scholarly journals Modelling snow accumulation on Greenland in Eemian, glacial inception and modern climates in a GCM

2012 ◽  
Vol 8 (2) ◽  
pp. 1523-1565 ◽  
Author(s):  
H. J. Punge ◽  
H. Gallée ◽  
M. Kageyama ◽  
G. Krinner
Keyword(s):  
Mass Balance ◽  
Ocean Circulation ◽  
Accumulation Rate ◽  
High Surface ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Local Climate ◽  
North East ◽  
Surface Climate

Abstract. Changing climate conditions on Greenland influence the snow accumulation rate and surface mass balance (SMB) on the ice sheet and, ultimately, its shape. This can in turn affect local climate via orography and albedo variations and, potentially, remote areas via changes in ocean circulation triggered by melt water or calving from the ice sheet. Examining these issues in the IPSL global model requires improving the representation of snow at the ice sheet surface. In this paper, we present the new snow scheme implemented in LMDZ, the atmospheric component of the IPSL coupled model. We analyze surface climate and SMB on the Greenland ice sheet under insolation and oceanic boundary conditions for modern, but also for two different past climates, the last glacial inception (115 kyr BP) and the Eemian (126 kyr BP). While being limited by the low resolution of the GCM, present-day SMB is on the same order of magnitude as recent regional model findings. It is affected by a moist bias of the GCM in Western Greenland and a dry bias in the north-east. Under Eemian conditions, the SMB diminishes largely, and melting affects areas with today high surface altitude including recent ice core drilling sites as NEEM. In contrast, glacial inception conditions lead to a higher mass balance overall due to the reduced melting in the colder summer climate. Compared to the widely applied positive degree day (PDD) parameterization of SMB, our direct modelling results suggest a weaker sensitivity of SMB to changing climatic forcing. In addition, significant differences in surface climate and SMB are found between simulations using monthly climatological mean and actual interannually varying monthly mean forcings for the ocean surface temperature and sea ice cover, in particular for the Eemian.

scholarly journals Modelling snow accumulation on Greenland in Eemian, glacial inception, and modern climates in a GCM

2012 ◽  
Vol 8 (6) ◽  
pp. 1801-1819 ◽  
Author(s):  
H. J. Punge ◽  
H. Gallée ◽  
M. Kageyama ◽  
G. Krinner
Keyword(s):  
Mass Balance ◽  
Ocean Circulation ◽  
General Circulation ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Circulation Model ◽  
Snow Accumulation ◽  
Sheet Surface ◽  
North East

Abstract. Changing climate conditions on Greenland influence the snow accumulation rate and surface mass balance (SMB) on the ice sheet and, ultimately, its shape. This can in turn affect local climate via orography and albedo variations and, potentially, remote areas via changes in ocean circulation triggered by melt water or calving from the ice sheet. Examining these interactions in the IPSL global model requires improving the representation of snow at the ice sheet surface. In this paper, we present a new snow scheme implemented in LMDZ, the atmospheric component of the IPSL coupled model. We analyse surface climate and SMB on the Greenland ice sheet under insolation and oceanic boundary conditions for modern, but also for two different past climates, the last glacial inception (115 kyr BP) and the Eemian (126 kyr BP). While being limited by the low resolution of the general circulation model (GCM), present-day SMB is on the same order of magnitude as recent regional model findings. It is affected by a moist bias of the GCM in Western Greenland and a dry bias in the north-east. Under Eemian conditions, the SMB decreases largely, and melting affects areas in which the ice sheet surface is today at high altitude, including recent ice core drilling sites as NEEM. In contrast, glacial inception conditions lead to a higher mass balance overall due to the reduced melting in the colder summer climate. Compared to the widely applied positive degree-day (PDD) parameterization of SMB, our direct modelling results suggest a weaker sensitivity of SMB to changing climatic forcing. For the Eemian climate, our model simulations using interannually varying monthly mean forcings for the ocean surface temperature and sea ice cover lead to significantly higher SMB in southern Greenland compared to simulations forced with climatological monthly means.

scholarly journals Recent North Greenland temperature warming and accumulation

2021 ◽  
Author(s):  
Helle Astrid Kjær ◽  
Patrick Zens ◽  
Ross Edwards ◽  
Martin Olesen ◽  
Ruth Mottram ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Topographic Effects ◽  
North East ◽  
The North ◽  
North Greenland

Abstract. In a warming climate concise knowledge of the mass balance of the Greenland ice sheet is of utter importance. Speculations that current warming will increase the snow accumulation and mitigate mass balance losses are unconstrained as accumulation data across large regions of the northern ice sheet are scarce. We reconstructed the accumulation from six north Greenland shallow firn cores (~10 m) and eight snow cores (~2 m) to constrain recent accumulation patterns in northern Greenland and calculated recent warming in the same area using borehole temperature measurements. We find an increase in temperatures in the north Greenland interior of 0.9 to 2.5 °C (method and site dependent) per decade over the past two decades in line with an Arctic amplified anthropogenic warming. We compare annual reconstructed accumulation from the firn cores (1966–2015) to radar estimates and to annual re-analysis data (1980–2016) of precipitation subtracted evaporation from the regional climate model HIRHAM5, operated by the Danish Meteorological Institute. The spatial variability resembles that observed in earlier estimates with a clear increase west of the topographic divide and a low accumulation area across the north-eastern ice sheet. Our accumulation results are comparable to earlier firn core estimates, despite being larger in the east. We only find a positive significant trend in the accumulation for the period 2000–2010 to the northwest. In the vicinity of the EGRIP deep ice core drilling site, we find variable accumulation patterns for two 15 km apart firn cores likely owing to local topographic effects as a result of the North East Greenland Ice Stream dynamics.

scholarly journals Recent precipitation decrease across the western Greenland ice sheet percolation zone

2019 ◽  
Vol 13 (11) ◽  
pp. 2797-2815 ◽  
Author(s):  
Gabriel Lewis ◽  
Erich Osterberg ◽  
Robert Hawley ◽  
Hans Peter Marshall ◽  
Tate Meehan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Accumulation Rates ◽  
The Past ◽  
Precipitation Decrease ◽  
Percolation Zone

Abstract. The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest in the context of future sea level rise. Increased melting in the GrIS percolation zone due to atmospheric warming over the past several decades has led to increased mass loss at lower elevations. Previous studies have hypothesized that this warming is accompanied by a precipitation increase, as would be expected from the Clausius–Clapeyron relationship, compensating for some of the melt-induced mass loss throughout the western GrIS. This study tests that hypothesis by calculating snow accumulation rates and trends across the western GrIS percolation zone, providing new accumulation rate estimates in regions with sparse in situ data or data that do not span the recent accelerating surface melt. We present accumulation records from sixteen 22–32 m long firn cores and 4436 km of ground-penetrating radar, covering the past 20–60 years of accumulation, collected across the western GrIS percolation zone as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project. Trends from both radar and firn cores, as well as commonly used regional climate models, show decreasing accumulation rates of 2.4±1.5 % a−1 over the 1996–2016 period, which we attribute to shifting storm tracks related to stronger atmospheric summer blocking over Greenland. Changes in atmospheric circulation over the past 20 years, specifically anomalously strong summertime blocking, have reduced GrIS surface mass balance through both an increase in surface melting and a decrease in accumulation rates.

scholarly journals Mass balance of the northeast sector of the Greenland ice sheet: a remote-sensing perspective

2000 ◽  
Vol 46 (153) ◽  
pp. 265-273 ◽  
Author(s):  
Eric Rignot ◽  
Guillaume Buscarlet ◽  
Beáta Csathó ◽  
Sivaprasad Gogineni ◽  
William Krabill ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Ice Shelf ◽  
Synthetic Aperture Radar Interferometry ◽  
Model Predictions ◽  
Grounding Line ◽  
Ice Production ◽  
Inland Ice

AbstractSynthetic-aperture radar interferometry data and airborne ice-sounding radar (ISR) data are employed to obtain modern estimates of the inland ice production from Nioghalvfjerdsbræ (NB) and Zachariae Isstrøm (ZI), the two largest glaciers draining the northeast sector of the Greenland ice sheet. Ice fluxes are measured at the grounding line (14.2 ±1 km3 ice a−1 for NB and 10.8 ±1 km3 ice a−1 for ZI) with an ice thickness deduced from ice-shelf hydrostatic equilibrium, and along an ISR profile collected upstream of the grounding line (14.3 ± 0.7 km3 ice a−1 for NB and 11.6 ± 0.6 km3 ice a−1 for ZI). Balance fluxes calculated from a map of snow accumulation and model predictions of surface melt are 11.9 ± 2 km3 ice a−1 for NB and 10.0 ± 2 km3 ice a−1 for ZI at the grounding line, and 12.2 and 10.3 km3 ice a−1, respectively, at the ISR line. The two glaciers therefore exhibit a negative mass balance equivalent to 14% of their balance flux, with a ±12% uncertainty. Independently, we detect a retreat of the grounding line of NB between 1992 and 1996 which is larger at the glacier center (920 ± 250 m) than on the sides (240 ± 50 m). The corresponding ice-thinning rates (2 ± 1 m a−1 at the glacier center and 0.6 ± 0.3 m a−1 on the sides) are too large to be accommodated by temporal changes in ablation or accumulation, and must be due to dynamic thinning.

scholarly journals Mass Balance of the Greenland Ice Sheet at Dye 3

1985 ◽  
Vol 31 (108) ◽  
pp. 198-200 ◽  
Author(s):  
Niels Reeh ◽  
Niels S. Gundestrup
Keyword(s):  
Mass Balance ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Bottom Layer ◽  
Surface Strain ◽  
Ice Thickness ◽  
Strain Rates ◽  
Confidence Limits ◽  
Rate Of Increase

AbstractThe mass balance of the Greenland ice sheet at Dye 3 is estimated on the basis of observations of ice thickness, accumulation rate, surface velocities, and surface strain-rates. The calculations indicate a rate of increase of surface elevation of 3 cm/year, with 95% confidence limits of −3 cm/year and +9 cm/year. Previous estimates of the mass balance of the Greenland ice sheet by the same method reported large imbalances; these are most probably due to lack of precise data and the use of quantities measured at the surface as representative of depth-averaged quantities. The most reliable observations indicate that the interior regions of the Greenland ice sheet are at present thickening at a rate of a few centimetres per year; a contributing cause for this may be the slow thinning of a bottom layer of relatively soft Wisconsin ice.

scholarly journals Surface mass balance of the Greenland ice sheet from climate-analysis data and accumulation/runoff models

2002 ◽  
Vol 35 ◽  
pp. 67-72 ◽  
Author(s):  
Edward Hanna ◽  
Philippe Huybrechts ◽  
Thomas L. Mote
Keyword(s):  
Mass Balance ◽  
Satellite Data ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Surface Elevation ◽  
Great Promise ◽  
Surface Mass Balance ◽  
Ice Dynamics ◽  
Surface Mass

AbstractWe used surface climate fields from high-resolution (~0.5660.56˚) European Centre for Medium-RangeWeather Forecasts (ECMWF) operational analyses (1992–98), together with meteorological and glaciological models of snow accumulation and surface meltwater runoff/retention, to produce novel maps of Greenland ice sheet (GIS) net accumulation, net runoff and surface mass balance (SMB). We compared our runoff maps with similar-scaled runoff (melt minus refreezing) maps based on passive-microwave satellite data. Our gross spatial/temporal patterns of runoff compared well with those from the satellite data, although amounts of modelled runoff are likely too low. Mean accumulation was 0.287 (0.307)ma–1, and mean runoff was 0.128 (0.151)ma–1, averaged across the W. Abdalati (T. L. Mote) GIS mask. Corresponding mean SMB was 0.159 (0.156)ma–1, with considerable interannual variability (standard deviation ~0.11ma–1) primarily due to variations in runoff. Considering best estimates of current iceberg calving, overall the GIS is probably currently losing mass. Our study shows great promise for meaningfully modelling SMB based on forthcoming ``second-generation’’ ECMWF re-analysis (ERA-40) data, and comparing the results with ongoing laser/radarmeasurements of surface elevation. This should help elucidate to what extent surface elevation changes are caused by short-term SMB variations or other factors (e.g. ice dynamics).

scholarly journals Annual Greenland accumulation rates (2009–2012) from airborne snow radar

2016 ◽  
Vol 10 (4) ◽  
pp. 1739-1752 ◽  
Author(s):  
Lora S. Koenig ◽  
Alvaro Ivanoff ◽  
Patrick M. Alexander ◽  
Joseph A. MacGregor ◽  
Xavier Fettweis ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Ultra Wideband ◽  
The Arctic ◽  
Surface Mass Balance ◽  
Accumulation Rates ◽  
Surface Mass

Abstract. Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2–6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009–2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

scholarly journals Mass Balance of the Greenland Ice Sheet at Dye 3

1985 ◽  
Vol 31 (108) ◽  
pp. 198-200 ◽  
Author(s):  
Niels Reeh ◽  
Niels S. Gundestrup
Keyword(s):  
Mass Balance ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Bottom Layer ◽  
Surface Strain ◽  
Ice Thickness ◽  
Strain Rates ◽  
Confidence Limits ◽  
Rate Of Increase

AbstractThe mass balance of the Greenland ice sheet at Dye 3 is estimated on the basis of observations of ice thickness, accumulation rate, surface velocities, and surface strain-rates. The calculations indicate a rate of increase of surface elevation of 3 cm/year, with 95% confidence limits of −3 cm/year and +9 cm/year. Previous estimates of the mass balance of the Greenland ice sheet by the same method reported large imbalances; these are most probably due to lack of precise data and the use of quantities measured at the surface as representative of depth-averaged quantities. The most reliable observations indicate that the interior regions of the Greenland ice sheet are at present thickening at a rate of a few centimetres per year; a contributing cause for this may be the slow thinning of a bottom layer of relatively soft Wisconsin ice.

A contourite drift succession in north-east Baffin Bay: a high-resolution Pleistocene archive of Greenland ice sheet and ocean variability

2020 ◽  
Author(s):  
Paul C. Knutz ◽  
Katrine Juul Andresen ◽  
John R. Hopper ◽  
Lara F. Perez ◽  
Calvin Campbell ◽  
...  
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Pleistocene ◽  
Target Area ◽  
Baffin Bay ◽  
North East

<p><span>The Greenland ice sheet’s response to anthropogenic warming will have major consequences for global sea levels but its behavior and stability during past warm intervals is poorly known. To elucidate the long-term behavior of the Greenland ice sheet, high-resolution marine records in ice proximal settings are required. Here we report the first results of a study of a deep-water contourite system on the north-east slope Baffin Bay based on geophysical and shallow core data obtained during two marine expeditions in 2017 and 2019. The contourite drift is incised by channels extending from the slope that is build up by prograding ice stream deposits (Melville Bugt trough-mouth fan). As a result, the contourite system presents a complex architecture. While the mechanisms for deposition and erosion are not yet clear, it is likely that the drift accumulated as a result of interactions between a deep contour current and downslope transport of sediments, presumably of glacigenic origin and therefore constitutes an example of an intertwined contourite-turbidite system. A preliminary age-depth model of the trough-mouth fan evolution indicates that the contourite system began to form during the late Early Pleistocene, possibly around 1 million years ago. The contourite drift is a key target for IODP proposal 909, aimed at unravelling the late Cenozoic evolution of the northern Greenland ice sheet and associated changes in Arctic paleoclimate. Shallow sediment cores from this target area have been retrieved and will be analyzed to generate high-resolution multi-proxy records of ocean circulation and sea-surface conditions including sea ice and paleoproductivity for the late Quaternary-Holocene. </span></p>

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