Inorganic carbon system dynamics in landfast Arctic sea ice during the early-melt period

• Main Authors: Brown, Kristina A., Miller, Lisa L.M., Mundy, Christopher John, Papakyriakou, Tim, Roger, Francois, Gosselin, Michel, Carnat, Gauthier, Swystun, Kyle, Tortell, Philippe P.D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: Sciences de l'espace; Phénomènes atmosphériques; Géographie physique; Sciences de la terre et du cosmos; Arctic Ocean; brines; carbon cycling; CO 2; sea ice; stable isotopes; Arctic; Canadian Arctic Archipelago; Arctic Archipelago; Sea ice
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/217327; https://dipot.ulb.ac.be/dspace/bitstream/2013/217327/3/217327.pdf

We present the results of a 6 week time series of carbonate system and stable isotope measurements investigating the effects of sea ice on air-sea CO 2 exchange during the early melt period in the Canadian Arctic Archipelago. Our observations revealed significant changes in sea ice and sackhole brine carbonate system parameters that were associated with increasing temperatures and the buildup of chlorophyll a in bottom ice. The warming sea-ice column could be separated into distinct geochemical zones where biotic and abiotic processes exerted different influences on inorganic carbon and pCO 2 distributions. In the bottom ice, biological carbon uptake maintained undersaturated pCO 2 conditions throughout the time series, while pCO 2 was supersaturated in the upper ice. Low CO 2 permeability of the sea ice matrix and snow cover effectively impeded CO 2 efflux to the atmosphere, despite a strong pCO 2 gradient. Throughout the middle of the ice column, brine pCO 2 decreased significantly with time and was tightly controlled by solubility, as sea ice temperature and in situ melt dilution increased. Once the influence of melt dilution was accounted for, both CaCO 3 dissolution and seawater mixing were found to contribute alkalinity and dissolved inorganic carbon to brines, with the CaCO 3 contribution driving brine pCO 2 to values lower than predicted from melt-water dilution alone. This field study reveals a dynamic carbon system within the rapidly warming sea ice, prior to snow melt. We suggest that the early spring period drives the ice column toward pCO 2 undersaturation, contributing to a weak atmospheric CO 2 sink as the melt period advances. Key Points: As spring Arctic sea ice matures, carbon dioxide undersaturation develops Abiotic processes dominated inorganic carbon in upper ice and early in season Biotic processes controlled inorganic carbon in bottom ice and late in season SCOPUS: ar.j FLWIN SCOPUS: ar.j info:eu-repo/semantics/published