We entered Glacier Bay just after dawn on August 30, and being the only cruise ship there, spent the better part of the day perusing a half dozen glacial faces. The one just below is Johns Hopkins Glacier at the head of the inlet of the same name. The tongue of white ice coming in from the left at the water line about 1/4 into the scene is a bit of Gilman Glacier. This photo was taken about 3:00 in the afternoon from about 6 miles distant.
Johns Hopkins Glacier continues to advance with Gilman Glacier as a single ice front. The glacier is about 1-mile wide, 250 feet high at the terminus, and 200 feet deep at the water line. It is formed from numerous tributary glaciers, many of which extend 12 or more miles into the surrounding peaks. About 50 medial moraines develop from the joining of these tributary glaciers. The debris in these moraines can be seen in the ice face and extending up-glacier as prominent black bands. This debris is transported in and on the ice and released either by melting of the ice face or calving of icebergs into Johns Hopkins Inlet. Melt-water from the glacier is discharged from submarine tunnels or conduits located near both the eastern and western edges of the glacier.Sometimes this water emerges at the inlet surface as fountains. Birds are commonly seen diving and floating where the melt-water up-wells along the ice face.
Johns Hopkins joined Gilman Glacier at its eastern edge in about 1990. During the decade following this merging of the ice, the two glaciers have separated and joined several times. The two glaciers were once again attached at the eastern edge of Johns
Hopkins in 2000 and both are now advancing slowly with a 150 to 200 foot steep ice face where they join.
Of note, Johns Hopkins is characterized by submarine calving -calving below the water surface caused by breaking off of ice from an “ice foot” that extends from the basal part of the glacier. These “basal bergs” rise suddenly and unexpectedly, emerging, sometimes explosively, without warning at the water surface. In late July 2003, submarine calving was extremely active.
The prediction that glaciers will be gone from Glacier National Park has been moved up by 10 years to 2020, the same year it’s predicted the Arctic Sea will be ice-free in the summer.