Meeting Documents

Ice-Sheet Melt Drives Vigorous Nutrient Upwelling and Enhanced Coastal Productivity at Sermeq Kujalleq, Greenland’s Most Active Glacier

Abstract

Over the past several decades, increasing Arctic air temperatures have caused extensive melt on the surface of the Greenland Ice Sheet. Unlike terrestrial runoff, surface ice-sheet melt drains through glacier cracks and crevasses and is often discharged several hundred meters below the ocean surface at glacier outlets. The emergence of this fresh, buoyant subglacial discharge at the grounding line generates turbulent upwelling plumes that can exceed more than 1 Sverdrup of total volume flux during summer, rivaling major upwelling systems in the global ocean. Recent evidence has shown that, similar to other upwelling regions, Greenland’s plumes upwell substantial nutrient fluxes from depth, contributing to enhanced productivity within fjords and on the shelf. Here we use a downscaled-model approach, combined with the ECCO-Darwin ocean biogeochemistry model, to investigate plume-driven upwelling from Sermeq Kujalleq — one of the most active glaciers in Greenland. We test the sensitivity of ice-sheet melt and associated upwelling on nutrient availability and productivity by comparing simulations with and without subglacial discharge in years of high/low melt. We find that the upwelling plume at Sermeq Kujalleq substantially increases nutrient concentrations in the photic zone, promoting phytoplankton growth in the late summer inside Disko Bay and further offshore on the shelf. In addition to providing a quantitative estimate of the ocean-ice processes that modulate nutrients and productivity in coastal waters, this study also provides a framework by which realistic, variable-depth ice-sheet discharge could be implemented in coarse-resolution ocean models coupled with biogeochemistry.