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Ocean model formulation influences transient climate response
- Source :
- EPIC3Journal of Geophysical Research-Oceans, Wiley, 126(12), pp. e2021JC017633, ISSN: 0148-0227, Journal of Geophysical Research: Oceans
- Publication Year :
- 2021
- Publisher :
- Wiley, 2021.
-
Abstract
- The transient climate response (TCR) is 20% higher in the Alfred Wegener Institute Climate Model (AWI‐CM) compared to the Max Planck Institute Earth System Model (MPI‐ESM) whereas the equilibrium climate sensitivity (ECS) is by up to 10% higher in AWI‐CM. These results are largely independent of the two considered model resolutions for each model. The two coupled CMIP6 models share the same atmosphere‐land component ECHAM6.3 developed at the Max Planck Institute for Meteorology (MPI‐M). However, ECHAM6.3 is coupled to two different ocean models, namely the MPIOM sea ice‐ocean model developed at MPI‐M and the FESOM sea ice‐ocean model developed at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). A reason for the different TCR is related to ocean heat uptake in response to greenhouse gas forcing. Specifically, AWI‐CM simulations show stronger surface heating than MPI‐ESM simulations while the latter accumulate more heat in the deeper ocean. The vertically integrated ocean heat content is increasing slower in AWI‐CM model configurations compared to MPI‐ESM model configurations in the high latitudes. Weaker vertical mixing in AWI‐CM model configurations compared to MPI‐ESM model configurations seems to be key for these differences. The strongest difference in vertical ocean mixing occurs inside the Weddell and Ross Gyres and the northern North Atlantic. Over the North Atlantic, these differences materialize in a lack of a warming hole in AWI‐CM model configurations and the presence of a warming hole in MPI‐ESM model configurations. All these differences occur largely independent of the considered model resolutions.<br />Plain Language Summary: The transient climate response (TCR) describes how strongly near‐surface temperatures warm in response to gradually increasing greenhouse‐gas levels. Here we investigate the role of the ocean which takes up heat and thereby delays the surface warming. Two models of the Coupled Model Intercomparison Project Phase 6 (CMIP6), the Alfred Wegener Institute Climate Model (AWI‐CM) and the Max Planck Institute Earth System Model (MPI‐ESM), which use the same atmosphere model but different ocean models are selected for this study. In AWI‐CM the upper ocean layers heat faster than in MPI‐ESM, while the opposite is true for the deep ocean. As a consequence, the TCR is 20% stronger in AWI‐CM compared to MPI‐ESM. We find that weaker vertical ocean mixing in AWI‐CM compared to MPI‐ESM, especially over the northern North Atlantic and the Weddell and Ross Gyres, is key for these differences. Our findings corroborate the importance of realistic ocean mixing in climate models when it comes to getting the strength and timing of climate change right.<br />Key Points: The transient climate response in two coupled models with the same atmosphere but different ocean components differs by 20%. The upper (deeper) ocean heats faster (slower) in AWI‐CM compared to MPI‐ESM, independent of model resolution. Vertical mixing in the northern North Atlantic and the Weddell and Ross Gyres appears to be key for these differences.<br />Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347<br />German Climate Computing Centre (DKRZ)<br />Federal Ministry of Education and Research of Germany<br />Helmholtz Association http://dx.doi.org/10.13039/501100009318<br />https://esgf-data.dkrz.de/projects/cmip6-dkrz/
- Subjects :
- 010504 meteorology & atmospheric sciences
010505 oceanography
Oceanography
Atmospheric sciences
01 natural sciences
Vertical mixing
Geophysics
ddc:551.6
Space and Planetary Science
Geochemistry and Petrology
13. Climate action
Earth and Planetary Sciences (miscellaneous)
Environmental science
Transient (oscillation)
14. Life underwater
Climate response
0105 earth and related environmental sciences
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- EPIC3Journal of Geophysical Research-Oceans, Wiley, 126(12), pp. e2021JC017633, ISSN: 0148-0227, Journal of Geophysical Research: Oceans
- Accession number :
- edsair.doi.dedup.....88bc513dc05f5b2bf35bbae62ac23faf