Preprints
https://doi.org/10.5194/cp-2021-112
https://doi.org/10.5194/cp-2021-112

  30 Aug 2021

30 Aug 2021

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

Oceanic CO2 outgassing triggered by terrestrial organic carbon fluxes during deglacial flooding

Thomas Extier, Katharina D. Six, Bo Liu, Hanna Paulsen, and Tatiana Ilyina Thomas Extier et al.
  • Max Planck Institute for Meteorology, Hamburg, Germany

Abstract. Oceans play a major role on the exchange of carbon with the atmosphere and thereby on past climates with glacial/interglacial variations of the CO2 concentration. The melting of ice sheets during deglaciations lets the sea level rise which leads to the flooding of coastal land areas resulting in the transfer of terrestrial organic matter to the ocean. However, the consequences of such fluxes on the ocean biogeochemical cycle and uptake/release of CO2 are poorly constrained. Moreover, this potentially important exchange of carbon at the land-sea interface is not represented in most Earth System Models. We present here the implementation of terrestrial organic matter fluxes into the ocean at the transiently changing land-sea interface in the Max Planck Institute for Meteorology Earth System Model (MPI-ESM) and investigate their effect on the biogeochemistry during the last deglaciation. Our results show that during the deglaciation, most of the terrestrial organic matter inputs to the ocean occurs during Meltwater Pulse 1a (between 15–14 ka) which leads to additional 21.2 GtC of terrestrial origin (mostly originating from wood and humus). Although this additional organic matter input is relatively small in comparison to the global ocean inventory (0.06 %) and thus doesn’t have an impact on the global CO2 flux, the terrestrial organic matter fluxes initiate oceanic outgassing at regional hotspots like in Indonesia for a few hundred years. Finally, sensitivity experiments highlight that terrestrial organic matter fluxes are the drivers of oceanic outgassing in flooded coastal regions during Meltwater Pulse 1a. Furthermore, the magnitude of outgassing is rather insensitive to higher carbon to nutrients ratios of the terrestrial organic matter. Our results provide a first estimate of the importance of terrestrial organic matter fluxes in a transient deglaciation simulation. Moreover, our model development is an important step towards a fully coupled carbon cycle in an Earth System Model applicable for simulations of glacial/interglacial cycles.

Thomas Extier et al.

Status: open (until 25 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on cp-2021-112', Martin Koelling, 03 Sep 2021 reply
    • AC1: 'Reply on CC1', Thomas Extier, 10 Sep 2021 reply
  • RC1: 'Comment on cp-2021-112', Anonymous Referee #1, 20 Sep 2021 reply
  • RC2: 'Comment on cp-2021-112', Anonymous Referee #2, 22 Sep 2021 reply

Thomas Extier et al.

Thomas Extier et al.

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Short summary
The role of land-sea fluxes during deglacial flooding on the ocean biogeochemistry and CO2 change remains poorly constrained due to the lack of climate models that consider such fluxes. We implement the terrestrial organic matter fluxes into the ocean at transiently changing land-sea interface in MPI-ESM and investigate their effect during the last deglaciation. Most of the terrestrial carbon goes to the ocean during flooding events of Meltwater Pulse 1a, which leads to regional CO2 outgassing.