Thanks in part to the Gulf Stream, palm trees survive the winter in southwestern England, and the fjords of Norway never freeze. Here's how it works:
As the Gulf Stream flows northward, the surface water evaporates because of the temperature difference between the warm tropical water and the colder air over the North Atlantic. That increases the water's salinity and decreases its temperature, making it heavier.
At a critical point, the surface water becomes so salty and heavy that it starts to sink through the layers below — some scientists describe it as a lava lamp.
This happens in three places near the Arctic: the Labrador Sea, southwest of Greenland; the Norwegian Sea, east of the ice-capped island; and in parts of the Arctic Ocean. The cold and salty water sinks to the ocean floor and then flows back toward the equator in cold abyssal currents.
People are also reading…
The downward draft created when the water sinks at these locations, and a third spot in Antarctica, powers the system of currents known as the ocean conveyor belt.
One way to visualize the process is to imagine a bathtub divided in two halves. The left half is filled with freshwater and right half with sea water, which is heavier because it contains salt.
If two holes are drilled in the dividing panel — one on top and the other at the bottom — the lighter freshwater will flow to the right through the upper hole, while the heavier sea water will flow left through the bottom hole.
If the sea water on the right is diluted with freshwater, however, the difference in density between the two halves will decrease and the flow will become weaker.
Scientists fear the same thing would happen to the ocean conveyor if large amounts of freshwater are released in the north Atlantic as the Greenland ice sheet melts.
Find slide shows, photo galleries and more science news at azstarnet.com/science
