Weddell Sea is a globally significant contributor to deep-sea sequestration of natural carbon dioxide

A mechanism of lateral transport of remineralized carbon from the subsurface Weddell Sea into the abyssal world oceans is presented and its impact is quantified. In the Weddell Sea interior, full remineralization of the export production occurs at shallow depths. This shallow, CO2-charged water stands in isopycnal contact with the abyssal world ocean waters to the north of the subpolar Weddell Sea. Via isopycnal water transport, remineralized CO2 is transferred and sequestered in the deep sea. The amount involved is 1.9×1013 g C yr−1, which is equal to at least 6% of the presently estimated world-wide natural CO2 sequestration in the abyssal oceans. It thus constitutes an important component of the lower limb of the global oceanic carbon cycle. There may be more regions like the Weddell Sea, where this mechanism could be active. It is likely to play a significant role on the glacial–interglacial time scale. During a glacial period, reduced CO2 transport via the CIW would tend to increase the atmospheric partial pressure of CO2 as opposed to the generally decreasing pCO2 trend.