A multi-century history of North Pacific SSTs from annual growth increments in the bivalve Panopea generosa

Abstract:

We present a highly-replicated, annually-resolved, multi-centennial reconstruction of North Pacific sea surface temperatures (SSTs) from Pacific geoduck (Panopea generosa) growth increment widths at Langara Island, British Columbia, Canada. We extend a live-collected chronology spanning CE 1764-2003 and append three radiocarbon-dated floating chronologies covering additional 136-, 107-, and 129- year intervals within the last ~1200 years. The reconstruction explains 56% of the variance in the instrumental record (1941-2002), and shows significant relationships to basin-scale variability (1900-2002). The reconstruction is characterized by strong autocorrelation with significant, but unstable, power spectra periodicities ranging from 10 to 60 years. Interdecadal variability in the 19^th century is unusually quiescent relative to other portions of the reconstruction. The 20^th century is defined by an abrupt regime shift in 1976 to uniquely warm and variable temperatures relative to any period of similar length in the 650-year reconstruction. The marked instability of low-frequency variability over time suggests that SSTs in the region may be better described by a red noise model than a quasi-periodic oscillating mode.