Linking Overturning, Recirculation, and Melt in Glacial Fjords

Abstract

Fjord circulation modulates the connection between marine-terminating glaciers and the ocean currents offshore. These fjords exhibit both overturning and horizontal recirculations, which are driven by water mass transformation at the head of the fjord via subglacial discharge plumes and distributed meltwater plumes. However, little is known about how various fjord characteristics influence the interaction between 3D fjord circulation and glacial melt. In this study, high-resolution numerical simulations of idealized glacial fjords demonstrate that recirculation strength controls melt, which feeds back on overturning and recirculation. The relationships between overturning, recirculation, and melt rate are well predicted by vorticity balance, reduced-order melt parameterizations, and empirical scaling arguments. These theories allow us to take into account the near-glacier horizontal velocities, which yield improved predictions of fjord overturning, recirculation, and glacial melt.