While threshold behavior for the AMOC has been readily observed in simple climate models, Hawkins et al. reproduce the dynamic in a much more complex atmosphere-ocean coupled general circulation model (AOGCM) for the first time. Re-creating more than 56,000 years of ocean activity in the Fast Met Office/Universities Simulator (FAMOUS) AOGCM, the authors find that by progressively adding freshwater into the North Atlantic they are able to trigger the transition from a healthy functioning AMOC to a nonexistent one, which does not recover when the freshwater addition is subsequently decreased. Further, on the basis of the FAMOUS simulations and recent observations, the authors suggest that measurements of the direction of the net flux of freshwater at the southern edge of the Atlantic could serve as indicators that the AMOC actually has two stable states and thus has the potential to exhibit a threshold transition.
Geophysical Research Letters, doi: 10.1029/2011GL047208, 2011
Title: Bistability of the Atlantic overturning circulation in a global climate model and links to ocean freshwater transport
Authors: E. Hawkins, R. S. Smith, L. C. Allison and T. J. Woollings: NCAS-Climate, University of Reading, Reading, UK;
J. M. Gregory: NCAS-Climate, University of Reading, Reading, UK; and Met Office, Exeter, UK;
H. Pohlmann: Met Office, Exeter, UK;
B. de Cuevas: National Oceanography Centre, Southampton, UK.
4. Formation of Indonesian Archipelago destroyed Australian rainforests
Just over 3 million years ago, a climatic upheaval forever changed Australia's western coast. Over the span of 200,000 years the southward flowing waters of the Leeuwin Current cooled by 2 t
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