03 Jun 2021

03 Jun 2021

Review status: this preprint is currently under review for the journal BG.

Climate pathways behind phytoplankton-induced atmospheric warming

Rémy Asselot1, Frank Lunkeit2, Philip B. Holden3, and Inga Hense1 Rémy Asselot et al.
  • 1Institute for Marine Ecosystem and Fishery Science, Center for Earth System Research and Sustainability, University of Hamburg, Hamburg, Germany
  • 2Meteorological Institute, University of Hamburg, Hamburg, Germany
  • 3Environment, Earth and Ecosystems, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK

Abstract. We investigate in which ways marine biologically-mediated heating increases the surface atmospheric temperature. While the effects of phytoplankton light absorption on the ocean have gained attention over the past years, the impact of this biogeophysical mechanism on the atmosphere is still unclear. Phytoplankton light absorption warms the surface of the ocean with consequences for the air-sea heat exchange and CO2 flux. We focus on the ocean-atmosphere interface and study the importance of air-sea heat exchange versus air-sea CO2 flux. To shed light on the role of phytoplankton light absorption on the surface atmospheric temperature, we performed different simulations with the EcoGENIE Earth system model. We configure the model without a seasonal cycle and, if not stated otherwise, the atmospheric CO2 concentration is allowed to evolve freely. The climate pathways examined are: heat exchange, dissolved CO2, solubility of CO2, and sea-ice covered area. Overall we show that the air-sea CO2 exchange has a larger effect on the biologically-induced atmospheric warming than the air-sea heat flux. Moreover, we notice that the freely evolving solubility of CO2 has a cooling effect on the surface atmospheric temperature.

Rémy Asselot et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-118', Anonymous Referee #1, 13 Jun 2021
  • RC2: 'Comment on bg-2021-118', David Armstrong McKay, 27 Aug 2021
  • RC3: 'Comment on bg-2021-118', Alexandre Pohl, 02 Sep 2021

Rémy Asselot et al.

Model code and software

Source code for Asselot et al, 2021 - Biogeosciences Rémy Asselot

Rémy Asselot et al.


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Short summary
Previous studies show that phytoplankton light absorption can warm the atmosphere via an increase in air-sea heat exchange and CO2 flux. Which of this flux is the main driver in the phytoplankton-induced atmospheric warming is still unknown. To shed light on this research question, we conduct simulations with a climate model of intermediate complexity. We show that phytoplankton mainly warms the atmosphere by increasing the air-sea CO2 flux.