Long-Term Variations of the North Atlantic Oscillation

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Abstract ATM-9615678 Stockton, Charles W. University of Arizona Title: Long-Term Variations of the North Atlantic Oscillation This award supports a research project designed to use tree-ring data from Morocco, appropriate tree-ring data from western Europe and eastern North America, sea ice extent records, and indices from the GISP2 Greenland ice cores to provide a 1000 year reconstructed record of variability of the North Atlantic Oscillation (NAO). Previous investigations have shown that the cool season large scale alternations of atmospheric mass between the North Atlantic regions of subtropical high pressure and subpolar low pressure are highly correlated with precipitation in Morocco. Because Morocco is physically located at the southern extremity of the NAO system, slight perturbations in the system are recorded in the Moroccan precipitation records. The tree rings record variations in the state of the NAO through the changing direction of associated atmospheric moisture transport. Three-ring data from western Europe and eastern North America, as well as Greenland ice core data and regional sea ice extent also show a high degree of response to the state of the NAO, and thus, can be used to assess the more northern extremity of the oscillation. The tree-ring construction of the NAO index will place recent NAO trends in a long-term perspective. Of particular interest is comparison of the recent NAO trend with NAO variations during the Little Ice Age and other periods of climate extreme. A final product of the project will be a long-term synoptic climatology showing various states of the NAO along with their associated North Atlantic synoptic weather conditions and North Atlantic SST anomaly fields.