 Methods for measuring retreat include staking terminus location , global positioning mapping , aerial mapping and laser altimetry . The key symptom of disequilibrium is thinning along the entire length of the glacier . This indicates a diminishment of the accumulation zone . The result is marginal recession of the accumulation zone margin , not just of the terminus . In effect , the glacier no longer has a consistent accumulation zone and without an accumulation zone cannot survive . For example , Easton Glacier in Washington state , U.S. will likely shrink to half its size but at a slowing rate of reduction and stabilize at that size despite the warmer temperature over a few decades . However , the Grinnell Glacier in Montana , U.S. will shrink at an increasing rate until it disappears . The difference is that the upper section of Easton Glacier remains healthy and snow @-@ covered , while even the upper section of the Grinnell Glacier is bare , is melting and has thinned . Small glaciers with minimal altitude range are most likely to fall into disequilibrium with the climate . 
