Ice Sheets Research Papers - Academia.edu (original) (raw)

2005, Science

We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 +/- 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 104- to 106-year scale, but a link between oxygen isotope and sea level on the 107-year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).

2009, Proceedings of the National Academy of Sciences

The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450 -600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the ''dust bowl'' era and inexorable sea level rise. Thermal expansion of the warming ocean provides a conservative lower limit to irreversible global average sea level rise of at least 0.4 -1.0 m if 21st century CO 2 concentrations exceed 600 ppmv and 0.6 -1.9 m for peak CO 2 concentrations exceeding Ϸ1,000 ppmv. Additional contributions from glaciers and ice sheet contributions to future sea level rise are uncertain but may equal or exceed several meters over the next millennium or longer.

2010, Nature

The rise in Arctic near-surface air temperatures has been almost twice as large as the global average in recent decades 1-3 -a feature known as 'Arctic amplification'. Increased concentrations of atmospheric greenhouse gases have driven Arctic and global average warming 1,4 ; however, the underlying causes of Arctic amplification remain uncertain. The roles of reductions in snow and sea ice cover 5-7 and changes in atmospheric and oceanic circulation 8-10 , cloud cover and water vapour 11,12 are still matters of debate. A better understanding of the processes responsible for the recent amplified warming is essential for assessing the likelihood, and impacts, of future rapid Arctic warming and sea ice loss 13,14 . Here we show that the Arctic warming is strongest at the surface during most of the year and is primarily consistent with reductions in sea ice cover. Changes in cloud cover, in contrast, have not contributed strongly to recent warming. Increases in atmospheric water vapour content, partly in response to reduced sea ice cover, may have enhanced warming in the lower part of the atmosphere during summer and early autumn. We conclude that diminishing sea ice has had a leading role in recent Arctic temperature amplification. The findings reinforce suggestions that strong positive ice-temperature feedbacks have emerged in the Arctic 15 , increasing the chances of further rapid warming and sea ice loss, and will probably affect polar ecosystems, ice-sheet mass balance and human activities in the Arctic 2 .

2004, Quaternary Science Reviews

The maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (>140 ka), (2) the Early Weichselian (100-80 ka), (3) the Middle Weichselian (60-50 ka) and (4) the Late Weichselian (25-15 ka). The reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in Russia and Siberia, and with marine seismic-and sediment core data. The Barents-Kara Ice Sheet got progressively smaller during each glaciation, whereas the dimensions of the Scandinavian Ice Sheet increased. During the last Ice Age the Barents-Kara Ice Sheet attained its maximum size as early as 90-80,000 years ago when the ice front reached far onto the continent. A regrowth of the ice sheets occurred during the early Middle Weichselian, culminating about 60-50,000 years ago. During the Late Weichselian the Barents-Kara Ice Sheet did not reach the mainland east of the Kanin Peninsula, with the exception of the NW fringe of Taimyr. A numerical ice-sheet model, forced by global sea level and solar changes, was run through the full Weichselian glacial cycle. The modeling results are roughly compatible with the geological record of ice growth, but the model underpredicts the glaciations in the ARTICLE IN PRESS

1996, Nature

AT the base of the Earth's mantle is a region, called D", which serves as a thermal and chemical boundary layer between the silicate mantle and the liquid-iron outer corelJ. Tomographic models of mantle compressional-wave velocity (vp) have their worst resolution in D", owing to limited ray samplinC5, but have hinted at large-scale lateral variations there. Here I use a new technique, which has its greatest resolution within D", to produce

2011, Geophysical Research Letters

2000, Science

The deep-sea sediment oxygen isotopic composition (␦ 18 O) record is dominated by a 100,000-year cyclicity that is universally interpreted as the main ice-age rhythm. Here, the ice volume component of this ␦ 18 O signal was extracted by using the record of ␦ 18 O in atmospheric oxygen trapped in Antarctic ice at Vostok, precisely orbitally tuned. The benthic marine ␦ 18 O record is heavily contaminated by the effect of deep-water temperature variability, but by using the Vostok record, the ␦ 18 O signals of ice volume, deep-water temperature, and additional processes affecting air ␦ 18 O (that is, a varying Dole effect) were separated. At the 100,000-year period, atmospheric carbon dioxide, Vostok air temperature, and deep-water temperature are in phase with orbital eccentricity, whereas ice volume lags these three variables. Hence, the 100,000-year cycle does not arise from ice sheet dynamics; instead, it is probably the response of the global carbon cycle that generates the eccentricity signal by causing changes in atmospheric carbon dioxide concentration.

1993, Paleoceanography

Climate over the past million years has been dominated by glaciation cycles with periods near 23,000, 41,000, and 100,000 years. In a linear version of the Milankovitch theory, the two shorter cycles can be explained as responses to insolation cycles driven by precession and obliquity. But the 100,000-year radiation cycle (arising from eccentricity variation) is much too small in amplitude and too late in phase to produce the corresponding climate cycle by direct forcing. We present phase observations showing that the geographic progression of local responses over the 100,000-year cycle is similar to the progression in the other two cycles, implying that a similar set of internal climatic mechanisms operates in all three. But the phase sequence in the 100,000-year cycle requires a source of climatic inertia having a time constant (--15,000 years) much larger than the other cycles (--5,000 years). Our conceptual model identifies massive northern hemisphere ice sheets as this larger inertial source. When these ice sheets, forced by precession and obliquity, exceed a critical size, they cease responding as linear Milankovitch slaves and drive atmospheric and oceanic responses that mimic the externally forced responses. In our model, the coupled system acts as a nonlinear amplifier that is particularly sensitive to eccentricity-driven modulations in the 23,000-year sea level cycle. During an interval when sea level is forced upward from a major low stand by a Milankovitch response acting either alone or in combination with an internally driven, higher-frequency process, ice sheets grounded on continental shelves become unstable, mass wasting accelerates, and the resulting deglaciation sets the phase of one wave in the train of 100,000-year oscillations.

2002, Journal of Geodynamics

2008, Quaternary Science Reviews

We synthesize palaeoclimate records from the mid-latitude arid Asian region dominated today by the Westerlies (''arid central Asia'' (ACA)) to evaluate spatial and temporal patterns of moisture changes during the Holocene. Sediment records from 11 lakes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five-class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200-year time slices. The proxies used in these records include pollen and diatom assemblages, sediment lithology, lake levels, and geochemistry (mainly isotope) data. The results of our synthesis show that ACA as a whole experienced synchronous and coherent moisture changes during the Holocene, namely a dry early Holocene, a wetter (less dry) early to mid-Holocene, and a moderately wet late Holocene. During the early Holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka (1 ka ¼ 1000 cal a BP). Hence the effective-moisture history in ACA is out-of-phase with that in monsoonal Asia as documented by numerous palaeoclimate records. In monsoonal Asia, a strong summer monsoon and humid climate characterized the early Holocene, and a weakened summer monsoon and drier climate prevailed during the late Holocene, which were mainly controlled by changes in low-latitude summer insolation. In contrast, we propose that the pattern of Holocene effective-moisture evolution in the westerly dominated ACA was mainly determined by North Atlantic sea-surface temperatures (SSTs) and high-latitude air temperatures that affect the availability, amount and transport of water vapor. Also, topography of the Tibetan Plateau and adjacent Asian highlands could have contributed to the intensification of dry climate in ACA during the early Holocene, as a result of strengthening the subsidence of dry air masses, associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation. Summer insolation might have played a key role in directly controlling moisture conditions in ACA but only after the northern hemisphere ice-sheets had disappeared in the mid-and late Holocene. r

1998, Earth and Planetary Science Letters

2009, Science

Mass budget calculations, validated with satellite gravity observations [from the Gravity Recovery and Climate Experiment (GRACE) satellites], enable us to quantify the individual components of recent Greenland mass loss. The total 2000-2008 mass loss of~1500 gigatons, equivalent to 0.46 millimeters per year of global sea level rise, is equally split between surface processes (runoff and precipitation) and ice dynamics. Without the moderating effects of increased snowfall and refreezing, post-1996 Greenland ice sheet mass losses would have been 100% higher. Since 2006, high summer melt rates have increased Greenland ice sheet mass loss to 273 gigatons per year (0.75 millimeters per year of equivalent sea level rise). The seasonal cycle in surface mass balance fully accounts for detrended GRACE mass variations, confirming insignificant subannual variation in ice sheet discharge.

2006, Quaternary Science Reviews

The emergence of low-frequency, high-amplitude, quasi-periodic ($100-kyr) glacial variability during the middle Pleistocene in the absence of any significant change in orbital forcing indicates a fundamental change internal to the climate system. This middle Pleistocene transition (MPT) began 1250 ka and was complete by 700 ka. Its onset was accompanied by decreases in sea surface temperatures (SSTs) in the North Atlantic and tropical-ocean upwelling regions and by an increase in African and Asian aridity and monsoonal intensity. During the MPT, long-term average ice volume gradually increased by 50msea−levelequivalent,whereaslowfrequencyice−volumevariabilityexperienceda100−kyrlullcenteredon1000kafollowedbyitsreappearance50 m sea-level equivalent, whereas lowfrequency ice-volume variability experienced a 100-kyr lull centered on 1000 ka followed by its reappearance 50msea−levelequivalent,whereaslowfrequencyice−volumevariabilityexperienceda100−kyrlullcenteredon1000kafollowedbyitsreappearance900 ka, although as a broad band of power rather than a narrow, persistent 100-kyr cycle. Additional changes at 900 ka indicate this to be an important time during the MPT, beginning with an 80-kyr event of extreme SST cooling followed by the partial recovery and subsequent stabilization of long-term North Atlantic and tropical ocean SSTs, increasing Southern Ocean SST variability primarily associated with warmer interglacials, the loss of permanent subpolar sea-ice cover, and the emergence of low-frequency variability in Pacific SSTs and global deep-ocean circulation. Since 900 ka, ice sheets have been the only component of the climate system to exhibit consistent low-frequency variability. With the exception of a near-universal organization of low-frequency power associated with marine isotope stages 11 and 12, all other components show an inconsistent distribution of power in frequency-time space, suggesting a highly nonlinear system response to orbital and ice-sheet forcing.

2009

Th-dated oxygen isotope records of stalagmites from Sanbao Cave, China, characterize Asian Monsoon (AM) precipitation through the ends of the third-and fourthmost recent ice ages. As a result, AM records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments, establishing the timing and sequence of major events. In all four cases, observations are consistent with a classic Northern Hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets. Meltwater and icebergs entering the North Atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon, causing increases in atmospheric CO 2 and Antarctic temperatures that drive the termination in the Southern Hemisphere. Increasing CO 2 and summer insolation drive recession of northern ice sheets, with probable positive feedbacks between sea level and CO 2 .

1999, Marine Geology

Based on the study of 10 sediment cores and 40 core-top samples from the South China Sea (SCS) we obtained proxy records of past changes in East Asian monsoon climate on millennial to bidecadal time scales over the last 220,000 years. Climate proxies such as global sea level, estimates of paleotemperature, salinity, and nutrients in surface water, ventilation of deep water, paleowind strength, freshwater lids, fluvial and=or eolian sediment supply, and sediment winnowing on the sea floor were derived from planktonic and benthic stable-isotope records, the distribution of siliciclastic grain sizes, planktonic foraminifera species, and the U K 37 biomarker index. Four cores were AMS-14 C-dated. Two different regimes of monsoon circulation dominated the SCS over the last two glacial cycles, being linked to the minima and maxima of Northern Hemisphere solar insolation. (1) Glacial stages led to a stable estuarine circulation and a strong O 2 -minimum layer via a closure of the Borneo sea strait. Strong northeast monsoon and cool surface water occurred during winter, in part fed by an inflow from the north tip of Luzon. In contrast, summer temperatures were as high as during interglacials, hence the seasonality was strong. Low wetness in subtropical South China was opposed to large river input from the emerged Sunda shelf, serving as glacial refuge for tropical forest. (2) Interglacials were marked by a strong inflow of warm water via the Borneo sea strait, intense upwelling southeast of Vietnam and continental wetness in China during summer, weaker northeast monsoon and high sea-surface temperatures during winter, i.e. low seasonality. On top of the long-term variations we found millennial-to centennial-scale cold and dry, warm and humid spells during the Holocene, glacial Terminations I and II, and Stage 3. The spells were coeval with published variations in the Indian monsoon and probably, with the cold Heinrich and warm Dansgaard-Oeschger events recorded in Greenland ice cores, thus suggesting global climatic teleconnections. Holocene oscillations in the runoff from South China centered around periodicities of 775 years, ascribed to subharmonics of the 1500-year cycle in oceanic thermohaline circulation. 102=84-year cycles are tentatively assigned to the Gleissberg period of solar activity. Phase relationships among various monsoon proxies near the onset of Termination IA suggest that summer-monsoon rains and fluvial runoff from South China had already intensified right after the last glacial maximum (LGM) insolation minimum, coeval with the start of Antarctic ice melt Ł Corresponding author. Present address: : S 0 0 2 5 -3 2 2 7 ( 9 8 ) 0 0 1 8 2 -0 246 L. Wang et al. / Marine Geology 156 (1999) prior to the δ 18 O signals of global sea-level rise. Vice versa, the strength of winter-monsoon winds decreased in short centennial steps only 3000-4000 years later, along with the melt of glacial ice sheets in the Northern Hemisphere.

2001, Journal of Geophysical Research

2002, Quaternary Science Reviews

The Late Wisconsinan advance of the Laurentide

2004, Geophysical Research Letters

2009, Geophysical Research Letters

1996, Climate Dynamics

Abstract. Previously published results suggest that the strength of the SW Indian Monsoon can vary signifi- cantly on century- to millenium time scales, an obser- vation that has important implications for assessments of future climate... more

2004, Quaternary Science Reviews

Relative sea-level change along the Italian coast and adjacent seas-the combined result of eustasy, glacio-hydro-isostasy and vertical tectonic motion-exhibits considerable spatial and temporal variability throughout the Holocene. The tectonic contribution can be evaluated from the elevation of MIS 5.5 shoreline-markers that are well developed in many localities and the eustatic and isostatic contributions can be predicted from models of ice sheets and earth rheology. Discrepancies between observed Holocene sea levels and model predicted values provide the information for refining the model parameters, including the tectonic rates of vertical movement. Recent and new Holocene and MIS 5.5 information from 30 sites in Italy has been evaluated and compared with model results to calibrate the predictive model. The resulting parameters for the earth rheology and for the eustatic (ice-volume equivalent) sea-level function are consistent with results from regions outside of the Mediterranean and reflect global values. Using the calibrated model parameters the relative sea-level change due to eustasy and the concomitant isostasy is predicted across the central Mediterranean region. Holocene tectonic rates of vertical motion are also given for the Italian coastal zone. At most sites where the MIS 5.5 shoreline occurs above or below its 'tectonically stable' position, the inferred rates of vertical crustal displacements are consistent with the assumption that average rates for the past B125,000 years are comparable to the average Holocene rates, but at some locations in eastern Sicily and southern Calabria the Holocene rates exceed the longer term average rates. r

1996, Earth and Planetary …

A major discrepancy between the Late Quatemary sea level changes derived from raised coral reef terraces at the Huon Peninsula in Papua New Guinea and from oxygen isotopes in deep sea cores is resolved. The two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka (ka = 1000 yr before present), but between 70 and 30 ka the isotopic sea levels are 20-40 m lower than the Huon Peninsula sea levels derived in earlier studies. New, high precision U-series age measurements and revised stratigraphic data for Huon Peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 6"O data. Using the sea level and deep sea isotopic data, oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from Greenland ice cores. The record of ice volume changes through the last glacial cycle now appears to be reasonably complete. Kqvwords: Quatemary; Huon Peninsula; U-234/Th-230; O-18/0-16; sea-level changes * Corresponding author. march in step with S "0 variations in deep ocean cores [l]. Furthermore, correlation of the HP sea levels with deep sea core records is supported by oxygen isotope data from giant clams (Triducna gigas> that are preserved in the coral terraces [2]. Sea levels deduced from HP for oxygen isotope stages 5a (83 ka) and 5c (104 ka) are supported by results from other places, including Barbados [3], Timor [4] and Haiti [5]. HP terraces dated around 60 and 40 ka have age equivalents at Kikai-Jima [6] and Vanuatu 0012-821X/96/$12.00 0 1996 Elsevier Science B.V. All rights reserved PII SOOIZ-821X(96)00062-3

2009, Nature

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2006, Journal of Climate

The climate sensitivity of the Community Climate System Model version 3 (CCSM3) is studied for two past climate forcings, the Last Glacial Maximum (LGM) and the mid-Holocene. The LGM, approximately 21 000 yr ago, is a glacial period with large changes in the greenhouse gases, sea level, and ice sheets. The mid-Holocene, approximately 6000 yr ago, occurred during the current interglacial with primary changes in the seasonal solar irradiance.

1998

Maps of upper-level and surface winds and of surface temperature and precipitation illustrate the results of a sequence of global paleoclimatic simulations spanning the past 21,000 years for North America. We review a) the large-scale features of circulation, temperature, and precipitation that appear in the simulations from the NCAR Community Climate Model Version 1 (CCM 1), b) the implications of the simulated climate for the past continental-scale distributions of three plant taxa (Picea spp., Pseudotsuga menziesii, and Artemisia tridentata), which are broadly representative of the vegetation across the continent, and c) the potential explanations in terms of atmospheric circulation or surface energy-and water-balance processes for mismatches between the simulations and observations. Most of the broad-scale features of previous paleoclimatic simulations with the NCAR CCM 0 for North America are present in the current simulations. Many of the elements of a conceptual model (based on previous climate simulations) that describes the controls of paleoclimatic variations across North America during the past 21,000 years are found in simulations reviewed here. These include 1) displacement of the jet stream by the Laurentide Ice Sheet to the south of its present position in both winter and summer, 2) generation of a "glacial anticyclone" over the ice sheet at the LGM, and the consequent induction of large-scale sinking motions induced over eastern North America, 3) changes in the strength of surface atmospheric circulation features through time, including weakening of the Aleutian low in winter, and strengthening of the eastern Pacific and Bermuda high-pressure systems in summer as the ice sheet decreased in size, 4) development of a "heat low" at the surface and a strengthened ridge in the upper-atmosphere over the continent at the time of the maximum summer insolation anomaly, 5) increases in summer temperature earlier in regions remote from the ice sheet (these increases appear earlier in the present (CCM 1) simulations than in the previous (CCM 0) ones, however), and 6) continuation of negative winter temperature anomalies into the middle Holocene. In general, simulated surface conditions that are discordant with paleoenvironmental observations can be attributed to the simulation of particular atmospheric circulation patterns (e.g. those that suppress precipitation or advect warm air into a region), with these mismatches amplified in Beringia and the southeastern United States by surface energy-and water-balance processes.

1998, Global Change Biology

This paper overviews the short-term (biophysical) and long-term (out to around 100 year timescales; biogeochemical and biogeographical) influences of the land surface on weather and climate. From our review of the literature, the evidence is convincing that terrestrial ecosystem dynamics on these timescales significantly influence atmospheric processes. In studies of past and possible future climate change, terrestrial ecosystem dynamics are as important as changes in atmospheric dynamics and composition, ocean circulation, ice sheet extent, and orbit perturbations.

2010, Nature Geoscience

Climate sensitivity-the mean global temperature response to a doubling of atmospheric CO 2 concentrations through radiative forcing and associated feedbacks-is estimated at 1.5-4.5 • C (ref. 1). However, this value incorporates only relatively rapid feedbacks such as changes in atmospheric water vapour concentrations, and the distributions of sea ice, clouds and aerosols 2 . Earth-system climate sensitivity, by contrast, additionally includes the effects of long-term feedbacks such as changes in continental ice-sheet extent, terrestrial ecosystems and the production of greenhouse gases other than CO 2 . Here we reconstruct atmospheric carbon dioxide concentrations for the early and middle Pliocene, when temperatures were about 3-4 • C warmer than preindustrial values 3-5 , to estimate Earth-system climate sensitivity from a fully equilibrated state of the planet. We demonstrate that only a relatively small rise in atmospheric CO 2 levels was associated with substantial global warming about 4.5 million years ago, and that CO 2 levels at peak temperatures were between about 365 and 415 ppm. We conclude that the Earth-system climate sensitivity has been significantly higher over the past five million years than estimated from fast feedbacks alone.

1985, Journal of Geophysical Research

The climate influence of the land ice that existed 18,000 years before present (18K B.P.) is investigated by use of a general circulation model of the atmosphere coupled with a static mixed layer ocean. Simulated climates are obtained from two versions of the model: one with the land ice distribution of the present and the other with that of 18K B.P. In the northern hemisphere the tropospheric flow field is strongly influenced by the Laurentide ice sheet and features a split flow straddling the ice sheet, with a strong jet stream forming the southern branch. The northern branch of the flow brings very cold air over the North Atlantic Ocean, where thick sea ice is maintained. The distribution of sea surface temperature (SST) difference between the two experiments in the northern hemisphere resembles the difference between the SST at 18K B.P. and at present, as estimated by the CLIMAP Project (1981). The 18K B.P. ice sheets have very little influence upon atmospheric temperature and SST in the southern hemisphere. This is because the interhemispheric heat transport hardly changes as the loss of heat energy due to the reflection of solar radiation by continental ice sheets in the northern hemisphere is almost completely counterbalanced by the in situ reduction of upward terrestrial radiation. Hydrologic changes in the model climate are also found, with statistically significant decreases in soil moisture occurring in a zone located to the south of the ice sheets in North America and Eurasia. These findings are consistent with some geological evidence of regionally drier climates from the last glacial maximum.

2009, Nature Geoscience

The recent marked retreat, thinning and acceleration of most of Greenland's outlet glaciers south of 70 • N has increased concerns over Greenland's contribution to future sea level rise 1-5 . These dynamic changes seem to be parallel to the warming trend in Greenland, but the mechanisms that link climate and ice dynamics are poorly understood, and current numerical models of ice sheets do not simulate these changes realistically 6-8 . Uncertainties in the predictions of mass loss from the Greenland ice sheet have therefore been highlighted as one of the main limitations in forecasting future sea levels 9 . Here we present a numerical ice-flow model that reproduces the observed marked changes in Helheim Glacier, one of Greenland's largest outlet glaciers. Our simulation shows that the ice acceleration, thinning and retreat begin at the calving terminus and then propagate upstream through dynamic coupling along the glacier. We find that these changes are unlikely to be caused by basal lubrication through surface melt propagating to the glacier bed. We conclude that tidewater outlet glaciers adjust extremely rapidly to changing boundary conditions at the calving terminus. Our results imply that the recent rates of mass loss in Greenland's outlet glaciers are transient and should not be extrapolated into the future.

1997, Journal of Geophysical Research

We present a combined heat- and ice-flow model, constrained by measurements of temperature in the Greenland Ice Sheet Project 2 (GISP2) borehole and by the GISP2 51so record and depth-age scale, which determines a history of temperature, accumulation rate, and ice sheet elevation for the past 50,000 years in central Greenland. Important results are: that the temperature increase from average glacial to Holocene conditions was large, approximately 15 øC, with a 20 øC warming from late glacial to Holocene; that the average accumulation rate during the last glacial maximum (between 15 and 30 kyr B. P.) was 5.5 to 7 cm yr -1, approximately 25% of the modern accumulation rate; that long-term (500-1000 years) averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the Holocene; and that the Greenland Ice Sheet probably thickened during the aleglacial transition. The inverse correlation of accumulation rate and temperature in the mid ...

2006, Geophysical Research Letters