Can we observe depth-variable iceberg melt rates?

The increasing input of freshwater to the subpolar North Atlantic, both through glacier meltwater runoff and the melting of calved icebergs, has significant implications for fjord circulation. However, the magnitude and timing of this meltwater input has been challenging to quantify because iceberg melt rates are largely unknown. Here we use data from a simultaneous glaciological and oceanographic field campaign conducted in Sermilik Fjord, southeast Greenland, during the summers of 2018 and 2019 to map the submarine geometry of large icebergs and use repeat surveys to directly measure changes in iceberg geometry with depth. We use a combination of coincident ship-based multibeam submarine scans and ocean hydrography measurements to construct a detailed picture of melt rate and meltwater injection with depth. This synthesis of in situ iceberg melt measurements in combination with adjacent ocean measurements is amongst the first of its kind. Here, we will discuss the results of the 2018 and 2019 field campaigns, the implications of variable iceberg meltwater injection throughout the water column, and comparisons to standard melt rate parameterizations and tidewater glacier submarine melt rate calculations.