EGU23-16435, updated on 26 Feb 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Currents, mélange and iceberg calving in Greenland fjords: new insights to a self-organised critical system 

Poul Christoffersen1,2, Seungbong Lee2, Samuel Cook3, and Martin Truffer4
Poul Christoffersen et al.
  • 1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia (
  • 2Scott Polar Research Institute, University of Cambridge, Cambridge, UK (
  • 3Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland (
  • 4Geophysical Institute, University of Alaska, Fairbanks, USA (

Flow and mass balance of the Greenland Ice Sheet are largely controlled by marine-terminating glaciers that deliver large quantities of ice into fjords and coastal seas. The interaction of these glaciers with the ocean is crucial because heat and circulation in fjords drive high rates of melting. However, the links between warm ambient fjord water, subaqueous melting and iceberg calving are poorly understood. Here, we report a detailed record of surface circulation in Ikerasak Fjord, West Greenland, by tracking the displacements of icebergs in radar imagery acquired with a terrestrial radar interferometer, which also produced a detailed record of iceberg calving from Store Glacier. With images captured every three minutes, we derived fjord circulation and calving rates with unusually high temporal resolution. In the first of three periods, we observed low-speed surface currents (<0.15 m/s) together with high calving activity (around 50 events per hour) as a response to the break-up of proglacial winter melange. We subsequently observed faster surface currents (up to 0.57 m/s) but much less calving (<20 icebergs per hour). Later, as currents intensified and a large eddy formed, we observed a combination of fast fjord circulation (around 0.4 m/s) and high calving activity (20-40 events per hour). The record shows that calving is a self-organised critical system, with small icebergs produced continuously in a critical state, whereas large icebergs were produced mostly when calving becomes super-critical. A super-critical state was reached when the melange broke up and later as the eddy formed in front of the glacier. In this state, we found stronger fjord circulation to drive more frequent calving events, while more frequent calving in general caused a higher flux of ice to the ocean.

How to cite: Christoffersen, P., Lee, S., Cook, S., and Truffer, M.: Currents, mélange and iceberg calving in Greenland fjords: new insights to a self-organised critical system , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16435,, 2023.