Atmospheric circulation changes in the tropical Pacific inferred from the voyages of the Manila galleons in the sixteenth-eighteenth centuries

©2001 American Meteorological Society. The authors wish to thank Mr. Cruz Apestegui for advice on the design and sailing characteristics of the Manila galleons, and Drs. A. K. Smith, W. Randel, P. Gent, and A. Kaplan for their comments on the original manuscript. Valuable comments were also provided by two anonymous reviewers. This work was supported in part by a Small Grant for Exploratory Research from the Earth System History (ESH) Program of the National Science Foundation (NSF); the support and encouragement of former ESH Director Dr. Howard Zimmerman is gratefully acknowledged. The National Center for Atmospheric Research is sponsored by NSF.
Historical accounts of the voyages of the Manila galleons derived from the Archivo General de Indias (General Archive of the Indies, Seville, Spain) are used to infer past changes in the atmospheric circulation of the tropical Pacific Ocean. It is shown that the length of the voyage between Acapulco, Mexico, and the Philippine Islands during the period 1590-1750 exhibits large secular trends, such that voyages in the middle of the seventeenth century are some 40% longer than those at the beginning or at the end of the century, and that these trends are unlikely to have been caused by societal or technological factors. Analysis of a series of "virtual voyages," constructed from modem wind data,,indicates that sailing time to the Philippines depended critically on the strength of the trade winds and the position of the western Pacific monsoon trough. These results suggest that the atmospheric circulation of the western Pacific underwent large, multidecadal fluctuations during the seventeenth century.
National Science Foundation (NSF), EE.UU.
Depto. de Física de la Tierra y Astrofísica
Fac. de Ciencias Físicas
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