OPP-PRF: Submesoscale Fjord Variability and Its Influence on Glacial Melt

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Understanding the processes at the boundary where ice and ocean meet, specifically at the faces of melting glaciers, remains a key challenge in our ability to predict the melting and retreat of these glaciers and their influence on sea level rise. The meltwater from these glaciers also has far-reaching implications for the rapidly-changing polar oceans. Recent observations and numerical simulations find unexpectedly high melting at the faces of submerged glaciers, and recent theory suggests that one possible explanation is the existence of relatively small-scale (submesoscale) ocean currents within glacial fjords (which are narrow, deep, and submerged valleys connecting glaciers to the open ocean). This research will connect the submesoscale ocean currents with the physics at the ice-ocean boundary layer to develop improved physical models that take into account the multiscale effects of ocean circulation near ice-ocean boundaries. The research is of critical importance to society since it will improve our understanding of how ocean circulation in fjords contributes to glacial melt and retreat, which will help improve projections of sea level rise and changes in marine life in these regions. This project will enable the training of a postdoctoral researcher (as the primary investigator) and provide funds to mentor two summer undergraduate students. Currently, there are order-of-magnitude discrepancies between observed and predicted melt rates at marine-terminating glaciers. Recent models suggest that the energetic dynamics at the ice-ocean boundary layer and submesoscale variability within fjords potentially contribute to these elevated melt rates. These discrepancies are hypothesized to arise from multi-scale ice-ocean interactions, with important processes and melt-circulation feedbacks across these scales that together contribute to an amplified melt rate. High-resolution submesoscale-resolving simulations of fjords and Large Eddy Simulations (LES) of the glacial ice-ocean boundary will be used to test the hypothesis that fjord submesoscale variability is a primary source of eddy kinetic energy within fjords and is potentially excited by a combination of shear, convective, and centrifugal instabilities driven by melt over the entire glacial front. These results will be used to test and develop improved parameterizations for the ice-ocean boundary layer that are consistent with previous and ongoing observations at the submarine face of LeConte Glacier, Alaska. These improved parameterizations will reduce uncertainty in glacial melt rate estimates (and thus, sea level rise projections) and improve our understanding of fjord circulation and its influence on polar coastal biogeochemistry. These improvements also likely to benefit our understanding of other types of ice-ocean boundaries.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.