85th AMS Annual Meeting

Tuesday, 11 January 2005: 9:00 AM
Impacts of Global Modes of Climate Variability on Regional Coastal Systems
John M. Wallace, JISAO/Univ. of Washington, Seattle, WA
The structure and behavior of a prescribed pattern or 'mode' of climate variability can be represented in terms of maps representing its spatial pattern in fields like sea level pressure, together with a single time varying index representing its amplitude and polarity. Although the climate literature abounds with modes of variability, just a few of them are of interdisciplinary interest, the most important and best known of which is the El Nino - Southern Oscillation (ENSO) phenomenon. A closely related (but not identical) mode is the Pacific-North American (PNA) pattern, the atmospheric signature of the so called "Pacific Decadal Oscillation". Another major player is a pattern variously known as the North Atlantic Oscillation, the Arctic Oscillation, and the Northern Hemisphere annular mode. ENSO, the PNA pattern and the annular modes are the only modes of climate variability for which there exists some degree of seasonal to interannual predictability. Together these modes account for virtually all the global climate trends of the past 50 years during the boreal winter and they are believed to play an important role in the variability on paleoclimatic time scales as well. These modes have pronounced effects on marine coastal ecosystems, as evidenced by the strong correspondence between their indices and various indicators of the state of the ecosystem. High resolution satellite imagery is beginning to show how these modes perturb coastal winds and chlorophyll concentrations.

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