An Orographic Conduit for Atlantic Forcing of Pacific Decadal Climate Variability


OCCI Funded Project: 2009


The tropical and subtropical Atlantic, Pacific, and Indian Ocean basins exhibit variability across a wide range of time scales. It is often theorized that modes of variability in one basin can influence the climate of adjacent ocean basins. Mechanisms for inter–basin connections on timescales distinct from the El Niño–Southern Oscillation (ENSO) have yet to be firmly established. The question of what mechanisms are responsible for decadal variability in the Pacific Ocean has come into focus, yet the potential role of inter–basin influences has yet to be considered. This project is based on the hypothesis that decadal variability in the North Atlantic can directly force decadal–scale variability in the tropical Pacific Ocean by way of modulating the strength of the wind jets flowing through the mountain gaps at the Isthmus of Tehuantepec in Mexico (“gap winds”). In essence, the Isthmus of Tehuantepec provides a direct orographic conduit for Atlantic forcing of Pacific decadal variability. In addition to the physical climate system, the resultant Atlantic–forced climate variability in the Pacific extends to the ocean ecosystem since the ocean dynamics invoked by the gap winds provide the vertical mixing and overturning necessary to maintain high productivity as seen in surface chlorophyll concentration.  This project synthesizes existing observational data and three–dimensional coupled climate model experiments to test the above hypothesis and explore a potentially exciting new inter–basin mechanism and contribute to the growing interest in understanding and predicting decadal climate variability.