Global emergence of compound climatic impact-drivers reveals a high exposure of marine environment
Zhetao Tan (Institute of Atmospheric Physics, Chinese academic of sciences & Mercator ocean international, Toulouse, France)
Séminaire du LMD à l’ENS.
Changes in health and sustainability of the ocean that provide goods and services for human well-being are closely linked to climate change. However, the ocean is exposed to a range of climatic impact-drivers (CIDs, e.g., temperature increase, sea level rise, oxygen depletion, acidification etc.) from global to local scale concurrently. These multiple CIDs make the ocean environment shifting from the normal condition, posing either positive or detrimental effects to ocean ecosystems. Therefore, detecting and understanding the combined effect of different CIDs (named compound CIDs in this study) is critical to further unravel diverse and adverse impacts on the ocean ecosystems.
In this study, we analyzed compound CIDs from changes in the upper 1000m of the ocean temperature (T), salinity (S), dissolved oxygen (DO) from 1960 to 2022, as well as surface pH changes from 1985 to 2021 by using several observation-based gridded products.
We first used a time of emergence (ToE) approach to study the emergence of compound CIDs over the past 60 years, with associated uncertainty evaluation. We found that a large fraction of global ocean has been under the emergence of compound CIDs before 2021 in the surface, epipelagic zone and mesopelagic zone: not only from surface to subsurface, from global to local, but also from temperature to dissolved oxygen, from single emergence to triple emergence (i.e., concurrent change). Then, we developed and implemented an exposure approach by using several exposure metrices in relevant for marine ecosystems. We found that the global emergence of compound CIDs reveals a high exposure of marine environment in some regions (e.g., Atlantic upwelling zone, oxygen minimum zone, subtropical gyre of Atlantic, Mediterranean Sea etc.). Finally, we identified these key areas of compound concurrent change as ocean hot spots to the long-term change of compound CIDs and linked it to some regional marine ecosystem case studies from other literatures.
As marine ecosystems rely on an environment determined by multiple drivers, the investigation of the compound CIDs provides a more complete description (and quantification) of their long-term exposure to the CIDs (multiple stressors) applied to other open questions and to support the open adaptation and mitigation.
Lundi 27 mars à 11h en salle Claude Froidevaux – 314 de l’ENS (24 rue Lhomond, Paris 5ème)