The role of subinertial waves in ocean heat transport into four East Greenland fjords

Abstract

Fjords are the primary conduit for oceanic heat transport to the Greenland Ice Sheet. This heat transport is highly time-variable, with typical frequencies in the subinertial range (with periods of several days). We studied four fjords along the southeast coast of Greenland to determine what drives oceanic heat into these fjords. The four fjords cover a range of widths and lengths, and three different high-resolution model simulations provided a range in stratifications and surface forcings. We find that the heat transport is associated with resonant modes of internal subinertial waves. The variability in transport of deep warm (Atlantic) water is highly correlated to the principal component that is associated with the gravest vertical normal mode (EOF 1 in narrow fjords, EOF 3 in a wide fjord). The dominant frequency in the heat transport time series is thus determined by the shape of the fjord and the stratification, the latter through the wave speed of the gravest normal mode. The oceanic heat supply to the Greenland Ice Sheet is thus governed by variables that are relatively easy to measure observationally.