Planktonic Foraminifera of the California Current Reflect 20th-Century Warming
David B. Field,1*
Timothy R. Baumgartner,2
Christopher D. Charles,1
Vicente Ferreira-Bartrina,2
Mark D. Ohman1
It is currently unclear whether observed pelagic ecosystem responses to ocean warming, such as a mid-1970s change in the eastern North Pacific, depart from typical ocean variability. We report variations in planktonic foraminifera from varved sediments off southern California spanning the past 1400 years. Increasing abundances of tropical/subtropical species throughout the 20th century reflect a warming trend superimposed on decadal-scale fluctuations. Decreasing abundances of temperate/subpolar species in the late 20th century indicate a deep, penetrative warming not observed in previous centuries. These results imply that 20th-century warming, apparently anthropogenic, has already affected lower trophic levels of the California Current.
1 Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
2 Centro de Investigación Científica y de Educación Superior de Ensenada, Km 107 Carretera Tijuana-Ensenada, Ensenada, Baja California, C.P. 22860, Mexico.
* Present address: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA.
To whom correspondence should be addressed. E-mail: dfield{at}mbari.org
