14 DAY TRIAL // A new survey conducted by the American space agency's Ice, Cloud, and land Elevation Satellite (ICEsat) has revealed that more and more ice is falling off the Greenland and Antarctic sheets into the world's oceans, as glaciers get thinner on account of global warming. The formations increase their flow rates to the sea, which translates into a constantly increasing sea level. The scientific data collected by the ICEsat mission provides scientists with the necessary tool to probe the changes in more detail than ever, the BBC News reports.
According to a new report, published in the latest issue of the scientific journal Nature by a team of scientists from the UK, if Greenland's ice sheets melt completely, we could be looking at a seven-meter (20-foot) increase in ocean levels worldwide. This would put the millions of people living in cities such as Tokyo, New York and Rotterdam at risk of flooding and death. The rise would be even greater if the Antarctic ice sheet collapsed as well, the team reports. Coastal maps could be completely redrawn, they say. As a note, the historic, 13-century-old city of Venice would disappear.
Compiling accurate projections and models of sea-level rises has proven thus far to be extremely difficult, mostly because scientists have had no way of assessing the extent of “dynamic thinning,” or the rate at which glaciers move and flow. “All of the glaciers that are changing rapidly are [the] ones that flow into the sea. The fact that they end in the sea means a buoyancy effect is working on them. Normally, they're heavy things and they rest on the sea-bed and friction slows them down. But as you start to thin glaciers, they start to float off the sea-bed more and more; there's less friction and the glaciers can speed up,” British Antarctic Survey (BAS) expert Hamish Pritchard told the British news agency.
The truly negative effects of this acceleration can only be understood when analyzing precipitation rates. A quick look at how much ice is deposited in the average year tells you immediately that the amount of lost ice far exceeds anything rain and snow can replenish. The ICEsat data makes this abundantly clear. It recorded a loss of height in most glaciers in the ice sheets. In some cases, the drop was considerable, and, worst of all, unexpected. This means that climate models for these regions may have actually underestimated the rate at which global warming and climate change act.
“If these were changes solely related to atmospheric conditions, either changes in temperature or snowfall, we would expect the glaciers and the nearby ice to be showing the same signal; and they don't. The glaciers are thinning because they are speeding up. Because they're flowing more rapidly to the ocean, they are discharging more ice into the ocean than is being replaced by new snowfall. The balance is loss,” BAS expert, Professor David Vaughan concludes.
