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- Title
Early Wintertime CO<sub>2</sub> Uptake in the Western Arctic Ocean.
- Authors
Murata, A.; Inoue, J.; Nishino, S.; Yasunaka, S.
- Abstract
To investigate CO2 uptake in the western Arctic Ocean (north of 65°N), we conducted underway, ship‐based observations of the partial pressures of CO2 (pCO2) and total dissolved inorganic carbon (TCO2) in surface seawater in early winter (November 2018). From these two properties of the seawater inorganic carbon system, we calculated total alkalinity (TA). In the early winter, surface seawater pCO2 in most places was lower than atmospheric pCO2. The weighted mean of the air‐sea influxes of CO2 were calculated to be 7.5 ± 1.6 mmol m−2 d−1. The calculated influxes imply that the area acted as a moderate sink for atmospheric CO2 in early winter, and its rate of CO2 uptake was comparable to that (8.0 ± 1.7 mmol m−2 d−1) in summer (late August−September 2017). Spatial variations of surface seawater pCO2 in the early winter could be attributed mostly to conservative mixing changes of TCO2 and TA, which together accounted for more than 70% of the pCO2 variations. In the marginal ice zone, however, there was a decrease of surface seawater pCO2 by 70–90 μatm because of horizontal advection of water with an anomalously high temperature from the Pacific Ocean and its subsequent cooling. We concluded that mixing of water masses was as important as biological processes in causing spatial variations of pCO2 and CO2 uptake in the western Arctic Ocean, especially during seasons and in areas associated with little biological activity. Plain Language Summary: The characteristics of the Arctic Ocean are changing because of a reduction of sea ice caused by global warming. Carbon cycling may also change in response to global warming. To evaluate how much CO2 is currently being taken up by the ocean, we conducted ship‐based observations of atmospheric and surface seawater partial pressures of CO2 (pCO2) and related seawater properties on the Pacific side of the Arctic Ocean (north of 65°N) in early winter, when few such observations have been conducted because of the seasonal expansion of sea ice. In early winter (November 2018), surface seawater pCO2 was lower than atmospheric pCO2, except in the southern parts of the study area. The implication is that the area acted as a sink for atmospheric CO2. In early winter, when rates of biological processes were low because there was little sunlight, spatial variations of surface seawater pCO2 could be explained mostly by water mixing, except in areas near sea ice, where low water temperatures decreased the pCO2. We highlight the role of water mixing as a determinant of the potential of the ocean to act as a sink for CO2, especially during seasons and in areas associated with little biological activity. Key Points: Shelf waters in the western Arctic Ocean acted as a sink for atmospheric CO2 that was as large in November 2018 as in August–September 2017Cooling of Pacific‐origin water was the main cause of a 70–90 μatm decrease of surface seawater partial pressures of CO2 in the marginal ice zonePhysical processes such as water mass mixing and cooling were the main factors that controlled uptake of CO2 in early winter and summer
- Subjects
WINTER; OCEAN; SEA ice; WATER masses; ATMOSPHERIC carbon dioxide; PARTIAL pressure; GLOBAL warming
- Publication
Journal of Geophysical Research. Oceans, 2022, Vol 127, Issue 8, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2021JC018037