Column-Compound Extremes in the Global Ocean

• Main Authors: Wong, Joel, Münnich, Matthias, Gruber, Nicolas
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2023
• Subjects: Pacific; Ocean acidification
• Online Access: http://dx.doi.org/10.22541/essoar.169755245.55770848/v1

Marine extreme events such as marine heatwaves, ocean acidity extremes and low oxygen extremes can pose a substantial threat to marine organisms and ecosystems. Such extremes might be particularly detrimental (i) when they occur compounded in more than one stressor, and (ii) when the extremes extend substantially across the water column, restricting the habitable space for marine organisms. Here, we use daily output from a hindcast simulation (1961-2020) from the ocean component of the Community Earth System Model (CESM) to characterise such column-compound extreme events (CCX), employing a relative threshold approach to identify the extremes and requiring them to extend vertically over at least 50m. The diagnosed CCXs are prevalent, occupying worldwide in the 1960s about 1% of the volume contained within the top 300m. Over the duration of our simulation, CCXs become more intense, last longer, and occupy more volume, driven by the trends in ocean warming and ocean acidification. For example, the triple CCX have expanded 24-fold, now last 3-times longer, and have become 6-times more intense since the early 1960s. Removing this effect with a moving baseline permits us to better understand the key characteristics of the CCXs. They last typically about 10 to 30 days and predominantly occur in the tropics and the high latitudes, regions of high potential biological vulnerability. Overall, the CCXs fall into 16 clusters, reflecting different patterns and drivers. Triple CCX are largely confined to the tropics and the North Pacific, and tend to be associated with the El Nino-Southern Oscillation.