Arvind Singh
Arvind Singh is an Associate Professor at the Physical Research Laboratory (PRL), Ahmedabad, India. Before joining PRL, he was a Nippon Foundation - Partnership for Observations of the Global Ocean (POGO) Scholar at the Bermuda Institute of Ocean Sciences, Bermuda, and a postdoctoral fellow at the University of Gothenburg, Sweden, and GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany. His research focuses on biogeochemical cycles of carbon and nitrogen, as well as the application of stable isotopes in the marine environment, with a particular emphasis on the Indian Ocean. He is an Editor for JGR-Oceans and serves on the Diversity, Equity, Inclusion, and Accessibility (DEIA) committee of the American Geophysical Union (AGU). At PRL, he teaches graduate courses on ocean biogeochemistry and error analysis. Additionally, he frequently delivers introductory oceanography lectures to master's students and participants of the Earth Science Olympiad in India.
Glacial expansion of deoxygenation in the Arabian Sea
Ongoing anthropogenically-forced warming has reduced oceanic oxygen levels, raising
concerns about the expansion of Oxygen Deficient Zones (ODZs) and their effects on marine habitats. The Arabian Sea, a perennial ODZ, experiences extremely low oxygen levels at intermediate depths, enhancing anaerobic processes like denitrification and ammonium oxidation (anammox), resulting in a loss of bioavailable nitrogen and the production of nitrous oxide. Mechanisms of how climate warming influences ODZ variability remain uncertain due to limited observations. Therefore, understanding long-term variations of ODZs under substantial climatic forcing and boundary conditions through geological history is essential. We present reconstructions of dissolved oxygen levels across the past glacial-interglacial cycle by analyzing iodine to calcium (I/Ca) ratios in planktic foraminifera from two sediment cores: one from the northern Arabian Sea (38–6 ka), colocated within the core of the modern ODZ, and the other from its flank, from the southeastern Arabian Sea (45–6 ka). We find that an expanded ODZ persisted in the Arabian Sea, extending into its southern portion during the Last Glacial Maximum (LGM), likely driven by enhanced primary productivity due to intense winter mixing. Cooler ocean temperatures were insufficient to buffer this expansion of oxygen deficient waters. Instead, we suggest that monsoonal dynamics, transport of intermediate waters from the Southern Ocean, and their impact on regional marine production control glacial-to-present ODZ variability in the Arabian Sea.
