GULF OF ALASKA ATMOSPHERE-OCEAN VARIABILITY OVER RECENT CENTURIES INFERRED FROM COASTAL TREE-RING RECORDS

Eight tree-ring chronologies from coastal sites along the Gulf of Alas ka (GOA) are used to develop a 227-year (1762-1988) reconstruction of spring/summer (March-September) coastal land temperatures for the regi on. This reconstruction explains 35% of the variance in the instrument al temperature data. The tree-ring records and reconstruction reflect the documented 1976 transition from cold to warm conditions in the Nor th Pacific and are consistent with regional temperature compilations. Three of the eight ring-width series, from elevational timberline site s where trees are particularly stressed by temperature, extend back to A.D. 1600 and are used to identify additional occurrences of such tra nsitions. The first principal component (PC) scores of these three lon ger records are positively correlated with spring (March-May) land and sea surface temperatures for the GOA region and are used to reconstru ct land surface temperatures. Decadal-scale fluctuations in the recons tructions show agreement with decade-long changes in the intensity of the Aleutian Low pressure cell over the past century, suggesting that the tree-ring data may provide an index of past circulation changes fo r the northeast Pacific. Blackman-Tukey spectral analyses of both reco nstructions indicate significant power at 7-11 years, with additional peaks at 3 years for the spring/summer reconstruction and 19 years for the longer spring temperature series. The modes of variation at about 3 and 7 years may correspond to those associated with the El Nino-Sou thern Oscillation bandwidth, whereas the 19-year term may relate to a proposed 20-year cycle of North Pacific circulation. The spring temper ature series shows generally increased growth over the past century, c oinciding with warmer spring temperatures in south coastal Alaska over this interval. Comparison with the entire spring series suggests that the recent warming exceeds temperature levels of prior centuries, ext ending back to A.D. 1600.