Air-sea fluxes of greenhouse gases and oxygen in the northern Benguela Current region during upwelling events

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Morgan , E J , Lavric , J V , Arevalo-Martinez , D L , Bange , H W , Steinhoff , T , Seifert , T & Heimann , M 2019 , ' Air-sea fluxes of greenhouse gases and oxygen in the northern Benguela Current region during upwelling events ' , Biogeosciences , vol. 16 , no. 20 , pp. 4065-4084 . https://doi.org/10.5194/bg-16-4065-2019

Title: Air-sea fluxes of greenhouse gases and oxygen in the northern Benguela Current region during upwelling events
Author: Morgan, Eric J.; Lavric, Jost V.; Arevalo-Martinez, Damian L.; Bange, Hermann W.; Steinhoff, Tobias; Seifert, Thomas; Heimann, Martin
Other contributor: University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
Date: 2019-10-21
Language: eng
Number of pages: 20
Belongs to series: Biogeosciences
ISSN: 1726-4170
DOI: https://doi.org/10.5194/bg-16-4065-2019
URI: http://hdl.handle.net/10138/311023
Abstract: Ground-based atmospheric observations of CO2, delta(O-2/N-2), N2O, and CH4 were used to make estimates of the air-sea fluxes of these species from the Luderitz and Walvis Bay upwelling cells in the northern Benguela region, during upwelling events. Average flux densities (+/- 1 sigma) were 0:65 +/- 0:4 mu mol m(-2) s(-1) for CO2, -5.1 +/- 2:5 mu mol m(-2) s(-1) for O-2 (as APO), 0:61 +/- 0:5 nmol m(-2) s(-1) for N2O, and 4:8 +/- 6:3 nmol m(-2)s(-1) for CH4. A comparison of our top-down (i.e., inferred from atmospheric anomalies) flux estimates with shipboard-based measurements showed that the two approaches agreed within +/- 55% on average, though the degree of agreement varied by species and was best for CO2. Since the top-down method overestimated the flux density relative to the shipboard-based approach for all species, we also present flux density estimates that have been tuned to best match the shipboard fluxes. During the study, upwelling events were sources of CO2, N2O, and CH4 to the atmosphere. N2O fluxes were fairly low, in accordance with previous work suggesting that the evasion of this gas from the Benguela is smaller than for other eastern boundary upwelling systems (EBUS). Conversely, CH4 release was quite high for the marine environment, a result that supports studies that indicated a large sedimentary source of CH4 in the Walvis Bay area. These results demonstrate the suitability of atmospheric time series for characterizing the temporal variability of upwelling events and their influence on the overall marine greenhouse gas (GHG) emissions from the northern Benguela region.
Subject: NITROUS-OXIDE EMISSIONS
ATMOSPHERIC OXYGEN
DIFFUSION-COEFFICIENTS
METHANE EMISSIONS
SATELLITE DATA
CO2 FLUXES
WIND-SPEED
N2O
VARIABILITY
WATER
1171 Geosciences
1172 Environmental sciences
1181 Ecology, evolutionary biology
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