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1.
Climate Change During the Last Deglaciation in Antarctica 总被引：1，自引：0，他引：1
PA Mayewski MS Twickler SI Whitlow LD Meeker Q Yang J Thomas K Kreutz PM Grootes DL Morse EJ Steig ED Waddington ES Saltzman P Whung KC Taylor 《Science (New York, N.Y.)》1996,272(5268):1636-1638
Greenland ice core records provide clear evidence of rapid changes in climate in a variety of climate indicators. In this work, rapid climate change events in the Northern and Southern hemispheres are compared on the basis of an examination of changes in atmospheric circulation developed from two ice cores. High-resolution glaciochemical series, covering the period 10,000 to 16,000 years ago, from a central Greenland ice core and a new site in east Antarctica display similar variability. These findings suggest that rapid climate change events occur more frequently in Antarctica than previously demonstrated. 相似文献
2.
Mayewski PA Meeker LD Whitlow S Twickler MS Morrison MC Bloomfield P Bond GC Alley RB Gow AJ Meese DA Grootes PM Ram M Taylor KC Wumkes W 《Science (New York, N.Y.)》1994,263(5154):1747-1751
High-resolution, continuous multivariate chemical records from a central Greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41,000 years. These chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to Greenland [defined here as the polar circulation index (PCI)] and in the extent of ocean ice cover. Massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in PCI. During stadials without discharge events, ocean ice cover appears to reach some common maximum level. The massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling. 相似文献
3.
800,000 years of abrupt climate variability 总被引：1，自引：0，他引：1
Barker S Knorr G Edwards RL Parrenin F Putnam AE Skinner LC Wolff E Ziegler M 《Science (New York, N.Y.)》2011,334(6054):347-351
We constructed an 800,000-year synthetic record of Greenland climate variability based on the thermal bipolar seesaw model. Our Greenland analog reproduces much of the variability seen in the Greenland ice cores over the past 100,000 years. The synthetic record shows strong similarity with the absolutely dated speleothem record from China, allowing us to place ice core records within an absolute timeframe for the past 400,000 years. Hence, it provides both a stratigraphic reference and a conceptual basis for assessing the long-term evolution of millennial-scale variability and its potential role in climate change at longer time scales. Indeed, we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the Middle to Late Pleistocene. 相似文献
4.
Willerslev E Cappellini E Boomsma W Nielsen R Hebsgaard MB Brand TB Hofreiter M Bunce M Poinar HN Dahl-Jensen D Johnsen S Steffensen JP Bennike O Schwenninger JL Nathan R Armitage S de Hoog CJ Alfimov V Christl M Beer J Muscheler R Barker J Sharp M Penkman KE Haile J Taberlet P Gilbert MT Casoli A Campani E Collins MJ 《Science (New York, N.Y.)》2007,317(5834):111-114
It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections. 相似文献
5.
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 B?lling 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. 相似文献
6.
Koerner RM 《Science (New York, N.Y.)》1989,244(4907):964-968
Evidence from ice at the bottom of ice cores from the Canadian Arctic Islands and Camp Century and Dye-3 in Greenland suggests that the Greenland ice sheet melted extensively or completely during the last interglacial period more than 100 ka (thousand years ago), in contrast to earlier interpretations. The presence of dirt particles in the basal ice has previously been thought to indicate that the base of the ice sheets had melted and that the evidence for the time of original growth of these ice masses had been destroyed. However, the particles most likely blew onto the ice when the dimensions of the ice caps and ice sheets were much smaller. Ice texture, gas content, and other evidence also suggest that the basal ice at each drill site is superimposed ice, a type of ice typical of the early growth stages of an ice cap or ice sheet. If the present-day ice masses began their growth during the last interglacial, the ice sheet from the earlier (Illinoian) glacial period must have competely or largely melted during the early part of the same interglacial period. If such melting did occur, the 6-meter higher-than-present sea level during the Sangamon cannot be attributed to disintegration of the West Antarctic ice sheet, as has been suggested. 相似文献
7.
Proxies from Greenland ice cores and North Atlantic marine sediment cores document repeated extreme climate swings of a few decades to millennia during the last glacial cycle, including periods of intense ice rafting called Heinrich events (HEs). We have found similar oxygen isotope variations recorded in mixed-layer-and thermocline-dwelling planktonic foraminifera during HEs 0, 1, and 4, suggesting that three foraminiferal taxa calcified their shells at similar temperatures in a homogenized upperwater column. This implies that the surface mixed layer was deeper during HEs. Similar deepening occurred on the northern margin of the ice-rafted-debris belt, implying that these deep mixed layers during HEs were widespread in the region. We suggest that an increase in storminess during HEs intensified the vertical mixing of meltwater from ice rafting in the upper ocean. 相似文献
8.
Hughen K Lehman S Southon J Overpeck J Marchal O Herring C Turnbull J 《Science (New York, N.Y.)》2004,303(5655):202-207
A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation. 相似文献
9.
Field observations on northeast Ellesmere Island indicate that the maximum advance of the northwest Greenland Ice Sheet was about 100 kilometers beyond its present margin. This occurred before the outermost Ellesmere Island ice advance, which took place more than 30,000 years before present (B.P.). Recession from the Ellesmere Island ice margin began at least 28,000 to 30,000 and possibly more than 35,000 years B.P. During this sequence of glacial events, significant land areas remained free of ice. The late Wisconsin ice extent along both northeast Ellesmere Island and northwest Greenland was extremely limited, leaving an ice-free corridor along Kennedy and Robeson channels. Recession from these ice margins is indicated by initial postglacial emergence around 8100 to 8400 years B.P. The relatively minor extent of late Wisconsin ice in the High Arctic probably reflects a period of extreme aridity occasioned by the buildup of the Laurentide Ice Sheet to the south. 相似文献
10.
A 0.5-million-year record of millennial-scale climate variability in the north atlantic 总被引：8，自引：0，他引：8
Long, continuous, marine sediment records from the subpolar North Atlantic document the glacial modulation of regional climate instability throughout the past 0.5 million years. Whenever ice sheet size surpasses a critical threshold indicated by the benthic oxygen isotope (delta18O) value of 3.5 per mil during each of the past five glaciation cycles, indicators of iceberg discharge and sea-surface temperature display dramatically larger amplitudes of millennial-scale variability than when ice sheets are small. Sea-surface temperature oscillations of 1 degrees to 2 degreesC increase in size to approximately 4 degrees to 6 degreesC, and catastrophic iceberg discharges begin alternating repeatedly with brief quiescent intervals. The glacial growth associated with this amplification threshold represents a relatively small departure from the modern ice sheet configuration and sea level. Instability characterizes nearly all observed climate states, with the exception of a limited range of baseline conditions that includes the current Holocene interglacial. 相似文献
11.
EJ Steig EJ Brook JWC White CM Sucher ML Bender SJ Lehman DL Morse ED Waddington GD Clow 《Science (New York, N.Y.)》1998,282(5386):92-95
Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres. 相似文献
12.
KH Kjær SA Khan NJ Korsgaard J Wahr JL Bamber R Hurkmans M van den Broeke LH Timm KK Kjeldsen AA Bjørk NK Larsen LT Jørgensen A Færch-Jensen E Willerslev 《Science (New York, N.Y.)》2012,337(6094):569-573
Global warming is predicted to have a profound impact on the Greenland Ice Sheet and its contribution to global sea-level rise. Recent mass loss in the northwest of Greenland has been substantial. Using aerial photographs, we produced digital elevation models and extended the time record of recent observed marginal dynamic thinning back to the mid-1980s. We reveal two independent dynamic ice loss events on the northwestern Greenland Ice Sheet margin: from 1985 to 1993 and 2005 to 2010, which were separated by limited mass changes. Our results suggest that the ice mass changes in this sector were primarily caused by short-lived dynamic ice loss events rather than changes in the surface mass balance. This finding challenges predictions about the future response of the Greenland Ice Sheet to increasing global temperatures. 相似文献
13.
Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13 总被引：2，自引：0，他引：2
Burns SJ Fleitmann D Matter A Kramers J Al-Subbary AA 《Science (New York, N.Y.)》2003,301(5638):1365-1367
Oxygen-isotope ratios of a stalagmite from Socotra Island in the Indian Ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present. The pattern of precipitation bears a striking resemblance to the oxygen-isotope record from Greenland ice cores, with increased tropical precipitation associated with warm periods in the high northern latitudes. The largest change, at the onset of interstadial 12, occurred very rapidly, in about 25 years. The chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period. 相似文献
14.
340,000-year centennial-scale marine record of Southern Hemisphere climatic oscillation 总被引：1，自引：0，他引：1
In order to investigate rapid climatic changes at mid-southern latitudes, we have developed centennial-scale paleoceanographic records from the southwest Pacific that enable detailed comparison with Antarctic ice core records. These records suggest close coupling of mid-southern latitudes with Antarctic climate during deglacial and interglacial periods. Glacial sections display higher variability than is seen in Antarctic ice cores, which implies climatic decoupling between mid- and high southern latitudes due to enhanced circum-Antarctic circulation. Structural and temporal similarity with the Greenland ice core record is evident in glacial sections and suggests a degree of interhemispheric synchroneity not predicted from bipolar ice core correlations. 相似文献
15.
It has been widely hypothesized that a warmer climate in Greenland would increase the volume of lubricating surface meltwater reaching the ice-bedrock interface, accelerating ice flow and increasing mass loss. We have assembled a data set that provides a synoptic-scale view, spanning ice-sheet to outlet-glacier flow, with which to evaluate this hypothesis. On the ice sheet, these data reveal summer speedups (50 to 100%) consistent with, but somewhat larger than, earlier observations. The relative speedup of outlet glaciers, however, is far smaller (<15%). Furthermore, the dominant seasonal influence on Jakobshavn Isbrae's flow is the calving front's annual advance and retreat. With other effects producing outlet-glacier speedups an order of magnitude larger, seasonal melt's influence on ice flow is likely confined to those regions dominated by ice-sheet flow. 相似文献
16.
Dust concentrations in ice of the last glacial maximum (LGM) are high in ice cores from Greenland and Antarctica. The magnitude of the enhancements can be explained if the strength of the hydrologic cycle during the LGM was about half of that at present. This notion is consistent with a large decrease (5 degrees Celsius) in ocean temperature during the LGM, as recently deduced from measurements of strontium and calcium in corals. 相似文献
17.
Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period 总被引：2，自引：0，他引：2
A precise relative chronology for Greenland and West Antarctic paleotemperature is extended to 90,000 years ago, based on correlation of atmospheric methane records from the Greenland Ice Sheet Project 2 and Byrd ice cores. Over this period, the onset of seven major millennial-scale warmings in Antarctica preceded the onset of Greenland warmings by 1500 to 3000 years. In general, Antarctic temperatures increased gradually while Greenland temperatures were decreasing or constant, and the termination of Antarctic warming was apparently coincident with the onset of rapid warming in Greenland. This pattern provides further evidence for the operation of a "bipolar see-saw" in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales. 相似文献
18.
Rapid changes in the hydrologic cycle of the tropical Atlantic during the last glacial 总被引：1，自引：0，他引：1
Sedimentary time series of color reflectance and major element chemistry from the anoxic Cariaco Basin off the coast of northern Venezuela record large and abrupt shifts in the hydrologic cycle of the tropical Atlantic during the past 90,000 years. Marine productivity maxima and increased precipitation and riverine discharge from northern South America are closely linked to interstadial (warm) climate events of marine isotope stage 3, as recorded in Greenland ice cores. Increased precipitation at this latitude during interstadials suggests the potential for greater moisture export from the Atlantic to Pacific, which could have affected the salinity balance of the Atlantic and increased thermohaline heat transport to high northern latitudes. This supports the notion that tropical feedbacks played an important role in modulating global climate during the last glacial period. 相似文献
19.
One thousand centuries of climatic record from cAMP century on the greenland ice sheet 总被引：1，自引：0，他引：1
A correlation of time with depth has been evaluated for the Camp Century, Greenland, 1390 meter deep ice core. Oxygen isotopes in approximately 1600 samples throughout the core have been analyzed. Long-term variations in the isotopic composition of the ice reflect the climatic changes during the past nearly 100,000 years. Climatic oscillations with periods of 120, 940, and 13,000 years are observed. 相似文献
20.
A new greenland deep ice core 总被引：1，自引：0，他引：1
Dansgaard W Clausen HB Gundestrup N Hammer CU Johnsen SF Kristinsdottir PM Reeh N 《Science (New York, N.Y.)》1982,218(4579):1273-1277
The polar ice sheets are rich sources of information on past atmospheric conditions, including paleoclimates. A new deep ice core has been drilled in south Greenland. Comparison of the oxygen isotopic profile with that from camp Century and with a deep-sea foraminifera record indicates that the new core reaches back to about 90,000 years before present in a continuous sequence. The details in the Wisconsin part of the ice core records seem to be climatically, significant, and the general trends reveal all of the relevant Emiliani stages recorded in deep-sea cores. The redated Camp Century record suggests a dramatic termination of the Eem/Sangamon interglacial. 相似文献