Wood, M., Carroll, D., Fenty, I.G., and Khazendar, A. (2024)
Presented at:
Ocean Sciences Meeting 2024Over 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 flows through glacier cracks and crevasses and is often discharged several hundred meters below the ocean surface. This fresh subglacial discharge generates turbulent upwelling plumes that can exceed more than 1 Sverdrup of total volume flux in the summertime, rivaling upwelling rates in the major upwelling systems in the global ocean. Recent evidence has shown that, similar to other upwelling regions, Greenland’s plumes upwell substantial nutrient fluxes, contributing to enhanced productivity within fjords and on the continental shelf. Here we use a downscaled-model approach with the MIT General Circulation Model (MITgcm) coupled with biogeochemistry and ecology (Darwin) to investigate submarine melt and upwelling from Sermeq Kujalleq — one of the largest glaciers in Greenland. We begin with the coarse-resolution, global ECCO-Darwin ocean biogeochemistry state estimate (15 km) and downscale into a regional model (3–4 km) that resolves circulation on the continental shelf. We then further downscale into a fjord-scale model (500 m) that resolves submesoscale circulation inside the narrow Ilullisat Icefjord. We test the influence of glacier melt and associated upwelling on nutrient availability and productivity by comparing simulations with and without subglacial discharge. The upwelling plume is implemented with a plume parameterization for MITgcm. We find that the upwelling plume at Sermeq Kujalleq provides significant increases in nutrient availability in the photic zone, promoting phytoplankton growth in the late summer in Disko Bay and on the continental shelf. In addition to providing a multi-decadal estimate of the processes modulating nutrient and productivity variability resulting from recent ice-sheet change, this study also provides a framework by which realistic, variable-depth ice-sheet discharge could be implemented in coarse-resolution models coupled with biogeochemistry.
