Determining CO2 Balance influenced by Upwelling and Primary Production in the Equatorial Pacific Region at 180° using CO2 and O2 flux

Abstract

The oceanic carbon cycle is one of the most important mechanisms in controlling the Earth’s climate as oceans take up to 30% of the carbon emissions, acting as a major sink. The ocean’s biological and solubility pumps are responsible for carbon storage through air-sea interactions. However, a big source of carbon to the atmosphere is the Equatorial Pacific due to it being a region of upwelling where old carbon-rich waters from the deep sea are transported to the surface. This paper highlights the finding of the research conducted upon the RV Thompson from 2nd to 8th March, 2023 in the Equatorial Pacific along the 5°N to 5°S transect during the tail end of a La Niña event. In order to quantify the air-sea flux and the proportion of carbon balance affected by upwelling and primary production in this region, a 1-D carbon budget model in steady state was applied to the CO2 and O2 distributions between 2°N and 2°S at the dateline (180°). Gas transfer velocity and solubility coefficients were used to quantify the outgassing of CO2 and to understand the correlation strength of these factors. Using the model, 96% of the flux of CO2 is affected by upwelling and less than 4% is affected by primary production. The average FCO2 = 0.0120 mol m-2 day-1 from 2°N to 2°S due to the proximity to the equator but the highest flux out of the system was 0.0227 mol m-2 day-1, recorded at 3°N with gas transfer velocity of CO2 ~27 cm/hr at a wind speed of 11 m/s, after which the wind speeds became relatively constant proceeding 2°N. This indicated that even though biochemical factors play a dominant role in regulating air-sea flux, physical factors such as wind are quite important as well.