 The mass balance , or difference between accumulation and ablation ( melting and sublimation ) , of a glacier is crucial to its survival . Climate change may cause variations in both temperature and snowfall , resulting in changes in mass balance . A glacier with a sustained negative balance loses equilibrium and retreats . A sustained positive balance is also out of equilibrium and will advance to reestablish equilibrium . Currently , nearly all glaciers have a negative mass balance and are retreating . 
