Winter weather controls net influx of atmospheric CO2 on the northwest European shelf

Shelf seas play an important role in the global carbon cycle, absorbing atmospheric carbon dioxide (CO2) and exporting carbon (C) to the open ocean and sediments. The magnitude of these processes is poorly constrained, because observations are typically interpolated over multiple years. Here, we used 298500 observations of CO2 fugacity (fCO(2)) from a single year (2015), to estimate the net influx of atmospheric CO2 as 26.2 +/- 4.7 Tg C yr(-1) over the open NW European shelf. CO2 influx from the atmosphere was dominated by influx during winter as a consequence of high winds, despite a smaller, thermally-driven, air-sea fCO(2) gradient compared to the larger, biologically-driven summer gradient. In order to understand this climate regulation service, we constructed a carbon-budget supplemented by data from the literature, where the NW European shelf is treated as a box with carbon entering and leaving the box. This budget showed that net C-burial was a small sink of 1.3 +/- 3.1 Tg C yr(-1), while CO2 efflux from estuaries to the atmosphere, removed the majority of river C-inputs. In contrast, the input from the Baltic Sea likely contributes to net export via the continental shelf pump and advection (34.4 +/- 6.0 Tg C yr(-1)).

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Kitidis Vassilis, Shutler Jamie D., Ashton Ian, Warren Mark, Brown Ian, Findlay Helen, Hartman Sue E., Sanders Richard, Humphreys Matthew, Kivimae Caroline, Greenwood Naomi, Hull Tom, Pearce David, McGrath Triona, Stewart Brian M., Walsham Pamela, McGovern Evin, Bozec Yann, Gac Jean-Philippe, Van Heuven Steven M. A. C., Hoppema Mario, Schuster Ute, Johannessen Truls, Omar Abdirahman, Lauvset Siv K., Skjelvan Ingunn, Olsen Are, Steinhoff Tobias, Koertzinger Arne, Becker Meike, Lefevre Nathalie, Diverres Denis, Gkritzalis Thanos, Cattrijsse Andre, Petersen Wilhelm, Voynova Yoana G., Chapron Bertrand, Grouazel Antoine, Land Peter E., Sharples Jonathan, Nightingale Philip D. (2019). Winter weather controls net influx of atmospheric CO2 on the northwest European shelf. Scientific Reports. 9 (20153). 11p..,

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