RECONSTRUCTING LITTLE ICE AGE GLACIAL HISTORIES FOR CRESCENT AND AMHERST GLACIERS, COLLEGE FIORD, SOUTHERN ALASKA

The melting of Alaskan glaciers is one of the most dramatic examples of contemporary warming. Ice retreat is revealing a rich record of previous expansions for the past several hundred years. Amherst and Crescent Glaciers, in College Fjord, Prince William Sound, southern Alaska, have been retreating over the past 150 years. Using tree-ring and radiocarbon dating we are able to date overrun trees, which yield times of ice expansion. Ages of trees growing on moraines provide minimum estimates for moraine building and ice retreat.

Tree cores from living trees, as well as subfossil logs, have been sampled for tree-ring dating at Amherst Glacier. Crossdating the Amherst tree ring series chronology against Prince William Sound master chronology provides an advance date of AD 1633. Ages of trees growing on a moraine at Amherst Glacier suggest moraine building shortly before AD 1830. A raft of overrun trees in the Crescent Glacier's outwash stream within the recent glacial limit was similarly dated. Crescent Glacier's master chronology from subfossil logs was dated against the master chronology from Prince William Sound to determine that the glacier was advancing about AD 1635. Trees growing on three moraines suggest building before AD 1775, 1800 and 1935.

Results indicate that Crescent and Amherst Glaciers were advancing during the cold period associated with the Maunder Minimum, an interval recognized in nearby tree-ring reconstructions. These glacier records are consistent with previous studies from the Gulf of Alaska, which suggest that this 17th century interval was among the coldest intervals of the Little Ice Age in southern Alaska.