RAPID-WATCH builds on RAPID to deliver a decade-long (2004-2014) time series of observations of the Atlantic Meridional Overturning Circulation (MOC). The observations is used with data from other sources to
- determine and interpret recent changes in the Atlantic MOC,
- assess the risk of rapid climate change due to changes in the MOC, and
- investigate the potential for predicting the MOC and its impacts on climate.
This work is carried out in collaboration with the Hadley Centre in the UK, and through international partnerships.
MOC data from 26°N are now available for 7 full years from 2004. For the first five years there seemed to be little variation from year to year once the seasonal cycle was taken into account. But the winter 2009-10 saw a severe drop in the strength of the MOC. This event coincided with a very cold winter in Europe, and has created much scientific interest. Now a paper from the 26N team reveals what took place.
The decline was not only due to anomalous winds in the winter of 2009-10, but also the result of the geostrophic (mid-ocean) flow increasing. Southward flow in the top 1100m intensified, and the deep southward return transport from high latitudes weakened. This rebalancing of the transport from the deep overturning to the upper gyre has implications for the heat transported by the Atlantic.