The Icelandic Whirlpool
Note the low pressure system that sits on top of Iceland. This “Icelandic Low” helps bring moisture to northern Europe and Scandinavia. (Modified from: NOAA)
Low Pressure in Iceland and Rain in Norway
On its way north, the Gulf Stream transports some 100 million cubic meters of water per second. To put this in perspective, one million cubic meters per second (equal to one "sverdrup," after the Norwegian oceanographer Harald U. Sverdrup and abbreviated sv) is a five times greater flow than that carried by the Amazon (the largest river in the world) at flood stage. (See the glossary section on “general circulation of the ocean”).
This tremendous flow of warm water toward Iceland does two things.
First, it brings large amounts of heat which are available through redistribution by latent heat flux: the release of moisture (as rain) that warms the air (The town of Bergen, Norway is famous for its rain. In Oslo they tell this joke: A tourist asked a child in Bergen, “Does the rain here ever stop.” He answers, “ I don't know, I’m only 8 years old.”) Second, the warm water sets up a low pressure region around Iceland, reaching over into the Norwegian Sea. This helps accelerate the westerly winds, which drive the North Atlantic Currents, and it sheds storm systems that move downwind into Norway, Sweden, Scotland, the Netherlands, Denmark and northern Germany.
Satellite data of sea surface temperature
from April 18, 2001. Notice the temperature anomaly off Norway and how, between 60°N and 80°N, the waters off Norway’s coast are as much as 8°C warmer than waters at the same latitude of Greenland, the Hudson Bay, and Alaska. (From: IRI/LDEO Climate Data Library
Formation of an Iceland Whirlpool
The Icelandic Low acts as an enormous whirlpool sucking in warm air from the subtropical regions on top of the Gulf Stream and sending much of the heat to Norwegian shores. The transport of heat by the warm ocean currents and the warm moist winds associated with them is what allows strawberries to grow in Norway. The counter-clockwise movement of this great whirlpool centered on Iceland stabilizes the regional circulation, helping to pull in warm water and warm winds that bring the energy that powers the whirlpool. Such a system may be called "self-stabilizing." It produces one of the greatest temperature anomalies known for the surface of the ocean, the uncommonly warm waters off Norway. Such a large anomaly suggests that the system is somehow "out of equilibrium" in this region. In turn, being out of equilibrium means that any substantial change in conditions (like those that could come about by climate change) is likely to result in a return toward equilibrium, that is, a colder Norwegian Sea, and a colder Norway.