COASTAL NORTHEAST PACIFIC PROXY RECORDS AND THEIR ROLE IN UNDERSTANDING REGIONAL CLIMATE FORCING

Coastal Northeast Pacific forests and glaciers are sensitive to changes primarily in summer temperatures. This vast region along the southern Alaskan coast is one of the least human-impacted ecosystems on Earth and one of the most vital land masses for the health of terrestrial and marine biological populations. A combination of glacial histories and tree-ring records spanning the last several millennia help characterize the various modes of climate variability for this extensive Pacific coastal temperate rainforest.

Tree-rings in coastal and near coastal setting are proxies for surface air and sea surface temperatures, as well as derived climate indices of Pacific Decadal Variability. A variety of methods allow for low frequency (millennial to century scale) and high frequency (decadal to annual) signals to be extracted from the ring-width series. Advance histories from land-terminating glaciers are similarly records of summer temperature, as well as winter precipitation on multi-decadal to millennial timescales. Tree-ring reconstructions from the region can be compared with glacier records as a mutual assessment of the fidelity of the reconstructions. For example, in the low frequency domain, external forcings including Milankovich and century-scale solar forcing are recognized and are largely consistent in both the glacial and tree-ring records. On shorter timescales, solar, tidal and volcanic forcings are recognized in the tree-ring record but not in the coarser resolution of the glacier histories.

New methods of extracting temperature signals in tree rings (blue intensity) offer the possibility of additional high frequency climate information from the tree-ring series. On longer timescales, improved chronologies of land-terminating glaciers, and a better understanding of tidewater glacier fluctuations that often have advanced for multiple centuries potentially offer climate information as well as better understanding of the roles of glaciers in modulating climatic and hydrologic processes in coastal ecosystems. The roles of external and internal forcing and their relative contribution to climate variability in the complex Northeast Pacific coupled glacier – forest – hydrologic systems are under investigation.