Short-term changes in Antarctica's ice shelves are key to predicting their long-term fate
Abstract
Antarctic ice loss is accelerating and will soon become the largest contributor to sea-level rise. Antarctica's ice shelves can provide mechanical support to "buttress" the seaward flow of grounded ice, so that ice-shelf thinning and retreat result in enhanced ice discharge to the ocean. Ice shelves are susceptible to changes in forcing from the atmosphere and ocean, which both change on multiple timescales to modify mass gains and losses at the surface and base. The only viable way to monitor the full extent of the ice shelves while capturing the relevant time scales is by satellite. We discuss results from analyses of time series of ice-shelf surface elevations derived from satellite radar altimetry from four ESA satellites (ERS-1 & -2, Envisat, CryoSat-2) between 1994 and 2017. The continuous 25-year time series are sufficiently long to resolve patterns of multi-year variability linked to atmospheric and oceanic processes. We focus on the variability present in the records, providing more information that can be obtained from linear trends reported in prior studies, and show two examples of this approach. The Pacific-sector ice shelves respond strongly to tropical ocean variability, with El Niño events increasing both snowfall and ocean-driven basal melting. The height increase by the added low-density snow exceeds the height decrease by loss of denser basal ice. However, mass loss by this basal melting exceeds mass gain from snow, so ice shelves lose mass overall; the opposite occurs during La Niñas. On the Antarctic Peninsula, where several ice shelves have collapsed or significantly retreated since the 1990's, ice shelf heights have increased since 2009, in some cases recovering most of the decline reported previously. We connect this to reduced summertime melting of the surface, even as the ocean continues to melt the base and remove mass. These examples demonstrate the capability of long and continuous records from satellite altimeters, allowing us to improve our understanding of what is causing ice-shelf mass changes and stability. As the satellite record lengthens, e.g. with NASA's ICESat-2 (launched Sept 2018), we expect to reach the point where we can confidently include these processes in models of ice-sheet response to climate changes, which will improve projections of future sea level rise.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C23A..02F
- Keywords:
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- 0702 Permafrost;
- CRYOSPHEREDE: 0736 Snow;
- CRYOSPHEREDE: 0738 Ice;
- CRYOSPHEREDE: 0750 Sea ice;
- CRYOSPHERE