FIVE NEW MOUNTAIN HEMLOCK TREE-RING CHRONOLOGIES FROM SOUTHEAST ALASKA: NEW RECORDS OF CLIMATE

Five new tree-ring records from along the Gulf of Alaska illustrate a range of climate responses. These include the background climate of the ocean-atmosphere system, the influence of katabatic winds from a major tidewater glacier system and tree damage caused by windstorms. Sorting out these signals is a challenge and an opportunity for reconstructing and understanding climate changes in the Northeast Pacific. The sites range from 50 to 600 meters in elevation and only one of the five series appears to be tracking the climate warming over the past several decades. Large-scale tropical volcanic coolings events from tropical eruptions in the late 1690s and 1809-10 are evident in most of the series and all five show a strong cooling in 1973, a poorly studied climate anomaly an unknown event in climate that is strongly expressed in tree and weather records from coastal Southeast Alaska.

Divergent climate responses are evident in the two ring-width series derived from growing within a kilometer of the expanded tidewater glacier system in Glacier Bay National Park and Preserve. One series shows a multidecadal suppression of growth during the ice maximum and the other, in a comparable location with respect to the ice, shows only a modest suppression to cooling forced by the nearby glacier. We will also present tree-ring comparisons with indices of Pacific Decadal Variability, and test a recent hypothesis about the nature and drivers of centennial-scale climate variability in the GOA based on newly-published speleothem data. The hypothesis suggests that linkages to solar variability and ENSO have been linked for millennia and only recently (after ~1970) this relationship has changed with ENSO now being dominated by anthropogenic forcing.