DECADAL-SCALE HOLOCENE CLIMATE VARIABILITY IN THE GULF OF ALASKA USING HIGH-RESOLUTION MARINE SEDIMENT RECORDS

The Gulf of Alaska in the Subarctic Northeast Pacific Ocean is a unique region where atmospheric circulation and ocean conditions are linked directly with marine ecosystem variability. Observations of modern climate in the Gulf of Alaska indicate strong teleconnections across the Northern Hemisphere, while outputs from coupled atmosphere-ocean GCMs suggest that environmental changes occurring here can force downstream climate variability, particularly during periods of abrupt climate change. The importance of this region is diminished however by the relatively short period of historical observations that range only to the previous century. Recent work on tree-ring and marine invertebrate archives have extended the paleoclimatology of the Gulf of Alaska in annual resolution over the last millennia, yet such detail for periods prior to AD 1000 require new sources of information.

We present results from a set of high-resolution marine sediment cores from the Gulf of Alaska margin collected by the EW0408 science party that extend to the early Holocene. Using proxy methods to reconstruct both marine primary productivity and terrestrial freshwater runoff, we show that decadal-scale variability in phytoplankton abundance has a significant correlation with a tree-ring reconstruction of the Pacific Decadal Oscillation for the last millennia. Extrapolating this relationship to the early Holocene shows that decadal-scale variability in atmospheric and oceanic systems has been a persistent feature since at least 7500 cal yrs BP. However, we also find evidence of centennial-scale oscillations that manifest as “mega-regime shifts” in the linked atmosphere-ocean-ecosystem configuration in the Gulf of Alaska. This variability is mirrored in several key archives from the terrestrial margin, and thus a synthesis of lake, ice, and marine datasets yields important new insight into the paleoclimatology of the Gulf of Alaska during the Holocene. In particular, we highlight environmental and ecological transitions associated with the onset of the Little Ice Age (AD 1200) and the mid-Holocene Neoglaciation.