Decline and Fall of a Glacier
The glaciers around Puncak Jaya have long been in visible decline. From 1936 to 2006, they lost nearly 80 percent of their area–two-thirds of that since 1970, according to a new paper by glaciologist Michael Prentice of the Indiana Geological Survey, who has long been interested in the area. Satellite images show that from 2002 to 2006 alone, the remaining ice decreased from 2.326 square kilometers to 2.152–a 7.5 percent drop. Now, with researchers there, other signs have become obvious. Take a look at the pictures below of the Northwall Firn Glacier, about 2.5 kilometers from the summit of Puncak Jaya, taken by Paul Q. Warren, a geologist with the Freeport McMoRan company who has been helping plan and execute the ice-coring project since October 2008.
This meltwater lake has formed on the surface of the glacier—a possible portent of quickening destruction. For one thing, liquid water tends to absorb more heat than does snow or ice, which reflect energy. Once a pond forms, it can become a hot spot that eats away everything around it--and indeed, you can see how this one has drilled down through layers of ice. Eventually it will hit the rock bed of the glacier. There the water may flow into and lubricate the bed causing the glacier to slide downhill faster. The water may then find its way to the glacier’s edge, forming a drain of running water that will help consume the ice from the bottom. (Paul Warren calls this picture “the ice jacuzzi.”) (click to view enlargement)
At the first drill site, faults in the ice (black lines with arrows) are obvious. Here, the ice is cracking and moving, as the glacier shifts around. Such faults are common on alpine glaciers, but movement could be hastened by the recent rapid melting. In analyzing these faults, Paul Warren has borrowed some terms from earthquake experts. According to him, most of the cracks are “thrust faults,” which means that older layers of ice have been thrust upward over younger ones. Others are so-called “normal faults,” where younger layers of ice have dropped below the older ones. Some faults were likely intersected by the coring (red line). It is important to know how the faults have moved, because their presence means that when studying the ice cores, one cannot simply assume that one is seeing the newest ice on the top and the oldest on the bottom. (click to view enlargement)
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