scholarly journals The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution

2016 ◽  
Vol 10 (1) ◽  
pp. 271-285 ◽  
Author(s):  
J. M. van Wessem ◽  
S. R. M. Ligtenberg ◽  
C. H. Reijmer ◽  
W. J. van de Berg ◽  
M. R. van den Broeke ◽  
...  
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Climate Model ◽  
Horizontal Resolution ◽  
Surface Mass Balance ◽  
Data Sets ◽  
High Accumulation ◽  
Surface Mass ◽  
Meltwater Runoff ◽  
The Antarctic

Abstract. This study presents a high-resolution (∼  5.5 km) estimate of surface mass balance (SMB) over the period 1979–2014 for the Antarctic Peninsula (AP), generated by the regional atmospheric climate model RACMO2.3 and a firn densification model (FDM). RACMO2.3 is used to force the FDM, which calculates processes in the snowpack, such as meltwater percolation, refreezing and runoff. We evaluate model output with 132 in situ SMB observations and discharge rates from six glacier drainage basins, and find that the model realistically simulates the strong spatial variability in precipitation, but that significant biases remain as a result of the highly complex topography of the AP. It is also clear that the observations significantly underrepresent the high-accumulation regimes, complicating a full model evaluation. The SMB map reveals large accumulation gradients, with precipitation values above 3000 mm we yr−1 in the western AP (WAP) and below 500 mm we yr−1 in the eastern AP (EAP), not resolved by coarser data sets such as ERA-Interim. The average AP ice-sheet-integrated SMB, including ice shelves (an area of 4.1  ×  105 km2), is estimated at 351 Gt yr−1 with an interannual variability of 58 Gt yr−1, which is dominated by precipitation (PR) (365 ± 57 Gt yr−1). The WAP (2.4  ×  105 km2) SMB (276 ± 47 Gt yr−1), where PR is large (276 ± 47 Gt yr−1), dominates over the EAP (1.7  ×  105 km2) SMB (75 ± 11 Gt yr−1) and PR (84 ± 11 Gt yr−1). Total sublimation is 11 ± 2 Gt yr−1 and meltwater runoff into the ocean is 4 ± 4 Gt yr−1. There are no significant trends in any of the modelled AP SMB components, except for snowmelt that shows a significant decrease over the last 36 years (−0.36 Gt yr−2).

scholarly journals The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution

2015 ◽  
Vol 9 (5) ◽  
pp. 5097-5136
Author(s):  
J. M. van Wessem ◽  
S. R. M. Ligtenberg ◽  
C. H. Reijmer ◽  
W. J. van de Berg ◽  
M. R. van den Broeke ◽  
...  
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Climate Model ◽  
Horizontal Resolution ◽  
Surface Mass Balance ◽  
High Accumulation ◽  
Surface Mass ◽  
Ice Shelves ◽  
Meltwater Runoff ◽  
The Antarctic

Abstract. This study presents a high-resolution (~ 5.5 km) estimate of Surface Mass Balance (SMB) over the period 1979–2014 for the Antarctic Peninsula (AP), generated by the regional atmospheric climate model RACMO2.3 and a Firn Densification Model (FDM). RACMO2.3 is used to force the FDM, which calculates processes in the snowpack, such as meltwater percolation, refreezing and runoff. We evaluate model output with 132 in-situ SMB observations and discharge rates from 6 glacier drainage basins, and find that the model realistically simulates the strong spatial variability in precipitation, but that significant biases remain as a result of the highly complex topography of the AP. It is also clear that the observations significantly underrepresent the high-accumulation regimes. The SMB map reveals large accumulation gradients, with precipitation values above 3000 mm we yr−1 over the western AP (WAP) and below 500 mm we yr−1 on the eastern AP (EAP), not resolved by coarser data-sets such as ERA-Interim. The other SMB components are one order of magnitude smaller, with drifting snow sublimation the largest ablation term removing up to 100 mm we yr−1 of mass. Snowmelt is widespread over the AP, reaching 500 mm we yr−1 towards the northern ice shelves, but the meltwater mostly refreezes. As a result runoff fluxes are low, but still considerable (200 mm we yr−1) over the Larsen (B/C), Wilkins and George VI ice shelves. The average AP ice sheet integrated SMB, including ice shelves (an area of 4.1 × 105 km2), is estimated at 351 Gt yr−1 with an interannual variability of 58 Gt yr−1, which is dominated by precipitation (PR) (365 ± 57 Gt yr−1). The WAP (2.4 × 105 km2) SMB (276 ± 47 Gt yr−1), where PR is large (276 ± 47 Gt yr−1), dominates over the EAP (1.7 × 105 km2) SMB (75 ± 11 Gt yr−1) and PR (84 ± 11 Gt yr−1). Total sublimation is 11 ± 2 Gt yr−1 and meltwater runoff into the ocean is 4 ± 4 Gt yr−1. There are no significant trends in any of the AP SMB components, except for snowmelt that shows a significant decrease over the last 36 years (−0.36 Gt yr−2).

scholarly journals Seasonal mass variations show timing and magnitude of meltwater storage in the Greenland Ice Sheet

2018 ◽  
Vol 12 (9) ◽  
pp. 2981-2999 ◽  
Author(s):  
Jiangjun Ran ◽  
Miren Vizcaino ◽  
Pavel Ditmar ◽  
Michiel R. van den Broeke ◽  
Twila Moon ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Spatial Scales ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
High Accumulation ◽  
Outlet Glacier ◽  
Surface Mass ◽  
Meltwater Runoff

Abstract. The Greenland Ice Sheet (GrIS) is currently losing ice mass. In order to accurately predict future sea level rise, the mechanisms driving the observed mass loss must be better understood. Here, we combine data from the satellite gravimetry mission Gravity Recovery and Climate Experiment (GRACE), surface mass balance (SMB) output of the Regional Atmospheric Climate Model v. 2 (RACMO2), and ice discharge estimates to analyze the mass budget of Greenland at various temporal and spatial scales. We find that the mean rate of mass variations in Greenland observed by GRACE was between −277 and −269 Gt yr−1 in 2003–2012. This estimate is consistent with the sum (i.e., -304±126 Gt yr−1) of individual contributions – surface mass balance (SMB, 216±122 Gt yr−1) and ice discharge (520±31 Gt yr−1) – and with previous studies. We further identify a seasonal mass anomaly throughout the GRACE record that peaks in July at 80–120 Gt and which we interpret to be due to a combination of englacial and subglacial water storage generated by summer surface melting. The robustness of this estimate is demonstrated by using both different GRACE-based solutions and different meltwater runoff estimates (namely, RACMO2.3, SNOWPACK, and MAR3.9). Meltwater storage in the ice sheet occurs primarily due to storage in the high-accumulation regions of the southeast and northwest parts of Greenland. Analysis of seasonal variations in outlet glacier discharge shows that the contribution of ice discharge to the observed signal is minor (at the level of only a few gigatonnes) and does not explain the seasonal differences between the total mass and SMB signals. With the improved quantification of meltwater storage at the seasonal scale, we highlight its importance for understanding glacio-hydrological processes and their contributions to the ice sheet mass variability.

scholarly journals Characteristics of the Antarctic surface mass balance, 1958–2002, using a regional atmospheric climate model

2005 ◽  
Vol 41 ◽  
pp. 97-104 ◽  
Author(s):  
W.J. Van De Berg ◽  
M.R. Van Den Broeke ◽  
C.H. Reijmer ◽  
E. Van Meijgaard
Keyword(s):  
Mass Balance ◽  
Large Scale ◽  
Climate Model ◽  
Horizontal Resolution ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Solid Precipitation ◽  
Temporal And Spatial Characteristics ◽  
The Antarctic ◽  
Regional Atmospheric Climate Model

AbstractTemporal and spatial characteristics of the Antarctic specific surface mass balance (SSMB) are presented, including its components solid precipitation, sublimation/deposition and melt. For this purpose, we use the output of a regional atmospheric climate model (RACMO2/ANT, horizontal resolution of ~55 km) for the period 1958–2002. RACMO2/ANT uses European Centre for Medium-Range Weather Forecasts (ECMWF) 40 year re-analysis (ERA-40) fields as forcing at the lateral boundaries. RACMO2/ANT underestimates SSMB in the high interior of East and West Antarctica and overestimates SSMB on the steep coastal slopes. Otherwise, the modeled spatial pattern of SSMB is in good qualitative agreement with recent compilations of in situ observations. Large-scale patterns, like the precipitation shadow effect of the Antarctic Peninsula, are well reproduced, and mesoscale SSMB patterns, such as the strong precipitation gradients on Law Dome, are well represented in the model. The integrated SSMB over the grounded ice sheet is 153mmw.e. a–1 for the period 1958–2002, which agrees within 5% with the latest measurement compilations. Sublimation and melt remove 7% and <1% respectively of the solid precipitation. We found significant seasonality of solid precipitation, with a maximum in autumn and a minimum in summer. No meaningful trend was identified for the SSMB, because the time series of solid precipitation and SSMB are affected by an inhomogeneity in 1980 within the ERA-40 fields that drive RACMO2/ANT. Sublimation, melt and liquid precipitation increase in time, which is related to a modeled increase in 2m temperature.

scholarly journals Downscaled surface mass balance in Antarctica: impacts of subsurface processes and large-scale atmospheric circulation

2021 ◽  
Vol 15 (9) ◽  
pp. 4315-4333
Author(s):  
Nicolaj Hansen ◽  
Peter L. Langen ◽  
Fredrik Boberg ◽  
Rene Forsberg ◽  
Sebastian B. Simonsen ◽  
...  
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Total Mass ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Basin Scale ◽  
The Antarctic

Abstract. Antarctic surface mass balance (SMB) is largely determined by precipitation over the continent and subject to regional climate variability related to the Southern Annular Mode (SAM) and other climatic drivers at the large scale. Locally however, firn and snowpack processes are important in determining SMB and the total mass balance of Antarctica and global sea level. Here, we examine factors that influence Antarctic SMB and attempt to reconcile the outcome with estimates for total mass balance determined from the GRACE satellites. This is done by having the regional climate model HIRHAM5 forcing two versions of an offline subsurface model, to estimate Antarctic ice sheet (AIS) SMB from 1980 to 2017. The Lagrangian subsurface model estimates Antarctic SMB of 2473.5±114.4 Gt yr−1, while the Eulerian subsurface model variant results in slightly higher modelled SMB of 2564.8±113.7 Gt yr−1. The majority of this difference in modelled SMB is due to melt and refreezing over ice shelves and demonstrates the importance of firn modelling in areas with substantial melt. Both the Eulerian and the Lagrangian SMB estimates are within uncertainty ranges of each other and within the range of other SMB studies. However, the Lagrangian version has better statistics when modelling the densities. Further, analysis of the relationship between SMB in individual drainage basins and the SAM is carried out using a bootstrapping approach. This shows a robust relationship between SAM and SMB in half of the basins (13 out of 27). In general, when SAM is positive there is a lower SMB over the plateau and a higher SMB on the westerly side of the Antarctic Peninsula, and vice versa when the SAM is negative. Finally, we compare the modelled SMB to GRACE data by subtracting the solid ice discharge, and we find that there is a good agreement in East Antarctica but large disagreements over the Antarctic Peninsula. There is a large difference between published estimates of discharge that make it challenging to use mass reconciliation in evaluating SMB models on the basin scale.

scholarly journals Influence of Oceanic Boundary Conditions in Simulations of Antarctic Climate and Surface Mass Balance Change during the Coming Century

2008 ◽  
Vol 21 (5) ◽  
pp. 938-962 ◽  
Author(s):  
Gerhard Krinner ◽  
Bérangère Guicherd ◽  
Katia Ox ◽  
Christophe Genthon ◽  
Olivier Magand
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Boundary Conditions ◽  
Mass Balance ◽  
Climate Model ◽  
Sea Surface ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Surface Conditions ◽  
The Antarctic

Abstract This article reports on high-resolution (60 km) atmospheric general circulation model simulations of the Antarctic climate for the periods 1981–2000 and 2081–2100. The analysis focuses on the surface mass balance change, one of the components of the total ice sheet mass balance, and its impact on global eustatic sea level. Contrary to previous simulations, in which the authors directly used sea surface boundary conditions produced by a coupled ocean–atmosphere model for the last decades of both centuries, an anomaly method was applied here in which the present-day simulations use observed sea surface conditions, while the simulations for the end of the twenty-first century use the change in sea surface conditions taken from the coupled simulations superimposed on the present-day observations. It is shown that the use of observed oceanic boundary conditions clearly improves the simulation of the present-day Antarctic climate, compared to model runs using boundary conditions from a coupled climate model. Moreover, although the spatial patterns of the simulated climate change are similar, the two methods yield significantly different estimates of the amplitude of the future climate and surface mass balance change over the Antarctic continent. These differences are of similar magnitude as the intermodel dispersion in the current Intergovernmental Panel on Climate Change (IPCC) exercise: selecting a method for generating boundary conditions for a high-resolution model may be just as important as selecting the climate model itself. Using the anomaly method, the simulated mean surface mass balance change over the grounded ice sheet from 1981–2000 to 2081–2100 is 43-mm water equivalent per year, corresponding to a eustatic sea level decrease of 1.5 mm yr−1. A further result of this work is that future continental-mean surface mass balance changes are dominated by the coastal regions, and that high-resolution models, which better resolve coastal processes, tend to predict stronger precipitation changes than models with lower spatial resolution.

scholarly journals Downscaled surface mass balance in Antarctica: impacts of subsurface processes and large-scale atmospheric circulation

2021 ◽  
Author(s):  
Nicolaj Hansen ◽  
Peter L. Langen ◽  
Fredrik Boberg ◽  
Rene Forsberg ◽  
Sebastian B. Simonsen ◽  
...  
Keyword(s):  
Mass Balance ◽  
Total Mass ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Lagrangian Framework ◽  
Basin Scale ◽  
The Antarctic

Abstract. Antarctic surface mass balance (SMB) is largely determined by precipitation over the continent and subject to regional climate variability related to the Southern Annular Mode (SAM) and other climatic drivers at the large scale. Locally however, firn and snow pack processes are important in determining SMB and the total mass balance of Antarctica and global sea level. Here, we examine factors that influence Antarctic SMB and attempt to reconcile the outcome with estimates for total mass balance determined from the GRACE satellites. This is done by having the regional climate model HIRHAM5 forcing two versions of an offline subsurface model, to estimate Antarctic ice sheet (AIS) SMB from 1980 to 2017. The Lagrangian subsurface model estimates AIS SMB of 2473.5 ± 114.4 Gt per year, while the Eulerian subsurface model variant results in slightly higher modelled SMB of 2564.8 ± 113.7 Gt per year. The majority of this difference in modelled SMB is due to melt and refreezing over ice shelves and demonstrates the importance of firn modelling in areas with substantial melt. Both the Eulerian and the Lagrangian SMB estimates are within uncertainty ranges of each other and within the range of other SMB studies. However, the Lagrangian version has better statistics when modelling the densities. There is a mean bias in modelled density of −24.0 ± 18.4 kg m−3 and −8.2 ± 15.3 kg m−3 for layers less than 550 kg m−3 for the Eulerian and Lagrangian framework, respectively. For layers with a density above 550 kg m−3 the bias is −31.7 ± 23.4 kg m−3 and −35.0 ± 23.7 kg m−3 for the Eulerian and Lagrangian framework, respectively. The mean firn 10 m temperature bias is 0.42–0.52 °C. Further, analysis of the relationship between SMB in individual drainage basins and the SAM, is carried out using a bootstrapping approach. This shows a robust relationship between SAM and SMB in half of the basins (13 out of 27). In general, when SAM is positive there is a lower SMB over the Plateau and a higher SMB on the westerly side of the Antarctic Peninsula, and vice versa when the SAM is negative. Finally, we compare the modelled SMB to GRACE data by subtracting the solid ice discharge, and find that there is a good agreement in East Antarctica, but large disagreements over the Antarctic Peninsula.There is a large difference between published estimates of discharge that make it challenging to use mass reconciliation in evaluating SMB models on the basin scale.

Antarctic Surface Mass Balance from 1980 to 2017

2021 ◽  
Author(s):  
Nicolaj Hansen ◽  
Peter L. Langen ◽  
Fredrik Boberg ◽  
Rene Forsberg ◽  
Sebastian B. Simonsen ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Models ◽  
Climate Model ◽  
Greenland Ice Sheet ◽  
Equal Mass ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Model Version ◽  
Lagrangian Framework ◽  
The Antarctic

&lt;p&gt;The regional climate model HIRHAM5 developed for Greenland ice sheet applications has now been updated to also simulate Antarctic conditions. The outputs of the Antarctic runs have been used to force an offline subsurface model, to give estimates of the Antarctic surface mass balance (SMB) from 1980 to 2017.&amp;#160; Here, we compare two different versions of this offline subsurface model and evaluate how they simulate the physical properties of the uppermost part of the Antarctic firn pack. We find that the total calculated SMB of Antarctica is sensitive to the subsurface model variant.&amp;#160;One model version uses an Eulerian framework, meaning that mass is advected through layers of fixed mass. When snowfall occurs at the surface, it is added to the first layer and an equal mass from that layer is shifted to the underlying layer. The same goes for each layer in the model column, and vice versa for mass loss. The other model version uses a Lagrangian framework for the layer development. Layers evolve through splitting and merging dynamically based on a number of weighted criteria.&lt;/p&gt;&lt;p&gt;The model simulations are validated against in situ observations of firn temperature and subsurface density. We find a mean temperature bias of 0.42-0.52 &amp;#8451;&amp;#160; and a mean bias in modelled density of -24.0&amp;#177;18.4 kg m&amp;#8315;&amp;#179; and&amp;#160; -8.2&amp;#177;15.3 kg m&amp;#8315;&amp;#179; for layers less than 550 kg m&amp;#8315;&amp;#179; for the Eulerian and Lagrangian framework, respectively. For layers with a density above 550 kg m&amp;#8315;&amp;#179; the bais is -31.7&amp;#177;23.4 kg m&amp;#8315;&amp;#179; and -35.0&amp;#177;23.7 kg m&amp;#8315;&amp;#179;&amp;#160; for the Eulerian and Lagrangian framework, respectively. The modelling framework also&amp;#160; affects the resulting&amp;#160; SMB. The Lagrangian framework,&amp;#160; estimates a total SMB&amp;#160; of 2473.5&amp;#177;114.4 Gt yr&amp;#8315;&amp;#185; while the Eulerian framework results in slightly higher modelled SMB of&amp;#160; 2564.8&amp;#177;113.7 Gt yr&amp;#8315;&amp;#185;. The majority for this difference in modelled SMB is pinpointed to the&amp;#160; ice shelves (the SMB over grounded ice only&amp;#160; differs&amp;#160; 30 Gt yr&amp;#8315;&amp;#185;) and&amp;#160; demonstrates the importance of firn modelling in areas with substantial melt. Both the Eulerian and the Lagrangian SMB estimates are within each other's uncertainties and within range of other SMB studies. However, the Lagrangian version has the best statistics for modelling the densities. Given the importance of precipitation to Antarctic SMB, climate models must accurately simulate regional circulation patterns that modulate precipitation rates. We therefore investigate the relationship between SMB in individual drainage basins and the southern annular mode (SAM),&amp;#160; using Monte Carlo simulations. This shows a robust relationship between SAM and SMB in half of the basins (13 out of 27). In general, when SAM is positive there is a lower SMB over the Plateau and a higher SMB on the westerly side of the Antarctic Peninsula, and vice versa when the SAM is negative.&lt;/p&gt;

The vertical structure of atmospheric rivers and their impact in the Atlantic sector of Antarctica from the Year of Polar Prediction observations

2020 ◽  
Author(s):  
Irina V. Gorodetskaya ◽  
Penny M. Rowe ◽  
Heike Kalesse ◽  
Tiago Silva ◽  
Naohiko Hirasawa ◽  
...  
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Vertical Structure ◽  
Surface Mass Balance ◽  
Atlantic Sector ◽  
Surface Mass ◽  
Atmospheric Rivers ◽  
Cloud Properties ◽  
The Antarctic

&lt;p&gt;The Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) had a special observing period (SOP) from November 16, 2018 to February 15, 2019, during which observational activity during austral summer in the Antarctic was greatly enhanced. More than 2000 additional radiosondes were launched during this 3-month period, roughly doubling the amount from routine programs. Further, several YOPP-endorsed projects contributed to enhanced data collection on various atmospheric and oceanic properties, including the Characterization of the Antarctic Atmosphere and Low Clouds (CAALC) project at King George Island (Antarctic Peninsula) and the Dynamics, Aerosol, Cloud And Precipitation Observations in the Pristine Environment of the Southern Ocean (DACAPO-PESO) field experiment in Punta Arenas (Sub-Antarctic Chile). Here we use the YOPP-SH-SOP observations to investigate the vertical structure of atmospheric rivers (ARs), along with their impact on cloud properties, radiative budgets, and precipitation in the Atlantic sector of Antarctica, including coastal areas of sub-Antarctic Chile, the Antarctic Peninsula and Dronning Maud Land (DML).&lt;/p&gt;&lt;p&gt;ARs can transport anomalous heat and moisture from subtropical regions to the Antarctic, with important impacts on Antarctic surface mass balance. On the Antarctic Peninsula, the surface mass balance can be especially sensitive to AR events during summer, when surface temperatures vary around zero and frequent transitions occur between snow and rainfall. The importance of ARs for the coastal DML is also linked to precipitation events during summer, but is more strongly linked to extreme snowfall events (rather than rainfall), and such events have resulted in anomalously high snow accumulation in DML in recent years.&lt;/p&gt;&lt;p&gt;We will present case studies that demonstrate how combining extensive ground-based observations and radiosoundings from stations in the sub-Antarctic and Antarctic allow for detailed characterization of the temporal evolution of AR events. Analysis of the observations and model sensitivity studies (using Polar-WRF) with additional radiosonde assimilation show the influence of ARs on the Antarctic atmospheric, cloud properties and surface precipitation, as well as the challenges in correctly forecasting conditions during such events. Further, we use SOP enhanced radiosonde programs at Neumayer and Syowa stations to investigate the AR signatures in the atmospheric vertical profiles in the DML coastal areas. The AR events observed during YOPP-SH are put in the context of the longer-term radiosonde observations using 10 years (from 2009 to 2019) of the Integrated Global Radiosonde Archive (IGRA) Version 2 data. The increased frequency of radiosonde observations during YOPP was crucial for elucidating the important contribution these rare events make to the moisture transport towards Antarctica. They also showed an added value in improving the forecast of weather conditions during AR events, which have important consequences for air, ship and station operations in Antarctica.&lt;/p&gt;

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