Seasonal Variability of Basal Melt under the Nansen Ice Shelf, Antarctica
Abstract
The Nansen Ice Shelf (NIS) is located beside the Terra Nova Bay polynya in the Ross Sea, Antarctica. Many oceanographic measurement campaigns have shown the cold Ice Shelf Water (ISW) flowing out from the ocean cavity beneath the NIS. We investigated the spatial and temporal variation of basal melt under the ice shelf in order to understand the formation of ISW within the cavity. The steady-state basal melt distribution based on mass conservation of the ice shelf delineates that the strongest melt occurs near the grounding line of Priestly Glacier. An ApRES (Autonomous phase-sensitive Radar Echo Sounding)instrumentdeployed near the grounding line, and another deployed in the middle of the ice shelf, have recorded the basal melt rates for several months. An interesting feature is a significant temporal variation in the basal melt rate near the grounding line: the basal melt rate exceeded 5 m/yr in the austral summer, compared with very much lower values during winter. The perturbations of basal melt rates are partly correlated with the wind speed in front of NIS, suggesting that the winds in front of ice shelf could be a driving force to control the basal melt for the innermost regions of the ice shelf. In order to understand the apparent seasonal variation in basal melting, we modeled the ocean circulation beneath the ice shelf using ROMS (Regional Ocean Modeling System). Using a bathymetry enhanced by the inversion of helicopter-based gravity survey data, the ROMS model successfully reproduces the strong seasonality in the heat transport beneath the ice shelf and in the basal melt. The results imply that the seasonal wind forcing drives the ocean circulation in the cavity to produce the seasonality in the basal melt and the outflow of ISW.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C21D1475L
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0728 Ice shelves;
- CRYOSPHERE;
- 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL