Holocene history of Hubbard Glacier in Yakutat Bay and Russell Fiord, southern Alaska

Stratigraphic and geomorphic data defined by radiocarbon ages, tree-ring da tes, and historical observations provide evidence of three major Holocene e xpansions of Hubbard Glacier, Early in each advance the Hubbard Glacier mar gin blocked Russell Fiord to create Russell Lake, raising base level and ca using stream beds and fan deltas throughout the Russell drainage basin to a ggrade. Each Hubbard Glacier expansion continued with an ice lobe advancing through Disenchantment and Yakutat Bays in the west, and an eastern lobe a dvancing into Russell Fiord. The earlier two Holocene expansions were, respectively, under way at 7690 a nd 5600 calibrated yr B.P., and each advance culminated more than 1 k.y. la ter. The late Holocene advance was under way by 3100 yr ago and reached sim ilar to 13 km farther south in Russell Fiord than the preceding two expansi ons. Late Holocene deglaciation of Yakutat and Disenchantment Bays was comp lete before A.D. 1791; Nunatak Glacier flowing from neves east of Russell F iord became the primary ice source to the Russell Fiord lobe at or before t his date. Ice retreat from the southern end of Russell Fiord began in the l ate eighteenth century and the penultimate Russell lake drained ca, A,D, 18 60. The relatively slow advances and more rapid retreats of Hubbard Glacier are consistent with the model of the iceberg-calving glacier cycle. Hubbard Gl acier is currently advancing and will likely reestablish Russell lake in th e near future, affecting local fisheries. However, glacier lobes are unlike ly to reach the area of the town of Yakutat, built on late Holocene glacial deposits, in the next 1 k.y.