A detailed view on the seasonality of stable carbon isotopes across the North Atlantic.

Becker, Meike, Steinhoff, Tobias and Körtzinger, Arne (2018) A detailed view on the seasonality of stable carbon isotopes across the North Atlantic. Open Access Global Biogeochemical Cycles, 32 (9). pp. 1406-1419. DOI 10.1029/2018GB005905.

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Abstract

The North Atlantic Ocean plays a major role in climate change not the least due to its importance in CO2 uptake and thus natural carbon sequestration. The CO2 concentration in its surface waters, which determines the ocean's CO2 sink/source function, varies on seasonal and interannual timescales and is mainly driven by air‐sea gas exchange, temperature variability and biological production/respiration. The variability in stable carbon isotope signatures can provide further insight and help to improve the understanding of the controls of the surface ocean carbon system.

In this work, a cavity ringdown spectrometer was coupled to a classical, equilibrator‐based pCO2 system on a VOS line that regularly sails across the subpolar North Atlantic between North America and Europe. From 2012 to 2014, a 3‐year time series of underway surface δ13C(CO2) data was obtained along with continuous measurements of temperature, salinity and fCO2. We perform a decomposition of thermal and non‐thermal drivers of fCO2 and δ13C(CO2). The direct measurement of the surface ocean δ13C(CO2) allows us to estimate the mass flux and also the stable carbon isotope fractionation during air‐sea gas exchange. While the CO2 mass flow was in the range of 1 − 2 mol CO2 m−2 yr−1 on the shelves and 2.5 − 3.5 mol CO2 m−2 yr−1 in the open ocean, the isotope signature of this CO2 flux with respect to the sea surface ranged from −2.6 ± 1.4‰ on the shelves to −6.6 ± 0.9‰ in the western and −4.5 ± 0.9‰ in the eastern part of the open ocean section.

Document Type: Article
Keywords: Stable carbon isotopes; Air‐sea gas exchange; Cavity ringdown spectroscopy; North Atlantic Ocean; Carbon dioxide; Seasonal variability;
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence > FO-R07
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2018GB005905
ISSN: 0886-6236
Projects: CARBOCHANGE, ICOS, Future Ocean
Date Deposited: 26 Sep 2018 08:03
Last Modified: 27 May 2019 09:39
URI: http://oceanrep.geomar.de/id/eprint/44388

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