Conventional reading suggests glaciers and ice sheets are formed top-down, by the cumulative compaction of snowflakes. New research published in Science today shows there is a bottom-up component too – at least for the East Antarctic ice sheet.
Ice sheets act as insulators from the cold polar weather conditions above. Deep down temperatures are higher because of increased influence of the Earth’s mantle. Friction caused by combined weight and movement underneath massive glaciers creates additional heat and causes part of the ice mass to melt. As the pressures are extremely high part of this melting water is forced uphill, towards the glacier source, the Gamburtsev Mountain Range, or Antarctic Alps, where it then refreezes and adds fresh ice mass to the glacier system.
Operating ice-penetrating radars, laser ranging systems, gravity meters, and magnetic sensors from two planes the researches found this process to be much more important than previously suspected – with up to 50 percent of glacier ice actually being refrozen and remixed melt water.
Flawed ice sheet models?
Ramifications for current ice sheet melting speeds are unclear, but one of the researchers, glaciologist Donald Blankenship of the University of Texas, states this at least shows current ice sheet models miss an important factor, by not paying special attention to processes at the bottom of the glaciers.
Comparing ice dynamics models to paleostudies of ice sheet behaviour suggests current models fail to represent the non-linearity of the melting process. It means our model studies are usually [model 1, model 2] more optimistic than historic data can correspond.
© Rolf Schuttenhelm | www.bitsofscience.org