Warm Atlantic inflow toward the Helmheim-Sermilik glacier-fjord system, South-East Greenland: Insights from a high-resolution Eulerian-Lagrangian model study.

Abstract:

The recent rapid increase in mass loss from the Greenland ice sheet has been primarily attributed to the acceleration of outlet glaciers. Helmheim-Sermilik is one of the major glacier-fjord systems in southeast Greenland that has been observed to retreat and nearly double its flow speed during the past decade. One possible cause of this acceleration is enhanced melting at the glacier terminus driven by the advection of warm waters of Atlantic origin over the East Greenland Shelf and into the Sermilik fjord (38E,66N).

We use a high resolution configuration of the MITgcm circulation model (2km- and 15m grid spacing in horizontal and vertical directions, respectively), forced by Era-Interim winds and with a bathymetry updated by recent ship- and seal-borne measurements, to study intra-seasonal variability of the intrusions of the warm Atlantic water on the East Greenland Shelf advected toward the Sermilik fjord. The modeled T-S properties in the vicinity of the fjord sill are in good agreement with available observations. The warm inflow into the fjord occurs in quasi-oscillatory pulses of 1-10 day periodicity and of 50-200m vertical extent. The inflow occurs for (10-40)% time of the year (depending on depth), with a slight preference for winter months. The velocity and heat flux distributions are nearly Gaussian at 300m depth and non-Gaussian (Kurtosis>7) at greater depths, with a long positive tail corresponding to high (>0.4m/s) inflow events in winter. We quantify the relative importance of synoptic winds and internal dynamics in generating this variability. The Eulerian analysis is supplemented by backward tracing of O(10,000) Lagrangian particles revealing pathways and water-mass transformation of the inflow that is primarily fed by Irminger Current intruding on the shelf in the vicinity of the Spill Jet section (32E,65N) and channeled through the Sermilik Deep Opening. We ephasize the importance of proper representation of topographic features on the shelf steering the modeled inflow, and of proper temporal and spatial resolution of the warm inflow events into the fjord.