Holocene glacial fluctuations in the southern Kenai Mountains, Alaska

Recent retreat of outlet glaciers from the Harding and Grewingk-Yalik Icefields has revealed a vast array of deposits which record multiple advances into coastal forests during the late Holocene. Tree-ring dating together with radiocarbon and lichenometric analyses allow for the reconstruction of these glacial fluctuations with decadal precision over the past two thousand years.; The records of fluctuations of 21 glaciers include 16 land-terminating glaciers, three tidewater glaciers and two cirque glaciers. Three major Holocene glaciations are evident and date approximately 3600 yr BP, 500 A.D., and the Little Ice Age, 1300 to 1850 A.D.; The earliest expansion beyond present margins is known only from the McCarty tidewater glacier. Land-terminating glaciers advanced simultaneously with tidewater glaciers about 500 A.D. However, later, during the Little Ice Age, tidewater glaciers advanced several centuries prior to their land-terminating neighbors.; Those glaciers terminating on the east, maritime mountain flank are more sensitive to variations in winter precipitation, which contrasts with inland glaciers on the west flank that are affected more by summer temperatures. These glacial records suggest that advances during 1460 A.D., between 1640 and 1670 A.D., about 1750 A.D., and from 1880 to 1910 A.D. reflected times of increased winter precipitation. Advances between 1440 to 1460 A.D., from 1650 to 1710 A.D., and from 1830 to 1860 A.D. reacted to cool summers.; Glaciers from the western mountain flank reached their Little Ice Age maxima, also the Holocene maxima for southern Kenai Mountain glaciers, as much as two centuries earlier than those on the eastern mountain flank. An ice divide migration model is proposed to help explain this observation. Glaciers terminating in the more continental climatic regime on the western side have been steadily retreating for the past century, in part, facilitated by increased ablation in large proglacial lakes. Four glaciers terminating on the more maritime, eastern flank are either thickening or showing terminal advances, in part, because of increased winter precipitation coupled with global warming along the Gulf of Alaska.