Alexander, M. A., N.-C. Lau, and J. D. Scott, 2004: Broadening the atmospheric bridge paradigm: ENSO telecommunications to the tropical West Pacific-Indian Oceans over the seasonal cycle and to the North Pacific in summer. In Earth's Climate: The Ocean-Atmosphere Interaction, C. Wang, S.-P. Xie, and J. A Carton (Eds.), American Geophysical Union, 85-103.


ABSTRACT

During El Niño-Southern Oscillation (ENSO) events, atmospheric teleconnections associated with sea surface temperature (SST) anomalies in the equatorial Pacific can influence the ocean thousands of kilometers away. We use several data sets to delineate this "atmospheric bridge" between ocean basins, focusing on two emerging research areas: 1) the evolution of atmosphere-ocean interactions in the tropical Indian-Western Pacific Oceans over the full ENSO cycle and 2) the formation of large amplitude SST anomalies in North Pacific in the summer before ENSO peaks. In ENSO composites [where events peak near the end of Yr(0)], an east-west SST dipole develops in the Indian Ocean during the summer-fall of Yr(0), followed by basin-wide warming through spring of Yr(1). The SST anomalies over most of the tropical west Pacific also reverse sign, from negative in summer of Yr(0) to positive in the following summer. Local air-sea interactions influence the evolution of these ENSO-induced SST anomalies and related sea level pressure (SLP) and precipitation anomalies. Over the western North Pacific, the southward displacement of the jet stream and storm track in the summer of Yr(0) changes the solar radiation and latent heat flux at the surface, which results in anomalous cooling (and deepening) of the oceanic mixed layer at ~40°N. The potential impact of both the tropical and North Pacific SST anomalies on the broader climate is discussed.