Sea Level Rise Foretold in Glacier

Tasiilaq, Greenland. From a helicopter hovering over the vast landscape of Greenland, oceanographer Fiammetta Straneo and her colleagues are attempting to answer one of the most urgent — and most widely debated — questions facing humanity: How fast is the world’s ice going to melt?

Dwarfed by the immensity of the landscape, the researchers’ helicopter is a red speck of machinery lost in a wilderness of rock and ice. To the right, a great fjord stretches toward the sea, choked with icebergs.

To the left looms one of the huge glaciers that brings ice from the top of the Greenland ice sheet, dumping it into the ocean.

Hanging out the sides of the craft, two scientists send a measuring device plunging into the water, between ice floes. Near the bottom, it reports a temperature of 40 degrees. It is the latest in a string of troubling measurements showing that the water is warm enough to melt glaciers rapidly from below.

“That’s the highest we’ve seen this far up the fjord,” Straneo says.

Scientists long believed that the collapse of the gigantic ice sheets in Greenland and Antarctica would take thousands of years, with sea level possibly rising as little as 18 centimeters in this century, about the same amount as in the 20th century.

As a result of recent calculations that take the changes into account, many scientists now say that sea level is likely to rise perhaps a meter by 2100 — an increase that, should it come to pass, would pose a threat to coastal regions the world over.

And the calculations suggest that the rise could conceivably exceed two meters, which would put thousands of square kilometers of the American coastline under water and could displace tens of millions of people in Asia.

Some of the world’s great cities — New York, London, Cairo, Bangkok, Venice and Shanghai among them — would be critically endangered by a one-meter rise in the sea.

Climate scientists readily admit that the meter estimate could be wrong. Their understanding of the changes going on in the world’s land ice is still primitive. But, they say, it could just as easily be an underestimate as an overestimate.

Melting ice is by no means the only sign that the earth is warming. Thermometers on land, in the sea and aboard satellites provide additional evidence.

Heat waves, flash floods and other extreme weather events are increasing. Plants are blooming earlier, coral reefs are dying and many other changes are afoot that most climate scientists attribute to global warming. Yet rising sea levels could turn out to be the single most serious effect.

While the United States is among the countries at greatest risk of the effects of rising sea levels, neither it nor any other wealthy country has made tracking and understanding the changes in the ice a strategic national priority.

The consequence is that researchers lack elementary information on the phenomenon.

They have been unable even to measure the water temperature near some of the most important ice on the planet, much less to figure out if that water is warming over time. Vital satellites have not been replaced in a timely way, so that American scientists are losing some of their capability to watch the ice from space .

The gaps in information make it impossible for scientists to be sure how serious the situation is.

In the United States, the Obama administration is seeking to chart a new course, abandoning the goal of returning to the moon and seeking a substantial increase in financing for earth sciences.

Major elements of the administration’s program won support from both parties on Capitol Hill and were signed into law recently, but amid a larger budget impasse, Congress has not allocated the money President Barack Obama requested.

In the meantime, NASA is spending about $15 million a year to fly airplanes over ice sheets and glaciers to gather some information it can no longer get by satellite, and projects are under way in various agencies to plug some of the other information gaps.

Climate scientists note that while the science of studying ice may be progressing slowly, the world’s emissions of heat-trapping gases are not.

“The past clearly shows that sea-level rise is getting faster and faster the warmer it gets,” German climate researcher Stefan Rahmstorf said.

“Why should that process stop? If it gets warmer, ice will melt faster.”

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