Publication: A shift in the wind regime of the southern end of the Canary upwelling system at the turn of the 20th century
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Amer Geophysical Union
In this study, we make use of historical wind direction observations to assemble an instrumental upwelling index (DUI) at the southern end of the Canary Current Upwelling System. The DUI covers the period between 1825 and 2014 and, unlike other upwelling indices, it does not rely neither in wind speed nor in reanalyzed data. In this sense, the DUI can be regarded as an instrumental index. Additionally, it avoids the suspected bias toward increasing wind speed of historical wind observations documented in previous research. Our results indicate that the frequency of the alongshore winds at the west coast of Africa between 10°N and 20°N measured by the DUI is significantly related with the wind stress and therefore the upwelling intensity in this region. The DUI presents a significant variability both at interannual and decadal timescales. We have not found any significant trend for the 20th century. However, when the entire length of the series is considered, a large shift toward more frequent alongshore winds is evidenced as a result of several decade-long fluctuations which took place between the late 19th century and the beginning of the 20th century. This fact would imply that a significant change in the upwelling intensity at the southern end of the Canary Current Upwelling System should have occurred at the turn of the 20th century.
© 2021. The Authors. Esther González did intensive work at the UK National Archives abstracting logbooks. The research was funded by the Spanish Ministerio de Economía y Competitividad under grant CGL2015-72164-EXP (UPNAO). Support for the 20th Century Reanalysis Project version 3 data set is provided by the U.S. Department of Energy, Office of Science Biological and Environmental Research (BER), by the National Oceanic and Atmospheric Administration Climate Program Office, and by the NOAA Physical Sciences Laboratory. Funding for open access publishing: Universidad Pablo de Olavide/CBUA.