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Abstract

The deep oceans play a crucial role in regulating the Earth’s climate on long timescales by exchanging heat and chemical compounds with the atmosphere and moving them globally. However, our knowledge about deep circulation is in the initial stage. For instance, twenty years ago, in the Madagascar Basin, chlorofluorocarbons (CFCs) concentration in the Antarctic Bottom Water (AABW) layer was insignificant. But newer measurements in 2018 revealed an increased concentration of these chemical compounds, which counters our previous knowledge. A possible explanation is that deep currents, as we understood them, may have changed course and strength in the last twenty years. To begin solving this puzzle, we put together the 2019 DMB Experiment, a project funded by the US National Science Foundation and endorsed by the International Indian Ocean Expedition. The project aims to measure the deep currents in this region for the first time using shipboard instruments, RAFOS, and deep Argo floats. Combining the novel measurements with computer simulations, the study will identify the pathways that deep waters travel in the Madagascar Basin and examine what causes such circulation patterns. Due to COVID-19, our cruise has been on hold since 2020. After four years of waiting, we are sailing from South Africa to Mauritius in April-May this year. In this talk, we will present the first results of the fieldwork component of this project.