3914 JOURNAL OF CLIMATE VOLUME 21 Influences of Atlantic Climate Change on the Tropical Pacific via the Central American Isthmus*

• Main Authors: Shang-ping Xie, Axel Timmermann
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2007
• Subjects: Pacific; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.145.1331; http://iprc.soest.hawaii.edu/~xie/iroam-hosing-08.pdf

Recent global coupled model experiments suggest that the atmospheric bridge across Central America is a key conduit for Atlantic climate change to affect the tropical Pacific. A high-resolution regional ocean– atmosphere model (ROAM) of the eastern tropical Pacific is used to investigate key processes of this conduit by examining the response to a sea surface temperature (SST) cooling over the North Atlantic. The Atlantic cooling increases sea level pressure, driving northeasterly wind anomalies across the Isthmus of Panama year-round. While the atmospheric response is most pronounced during boreal summer/fall when the tropical North Atlantic is warm and conducive to deep convection, the Pacific SST response is strongest in winter/spring when the climatological northeast trade winds prevail across the isthmus. During winter, the northeasterly cross-isthmus winds intensify in response to the Atlantic cooling, reducing the SST in the Gulf of Panama by cold and dry advection from the Atlantic and by enhancing surface turbulent heat flux and mixing. This Gulf of Panama cooling reaches the equator and is amplified by the Bjerknes feedback during boreal spring. The equatorial anomalies of SST and zonal winds dissipate quickly in early summer as the seasonal development of the cold tongue increases the stratification of the atmospheric boundary layer and shields the surface from the Atlantic influence that propagates into the Pacific as tropospheric Rossby