Drought or Deluge? Columbia River flows to the North Pacific under a variable Holocene climate.

Oregon State University, Corvallis OR

Investigators

Abstract

Drought or Deluge? Columbia River flows to the North Pacific under a variable Holocene Climate The discharge of the Columbia River broadly reflects the water supply of the Pacific Northwest region. Little is known about the long-term influence on climate variability on this water supply prior to the 20th century, leading to uncertainty surrounding the impacts of the currently warming climate on regional water rights, agricultural production, and fisheries. This research aims to reconstruct the natural variability in river discharge via chemical and biotic measures of past surface salinity preserved in marine sedimentary layers accumulating off the Columbia River mouth, and to place that river discharge variability into the climatologic context of the past ~12,000 years, a time that spans intervals of both warmer and cooler climate than today. By investigating the relationship between climate variability and discharge of this major river system in the past, this research will contribute to a better understanding of what is likely in the future. This project leverages a new suite of sediment cores recently collected via two seagoing research expeditions to the continental slope off the Columbia River, well suited for reconstructions of Holocene climate and river discharge. The sites bracket the offshore Columbia River low salinity plume in its winter and summer extents. The study will analyze fossil plankton shells for oxygen isotopes, barium:calcium and magnesium:calcium ratios, the species abundances of marine foraminiferal plankton and both marine and freshwater diatoms to reconstruct sea-surface temperatures and sea-surface salinity (related to discharge). Analysis of multiple species of known seasonal succession will allow for investigation of seasonality and intermittency of discharge. These data will address a hypothesis that higher temperatures in the NE Pacific are associated with inland drought, relative to an alternate hypothesis that warmer ocean temperature drive higher net precipitation (snow and rain) through an increase in atmospheric moisture. The highly resolved independent chronology of this reconstruction will place PNW hydroclimate and NE Pacific temperature variability into a global temporal framework, improving our understanding of large-scale regional climate dynamics in a part of the world poorly constrained by data and models. Results of this study will advance fundamental understanding of regional-scale dynamic sensitivity of climate and will yield practical knowledge about potential future water supplies of value for long-term planning. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.