Sensitivity of submarine melting on North East Greenland towards ocean forcing

• Main Authors: Anhaus, Philipp, Smedsrud, Lars H., Årthun, Marius, Straneo, Fiammetta
• Format: Text
• Language: English
• Published: 2019
• Subjects: Greenland; East Greenland; Ice Sheet; Ice Shelf
• Online Access: https://doi.org/10.5194/tc-2019-35; https://tc.copernicus.org/preprints/tc-2019-35/

The Nioghalvfjerdsbræ (79NG) is a floating ice tongue on Northeast Greenland draining a large part of the Greenland Ice Sheet. A CTD profile from a rift on the ice tongue close to the northern front shows that Atlantic Water (AW) is present in the cavity below, with maximum temperature of approximately 1 °C at 610 m depth. The AW present in the cavity thus has the potential to drive submarine melting along the ice base. Here, we simulate melt rates from the 79NG with a 1D numerical Ice Shelf Water (ISW) plume model. A meltwater plume is initiated at the grounding line depth (600 m) and rises along the ice base as a result of buoyancy contrast to the underlying AW. Ice melts as the plume entrains the warm AW. Maximum simulated melt rates are 50–76 m yr −1 within 10 km of the grounding line. Within a zone of rapid decay between 10 km and 20 km melt rates drop to roughly 6 m yr −1 . Further downstream, melt rates are between 15 m yr −1 and 6 m yr −1 . The melt-rate sensitivity to variations in AW temperatures is assessed by forcing the model with AW temperatures between 0.1–1.4 °C, as identified from the ECCOv4 ocean state estimate. The melt rates increase linearly with rising AW temperature, ranging from 10 m yr −1 to 21 m yr −1 along the centerline. The corresponding freshwater flux ranges between 11 km 3 yr −1 (0.4 mSv) and 30 km 3 yr −1 (1.0 mSv), which is 5 % and 12 % of the total freshwater flux from the Greenland Ice Sheet since 1995, respectively. Our results improve the understanding of processes driving submarine melting of marine-terminating glaciers around Greenland, and its sensitivity to changing ocean conditions.