The Arctic Ocean is the smallest and shallowest of the Earth's five oceans. In recent years its surrounding commental kind masses have wanned rapidly. The consequences of this will he profound. The Arctic is now heating up twice as fast as the rest of our planet. This permits vegetation to move northward, increasing the rate of warming as reflective snow cover decreases. Then the warmer land lets subsurface permafrost thaw, releasing the potent greenhouse gas methane. It is a feedback-loop process that has greatly accelerated Arctic warming in the past half decade.
Until a few years ago, the wintertime Arctic Ocean and adjacent Bering Sea were completely ice-covered by seasonal and multiyear ice from 3- to 13-feet thick. In summer, the annual ice melt left about half this cover in place. Over the past five years, this has all changed. Winter ice cover is now decreasing at the rate of more than 3 percent a decade. The change is even greater in the summer. Since the 1970s, summer ice cover has decreased by 30 percent while the total volume of ice decreased by about 40 percent.
Geographically speaking, an ice-free Arctic Ocean in summer is assured. Depending on the expert, the "when" could he from 10 to 50 years. Eventually, the Arctic Ocean will he ice-free year "round, something that last happened about a million years ago.
One reason predictions are so imprecise is that oceanographic research in an ice-covered ocean is extremely difficult. However, a half-century of nuclear-powered submarine operations by the United States, Great Britain, Soviet Union, and Russia have provided an extensive database on this least-known ocean. Especially useful were the submarine-derived year 'round measurements of ice cover area and its thickness.
While melting of sea ice does not raise sea level since it is already floating, the increased ice-free urea does result in a warming of the ocean. Ice acts us a mirror for the sun's low-angle rays, reflecting this energy back into space. With the mirror gone, the exposed, darker surface waters more readily absorb solar energy. As the ocean warms, more ice melts, and the rate of warming accelerates.
A major global impact from Arctic Ocean heating is a weakening of the Gulf Stream and the warm northern currents it spawns. This great river in the sea transports thermal energy from the equatorial Atlantic to the high latitudes of Northern Europe. It provides an average 18° F temperature increase for the British Isles and Scandinavia compared to equivalent latitudes in North America or Siberia. So as this flow weakens, Europe will become cooler.
Gulf Stream slowing is already evident. In the past 12 years, the flow has diminished by 30 percent and will lead to lower temperatures on land. Sonic experts predict the Gulf Stream may eventually stop altogether. And there is historic evidence that this happened before.
A warmer Arctic Ocean is not all had news. In the near term, greatly reduced ice cover will permit global maritime shipping to use this ocean tor safe navigation in all but the coldest winter months. Compared to ship routes used today, a northern sea route between Asia and Europe would save 4,000 miles in the transport of goods between the two regions.
Meanwhile, Greenland, which contains 11 percent of the world's land-hound ice, has also been the subject of careful ice-cover measurements. In recent years, the data show a net annual loss of land ice to the sea at a rate that is slowly increasing. Since the ice is on land, whatever goes into the sea contributes directly to sea level rise.
At present, global sea level rise owes equally to two factors: wanning of the oceans (heated water expands) and land-bound ice melt. Eventually, the effect of the latter will dominate.
Experts have estimated that if all the ice on Greenland melts, then sea level will rise about 17 feet. Since 8 out of 10 major cities in the world are on a coast, rising sea level will be a matter of great concern in future years. And it is a future that is not that far away. Recent research has shown that major ice movements from land to sea can occur very rapidly, often measured in years rather than decades or centuries.
It is not clearly understood why the Arctic regions of our planet are warming so rapidly, but the effects are clear. There are many theories, and much more scientific investigation is needed. However, there is no ambiguity about the basic issue: the Arctic Ocean is losing its cool. And the consequences are going to affect all of us.