COASTAL ALASKA AND COASTAL EASTERN US PALEOECOLOGY/PALEOCLIMATE - HOW DO DEGLACIATION, COLONIZATION, YOUNGER DRYAS, NORTHWARD TREE MIGRATION, HOLOCENE THERMAL MAXIMUM, NEOGLACIATION, AND PEAT FORMATION COMPARE? (Invited Presentation)

Ice recession along the N. Pacific Alaskan margin occurred as early as 16,000 cal yr BP, but most coastal sites around the rim record even younger ages. Eastern Laurentide ice sheet recession dates to between 16-15 kyr BP across the moraine margin of CT, NY, and NJ. Earliest late-glacial sediment records from both regions indicate similar tundra components including Dryas, dwarf birch, crowberry, and willow, but while mixed late-glacial boreal forest characterizes the Bolling-Allerod in the northeastern US, Alaskan late-glacial records generally lack trees with the exception of lodgepole pine and mountain hemlock in southern sites. The cold, dry Younger Dryas in Alaska shows a lithological shift along with a “fern gap”, increases in wormwood and crowberry, while a cold, wet YD is characteristic of the eastern US with fir, spruce, paper birch and alder. The Holocene vegetational history is marked by in the Pacific northwest by stepwise arrival and expansion of Sitka spruce, mountain hemlock, and western hemlock northwestward, while in eastern North America the larger seed sources and landmass pathways resulted in a more diverse boreal forest in the late-glacial which led to first white pine and then oak dominance in the early Holocene. Droughts are evident on both coastlines as shifts from Sphagnum to sedge dominance in Holocene bog records, and Neoglaciation in both regions is characterized as a cooler, wetter interval with interesting and varied vegetational response. Warming climate since the 1950s is evident in both regions. Reasons for the differences in ecological response on different sides of the continent throughout the late-glacial and Holocene will be discussed.