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ASSOCIATIONS BETWEEN NAO VARIBILITY AND U.S. MID-ATLANTIC REGION HYDROCLIMATOLOGY
Citation:
Walker, H A., B. Yarnal, AND R. Najjar. ASSOCIATIONS BETWEEN NAO VARIBILITY AND U.S. MID-ATLANTIC REGION HYDROCLIMATOLOGY. Presented at Chapman Conference on the North Atlantic Oscillation, Galicia, Spain, November 28, 2000.
Description:
Variability in the climate of the US Mid-Atlantic Region is associated with larger scale variability in the El Nino-Southern Oscillation (ENSO), the Pacific North American (PNA) teleconnection pattern, and the North Atlantic Oscillation (NAO). Collectively, these three large-scale modes of variability may affect storm frequency and tracking over the region. We focused on associations relating a multiproxy reconstruction of variations in the NAO with variability in the water balance of the Susquehanna River Basin, with the interannual variability of freshwater influx into Chesapeake Bay, and with drought. Using data from the past 100 years, it is apparent that negative NAO index phases are associated with cooler and dryer conditions over the Susquehanna River Basin. USGS data for the past 50 years show that fresh water influx into Chesapeake Bay matches the multiproxy NAO index variations. We based an analysis of spatial and temporal components of variance in Mid-Atlantic Region drought over the past 300 years on an ordination and spectral analysis of four tree-ring-based drought indices representing a north-south transect through the region. The resulting orthogonal components of variance are coherent with the dominant modes of NAO variability and characterize variation in three climatic features: overall moisture flux into the region; north-south variability in regional drought; and subtle components of variance in the 60 to 100-year band. The last of these three climatic features may relate to fluctuations in the intensity of thermohaline circulation in the North Atlantic. Our results indicate that variability in North Atlantic atmospheric and oceanic circulation may be associated with climate regime shifts in the US Mid-Atlantic Region and with occasional periods of severe drought that are evident in the Mid-Atlantic Region paleo-record.