It is occasionally said that Britain and Ireland owe their mild climate to the presence of the Gulf Stream and the North Atlantic Drift. Thus, the story goes, the Gulf Stream brings warm water from Florida up the eastern seaboard of the United States and then across the Atlantic in the North Atlantic Drift to the shores of Britain and Ireland, hence moderating the otherwise cold winters. Certainly, the surface temperature of the eastern North Atlantic is a few degrees warmer than the water at the same latitude off the coast of Newfoundland, as figure 2.2 in chapter 2 illustrates. Although this difference does have some effect on the temperature differences between the two locations, Britain and Ireland have a moderate winter climate primarily as a consequence of the fact that they are next to the ocean, with the ocean on their west. Even if there were no gyres in the ocean at all, the climate of these parts would be much more moderate than the climate at similar latitudes on the eastern sides of continental land masses. Thus, Britain and Ireland have a much more similar climate to British Columbia, at a similar latitude on the west coast of canada, than they do to Newfoundland and Labrador on the east coast. The effects of the east-west asymmetry of sea-surface temperatures on the seasonal climate of Britain and Ireland, and of midlatitude coastal areas surrounding the ocean basins generally, are relatively small.1
However, the effects of the ocean and the ocean circulation on the climate of Britain and Ireland are far from small. If the ocean were to cease circulating altogether— that is, both the gyres and the meridional overturning circulation were to cease—then the high latitudes would generally get colder, as we discussed in the previous section, and possibly freeze over. If the oceans did not freeze, western Europe would still have a maritime climate and a more moderate seasonal cycle than the eastern United States and eastern Canada.
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