The water temperatures of the Atlantic are very apparent in this colour enhanced photograph.
The temperature of the surface waters in the Atlantic Ocean is governed by the flow of sea-surface currents. Worldwide, the waters around the equator are warmest. As a result, currents moving away from the equator bring warm water to both the north and south Atlantic coasts. The North Equatorial Current moves warm water to the North Atlantic, while the South Equatorial Current spreads both north and south, bringing warm water to the east coasts of both North and South America. In the North Atlantic, the strong Labrador Current spreads a cold stream as far down as latitude 40ºN. By contrast, the Gulf Stream brings warm water as far up as the coast of Norway. The junction where these two extreme temperatures meet - around the Grand Banks of Newfoundland - is striking, and is known as the “cold wall.”
In deeper waters, the North Atlantic temperatures can vary from about 2.5°C at the very bottom to about 5°C at 3 000 feet. The immense tides of the Bay of Fundy continually stir the cold deep water up to the surface of the North Atlantic, making the surface waters cool, even in midsummer. The summer sun does succeed in warming the surface inshore waters of the Atlantic, often to a maximum of 15-20°C. In the winter, however, the temperatures of these same coastal waters drop to just above freezing. The North Atlantic deepwater currents bring cold water to the south, lowering deep water temperatures in the South Atlantic by about 2°C.