New studies have shown that the global temperature is increasing and the polar ice is melting more rapidly than was expected helping dramatic climate and ocean condition changes. If 5 years ago someone would have ventured that in 2014 the Arctic would be ice free in summer he would have been laughed at. Today, “that is fairly unlikely but a possibility” said Walter Meier, cryosphere scientist at the National Snow and Ice Data Center, University of Colorado in Boulder at a NASA media briefing yesterday.
Scientists have changed their minds on the speed of the Arctic ice receding. So far it was expected that the Arctic would be ice-free in summer by the end of the century. That has dramatically changed – now it is estimated to happen in as few as 30 years. The updated forecast is the result of a new analysis of computer models coupled with the most recent summer ice measurements.
“The Arctic is changing faster than anticipated,” said James Overland, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory and co-author of the study, that appeared April 3 in Geophysical Research Letters. “It’s a combination of natural variability, along with warmer air and sea conditions caused by increased greenhouse gases.”
Overland and his co-author, Muyin Wang, a University of Washington research scientist with the Joint Institute for the Study of the Atmosphere and Ocean in Seattle, analyzed projections from six computer models, including three with sophisticated sea ice physics capabilities. That data was then combined with observations of summer sea ice loss in 2007 and 2008.
The summer sea ice currently covers 4.6 million square kilometer (about 2.8 million square miles). The new observations and calculations created an expectation that the area would decrease to about 1 million square kilometers (about 620,000 square miles) – a loss approximately four-fifths the size of the continental U.S. Much of the sea ice that would decrease is between Alaska and Russia in the Pacific Arctic and would mostly remain in the area north of Canada and Greenland.
“Ice extent is an important measure of the health of the Arctic, but it only gives us a two-dimensional view of the ice cover,” said Walter Meier. “Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it grows more vulnerable to melting in the summer.” Each year the wind flushes out about a tenth of the total ice, which constitutes an area about the size of Texas, which is then replenished over the next season. The years between 2005 and 2007 were unusual though as there was almost no replenishing of the older thick ice, leaving behind newer ice that is not thick enough to survive the summers.
Until recently, the majority of Arctic sea ice survived at least one summer and often several. But things have changed dramatically. Thin seasonal ice — ice that melts and re-freezes every year — makes up about 70 percent of the Arctic sea ice in wintertime, up from 40 to 50 percent in the 1980s and 1990s. Thicker ice, which survives two or more years, now comprises just 10 percent of wintertime ice cover, down from 30 to 40 percent. A slight increase last winter could be observed estimating a 10-15 percent of remaining thick ice this summer. “This ice could survive through the summer if it doesn’t get blown out of the Arctic” said Meier during the conference.
Sea ice thickness has been hard to measure directly, so scientists have typically used estimates of ice age to approximate its thickness. But last year a team of researchers led by Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., produced the first map of sea ice thickness over the entire Arctic basin.
Using two years of data from NASA’s Ice, Cloud, and land Elevation Satellite (ICESat), Kwok’s team estimated thickness and volume of the Arctic Ocean ice cover for 2005 and 2006. They found that the average winter volume of Arctic sea ice contained enough water to fill Lake Michigan and Lake Superior combined.
“The Arctic is often called the ‘Earth’s refrigerator’ because the sea ice helps cool the planet by reflecting the sun’s radiation back into space,” said Wang. “With less ice, the sun’s warmth is instead absorbed by the open water, contributing to warmer temperatures in the water and the air.”
In the meantime, similar studies are being conducted in the Antarctic. Weather stations, glacier movement sensors and in general investigative expeditions here are still too scarce to have such comprehensive analysis results as in the Arctic, but scientists are driven to learn more as they realized the dramatic consequences minor changes would have. Contrary to the Arctic, which is ice that covers water and therefore grows and melts into water, the Antarctic ice covers land. If only 1% of the Antarctic ice would melt, the oceans’ level would rise 65 centimeters (about 2.13 feet) with major implications for coastal areas.
Until now, it had been estimated that the temperature was decreasing, but It has now been reported that the Antarctic’s temperature actually went up 0.5C (0.9F) degrees between 1957 and 2006. In 2004 weeds started to grow and last month scientists reported drastic biological changes, such as decreasing amounts of plankton, which lead to decreasing amounts of krill, which in turn lead to decreasing number of the penguins that feed from the krill.
Kim Holmen, Research Director at the Norwegian Polar Institute, has said that the Antarctic is changing rapidly in an unexpected ways. Computerized models show that the increased water temperature could start the collapsing of ice platforms in the east, an occurrence that is already a fact in the west. In fact, only yesterday the ice bridge between the main Wilkins ice shelf and Charcot Island has collapsed, being the tenth major ice shelf collapses in recent years.
Scientists have enlisted the help of elephant seals to study depth, salinity and water temperature. The data provided by sensors tied to the animals’ backs have already confirmed that the water temperature is increasing more than the global average.
The worldwide patterns are related — as the Arctic starts losing ice cover in summer time, less heat will be refracted back into space and more will be absorbed by the water, changing water and wind currents, which in turn changes weather patterns and create warmer temperatures. Although satellite research only started in 1979, scientists are confident that the ice coverage is now much lower than in the past century. Despite not knowing exact figures and still learning to understand how the heat is stored in the water, one fact is clear — scientists have established that the amount of ice is diminishing due to warmer temperatures forced by greenhouse gases.
Copyright © 2009 by Marine Science Today, a publication of OceanLines LLC