Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO2 Fluxes

Ribas-Ribas, Mariana; Battaglia, Gianna; Humphreys, Matthew P.; Wurl, Oliver

doi:10.3390/geosciences9050230

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Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO₂ Fluxes

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Center for Marine Sensors, Institute for Chemistry and Biology of the Marine Environment, Carl von Ossietzky University Oldenburg, 26129 Wilhelmshaven, Germany

Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland

Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK

Author to whom correspondence should be addressed.

Geosciences 2019, 9(5), 230; https://doi.org/10.3390/geosciences9050230

Received: 15 March 2019 / Revised: 6 May 2019 / Accepted: 13 May 2019 / Published: 20 May 2019

(This article belongs to the Special Issue Ocean-Atmosphere Interaction)

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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 (ΔpCO₂) 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 ΔpCO₂ between the ocean and atmosphere. Such conditions occur frequently in the Tropics. View Full-Text

Keywords: gas transfer velocity; low wind speed; carbon dioxide; ocean-atmosphere CO₂ flux; carbon cycle

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Ribas-Ribas, M.; Battaglia, G.; Humphreys, M.P.; Wurl, O. Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO₂ Fluxes. Geosciences 2019, 9, 230. https://doi.org/10.3390/geosciences9050230

AMA Style

Ribas-Ribas M, Battaglia G, Humphreys MP, Wurl O. Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO₂ Fluxes. Geosciences. 2019; 9(5):230. https://doi.org/10.3390/geosciences9050230

Chicago/Turabian Style

Ribas-Ribas, Mariana, Gianna Battaglia, Matthew P. Humphreys, and Oliver Wurl. 2019. "Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO₂ Fluxes" Geosciences 9, no. 5: 230. https://doi.org/10.3390/geosciences9050230

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Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO₂ Fluxes

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