Flow aware parameterizations invigorate the simulated ocean circulation
under the Pine Island ice shelf, West Antarctica
Abstract
Warm, subsurface ocean waters that access ice shelves in the Amundsen
Sea are likely to be a key driver of high meltrates and ice shelf
thinning. Numerical models of the ocean circulation have been essential
for gaining understanding of the mechanisms responsible for heat
delivery and meltrate response, but a number of challenges remain for
simulations that incorporate this region. Here, we develop a suite of
numerical experiments to explore how sub ice shelf cavity circulation
and meltrate patterns are impacted by parameterization schemes for (1)
subgrid-scale ocean turbulence, and (2) ice-ocean interactions. To
provide a realistic context, our experiments are developed to simulate
the ocean circulation underneath the Pine Island ice shelf, and
validated against mooring observations and satellite derived meltrate
estimates. Each experiment is forced with data-informed open boundary
conditions that bear the imprint of the gyre in Pine Island Bay. We find
that even at a ~600 m grid resolution, flow aware ocean
parameterizations for subgrid-scale momentum and tracer transfer are
crucial for representing the circulation and meltrate pattern
accurately. Our simulations show that enhanced meltwater diffusion near
the ice-ocean interface intensifies near wall velocities via thermal
wind, which subsequently increases meltrates near the grounding line.
Incorporating a velocity dependent ice-ocean transfer coefficient
together with a flow aware ocean turbulence parameterization therefore
seems to be necessary for modelling the ocean circulation underneath ice
shelves in the Amundsen Sea at this resolution.