The oxygen dissolved in the ocean is crucial for sustaining most marine life and plays a key role in many biogeochemical cycles. However, human-induced global temperature rise and nutrient runoff from land are causing a significant decline in oxygen levels in marine settings. Ocean’s oxygen has also declined in the past, when so-called “deoxygenation events” have perturbed the ocean carbon cycle, leading to the deposition of organic-rich layers both in marginal seas (sapropels events) and open ocean (oceanic anoxic events) settings.
The drivers behind marine deoxygenation are complex, involving diverse biogeochemical processes operating over different timescales. Understanding these dynamics is crucial for predicting current and future oxygen trends and developing effective mitigation and adaptation strategies. The geological archive presents a unique opportunity to study past deoxygenation on a broad spectrum of timescales, offering insights into the intricate feedback mechanisms and biogeochemical dynamics that control ocean oxygen levels.
This session aims to bring together contributions that address ocean deoxygenation and the consequent formation of organic-rich sediments from the Paleozoic to the present, based on paleoceanographic and paleoclimatic proxy-based reconstructions and numerical modeling. The session aims at emphasizing: (1) Novel proxy developments in organic, inorganic, and isotope geochemistry; (2) Advancements in fossil and mineral indicators of past deoxygenation events; (3) Innovative modeling approaches and model-data integration to quantify and resolve the mechanisms driving ocean deoxygenation across different timescales. We encourage contributions focusing on laminated sediments, which can provide high-resolution glimpses into the timing and progression of marine deoxygenation. By broadening our perspective on the mechanisms and timescales of ocean deoxygenation, this session aims to deliver key, quantitative information on the oxygen dynamics in the past oceans that will contribute to projections of future ocean oxygen levels in a warming world.