Jeanne DeMeo, Pitzer College

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Abstract:

The earth’s natural climate variability fluctuates on a large range of time scales. The impact of anthropogenic greenhouse gas emissions on specific patterns of climate variability is a subject of current research. The North Atlantic Oscillation (NAO) is one such pattern of climate variability. The NAO is the dominant wintertime atmospheric pressure pattern in the Atlantic region and is hypothesized to be connected to other climate system features such as Atlantic Multidecadal Variability (AMV) or Atlantic Meridional Overturning Circulation (AMOC) which describe sea surface temperature changes, and deep ocean circulation changes respectively. Measurements of the NAO extend into the 1800s, and many reconstructions using paleoclimate proxy data have been created to extend that instrumental record back in time. To assess the fidelity of these reconstructions, this study analyzed existing reconstructions using a spearman's correlation, coefficient of efficiency, and a root mean squared error. The results indicated that the Cook et al. (2019), Luterbacher et al. (2001), and Michel et al. (2020) performed better than other NAO reconstructions when compared to three different indices of historical NAO patterns. The exact ranking of each reconstruction depended on the exact metric and comparison dataset, reflecting the different calibration targets of individual studies as well as the strengths and weaknesses of different approaches.