Ocean surface circulation in front of Greenland glaciers derived from Ground Portable Radar Interferometry.

Abstract:

Marine-terminating glaciers control the majority of the Greenland Ice Sheet mass loss other than surface melt. These glaciers are modulated by processes that include ocean temperature, tidal cycle, subglacial hydrology, mélange concentration, and calving of grounded ice blocks. To understand the dynamics of these glaciers, it is important to document the motion of the surface waters in front of the glacier because this motion is indicative of the regime of horizontal mixing of the water layers in front of the glacier. We do this by tracking floating ice movement in the fjord using Gamma Portable Radar Interferometer-II (GPRI) data. We employ data collected in July 2016 in front of Kangilernata glacier and in July 2018 in front of Kujalleq glacier. The GPRI scanned the fjord waters, drifting icebergs, and glacier fronts every 3 minutes, yielding a time series of radar images showing a dynamic ocean surface, with regular horizontal currents, mixed with eddies and gravity waves generated by calving events. A shallow sill 3 km from the front of Kujalleq glacier is found to impact ocean circulation and iceberg motion. On Kangilernata, we observe complex interactions between plumes of subglacial discharge, calving events, and a pattern of tidally- and wind-driven horizontal circulation of ocean waters in the fjord. We conclude on the nature of ocean circulation in these fjords and how the horizontal re-circulation of the ocean waters may affect the magnitude of ice-ocean interactions at glacier margins. The work was performed at UCI and was funded by a NASA grant from the Cryosphere Science Program and the Donald Bren Endowment at UCI.