, were retrieved and showed similar thin laminae, described by high magnetic susceptibility and density, high titanium and TOC / TN atomic ratio, and coarse grain size. They are also characterized either by inverse grading followed by normal grading or by normal grading only and a prevalence of red amorphous particles and lignocellulosic fragments, typical of flood deposits. Flood events showed similar trend in both records: they mainly occurred during cooler and wetter periods characterized by weaker Greenlandic paleo-temperatures, substantial glacier advances, and a high precipitation on the Greenlandic Ice Sheet and North Atlantic ice-rafting events. They can therefore be interpreted as a result of ice and snow-melting episodes. They occurred especially during rapid climate changes (RCC) such as the Middle to Late Holocene transition around 2250 BC, the Sub-boreal/Sub-atlantic transition around 700 BC and the Little Ice Age (LIA) between AD 1300 and AD 1900, separated by cycles of 1500 years and driven by solar forcing. These global RCC revealed by QAL-2011 and LKG-2011 flood events may have influenced Human settlements in south Greenland, especially the paleo-Eskimo cultures and the Norse settlement, and have been mainly responsible for their demise.

  2. Multi-proxies Approach of Climatic Records In Terrestrial Mollusks Shells

    NASA Astrophysics Data System (ADS)

    Labonne, M.; Rousseau, D. D.; Ben Othman, D.; Luck, J. M.; Metref, S.

    Fossil land snails shells constitute a valuable source of information for the study of Quaternary deposits as they are commonly preserved in many regions and notably in loess sequences. The use of stable isotope composition of the carbonate in the shells was previously applied to reconstruct past climate or environnements but the technic was not widely exploited and compared with other proxies from the same sequence. In this study, we have analysed stables isotopes, trace elements and Sr isotopes from both shells of land snails Vertigo modesta and the sediment from the Eustis upper Pleistocene loess sequence (Nebraska, USA). This serie developed during the last glaciation and records the last deglaciation between 18,000 and 12,000 B.P. years. We compare the paleoclimatic information obtained by different proxies, such as mag- netic susceptibility, temperature and moisture estimated by land snails assemblage with geochemical data measured on land snails shells in order to validate the climatic information obtained with this proxy. Our study demonstrates that shell carbonate reflects environmental conditions estimated by other proxies. Carbon and oxygen iso- topes show cyclic variations (millenial cycles) along the profile which correlate with stratigraphic units and could be link with the retreat of the Laurentide ice sheet. Trace element and Sr isotopes in the shells indicate various origins for the eolian dusts in the two main loess units along the sequence.

  3. Multitemporal Snow Cover Mapping in Mountainous Terrain for Landsat Climate Data Record Development

    NASA Technical Reports Server (NTRS)

    Crawford, Christopher J.; Manson, Steven M.; Bauer, Marvin E.; Hall, Dorothy K.

    2013-01-01

    A multitemporal method to map snow cover in mountainous terrain is proposed to guide Landsat climate data record (CDR) development. The Landsat image archive including MSS, TM, and ETM+ imagery was used to construct a prototype Landsat snow cover CDR for the interior northwestern United States. Landsat snow cover CDRs are designed to capture snow-covered area (SCA) variability at discrete bi-monthly intervals that correspond to ground-based snow telemetry (SNOTEL) snow-water-equivalent (SWE) measurements. The June 1 bi-monthly interval was selected for initial CDR development, and was based on peak snowmelt timing for this mountainous region. Fifty-four Landsat images from 1975 to 2011 were preprocessed that included image registration, top-of-the-atmosphere (TOA) reflectance conversion, cloud and shadow masking, and topographic normalization. Snow covered pixels were retrieved using the normalized difference snow index (NDSI) and unsupervised classification, and pixels having greater (less) than 50% snow cover were classified presence (absence). A normalized SCA equation was derived to independently estimate SCA given missing image coverage and cloud-shadow contamination. Relative frequency maps of missing pixels were assembled to assess whether systematic biases were embedded within this Landsat CDR. Our results suggest that it is possible to confidently estimate historical bi-monthly SCA from partially cloudy Landsat images. This multitemporal method is intended to guide Landsat CDR development for freshwaterscarce regions of the western US to monitor climate-driven changes in mountain snowpack extent.

  4. What the Long-Term Sunspot Record Tells Us About Space Climate

    NASA Technical Reports Server (NTRS)

    Hathaway, D. H.

    2004-01-01

    Direct observations of sunspots span the nearly 400 years since the time of Galileo. Dedicated observing programs at several observatories over the last 150 years have provided detailed information not only on the number of sunspots but on their sizes and positions as well. The data acquired by those original observers, and by those who have more recently brought those observations to light, provide important clues about the nature of the solar cycle and its contribution to space climate. The period of the cycle, the equator-ward drift of the active latitudes, the asymmetry between the rise to maximum and the fill to minimum, shifting asymmetries between northern and southern hemisphere activity, the tilt of active regions, and the increasing amplitude of the cycles since the Maunder Minimum are all well established. Other, less well established characteristics such as multi-cycle and short-term periodicities, often depend upon the method of data analysis. The strong correlation between sunspot statistics and other measures of solar activity, coupled with the length of the sunspot record, make these observations extremely valuable for characterizing and understanding space climate.

  5. Verification of a New NOAA/NSIDC Passive Microwave Sea-Ice Concentration Climate Record

    NASA Technical Reports Server (NTRS)

    Meier, Walter N.; Peng, Ge; Scott, Donna J.; Savoie, Matt H.

    2014-01-01

    A new satellite-based passive microwave sea-ice concentration product developed for the National Oceanic and Atmospheric Administration (NOAA)Climate Data Record (CDR) programme is evaluated via comparison with other passive microwave-derived estimates. The new product leverages two well-established concentration algorithms, known as the NASA Team and Bootstrap, both developed at and produced by the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC). The sea ice estimates compare well with similar GSFC products while also fulfilling all NOAA CDR initial operation capability (IOC) requirements, including (1) self describing file format, (2) ISO 19115-2 compliant collection-level metadata,(3) Climate and Forecast (CF) compliant file-level metadata, (4) grid-cell level metadata (data quality fields), (5) fully automated and reproducible processing and (6) open online access to full documentation with version control, including source code and an algorithm theoretical basic document. The primary limitations of the GSFC products are lack of metadata and use of untracked manual corrections to the output fields. Smaller differences occur from minor variations in processing methods by the National Snow and Ice Data Center (for the CDR fields) and NASA (for the GSFC fields). The CDR concentrations do have some differences from the constituent GSFC concentrations, but trends and variability are not substantially different.

  6. Late-Glacial to Early Holocene Climate Changes from a Central Appalachians Pollen and Macrofossil Record

    NASA Technical Reports Server (NTRS)

    Kneller, Margaret; Peteet, Dorothy

    1997-01-01

    A Late-glacial to early Holocene record of pollen, plant macrofossils and charcoal, based on two cores, is presented for Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed upon the overall warming trend from 14,200 to 7,500 C-14 yr B.P. This site shows cold, moist conditions from approximately 14,200 to 12,700 C-14 yr B.P., with warming at 12,730, 11,280 and 10,050 C-14 yr B.P. A decrease in deciduous broad-leaved tree taxa and Pinus strobus (haploxylon) pollen, simultaneous with a re-expansion of Abies denotes a brief, cold reversal from 12,260 to 12,200 C-14 yr B.P. A second cold reversal, inferred from increases in montane conifers, is centered at 7,500 C-14 yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland, and northwestern Europe. Warming at 11,280 C-14 yr B.P. shows the complexity of regional climate responses during the Younger Dryas chronozone.

  7. Insect-damaged fossil leaves record food web response to ancient climate change and extinction.

    PubMed

    Wilf, P

    2008-01-01

    Plants and herbivorous insects have dominated terrestrial ecosystems for over 300 million years. Uniquely in the fossil record, foliage with well-preserved insect damage offers abundant and diverse information both about producers and about ecological and sometimes taxonomic groups of consumers. These data are ideally suited to investigate food web response to environmental perturbations, and they represent an invaluable deep-time complement to neoecological studies of global change. Correlations between feeding diversity and temperature, between herbivory and leaf traits that are modulated by climate, and between insect diversity and plant diversity can all be investigated in deep time. To illustrate, I emphasize recent work on the time interval from the latest Cretaceous through the middle Eocene (67-47 million years ago (Ma)), including two significant events that affected life: the end-Cretaceous mass extinction (65.5 Ma) and its ensuing recovery; and globally warming temperatures across the Paleocene-Eocene boundary (55.8 Ma). Climatic effects predicted from neoecology generally hold true in these deep-time settings. Rising temperature is associated with increased herbivory in multiple studies, a result with major predictive importance for current global warming. Diverse floras are usually associated with diverse insect damage; however, recovery from the end-Cretaceous extinction reveals uncorrelated plant and insect diversity as food webs rebuilt chaotically from a drastically simplified state. Calibration studies from living forests are needed to improve interpretation of the fossil data.

  8. North Pacific Climate Variability in Ice Core Accumulation Records From Eclipse Icefield, Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Yalcin, K.; Wake, C. P.; Kreutz, K. J.

    2005-12-01

    Three annually dated ice cores from Eclipse Icefield, Yukon, Canada provide records of net accumulation spanning the last 100 to 500 years. The ice cores were dated by annual layer counting verified by reference horizons provided by radioactive fallout and volcanic eruptions. Annual layers become progressively thinner with depth in the Eclipse ice cores, requiring reconstruction of original annual layer thicknesses by correcting for ice creep. An empirical approach was used that is based on the observed layer thicknesses from annual layer counting of the Eclipse ice cores. Accumulation records are highly reproducible with 73% of the signal shared between the three cores. The accumulation time-series shows considerable decadal scale variability that can be related to climate regimes that characterize the North Pacific. For example, periods of high accumulation are noted from 1470-1500, 1540-1560, and 1925-1975. Periods of low accumulation are observed between 1500-1540, 1680-1780, and 1875-1925. The strongest multi-year drop in accumulation is seen between 1979 and 1984, although there are isolated years with lower accumulation. This drop in accumulation is possibly related to the 1977 regime shift in the Pacific Decadal Oscillation. However, PDO regime shifts are not always reflected in the accumulation time series, implying a non-linear response or modulation by other modes of climate variability such as ENSO. Its is noteworthy that the Eclipse accumulation time series is out of phase with the accumulation time series from nearby Mount Logan on all time scales for reasons to be investigated.

  9. Chironomid oxygen isotope record of mid- to late Holocene climate evolution from southern Spitsbergen

    NASA Astrophysics Data System (ADS)

    Arppe, Laura; Kurki, Eija; Wooller, Matthew; Luoto, Tomi; Zajączkowski, Marek; Ojala, Antti

    2017-04-01

    The oxygen isotope composition of head capsule chitin of chironomid larvae picked from a sediment core covering the past 5500 years from lake Svartvatnet in southern Spitsbergen was used to reconstruct the isotopic composition of oxygen in lake water (δ18Olw) and local precipitation. Consistent with the gradual cooling of climate over the Neoglacial period, the δ18Olw record displays a gentle decreasing trend over the study period. The Svartvatnet δ18Olwrecord shows a maximum at ca. 1900-1800 cal BP, consistent with the timing of the Roman Warm Period, and three negative excursions increasing in intensity towards the present-day at 3400-3200, 1250-1100 and 350-50 cal BP, which are tentatively linked to multidecadal periods of low solar activity amplified by oceanic and atmospheric feedbacks. The time period of the Little Ice Age shows a two-step decrease in δ18Olwvalues, with a remarkable, 8-9‰ drop at 350-50 cal BP construed to predominantly represent significantly decreased winter temperatures during a period of increased seasonal differences and extended sea ice cover inducing changes in moisture source regions. Similarity of the trends between the δ18Olwrecord and a July-T reconstruction based on chironomid assemblages (Luoto et al., in review) from the same core suggests that air temperature exerts a significant control over the δ18Olwvalues, but the record is most likely influenced by changes in sea ice extent and possibly the seasonal distribution of precipitation. Reference: Luoto TP, Ojala A, Brooks S et al. Synchronized proxy-based temperature reconstructions reveal mid-to late Holocene climate oscillations in High Arctic Svalbard. Journal of Quaternary Science, submitted.

  10. Evaluation of annual resolution coral geochemical records as climate proxies in the Great Barrier Reef of Australia

    NASA Astrophysics Data System (ADS)

    Deng, Wenfeng; Wei, Gangjian; McCulloch, Malcolm; Xie, Luhua; Liu, Ying; Zeng, Ti

    2014-12-01

    Sampling of annually banded massive coral skeletons at annual (or higher) resolutions is increasingly being used to obtain replicate long-term time series of changing seawater conditions. However, few of these studies have compared and calibrated the lower annual resolution records based on coral geochemical tracers with the corresponding instrumental climate records, although some studies have inferred the climatic significance of annual coral series derived from averages of monthly or sub-annual records. Here, we present annual resolution analysis of coral records of elemental and stable isotopic composition that are approximately 70 years long. These records were preserved in two coexisting colonies of Porites sp. from Arlington Reef, on the Great Barrier Reef in Australia, and are used to evaluate the climatic significance of annually resolved coral geochemical proxies. The geochemical records of coral sample "10AR2," with its faster and relatively constant annual growth rate, appear to have been independent of skeletal growth rate and other vital effects. The annual resolution of Sr/Ca and Δδ18O time series was shown to be a good proxy for annual sea surface temperature (SST; r = -0.67, n = 73, p < 0.0000001) and rainfall records ( r = -0.34, n = 67, p < 0.01). However, a slower growing coral sample, "10AR1" showed significantly lower correlations ( r = -0.20, n = 71, p = 0.05 for Sr/Ca and SST; r = -0.19, n = 67, p = 0.06 for Δδ18O and rainfall), indicating its greater susceptibility to biological/metabolic effects. Our results suggest that while annually resolved coral records are potentially a valuable tool for determining, in particular, long timescale climate variability such as Pacific Decadal Oscillation, Interdecadal Pacific Oscillation, and other climatic factors, the selection of the coral sample is important, and replication is essential.

  11. Human and climate impacts on Holocene fire activity recorded in polar and mountain ice cores

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie; Zennaro, Piero; Kirchgeorg, Torben; Li, Quanlian; Wang, Ninglian; Power, Mitchell; Zangrando, Roberta; Gabrielli, Paolo; Thompson, Lonnie; Gambaro, Andrea; Barbante, Carlo

    2014-05-01

    Fire is one of the major influences of biogeochemical change on local to hemispheric scales through emitting greenhouse gases, altering atmospheric chemistry, and changing primary productivity. Levoglucosan (1,6-anhydro-β-D-glucopyranose) is a specific molecular that can only be produced by cellulose burning at temperatures > 300°C, comprises a major component of smoke plumes, and can be transported across > 1000 km distances. Levoglucosan is deposited on and archived in glaciers over glacial interglacial cycles resulting in pyrochemical evidence for exploring interactions between fire, climate and human activity. Ice core records provide records of past biomass burning from regions of the world with limited paleofire data including polar and low-latitude, high-altitude regions. Here, we present Holocene fire activity records from the NEEM, Greenland (77° 27'N; 51° 3'W; 2454 masl), EPICA Dome C, Antarctica (75° 06'S; 123° 21'E; 3233 masl), Kilimanjaro, Tanzania (3° 05'S, 21.2° E, 5893 masl) and the Muztagh, China (87.17° E; 36.35° N; 5780 masl ice cores. The NEEM ice core reflects boreal fire activity from both North American and Eurasian sources. Temperature is the dominant control of NEEM levoglucosan flux over decadal to millennial time scales, while droughts influence fire activity over sub-decadal timescales. Our results demonstrate the prominence of Siberian fire sources during intense multiannual droughts. Unlike the NEEM core, which incorporates the largest land masses in the world as potential fire sources, EPICA Dome C is located far from any possible fire source. However, EPICA Dome C levoglucosan concentrations are consistently above detection limits and demonstrate a substantial 1000-fold increase in fire activity beginning approximately 800 years ago. This significant and sustained increase coincides with Maori arrival and dispersal in New Zealand augmented by later European arrival in Australia. The EPICA Dome C levoglucosan profile is

  12. A mid-european decadal isotope-climate record from 15,500 to 5000 years B.P

    PubMed

    von Grafenstein U; Erlenkeuser; Brauer; Jouzel; Johnsen

    1999-06-04

    Oxygen-isotope ratios of precipitation (delta18OP) inferred from deep-lake ostracods from the Ammersee (southern Germany) provide a climate record with decadal resolution. The record in detail shows many of the rapid climate shifts seen in central Greenland ice cores between 15,000 and 5000 years before the present (B.P.). Negative excursions in the estimated delta18OP from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the North Atlantic. Deviating millennial-scale trends, however, indicate that climate gradients between Europe and Greenland changed systematically, reflecting a gradual rearrangement of North Atlantic circulation during deglaciation.

  13. Climate, productivity, and intermediate water nutrients: new records from bamboo coral Ba/Ca

    NASA Astrophysics Data System (ADS)

    Lavigne, M.; Hill, T. M.; Spero, H. J.; Guilderson, T. P.

    2010-12-01

    A geochemical nutrient proxy from deep-sea corals would provide decadal to centennial scale records of intermediate-water nutrient dynamics. Such records could be used to determine how intermediate water masses (300-2000m) are affected by decadal scale climate change (e.g. Pacific Decadal Oscillation) via carbon cycling, export production, and intermediate water-mass circulation/ventilation. Because seawater barium (BaSW ) has a nutrient-like distribution in the water-column (similar to silicate), Ba/Ca records have been used to trace upwelled nutrient supply in shallow water surface corals isolated from terrestrial barium sources. Here we show the first calibration of a nutrient proxy from skeletal barium preserved in the calcitic internodes of bamboo corals. Our calibration was calculated from a depth transect (500-2000m) of Isidella and Keratoisis corals spanning a silicate and (BaSW ) gradient on the California Margin (Ba/Ca coral (µmol/mol) = 0.117 BaSW (nmol/kg ) + 0.835; R2 = 0.88; n = 29). The strong linear correlation between Ba/Ca coral and BaSW suggests that coral Ba/Ca is a reliable recorder of seawater barium (and, therefore, silicate). We find a distribution coefficient (DBa) for bamboo coral Ba/Ca of 1.3±0.1, similar to that of other corals (surface and deep-sea dwelling) and inorganic calcium carbonate precipitation experiments (DBa = 1.2-1.5). This implies that, as true for other carbonates, Ba incorporation is primarily driven by ionic substitution and holds promise as a globally applicable nutrient proxy in bamboo corals. High-resolution Ba/Ca timeseries records sampled via LA-ICP-MS in two co-located California Margin corals (Pioneer Seamount; 830m; 37°22’27”N) co-vary with ~decadal-scale variations in silicate and nitrate measured at 500m depth (CalCOFI line 80 sta. 60; 34°8’60”N). This suggests that high-resolution records of bamboo coral Ba/Ca can be used to reconstruct broad changes in intermediate water nutrients driven by

  14. A compilation of Western European terrestrial records 60-8 ka BP: towards an understanding of latitudinal climatic gradients

    NASA Astrophysics Data System (ADS)

    Moreno, Ana; Svensson, Anders; Brooks, Stephen J.; Connor, Simon; Engels, Stefan; Fletcher, William; Genty, Dominique; Heiri, Oliver; Labuhn, Inga; Perşoiu, Aurel; Peyron, Odile; Sadori, Laura; Valero-Garcés, Blas; Wulf, Sabine; Zanchetta, Giovanni

    2014-12-01

    Terrestrial records of past climatic conditions, such as lake sediments and speleothems, provide data of great importance for understanding environmental changes. However, unlike marine and ice core records, terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non-specialist. As a consequence, many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations, comparisons, or modelling exercises. Here we present a compilation of Western European terrestrial palaeo-records covering, entirely or partially, the 60-8-ka INTIMATE time period. The compilation contains 56 natural archives, including lake records, speleothems, ice cores, and terrestrial proxies in marine records. The compilation is limited to include records of high temporal resolution and/or records that provide climate proxies or quantitative reconstructions of environmental parameters, such as temperature or precipitation, and that are of relevance and interest to a broader community. We briefly review the different types of terrestrial archives, their respective proxies, their interpretation and their application for palaeoclimatic reconstructions. We also discuss the importance of independent chronologies and the issue of record synchronization. The aim of this exercise is to provide the wider palaeo-community with a consistent compilation of high-quality terrestrial records, to facilitate model-data comparisons, and to identify key areas of interest for future investigations. We use the compilation to investigate Western European latitudinal climate gradients during the deglacial period and, despite of poorly constrained chronologies for the older records, we summarize the main results obtained from NW and SW European terrestrial records before the LGM.

  15. It's getting hot here - The Middle Eocene Climatic Optimum (MECO) in a terrestrial sedimentary record

    NASA Astrophysics Data System (ADS)

    Methner, K.; Wacker, U.; Fiebig, J.; Chamberlain, C.; Mulch, A.

    2013-12-01

    The Middle Eocene Climatic Optimum (MECO) represents an enigmatic global warming event during Cenozoic cooling that has been discovered in ocean drill cores from varying latitudes and oceanic basins. It is marked by a rapid negative shift in oxygen isotope ratios of foraminiferal calcite and thought to reflect the combined effects of freshwater input as well as an increase in sea surface and bottom water temperatures by up to 5 to 6 °C. MECO is therefore a temperature extreme during already warm Eocene climate. This makes the MECO to one of the hottest phases during Earth's climate history, yet it is largely unknown how MECO affected temperatures in the continental interiors as well as their rainfall and vegetation dynamics. Here, we present stable isotope (δ18O, δ13C) and clumped isotope temperature (Δ47) records from a middle Eocene (ca. 42.0 to 40.0 Ma) mammal fossil locality in southwestern Montana, USA. The sampled section (Upper Dell Beds, Sage Creek Basin) comprises about 60 m of stacked paleosols that were correlated to Chron C18r by paleomagnetics and biostratigraphy. δ18O values of pedogenic carbonate range from -12 to -18 per mil (SMOW) and to first-order follows the marine δ18O pattern. Low δ18O values coincide with peak-MECO conditions and show a relatively rapid ca. 5°C increase in soil temperatures reaching peak temperatures of ~27°C at the climax of MECO. Immediately after the MECO event temperatures drop rapidly by about 8°C. To our knowledge this is the first terrestrial MECO paleotemperature record that further provides insight into the precipitation dynamics deep within the North American continent during this early Cenozoic hyperthermal. Paleosol Δ47 temperatures are highly reproducible within and across individual soil sequences and provide a realistic temperature estimate prior, during and after the MECO event. The combined δ18O and Δ47 data therefore provide important insight into the isotopic evolution of precipitation and mean

  16. Evaluation Of The MODIS-VIIRS Land Surface Reflectance Fundamental Climate Data Record.

    NASA Astrophysics Data System (ADS)

    Roger, J. C.; Vermote, E.; Skakun, S.; Murphy, E.; Holben, B. N.; Justice, C. O.

    2016-12-01

    The land surface reflectance is a fundamental climate data record at the basis of the derivation of other climate data records (Albedo, LAI/Fpar, Vegetation indices) and has been recognized as a key parameter in the understanding of the land-surface-climate processes. Here, we present the validation of the Land surface reflectance used for MODIS and VIIRS data. This methodology uses the 6SV Code and data from the AERONET network. The first part was to define a protocol to use the AERONET data. To correctly take into account the aerosol model, we used the aerosol microphysical properties provided by the AERONET network including size-distribution (%Cf, %Cc, rf, rc, σr, σc), complex refractive indices and sphericity. Over the 670 available AERONET sites, we selected 230 sites with sufficient data. To be useful for validation, the aerosol model should be readily available anytime, which is rarely the case. We then used regressions for each microphysical parameter using the aerosol optical thickness at 440nm and the Angström coefficient as parameters. Comparisons with the AERONET dataset give good APU (Accuracy-Precision-Uncertainties) for each parameter. The second part of the study relies on the theoretical land surface retrieval. We generated TOA synthetic data using aerosol models from AERONET and determined APU on the surface reflectance retrieval while applying the MODIS and VIRRS Atmospheric correction software. Over 250 AERONET sites, the global uncertainties are for MODIS band 1 (red) is always lower than 0.0015 (when surface reflectance is > 0.04). This very good result shows the validity of our reference. Then, we used this reference for validating the MODIS and VIIRS surface reflectance products. The overall accuracy clearly reaches specifications. Finally, we will present an error budget of the surface reflectance retrieval. Indeed, to better understand how to improve the methodology, we defined an exhaustive error budget. We included all inputs i

  17. High-Resolution Pollen Record of Deglacial Climate Variability in Central Florida

    NASA Astrophysics Data System (ADS)

    Willard, D. A.; Bernhardt, C. E.; Edgar, T.

    2004-12-01

    Pollen evidence from lacustrine sediments in Tampa Bay, Florida document considerable climatic variability superimposed on deglacial warming in the subtropics. Nine radiocarbon dates on well-preserved mollusk shells provide a reliable chronology of continuous sedimentation from 20 ka to 11.5 ka; examination of pollen assemblages from 2 cm increments within the lacustrine unit provide temporal resolution averaging one sample every 45 years. During the glacial maximum, much drier and cooler than modern conditions are indicated by pollen assemblages enriched in Chenopodiaceae, Carya, Poaceae and Ambrosia. Increased abundance of Pinus pollen between 17.4 ka and 15 ka indicates the existence of warmer, wetter conditions in the interval including Heinrich Event 1. After a reversion to drier, cooler conditions at about 15 ka, Pinus pollen abundance increased again at 14 ka. Combined with the near loss of Carya pollen, these data suggest attainment of nearly modern climatic conditions during the Bolling-Allerod (14-13 ka). However, variability within the Bolling-Allerod is documented by shifts to deglacial-equivalent vegetation during the Older Dryas (13.4-13.6 ka). The Younger Dryas (12.9-11.6 ka) is characterized by two distinct phases: from 12.9-11.9 ka, the increased abundance of Chenopodiaceae and Quercus mark drier, possibly cooler conditions comparable to those of the deglacial (17.4 - 14 ka). From 11.9-11.5 ka, strong dominance of herbaceous Chenopodiaceae is similar to full-glacial conditions, indicating much drier, possibly cooler conditions. Comparison of these paleoclimatic patterns with marine records from Orca Basin in the Gulf of Mexico indicate close temporal correspondence in warming of atmospheric and sea-surface temperatures. Pollen evidence also suggests that significant warming began around 17.4 ka, before the onset of Heinrich Event 1, as has been documented at other sites in the North Atlantic Ocean and Europe. This record of deglacial atmospheric

  18. A new long sediment record from Padul, southern Spain records orbital- and suborbital-scale environmental and climate changes during the middle and late Quaternary

    NASA Astrophysics Data System (ADS)

    Jimenez-Moreno, Gonzalo; Camuera, Jon; Ramos-Roman, Maria J.; Toney, Jaime L.; Anderson, R. Scott; Jimenez-Espejo, Francisco J.; Kaufman, Darrell; Bright, Jordon; Webster, Cole

    2017-04-01

    Long paleoenvironmental records are necessary in order to understand recurrent climatic or paleoenvironmental changes occurring with a certain periodicity (i.e., glacial-interglacial cycles). In this respect, the Padul peat bog has one of the best available records of Pleistocene sediments in semiarid Southern Europe. The sedimentary sequence is more than 100 m thick and has been used to study palaeoenvironmental change for the past ca. 1 Ma. Since the 1960s several cores have already been taken from this basin showing oscillations in many proxies (pollen, organic geochemistry and sedimentation) related with paleoclimatic and paleohydrological changes. However, a more detailed and higher resolution study, using new dating and analytical techniques (AMS 14C, AAR, continuous XRF-scanning, high-resolution pollen analysis and geochemistry), needs to be done in such an interesting site. Here we present preliminary paleoenvironmental data from a new sediment core, Padul-15-05, which shows significant changes in the environment and lake sedimentation, probably related with glacial-interglacial climate dynamics during the past ca. 300,000 years. These data confirm that orbital- as well as suborbital-scale variability (i.e., Heinrich, D-O events) are recorded in the studied core. This unique record thus has very high potential for paleoenvironmental and paleoclimatic reconstructions for, at least, the two last climatic cycles in this semiarid Mediterranean area.

  19. An Assessment of IPCC 20th Century Climate Simulations Using the 15-year Sea Level Record from Altimetry

    NASA Astrophysics Data System (ADS)

    Leuliette, E.; Nerem, S.; Jakub, T.

    2006-07-01

    Recen tly, multiple ensemble climate simulations h ave been produced for th e forthco ming Fourth A ssessment Report of the Intergovernmental Panel on Climate Change (IPCC). N early two dozen coupled ocean- atmo sphere models have contr ibuted output for a variety of climate scen arios. One scenar io, the climate of the 20th century exper imen t (20C3 M), produces model output that can be comp ared to th e long record of sea level provided by altimetry . Generally , the output from the 20C3M runs is used to initialize simulations of future climate scenar ios. Hence, v alidation of the 20 C3 M experiment resu lts is crucial to the goals of th e IPCC. We present compar isons of global mean sea level (G MSL) , global mean steric sea level change, and regional patterns of sea lev el chang e from these models to r esults from altimetry, tide gauge measurements, and reconstructions.

  20. Fifty-Year Record of Glacier Change Reveals Shifting Climate in the Pacific Northwest and Alaska, USA

    USGS Publications Warehouse

    ,

    2009-01-01

    Fifty years of U.S. Geological Survey (USGS) research on glacier change shows recent dramatic shrinkage of glaciers in three climatic regions of the United States. These long periods of record provide clues to the climate shifts that may be driving glacier change. The USGS Benchmark Glacier Program began in 1957 as a result of research efforts during the International Geophysical Year (Meier and others, 1971). Annual data collection occurs at three glaciers that represent three climatic regions in the United States: South Cascade Glacier in the Cascade Mountains of Washington State; Wolverine Glacier on the Kenai Peninsula near Anchorage, Alaska; and Gulkana Glacier in the interior of Alaska (fig. 1).

  1. A 50-ky record of climate, ecosystem, and erosion rate change in the Oregon Coast Range

    NASA Astrophysics Data System (ADS)

    Marshall, J. A.; Roering, J. J.; Granger, D. E.; Gavin, D. G.

    2013-12-01

    In unglaciated landscapes, quantifying landscape response to millennial-scale climate fluctuations is often restricted to temporally and spatially limited archives such as terrace deposits. In addition, mechanistic explanations for landscape response to climate change are lacking. Specifically it is unclear how climate controls the vigor and rate of soil production and transport, as processes in modern ecosystems (e.g. bioturbation such as tree throw) tend to bias our interpretations of landscape evolution. Here, we present results coupling a 50-ky paleo-environmental record with cosmogenic 10Be-derived paleo-erosion rates spanning non-glacial, glacial, and inter-glacial intervals from a 63m sediment archive in the Oregon Coast Range (OCR). At Little Lake, our landslide-dammed lake study site, we refined previous records of paleo-climate to better constrain paleo-temperature and thus the likelihood of frost-driven vs. biotic erosional processes prior to the Holocene. The presence of Picea sitchensis (Sitka spruce) and Abies lasiocarpa (subalpine fir) in the core during the Last Glacial Maximum (LGM) imply mean annual temperatures of ~ 1 °C and January mean temperatures of ~ -7 °C. This contrasts sharply with modern temperatures of 11 °C and 5 °C respectively. Using 14C (n=21) and OSL (n=3), we constructed a chronology for our sediment archives that spans the non-glacial (50-26 ka) and glacial intervals (26- 16 ka) and the late Holocene (3 ka to present). Our depth-age model shows that sediment accumulation rates increased 5x from the non-glacial to the glacial interval, coincident with a transition from finely laminated clays and sands to coarse blue-grey sands. We extracted 25 samples for 10Be analysis from the core over an average interval of 1500 years. Preliminary 10Be-derived erosion rates show increasing erosion rates from 0.06 × 0.02 mm/yr (48 ka) to 0.18 × 0.02 mm/yr (28 ka) during the non-glacial interval as temperatures cooled and the forest

  2. Major Holocene Climatic Cycle Recorded in Snow Stratigraphy of the East Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Wise, D. U.

    2011-12-01

    Satellite images show near-surface snows of the East Antarctic Plateau can be divided into four previously unrecognized stratigraphic units, each separated by unconformities. The sequence records an apparent cycle of hot to cold conditions followed by slow return to the modern warm climate. It began with megadune deposition during hot conditions with strong winds and heavy snowfalls from local sources in open marine waters, most likely during the Holocene hypsothermal climatic excursion. Megadunes are unique to this plateau as upwind-migrating, upper flow regime features, characterized by alternating glazed and unglazed snow pseudo-beds with 2 - 4 km wavelength but only 1 - 5 m amplitude. They form a zebra-striped pattern with exposure across ~ 106 km2 or ~ 15 - 20% of the plateau surface. As the hypsothermal excursion ended, wind velocity decreased, snow supplies declined, Froude numbers approached unity, and deposition shifted abruptly from upper flow regime megadunes into lower flow regime downwind-migrating, ephemeral, high topographic relief dunes, a type previously undescribed and like megadunes unique to the plateau. Soon these were replaced by ordinary, downwind migrating, parabolic dunes to complete a trio of dune types comprising the basal or unit #1 member of the stratigraphic sequence. All were abandoned with development of unit #2, characterized by pervasive snow-starvation and overlapping "tiger claw" wind lineations that sweep downslope for distances of 1000 to 1500 km. These two units record the first part of the cycle, a long-term monotonic decrease in snow availability, best explained by a steadily cooling climate that expanded ice cover across marine moisture sources. Ultimately much of the adjacent Southern Ocean froze to allow both units to develop a strongly lineated, wind-burned, recrystallized surface. When climates finally began to warm and marine ice cover began to recede, unit #3's snows began to expand with basal unconformity across most

  3. Obliquity-paced climate change recorded in Antarctic debris-covered glaciers

    PubMed Central

    Mackay, Sean L.; Marchant, David R.

    2017-01-01

    The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change. PMID:28186094

  4. Obliquity-paced climate change recorded in Antarctic debris-covered glaciers

    NASA Astrophysics Data System (ADS)

    Mackay, Sean L.; Marchant, David R.

    2017-02-01

    The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ~220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change.

  5. Obliquity-paced climate change recorded in Antarctic debris-covered glaciers.

    PubMed

    Mackay, Sean L; Marchant, David R

    2017-02-10

    The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change.

  6. Earth Science and Climate Data Records at the National Oceanographic Data Center

    NASA Astrophysics Data System (ADS)

    Casey, K. S.; Levitus, S.; Brandon, T. B.

    2008-12-01

    The NOAA National Oceanographic Data Center (NODC) serves as the nation's archive and long-term stewardship facility for a wide range of ocean observations. For centuries, these observations came primarily from ships and other platforms in the water, and in recent decades satellite-based sensors have begun delivering critical data as well. NODC provides to the community Earth Science Data Records (ESDRs) from both in situ and space-based platforms, with a particular emphasis on Climate Data Records (CDRs) geared toward understanding long-term variability in the ocean. Two of NODC's major CDR efforts will be presented. The first of these is the World Ocean Database (WOD) project, which focuses on the collection, quality control, and provision of ocean parameters throughout the depth of the world ocean using in situ profile measurements. The second effort relies on satellite-based observations of sea surface temperature (SST) and includes the Pathfinder and Group for High Resolution SST (GHRSST) programs. Despite having emerged from what are traditionally considered very different parts of the oceanography community, both WOD and Pathfinder/GHRSST share a surprising degree of commonality in their approaches to generating and reprocessing products, obtaining community consensus on their approaches, and encouraging wide usage of the resulting CDRs. These efforts will be discussed and compared with a focus on application of the concepts not only across ocean disciplines but to the generation of other ESDRs as well.

  7. A new meteorological record for Cádiz (Spain) 1806-1852: Implications for climatic reconstructions

    NASA Astrophysics Data System (ADS)

    Gallego, David; Garcia-Herrera, Ricardo; Calvo, Natalia; Ribera, Pedro

    2007-06-01

    A new documentary source of data for wind, atmospheric pressure and air temperature for the city of Cádiz (southern Spain) has been abstracted, analyzed and compared with present-day data. Wind records cover the period 1806-1852 with three observations per day. Instrumental pressure and temperature cover the period 1825-1852. While the historical pressure series shows average values very close to that found for the period 1971-2000, temperature shows a large asymmetric seasonal warming, with increments in the order of 2°C for the winter months and almost no change for summer. Wind measurements have been transformed into their numerical equivalents and then compared with present-day values. The analysis shows that the numerical estimation of ancient wind forces observed at Cádiz, while providing a robust climatic signal, has a strong bias to larger values than their instrumental equivalents. Despite the uncertainties involved in the interpretation of early wind series, this effect could be related to the recording of "average wind gusts" rather than average winds as measured by today's anemometers. In consequence, wind climatologies based on historical data, which recently are becoming available to the scientific community, should be used carefully.

  8. Late Middle Pleistocene climate in southwestern China: inferences from the stratigraphic record of Panxian Dadong Cave, Guizhou

    NASA Astrophysics Data System (ADS)

    Karkanas, Panagiotis; Schepartz, Lynne A.; Miller-Antonio, Sari; Wang, Wei; Huang, Weiwen

    2008-08-01

    Panxian Dadong Cave, situated in the subtropical zone of southwestern China, preserves a fan-like sedimentary sequence close to its entrance that spans the period between MIS 8 and 5 (300-130 ka). The frequent alternation of flowstone formation, cementation, clastic deposition, and frost activity in the depositional sequence makes it ideal for reconstructing the environmental conditions prevailing during the later Middle Pleistocene on the Guizhou Plateau. Macroscopic and microscopic sedimentary analyses determine that clastic deposits were entering the cave in the form of intermittent cohesive debris flows and sheetflows during cold and relatively dry climatic conditions when vegetation cover was reduced. Interlayered impure flowstones were forming during wetter phases but still under glacial conditions. Seasonally freezing temperatures are deduced from the frequent occurrence of cycles of well-developed freeze-thaw features affecting both the clastic parts of the sequence and the flowstones as they were deposited. The described depositional processes were responsible for lateral redistribution on the fan surface of bone remains and lithic artifacts that were accumulating on the surface as a result of hominid activities. During the intervening interglacial stages (MIS 7 and possibly MIS 5) clastic deposition was considerably reduced and only thin flowstone caps and weathering manganese-iron crusts were forming. It is suggested that precipitation was much higher during glacial intervals than interglacials under a predominantly cold climate. Dadong Cave provides a good example of very cold and wet climatic conditions during glacials in the subtropics of East Asia.

  9. Multiple Speleothem Record of Orbital to Millennial-scale Climate Variability During MIS 21 to MIS 26

    NASA Astrophysics Data System (ADS)

    Hellstrom, J. C.; Bajo, P.; Drysdale, R.; Woodhead, J. D.; Ferretti, P.; Voelker, A. H. L.; Wolff, E. W.; Zanchetta, G.; Rodrigues, T.; Frisia, S.; Spoetl, C.; Fallick, A.

    2016-12-01

    Despite increasing interest in the study of orbital to millenial-scale climate variability during the Middle Pleistocene Transition our understanding of climate forcings as well as teleconnections is restricted in part by the lack of radiometrically-dated records. Furthermore, almost all high-resolution records have been recovered from marine setttings while continental archives remain highly under-represented. Here we present a multiple U-Pb radiometrically dated speleothem δ18O and δ13C record from Corchia Cave (Italy) which spans the Marine Isotope Stage (MIS) 21 to MIS 26 time interval. The record is based on four stalagmites and one subaqueous core. More than 100 U-Pb analyses secured a robust chronology and all climate events of interest were dated with a precision of 5ka or better. The speleothem chronology was transposed on to the marine benthic records through matching the speleothem δ18O and the SST records from the North Atlantic. Our results reveal that Terminations XII and X are separated by two obliquity cycles, and that Marine Isotope Stages 25 to 22 are not part of a 100-kyr cycle as previously thought. Furthermore, our time series reveal that precession also played an important role with each Termination occurring when summer insolation in either the Northern or Southern Hemisphere was high. This rules out the importance of an exclusively Northern Hemisphere summer insolation maximum in triggering the timing of these terminations and implicates obliquity as the major forcing parameter. Superimposed on the glacial-interglacial climate variability in our record we also recognise four interstadial periods during MIS 21. These millenial-scale events are in agreement with deep sea records distributed across the North Atlantic. The interstadials are recorded in both speleothem δ18O and δ13C proxies and are interpreted as reflective of a decrease in rainfall amount and temperature at the Corchia cave site probably as a response to precession

  10. Extending MODIS Cloud Top and Infrared Phase Climate Records with VIIRS and CrIS

    NASA Astrophysics Data System (ADS)

    Heidinger, A. K.; Platnick, S. E.; Ackerman, S. A.; Holz, R.; Meyer, K.; Frey, R.; Wind, G.; Li, Y.; Botambekov, D.

    2015-12-01

    The MODIS imagers on the NASA EOS Terra and Aqua satellites have generated accurate and well-used cloud climate data records for 15 years. Both missions are expected to continue until the end of this decade and perhaps beyond. The Visible and Infrared Imaging Radiometer Suite (VIIRS) imagers on the Suomi-NPP (SNPP) mission (launched in October 2011) and future NOAA Joint Polar Satellite System (JPSS) platforms are the successors for imager-based cloud climate records from polar orbiting satellites after MODIS. To ensure product continuity across a broad suite of EOS products, NASA has funded a SNPP science team to develop EOS-like algorithms that can be use with SNPP and JPSS observations, including two teams to work on cloud products. Cloud data record continuity between MODIS and VIIRS is particularly challenging due to the lack of VIIRS CO2-slicing channels, which reduces information content for cloud detection and cloud-top property products, as well as down-stream cloud optical products that rely on both. Here we report on our approach to providing continuity specifically for the MODIS/VIIRS cloud-top and infrared-derived thermodynamic phase products by combining elements of the NASA MODIS science team (MOD) and the NOAA Algorithm Working Group (AWG) algorithms. The combined approach is referred to as the MODAWG processing package. In collaboration with the NASA Atmospheric SIPS located at the University of Wisconsin Space Science and Engineering Center, the MODAWG code has been exercised on one year of SNPP VIIRS data. In addition to cloud-top and phase, MODAWG provides a full suite of cloud products that are physically consistent with MODIS and have a similar data format. Further, the SIPS has developed tools to allow use of Cross-track Infrared Sounder (CrIS) observations in the MODAWG processing that can ameliorate the loss of the CO2 absorption channels on VIIRS. Examples will be given that demonstrate the positive impact that the CrIS data can provide

  11. Teaching climate change: A 16-year record of introducing undergraduates to the fundamentals of the climate system and its complexities

    NASA Astrophysics Data System (ADS)

    Winckler, G.; Pfirman, S. L.; Hays, J. D.; Schlosser, P.; Ting, M.

    2011-12-01

    Responding to climate change challenges in the near and far future, will require a wide range of knowledge, skills and a sense of the complexities involved. Since 1995, Columbia University and Barnard College have offered an undergraduate class that strives to provide students with some of these skills. The 'Climate System' course is a component of the three-part 'Earth Environmental Systems' series and provides the fundamentals needed for understanding the Earth's climate system and its variability. Being designed both for science majors and non-science majors, the emphasis of the course is on basic physical explanations, rather than mathematical derivations of the laws that govern the climate system. The course includes lectures, labs and discussion. Laboratory exercises primarily explore the climate system using global datasets, augmented by hands-on activities. Course materials are available for public use at http://eesc.columbia.edu/courses/ees/climate/camel_modules/ and http://ncseonline.org/climate/cms.cfm?id=3783. In this presentation we discuss the experiences, challenges and future demands of conveying the science of the Earth's Climate System and the risks facing the planet to a wide spectrum of undergraduate students, many of them without a background in the sciences. Using evaluation data we reflect how the course, the students, and the faculty have evolved over the past 16 years as the earth warmed, pressures for adaptation planning and mitigation measures increased, and public discourse became increasingly polarized.

  12. Decadal and Lower Frequency South Pacific Climate Variability Since 1619 AD from Replicated Coral Records

    NASA Astrophysics Data System (ADS)

    Linsley, B. K.; Wellington, G. M.; Kaplan, A.; Demenocal, P. B.

    2004-12-01

    A notable aspect of multi-century oxygen isotope (\\delta18O) time-series generated from modern Pacific Porites corals in the convergence zone is the presence of a trend component of progressively lower \\delta18O in the top (younger) sections of most published \\delta18O series. The climatic significance of this trend has remained controversial in part due to the paucity of multi-century long coral records. Here we present sub-annually resolved and replicated Porites \\delta18O records from Fiji (17S, 179E) (1619-2001AD, replicated from 1780) and Rarotonga (21.5S, 160W) (1726-1997AD; replicated from 1874) in the southwestern Pacific to evaluate the significance of the \\delta18O trend in this region. As part of this study we also analyzed bulk skeletal Sr/Ca from each of the 5 coral cores (2 subannual, 3 annually averaged). The coral \\delta18O series from Fiji and Rarotonga document site reproducible trends (similar timing within each site, and total magnitudes of 0.30 to 0.35 per mil since 1850AD) towards progressively lower and unprecedented \\delta18O in the late 20th century. However, the Sr/Ca records from the same cores do not replicate completely before 1950AD, indicating that at these sites, and in some corals, Porites bulk skeletal Sr/Ca is not strictly a function of SST or external-to-the-coral environmental variability. For skeletal \\delta18O, the overall reproducibility of the \\delta18O trend in different age corals at each site, supports a locally consistent, primarily environmental origin for this mode of \\delta18O variability. Comparison of the \\delta18O trend modes at Fiji and Rarotonga to each other and to instrumental SST and precipitation data suggests that the coral \\delta18O trend at each site is due to regionally variable but progressive warming and salinity reduction. If this interpretation is correct, the second half of the 20th century was the warmest and least saline at both sites since the early 1600s. Since Fiji and Rarotonga are

  13. Blue Hill Observatory Sunshine - Assessment of Climate Signals in the Longest Continuous Meteorological Record in North America

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Finocchio, P.; Melaas, E. K.; Iacono, M. J.

    2014-12-01

    The Blue Hill Meteorological Observatory occupies a unique place in the history of the American Meteorological Society and the development of atmospheric science. Through its 129-year history, the Observatory has been operated by founder Abbott Lawrence Rotch (1861-1912), Harvard University, and the National Weather Service, and it is presently run by the non-profit Blue Hill Observatory Science Center. While daily temperature and precipitation records are available through the National Climatic Data Center, they do not include the full record of sunshine duration data that were measured using a Campbell-Stokes sunshine recorder. We have recently digitized the Observatory's original daily sunshine archives, and now present the first full collection and analysis of sunshine records extending from 1889 to the present. This data set is unique and salient to modern climate research because the collection represents the earliest and longest continuous measurements of insolation outside of Western Europe. Together the record provides an unprecedented glimpse into regional climate features, as well as important links between global phenomena and regional climate. Analysis reveals long-term fluctuations of cloud-cover and solar radiation, including signals of regional industrialization, global-dimming, volcanic eruptions, the 11-Year Solar Cycle, and the El Niño Southern Oscillation. Shorter period fluctuations include evidence of an intricate annual pattern of sunshine duration and correlations with the Arctic Oscillation, North Atlantic Oscillation, and galactic cosmic rays.

  14. Late Holocene Lacustrine Records of Climate and Vegetation Change From Southern Patagonia, Chile

    NASA Astrophysics Data System (ADS)

    Moy, C. M.; Francois, J.; Moreno, P.; Villa Martinez, R.; Dunbar, R. B.

    2004-12-01

    The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere, having a major impact on the climate of Chile and hydrographic conditions in the Southern Ocean. The latitudinal position and strength of the westerlies directly influences the amount and isotopic composition of precipitation that falls in southern Chile. Although instrumental records provide information on how the westerlies have varied over the recent past there is still an incomplete understanding of how the strength and latitudinal position of the southern westerlies have changed during the Holocene and how the wind field has varied at millennial to sub-decadal timescales. In this study we relate changes in the westerly winds to changes in water balance as recorded in closed-basin lakes. Sediment cores were obtained from Laguna Guanacos in Parque Nacional Torres del Paine (51° S, 72° W) during the austral summer of 2004 and sampled at 1-2cm intervals for pollen, charcoal, and stable isotope analysis. Laguna Guanacos is a small closed-basin lake situated in the core of westerly wind belt and is therefore sensitive to fluctuations in the strength and position of the westerlies. The sediment cores obtained from the lake reveal high concentrations of organic mater ( ˜20%) and biogenic carbonate, which is rare in Chilean Patagonia. AMS radiocarbon dates on the organic and carbonate fractions indicate that the record spans the last ˜14,000 calendar years and modern dates from core tops suggest little influence by old or dead carbon sources. Pollen analysis on the late Holocene portion of the record reveals a significant expansion of the Nothofagus forest since ˜3500 cal yr BP, suggesting an overall increase in precipitation during this interval. Millennial- and centennial-scale fluctuations in bulk carbonate content and forest and steppe pollen are superimposed upon this pattern, providing a view of a highly dynamic westerly wind regime and forest

  15. Can an Earth System Model Reproduce the Palaeo-Climate Proxy Record in eastern Africa during the Eemian?

    NASA Astrophysics Data System (ADS)

    Anker Pedersen, Rasmus; Thejll, Peter; Mottram, Ruth; Davies, Sarah; Lamb, Henry

    2016-04-01

    The climate of the Eemian period is characterized by higher than present day temperatures at the poles and a substantially increased sea level compared to the present day, which has led to its use as a proxy for future climate change scenarios. Regionally, the Eemian climate in eastern Africa has been defined by a number of different proxies. Evidence from the region's lakes indicate generally wetter conditions. At Lake Tana, Ethiopia, there is evidence that this wetter period is punctuated by variable precipitation. These changes have been related to shifts in the position of the ITCZ caused by warmer North Atlantic SSTs, but they may also be related to the steep insolation gradient through the Eemian period that gave greater warming at the high latitudes and cooling in the tropics and low latitudes. The EC-Earth fully coupled earth system model includes ocean, atmosphere, sea ice and land surface modules and has been run for a time-slice within the Eemian period at a resolution of 1 degree in a number of different experimental configurations to determine the relative importance of internal (SST, sea ice) and external (orbital driven insolation forcing) climate drivers on the climate of the Eemian in eastern Africa. Here, we present initial results that show the EC-Earth GCM can replicate the proxy record for the Eemian period though substantial uncertainties related especially to the resolution of the proxy record remains. The model simulations suggest that insolation driven cooling in combination with changes in SSTs can explain climate changes recorded in eastern Africa. This gives us further confidence in both future projections of climate change and the regional downscaling proposed in the DACEA project to understand the hydrology of the Nile basin and eastern African climate.

  16. Annually resolved lake and shallow marine sediment records of global climate change of the past 16,000 years

    NASA Astrophysics Data System (ADS)

    Haug, G. H.; Brauer, A.; Yancheva, G.; Dulski, P.; Negendank, J. F.; Peterson, L. C.; Sigman, D. M.

    2007-12-01

    In the sediments of lake Huguang Maar in coastal southeast China, the titanium content and redox-sensitive magnetic properties record the strength of winter monsoon winds at subdecadal to annual resolution over the last 16 thousand years. The record indicates a stronger winter monsoon prior to the Bølling-Allerød warming, during the Younger Dryas, and during the middle and late Holocene, when cave stalagmite oxygen isotope data indicate a weaker summer monsoon. The anti-correlation between winter and summer monsoon strength is best explained by migrations in the ITCZ that occurred simultaneously in central America and Africa. Drought associated with southward ITCZ migration may have played a role in the termination of several Chinese dynasties. A remarkable similarity of ITCZ migration in east Asia and the Americas from 700 to 900 AD raises the possibility that the coincident declines of the important Tang Dynasty in China and the Classic Maya in Central America were catalyzed by the same ITCZ migrations. The mechanisms behind these decadal-scale ITCZ-monsoon swings can be further exoplored at major climate transitions such as the onset of Younger Dryas cooling at ~12.7 ka, one of the most abrupt climate changes observed in ice core, lake and marine records in the North Atlantic realm and much of the Northern Hemisphere. Annually laminated lake sediments ideally record the dynamics of abrupt climate changes since seasonal deposition immediately responds to climate and varve counts accurately estimate the time of change. We report new sub-annual geochemical and varve microfacies data from a lake in Western Germany, which provides one of the best-dated records currently available for this climate transition, which we compare to the Cariaco Basin and Lake Huguang Maar records. The Lake Meerfelder Maar record indicates an abrupt increase in storminess, occurring from one year to the next at 12,678 ka BP, coincident with other observed climate changes in the region

  17. An 18 million year record of vegetation and climate change in northwestern Canada and Alaska: Tectonic and global climatic correlates

    USGS Publications Warehouse

    White, J.M.; Ager, T.A.; Adam, D.P.; Leopold, E.B.; Liu, Gaisheng; Jette, H.; Schweger, C.E.

    1997-01-01

    We reconstruct long-term vegetation/paleoclimatic trends, spanning the last 18 million years, in Alaska. Yukon and far western Northwest Territories. Twenty-one average percentage spectra for pollen and spores are assembled from eight surface/subsurface sections. The sections are dated independently or by correlation. Pollen and spore ratios indicate the direction of change in vegetation and climatic parameters growing season temperature (T(est)), tree canopy density (C(est)) and paludification at study sites (P(est)). A global warm peak ca. 15 Ma is shown by the abundance of thermophilous taxa, including Fagus and Quercus. A temperature decline immediately following 15 Ma parallels climatic reconstructions based on marine oxygen isotopes. Subsequent declines correlate to the Messinian event and the onset of late Pliocene Pleistocene glaciation. After 7 Ma herbs and shrubs become more important elements of the palynological assemblages, suggesting a more continental, colder/drier climate. However, a late Pliocene warm interval is evident. Vegetation/climatic changes during the early to late Miocene show synchrony with, and are most economically attributable to, global events. After 7 Ma, vegetation/climate change is attributed primarily to latest Miocene-to-Pleistocene uplift of the Alaska Range and St. Elias Mrs. The continuing influence of global climatic patterns is shown in the late Pliocene warm interval, despite uplift to the south. The opening of the Bering Strait ca. 3 Ma may have moderated the climate in the study area.

  18. Radiolaria and pollen records from 0 to 50 ka at ODP Site 1233: Continental and marine climate records from the Southeast Pacific

    USGS Publications Warehouse

    Pisias, N.G.; Heusser, L.; Heusser, C.; Hostetler, S.W.; Mix, A.C.; Weber, M.

    2006-01-01

    Site 1233 drilled during Leg 202 of the Ocean Drilling Program provides a detailed record of marine and continental climate change in the Southeast Pacific and South American continent. Splits from over 500 samples taken at 20 cm intervals for quantitative analysis of radiolarian and pollen populations yield a temporal resolution of 200-400 years. In each sample, 39 pollen taxa and 40 radiolarian species and genera were evaluated. Age control is provided by 25 AMS 14C dates [Lamy, F., Kaiser, J., Ninnemann, U., Hebbeln, D., Arz, H.W., Stoner, J., 2004. Science 304, 1959-1962]. Multivariate statistical analyses of these data allow us to conclude the following: (1) During the past 50 ka, the region of the central Chile coast is not directly influenced by polar water from the Antarctic region. (2) Changes in ocean conditions off central Chile during this time interval primarily reflect north-south shifts in the position of the South Pacific transition zone. (3) Changes in Chilean vegetation reflect comparable latitudinal shifts in precipitation and the position of the southern westerlies. (4) The first canonical variate of radiolarian and pollen records extracted from Site 1233 are remarkably similar to each other as well as to temperature records from the Antarctic, which suggests that marine and continental climate variability in the region is tightly coupled at periods longer than 3000 years. (5) The phase coupling of these climate records, which lead variations of continental erosion based on iron abundance at the same site, are consistent with a hypothesis that erosion is linked to relatively long (i.e, few thousand years) response times of the Patagonian ice sheet, and thus is not a direct indicator of regional climate. ?? 2005 Elsevier Ltd. All rights reserved.

  19. Understanding Sun-Climate Connection by Analysis of Historical Sunspot, Auroral and Weather Records

    NASA Astrophysics Data System (ADS)

    Pang, K. D.; Yau, K. K.

    2005-12-01

    Fifty years of galactic cosmic ray data show changes with the solar cycle. Deflection of the highly energetic particles from exploding supernovae by the solar wind and associated magnetic field also modulates cosmogenic radioisotope production high in the atmosphere. The same trends are seen in carbon-14 and beryllium-10 abundances from long-lived trees and polar ice cores, respectively. Total solar irradiances measured by satellite radiometers show a 0.1% variance over the last two solar cycles, with only a small effect on global temperatures. A longer view is obviously needed. During the Maunder Minimum (1645-1715) sunspots were rarely seen. Total solar irradiances, reconstructed from historical sunspot data, were 0.24% lower, correlating nicely with an estimated 0.5-degree drop in Northern Hemisphere surface temperatures during the Little Ice Age [Lean and Rind, J. Clim. 11, 3069, 1998]. A longer time series has been reconstructed from even earlier records. From the frequencies of sunspot and auroral sightings in East Asian and European chronicles, C-14 and Be-10 abundances we have reconstructed the recent history of a variable Sun. In the past 1800 years the Sun has gone through nine cycles of brightness change. Although these long-term changes were <1% they have clearly affected the climate [Pang and Yau, Eos 83, No. 43, 481, 2002]. We have also analyzed Chinese historical weather records for comparison. Reports of unseasonable cold are classified by their degree of severity: (1) Late (April-June) or early (July-Sept.) killing frosts; (2) Bitter cold/heavy snowfall; and (3) Heavy sustained snowfall, bitter cold with frozen wells, lakes, rivers and icebound seas. The latter cases were often widespread and multi-year. All categories occurred most often during Maunder Minimum. The Category 3 episodes were in 1652-54, 1656, 1664, 1670-72, 1676-77, 1683, 1688-91, 1716 and 1718-19. The coldest time 1670-1697 coincides with lows in aurora sightings and numerical

  20. Verification of a coupled climate-hydrological model against Holocene palaeohydrological records

    NASA Astrophysics Data System (ADS)

    Ward, Philip J.; Aerts, Jeroen C. J. H.; de Moel, Hans; Renssen, Hans

    2007-06-01

    We have coupled a climate model (ECBilt-CLIO-VECODE) and a hydrological model (STREAM) offline to simulate palaeodischarge of nineteen rivers (Amazon, Congo, Danube, Ganges, Krishna, Lena, Mackenzie, Mekong, Meuse, Mississippi, Murray-Darling, Nile, Oder, Rhine, Sacramento-San Joaquin, Syr Darya, Volga, Volta, Zambezi) for three time-slices: Early Holocene (9000-8650 BP), Mid-Holocene (6200-5850 BP) and Recent (1750-2000 AD). To evaluate the model's skill in retrodicting broad changes in mean palaeodischarge we have compared the model results with palaeodischarge estimates from multi-proxy records. We have compared the general trends inferred from the proxy data with statistical differences in modelled discharge between the three periods, thereby developing a technique to assess the level of agreement between the model and proxy data. The quality of the proxy data for each basin has been classed as good, reasonable or low. Of the model runs for which the proxy data were good or reasonable, 72% were in good agreement with the proxy data, and 92% were in at least reasonable agreement. We conclude that the coupled climate-hydrological model performs well in simulating mean discharge in the time-slices studied. The discharge trends inferred from the proxy and model data closely follow latitudinal and seasonal variations in insolation over the Holocene. For a number of basins for which agreement was not good we have identified specific mechanisms which could be responsible for the discrepancy, primarily the absence of the Laurentide ice sheet in our model. In order to use the model in an operational sense within water management studies it would be useful to use a higher spatial resolution and a daily time-step.

  1. High-resolution conodont oxygen isotope record of Ordovician climate change

    NASA Astrophysics Data System (ADS)

    Chen, J.; Chen, Z.; Algeo, T. J.

    2013-12-01

    The Ordovician Period was characterized by several major events, including a prolonged 'super greenhouse' during the Early Ordovician, the 'Great Ordovician Biodiversification Event (GOBE)' of the Middle and early Late Ordovician, and the Hirnantian ice age and mass extinction of the latest Ordovician (Webby et al., 2004, The Great Ordovician Biodiversification Event, Columbia University Press). The cause of the rapid diversification of marine invertebrates during the GOBE is not clear, however, and several scenarios have been proposed including widespread development of shallow cratonic seas, strong magmatic and tectonic activity, and climate moderation. In order to investigate relationships between climate change and marine ecosystem evolution during the Ordovician, we measured the oxygen isotopic composition of single coniform conodonts using a Cameca secondary ion mass spectrometer. Our δ18O profile shows a shift at the Early/Middle Ordovician transition that is indicative of a rapid 6 to 8 °C cooling. This cooling event marks the termination of the Early Ordovician 'super greenhouse' and may have established cooler tropical seawater temperatures that were more favorable for invertebrate animals, setting the stage for the GOBE. Additional cooling episodes occurred during the early Sandbian, early Katian, and Hirnantian, the last culminating in a short-lived (<1-Myr) end-Ordovician ice age. The much cooler conditions that prevailed at that time may have been an important factor in the end-Ordovician mass extinction. Our results differ from those of Trotter et al. (2008, 'Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry,' Science 321:550-554). Instead of a slow, protracted cooling through the Early and Middle Ordovician, our high-resolution record shows that cooling occurred in several discrete steps, with the largest step being at the Early/Middle Ordovician transition.

  2. Protocol for Validation of the Land Surface Reflectance Fundamental Climate Data Record using AERONET: Application to the Global MODIS and VIIRS Data Records

    NASA Astrophysics Data System (ADS)

    Roger, J. C.; Vermote, E.; Holben, B. N.

    2014-12-01

    The land surface reflectance is a fundamental climate data record at the basis of the derivation of other climate data records (Albedo, LAI/Fpar, Vegetation indices) and a key parameter in the understanding of the land-surface-climate processes. It is essential that a careful validation of its uncertainties is performed on a global and continuous basis. One approach is the direct comparison of this product with ground measurements but that approach presents several issues related to scale, the episodic nature of ground measurements and the global representativeness. An alternative is to compare the surface reflectance product to reference reflectance determined from Top of atmosphere reflectance corrected using accurate radiative transfer code and very detailed measurements of the atmosphere obtained over the AERONET sites (Vermote and al, 2014, RSE) which allows to test for a large range of aerosol characteristics; formers being important inputs for atmospheric corrections. However, the application of this method necessitates the definition of a very detailed protocol for the use of AERONET data especially as far as size distribution and absorption are concerned, so that alternative validation methods or protocols could be compared. This paper describes the protocol we have been working on based on our experience with the AERONET data and its application to the MODIS and VIIRS record.

  3. A Long-Term and Reproducible Passive Microwave Sea Ice Concentration Data Record for Climate Studies and Monitoring

    NASA Technical Reports Server (NTRS)

    Peng, G.; Meier, W. N.; Scott, D. J.; Savoie, M. H.

    2013-01-01

    A long-term, consistent, and reproducible satellite-based passive microwave sea ice concentration climate data record (CDR) is available for climate studies, monitoring, and model validation with an initial operation capability (IOC). The daily and monthly sea ice concentration data are on the National Snow and Ice Data Center (NSIDC) polar stereographic grid with nominal 25 km × 25 km grid cells in both the Southern and Northern Hemisphere polar regions from 9 July 1987 to 31 December 2007. The data files are available in the NetCDF data format at http://nsidc.org/data/g02202.html and archived by the National Climatic Data Center (NCDC) of the National Oceanic and Atmospheric Administration (NOAA) under the satellite climate data record program (http://www.ncdc.noaa.gov/cdr/operationalcdrs.html). The description and basic characteristics of the NOAA/NSIDC passive microwave sea ice concentration CDR are presented here. The CDR provides similar spatial and temporal variability as the heritage products to the user communities with the additional documentation, traceability, and reproducibility that meet current standards and guidelines for climate data records. The data set, along with detailed data processing steps and error source information, can be found at http://dx.doi.org/10.7265/N5B56GN3.

  4. Holocene Arroyo Records in Southern Utah: A balance between Climate Forcing and Geomorphic Thresholds

    NASA Astrophysics Data System (ADS)

    Rittenour, T. M.

    2012-12-01

    important however, as high-discharge events were needed to initiate arroyo incision. In general, two of the study catchments show quasi-synchronous behavior over the last 2-3 ka and all catchments record an increased frequency of arroyo cutting events over the last 2-4 ka, contemporaneous with increased ENSO activity at this time. It is proposed that the timing of arroyo entrenchment is in-part catchment specific and is dependent on the relaxation/recovery time of these high sediment yield systems due to the time required to re-aggrade the floodplain and re-approach threshold conditions related to resultant increased long-profile concavity. Rapid entrenchment (arroyo cutting) is triggered by high-discharge events only once local threshold gradients are crossed. The specific timing of arroyo cutting is therefore dependent on the balance between catchment-specific geomorphic processes/thresholds and climate-related peak discharge patterns.

  5. From MODIS to VIIRS: Steps toward continuing the dark-target aerosol climate data record

    NASA Astrophysics Data System (ADS)

    Levy, R. C.; Mattoo, S.; Liu, H.; Munchak, L. A.; Laszlo, I.; Cronk, H.

    2012-12-01

    By this fall-2012 AGU meeting, the Moderate Resolution Imaging Spectrometer (MODIS) has been flying on NASA's Terra and Aqua satellites for 13 years and 10.5 years, respectively. During this time, the MODIS Aerosol Science Team has fine-tuned the aerosol retrieval algorithms and data processing protocols, resulting in a highly robust, stable and usable aerosol product. The aerosol optical depth (AOD) product has been validated extensively, and the MODIS-retrieved environmental data record (EDR) is becoming a strong foundation for creating an aerosol climate data record (CDR). With last year's launch of the Visible and Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP, the VIIRS-derived aerosol product has been designed to continue that provided by MODIS. VIIRS and MODIS have similar orbital mechanics and provide similar spectral resolution with similar spatial resolution. At the same time, the VIIRS and MODIS aerosol algorithms have similar physical assumptions. In fact, the initial validation exercises suggest that, in general, the VIIRS aerosol product is performing well, and that the expected error for the VIIRS-derived AOD is similar to that reported by MODIS. Although VIIRS should be able to derive an aerosol product similar in quality to MODIS, can the VIIRS aerosol record be "stitched" together with the MODIS record? To answer this question, instead of qualifying how similar they are, we need to quantify how their differences can and do impact the resulting aerosol products. There are instrumental differences, such as orbit altitude (805km versus 705km), spatial resolution (375m/750m versus 250m/500m/1000m), spectral differences, and sampling differences). There are pre-processing differences (cloud masking, gas correction assumptions, pixel selection protocols). There are retrieval algorithm differences, and of course final processing and quality control differences. Although we expect that most of differences have little or no impact, some may be

  6. Bering Sea records of climate and North Pacific Intermediate Water ventilation

    NASA Astrophysics Data System (ADS)

    Knudson, K. P.; Ravelo, A. C.

    2012-12-01

    Although much progress has been made in understanding the links between high-latitude paleoclimate and circulation in the North Atlantic, the relationship is poorly understood in the North Pacific. Some work has speculated that North Pacific climate on glacial-interglacial (G/IG) cycles is related to fluctuations in the prominence of North Pacific Intermediate Water (NPIW), based on evidence from data from short cores that shows increased ventilation during the Last Glacial Maximum. However, changes in North Pacific ventilation have not been evaluated on timescales long enough to validate this theory linking climate and NPIW production. New Bering Sea cores from Integrated Ocean Drilling Program Expedition 323 Site U1342, located within the present-day oxygen minimum zone (OMZ), contain alternating laminated and massive bioturbated sediments that may indicate changes in intensity and depth in the OMZ in response to variations in intermediate water ventilation and surface productivity. Here we show preliminary results from Site U1342 that evaluate changes in climate and Bering Sea ocean circulation over multiple glacial-interglacial cycles. δ13C and δ18O records from benthic foraminifera Uvigerina perigrina and δ15N of bulk sediment are compared to occurrences of laminated intervals over the past 800 kyr. During interglacials, much lighter benthic δ13C values at U1342 relative to deep Pacific site 849 indicate an older water mass at U1342, whereas similar benthic δ13C values at sites 849 and U1342 during glacials provide evidence for increased ventilation. Although laminated intervals, which are indicative of the most extreme reductions in oxygenation, occur more frequently during interglacial times, they are not strongly correlated to benthic δ13C and δ18O fluctuations. δ15N of bulk sediment, which may indicate changes in either denitrification and/or nutrient utilization, display little relationship to the G/IG intervals and display positive peaks in some

  7. Changing Requirements for Archiving Climate Data Records Derived From Remotely Sensed Data

    NASA Astrophysics Data System (ADS)

    Fleig, A. J.; Tilmes, C.

    2007-05-01

    With the arrival of long term sets of measurements of remotely sensed data it becomes important to improve the standard practices associated with archival of information needed to allow creation of climate data records, CDRs, from individual sets of measurements. Several aspects of the production of CDRs suggest that there should be changes in standard best practices for archival. A fundamental requirement for understanding long- term trends in climate data is that changes with time shown by the data reflect changes in actual geophysical parameters rather than changes in the measurement system. Even well developed and validated data sets from remotely sensed measurements contain artifacts. If the nature of the measurement and the algorithm is consistent over time, these artifacts may have little impact on trends derived from the data. However data sets derived with different algorithms created with different assumptions are likely to introduce non-physical changes in trend data. Yet technology for making measurements and analyzing data improves with time and this must be accounted for. To do this for an ongoing long term data set based on multiple instruments it is important to understand exactly how the preceding data was produced. But we are reaching the point where the scientists and engineers that developed the initial measurements and algorithms are no longer available to explain and assist in adapting today's systems for use with future measurement systems. In an era where tens to hundreds of man years are involved in calibrating an instrument and producing and validating a set of geophysical measurements from the calibrated data we have long passed the time when it was reasonable to say "just give me the basic measurement and a bright graduate student and I can produce anything I need in a year." Examples of problems encountered and alternative solutions will be provided based on developing and reprocessing data sets from long term measurements of

  8. Developing quantitative records of past climate and environment in Ireland: a palaeoecological, sedimentological and archaeological approach

    NASA Astrophysics Data System (ADS)

    Holmes, Naomi; Warren, Graeme; Davis, Steve; Turner, Jonathan; McCarron, Steve; Leng, Melanie; Brooks, Steve

    2010-05-01

    Much archaeological and palaeoecological research focussing on past relationships between humans and their local environment has been carried out in Ireland. The majority of the palaeoecological research has provided qualitative information about past environments, with an emphasis on palynological studies from lake and bog sites. There is, however, a lack of quantitative palaeoclimatic research from Ireland. The quantitative studies that have been carried out focus on the late-glacial to early-Holocene transition. The mid-Holocene remains relatively unstudied, even though this was a period of key changes in past society. This project aims to address the lack of quantitative data by producing palaeoenvironmental data from one area which is particularly rich in archaeological sites, north County Mayo, in the NW of Ireland. Results from this research will be presented here. This interdisciplinary project, involving palaeoecologists, archaeologists, and geographers, has a specific focus on the period from the adoption of agriculture in Ireland (c. 6000 cal. year BP) to a subsequent hypothesised decline in Neolithic agriculture (c. 5200 cal. year BP), both events argued to have been influenced by changes in climate. North County Mayo is a particularly important area in this context, with the internationally renowned sub-bog Neolithic field systems known as the Céide Fields, four excavated court-tombs, and, 6 km west of Céide, the small valley of Belderrig, which offers a remarkable range of materials from the Mesolithic to the later prehistoric. This area is thus ideal for examining interactions between changing settlement and environment over time. A 7 m core was obtained from Cregganmore, a small lake located c. 3 km from the main archaeological complexes in Belderrig. This core will provide a local palaeoclimatic (chironomid-inferred summer temperature) record which will complement extant palaeoenvironmental information (pollen studies) from this archaeologically

  9. Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa

    NASA Astrophysics Data System (ADS)

    Berke, Melissa A.; Johnson, Thomas C.; Werne, Josef P.; Grice, Kliti; Schouten, Stefan; Sinninghe Damsté, Jaap S.

    2012-11-01

    New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ˜14,000 year record of climate variability from Lake Victoria, East Africa, the world's second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific δD of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific δ13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ˜10-9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The δ13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the

  10. Fusion of Active and Passive Microwave Observations to Create AN Essential Climate Variable Data Record on Soil Moisture

    NASA Astrophysics Data System (ADS)

    Wagner, W.; Dorigo, W.; de Jeu, R.; Fernandez, D.; Benveniste, J.; Haas, E.; Ertl, M.

    2012-07-01

    Soil moisture was recently included in the list of Essential Climate Variables (ECVs) that are deemed essential for IPCC (Intergovernmental Panel on Climate Change) and UNFCCC (United Nations Framework Convention on Climate Change) needs and considered feasible for global observation. ECVs data records should be as long, complete and consistent as possible, and in the case of soil moisture this means that the data record shall be based on multiple data sources, including but not limited to active (scatterometer) and passive (radiometer) microwave observations acquired preferably in the low-frequency microwave range. Among the list of sensors that can be used for this task are the C-band scatterometers on board of the ERS and METOP satellites and the multi-frequency radiometers SMMR, SSM/I, TMI, AMSR-E, and Windsat. Together, these sensors already cover a time period of more than 30 years and the question is how can observations acquired by these sensors be merged to create one consistent data record? This paper discusses on a high-level possible approaches for fusing the individual satellite data. It is argued that the best possible approach for the fusion of the different satellite data sets is to merge Level 2 soil moisture data derived from the individual satellite data records. This approach has already been demonstrated within the WACMOS project (http://wacmos.itc.nl/) funded by European Space Agency (ESA) and will be further improved within the Climate Change Initiative (CCI) programme of ESA (http://www.esa-cci.org/).

  11. Preboreal climate oscillations in Europe: Wiggle-match dating and synthesis of Dutch high-resolution multi-proxy records

    NASA Astrophysics Data System (ADS)

    Bos, Johanna A. A.; van Geel, Bas; van der Plicht, Johannes; Bohncke, Sjoerd J. P.

    2007-08-01

    In order to compare environmental and inferred climatic change during the Preboreal in The Netherlands, five terrestrial records were analysed. Detailed multi-proxy analyses including microfossils (e.g., pollen, spores, algae, and fungal spores), macroremains (e.g., seeds, fruits, wood, mosses, etc.), and loss on ignition measurements were carried out with high temporal resolution. To link the five Preboreal records, accurate chronologies were produced by AMS 14C wiggle-match dating. The Dutch records show that following the Lateglacial/Holocene climate warming, birch woodlands expanded between 11,530 and 11,500 cal BP during the Friesland Phase of the Preboreal. After the Friesland Phase, two distinct climatic shifts could be inferred: (1) around 11,430-11,350 cal BP the expansion of birch forests was interrupted by a dry continental phase with open grassland vegetation, the Rammelbeek Phase. This phase was coeval with the coldest part of the Preboreal oscillation (PBO) as observed in the δ 18O record of the Greenland ice-core records and has been attributed to a large meltwater flux that resulted in a temporary decrease of the thermohaline circulation in the North Atlantic. (2) At the start of the Late Preboreal, between 11,270 and 11,210 cal BP, a sudden shift to a more humid climate occurred and birch forests expanded again. A simultaneous increase in the cosmogenic nuclides 14C and 10Be suggests that these changes in climate and vegetation were forced by a sudden decline in solar activity. Expansion of pine occurred during the later part of the Late Preboreal. At the onset of the Boreal, between 10,770 and 10,700 cal BP, dense woodlands with hazel, oak, elm and pine started to develop in The Netherlands.

  12. The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes

    USGS Publications Warehouse

    Funk, Chris; Peterson, Pete; Landsfeld, Martin; Pedreros, Diego; Verdin, James; Shukla, Shraddhanand; Husak, Gregory; Rowland, James; Harrison, Laura; Hoell, Andrew; Michaelsen, Joel

    2015-01-01

    The Climate Hazards group Infrared Precipitation with Stations (CHIRPS) dataset builds on previous approaches to ‘smart’ interpolation techniques and high resolution, long period of record precipitation estimates based on infrared Cold Cloud Duration (CCD) observations. The algorithm i) is built around a 0.05° climatology that incorporates satellite information to represent sparsely gauged locations, ii) incorporates daily, pentadal, and monthly 1981-present 0.05° CCD-based precipitation estimates, iii) blends station data to produce a preliminary information product with a latency of about 2 days and a final product with an average latency of about 3 weeks, and iv) uses a novel blending procedure incorporating the spatial correlation structure of CCD-estimates to assign interpolation weights. We present the CHIRPS algorithm, global and regional validation results, and show how CHIRPS can be used to quantify the hydrologic impacts of decreasing precipitation and rising air temperatures in the Greater Horn of Africa. Using the Variable Infiltration Capacity model, we show that CHIRPS can support effective hydrologic forecasts and trend analyses in southeastern Ethiopia.

  13. The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes

    PubMed Central

    Funk, Chris; Peterson, Pete; Landsfeld, Martin; Pedreros, Diego; Verdin, James; Shukla, Shraddhanand; Husak, Gregory; Rowland, James; Harrison, Laura; Hoell, Andrew; Michaelsen, Joel

    2015-01-01

    The Climate Hazards group Infrared Precipitation with Stations (CHIRPS) dataset builds on previous approaches to ‘smart’ interpolation techniques and high resolution, long period of record precipitation estimates based on infrared Cold Cloud Duration (CCD) observations. The algorithm i) is built around a 0.05° climatology that incorporates satellite information to represent sparsely gauged locations, ii) incorporates daily, pentadal, and monthly 1981-present 0.05° CCD-based precipitation estimates, iii) blends station data to produce a preliminary information product with a latency of about 2 days and a final product with an average latency of about 3 weeks, and iv) uses a novel blending procedure incorporating the spatial correlation structure of CCD-estimates to assign interpolation weights. We present the CHIRPS algorithm, global and regional validation results, and show how CHIRPS can be used to quantify the hydrologic impacts of decreasing precipitation and rising air temperatures in the Greater Horn of Africa. Using the Variable Infiltration Capacity model, we show that CHIRPS can support effective hydrologic forecasts and trend analyses in southeastern Ethiopia. PMID:26646728

  14. CERES FM-5 on the NPP Spacecraft: Continuing the Earth Radiation Budget Climate Data Record

    NASA Technical Reports Server (NTRS)

    Priestly, Kory; Smith, G. Louis

    2009-01-01

    The Clouds and the Earth's Radiant Energy System (CERES) Flight Model-5 (FM-5) instrument will fly on the NPOESS Preparatory Project (NPP) spacecraft, which has a launch-readiness date in June, 2010. This mission will continue the critical Earth Radiation Budget Climate Data Record (CDR) begun by the Earth Radiation Budget Experiment (ERBE) instruments in the mid 1980 s and continued by the CERES instruments currently flying on the EOS Terra and Aqua spacecraft. Ground calibrations have been completed for FM-5 and the instrument has been delivered for integration to the spacecraft Rigorous pre-launch ground calibration is performed on each CERES unit to achieve an accuracy goal of 1% for SW flux and 0.5% for outgoing LW flux. Any ground to flight or in-flight changes in radiometer response is monitored using a protocol employing both onboard and vicarious calibration sources and experiments. Recent studies of FM-1 through FM-4 data have shown that the SW response of space based broadband radiometers can change dramatically due to optical contamination. With these changes having most impact on optical response to blue-to UV radiance, where tungsten lamps are largely devoid of output, such changes are hard to monitor accurately using existing on-board sources. This paper outlines the lessons learned on the existing CERES sensors from 30+ years of flight experience and presents a radiometric protocol to be implemented on the FM-5 instrument to ensure that its performance exceeds the stated calibration and stability goals.

  15. The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes

    NASA Astrophysics Data System (ADS)

    Funk, Chris; Peterson, Pete; Landsfeld, Martin; Pedreros, Diego; Verdin, James; Shukla, Shraddhanand; Husak, Gregory; Rowland, James; Harrison, Laura; Hoell, Andrew; Michaelsen, Joel

    2015-12-01

    The Climate Hazards group Infrared Precipitation with Stations (CHIRPS) dataset builds on previous approaches to ‘smart’ interpolation techniques and high resolution, long period of record precipitation estimates based on infrared Cold Cloud Duration (CCD) observations. The algorithm i) is built around a 0.05° climatology that incorporates satellite information to represent sparsely gauged locations, ii) incorporates daily, pentadal, and monthly 1981-present 0.05° CCD-based precipitation estimates, iii) blends station data to produce a preliminary information product with a latency of about 2 days and a final product with an average latency of about 3 weeks, and iv) uses a novel blending procedure incorporating the spatial correlation structure of CCD-estimates to assign interpolation weights. We present the CHIRPS algorithm, global and regional validation results, and show how CHIRPS can be used to quantify the hydrologic impacts of decreasing precipitation and rising air temperatures in the Greater Horn of Africa. Using the Variable Infiltration Capacity model, we show that CHIRPS can support effective hydrologic forecasts and trend analyses in southeastern Ethiopia.

  16. A dinoflagellate cyst record of Holocene climate and hydrological changes along the southeastern Swedish Baltic coast

    NASA Astrophysics Data System (ADS)

    Yu, Shi-Yong; Berglund, Björn E.

    2007-03-01

    A high-resolution, well-dated dinoflagellate cyst record from a lagoon of the southeastern Swedish Baltic Sea reveals climate and hydrological changes during the Holocene. Marine dinoflagellate cysts occurred initially at about 8600 cal yr BP, indicating the onset of the Littorina transgression in the southeastern Swedish lowland associated with global sea level rise, and thus the opening of the Danish straits. Both the species diversity and the total accumulation rates of dinoflagellate cysts continued to increase by 7000 cal yr BP and then decreased progressively. This pattern reveals the first-order change in local sea level as a function of ice-volume-equivalent sea level rise versus isostatic land uplift. Superimposed upon this local sea level trend, well-defined fluctuations of the total accumulation rates of dinoflagellate cysts occurred on quasi-1000- and 500-yr frequency bands particularly between 7500 and 4000 cal yr BP, when the connection between the Baltic basin and the North Atlantic was broader. A close correlation of the total accumulation rates of dinoflagellate cysts with GISP2 ice core sea-salt ions suggests that fluctuations of Baltic surface conditions during the middle Holocene might have been regulated by quasi-periodic variations of the prevailing southwesterly winds, most likely through a system similar to the dipole oscillation of the modern North Atlantic atmosphere.

  17. Climatic, volcanic and tectonic events recorded in recent sediments of the Rukwa rift, Western Tanzania

    NASA Astrophysics Data System (ADS)

    Delvaux, D.; Mees, F.; Williamson, D.; Macheyeki, A. S.

    2009-04-01

    Lake Rukwa is now a shallow lake occupying the floor of the closed Rukwa depression in the western branch of the East African Rift System. Sediment records of the paleo-lake level show that during the Late Pleistocene to Early Holocene, Lake Rukwa reached the level of the overflow sill, 180 m higher than its present level, and was overflowing into Lake Tanganyika. Lacustrine sediments from this period are now exposed on the margin of the depression, and in particular along the Songwe River, where several large sections up to 35 meters high can be studied. Investigation of selected sections reveals a complex evolution in alternating fluvio-deltaic to lacustrine environment, punctuated by episodic inflow of volcanic material from the nearby Rungwe Volcanic Province. Macroscopic description of the sedimentary packages and their geometry, combined with C14 dating, diatom analysis, and optical microscopy allow to propose a preliminary evolution scheme in which climatically induced lake level change, volcanic input and tectonic influence can be reconstructed. In particular, correlations between sections at different altitudes allow to better constrain the lake level fluctuation than previous estimates based on drill core analysis.

  18. Late Ordovician land plant spore 13C fractionation records atmospheric CO2 and climate change

    NASA Astrophysics Data System (ADS)

    Beerling, D. J.; Nelson, D. M.; Pearson, A.; Wellman, C.

    2008-12-01

    Molecular systematics and spore wall ultrastructure studies indicate that late Ordovician diad and triad fossil spores were likely produced by plants most closely related to liverworts. Here, we report the first δ13C estimates of Ordovician fossil land plant spores, which were obtained using a spooling wire micro-combustion device interfaced with an isotope-ratio mass spectrometer (Sessions et al., 2005, Analytical Chemistry, 77, 6519). The spores all originate from Saudi Arabia on the west of Gondwana and date to before (Cardadoc, ca. 460 Ma), during (443Ma) and after (Llandovery, ca. 440Ma) the Hirnantian glaciation. We use these numbers along with marine carbonate δ13C records to estimate atmospheric CO2 by implementing a theoretical model that captures the strong CO2-dependency of 13C fractionation in non-vascular land plants (Fletcher et al., 2008, Nature Geoscience, 1, 43). Although provisional at this stage, reconstructed CO2 changes are consistent with the Kump et al. (2008) (Paleo. Paleo. Paleo. 152, 173) 'weathering hypothesis' whereby pre-Hirnantian cooling is caused by relatively low CO2 (ca. 700ppm) related to enhanced weathering of young basaltic rocks during the early phase of the Taconic uplift, with background values subsequently rising to around double this value by the earliest Silurian. Further analyses will better constrain atmospheric CO2 change during the late Ordovician climatic perturbation and address controversial hypotheses concerning the causes and timing of the Earth system transition into an icehouse state.

  19. Late Pleistocene Climatic Changes in the Western Mediterranean Inferred from Temperature, Productivity and Eolian Input Records: Implications for Human Dispersal

    NASA Astrophysics Data System (ADS)

    Hambach, B.; Rosell Mele, A.; Martinez-Garcia, A.

    2009-12-01

    The relation between climate and hominid dispersal has yet a number of unsettled issues, largely due to the lack of regional climate records in areas with significant hominid remains. Scientific evidence from the Mediterranean region indicates that humans evolved into their present form during key climatic intervals as indicated by the records of the earliest Europeans from Atapuerca (Spain) and Dmanisi (Georgia). However, it remains unclear which route was used by the early hominids to populate Europe (via the strait of Gibraltar or the Levantine Corridor). In this sense, it is still not clear if the climatic conditions during this period were favorable for hominid crossing via the strait of Gibraltar or not. To gain a better insight into the Iberian peninsular climate during the late Pleistocene, a marine sediment core from the Alboran Sea, Western Mediterranean, is used to reconstruct climate relevant variables related to surface ocean and atmospheric circulation by applying a set of organic geochemical proxies (biomarkers). In a first approach we present high resolution data (2 ky) for the interval from 0 to 500 ky. The results of this multi-biomarker analysis give new insights into past ocean climate conditions as well as into the processes that occurred onshore during this period. The reconstruction of sea surface temperatures is done by the analysis of alkenones (UK37-index). Total chlorins concentration is used as proxy for paleoproductivity. Terrestrial eolian inputs and vegetation changes are determined by the analysis of n-alkyl compounds (long chain n-alkanes, n-alkenols and n-alkanoic acids) which are major components of leaf waxes from terrestrial higher plants. Like mineral aerosols, these compounds are wind-transported from local vegetation sources to adjacent oceans where the particles settle and are preserved in ocean sediments with very little diagenetic alteration. These biomarkers offer a promising tool for reconstructing terrestrial vegetation

  20. Linking hydrological modeling and paleolimnological records for a better understanding of climate-hydrosphere interactions on the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Biskop, Sophie; Fink, Manfred; Fürstenberg, Sascha; Haberzettl, Torsten; Kasper, Thomas; Frenzel, Peter

    2016-04-01

    On the Tibetan Plateau (TP), where lake monitoring data are sparse, lacustrine systems, especially terminal lakes, act as sensitive indicators of climate variability, storing climatic and environmental information within their sediments. Thus, lake sediments are important archives for the reconstruction of hydrological changes and related climate conditions on decadal to millennial time scales. From a large number of lacustrine records on the TP, high lake levels were reconstructed for the Early Holocene, which are assumed to be related to a period climatically wetter than today. This study is the first attempt to integrate such paleoclimatic evidences from Tibetan lakes into hydrological modeling attempts to establish a quantitative reconstruction of climate variations. For the large lake Tangra Yumco (southern-central Tibetan Plateau) a high lake level indicated by an erosional terrace of 181 to 183 m above the recent lake level was dated to 8.5 ka. To maintain this high stand allowing forming a distinct lake level terrace, certain climatic conditions are needed. Considering the paleo-lake extension of Tangra Yumco and nearby lake Xuru Co, the hydrological model developed and evaluated for present-day conditions was run through several scenarios of precipitation and temperature changes. The High Asia Reanalysis (HAR) atmospheric data set for the period 2001-2010 (10 km, daily resolution) served as meteorological driver for the process-oriented conceptual hydrological model built within the Jena Adaptable Modeling System. Based on inverse modeling, this study estimates the amount of precipitation and temperature to maintain a state close to equilibrium during the lake level high-stand at 8.5 ka. This study highlights the benefits of water balance simulations by combining paleolake records and synthetic climates derived from atmospheric model data, in order to deepen the understanding of the response of hydrological systems to climate variability.

  1. Sequential planning of flood protection infrastructure under limited historic flood record and climate change uncertainty

    NASA Astrophysics Data System (ADS)

    Dittes, Beatrice; Špačková, Olga; Straub, Daniel

    2017-04-01

    Flood protection is often designed to safeguard people and property following regulations and standards, which specify a target design flood protection level, such as the 100-year flood level prescribed in Germany (DWA, 2011). In practice, the magnitude of such an event is only known within a range of uncertainty, which is caused by limited historic records and uncertain climate change impacts, among other factors (Hall & Solomatine, 2008). As more observations and improved climate projections become available in the future, the design flood estimate changes and the capacity of the flood protection may be deemed insufficient at a future point in time. This problem can be mitigated by the implementation of flexible flood protection systems (that can easily be adjusted in the future) and/or by adding an additional reserve to the flood protection, i.e. by applying a safety factor to the design. But how high should such a safety factor be? And how much should the decision maker be willing to pay to make the system flexible, i.e. what is the Value of Flexibility (Špačková & Straub, 2017)? We propose a decision model that identifies cost-optimal decisions on flood protection capacity in the face of uncertainty (Dittes et al. 2017). It considers sequential adjustments of the protection system during its lifetime, taking into account its flexibility. The proposed framework is based on pre-posterior Bayesian decision analysis, using Decision Trees and Markov Decision Processes, and is fully quantitative. It can include a wide range of uncertainty components such as uncertainty associated with limited historic record or uncertain climate or socio-economic change. It is shown that since flexible systems are less costly to adjust when flood estimates are changing, they justify initially lower safety factors. Investigation on the Value of Flexibility (VoF) demonstrates that VoF depends on the type and degree of uncertainty, on the learning effect (i.e. kind and quality of

  2. Long Term Seasonality Changes and Short Term Climate Variability Recorded in Eurasian Loess: Examples from Serbia, Romania, Kazakhstan, and China

    NASA Astrophysics Data System (ADS)

    Machalett, B.; Oches, E. A.; Haam, E.; Lai, Z. P.; Endlicher, W.

    2012-04-01

    Past climate dynamics associated with the Eurasian continent are well studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of considerable debate. While western Atlantic polar and tropical air masses penetrate into the continent and are modified and transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmosphere and ocean processes and regulate teleconnection patterns of the Northern Hemisphere. The distribution of Eurasian loess deposits allows interregional palaeoclimatic investigations along a west-east transect across the entire Eurasian loess belt of the Northern Hemisphere, offering the potential to reconstruct Pleistocene atmospheric circulation patterns and aeolian dust dynamics on a wide spatial scale. This paper utilizes high resolution particle size data from several loess sequences across Eurasia (Serbia, Romania, Kazakhstan, and China) that provide a detailed signal of glacial-interglacial atmospheric dynamics and long term, semi-continuous trends in the aeolian dust record since marine isotope stage 10. In consideration of the modern synoptic atmospheric circulation patterns and aeolian dust transport across the Eurasian landmass, we propose that the observed data reflect oscillations superimposed on a long term signal of seasonality, triggered by changes in duration and permanency of the seasonal shift of the Eurasian polar front during the middle to late Pleistocene. As the activity of the polar front jet is intimately connected with the high level planetary frontal zone (HPFZ), the Eurasian loess archives may also serve as a recorder of intra-hemispheric climate connections in past atmospheric circulation. Although there are large scale similarities in

  3. What climate information is recorded in stable isotope ratios of wood lignin methoxyl groups?

    NASA Astrophysics Data System (ADS)

    Greule, Markus; Keppler, Frank

    2010-05-01

    The stable isotope composition of the bioelements C, O, H and N in plant organic matter is known to be a very powerful for various environmental impacts. Particularly tree rings are suitable for this analysis because they exhibit a "climate archive" with a yearly or even biannual resolution. One of the most determined wood compounds is cellulose which amongst others is used to reconstruct the temperature due to measurement of stable hydrogen and oxygen isotopes. Therefore cellulose is converted into cellulose nitrate to eliminate the exchangeable hydroxyl hydrogen or equilibration methods are used. However, a general problem associated with the determination of the stable hydrogen values of marker compounds for the study of climate and environmental conditions is the isolation of the pure compound for analysis by isotope ratio mass spectrometry. Exploitation of components of wood as markers, in particular, has been restricted by the very labour intensive and time consuming preparation of samples (e.g. cellulose nitrate). An alternative way to record climate information from tree rings was recently proposed by Keppler et al. (2007) who measured the stable hydrogen values of methoxyl groups in wood. Lignin methoxyl groups are considered to be stable, i.e. the hydrogen atoms of the methoxyl moiety do not exchange with those of plant water during ongoing metabolic reactions in the plant. Thus the initial deuterium content of the methoxyl groups of lignin in woody tissue at formation is retained throughout the lifetime of the tree and in preserved tissue. The methoxyl content of lignin in wood is usually determined by the Zeisel method (Zeisel, 1885) - the reaction between methyl ethers and hydroiodic acid to form methyl iodide. Exploiting this reaction for the measurement of stable hydrogen values of lignin methoxyl groups ensures that during the entire analytical procedure the isotope signal is preserved since no isotopic exchange occurs between the methyl groups and

  4. The accumulation record from the GISP2 core as an indicator of climate change throughout the holocene

    SciTech Connect

    Meese, D.A.; Gow, A.J.; Grootes, P.; Stuiver, M.; Waddington, E.D.; Mayewski, P.A.; Zielinski, G.A.

    1994-12-09

    A depth-age scale and an accumulation history for the Holocene have been established on the Greenland Ice Sheet Project 2 (GISP2) deep core, providing the most continuously dated record of annual layer accumulation currently available. The depth-age scale was obtained with the use of various independent techniques to count annual layers in the core. An annual record of surface accumulation during the Holocene was obtained by correcting the observed layer thicknesses for flow-thinning. Fluctuations in accumulation provide a continuous and detailed record of climate variability over central Greenland during the Holocene. Climate events, including {open_quotes}Little Ice Age{close_quotes} type events, are examined.

  5. Amplitude-frequency fluctuations of the seasonal cycle, temperature anomalies, and long-range persistence of climate records.

    PubMed

    Vecchio, A; Carbone, V

    2010-12-01

    The presence of long-term persistence of climate records on scales from 2 to 15 yr has been reported in the literature, even if the universality of this result is controversial. In the present paper results from monthly temperature records measured for about 250 yr in Prague and Milan are reported. Because of the nonlinear and nonstationary character of temperature time series the seasonal contribution has been identified through the empirical mode decomposition. We find that the seasonal component of the climate records is characterized by some time scales showing both amplitude and phase fluctuations. By using a more suitable definition of temperature anomalies, and thus excluding persistence effects due to seasonal oscillations and trends, the occurrence of long-term persistence has been investigated through the detrended fluctuation analysis. Our results indicate persistence on scales from 3 to 10 yr with similar values for the detrended fluctuation analysis indices.

  6. Reinterpreting the Crystal Cave speleothem record with statistics, climate models, and proxy system models

    NASA Astrophysics Data System (ADS)

    Hu, J.; Emile-Geay, J.; Partin, J. W.; Dee, S.

    2016-12-01

    The oxygen isotope composition of speleothem calcite is commonly used as a paleoclimate proxy due to its potential for accurate dating and high temporal resolution, but its interpretation can be complex. Here we present a cautionary tale from Crystal Cave, CA, which exemplifies the danger of statistical calibrations as the sole basis for proxy interpretation. The Crystal Cave δ18O record [1] was interpreted as a proxy for sea surface temperature in the Kuroshio Extension region on the basis of an apparently high correlation. Here we show by considering serial autocorrelation, test multiplicity ("look elsewhere" effect), and age uncertainties, that this interpretation is potentially based on a statistical artifact. Using the published age model, we first revisit the correlation analysis by considering the effect of serial correlation. The resulting degrees of freedom decrease, raising the bar for significance. Consideration of the false discovery rate due to the multiplicity problem [2] further reduces the number of gridpoints exhibiting significant correlations. Finally, we quantify age uncertainties using Bchron [3], providing an ensemble of 1,000 possible realizations of the δ18O time series. A statistical analysis of correlations with this ensemble challenges the published interpretation of the Crystal Cave record [1], finding no robust relationship to sea-surface temperature. Our study cautions against "correlation-fishing" as a basis for paleoclimate interpretation, and reaffirms the importance of mechanistic studies as a foundation of this interpretation. Accordingly, we propose a new interpretation of the Crystal Cave δ18O record based on an isotope-enabled climate model [4] and a proxy system model for speleothem calcite [5]. References [1] McCabe-Glynn, S., et al., 2013. Nat. Geosci. 6, 617-621.. [2] Benjamini, Y., Hochberg, Y., 1995. J. R. Stat. Ser. Series B (Methodological) 57, 289-300. [3] Haslett, J., Parnell, A., 2008. J. R. Stat. Soc. Ser. C

  7. Multiproxy Records of Indo-Pacific Climate and Environmental Change from Lake Towuti, Indonesia, Since 60 Kyr BP

    NASA Astrophysics Data System (ADS)

    Russell, J. M.; Vogel, H.; Bijaksana, S.; Konecky, B. L.; Wicaksono, S. A.; Costa, K.; Wattrus, N. J.; Melles, M.

    2014-12-01

    Lake Towuti is a large tectonic lake in central Sulawesi, Indonesia that provides a unique opportunity to reconstruct climate and terrestrial environments in the heart of the Indo-Pacific warm pool. Long-term climate variations in this region are governed by a complex interplay between the Australasian monsoons and the ENSO system forced by changing insolation, sea level, ice sheets, and greenhouse gas concentrations. Existing reconstructions suggest heterogeneous responses of Indonesian climate to these forcings, highlighting the need for new long records of regional hydrology. We have developed multiproxy datasets from Lake Towuti and nearby lakes that provide continuous, detailed, and reproducible paleoenvironmental records spanning the past 60 kyr BP. Elemental tracers of terrestrial runoff and compound-specific stable isotope records of vegetation show that wet conditions and rainforest ecosystems persisted during Marine Isotope Stage 3 and the Holocene, and were interrupted by severe drying between 33 and 15 kyr BP when high-latitude ice sheets expanded and global temperatures cooled. This chronology of change implies that central Indonesian hydroclimate varies strongly in response to high-latitude climate forcing. New vegetation records from nearby lakes confirm these findings, but suggest the amplitude of glacial-interglacial changes in vegetation were weaker at high altitude, with important implications for the heterogeneity among Indonesian climate reconstructions. New lithologic and trace element records from Lake Towuti further document the significance of climate changes at the MIS3, 2, and 1 boundaries to Lake Towuti's paleolimnology, heat budget, and seasonal mixing. High-resolution seismic reflection data from Lake Towuti constrain the maximum depth of lake level lowstands during MIS2. Hydrological modeling suggests that precipitation was reduced by at least 50% at that time, an amplitude at or above the upper limits of precipitation changes

  8. A 60,000-yr record of climate in Southeast Tropical Africa: Preliminary results from Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Tierney, J.; Russell, J.

    2006-12-01

    Few paleoclimate records exist that record high-frequency climate variability within tropical Africa, particularly during Marine Isotope Stage 3 (30-60,000 years BP). Thus very little is known about the potential role or response the region may have with regards to high-latitude abrupt climate change. However, climate variability in tropical East Africa is linked to large-scale changes in the convective intensity and location of the inter- tropical convergence zone (ITCZ) and the strength of the seasonal monsoonal winds from both the Atlantic and Indian Oceans. Understanding tropical African climate history may illuminate the causes and amplifying mechanisms of global climate change. We present here a multiproxy record of 60,000 years of climate variability from the sediments of Lake Tanganyika, southeast tropical Africa, which addresses outstanding questions regarding the role of East Africa in the context of abrupt climate change. Continuously accumulating hemipelagic sediments recovered from 650 m water depth from the southern half of Lake Tanganyika record hydrologic variability, terrestrial paleoenvironments, and changes in wind-driven upwelling intensity. Major element variations in Tanganyika sediments measured at 1 mm resolution by scanning XRF resolve changes in sediment geochemistry over decadal to centennial timescales, shedding light on the amplitude and frequency of short-term climate variability in this region. Additionally, records of bulk stable isotopes (δ13C, δ15N), compound- specific δD, and biogenic silica indicate rapid, dramatic changes in lake productivity, vegetation, and rainfall over millennial time-scales from Marine Isotope Stage 3 to present, including the Younger Dryas. In the case of the latter, the Younger Dryas is manifest in Lake Tanganyika as a sedimentary sequence of low diatom content, indicating reductions in southerly monsoonal windspeed and lake upwelling, and hydrogen isotope data over this interval indicate significant

  9. Can Convergent Cross Mapping Untangle Idiosyncratic Speleothem Proxy Records to Reveal the Structure of Shared Climate Forcing?

    NASA Astrophysics Data System (ADS)

    Frappier, A. E.

    2015-12-01

    Rapid growth and development of speleothem paleoclimatology has generated diverse and important new terrestrial paleoenvironmental proxy records that increasingly illuminate both the enormous potential and great complexity of cave proxy systems and speleothem data. Speleothem records commonly exhibit complex covariation patterns between proxy variables (i.e. carbon and oxygen isotopes, various trace element concentrations and ratios, stratigraphic characteristics, growth rates, etc...). Such covariation patterns frequently change sign and magnitude over time, and often show periods without significant correlation that alternate with times with strongly coupled behavior. These patterns are evident when comparing records between sites and stalagmites, and even within a single stalagmite. Instability in covariation patterns and low long-term correlations both limit our confidence in applying speleothems proxy transfer functions over long time periods. Are these complex covariation patterns meaningful or merely mirages? When two speleothem records show the same result, replication is considered by the community to be evidence that both records are highly sensitive to a common climate signal and are thus reliable proxies for that climate signal. Signals derived from a single speleothem dataset could be noise, and thus of limited value until it is validated by the replication test. Are speleothems naturally idiosyncratic and noisy? Must all speleothem records be duplicated to establish reliability? I consider whether Convergent Cross Mapping (CCM) may offer a fruitful approach to these problems. CCM is a powerful statistical tool developed in George Sugihara's lab for complex dynamical systems that tests the direction of causality and strength of forcing among multiple time-series variables. I apply CCM to speleothem timeseries records to 1) reconstruct the underlying state climate variable of interest over time (in this case, precipitation), and 2) determine the

  10. Climate variability from the Florida Bay sedimentary record: Possible teleconnections to ENSO, PNA and CNP

    USGS Publications Warehouse

    Cronin, T. M.; Dwyer, G.S.; Schwede, S.B.; Vann, C.D.; Dowsett, H.

    2002-01-01

    We analyzed decadal and interannual climate variability in South Florida since 1880 using geochemical and faunal paleosalinity indicators from isotopically dated sediment cores at Russell Bank in Florida Bay (FB). Using the relative abundance of 2 ostracode species and the Mg/Ca ratios in Loxoconcha matagordensis shells to reconstruct paleosalinity, we found evidence for cyclic oscillations in the salinity of central FB. During this time salinity fluctuated from as low as ???18 parts per thousand (ppt) to as high as ???57 ppt. Time series analyses suggest, in addition to a 5.6 yr Mg/Ca based salinity periodicity, there are 3 other modes of variability in paleosalinity indicators: 6-7, 8-9, and 13-14 yr periods which occur in all paleo-proxies. To search for factors that might cause salinity to vary in FB, we compared the Russell Bank paleosalinity record to South Florida winter rainfall, the Southern Oscillation Index (SOI), winter North Atlantic Oscillation (NAO), and the winter Pacific North American (PNA) index, and a surrogate for the PNA in the winter season, the Central North Pacific (CNP) index. SOI and PNA/CNP appear to be associated with South Florida winter precipitation. Time series analyses of SOI and winter rainfall for the period 1910-1999 suggest ???5, 6-7, 8-9 and 13-14 yr cycles. The 6-7 yr and 13-14 yr cycles correspond to those observed in the faunal and geochemical time series from Russell Bank. The main periods of the CNP index are 5-6 and 13-15 yr, which are similar to those observed in FB paleosalinity. Cross-spectral analyses show that winter rainfall and salinity are coherent at 5.6 yr with a salinity lag of ???1.6 mo. These results suggest that regional rainfall variability influences FB salinity over interannual and decadal timescales and that much of this variability may have its origin in climate variability in the Pacific Ocean/atmosphere system.

  11. Detrital cave sediments record Late Quaternary hydrologic and climatic variability in northwestern Florida, USA

    NASA Astrophysics Data System (ADS)

    Winkler, Tyler S.; van Hengstum, Peter J.; Horgan, Meghan C.; Donnelly, Jeffrey P.; Reibenspies, Joseph H.

    2016-04-01

    Detrital sediment in Florida's (USA) submerged cave systems may preserve records of regional climate and hydrologic variability. However, the basic sedimentology, mineralogy, stratigraphic variability, and emplacement history of the successions in Florida's submerged caves remains poorly understood. Here we present stratigraphic, mineralogical, and elemental data on sediment cores from two phreatic cave systems in northwestern Florida (USA), on the Dougherty Karst Plain: Hole in the Wall Cave (HITW) and Twin Cave. Water flowing through these caves is subsurface flow in the Apalachicola River drainage basin, and the caves are located just downstream from Jackson Blue (1st magnitude spring, > 2.8 m3 s- 1 discharge). Sedimentation in these caves is dominated by three primary sedimentary styles: (i) ferromanganese deposits dominate the basal recovered stratigraphy, which pass upsection into (ii) poorly sorted carbonate sediment, and finally into (iii) fine-grained organic matter (gyttja) deposits. Resolving the emplacement history of the lower stratigraphic units was hampered by a lack of suitable material for radiocarbon dating, but the upper organic-rich deposits have a punctuated depositional history beginning in the earliest Holocene. For example, gyttja primarily accumulated in HITW and Twin Caves from ~ 5500 to 3500 cal yr. BP, which coincides with regional evidence for water-table rise of the Upper Floridian Aquifer associated with relative sea-level rise in the Gulf of Mexico, and evidence for invigorated drainage through the Apalachicola River drainage basin. Gyttja sediments were also deposited in one of the caves during the Bølling/Allerød climate oscillation. Biologically, these results indicate that some Floridian aquatic cave (stygobitic) ecosystems presently receive minimal organic matter supply in comparison to prehistoric intervals. The pre-Holocene poorly sorted carbonate sediment contains abundant invertebrate fossils, and likely documents a period

  12. Seeing the climate through the trees: observing climate and forestry impacts on streamflow using a 60-year record

    Treesearch

    T. P. Burt; N. J. K. Howden; J. J. McDonnell; J. A. Jones; G. R. Hancock

    2014-01-01

    Paired watershed experiments involving the removal or manipulation of forest cover in one of the watersheds have been conducted for more than a century to quantify the impact of forestry operations on streamflow. Because climate variability is expected to be large, forestry treatment effects would be undetectable without the treatment–control comparison. New...

  13. Early to middle Miocene climate evolution: benthic oxygen and carbon isotope records from Walvis Ridge Site 1264.

    NASA Astrophysics Data System (ADS)

    Lourens, L. J.; Beddow, H.; Liebrand, D.; Schrader, C.; Hilgen, F. J.

    2016-12-01

    Across the early to middle Miocene, high-resolution records from the Pacific Ocean indicate a dynamic climate system, encompassing a 2 Myr global warming event from 17 Ma to 14.7 Ma, followed by a major Cenozoic cooling step at 14.2 Ma -13.8 Ma. Currently, no high-resolution benthic record from the Atlantic Ocean exists covering both events, limiting global coverage of this intriguing period in Cenozoic climate evolution. Here, we present the first early to middle Miocene high-resolution from the Atlantic basin. These records, from Site 1264 on the Walvis Ridge, span a 5.5 Myr long interval (13.24-18.90 ma) in high temporal resolution ( 4 kyr) and are tuned to eccentricity. The d18O record shows a sudden (high-latitude) warming/deglaciation on Antarctica at 17.1 Ma, a rapid cooling/glaciation of Antarctica at 13.8 Ma, and high-amplitude ( 1‰) variability on astronomical time-scales throughout this interval. Together with other records from this time interval located in the Pacific, which show similar features, the data strongly suggests a highly dynamic global climate system. We find cooling steps in d18O at 14.7, 14.2 and 13.8 Ma, suggesting concurrent cooling in the Pacific and Atlantic deep waters during the MMCT. The benthic foraminiferal stable isotope records reveal that the dominant astronomical frequencies present at ODP Site 1264 during the early to middle Miocene interval are the 405 kyr and 110 kyr eccentricity periodicities. This is a contrast to other early to middle Miocene records from drill-sites in the Pacific and South China Sea, which show a strong expression of obliquity in particular between 14.2 and 14.7 Ma.

  14. Holocene environments and climate in the Mongolian Altai reconstructed from the Hoton-Nur pollen and diatom records: a step towards better understanding climate dynamics in Central Asia

    NASA Astrophysics Data System (ADS)

    Rudaya, Natalia; Tarasov, Pavel; Dorofeyuk, Nadezhda; Solovieva, Nadia; Kalugin, Ivan; Andreev, Andrei; Daryin, Andrei; Diekmann, Bernhard; Riedel, Frank; Tserendash, Narantsetseg; Wagner, Mayke

    2009-03-01

    This study presents the results of the palynological and diatom analyses of the sediment core recovered in Hoton-Nur Lake (48°37'18″N, 88°20'45″E, 2083 m) in 2004. Quantitative reconstruction of the Holocene vegetation and climate dynamics in the semiarid Mongolian Altai suggests that boreal woodland replaced the primarily open landscape of northwestern Mongolia at about 10 kyr BP (1 kyr = 1000 cal yr) in response to a noticeable increase in precipitation from 200-250 mm/yr to 450-550 mm/yr. A decline of the forest vegetation and a return to a predominance of open vegetation types occurred after 5 kyr BP when precipitation sums decreased to 250-300 mm/yr. Prior to 11.5 kyr BP diatom concentrations are relatively low and the lake is dominated by planktonic Cyclotella and small Fragilariaceae, suggesting the existence of a relatively deep and oligotrophic/mesotrophic lake. The great abundance of Staurosirella pinnata from the beginning of the record until 10.7 kyr BP might imply intensified erosion processes in the catchment and this is fully consistent with the presence of scarce and dry vegetation and the generally arid climate during this period. From about 10.7 kyr BP, more planktonic diatom taxa appeared and increased in abundance, indicating that the lake became more productive as diatom concentration increased. This change correlates well with the development of boreal woodland in the catchment. Decrease in precipitation and changes in the vegetation towards steppe are reflected by the rapid increase in Aulacoseira distans from about 5 kyr BP. The Holocene pollen and diatom records do not indicate soil and vegetation cover disturbances by the anthropogenic activities, implying that the main transformations of the regional vegetation occurred as a result of the natural climate change. Our reconstruction is in agreement with the paleomonsoon records from China, demonstrating an abrupt strengthening of the summer monsoon at 12 kyr BP and an associated

  15. Wildland fire probabilities estimated from weather model-deduced monthly mean fire danger indices

    Treesearch

    Haiganoush K. Preisler; Shyh-Chin Chen; Francis Fujioka; John W. Benoit; Anthony L. Westerling

    2008-01-01

    The National Fire Danger Rating System indices deduced from a regional simulation weather model were used to estimate probabilities and numbers of large fire events on monthly and 1-degree grid scales. The weather model simulations and forecasts are ongoing experimental products from the Experimental Climate Prediction Center at the Scripps Institution of Oceanography...

  16. Decadal climate variation recorded in modern global carbonate archives (brachiopods, molluscs)

    NASA Astrophysics Data System (ADS)

    Romanin, Marco; Zaki, Amir H.; Davis, Alyssa; Shaver, Kristen; Wang, Lisha; Aleksandra Bitner, Maria; Capraro, Luca; Preto, Nereo; Brand, Uwe

    2017-04-01

    The progress of the Earth's warming trend has rapidly accelerated in the last few decades due to the increase in emission of anthropogenic greenhouse gases. The exchange of heat between the atmosphere and seawater has consequently elevated the rate of temperature buildup in the low and high latitude ocean. Records of the variation in seawater temperature in response to local and global changes in climate are preserved within the carbonate structures of marine biogenic archives. Investigating the isotopic composition of the archives' growth increments documents the magnitude of sea surface temperature (SST) change. A long-term (1956-2012) record of temperature change in sub-tropical seawater was acquired from the giant clam Tridacna maxima collected from the Red Sea in conjunction with published results of the oyster Hyotissa hyotis (Titschack et al., 2010). Variation in polar-subpolar SST was obtained from the brachiopod Magellania venosa recovered from the coastal area of southern Chile, and from the proxy record of Hemithiris psittacea of Hudson Bay (Brand et al., 2014). The former reveals a long-term (1961-2012) time-series of Antarctic-induced oceanographic change in the southern hemisphere, while the latter represents a trend of Hudson Bay seawater SST in the northern hemisphere. Evaluation of the isotopic compositions confirms the equilibrium incorporation of oxygen isotopes with respect to ambient seawater in brachiopods and some bivalves. A general trend of decreasing δ18O values in the Red Sea molluscs is observed, indicating an increase in tropical seawater temperature of about 0.79°C since 1988. The δ18O values of the polar-subpolar brachiopods display similar depletion slopes but of larger magnitudes than that of the Red Sea archives. This signifies a rise in seawater temperature of about 1.47°C in Hudson Bay since 1991, and about 2.08°C in southern Chile since 1988. The 2013 IPCC report suggests an increase in SST of +0.094°C per decade (average

  17. Regional climate signal modified by local factors - multi core study records (Lake Czechowskie region, N Poland)

    NASA Astrophysics Data System (ADS)

    Zawiska, Izabela; Rzodkiewicz, Monika; Noryśkiewicz, Agnieszka; Kramkowski, Mateusz; Obremska, Milena; Ott, Florian; Plessen, Birgit; Tjallingii, Rik; Słowiński, Michał; Błaszkiewicz, Mirosław; Brauer, Achim

    2016-04-01

    Lake sediments can be utilized as valuable paleoclimate and environmental archives as they contain information of past changes. Multi-proxy analyses of sedimentary compartments (e.g. pollen, diatoms, Cladocera) reveal those changes. However, to decipher the spatial variability of past climate changes and to define the proxies suited for local and regional scale reconstructions archive comparisons are needed. Here we present a detailed multi-proxy study from four different sediment cores covering the Younger Dryas cold period from the Lake Czechowskie region (N Poland). Three cores are located along a transect in the Lake Czechowskie basin from its deepest point towards a former lake bay close to today's shoreline. The fourth lacustrine sediment core was retrieved from the Trzechowskie paleolake, app. 1 km W from Lake Czechowskie. The dataset comprises information from pollen (AP, NAP, Juniperus, Betula-tree, Pinus silvestris), diatom (planktonic/benthic index, diatom valve concentration, dominant species), Cladocera (planktonic/benthic index, dominant species, number of Cladocera species, total sum of specimens) and geochemical (TOC and CaCO3 content, mineral matter, titanium) analyses. At the beginning of the Younger Dryas the AP pollen share decreased and NAP and Juniperus pollen increased in all studied locations. The mineral matter and titanium record showed higher values in two cores taken from the deepest parts of Lake Czechowskie and the core from Trzechowskie paleolake while in the core located at the marginal part of the lake it was already high in Allerød and it did not change much in Younger Dryas. The Cladocera based indexes: total sum of specimens and number of species decreased at the beginning of YD but on the contrary the Cladocera species composition changes were site-specific. The diatoms valve concentration index significantly lowered in core from the deep location while on the contrary increased in core from paleolake Trzechowskie. Our results

  18. Climatic variability during the last deglaciation: A stalagmite-based multi-proxy record from Mawmluh cave, India

    NASA Astrophysics Data System (ADS)

    Huguet, C.; Munnuru Singamshetty, K.; Routh, J.; Fietz, S.; Mangini, A.; Ghosh, P.; Lone, M. A.; Rangarajan, R.; Eliasson, J.

    2016-12-01

    The Mawmluh cave in northeastern India, is affected by global climate patterns displaying glacial-interglacial patterns and also the Indian Summer Monsoon (ISM). Precipitation from the ISM plays a vital role for the local community and thus, understanding the driving forces of ISM fluctuations became a recent focus of a number of paleoclimate studies. Here, we used the stalagmite KM-1 from Mawmluh cave to reconstruct climate variability during the last glacial-interglacial transition from 22 to 6 ka. For the first time, molecular proxy data (TEX86 and MBT/CBT derived from isoprenoid and branched GDGTs respectively) were coupled to stable isotope records (δ13C and δ18O) and compared to other speleothem records in Asia. ISM system abruptly transition between a suppressed and active state which is associated to changes in vegetation and thus shifts in δ13C. The abrupt δ13C shift observed in our record indicate changes to wetter climate in the Holocene, which are coupled to increase in abundance of GDGTs indicating higher production and/or transfer to KM-1. The TEX86-derived temperature roughly follows the glaciation-deglaciation cycle and Holocene changes. The TEX86 results show good correspondence with the δ18O records for temperature highlighting the potential for the use of molecular proxy in speleothem based climate reconstructions. While the MBT/CBT proxy is also defined as a temperature proxy it is not coupled with δ18O patterns, and thus shows no clear temperature signal. A decoupling between MBT/CBT from soils and the connected speleothems as well as a precipitation-moisture effect on this proxy have been previously reported. In this particular case the MBT/CBT seems to be better related to precipitation-monsoon changes, and thus warrant further exploration as a complementary proxy to isotope records for monsoon strength.

  19. The Recognition of Multi-Decadal Scale Climate Variability in the Paleo-record over the Past 1000 Years

    NASA Astrophysics Data System (ADS)

    Swart, Peter; Waite, Amanda; Rosenheim, Brad; Moses, Chris

    2010-05-01

    Proxy reconstructions of climate from tree rings, corals, stalagmites, sclerosponges, and deep-sea sediments show multi-decadal climate variability preserved in records extending back at least 1000 years. Most of these records appear to show a strong correlation with indices such as the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO) over the period of the instrumental record (~1850-present). The repeated recognition of these signals in a number of different archives and geographical locations throughout the Atlantic (Cape Verde Islands, Gulf of Guinea, Puerto Rico, Cariaco Basin , South Florida, and the Bahamas) strongly suggests that these signals are real and have climatic significance. The AMO and NAO climate signals are manifested in these indices through (i) the direct effect of water temperature and salinity on the growth rate of trees and corals and (ii) temperature and salinity influences on the incorporation of geochemical proxies, such as the Mg/Ca, Sr/Ca, and oxygen isotopic ratios, into the skeletons of different carbonate producing organisms. In many areas these relationships are complex and there is often considerable local variability in the response of corals and trees, particularly in the growth rate related parameters. Prior to the instrumental period, the tree-ring index compiled by (Gray et al., 2004, GRL,31) has been taken as the principal reconstruction of the AMO. While most of the marine records examined appear to correlate with the tree-ring record during the instrumental period, there are significant discrepancies prior to 1850. This raises many questions about the stationarity and persistence of the AMO and the suitability of individual archives such as tree rings for these modes.

  20. Hydrogen isotope ratios of recent lacustrine sedimentary n-alkanes record modern climate variability

    NASA Astrophysics Data System (ADS)

    Sachse, D.; Radke, J.; Gleixner, G.

    2004-12-01

    Hydrogen isotope ratios were measured on n-alkanes (n-C 12 to n-C 31) extracted from recent lake surface sediments along a N-S European transect to test if modern climate variability is recorded in these biomarkers. δD values of the n-alkanes are compared to δD values of meteoric water from the IAEA-GNIP database spanning a range from -119‰ in northern Sweden to -41‰ in southern Italy, to lake water δD values, and to mean annual temperatures, varying between -2.0°C in the north and 13.7°C in the south. δD values of the short-chained n-alkanes n-C 12 to n-C 20, excluding algal derived n-C 17 and n-C 19, are higher in the north and lower in the south. The isotopic fractionation ɛ for hydrogen between meteoric water and the short-chained n-alkanes is increasing from N to S by more than 100‰ and is significantly correlated to mean annual temperature for n-C 16 and n-C 18. This suggests that these n-alkanes may originate from a different source in the northern lakes, possibly due to petroleum contamination, or are synthesized using a different biochemical pathway. The n-C 17 and n-C 19 alkanes of algal origin, the n-C 21 and n-C 23 alkanes originating from water plants, and the long-chain n-alkanes n-C 25, n-C 27, n-C 29, and n-C 31 of terrestrial origin, clearly correlate with δD values of meteoric water, lake water, and mean annual temperature, indicating that they excellently record the δD value of meteoric water. The mean hydrogen isotope fractionation ɛ C17/w of -157‰ (SD = 13) between n-C 17 and meteoric water is fairly constant over the wide range of different climates and lake environments, suggesting only minor influence of environmental factors on this biochemical fractionation. This suggests that δD values of n-C 17 are suitable to reconstruct the isotopic composition of source water. The mean fractionation between the long-chain n-alkanes and water is -128‰ (SD = 12). The mean difference of 31‰ between both ɛ values is likely due to

  1. Late Holocene Lacustrine Records of Climate and Vegetation Change From Southernmost South America

    NASA Astrophysics Data System (ADS)

    Moy, C. M.; Dunbar, R. B.; Francois, J.; Moreno, P. I.; Villa Martínez, R.

    2006-12-01

    The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere and has a major impact on the climate of southern South America as well as Southern Ocean hydrography. Southernmost South America is well-located to investigate past changes in the westerly winds because regional precipitation variability is controlled by the location and intensity of the wind field and it is the only landmass to extend within the core of the westerlies. Here we present late Holocene lacustrine records of climate change related to the westerlies from southern Patagonia, Chile. We focus on Lago Guanaco, a small hydrologically closed-basin lake in Southern Patagonia, and use stable isotope and pollen data from this site and three additional lakes in order to reconstruct changes in moisture balance related to the westerlies. Lago Guanaco (51°S, 72°W) is located close to the Nothofagus forest-Patagonian Steppe transition in the eastern region of Parque Nacional Torres del Paine. The location and composition of this important biological discontinuity is highly sensitive to the W-E precipitation gradient throughout Patagonia. The 4.75 m sediment core we obtained from the center of the lake has high concentrations of organic mater in addition to ostracodes and bivalves, which are relatively rare in Chilean Patagonia. Eleven AMS radiocarbon dates on organic and carbonate fractions indicate that the record spans the last ~14,400 cal yr BP and modern dates from core tops suggest little influence by old carbon sources. Changes in moisture balance and forest density/proximity are reflected in downcore variations in δ18Obivalve and δ18Oostracode, the Nothofagus/Poaceae paleovegetation index, and the C/N ratio of bulk decalcified organic matter. Combined, these variables document changes in the isotopic composition of the lake water, which largely reflect the isotopic composition of precipitation and the influence of evaporation, as well as shifts

  2. Global Snow Extent Climate Data Records and Trends Derived from Satellite Passive Microwave and Visible Data

    NASA Astrophysics Data System (ADS)

    Brodzik, M. J.; Savoie, M. H.; Armstrong, R. L.

    2008-12-01

    The extent and variability of seasonal snow cover are important parameters in climate and hydrologic systems due to effects on energy and moisture budgets. Northern Hemisphere snow cover extent, comprising about 98 percent of global seasonal snow cover, is the largest single spatial component of the cryosphere, with a mean maximum extent of 47 million square kilometers, nearly 50 percent of the land surface area. During the past four decades much important information on Northern Hemisphere snow extent has been provided by the NOAA weekly snow extent charts derived from visible-wavelength polar-orbiting and geostationary satellite imagery. NSIDC distributes these data as the Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 3. Since 1978, satellite passive microwave sensors have provided an independent source for snow monitoring, with the ability to penetrate clouds, provide data during darkness and the potential to provide an index of snow water equivalent. The historic microwave record spans a thirty year period and data are available from NSIDC as the Global EASE-Grid Monthly Snow Water Equivalent Climatology Product. Both data sets have been updated through spring, 2008. Trend analysis on the passive microwave record is complicated by the short overlap period of SMMR and SSM/I in 1987. To derive a consistent map of passive microwave snow cover, we examined the temporally closest overpasses from each sensor at selected targets and derived regression equations to cross-calibrate the sensors. Passive microwave snow algorithms have also consistently overestimated snow cover on the Tibet Plateau. We attribute the overmeasure to the use of algorithms that have assumed a thick atmosphere. These algorithms overmeasure snow extent when applied to very high elevation surfaces. We have derived an atmospheric correction to compensate for the influence of the reduced atmospheric thickness on snow extent estimates. Using the latest improvements to

  3. Mt. Logan Ice Core Record of North Pacific Holocene Climate Variability

    NASA Astrophysics Data System (ADS)

    Osterberg, E. C.; Mayewski, P. A.; Fisher, D. A.; Kreutz, K. J.; Handley, M. J.; Sneed, S. B.

    2006-12-01

    A >12,000 year-long, continuous, high-resolution (sub-annual to multi-decadal) ice core record from the summit plateau (5300 m asl) of Mt. Logan, Yukon, Canada, reveals large, abrupt fluctuations in North Pacific climate throughout the Holocene with a 1-2 ky periodicity. Co-registered major ion, trace element and stable isotope time series reveal a strong inverse relationship between precipitation δ18O and atmospheric seasalt and dust concentrations over multi-decadal to millennial periods (r<-0.6, p<0.0001). Intervals with depleted stable isotope ratios are associated with elevated concentrations of dust and seasalt aerosol at ca. 2.5, 4, 6.2, 7.5, 8.2, 9, and 10 k.y. B.P. Contrary to the traditional paleothermometric model of stable isotopes in ice cores, instrumental data and computer models suggest that stable isotopes on the summit of Mt. Logan represent changes in moisture source region between dominantly cold North Pacific waters (more zonal circulation; enriched stable isotope values) and warmer subtropical waters (more meridional circulation; depleted stable isotope values). Consequently, Holocene millennial-scale stable isotope fluctuations in the Mt. Logan core have a larger amplitude (6-9‰ for δ18O) than those found in Greenland and Canadian Arctic ice core records (e.g. 2-3‰ for GISP2 δ18O). Over the instrumental period (1948-1998), higher Mt. Logan dust concentrations are strongly associated with enhanced springtime cyclonic activity over East Asian desert source regions (r<-0.6, p<0.0001), which is characteristic of the La Niña atmospheric pressure pattern in the North Pacific. Mt. Logan seasalt aerosol concentrations are related to the wintertime strength of the Aleutian Low pressure center (r<-0.45, p<0.001). We use these calibrated proxy relationships to propose a conceptual model of North Pacific atmospheric circulation during the Holocene.

  4. Alkenone and Isotopic Records of Holocene Climatic and Environmental Change From Laminated West Greenland Lakes

    NASA Astrophysics Data System (ADS)

    D'Andrea, W. J.; Huang, Y.

    2004-12-01

    Long chain alkenones (LCAs) are a key class of biomarkers for paleotemperature reconstructions. These compounds are ubiquitous in ocean sediments, but rare in lake sediments. Here we report the first discovery of LCAs in a downcore profile and surface sediments of five Greenland lakes. The concentrations of LCAs in surface sediments of these lakes are one to two orders of magnitude higher than those reported previously in other lake surface sediments around the world. Alkenones are present in five Greenland lakes with elevated salinity, but absent from five freshwater lakes. The alkenones have exceptionally low \\delta13C values ranging from -40 to -43\\permil, and are depleted by 10 to 15\\permil relative to short-chain fatty acids and sterols within the same samples. These \\delta13C values are the lowest ever reported for alkenones in a natural setting and have important implications for tracing the alkenone producers in lakes. Using the published calibration for lake sediments, the alkenone unsaturation indices in the surface sediments of the Greenland lakes record late spring/early summer temperature when algal blooms occur, suggesting the applicability of lacustrine alkenones as a paleotemperature proxy. LCA unsaturation indices and \\deltaD from sediment cores taken from these Greenland lakes will help elucidate the environmental controls on these sedimentary parameters, and will aid the reconstruction of Holocene climate variability in West Greenland. Ongoing work on the saline lakes includes determining high resolution alkenone unsaturation ratios/abundances and bulk/compound-specific isotopic values from sediment cores, algal culturing, and establishing microbial community structure in the saline lakes using DNA/RNA fingerprinting. Up-to-date results will be presented in the meeting.

  5. Identifying the Holocene evolution of interannual climate variability in Southern California river runoff records.

    NASA Astrophysics Data System (ADS)

    Hendy, I. L.; Hinnov, L.; Brown, E. T.; Napier, T.

    2015-12-01

    Precipitation patterns in southern California are strongly correlated with El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) climate variability during the 20th Century. Heavy rainfall in southern California is generated by warm-wet storms associated with atmospheric rivers (ARs) producing flood events, while drought conditions occur when winter precipitation associated with north Pacific low pressure systems does not reach the region. Winter rainfall delivers siliciclastic sediment to Santa Barbara Basin (SBB), CA while spring summer marine productivity provides biogenic sediment resulting in a simple two component laminae couplet. Laminations are preserved in the low oxygen bottom of SBB providing a high temporal resolution paleoclimate record. Here we present scanning XRF generated annually resolved elemental concentrations for the last 9.5 ka in SBB from SPR0901-03KC (34°16.99'N; 120°2.408'W) and MV0811-14JPC (34°16.54'N; 120°2.10'W) in ~586 m water depth. High siliciclastic elemental counts are interpreted as indicating increased river runoff, while low values indicate droughts. Floods events indicative of extreme precipitation events occur throughout the Holocene, however long intervals between floods occur 8.5-7 Ka, 5.6-6.4 Ka and 0.8-1.1 Ka. Notable droughts occur 5.6-6.1, 4.7-5.1, 3.5-4.1, 2.6, 2.1, 1.8, 1.1 and 0.9 Ka. Spectral analysis indicates silicilastic elemental peaks are close to an annual resolution, however annual tuning increases the power of the interannual frequencies without changing the frequency appreciably. High frequency variability is lost during drought intervals.

  6. A comparison of the climates of the Medieval Climate Anomaly, Little Ice Age, and Current Warm Period reconstructed using coral records from the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Deng, Wenfeng; Liu, Xi; Chen, Xuefei; Wei, Gangjian; Zeng, Ti; Xie, Luhua; Zhao, Jian-xin

    2017-01-01

    For the global oceans, the characteristics of high-resolution climate changes during the last millennium remain uncertain because of the limited availability of proxy data. This study reconstructs climate conditions using annually resolved coral records from the South China Sea (SCS) to provide new insights into climate change over the last millennium. The results indicate that the climate of the Medieval Climate Anomaly (MCA, AD 900-1300) was similar to that of the Current Warm Period (CWP, AD 1850-present), which contradicts previous studies. The similar warmth levels for the MCA and CWP have also been recorded in the Makassar Strait of Indonesia, which suggests that the MCA was not warmer than the CWP in the western Pacific and that this may not have been a globally uniform change. Hydrological conditions were drier/saltier during the MCA and similar to those of the CWP. The drier/saltier MCA and CWP in the western Pacific may be associated with the reduced precipitation caused by variations in the Pacific Walker Circulation. As for the Little Ice Age (LIA, AD 1550-1850), the results from this study, together with previous data from the Makassar Strait, indicate a cold and wet period compared with the CWP and the MCA in the western Pacific. The cold LIA period agrees with the timing of the Maunder sunspot minimum and is therefore associated with low solar activity. The fresher/wetter LIA in the western Pacific may have been caused by the synchronized retreat of both the East Asian Summer Monsoon and the Australian Monsoon.

  7. Early and Mid-Holocene Climate Variability - A Multi-Proxy Approach from Multi-Millennial Tree Ring Records

    NASA Astrophysics Data System (ADS)

    Ziehmer, Malin Michelle; Nicolussi, Kurt; Schlüchter, Christian; Leuenberger, Markus

    2016-04-01

    Most reconstructions of Holocene climate variability in the Alps are based on low-frequency archives such as glacier and tree line fluctuations. However; recent finds of wood remains in glacier forefields in the Alps reveal a unique high-frequency archive allowing climate reconstruction over the entire Holocene. The evolution of Holocene climate can be reconstructed by using a multi-proxy approach combining tree ring width and multiple stable isotope chronologies by establishing highly resolved stable isotope records from calendar-dated wood which covers the past 9000 years b2k. Therefore, we collected samples in the Alps covering a large SW-NE transect, primarily in glacier forefields but also in peat bogs and small lakes. The multiple sample locations allow the analysis of climatic conditions along a climatic gradient characterized by the change from an Atlantic to a more continental climate. Subsequently, tree ring widths are measured and samples are calendrically dated by means of tree ring analysis. Due to the large amount of samples for stable isotope analysis (> 8000 samples to cover the entire Holocene by guaranteeing a sample replication of 4 samples per time unit of 5 years), dated wood samples are separated into 5-year tree ring blocks. These blocks are sliced and the cellulose is extracted after a standardized procedure and crushed by ultrasonic homogenization. In order to establish multi-proxy records, the stable isotopes of carbon, oxygen and hydrogen are simultaneously measured. Both the 5-year tree ring width and multiple stable isotope series offer new insights into the Early and Mid-Holocene climate and its variability in the Alps. The stable isotope records reveal interesting low-frequency variability. But they also display expected offsets caused by the measurement of individual trees revealing effects of sampling site, tree species and growth trend. These effects offer an additional insight into the tree growth and stand behavior of single

  8. Climatic changes in the northern Red Sea during the last 22,000 years as recorded by calcareous nannofossils

    NASA Astrophysics Data System (ADS)

    Legge, Heiko Lars; Mutterlose, JöRg; Arz, Helge W.

    2006-03-01

    We present a high-resolution record of calcareous nannofossils from the northern Red Sea for the last 22 kyr. Extreme conditions with enhanced salinities during the Last Glacial Maximum are characterized by high values of Gephyrocapsa ericsonii. The dominance of Emiliania huxleyi in Heinrich event 1 indicates a climatic cooling favoring the bloom of opportunistic species. The calcareous nannofossils record a two-step onset of the postglacial humid climate, punctuated by the Younger Dryas. Both steps show an early oligotrophic phase dominated by Florisphaera profunda and Gladiolithus flabellatus and a subsequent fertile phase characterized by E. huxleyi. The Younger Dryas is described by high values of Gephyrocapsa oceanica, indicating an increased mixing of the water column. In the late Holocene, repetitive increases in abundance of F. profunda and G. flabellatus reflect restricted oligotrophic conditions, caused by the high aridity following the Holocene humid period.

  9. Peeking Under the Ice… Literally: Records of Arctic Climate Change from Radiocarbon Dating Moss Emerging from Beneath Retreating Glaciers

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; Schweinsberg, A.; Miller, G. H.; Lifton, N. A.; Beel, C. R.; Bennike, O.

    2014-12-01

    Dramatic changes are taking place throughout the Arctic. Many glaciers have already melted away completely, and most others are well on their way as rising snowline elevations promise continued glacier retreat. Emerging from beneath retreating glacier margins is a landscape rich in information about past climate and glacier changes. Within newly exposed bedrock is an inventory of cosmogenic nuclides that archive past ice cover timing and duration. Lake basins re-appearing due to retreating ice preserve sediment archives that tell of cooling climate and advancing ice. And ancient surfaces vegetated with tundra communities that have long been entombed beneath frozen-bedded ice caps are now being revealed for the first time in millennia. This presentation will focus on the climate and glacier record derived from radiocarbon dating of in situ moss recently exhumed from retreating local ice cap margins on western Greenland. Dozens of radiocarbon ages from moss group into several distinct modes, which are interpreted as discrete times of persistent summer cooling and resultant glacier expansion. The data reveal a pattern of glacier expansion beginning ~5000 years ago, followed by periods of glacier growth around 3500 and 1500 years ago. Because these times of glacier expansion are recorded at many sites in western Greenland and elsewhere in the Arctic, they are interpreted as times of step-wise summer cooling events during the Holocene. These non-linear climate changes may be a result of feedbacks that amplify linear insolation forcing of Holocene climate. In addition to these insights into the Arctic climate system, the antiquity of many radiocarbon ages of ice-killed moss indicate that many arctic surfaces are being re-exposed for the first time in millennia due to retreating ice, emphasizing the unprecedented nature of current summer warming.

  10. Mid-Burdigalian Paratethyan alkenone record reveals link between orbital forcing, Antarctic ice-sheet dynamics and European climate at the verge to Miocene Climate Optimum

    NASA Astrophysics Data System (ADS)

    Grunert, Patrick; Tzanova, Alexandrina; Harzhauser, Mathias; Piller, Werner E.

    2014-12-01

    The Early Ottnangian Cooling (EOC), a distinct cold-spell in European climate at ~ 18 Ma preceding the Miocene Climate Optimum, is frequently reported in Paratethys records; however, the duration, magnitude, and underlying causes are poorly understood. A new palaeoclimatic data-set provides unexpected insights into this event. UK'37-based sea-surface temperatures > 24 °C between ~ 18.1 and 17.7 Myrs substantially exceed existing estimates, and indicate a significantly warmer European climate than previously assumed for this usually poorly recovered time interval. The EOC is expressed as an average drop of 2-3 °C in Paratethyan water temperatures between ~ 18.1 and 17.8 Myrs with two distinct cold snaps at ~ 17.86 Ma and ~ 17.81 Ma. The short duration of the EOC excludes Tethyan Seaway closure as its underlying cause, although the enhanced palaeoclimatic sensitivity of the Paratethys due to this palaeogeographic configuration potentially contributed to the magnitude of SST deterioration during the EOC. The revealed palaeoclimatic pattern shows a strong correlation with isotope event Mi-1b in deep-sea δ18O records, and we propose a tight palaeoclimatic link between the Southern Ocean and the Paratethys/Mediterranean realm as an alternative hypothesis. The interplay of modulations in the long-term (~ 400 kyrs) and short-term (~ 100 kyrs) eccentricity cycles most likely acted as pacemaker of this palaeoclimatic interaction.

  11. Integrating satellite observations and modern climate measurements with the recent sedimentary record: An example from Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Addison, Jason A.; Finney, Bruce P.; Jaeger, John M.; Stoner, Joseph S.; Norris, Richard D.; Hangsterfer, Alexandra

    2013-07-01

    Assessments of climate change over time scales that exceed the last 100 years require robust integration of high-quality instrument records with high-resolution paleoclimate proxy data. In this study, we show that the recent biogenic sediments accumulating in two temperate ice-free fjords in Southeast Alaska preserve evidence of North Pacific Ocean climate variability as recorded by both instrument networks and satellite observations. Multicore samples EW0408-32MC and EW0408-43MC were investigated with 137Cs and excess 210Pb geochronometry, three-dimensional computed tomography, high-resolution scanning XRF geochemistry, and organic stable isotope analyses. EW0408-32MC (57.162°N, 135.357°W, 146 m depth) is a moderately bioturbated continuous record that spans AD ˜1930-2004. EW0408-43MC (56.965°N, 135.268°W, 91 m depth) is composed of laminated diatom oozes, a turbidite, and a hypopycnal plume (river flood) deposit. A discontinuous event-based varve chronology indicates 43MC spans AD ˜1940-1981. Decadal-scale fluctuations in sedimentary Br/Cl ratios accurately reflect changes in marine organic matter accumulation that display the same temporal pattern as that of the Pacific Decadal Oscillation. An estimated Sitka summer productivity parameter calibrated using SeaWiFS satellite observations support these relationships. The correlation of North Pacific climate regime states, primary productivity, and sediment geochemistry indicate the accumulation of biogenic sediment in Southeast Alaska temperate fjords can be used as a sensitive recorder of past productivity variability, and by inference, past climate conditions in the high-latitude Gulf of Alaska.

  12. Plant-wax D/H ratios in the southern European Alps record multiple aspects of climate variability

    NASA Astrophysics Data System (ADS)

    Wirth, Stefanie B.; Sessions, Alex L.

    2016-09-01

    We present a Younger Dryas-