Glacier calving rates due to subglacial discharge, fjord circulation, and free convection
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Tidewater glacier calving provides the most direct mechanism of ice transfer from land to the ocean. However, the physical melt processes influencing calving remain challenging to constrain. In this study we focus on calving rates at Kongsbreen, a tidewater glacier in Svalbard, due to three mechanisms of submarine melt: 1) free convection, 2) horizontal fjord circulation, and 3) meltwater discharge. To calculate an overall calving rate, we measure glacier velocity and terminus change using Sentinel imagery. We calculate free convection, fjord circulation, and meltwater discharge calving using mooring data for mid-fjord ocean temperature (30-80 m depth), reanalysis results for meltwater runoff, and georectified time-lapse imagery to track icebergs and infer surface circulation. Results show the total glacier calving rate is highly correlated with ocean temperature during the 2016 melt season. When runoff was present, we found that subglacial discharge accounted for calving rates an order of magnitude greater than the maximum calving rates assigned to the other two melting mechanisms combined. Further, subglacial discharge at Kongsbreen was more efficient in inducing calving later in the season than earlier in the season, implying that the increase in ocean temperatures, the timing of meltwater discharge within a melt season, and/or the development of discrete meltwater exit channels are critical components to calving rates. As the recent atmospheric warming trend and subsequent increase in meltwater discharge is expected to continue, it is essential to understand the processes contributing to an increase in glacier calving and incorporate these processes into predictive models.
Schild , K M , Renshaw , C E , Benn , D I , Luckman , A , Hawley , R L , How , P , Trusel , L , Cottier , F R , Pramanik , A & Hulton , N R J 2018 , ' Glacier calving rates due to subglacial discharge, fjord circulation, and free convection ' , Journal of Geophysical Research - Earth Surface , vol. Early View . https://doi.org/10.1029/2017JF004520
Journal of Geophysical Research - Earth Surface
©2018. The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
DescriptionWe would like to thank the New Hampshire Space Grant Consortium (award # NNX15AH79H) for the training grant to fund KMS; the ConocoPhillips-Ludin Northern Area Program (under the CRIOS project) and the Dartmouth Graduate Studies Travel fund for their financial support to conduct fieldwork and travel for data dissemination; the Polar Geospatial Center for arranging access to the WorldView-2 imagery; the UK Natural Environmental Research Council (NERK) Oceans 2025 and Northern Sea Program for mooring work support, with further support from the Research Council of Norway (NFR) projects: Circa (214271), Cleopatra (178766), Cleopatra II (216537), and Marine Night (226471); Alex Hart and the GeoSciences Mechanical Workshop at the University of Edinburgh for manufacturing the time-lapse camera enclosure that was used in this study; Colin Oriffiths for overseeing the collection of mooring data in Kongsfjorden since 2002; ESA for processing the Copernicus Sentinel data (2016).
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