Talk in honor of Gerard Bond

Response of Norwegian Sea Surface and Air Temperature to Solar Forcing; A Tribute to the “Persistence” of Gerard Bond

Scott J. Lehman [scott.lehman@colorado.edu], University of Colorado, Boulder; H.P. Sejrup and H. Haflidason, University of Bergen, Norway; R. Muscheler, National Center for Atmospheric Research, Boulder, Colorado; J. Andrews, University of Colorado, Boulder.

            Previous studies of eastern Norwegian Sea sediment cores by Berstad et. al. (2003) document a strong relationship between 18O variation in the summer surface dwelling planktonic foraminifera Neogloboquadrina pachyderma (dextral form) and the instrumental record of nearby coastal and island summer air temperature back to ~1870 AD. Here we present an improved chronology (from 210Pb, 137Cs, historic ashes and high precision AMS dating) and increased sampling resolution (from 2-3 years in the 1900’s to 10 years older than 1700 AD) for ~7000 years of record in two cores from the Berstad et al. site. The isotopic results show a strong negative (i.e. positive temperature) correspondence with peaks in Group Sun Spot Number back to ~1600 AD and with solar activity as reconstructed from 14C variations (Muscheler et al.,  in press) back to 1300 AD. For the longer part of the record, we compare the 500 -1800 year band pass components of 18O variation, 14C production, and estimated 10Be flux. A strong positive correlation between the temperature and solar proxies supports the evidence of Gerard Bond and others (2001) for a persistent sun-climate connection in this band. Taken together, these observations document a response of Norwegian Sea surface and air temperature to solar forcing on timescales of decades to millennia. Comparison of our isotopic results to those from Florida Strait and Greenland indicates Atlantic-wide coherence of the climate signal, at least for correlative features of more than a few hundred years duration. This suggests a possible interaction with the thermohaline circulation, and a climate signature similar to that of the Atlantic Multi-Decadal Oscillation.