Tropical and Extratropical Responses of the North Atlantic Atmospheric Circulation to a Sustained Weakening of the MOC

David J. Brayshaw, Tim Woollings, Michael Vellinga
2009 Journal of Climate  
The tropospheric response to a forced shutdown of the North Atlantic ocean's meridional overturning circulation (MOC) is investigated in a coupled oceanatmosphere GCM (HadCM3). The strength of the boreal winter North Atlantic storm track is significantly increased and penetrates much further into Western Europe. The changes in the storm track are shown to be consistent with the changes in near-surface baroclinicity which can be linked to changes in surface temperature gradients near regions of
more » ... ts near regions of sea-ice formation and in the open ocean. Changes in the SST of the tropical Atlantic are linked to a strengthening of the subtropical jet to the north which, combined with the enhanced storm track, leads to a pronounced split in the jet structure over Europe. EOF analysis and stationary box indices methods are used to analyse changes to the North Atlantic Oscillation (NAO). There is no consistent signal of a change in the variability of the NAO, and while the changes in the mean flow project onto the positive NAO phase they are significantly different from it. However, there is a clear eastward shift of the NAO pattern in the shutdown run, and this potentially has implications for ocean circulation and for the interpretation of proxy paleoclimate records.
doi:10.1175/2008jcli2594.1 fatcat:ywktzpixt5exlgv4nywibjxeja