Lateglacial and Holocene tephra markers from Icelandic source volcanoes have been identified in five sediment cores from the North Icelandic shelf and correlated with tephra layers in reference soil sections in North Iceland and the GRIP ice core. Land-sea correlation of tephra markers, that have been radiocarbon dated with terrestrial material or dated by documentary evidence, provides a tool for monitoring reservoir age variability in the region. Age models developed for the shelf sediments north of Iceland, based on offshore tephrochronology on one hand and on calibrated AMS 14C datings of marine molluscs on the other, display major deviations during the last 4500 years. The inferred temporal variability in the reservoir age of the regional water masses exceeds by far the variability expected from the marine model calculations. The observed reservoir ages are generally considerably higher, by up to 450 years, than the standard model ocean. It is postulated that the intervals with increased and variable marine reservoir age reflect incursions of Arctic water masses derived from the East Greenland Current to the Iceland Sea and the North Icelandic shelf.
Bibliographical noteFunding Information:
The present paper is a contribution to the two European Union 5th framework projects, HOLSMEER (Contract No. EVK2-CT-2000-00060) and PACLIVA (Contract No. ECK2-CT-2002-00143) as well as the PANIS project (Palaeoenvironments on the North Icelandic shelf). Core material was obtained from the BIOICE Cruise in 1995 and the MD9922 IMAGES Cruise in 1999. We are grateful to the Institut Paul-Emile Victor (IPEV) for the IMAGES coring operations onboard the Marion Dufresne. Scientific work was supported by grants from the Icelandic Research Council and the Danish Natural Science Research Council. We thank Ole Tumyr at the Geological Institute, University of Bergen, Norway, for assistance and discussions about microprobe analyses presented here.