Large contribution of the sea-ice zone to Southern Ocean carbon export revealed by BGC-Argo floats

Abstract

The Southern Ocean (south of 30°S) contributes significantly to global ocean carbon uptake through the solubility pump and phytoplankton productivity. Many studies have estimated carbon export to the deep ocean, but very few have attempted a basin-scale perspective. In this study, we use an extensive array of BGC-Argo floats to improve previous estimates of carbon export across basins and frontal zones, with a focus on the sea-ice zone (SIZ). We find that the SIZ contributes 33% of the 5.08 PgC y− 1 total Southern Ocean carbon export. We also show that subsurface carbon respiration, not flux out of the surface ocean, contributes most strongly to the temporal and spatial variability of carbon export. Our work highlights the importance of closely monitoring the SIZ to accurately quantify the total Southern Ocean carbon sink, especially as the SIZ is prone to strong interannual variability. Tightening these estimates and their drivers ultimately impacts our understanding of climate variability at the global ocean scale.