Multi-proxy reconstructions of northeastern Pacific sea surface temperature data from trees and Pacific geoduck

We demonstrate the potential for developing sea surface temperature (SST) reconstructions in the northeast Pacific from combinations of tree-ring and growth-increment chronologies of the long-lived marine bivalve, the Pacific geoduck. Six Pacific geoduck chronologies developed from site along the Washington-British Columbia coast are compared and combined with tree-ring chronologies from California to Alaska. All chronologies are annually resolved and strongly relate to local to regional-scale SST, though differences in the response season as well as the spectral properties of the two proxies are observed. Both proxy types closely track SST and when used in combination, yield a more robust SST reconstruction than tree-ring or geoduck chronologies could provide alone. In total, variance explained in SST is 63.9% at the regional-scale and 68.2% at a local scale, providing SST estimates for more than 60 years prior to the start of continuous instrumental records in this region. This study represents one of the few climate reconstructions where both proxies are annually resolved, and is the first to integrate regional networks of geoduck chronologies and tree-ring chronologies.