A 1,000-year ice core record of interannual to multidecadal variations in atmospheric circulation over the North Atlantic
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Interannual to multidecadal modes in ocean/atmosphere dynamics in the North Atlantic region have been identified using sea salt aerosol proxy records from northern Greenland ice cores over the last 1,000 years. Sea salt concentrations show a consistent relationship with anomalies in the meridional pressure gradient over the North Atlantic region over all considered time scales. These pressure anomalies are connected to shifts in storm tracks, leading to lower pressure and higher storm activity, hence, higher sea salt export over the Greenland ice sheet. Two modes of long-term variability with a period of 10.4 years and 62 years could be identified. The latter is connected to long-term changes in sea surface temperature (SST) as documented by a high correlation of North Atlantic SST with our sea salt record over the last 150 years. Long-term reconstruction of these modes shows that the 10.4-year cycle has been a phenomenon persistent over the last millennium while the 62-year cycle has been mainly active after 1700. Accordingly, the longer-term persistence of this multidecadal variability in sea salt points also to significant variations in SST over the last 300 years.
KeywordsNorth Atlantic Oscillation North Atlantic Oscillation Index North Atlantic Region Positive North Atlantic Oscillation Phase Dansgaard Oeschger
This is a contribution to the research strategy project “Natural climate variations from 10,000 to the present” (KIHZ) by the Helmholtz association of German research centers, funded by the German Ministry for Education and Research and in part of the EU project “Patterns of Climate Variability in the North Atlantic” (PACLIVA). We especially thank G. Lohmann for fruitful discussions and comments on this work and the PACLIVA ice core team on helpful comments. NCEP reanalysis data were kindly provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA (at http://www.cdc.noaa.gov/).
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