Four months ago I restarted writing blog entries. I switched from stories about my old life as a professional snowboarder to my new life as a young researcher. My aim was to use blog entries to communicate science in an informal and possibly fun way and to facilitate my personal scientific writing process. However, I ended up doing a lot of scientific writing and close to no blogging over the past months. The result is my master’s thesis on „Ocean oxygen extreme events in the Eastern Tropical Pacific“ and here I’m sharing the abstract of my thesis with you. In the unlikely event that you feel like reading more about my work, please contact me and I’m happy to send you my full thesis.
Abstract
Extreme events on land are known to affect the structure of ecosystems and alter their biogeochemical activity extensively. However, our understanding of the role of extreme events in the marine domain is limited, especially for events associated with extremely low oxygen concentrations. In a warming climate, deoxygenation is predicted to increase, and thus oxygen extremes will very likely become more frequent and intense in the future. A region of particular interest is the Eastern Tropical Pacific (ETP) which harbors the largest naturally occurring subsurface oxygen minimum zone (OMZ) in the global ocean. The OMZ in the ETP, which is situated under highly productive surface waters, is strongly affected by seasonal variability and superimposed interannual dynamics induced by El Niño-Southern Oscillation (ENSO). Even though OMZs and deoxygenation are well studied, and drivers for oxygen variability are understood, the event perspective on oxygen extremes is mostly missing. Our key motivation is to start closing this gap and translate the terminology of extreme events into the oxygen world. In this thesis, we apply a model-based approach to study oxygen extreme events. We analyze a hindcast model run from 1979–2016 generated by the Regional Oceanic Modeling System (ROMS) and embedded ecosystem component (BEC) in a setup configured to the ETP. We detect and characterize oxygen extreme events by their frequency, duration, intensity, severity, and spatial extent. We present that seasonal cycles affect oxygen concentrations at the upper OMZ boundary in the Eastern Tropical North Pacific (ETNP), accounting for more than one-third of the simulated variability. On interannual timescales, we found that ENSO strongly modulates the vertical position of the oxycline. ENSO explains 30 %–40 % of the oxygen variability in the ETP. Ultimately, we relate the impact of ENSO on oxygen concentrations with changes in extreme event characteristics. For the first time, we present this important step towards establishing the event perspective on oxygen extremes. We show that El Niño leads to more frequent but shorter events, while La Niña triggers longer, more persistent events. However, the link from ENSO as a crucial driver for interannual oxygen variability onto the extreme event perspective remains complex.
That’s it! Up next: my internship at MIT in Boston.