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Meridional Heat Transport in the DeepMIP Eocene ensemble: non-CO2 and CO2 effects
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  • Fanni Dora Kelemen,
  • Sebastian Steinig,
  • Agatha Margaretha De Boer,
  • Jiang Zhu,
  • Wing-Le Chan,
  • Igor Niezgodzki,
  • David Hutchinson,
  • Gregor Knorr,
  • Ayako Abe-Ouchi,
  • Bodo Ahrens
Fanni Dora Kelemen
Goethe University Frankfurt

Corresponding Author:[email protected]

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Sebastian Steinig
University of Bristol
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Agatha Margaretha De Boer
Stockholm University
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Jiang Zhu
National Center for Atmospheric Research
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Wing-Le Chan
University of Tokyo
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Igor Niezgodzki
Institute of Geological Sciences PAN
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David Hutchinson
University of New South Wales
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Gregor Knorr
AWI Bremerhaven
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Ayako Abe-Ouchi
University of Tokyo
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Bodo Ahrens
IAU, Goethe University Frankfurt am Main
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Abstract

The total meridional heat transport (MHT) is relatively stable across different climates. Nevertheless, the strength of individual processes contributing to the total transport are not stable. Here we investigate the MHT and its main components especially in the atmosphere, in five coupled climate model simulations from the Deep-Time Model Intercomparison Project (DeepMIP). These simulations target the Early Eocene Climatic Optimum (EECO), a geological time period with high CO2 concentrations, analogous to the upper range of end-of-century CO2 projections. Preindustrial and early Eocene simulations at a range of CO2 levels (1x, 3x and 6x preindustrial values) are used to quantify the MHT changes in response to both CO2 and non-CO2 related forcings. We found that atmospheric poleward heat transport increases with CO2, while the effect of non-CO2 boundary conditions (e.g., paleogeography, land ice, vegetation) is causing more poleward atmospheric heat transport on the Northern and less on the Southern Hemisphere. The changes in paleogeography increase the heat transport via transient eddies at the mid-latitudes in the Eocene. The Hadley cells have an asymmetric response to both the CO2 and non-CO2 constraints. The poleward latent heat transport of monsoon systems increases with rising CO2 concentrations, but this effect is offset by the Eocene topography. Our results show that the changes in the monsoon systems’ latent heat transport is a robust feature of CO2 warming, which is in line with the currently observed precipitation increase of present day monsoon systems.