Gas dynamics within landfast sea ice of an Arctic fjord (NE Greenland) during the spring–summer transition
Author:
Geilfus Nicolas-Xavier12, Delille Bruno3, Tison Jean-Louis4, Lemes Marcos1, Rysgaard Søren156
Affiliation:
1. 1Centre for Earth Observation Science and Department of Environment and Geography, University of Manitoba, Winnipeg, MB, Canada 2. 2Current address: Tvärminne Zoological Station, University of Helsinki, Hanko, Finland 3. 3Chemical Oceanography Unit, University of Liège, Liège, Belgium 4. 4Laboratoire de Glaciologie, DGES-IGEOS, Université Libre de Bruxelles, Bruxelles, Belgium 5. 5Greenland Climate Research Centre, Greenland Institute of Natural Resources, Nuuk, Greenland 6. 6Arctic Research Centre, Aarhus University, Aarhus, Denmark
Abstract
Sea ice is an active component of the Earth’s climate system, interacting with both the atmosphere and the ocean. Arctic sea ice is commonly covered by melt ponds during late spring and summer, strongly affecting sea ice physical and optical properties. How melt pond formation affects sea ice gas dynamics and exchanges between sea ice and the atmosphere, with potential feedbacks on climate, is not well known. Here we measured concentrations of N2, O2, and Ar, total alkalinity, and dissolved inorganic carbon within sea ice of Young Sound, NE Greenland, to examine how melt pond formation and meltwater drainage through the ice affect its physical properties and gas composition, including impacts on CO2 exchange with the atmosphere. Sea ice gas composition was controlled mainly by physical processes, with most of the gas initially in gaseous form in the upper ice layer. A minor contribution from biological processes was associated with positive estimates of net community production (up to 2.6 µmol Lice−1 d−1), indicating that the ice was net autotrophic. As the sea ice warmed, the upper ice gas concentrations decreased, suggesting a release of gas bubbles to the atmosphere. However, as melt ponds formed, the ice surface became strongly depleted in gases. Due to melt pond development, meltwater permeated through the ice, resulting in the formation of an underwater ice layer also depleted in gases. Sea ice, including brine, slush, and melt ponds, was undersaturated in CO2 compared to the atmosphere, supporting an uptake of up to −4.26 mmol m−2 d−1 of atmospheric CO2. As melt pond formation progressed, however, this uptake weakened in the strongly altered remaining ice surface (the “white ice”), averaging −0.04 mmol m−2 d−1. This study reveals the importance of melt pond formation and dynamics for sea ice gas composition.
Publisher
University of California Press
Subject
Atmospheric Science,Geology,Geotechnical Engineering and Engineering Geology,Ecology,Environmental Engineering,Oceanography
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