Abstract

Global warming is causing a decrease in the amount of dissolved oxygen (o2) in the ocean, which is a major issue for marine ecosystem and sea life. However, we face challenges in accurately predicting these changes in o2 levels using our current models. In this presentation, I will talk about the uncertainties and missing pieces in our ocean biogeochemistry simulations. Specifically, I will look at the latest models that simulates how the o2 and temperature have changed over the past 50 years. I will closely look at o2 and heat in the top 700 meters of the ocean, using models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). I will compare changes in o2 levels and ocean heat content (OHC) to show how the ocean’s physical and biogeochemical response to climate change differ. These comparisons use forced ocean-only models (from the Ocean Model Intercomparison Project phases 1 and 2, or OMIP1 and OMIP2 ) and coupled climate models (from CMIP6 ’s historical simulations). The models show different trends in o2 and OHC over the past five decades. A closer look at the OMIP1 and OMIP2 models suggests that different atmospheric forcing such as surface wind could explain why these models simulate different changes. Furthermore, comparing OMIP models with CMIP6 historical models reveals that differences in the background mean state of the models, due to how they were initially set up and spun-up, lead to significant differences in how they simulate o2 levels will change due to climate change. Finally, I will discuss how future studies could improve our understanding of ocean deoxygenation and biogeochemistry changes by using coordinated simulation efforts. This could help us figure out what controls changes in o2 levels and other related aspects of the ocean biogeochemical cycles.