Impact of nonzero intercept gas transfer velocity parameterizations on global and regional ocean–atmosphere CO2 fluxes

Ribas-Ribas, Mariana, Battaglia, Gianna, Humphreys, Matthew P. and Wurl, Oliver (2019) Impact of nonzero intercept gas transfer velocity parameterizations on global and regional ocean–atmosphere CO2 fluxes. Geosciences, 9 (5). ISSN 2076-3263

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Abstract

Carbon dioxide (CO2) fluxes between the ocean and atmosphere (FCO2) are commonly computed from differences between their partial pressures of CO2 (∆pCO2) and the gas transfer velocity (k). Commonly used wind-based parameterizations for k imply a zero intercept, although in situ field data below 4 m s−1 are scarce. Considering a global average wind speed over the ocean of 6.6 m s−1, a nonzero intercept might have a significant impact on global FCO2. Here, we present a database of 245 in situ measurements of k obtained with the floating chamber technique (Sniffle), 190 of which have wind speeds lower than 4 m s−1. A quadratic parameterization with wind speed and a nonzero intercept resulted in the best fit for k. We further tested FCO2 calculated with a different parameterization with a complementary pCO2 observation-based product. Furthermore, we ran a simulation in a well-tested ocean model of intermediate complexity to test the implications of different gas transfer velocity parameterizations for the natural carbon cycle. The global ocean observation-based analysis suggests that ignoring a nonzero intercept results in an ocean-sink increase of 0.73 Gt C yr−1. This corresponds to a 28% higher uptake of CO2 compared with the flux calculated from a parameterization with a nonzero intercept. The differences in FCO2 were higher in the case of low wind conditions and large ∆pCO2 between the ocean and atmosphere. Such conditions occur frequently in the Tropics.

Item Type: Article
Uncontrolled Keywords: carbon cycle,carbon dioxide,gas transfer velocity,low wind speed,ocean-atmosphere co flux,earth and planetary sciences(all) ,/dk/atira/pure/subjectarea/asjc/1900
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Depositing User: LivePure Connector
Date Deposited: 05 Jul 2019 10:30
Last Modified: 22 Apr 2020 08:00
URI: https://ueaeprints.uea.ac.uk/id/eprint/71638
DOI: 10.3390/geosciences9050230

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