A NEAR MILLENNIUM-LONG RECORD OF ANNUAL SUMMER SEAWATER TEMPERATURE CHANGES FROM THE NORTH ICELANDIC SHELF: CLIMATE PERSPECTIVES FROM A CONTINUOUS, MULTI-CENTURY, MASTER SHELL CHRONOLOGY

Here we provide seawater temperature data for the north Icelandic shelf waters during the last millennium based on annually-banded molluscs. The detrended and normalized master shell growth record has been calibrated and validated (RE = 0.61, CE = 0.42) with a nearby instrumental series (AD 1947-2005), which allows us to estimate past summer seawater temperatures at 75 m water depth with a mean squared error of ± 0.6 °C. The master shell growth chronology is based on long-lived bivalves (Arctica islandica L.), which were live-caught in 2006 in a relatively shallow shelf setting (80 m) near the island of Grimsey. Using the dendrochronological technique of cross-dating, we have successfully linked dead-collected A. islandica shells with the modern master chronology and established a continuous shell-based chronology for much of the last millennium. Nearby proxy-SST records, derived from sediment archives, and our new seawater temperature record are in good agreement. Due to the annual nature of the shell-based seawater temperature record, we have been able to hindcast high-frequency extreme climate events, which appear to be similar to the great salinity anomaly (GSA)/cold period of the 1960s. Extremely narrow annual growth increments (or cold periods) were most frequent in the 18^th, 15^th, 17^th, and 19^th centuries, respectively. The ocean climate north of Iceland was highly variable during the Little Ice Age (ca. AD 1300 – 1850), with substantial warm intervals imbedded in the relatively cold period. These data are currently being used to score and constrain regional climate model runs.