Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller
Glacier over the past two millennia are reconstructed using 34 radiocarbon
dates and tree-ring data from 16 sites across the glaciers' forelands. The
general sequence of glacial activity is consistent with well-dated fluctua
tions of tidewater and land-terminating glaciers elsewhere along the Gulf o
f Alaska. Extensive forested areas along 25 km of the Bering ice margin wer
e inundated by glacio-lacustrine and glacio-fluvial sediments during a prob
able ice advance shortly before 500 cal yr A.D, Regrowth of forests followe
d the retreating ice as early as the 7th century A.D., with frequent interr
uptions of tree growth due to outwash aggradation. Forests overrun by ice a
nd buried in outwash indicate readvance about 1080 cal yr A.D. Retreat foll
owed, with ice-free conditions maintained along the distal portions of the
forefield until the early 17th century after which the ice advanced to with
in a few kilometers of its outer Neoglacial moraine, Ice reached this posit
ion after the mid-17th century and prior to 200 yr ago. Since the early 20t
h century, glacial retreat has been punctuated by periodic surges. The reco
rd from forests overrun by the nonsurging Steller Lobe shows that this west
ern ice margin was advancing by 1250 A.D., reaching near its outer moraine
after 1420 cal yr A.D. Since the late 19th century, the lobe has dominantly
retreated. (C) 1999 University of Washington.