Is the Oceanic Heat Transport in the North Atlantic Irrelevant to the Climate in Europe?

It has long been believed that the transport of heat northward by the Atlantic Ocean circulation is of importance to mean/seasonal atmosphere-ocean climate, and with less certainty, to decadal climate variability. Indeed, ASOF is founded on the idea that oceanic freshwater and heat transports are both crucial to climate. The importance of ocean circulation has been challenged Clement and Cane (2002), hereinafter 'SBYGNCC', in their paper, 'Is the Gulf Stream responsible for Europe's mild winters?' While centering attention on the mild climate of Europe, their work, if correct would have greater consequences. Their argument is based on belief in following: that: (i) only a small portion of the total northward heat transport north of 40°N, is accomplished by the ocean in comparison with the atmospheric heat transport (ii) oceanic heat storage is local, with the summer's heating of the mixed layer being the dominant source of wintertime oceanic heat release to the atmosphere, with little contribution from oceanic heat transport (iii) freshwater transport coupled with heat transport can be neglected. Here we argue that while (i) is true it is misleading, (ii) is based on a simple logical fallacy in their paper, and is incorrect for much of the northern Atlantic, and by neglecting (iii) they have missed the most important climate interaction of all. One could hardly argue against the persuasive reasoning provided by SBYGNCC that the maritime climate maintains the temperature contrast between the North America and Europe. However, their conclusions regarding removal of the oceanic heat transport could be taken to mean that oceanic heat transport has no signifi cant consequence for the climate in Europe and elsewhere, beyond a minor warming of 0°C-3°C. We address points (i) to (iii) in order. (i): Satellite radiation measurements combined with atmospheric observations assimilated into models give estimates of total, atmospheric and oceanic meridional heat fl ux. Recent analyses elevate the atmospheric contribution somewhat, the atmospheric transport peaking between 4 and 5 PW (5x10 15 watt), while the ocean transport peaks at about 2 PW (Trenberth and Caron, 2001). However, as Bryden and Imawaki (2001) emphasize [using transport estimates of Keith (1995)], the atmospheric fl ux is comprised of nearly equal contributions from latent-and sensible heat. Latent heat is fresh water (2.5 PW