Preprints
https://doi.org/10.5194/tc-2022-136
https://doi.org/10.5194/tc-2022-136
 
08 Jul 2022
08 Jul 2022
Status: this preprint is currently under review for the journal TC.

Impact of icebergs on the seasonal submarine melt of Sermeq Kujalleq

Karita Kajanto1, Fiammetta Straneo2,3, and Kerim Nisancioglu1 Karita Kajanto et al.
  • 1Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
  • 2Scripps Institution of Oceanography, UCSD, CA, USA
  • 3Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway

Abstract. The role of icebergs in narrow fjords hosting marine terminating glaciers in Greenland is poorly understood, even though icebergs provide a substantial freshwater flux that can exceed the subglacial discharge. Iceberg melt is distributed at depth, contributing to fjord stratification, thus impacting melt and dynamics of the glacier front. We model the high-silled Ilulissat Icefjord in Western Greenland with the MITgcm ocean model, using the IceBerg package to study the effect of icebergs on fjord properties, and compare our results with available observations from 2014. We find the subglacial discharge plume to be the primary driver of the seasonality of circulation, glacier melt and iceberg melt. Icebergs are necessary to include to correctly understand the properties of Ilulissat Icefjord, since they modify the fjord in three main ways: First, icebergs cool and freshen the water column within their vertical extent; Second, icebergs depress the neutral buoyancy depth of the plume and the outflow route of glacially modified water; Third, icebergs modify the deep basin, below their vertical extent, due to both increased entrainment of glacially modified water into the fjord, and iceberg modification of the incoming ambient water. Furthermore, the depressed neutral buoyancy depth of the plume limits melt to the deep section of the front of Sermeq Kujalleq (Jakobshavn Isbræ) even during peak summer, and thus promotes undercutting. We postulate that the impact of icebergs on the neutral buoyancy depth of the plume is a key mechanism connecting iceberg melange and glacier calving, independent of mechanical support.

Karita Kajanto et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-136', Anonymous Referee #1, 25 Jul 2022
  • RC2: 'Comment on tc-2022-136', Anonymous Referee #2, 03 Aug 2022

Karita Kajanto et al.

Karita Kajanto et al.

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Short summary
Many outlet glaciers in Greenland are connected to the ocean by narrow glacial fjords, where warm water melts the glacier underneath. Ocean water is modified in these fjords through processes that are poorly understood, particularly iceberg melt. We use a model to show how the icebergs cool down Ilulissat Icefjord, and cause circulation to take place deeper in the fjord, than if there were no icebergs. This causes the glacier to melt from a smaller surface area than without icebergs.