Time-varying freshwater fluxes from Antarctic ice shelves
Abstract
Recent Antarctic ice-sheet mass loss is primarily driven by the dynamic response of grounded ice to a decrease in buttressing as ice shelves lose mass by excess calving and basal melting. Large-scale observations of ice-shelf melt rates, and corresponding freshwater fluxes, are difficult to make using in-situ techniques but can be inferred using height changes derived from satellite and airborne altimetry, satellite-derived ice velocities, and auxiliary data from regional atmospheric and firn modeling. Published estimates of continent-wide basal melt rates from altimetry are all based on ice-shelf height data from the laser altimeter onboard NASA's Ice Cloud and land Elevation Satellite (ICESat), which operated from 2003 to 2009. However, because of instrument limitations, estimated melt rates from ICESat are only provided as five-year time-averaged values with no information on temporal variability. Furthermore, with the exception of the large southern ice shelves (Filchner-Ronne and Ross), ICESat poorly resolves spatial structure of trends due to orbit and sampling characteristics, including data loss when clouds are present. We present a high-resolution record of Lagrangian, time-varying height changes from Ku-band CryoSat-2 radar altimetry (2010-present), and interpret our results in the context of the multi-decadal (1994-present) Eulerian estimates from ERS-1, ERS-2, Envisat, and CryoSat-2. Using these records, we estimate time series of freshwater fluxes around Antarctica, which can provide crucial constraints for models representing Antarctic coastal ocean state and ice shelf melting. We consider uncertainties from radar signal penetration and firn modeling to determine the spatially-dependent minimum time scales for which temporal variability of freshwater fluxes can be assessed. The ICESat-2 laser altimeter mission, scheduled to launch in September 2018, will provide measurements of ice shelf height at higher accuracy and precision than current ice-observing satellites. If data from the ATLAS instrument onboard the ICESat-2 satellite are available by the time of this presentation, we will provide an initial assessment of instrument performance over ice shelves and discuss how these data can be used in future to improve estimates of freshwater fluxes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C12B..08A
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0726 Ice sheets;
- CRYOSPHEREDE: 0728 Ice shelves;
- CRYOSPHEREDE: 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL