HR: 14:00h
AN: GC52A-02    [PDF]
TI: The Atlantic Basin as a Source for North American Drought: New Perspectives from Proxy Climate Networks
AU: * Gray, S T
EM: sgray@montana.edu
AF: Big Sky Institute-Montana State University, 106 AJM Johnson Hall, Bozeman, MT 59717 United States
AU: Graumlich, L J
EM: lisa@montana.edu
AF: Big Sky Institute-Montana State University, 106 AJM Johnson Hall, Bozeman, MT 59717 United States
AU: Betancourt, J L
EM: jlbetanc@usgs.gov
AF: Desert Laboratory U.S. Geological Survey and University of Arizona, 1675 West Anklam Road, Tucson, AZ 85745 United States
AB: Investigations into the causes of severe, persistent droughts in North America have focused primarily on interannual (ENSO) to decadal-scale (PDO) variability in Pacific sea surface temperatures (SST). This, in turn, has justified rapid development of high-resolution proxies to extend Pacific SST fields beyond the instrumental record. However, recent studies show that low-frequency (30-70 yr) modes in North Atlantic ($0-70\deg$ N) SST, the so-called Atlantic Multidecadal Oscillation (AMO), may influence long-term summer moisture trends and modulate Pacific teleconnections over North America. To examine this linkage, we compare a new, tree-ring based proxy for the AMO (A.D. 1567-1991) with gridded reconstructions of drought (1700-1978) and hydroclimatic variability (late 1500s-Present) across North America. Our AMO reconstruction, which includes 13 tree-ring chronologies from Eastern North America, Western Europe, Scandinavia and the Middle East, captures both interannual (r = 0.78) and decadal-scale (10 yr) variability (r = 0.94) in observed SST over the North Atlantic Basin. Reconstructed AMO is significantly correlated with reconstructed drought frequency and intensity throughout North America, particularly in the central and southern Rockies and western Great Plains. This is not only true for the interval of the gridded PDSI reconstructions (1700-1978), but also for a suite of proxy records from the Western US that overlap with the complete AMO reconstruction. Specifically, the late-16$^{th}$ and mid-20$^{th}$ Century (1930s and 1950s) "megadroughts", as well as current drought in the Western US, occurred during strong, persistent warm phases of the AMO. In addition, wet spells in the early 17$^{th}$, 19$^{th}$ and 20$^{th}$ centuries correspond with cool regimes in North Atlantic SST. The coherency of drought events across major river basins and climatic regions of the Western US also increases when warm phases of the AMO coincide with cool phases of the PDO. Overall, these analyses demonstrate the potential for using Atlantic SSTs to understand drought variability throughout North America, and the need to reevaluate Pacific-North American teleconnections in light of larger-scale SST fluctuations.
DE: 1620 Climate dynamics (3309)
DE: 1635 Oceans (4203)
DE: 1812 Drought
DE: 1833 Hydroclimatology
DE: 3344 Paleoclimatology
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting