Coastal upwelling along the western Americas: Past, present, and future

A. van Geen
Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964
Phone: (914) 365 8644, Fax: (914) 365 8154, e-mail:


This page provides access to preliminary results from a coordinated program of surfzone water collection and analysis along the western coasts of Chile, Mexico, and the United States. Sampling started at the end of 1996 and is currently supported by the Inter-American Institute for Global Change Research (IAI), the US National Science Foundation, and the Climate Center of the Lamont-Doherty Earth Observatory. The short-term objective of the program is to provide an integrated picture of large-scale variations in the intensity of coastal upwelling in response to variations in alongshore winds over the Peru/Humboldt and California Current systems. The sampling strategy is based on the observations of van Geen et al. (1992) and van Geen and Husby (1996) near San Francisco Bay, California, showing that concentration of upwelling-sensitive tracers such as nutrients and the trace metal cadmium in surfzone water is determined mainly by large-scale wind-forcing rather than local processes. The long-term objective is to use this information to reconstruct past changes in wind patterns, and therefore climate, along the western Americas by inferring the past composition of nearshore waters from the composition of carbonate shells formed by foraminifera and mollusks. Shells formed by these organisms over the past 9000 years of the Holocene can be recovered from estuarine sediments and archeological middens. Either orbital changes in insolation or changes in the intensity of the El Niņo/Southern Oscillation could have significantly affected the intensity of coastal upwelling along the western Americas during the Holocene. A simple consideration of interhemispheric differences in the effect of these two agents of climate change suggests that it should be possible to distinguish their relative importance from paleo-upwelling reconstructions at a few carefully selected sites in both hemispheres. This information will, in turn, provide a useful test of general circulation models designed to predict the impact of future climate change along the western Americas.

Current participants

The longest available time series of surfzone salinity, nutrients, and cadmium started in 1991 at Pillar Point, California. This site is presently sampled periodically by Darcy Gordon from Stanford University. Samples are processed in the laboratory of Samuel Luoma at the US Geological Survey in Menlo Park, California. Two sampling sites on the open coast were added in 1994 at Trinidad Head, California, and Seven Devils Beach, Oregon. These samples are currently collected and processed by John Hill from Humboldt State University in Arcata, California, and by Chris Cziesla from the Oregon Institute of Marine Biology in Charleston, Oregon. Surface water has also been collected inside the mouths of San Francisco Bay, Humboldt Bay, and Coos Bay to determine how faithfully the composition of estuaries tracks the composition of nearshore water on the open coast. Renee Takesue, Michelle Large, Shad Baiz, Laura Verhegge, and Isaac Kaplan have also collected and processed surfzone samples from the US sites in the past. In late 1996, five students from Chile and Mexico started collected surfzone water at 10 new sites. Students participating in this program include Claudia Figueroa (advised by Marco Salamanca) from Universidad de Concepcion, Chile, Manuel Varas (Juan Carlos Castilla) from Pontificia Universidad Catolica de Chile, Santiago, Nury Guzman (Ruben Escribano/Luc Ortlieb) from Universidad de Antofagasta, Chile, Ernesto Vasquez (Lucio Godinez) from Centro Interdisciplinario de Ciencias Marinas, La Paz, Mexico, and Eduardo Ortiz (Jose Carriquiry) from Universidad Autonoma de Baja California, Ensenada, Mexico. Each of the Latin American students is funded by IAI to spend 4 months doing research at Lamont-Doherty which includes analysis of the samples that were collected. The first student, Manuel Varas, arrived in New York in January 1998.

The available data

Samples are collected periodically for salinity, nutrients phosphate, silicate, and nitrate, and Cd at each site. Cd is important for this project for two reasons. (1) Dissolved Cd is enriched in subsurface water offshore, just like the nutrient phosphate, but is taken up less rapidly by coastal phytoplankton. Cd measured in the surfzone is therefore a sensitive and nearly conservative indicator of coastal upwelling. (2) Cd incorporated in biogenic carbonate reflects the composition of ambient water during the life of the organism and can therefore be used to reconstruct past upwelling.
Line plots

Available results can be viewed with a software written by Benno Blumenthal from the Lamont-Doherty Earth Observatory. Click here to view sampling locations. Note that the data viewer allows you to zoom in on the different locations. Click here for a complete list of sampling locations and their latitude and longitude. Click here to view all the available data on a color scale for a specific tracer. You can also get a line plot of a time series for a selected tracer at a specific location (see table). The data viewer also allows you to overlay line plots for several stations. You can also obtain tables of the data for specific sites (see table).
Data Tables

Note that you can access many other ocean and climate data sets using the same viewer through the Lamont-Doherty Earth Observatory web page by clicking here.

Future developments

This web page will be updated periodically to provide the latest surfzone data in a convenient format to participants and other interested parties. A preliminary interpretation will be added in the near future. Current funding for surfzone sampling will run out at the end of 1998. I am actively looking for ways to extend surfzone sampling at all sites for at least another year in order to document the effect of the La Niņa, predicted to follow the present El Niņo (Webster and Palmer, 1997), on nearshore water chemistry.

Comments and suggestions regarding the surfzone sampling program or future paleo-upwelling reconstructions can be sent to


van Geen, A., S. N. Luoma, C. C. Fuller, R. Anima, H. E. Clifton, S. Trumbore, Evidence from Cd/Ca ratios in foraminifera for greater upwelling off California 4,000 years ago, Nature, 358, 54-56, 1992.

van Geen, A. and D. M. Husby, Cadmium in the California Current system: Tracer of past and present upwelling, J. Geophys. Res., 101, 3489-3507, 1996.

Webster, P. J., and T. N. Palmer, The past and the future of El Niņo, Nature, 390, 562-564, 1997.