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Strong biological carbon uptake and carbonate chemistry associated with dense shelf water outflows in the Cape Darnley polynya, East Antarctica

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Title: Strong biological carbon uptake and carbonate chemistry associated with dense shelf water outflows in the Cape Darnley polynya, East Antarctica
Authors: Kan, Murakami Browse this author
Daiki, Nomura Browse this author →KAKEN DB
Gen, Hashida Browse this author →KAKEN DB
Nakaoka, Shin-ichiro Browse this author
Kitade, Yujiro Browse this author →KAKEN DB
Hirano, Daisuke Browse this author
Hirawake, Toru Browse this author →KAKEN DB
Ohshima, Kay I. Browse this author →KAKEN DB
Keywords: Carbon dioxide
Primary production
Carbon transport
Dense water formation
Gas exchange
Cape Darnley
Southern Ocean
Issue Date: 10-Sep-2020
Publisher: Elsevier
Journal Title: Marine Chemistry
Volume: 225
Start Page: 103842
Publisher DOI: 10.1016/j.marchem.2020.103842
Abstract: Formation of dense shelf water (DSW) in coastal polynyas (open water or thin sea-ice cover) in the sea-ice zone around Antarctica supplies Antarctic Bottom Water (AABW) through overflow down the continental slope. In coastal polynyas, atmospheric carbon dioxide (CO2) is absorbed by the ocean in the early spring because of active primary production, and DSW formation is an important process for transporting this carbon from the sea surface to the deep ocean. However, there have been few quantitative evaluations of carbon consumption by active primary production and transport in coastal polynyas. Here, we examined the carbon dynamics in the Cape Darnley polynya (CDP), East Antarctica during austral summer 2009, by using carbonate system parameters combined with oceanographic mooring data. The partial pressure of CO2 in the CDP surface water was lower than that of the atmosphere and the mean and standard deviation of sea−air CO2 flux was estimated as −6.5 ± 6.9 mmol C m−2 d−1 (a negative value indicates absorption of atmospheric CO2 by the ocean). Vertical profiles of dissolved inorganic carbon (DIC) concentration showed that concentrations in the bottom layer near the ocean floor were lower (by about 20 μmol kg−1) than those in the ambient water (e.g., modified Circumpolar Deep Water, mCDW). The low-DIC in the shelf water was maintained by the strong biological uptake of carbon imported from high-DIC mCDW within the water column. Therefore, low-DIC DSW overflowed down the continental slope, and low-DIC concentrations were maintained through an export pathway to the continental shelf. The annual production of dissolved organic carbon and particulate organic carbon on the shelf was estimated as 0.7 × 1011–1.5 × 1011 mol C using the data for the DIC of DSW and current velocity data from a mooring in the CDP. Our results provide quantitative estimates for the potential role of carbon consumption by the active primary production and carbon transport by dense water formation in Antarctic coastal polynyas.
Rights: © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Type: article (author version)
Appears in Collections:国際連携研究教育局 : GI-CoRE (Global Institution for Collaborative Research and Education : GI-CoRE) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
北方生物圏フィールド科学センター (Field Science Center for Northern Biosphere) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 野村 大樹

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