Abstract
The Antarctic ice sheet (AIS) has the greatest potential for global sea level rise. This study simulates AIS ice creeping, sliding, tabular calving, and estimates the total mass balances, using a recently developed, advanced ice dynamics model, known as SEGMENT-Ice. SEGMENT-Ice is written in a spherical Earth coordinate system. Because the AIS contains the South Pole, a projection transfer is performed to displace the pole outside of the simulation domain. The AIS also has complex ice-water-granular material-bedrock configurations, requiring sophisticated lateral and basal boundary conditions. Because of the prevalence of ice shelves, a ‘girder yield’ type calving scheme is activated. The simulations of present surface ice flow velocities compare favorably with InSAR measurements, for various ice-water-bedrock configurations. The estimated ice mass loss rate during 2003–2009 agrees with GRACE measurements and provides more spatial details not represented by the latter. The model estimated calving frequencies of the peripheral ice shelves from 1996 (roughly when the 5-km digital elevation and thickness data for the shelves were collected) to 2009 compare well with archived scatterometer images. SEGMENT-Ice’s unique, non-local systematic calving scheme is found to be relevant for tabular calving. However, the exact timing of calving and of iceberg sizes cannot be simulated accurately at present. A projection of the future mass change of the AIS is made, with SEGMENT-Ice forced by atmospheric conditions from three different coupled general circulation models. The entire AIS is estimated to be losing mass steadily at a rate of ~120 km3/a at present and this rate possibly may double by year 2100.
Highlights
At present the Earth’s climate is in an interglacial period
Model simulated land ice mass losses and features of tabular calving during the past decade are compared with available measurements, and SEGMENTIce predictions are presented of the mass changes for the Antarctic ice sheet (AIS) for the twenty-first century, under a range of future scenarios provided by coupled general circulation models (CGCMs)
The Jacobian involved for transferring between two coordinates is, for any function F: Fig. 2 The general curvilinear system in SEGMENT-Ice. a the spherical rotating earth reference system, (b) the terrain-following sigma coordinate system transfer, and (c) is the stretched vertical grid stencil over Amery Ice Shelf oh r;/ H
Summary
At present the Earth’s climate is in an interglacial period. Predictions based on the eccentricity in the Earth’s orbit suggest that interglacial conditions possibly could continue for another 10 kyr (Berger and Loutre 2002). The Gravity Recovery And Climate Experiment (GRACE) data measure the sum total of ice mass change and post glacial rebound (PGR) for an area, which show a positive rate over the entire Antarctic continent (Velicogna and Wahr 2006). As it cannot differentiate between phases of water, changes for floating ice (ice shelves) cannot be recorded by the GRACE satellite pair. Model simulated land ice mass losses and features of tabular calving during the past decade are compared with available measurements, and SEGMENTIce predictions are presented of the mass changes for the AIS for the twenty-first century, under a range of future scenarios provided by CGCMs. Section 5 draws conclusions resulting from this study
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