NOAA/WDS Paleoclimatology - North Icelandic Shelf 1350 Year Molusc Radiocarbon Data

STUDY NOTES: Radiocarbon content of shells of the long-lived marine bivalve Arctica islandica collected on the North Icelandic shelf. The shells were absolutely dated using crossdating techniques derived from dendrochronology, and provide a 1350-year record of water mass migration and strength of the Atlantic meridional overturning circulation. Shells were collected near the island of Grimsey, North Icelandic Shelf, at a water depth of 81-83 m from the RV Bjarni Saemundsson (Cruise No. B05-2006, trawl B05AD03). Trawl B05AD03: 66°31.59'N, 18°11.74'W, ~82m water depth.
ABSTRACT SUPPLIED BY ORIGINATOR: Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.