Simulation of the Atlantic meridional overturning circulation in an atmosphere-ocean global coupled model. Part II: weakening in a climate change experiment: a feedback mechanism |
| |
| Authors: | Virginie Guemas David Salas-Mélia |
| |
| Institution: | (1) Centre National de Recherches Météorologiques/Groupe d’Etude de l’Atmosphère Météorologique (CNRM/GMGEC), Météo-France, CNRS, 31057 Toulouse Cedex, France;(2) Laboratoire des Sciences du Climat et de l’Environnement, UMR 1572, CEA-CNRS-UVSQ, Gif-sur-Yvette, France |
| |
| Abstract: | Most state-of-the art global coupled models simulate a weakening of the Atlantic meridional overturning circulation (MOC)
in climate change scenarios but the mechanisms leading to this weakening are still being debated. The third version of the
CNRM (Centre National de Recherches Météorologiques) global atmosphere-ocean-sea ice coupled model (CNRM-CM3) was used to
conduct climate change experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4).
The analysis of the A1B scenario experiment shows that global warming leads to a slowdown of North Atlantic deep ocean convection
and thermohaline circulation south of Iceland. This slowdown is triggered by a freshening of the Arctic Ocean and an increase
in freshwater outflow through Fram Strait. Sea ice melting in the Barents Sea induces a local amplification of the surface
warming, which enhances the cyclonic atmospheric circulation around Spitzberg. This anti-clockwise circulation forces an increase
in Fram Strait outflow and a simultaneous increase in ocean transport of warm waters toward the Barents Sea, favouring further
sea ice melting and surface warming in the Barents Sea. Additionally, the retreat of sea ice allows more deep water formation
north of Iceland and the thermohaline circulation strengthens there. The transport of warm and saline waters toward the Barents
Sea is further enhanced, which constitutes a second positive feedback. |
| |
| Keywords: | Thermohaline circulation Deep ocean convection Global coupled model Coupled mechanism Climate change |
| 本文献已被 SpringerLink 等数据库收录！ |
|
