The Gulf Stream is a warm surface ocean current originating in the Gulf of Mexico, which widens to several hundred kilometres, and slows to less than 2 km/h, and then divides into several sub-currents, one of which is the North Atlantic Drift (Hayward and Williams (2005) Geol. Today 21, 4). The intensified westerlies in the northern North Atlantic and strengthened northerlies along the western part of the Nordic Seas force the North Atlantic Drift to follow a more easterly path, giving an asymmetric sea surface temperature response in the northern North Atlantic, and thereby maintaining the properties of the Atlantic Water entering the Nordic Seas (Otterå et al. (2004) Tellus A 56, 4). See Rasmussen and Thomsen (2004) Pal. Pal. & Pal. 210, 1 on the role of the North Atlantic Drift in millennial glacial climate fluctuations. Bryden et al. (2005) Nature 438 calculate that the North Atlantic Drift has slowed by 30% over the past 50 years.