Retreating Alaskan Glacier Reveals Remains Of Medieval Forest
By Paul Homewood
The Exit Glacier, Alaska
Reader agfosterjr sent me a link about the Exit Glacier, in southern Alaska, pointing out, as the glacier retreats, it is uncovering remains of a medieval forest, as this report from the National Park Office makes clear:-
The Little Ice Age (LIA) was a time of global cooling from approximately 1350 to 1870 AD. During this time glaciers expanded in the northern regions, moving down the mountains and scouring the vegetation that had been in the valleys below. Park Service personnel recently discovered evidence of a buried forest dating back to at least 1170 AD high in the Forelands near the current glacier’s edge.
This report, of course, tallies with studies of other Alaskan glaciers, which have also found similar tree remains. What I found equally intriguing though was this table, that was included in the report, showing how the rate of retreat has changed since the 19thC.
The retreat began slowly after 1815, but really accelerated after 1889. The fastest rate was 1914-17, but since then the glacier has been retreating much more slowly.
I was puzzled though by the fact that the table finished in 1973, confused further by the fact that the bottom line mentions 1815-1999. The total retreat of 6549 ft for that whole period is the sum of the individual periods, so I wondered whether the retreat had stopped altogether since 1973.
[The National Park report is based on research undertaken in 2001, so logically the figures up to 1999 should be correct]
So I did some more research and found this study by Katie Baumann, based on National Park mapping.
[There may be a problem with this link]
Let’s home in on the right hand map. The retreat from 1950 to 1973 is very clear, but since then there has been no significant change. Indeed the current glacier extent seems to be greater than in 1985. As the footnote says, the last 35 years have seen a mixture of advance and retreat.
This of course is only one glacier, and I certainly would not suggest that it is representative of all glaciers in Alaska. But it is clear that the Exit Glacier began retreating at the end of the LIA, retreated at a much faster pace between 1889 and 1917 than anything seen since, and stopped retreating 40 years ago.