 Long @-@ term mass balance records from Lemon Creek Glacier in Alaska show slightly declining mass balance with time . The mean annual balance for this glacier was − 0 @.@ 23 m ( 0 @.@ 75 ft ) each year during the period of 1957 to 1976 . Mean annual balance has been increasingly negatively averaging − 1 @.@ 04 m ( 3 @.@ 4 ft ) per year from 1990 to 2005 . Repeat glacier altimetry , or altitude measuring , for 67 Alaska glaciers find rates of thinning have increased by more than a factor of two when comparing the periods from 1950 to 1995 ( 0 @.@ 7 m ( 2 @.@ 3 ft ) per year ) and 1995 to 2001 ( 1 @.@ 8 m ( 5 @.@ 9 ft ) per year ) . This is a systemic trend with loss in mass equating to loss in thickness , which leads to increasing retreat — the glaciers are not only retreating , but they are also becoming much thinner . In Denali National Park , all glaciers monitored are retreating , with an average retreat of 20 m ( 66 ft ) per year . The terminus of the <unk> Glacier has been retreating 26 m ( 85 ft ) per year and the Muldrow Glacier has thinned 20 m ( 66 ft ) since 1979 . Well documented in Alaska are surging glaciers that have been known to rapidly advance , even as much as 100 m ( 330 ft ) per day . Variegated , Black Rapids , Muldrow , Susitna and <unk> are examples of surging glaciers in Alaska that have made rapid advances in the past . These glaciers are all retreating overall , punctuated by short periods of advance . 
