NEW MILLENNIAL-LENGTH PACIFIC/NORTH AMERICAN (PNA) TELECONNECTION PATTERN PROXY RECONSTRUCTION FROM NEW ENGLAND REVEALS PRESENT ANOMALOUS STATE

The Pacific/North American (PNA) teleconnection pattern forces winter/spring hydroclimate variability over North America by controlling the amplitude of the sup-polar jet stream. Instrumental PNA time-series cover fewer than six decades (1949-Present), however, which makes it difficult to fully understand the natural variability of the phenomenon. Here we present a proxy reconstruction of the PNA pattern based on compaction-corrected varve lamina thicknesses from the Pettaquamscutt River Estuary, RI, in order to expand our understanding of PNA variability over the last millennium. In New England, positive PNA conditions (meridional atmospheric flow) lead to more precipitation due to the associated dominance of moist Gulf of Mexico and Atlantic coastal air masses. Dry periods are associated with dry continental air masses that become dominant during negative PNA conditions (zonal flow). Regression of the two time-series during the period of instrumental overlap illustrate that lamina thicknesses explain 49% of the decadal PNA variability and over 30% of the interannual PNA variability, with confidence levels over 99%. The resulting PNA reconstruction demonstrates that the last four to five decades have had anomalously high PNA values as compared to the last millennium. The Little Ice Age was a time of a prolonged negative state, while the Medieval Warm Period displays much variability and a mean state intermediate between that of the Little Ice Age and Present Warm Period. The dominant periodic components of the time-series are in the 8- and 3-year ranges, and amplitudes of these and other cycles were smaller during the Little Ice Age negative PNA period as compared to the Medieval and Present Warm Periods. This conclusion of recent anomalously high PNA values suggests that water resource planning based on historical weather data may misrepresent natural hydroclimate variability, which is especially important to consider in drought-sensitive regions.