Mass Loss in the Greenland and Antarctica Ice Sheets: 2002-2014

2015 ◽  
Author(s):  
Jamal Munshi
Keyword(s):  
Mass Loss ◽  
Ice Sheets

scholarly journals Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes

Science ◽  
2020 ◽  
Vol 368 (6496) ◽  
pp. 1239-1242 ◽  
Author(s):  
Ben Smith ◽  
Helen A. Fricker ◽  
Alex S. Gardner ◽  
Brooke Medley ◽  
Johan Nilsson ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Mass Loss ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Snow Accumulation ◽  
Mass Change ◽  
Laser Altimetry ◽  
Ice Shelves ◽  
Ice Cloud

Quantifying changes in Earth’s ice sheets and identifying the climate drivers are central to improving sea level projections. We provide unified estimates of grounded and floating ice mass change from 2003 to 2019 using NASA’s Ice, Cloud and land Elevation Satellite (ICESat) and ICESat-2 satellite laser altimetry. Our data reveal patterns likely linked to competing climate processes: Ice loss from coastal Greenland (increased surface melt), Antarctic ice shelves (increased ocean melting), and Greenland and Antarctic outlet glaciers (dynamic response to ocean melting) was partially compensated by mass gains over ice sheet interiors (increased snow accumulation). Losses outpaced gains, with grounded-ice loss from Greenland (200 billion tonnes per year) and Antarctica (118 billion tonnes per year) contributing 14 millimeters to sea level. Mass lost from West Antarctica’s ice shelves accounted for more than 30% of that region’s total.

scholarly journals Sensitivity of centennial mass loss projections of the Amundsen basin to the friction law

2019 ◽  
Vol 13 (1) ◽  
pp. 177-195 ◽  
Author(s):  
Julien Brondex ◽  
Fabien Gillet-Chaulet ◽  
Olivier Gagliardini
Keyword(s):  
Mass Loss ◽  
Ice Sheets ◽  
Effective Pressure ◽  
Amundsen Sea ◽  
Friction Law ◽  
Mass Losses ◽  
Grounding Line ◽  
Initial States ◽  
Basal Shear ◽  
Parameter Values

Abstract. Reliable projections of ice sheets' future contributions to sea-level rise require models that are able to accurately simulate grounding-line dynamics, starting from initial states consistent with observations. Here, we simulate the centennial evolution of the Amundsen Sea Embayment in response to a prescribed perturbation in order to assess the sensitivity of mass loss projections to the chosen friction law, depending on the initialisation strategy. To this end, three different model states are constructed by inferring both the initial basal shear stress and viscosity fields with various relative weights. Then, starting from each of these model states, prognostic simulations are carried out using a Weertman, a Schoof and a Budd friction law, with different parameter values. Although the sensitivity of projections to the chosen friction law tends to decrease when more weight is put on viscosity during initialisation, it remains significant for the most physically acceptable of the constructed model states. Independently of the considered model state, the Weertman law systematically predicts the lowest mass losses. In addition, because of its particular dependence on effective pressure, the Budd friction law induces significantly different grounding-line retreat patterns than the other laws and predicts significantly higher mass losses.

scholarly journals A 14-yr Circum-Antarctic Iceberg Calving Dataset Derived from Continuous Satellite Observations

2021 ◽  
Author(s):  
Mengzhen Qi ◽  
Yan Liu ◽  
Jiping Liu ◽  
Xiao Cheng ◽  
Qiyang Feng ◽  
...  
Keyword(s):  
Mass Loss ◽  
Ice Sheets ◽  
Data Repository ◽  
Main Process ◽  
Ice Shelves ◽  
Radar Images ◽  
Wilkes Land ◽  
Iceberg Calving ◽  
Interval Type ◽  
The Antarctic

Abstract. Iceberg calving is the main process that facilitates the dynamic mass loss of ice sheets into the ocean, which accounts for approximately half of the net mass loss of all Antarctic ice shelves. Fine-scale calving variability observations can help reveal the involved calving mechanisms and identify the principal processes that influence how the changing climate affects the mass loss of ice sheets. Iceberg calving from specific ice shelves or regions has been monitored before, but there is still a lack of consistent, long-term and high-precision records on independent calving events for all Antarctic ice shelves. In this study, we developed a circum-Antarctic annual iceberg calving product measuring every independent calving event larger than 1 km2 that occurred from August 2005 to August 2019. We first simulated the expansion of the coastline according to ice velocity, and then manually delineated the calved areas, which are considered to be the differences between the simulated coastline and the actual coastline derived from the corresponding satellite imagery, based on 15 years of continuous multisource optical and synthetic aperture radar images. This product provides detailed information on each calving event, including the associated year of occurrence, area, size, average thickness, mass, recurrence interval, type, and measurement uncertainties. In total, 1786 annual calving events occurred on the Antarctic ice shelves from August 2005 to August 2019. The average annual calving area was measured as 3411.4 km2 with an uncertainty value of 17.1 km2, and the average calving rate was measured as 771.1 Gt/yr with an uncertainty value of 10.2 Gt/yr. The calving frequency, area, and mass fluctuated moderately during the first decade, followed by a dramatic increase from 2015/16 to 2018/19. During the dataset period, large ice shelves, such as the Ronne-Filchner, Ross and Amery Ice Shelves, advanced with low calving frequency, while small and medium-sized ice shelves retreated and calved more frequently. Iceberg calving is most prevalent in West Antarctica, followed by the Antarctic Peninsula and Wilkes Land in East Antarctica. The annual circum-Antarctic iceberg calving dataset provides consistent and precise calving observations with the longest time coverage. The dataset provides multidimensional variables for each independent calving event that can be used to study detailed spatiotemporal variations in Antarctic iceberg calving. The dataset can also be used to study ice sheet mass balance, calving mechanisms and the responses of iceberg calving to climate change. The dataset is shared via Global Change Data Repository (href="http://www.geodoi.ac.cn/WebEn/doi.aspx?Id=1516), and entitled Annual iceberg calving dataset of the Antarctic ice shelves (2005–2019) with DOI: https://doi.org/10.3974/geodb.2020.04.09.V1.

scholarly journals Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

2015 ◽  
Vol 9 (1) ◽  
pp. 197-215 ◽  
Author(s):  
T. Dunse ◽  
T. Schellenberger ◽  
J. O. Hagen ◽  
A. Kääb ◽  
T. V. Schuler ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheets ◽  
Glacier Mass Balance ◽  
Internal Dynamic ◽  
Svalbard Archipelago ◽  
Flow Acceleration ◽  
Ice Cap ◽  
Surface Melt

Abstract. Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the polar regions. Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg discharge of 4.2±1.6 Gt a−1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. With the seawater displacement by the terminus advance accounted for, the related sea-level rise contribution amounts to 7.2±2.6 Gt a−1. This rate matches the annual ice-mass loss from the entire Svalbard archipelago over the period 2003–2008, highlighting the importance of dynamic mass loss for glacier mass balance and sea-level rise. The active role of surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities. Given sustained climatic warming and rising significance of surface melt, we propose a potential impact of the hydro-thermodynamic feedback on the future stability of ice-sheet regions, namely at the presence of a cold-based marginal ice plug that restricts fast drainage of inland ice. The possibility of large-scale dynamic instabilities such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise.

scholarly journals Deep Learning on Airborne Radar Echograms for Tracing Snow Accumulation Layers of the Greenland Ice Sheet

2021 ◽  
Vol 13 (14) ◽  
pp. 2707
Author(s):  
Debvrat Varshney ◽  
Maryam Rahnemoonfar ◽  
Masoud Yari ◽  
John Paden ◽  
Oluwanisola Ibikunle ◽  
...  
Keyword(s):  
Deep Learning ◽  
Mass Loss ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Airborne Radar ◽  
Snow Layer ◽  
Surface Mass ◽  
Radar Images

Climate change is extensively affecting ice sheets resulting in accelerating mass loss in recent decades. Assessment of this reduction and its causes is required to project future ice mass loss. Annual snow accumulation is an important component of the surface mass balance of ice sheets. While in situ snow accumulation measurements are temporally and spatially limited due to their high cost, airborne radar sounders can achieve ice sheet wide coverage by capturing and tracking annual snow layers in the radar images or echograms. In this paper, we use deep learning to uniquely identify the position of each annual snow layer in the Snow Radar echograms taken across different regions over the Greenland ice sheet. We train with more than 15,000 images generated from radar echograms and estimate the thickness of each snow layer within a mean absolute error of 0.54 to 7.28 pixels, depending on dataset. A highly precise snow layer thickness can help improve weather models and, thus, support glaciological studies. Such a well-trained deep learning model can be used with ever-growing datasets to aid in the accurate assessment of snow accumulation on the dynamically changing ice sheets.

scholarly journals Sensitivity of centennial mass loss projections of the Amundsen basin to the friction law

2018 ◽  
Author(s):  
Julien Brondex ◽  
Fabien Gillet-Chaulet ◽  
Olivier Gagliardini
Keyword(s):  
Mass Loss ◽  
Ice Sheets ◽  
Future Contribution ◽  
Amundsen Sea ◽  
Friction Law ◽  
Mass Losses ◽  
Grounding Line ◽  
Initial States ◽  
Basal Shear ◽  
Parameter Values

Abstract. Reliable projections of ice sheets future contribution to sea level rise require models able to accurately simulate grounding line dynamics, starting from initial states consistent with observations. Here, we simulate the centennial evolution of the Amundsen Sea Embayement in response to a schematic perturbation in order to assess the sensitivity of mass loss projections to the chosen friction law, depending on the initialisation strategy. To this end, three different model states are constructed by inferring both the initial basal shear stress and viscosity fields with various relative weights. Then, starting from each of these model states, prognostic simulations are carried out using a Weertman, a Schoof and a Budd friction law, with different parameter values. Independently of the considered model state, the Weertman law systematically predicts the lowest mass losses. Although the sensitivity of projections to the chosen friction law tends to decrease when more weight is put on viscosity during initialisation, it remains significant for the most physically acceptable of the constructed model states. In addition, because of its particular dependence on effective pressure, the Budd friction law induces significantly different GL retreat patterns than the other laws and predicts much higher mass losses.

scholarly journals Brief communication: A roadmap towards credible projections of ice sheet contribution to sea level

2021 ◽  
Vol 15 (12) ◽  
pp. 5705-5715
Author(s):  
Andy Aschwanden ◽  
Timothy C. Bartholomaus ◽  
Douglas J. Brinkerhoff ◽  
Martin Truffer
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Mass Change ◽  
Recent Effort ◽  
Government Investment ◽  
Formal Process ◽  
The Future

Abstract. Accurately projecting mass loss from ice sheets is of critical societal importance. However, despite recent improvements in ice sheet models, our analysis of a recent effort to project ice sheet contribution to future sea level suggests that few models reproduce historical mass loss accurately and that they appear much too confident in the spread of predicted outcomes. The inability of models to reproduce historical observations raises concerns about the models' skill at projecting mass loss. Here we suggest that uncertainties in the future sea level contribution from Greenland and Antarctica may well be significantly higher than reported in that study. We propose a roadmap to enable a more realistic accounting of uncertainties associated with such forecasts and a formal process by which observations of mass change should be used to refine projections of mass change. Finally, we note that tremendous government investment and planning affecting tens to hundreds of millions of people is founded on the work of just a few tens of scientists. To achieve the goal of credible projections of ice sheet contribution to sea level, we strongly believe that investment in research must be commensurate with the scale of the challenge.

scholarly journals Destabilisation of an Arctic ice cap triggered by a hydro-thermodynamic feedback to summer-melt

2014 ◽  
Vol 8 (3) ◽  
pp. 2685-2719 ◽  
Author(s):  
T. Dunse ◽  
T. Schellenberger ◽  
A. Kääb ◽  
J. O. Hagen ◽  
T. V. Schuler ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Polar Regions ◽  
Svalbard Archipelago ◽  
Flow Acceleration ◽  
Ice Cap ◽  
Global Sea Level

Abstract. Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the Polar Regions. Here we present continuous GPS measurements and satellite synthetic aperture radar based velocity maps from the Austfonna ice cap, Svalbard, that demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of the ice cap's largest drainage basin, Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a−1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. After accounting for the terminus advance, the related sea-level rise contribution of 7.2 ± 2.6 Gt a−1 matches the recent annual ice-mass loss from the entire Svalbard archipelago. Our study highlights the importance of dynamic glacier wastage and illuminates mechanisms that may trigger a sustained increase in dynamic glacier wastage or the disintegration of ice-sheets in response to climate warming, which is acknowledged but not quantified in global projections of sea-level rise.

scholarly journals Ice-sheet mass balance: assessment, attribution and prognosis

2007 ◽  
Vol 46 ◽  
pp. 1-7 ◽  
Author(s):  
Richard B. Alley ◽  
Matthew K. Spencer ◽  
Sridhar Anandakrishnan
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Balance Assessment ◽  
Additional Mass ◽  
Recent Warming ◽  
The Future ◽  
Ice Sheet Mass Balance ◽  
Antarctic Ice Sheets

AbstractContrary to prior expectations that warming would cause mass addition averaged over the Greenland and Antarctic ice sheets and over the next century, the ice sheets appear to be losing mass, at least partly in response to recent warming. With warming projected for the future, additional mass loss appears more likely than not.

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