What lies beneath: using sea surface temperatures to reconstruct sub-surface continental shelf ocean variability near Helheim Glacier, Greenland
Abstract
The Greenland ice sheet contributes one-quarter of global sea level rise each year and one-third of its mass loss occurs at outlet glaciers. Melting at the ice-ocean boundary through interactions with relatively warm ocean water is one mechanism for this loss. Satellite-derived sea surface temperatures (SST) may hold clues to fjord heat content and ice-ocean interactions where no in situ observations exist, but to date they have been rarely used.
Here, we explore the utility of SSTs using Sermilik Fjord near Helheim Glacier as a case study. Within Sermilik Fjord and on the inner continental shelf, warm Atlantic Water (AW) flows below 150-250 m with cold, fresh Polar Water above, while outside of the shelf break in the Irminger Sea, AW resides from the surface to depths below 600 m. Little is known about the water mass interactions between the offshore Irminger Sea and the fjord, and the mechanisms linking the two. We derive SSTs from the MODIS Level 3 gridded SST product to investigate the variability of water masses and mechanisms driving them within the Helheim system from 2000 to present. The SSTs reveal a permanent, but variable in properties, bifurcation of AW throughout the water column that transports heat onto the continental shelf along a bathymetric trough toward Sermilik Fjord. Using deep water temperatures from a mooring near the fjord mouth and atmospheric reanalysis data from ERA5, we show that SSTs along the bifurcation reflect changes in both air and ocean temperature, though differently between summer and winter. Winds serve as a control on the extent of the bifurcation observed in SSTs, providing insight into the changes in transport of AW into the trough toward the fjord. Peak SSTs and maxima in the horizontal extent of the bifurcation occur on the shelf in 2003, 2010, and 2014-2018. In contrast, we observe a general cooling of AW offshore since 2012, suggesting that AW source temperature may not be the only important driver of the variability of waters on the shelf that ultimately feed into the fjords and bring heat to Helheim. Our work suggests SSTs can provide new insight into ocean variability that can better inform our understanding of the drivers of glacier change.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C21D1484S
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0728 Ice shelves;
- CRYOSPHERE;
- 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL