Monitoring Fjord Circulation Using Iceberg-Mounted GPS as Real-Time Drifters

摘要

Ocean circulation in Greenland's large glacial fjords is one mechanism that controls the rate of submarine melting at the termini of Greenland's outlet glaciers. Here we use hourly position data from GPS units deployed on ten large (>100 meter), deep-keeled icebergs in Sermilik Fjord, SE Greenland. We observe and quantify the motions of these icebergs moving through the mélange, fjord, and shelf regimes. In the mélange, icebergs move outward with glacier flow until pushed loose by large calving events. In the fjord, high frequency, low amplitude tidally-driven motions are superimposed on dominant 1-5 day events with net velocities exceeding 0.1 m/s. We interpret these events as two-layer, intermediary circulation driven by winds along the shelf, where icebergs travel southward in the East Greenland Coastal Current. These results showcase the potential of this novel instrumentation to link iceberg motion with circulation in any large glacial fjord.