ESRL/PSD Seminar Series

Abstract

The three leading modes of Pacific sea surface temperature (SST) variability, El Niño ­ Southern Oscillation (ENSO), Pacific Decadal Variability (PDV) and the long­term change in Pacific SST (LT), individually force hemispheric teleconnections that result in changes to the precipitation and water resources over North America and Western Asia. While the three leading Pacific SST modes are individually impactful, their synchronous phasing can result in SST expressions that force intense and prolonged changes to the atmospheric circulation and precipitation throughout the Northern Hemisphere. The recent and persistent SST expression associated with the phasing of La Niña, negative PDV and a warm west Pacific Ocean resulting form LT, forces severe hemispheric drought in models and observations. Its mirror expression, El Niño, positive PDV and a cool west Pacific Ocean associated with LT, forces immense pluvials throughout the Northern Hemisphere; however, this SST expression no longer occurs because of a continuously warming west Pacific Ocean. Therefore, SST­forced hemispheric pluvials are becoming less intense while SST­forced droughts are becoming more intense. This work has implications for seasonal to decadal predictability, particularly over food and water insecure regions.