The California Current System (CCS) is a setting where several recent studies, focusing on the mechanisms and effects of glacial/interglacial climate change in North America and the North Pacific Ocean, employ the unsaturation patterns of alkenone biomarkers as a proxy for mean annual sea surface temperature (SST). However, the CCS is also a setting where dramatic changes in upwelling are known to occur in response to the very climate variation that these SST proxy records are employed to reconstruct. Knowing that the seasonal and depth distribution of phytoplankton, including alkenone producers, can depend heavily on the nutrient regime, what ramifications might this fact hold for interpretation of down core alkenone based SST records along the California margin? The investigators at Oregon State University hypothesize that changes in upwelling behavior and nutrient input along the northeast Pacific margin during glacial periods have shaped the SST proxy record and, thus, the research community's current understanding of how North Pacific climate responds to external forcing.
The investigators will measure alkenone unsaturation patterns and hydrogen isotopic composition in sediments from the modern northeast Pacific margin to track the effects of nutrient stress on the alkenone signal exported to the sea floor. Measurements will then be made on sediments from the same region at the last glacial maximum, as well as with roughly 4,000-year resolution at three representative sites through the last full glacial cycle. Through comparison of latitudinal trends in the results, the investigators will test their hypothesis that significant shifts occurred in the pattern of alkenone production through the glacial history of the CCS. If demonstrated, paleotemperature records from this region can be re-evaluated with the benefit of this improved ecological context. Current conceptions of the relationship between North Pacific climate and CCS strength, drawn from these fossil signatures, may be refined.
This project is best summarized as an effort to resolve important open questions surrounding the mechanisms and timing of North American/North Pacific climate change while simultaneously evaluating the utility of a powerful new tracer of paleo ecology. Fundamental understanding of these relationships is of direct importance as the scientific community attempts to determine the significance of recent anomalous CCS upwelling seasons and their ties to the currently changing atmospheric conditions in the North Pacific. Funding will support an advanced graduate student who has been centrally involved in developing the ideas upon which this research project is based.
