The first people known to reach the North Pole were Americans Robert Peary and Matthew Henson, and the Inuits Ootah, Ooqueah, Seegloo and Egingwah. They arrived at the pole on April 16, 1909, after traveling 400 miles from Greenland over sea ice.

In the not-too-distant future, however, it might not be possible to make such a journey. Why? Because the sea ice that once covered most of the Arctic Ocean year-round is rapidly disappearing.

The total area covered by sea ice last year was the lowest ever recorded. It was less than one-half of the average ice cover in the 1950s and 1960s. The decline in recent years has been even more dramatic. Since 2005, the area covered by sea ice has dropped by 25 percent. This is equivalent to losing an area of sea ice the size of Texas and California combined.

What is causing the ice to melt? The short answer is that summer temperatures in the Arctic are rising faster than anywhere else on Earth. The warming of the Arctic Ocean not only means that more ice is melting every summer, but also, because the water has to cool down more before it freezes, less ice is forming every winter. This combination of effects has led some scientists to speculate that the Arctic Ocean could be free of summer ice in as few as 20 or 30 years.

How would the loss of the ice cap affect things? On the plus side, it would allow ships to sail across the top of the world, at least in summer, making for a much shorter trip between Russia and North America.

Other impacts would be more troublesome. Sea ice reflects more of the sun's heat back into space than does open water. Thus, the melting of the ice could accelerate global warming.

It's not clear how the loss of sea ice would affect the world's oceans. Sea ice is basically fresh water. When it melts, the salt content of ocean water would decrease. Right now, the world's oceans are layered with salty, cold water from the Arctic that is concentrated in a deep ocean layer. In the future, the less-salty water could mix more easily into oceans, disturbing the layering. This could affect ocean currents, global climate, and the productivity of the ocean ecosystem in ways that are not yet fully understood.

Finally, several species of animals, notably polar bears, rely on Arctic sea ice for survival. If it all melted, the only polar bears left would probably be in zoos.

Related Virginia science Standards of Learning: 2.5, 2.7a; 3.4, 3.6a, 3.10b; 4.5f; 5.7f; 6.5g; LS.4c, LS.11c, LS.12; ES.7, ES.11; BIO.9d.
Jim Beard is the curator of geology at the Virginia Museum of Natural History in Martinsville.