The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) contribution to CMIP6: investigation of sea-level and ocean climate change in response to CO<sub>2</sub> forcing
The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) aims to investigate the spread in simulations of sea-level and ocean climate change in response to CO<sub>2</sub> forcing by atmosphere–ocean general circulation models (AOGCMs). It is particularly motivated by the uncerta...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://www.geosci-model-dev.net/9/3993/2016/gmd-9-3993-2016.pdf |
| Summary: | The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) aims to
investigate the spread in simulations of sea-level and ocean climate change
in response to CO<sub>2</sub> forcing by atmosphere–ocean general circulation
models (AOGCMs). It is particularly motivated by the uncertainties in
projections of ocean heat uptake, global-mean sea-level rise due to thermal
expansion and the geographical patterns of sea-level change due to ocean
density and circulation change. FAFMIP has three tier-1 experiments, in which
prescribed surface flux perturbations of momentum, heat and freshwater
respectively are applied to the ocean in separate AOGCM simulations. All
other conditions are as in the pre-industrial control. The prescribed fields
are typical of pattern and magnitude of changes in these fluxes projected by
AOGCMs for doubled CO<sub>2</sub> concentration. Five groups have tested the
experimental design with existing AOGCMs. Their results show diversity in the
pattern and magnitude of changes, with some common qualitative features. Heat
and water flux perturbation cause the dipole in sea-level change in the North
Atlantic, while momentum and heat flux perturbation cause the gradient across
the Antarctic Circumpolar Current. The Atlantic meridional overturning
circulation (AMOC) declines in response to the heat flux perturbation, and
there is a strong positive feedback on this effect due to the consequent
cooling of sea-surface temperature in the North Atlantic, which enhances the
local heat input to the ocean. The momentum and water flux perturbations do
not substantially affect the AMOC. Heat is taken up largely as a passive
tracer in the Southern Ocean, which is the region of greatest heat input,
while the weakening of the AMOC causes redistribution of heat towards lower
latitudes. Future analysis of these and other phenomena with the wider range
of CMIP6 FAFMIP AOGCMs will benefit from new diagnostics of temperature and
salinity tendencies, which will enable investigation of the model spread in
behaviour in terms of physical processes as formulated in the models. |
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| ISSN: | 1991-959X 1991-9603 |