Calving Signature in Ocean Waves at Helheim Glacier and Sermilik Fjord, East Greenland

Abstract

hen glaciers calve icebergs, a fraction of the released potential energy is radiated away via gravity waves. The characteristics of such waves, caused by iceberg calving on Helheim Glacier in east Greenland, are investigated. Observations were collected from an array of five high-frequency bottom pressure meters placed along Sermilik Fjord. Calving-generated tsunami waves were identified and used to construct a calving event catalog. Calving events are observed to cluster around high and low semidiurnal tides and around high and prior-to-low semimonthly tides. In the postcalving ocean state, discrete spectral peaks associated with calving events are observed, and they are consistent among all the events. A numerical model is used to compute the resonant modes of the fjord and to simulate calving-generated ocean waves. Damped oscillator boundary forcing with 5- to 10-min periods is found to reproduce well the observed properties of calving waves. These observations and modeling are relevant for better understanding of wave dynamics in glacier fjords.