Archives for August 25, 2009

“FOR a glacier to maintain its present size it must have precipitation as snowfall at its source. This leads to a slightly complex relationship with temperature. If the regional climate becomes too dry, there will be no precipitation, so the glacier will diminish. This could happen if the region became cold enough to reduce evaporation from the ocean. If temperatures rise, evaporation is enhanced and so therefore is snowfall. Paradoxically a regional rise of temperature may lead to increased growth of glaciers and ice sheets. Today, for example, the ice sheets of both Antarctica and Greenland are growing by accumulation of snow…

“In the Greenland ice sheet several cores have more than 3 km of undisturbed ice which go back in time for over 105,000 years, much less than the Antarctic equivalent. The Vostok cores in Antarctica provide data for the past 414,000 years before the ice starts to be deformed. Dome F core reached 3035 m and Dome C core 3309 m, and both date back to 720,000 years. The Epica core in Antarctica goes back to 760,000 years, as does the Guliya core in Tibet. But what is more important than the age is that vast thicknesses of ice are preserved, and they retain complete records of deposition, in spite of the fact that temperatures at times during that period have been warmer than now. They do not fit the model of surface melting, either now or then. After three quarters of a million years of documented continuous accumulation, how can we believe that right now the world’s ice sheets are collapsing!” [Read more…] about Understanding Ice Sheets and Collapse