July 28, 2016
Sater Glacier is in the Okpilak River watershed of the Brooks Range, Alaska. It is named for John Sater an early geologist working in the Brooks Range and on the nearby McCall Glacier. Here we examine Landsat imagery from 1987-2016 to identify changes in the glacier. Matt Nolan, U. Alaska-Fairbanks, has provided links to the recent research and publications at McCall Glacier. These glacier have suffered increased mass loss since 1990 as a result of an increase in the equilibrium line altitude that has reduced accumulation area and is indicative of increased ablation (Delcourt al , 2008) as noted at Slender Glacier.
In 1987 Sater Glacier extended from 2300 m to 1600 m with two main tributaries joining 1 km above the terminus. Retained snowcover blankets most of the glacier in this early August image. In 1995 the main change is the lack of retained snowcover on the glacier, with a month left in the melt season. The retained snowcover is the accumulation area ratio (AAR), which needs to be above 50% for a glacier to be in equilibrium, but is less than 10% in 1995. The 2012 Google Earth image above indicates very little retained snowcover on the glacier in mid-July, AAR of 15%. Likely no retained snowcover by summer’s end. In 2015 a late July image again indicates limited retained snowcover, the AAR less than 10%. In 2016 the late July image again indicates limited snowcover though slightly better than in 2015 with an AAR of 25%. This persistent failure to retain snowcover indicates a glacier than cannot survive (Pelto, 2010). This has also led to the near separation of the tributaries, retreat of the upper margins of the glacier and terminus retreat of 250 m. The retreat of the terminus has been much less than Okpilak Glacier, but the prognosis due to the lack of retained snowcover is much worse, it cannot survive current climate.
1995 Landsat image red arrow indicates 1987 terminus, yellow arrow 2015 terminus and purple arrows upglacier thinning.
2015 Landsat image red arrow indicates 1987 terminus, yellow arrow 2015 terminus and purple arrows upglacier thinning.
2016 Landsat image red arrow indicates 1987 terminus, yellow arrow 2015 terminus and purple arrows upglacier thinning.