Column-Compound Extremes in the Global Ocean

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 (a) when they are compounded in more than one stressor, and (b) when the extremes extend substantially across the water column, restricting the habitable space for marine organisms. Here, we use daily output of a hindcast simulation (1961-2020) from the ocean component of the Community Earth System Model to characterize such column-compound extreme events (CCX), employing a relative threshold approach to identify extremes and requiring them to extend vertically over at least 50 m. The diagnosed CCX are prevalent, occupying worldwide in the 1960s about 1% of the volume contained within the top 300 m. Over the duration of our simulation, CCX become more intense, last longer, and occupy more volume, driven by the trends in ocean warming and ocean acidification. For example, the triple CCX expanded 39-fold, now last 3-times longer, and became 6-times more intense since the early 1960s. Removing this effect with a moving baseline permits us to better understand the key characteristics of CCX, revealing a typical duration of 10-30 days and a predominant occurrence in the Tropics and high latitudes, regions of high potential biological vulnerability. Overall, the CCX 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 Ni & ntilde;o-Southern Oscillation. The global ocean is becoming warmer, more acidic, and losing oxygen due to climate change. On top of this trend, sudden increases in temperature, or drops in pH or oxygen adversely affect marine organisms when they cannot quickly adapt to these extreme conditions. These conditions are worse for marine organisms when such extremes occur together in the vertical water column, leading to column-compound extreme (CCX) events, severely reducing the available habitable space. To investigate such CCX, we used a numerical model simulation of the global ocean during the historical period of 1961-2020. Singular extreme events are identified primarily with relative percentile thresholds, while CCX require a 50 m minimum depth threshold in the water column. We find that CCX have been increasing in volume, occupying up to 20% of the global ocean volume toward 2020. We then remove the climate trend to better understand the drivers behind CCX. Many CCX occur in the tropics and high latitudes, lasting 10-30 days and reducing habitable space by up to 75%. This study is the first to systematically detect compound extremes in the water column and may form the basis for determining their detrimental effects on marine organisms and ecosystems. Column-compound extremes (CCX)- extremes in multiple parameters within the top 300 m-may reduce habitable space by up to 75% From 1961 to 2020, CCX have become more intense, longer, and occupy more volume, driven by the trends in ocean warming and acidification Triple CCX are confined to the tropics and the North Pacific and tend to be associated with ENSO

Keyword(s)

compound extreme events, marine heatwave, ocean acidity extreme, low oxygen extreme, global, vertical water column

Full Text

FilePagesSizeAccess
Publisher's official version
338 Mo
Supporting Information S1
3492 Mo
Movie S1
-2 Mo
Original Version of Manuscript
417 Mo
Peer Review History
14168 Ko
Author Response to Peer Review Comments
25275 Ko
First Revision of Manuscript
5713 Mo
Second Revision of Manuscript [Accepted]
5713 Mo
How to cite
Wong Joel, Munnich Matthias, Gruber Nicolas (2024). Column-Compound Extremes in the Global Ocean. Agu Advances. 5 (3). e2023AV001059 (33p.). https://doi.org/10.1029/2023AV001059, https://archimer.ifremer.fr/doc/00941/105249/

Copy this text