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Front. Earth Sci. | doi: 10.3389/feart.2018.00234

Carbon dynamics during the formation of sea ice at different growth rates

  • 1ETH Zürich, Switzerland
  • 2Institute of Ocean Sciences, Canada

Controlled laboratory experiments have shed new light on the potential importance of brine rejection during sea-ice formation for carbon dioxide sequestration in the ocean. We grew ice in an experimental seawater tank (1 m3) under abiotic conditions at three different air temperatures (-40 °C, -25 °C, -15 °C) to determine how different ice growth rates affect the allocation of carbon to ice, water, or air. Carbonate system parameters were determined by discrete sampling of ice cores and water, as well as continuous measurements by multiple sensors deployed mainly in the water phase. A budgetary approach revealed that of the initial total inorganic carbon (TIC) content of the water converted to ice, only 28-29 % was located in the ice phase by the end of the experiments run at the warmest temperature, whereas for the coldest ambient temperature, 46-47 % of the carbon remained in the ice. Exchange with air appeared to be negligible, with the majority of the TIC remaining in the under-ice water (53 -72 %). Along with a good correlation between salinity and TIC in the ice and water samples, these observations highlight the importance of brine drainage to TIC redistribution during ice formation. For experiments without mixing of the under-ice water, the sensor data further suggested stronger stratification, likely related to release of denser brine, and thus potentially larger carbon sequestration for ice grown at a colder temperature and faster growth rate.

Keywords: sea ice, growth rates, CO2 system, brine drainage, Tank experiment

Received: 27 Jul 2018; Accepted: 03 Dec 2018.

Edited by:

Jeff S. Bowman, Scripps Institution of Oceanography, University of California, San Diego, United States

Reviewed by:

Soren Rysgaard, Aarhus University, Denmark
Sebastien Moreau, Norwegian Polar Institute, Norway
Daiki Nomura, Graduate School of Fisheries Sciences, Hokkaido University, Japan  

Copyright: © 2018 König, Miller, Simpson and Vagle. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Ms. Daniela S. König, ETH Zürich, Zurich, Switzerland, daniela.koenig@liverpool.ac.uk