scholarly journals EVALUATION OF SURFACE MELT RATE USING A MASS BALANCE MODEL OF THE ANTARCTIC ICE SHEET

2017 ◽  
Vol 4 ◽  
pp. 72-79
Author(s):  
I.А. Коrnеvа ◽  
◽  
О.О. Rybak ◽  
◽  
◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Balance Model ◽  
Mass Balance Model ◽  
Antarctic Ice Sheet ◽  
Surface Melt ◽  
The Antarctic

scholarly journals A Joint Inversion Estimate of Antarctic Ice Sheet Mass Balance Using Multi-Geodetic Data Sets

2019 ◽  
Vol 11 (6) ◽  
pp. 653 ◽  
Author(s):  
Chunchun Gao ◽  
Yang Lu ◽  
Zizhan Zhang ◽  
Hongling Shi
Keyword(s):  
Mass Balance ◽  
Joint Inversion ◽  
Ice Sheet ◽  
Mass Change ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
Uplift Rates ◽  
The Antarctic

Many recent mass balance estimates using the Gravity Recovery and Climate Experiment (GRACE) and satellite altimetry (including two kinds of sensors of radar and laser) show that the ice mass of the Antarctic ice sheet (AIS) is in overall decline. However, there are still large differences among previously published estimates of the total mass change, even in the same observed periods. The considerable error sources mainly arise from the forward models (e.g., glacial isostatic adjustment [GIA] and firn compaction) that may be uncertain but indispensable to simulate some processes not directly measured or obtained by these observations. To minimize the use of these forward models, we estimate the mass change of ice sheet and present-day GIA using multi-geodetic observations, including GRACE and Ice, Cloud and land Elevation Satellite (ICESat), as well as Global Positioning System (GPS), by an improved method of joint inversion estimate (JIE), which enables us to solve simultaneously for the Antarctic GIA and ice mass trends. The GIA uplift rates generated from our JIE method show a good agreement with the elastic-corrected GPS uplift rates, and the total GIA-induced mass change estimate for the AIS is 54 ± 27 Gt/yr, which is in line with many recent GPS calibrated GIA estimates. Our GIA result displays the presence of significant uplift rates in the Amundsen Sea Embayment of West Antarctica, where strong uplift has been observed by GPS. Over the period February 2003 to October 2009, the entire AIS changed in mass by −84 ± 31 Gt/yr (West Antarctica: −69 ± 24, East Antarctica: 12 ± 16 and the Antarctic Peninsula: −27 ± 8), greater than the GRACE-only estimates obtained from three Mascon solutions (CSR: −50 ± 30, JPL: −71 ± 30, and GSFC: −51 ± 33 Gt/yr) for the same period. This may imply that single GRACE data tend to underestimate ice mass loss due to the signal leakage and attenuation errors of ice discharge are often worse than that of surface mass balance over the AIS.

scholarly journals Climate, the Antarctic ice sheet and ground heat flux

1995 ◽  
Vol 21 ◽  
pp. 144-148
Author(s):  
Garth W. Paltridge ◽  
Christopher M. Zweck
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Climate Models ◽  
Global Climate ◽  
Ice Sheet ◽  
Global Climate Models ◽  
Balance Model ◽  
Antarctic Ice Sheet ◽  
Ground Heat Flux ◽  
The Antarctic

A simple steady-state energy and mass-balance model of the Antarctic ice sheet is developed. Basically it is a set of two equations with two unknowns of steady-state height h and potential basal temperature Tb. Tb determines whether, and to what extent, there is liquid water at the base of the ice which in turn affects the values of h and Tb. Simultaneous changes of sea-level temperature and precipitation (changes related to each other as might be expected from global climate models) indicate a maximum in the field of possible steady-state ice volumes which may not be far from the presently observed conditions. The possibility of cyclical variation in ground heat flux associated with convection of water and heat in the continental crust is discussed. The mechanism might be capable of generating cycles of ice-sheet volume with relatively short periods similar to those of Milankovitch forcing.

scholarly journals An Evaluation of Surface Climatology in State-of-the-Art Reanalyses over the Antarctic Ice Sheet

2019 ◽  
Vol 32 (20) ◽  
pp. 6899-6915 ◽  
Author(s):  
A. Gossart ◽  
S. Helsen ◽  
J. T. M. Lenaerts ◽  
S. Vanden Broucke ◽  
N. P. M. van Lipzig ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Surface Temperature ◽  
Mass Balance ◽  
Ice Sheet ◽  
Surface Mass Balance ◽  
Antarctic Ice Sheet ◽  
Near Surface ◽  
Surface Mass ◽  
Atmospheric Rivers ◽  
The Antarctic

Abstract In this study, we evaluate output of near-surface atmospheric variables over the Antarctic Ice Sheet from four reanalyses: the new European Centre for Medium-Range Weather Forecasts ERA-5 and its predecessor ERA-Interim, the Climate Forecast System Reanalysis (CFSR), and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The near-surface temperature, wind speed, and relative humidity are compared with datasets of in situ observations, together with an assessment of the simulated surface mass balance (approximated by precipitation minus evaporation). No reanalysis clearly stands out as the best performing for all areas, seasons, and variables, and each of the reanalyses displays different biases. CFSR strongly overestimates the relative humidity during all seasons whereas ERA-5 and MERRA-2 (and, to a lesser extent, ERA-Interim) strongly underestimate relative humidity during winter. ERA-5 captures the seasonal cycle of near-surface temperature best and shows the smallest bias relative to the observations. The other reanalyses show a general temperature underestimation during the winter months in the Antarctic interior and overestimation in the coastal areas. All reanalyses underestimate the mean near-surface winds in the interior (except MERRA-2) and along the coast during the entire year. The winds at the Antarctic Peninsula are overestimated by all reanalyses except MERRA-2. All models are able to capture snowfall patterns related to atmospheric rivers, with varying accuracy. Accumulation is best represented by ERA-5, although it underestimates observed surface mass balance and there is some variability in the accumulation over the different elevation classes, for all reanalyses.

Climate parameters influencing satellite-based volume and elevation changes of the Antarctic ice sheet

2020 ◽  
Author(s):  
Athul Kaitheri ◽  
Anthony Mémin ◽  
Frédérique Rémy
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Snow Accumulation ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Changing Climate ◽  
Basin Scale ◽  
Elevation Changes ◽  
The Antarctic ◽  
Grace Mission

<p>Precisely quantifying the Antarctic Ice Sheet (AIS) mass balance remains a challenge as several processes compete at differing degrees in the basin-scale with regional variations. Understanding of changes in AIS has been largely based on observations from various altimetry missions and Gravity Recovery And Climate Experiment (GRACE) missions due to its scale and coverage. Analysis of linear trends in surface height variations of AIS since the early 1990s showed multiple variabilities in the rate of changes over the period of time. These observations are a reflection of various underlying ice sheet processes. Therefore understanding the processes that interact on the ice sheet is important to precisely determine the response of the ice sheet to a rapidly changing climate.</p><p>Changing climate constitutes variations in major short term processes including snow accumulation and surface melting. Variations in accumulation rate and temperature at the ice sheet surface cause changes in the firn compaction (FC) rate. Variations in the FC rate change the AIS thickness, that should be detected from altimetry, but do not change its mass, as observed by the GRACE mission. We focus our study on the seasonal and interannual changes in the elevation and mass of the AIS. We use surface elevation changes from Envisat data and gravity changes derived from the latest GRACE solutions between 10/2002 and 10/2010. As mass changes observed using the GRACE mission is strongly impacted by long term isostasy, as it involves mantle mass redistribution, we remove from all dataset an 8-year trend. We use weather variable historical data solutions including surface mass balance, temperature and wind velocities from the regional climate model RACMO2.3p2 as input to an FC model to estimate AIS elevation changes. We obtain a very good correlation between height change estimates from GRACE, Envisat and RACMO2.3p2 at several places such as along the coast of Dronning Maud Land, Wilkes land and Amundsen sea sector. Considerable differences in Oates and Mac Robertson regions, with a strong seasonal signal in Envisat estimates, reflect spatial variability in physical parameters of the surface of the AIS due to climate parameter changes such as winds.</p>

Automated mapping of Antarctic supraglacial lakes and streams using machine learning

2020 ◽  
Author(s):  
Mariel Dirscherl ◽  
Andreas Dietz ◽  
Celia Baumhoer ◽  
Christof Kneisel ◽  
Claudia Kuenzer
Keyword(s):  
Machine Learning ◽  
Mass Balance ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Supraglacial Lakes ◽  
The Antarctic ◽  
Sentinel 2

<p>Antarctica stores ~91 % of the global ice mass making it the biggest potential contributor to global sea-level-rise. With increased surface air temperatures during austral summer as well as in consequence of global climate change, the ice sheet is subject to surface melting resulting in the formation of supraglacial lakes in local surface depressions. Supraglacial meltwater features may impact Antarctic ice dynamics and mass balance through three main processes. First of all, it may cause enhanced ice thinning thus a potentially negative Antarctic Surface Mass Balance (SMB). Second, the temporary injection of meltwater to the glacier bed may cause transient ice speed accelerations and increased ice discharge. The last mechanism involves a process called hydrofracturing i.e. meltwater-induced ice shelf collapse caused by the downward propagation of surface meltwater into crevasses or fractures, as observed along large coastal sections of the northern Antarctic Peninsula. Despite the known impact of supraglacial meltwater features on ice dynamics and mass balance, the Antarctic surface hydrological network remains largely understudied with an automated method for supraglacial lake and stream detection still missing. Spaceborne remote sensing and data of the Sentinel missions in particular provide an excellent basis for the monitoring of the Antarctic surface hydrological network at unprecedented spatial and temporal coverage.</p><p>In this study, we employ state-of-the-art machine learning for automated supraglacial lake and stream mapping on basis of optical Sentinel-2 satellite data. With more detail, we use a total of 72 Sentinel-2 acquisitions distributed across the Antarctic Ice Sheet together with topographic information to train and test the selected machine learning algorithm. In general, our machine learning workflow is designed to discriminate between surface water, ice/snow, rock and shadow being further supported by several automated post-processing steps. In order to ensure the algorithm’s transferability in space and time, the acquisitions used for training the machine learning model are chosen to cover the full circle of the 2019 melt season and the data selected for testing the algorithm span the 2017 and 2018 melt seasons. Supraglacial lake predictions are presented for several regions of interest on the East and West Antarctic Ice Sheet as well as along the Antarctic Peninsula and are validated against randomly sampled points in the underlying Sentinel-2 RGB images. To highlight the performance of our model, we specifically focus on the example of the Amery Ice Shelf in East Antarctica, where we applied our algorithm on Sentinel-2 data in order to present the temporal evolution of maximum lake extent during three consecutive melt seasons (2017, 2018 and 2019).</p>

scholarly journals Changes in ice dynamics and mass balance of the Antarctic ice sheet

2006 ◽  
Vol 364 (1844) ◽  
pp. 1637-1655 ◽  
Author(s):  
Eric Rignot
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
Ice Sheet ◽  
East Antarctica ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
The Antarctic

The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1 m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 °C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.

scholarly journals Response of Antarctic Ice Sheet Mass Balance to Climate Change

2018 ◽  
Author(s):  
Jingang Zhan ◽  
Hongling Shi ◽  
Yong Wang ◽  
Yixin Yao ◽  
Yongbin Wu
Keyword(s):  
Surface Temperature ◽  
Mass Balance ◽  
Ice Sheet ◽  
Low Frequency ◽  
Principal Component ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Mass Change ◽  
Antarctic Ice Sheet ◽  
The Antarctic

Abstract. The ice record should have recorded and will likely reflect information on environmental changes such as atmospheric circulation. In this paper, 153 months of Gravity Recovery and Climate Experiment (GRACE) satellite time-varying gravity solutions were used to study the principal components of the Antarctic ice sheet mass change and their time-frequency variation. This assessment is based on complex principal component analysis and the wavelet amplitude-period spectrum method to reveal the main climatic factors that affect the change on the ice sheet. The complex principal component analysis results reveal the principal components that affect the mass change of the ice sheet; the wavelet analysis present the time-frequency variation of each component and the possible relationship between each principal component and different climatic factors. The results show that the specific climate factors represented by low-frequency signals with a period greater than 5 years dominate the changes of the Antarctic ice sheet mass balance. These climate factors are related to the abnormal sea surface temperature changes in the equatorial Pacific (Niño 1+2 region), the correlation between the low-frequency periodic signal of sea surface temperature anomalies in the equatorial Pacific and the first principal component of the ice sheet mass change in Antarctica is 0.65. The first principal component explains 85.45 % of the mass change in the ice sheet. The change in the meridional wind at 700 hPa in the South Pacific may be the key factor that determines the effect of sea surface temperature anomalies in the equatorial Pacific on the Antarctic ice sheet. The atmospheric temperature change in Antarctica is the second most important factor that affects the mass balance of the ice sheet in the area, and its contribution to the mass balance of the ice sheet is only 6.35 %. This result means that with the increase of low-frequency signals during the El Niño period, Antarctic ice sheet mass changes may intensify.

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