"It is widely believed by scientists and laypeople alike that the transport
of warm water north in the Gulf Stream and North Atlantic Drift, and its
release to the atmosphere, is the reason why western Europe's winters are so
much milder (about 15-20°C) than those of eastern North America... This idea
seems to have gained wide currency with the subtle difference that the
poleward flow of warm water is now more likely to be ascribed to the
thermohaline circulation than the Gulf Stream per se. It remains a central
organizing principle of climate research."

and concludes:

"In the current paper we demonstrate that transport of heat by the ocean is
not responsible for the contrast between Europe's mild winters and the harsh
ones of eastern North America. Indeed, this contrast would occur if the
ocean was a motionless slab of modest and uniform depth. Instead the
contrast arises as a consequence of atmospheric advection around the
Icelandic Low and the simple maritime-continental climate distinction."
http://abob.libs.uga.edu/bobk/ccc/cc042402.html
[also check out story: WHAT WATSON DID WRONG]