Why are scientists interested in the Arctic's climate? They want to know what could happen to all that ice floating on the Arctic Ocean - a stiff blanket of frozen fresh water.
Fresh-water ice? Yep. As the seawater freezes, thaws, then refreezes, more and more salt is squeezed out of the ice. (That's why water made by melting chunks of "multi-year" ice makes such great-tasting hot chocolate!) It's also why the layer of seawater just beneath the ice is very, very salty.
If the Earth's climate continues to warm, scientists are concerned that growing amounts of the Arctic ice cap would melt each summer.
Researchers are not so much worried about rising sea levels if this happens. To illustrate why, fill a container part way with water, then add a dozen ice cubes. These represent the ice cap.
Mark the new water level, then see if it has changed after the ice has melted. No change? That's because the ice was already part of the "ocean."It's just that the top layer changed its form.
Fresh water is less dense than salt water, however, leading some researchers to think that it could form a "lid" as it enters the Atlantic Ocean, slowing salt water circulation and perhaps altering ocean currents and weather patterns worldwide.