Biological pump Sensitivity and climate change, InterroGatiNg past environmentAL perturbations

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PI: Alexandre Pohl. This is a H2020 Marie Curie Global Fellowship (257 k€) that allowed me to spend 2 years in California Riverside to work with Andy Ridgwell, and one additional year back home at the Biogéosciences research lab in Dijon, France. The main idea was to simulate deep-time ocean oxygenation and its coupling with the evolution of the marine biosphere.

Collaborators:

Alexandre Pohl

Fellows:

Abstract

Oceans play a vital role in removing CO2 from the atmosphere through a mechanism involving algae known as the biological pump. Changing environmental conditions may affect this system and the oxygenation of oceans in ways we cannot at this time predict easily. BioSIGNAL project will use modelling of coupled oceanic ecosystems and geochemical cycles using past records of the biological pump’s reactions to change to understand the mechanics of the process. This will provide invaluable help to scientists and policymakers who are working on next-generation marine ecosystem models projecting the effect of climate change on ocean processes.

The biological pump refers to the mechanism by which carbon is assimilated by photosynthetic algae in the ocean photic zone and subsequently exported to depth upon death of the organisms. The largest part of this export production is generally remineralized as it travels throughout the water column where it depletes dissolved oxygen concentrations. A fraction of the export production may still reach the sea floor, where it is susceptible to be buried, thus inducing a net removal of CO2 from the ocean-atmosphere system. Therefore, the good appraisal of the response of the biological pump to changing environmental conditions is crucial to reasonably predict climate and ocean oxygenation impacts, both associated with past events and as will result from ongoing anthropogenic emissions. However, the behavior of the ecological system in the face of climatic changes and how it impacts the strength and efficiency of the biological pump remains difficult to predict. To address this, the BioSIGNAL project will investigate the sensitivity of the biological pump in a novel way – using a state-of-the-art ecological model including a representation of marine biogeochemical cycles. BioSIGNAL will focus on past periods, which provide a whole evolutionary chronicle to which model outputs can be directly compared. Confrontation of model results with geological records will also allow to develop a mechanistic understanding of the behavior of the ecological system in response to a wide range of environmental perturbations. The proposed approach constitutes an unrivaled opportunity to increase our understanding of the geological record and what it can tell us of relevance to the future. Lessons learned here, both positive and negative, have the potential to help inform the next generation of marine ecosystem models needed to make improved projections of future global change impacts on ocean ecosystems, and hence engaging a broad range of global change scientists and ultimately, policy makers.

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