Northeast Pacific Surface Ocean Response to Millennial Scale Climate Variability
N.G. Pisias A.C. Mix, (College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis OR 97331; ph. 541-737- 5213; Internet: firstname.lastname@example.org); L. Heusser (Lamont Doherty Earth Observatory, Palisades NY)
Analysis of radiolarian microfossils, stable isotopes and pollen in sediment cores from the continental margin off Northern California and Oregon provide records of surface ocean variability on millennial time scales during the last 100,000 years. Radiolarian based sea surface temperature estimates suggest temperature variability of on the order of 2oC. In these coastal waters these temperatures changes reflect both changes in California Current advection and eastern boundary upwelling. Radiolarian species changes reflect both processes. The variability in coastal upwelling in the region is highly correlated with ice core records from Greenland (weaker upwelling during stadial events) suggesting that at least part of the response to Heinrich scale events in the Northeast Pacific in coastal upwelling related to changes in atmospheric circulation patterns.
Pollen extract from these marine sediment cores provide the opportunity to directly compare the climate response of continental systems with the oceanographic record. Detailed statistical analysis shows a very high degree of correlation between the continental and marine records. The first variate identified in a canonical correlation analysis shows the pollen and radiolarian species abundances has a correlation coefficient of 0.94. This canonical variate correlates a combination of radiolarian species associated with coastal upwelling with a combination of redwood and coastal hemlock pollen, with high upwelling being correlated with increased redwood and hemlock pollen. This correlation is reasonable since coastal redwood forests depend on fog, which is associated with summer upwelling. The strong degree of correlation between the marine and continental record on these time scales suggest that the response time of these two systems to climate change is on the same order.
One important caveat with interpretation of marine pollen records with climate is the issue of how differing transport processes might influence the pollen record. If transport changes from different provenances, then the pollen record would not necessarily reflect changes in continental climate. In these cores the pollen record is not correlated with the changing abundance of terrigenous material. On going sediment provenance studies will hopefully provide a method to separate the climate component of the marine pollen record versus changes in transport mechanisms.