16. Seasonal Moisture Source Variability for the Colorado River Basin during the Late Holocene from Lake and Marine Sediment Archives

The Upper and Lower Colorado River basins are supplied with moisture by two primary sources; winter snows and summer monsoon rains.  The net moisture balance for the region is a combination of seasonal precipitation and understanding the multi-annual to decadal atmospheric dynamics that result in long-term moisture decreases for the Colorado River Basin is of increasing interest.  Future climate predictions forecast decreased snowpack and earlier run-off that will further stress an already diminished water resource due to increasing demand. 

Microfossil and geochemical studies on cores from the central Gulf of California have revealed that the North American monsoon developed during the past ~6000 years when sea surface temperatures became warm enough to supply moisture (Barron et al., 2004).  Lake sediments and ice cores from North Pacific margins have documented winter atmospheric patterns of circulation around the Aleutian Low (Anderson et al., 2005) that may have varied with El Niño Southern Oscillation (ENSO) cycles.  Lake sediment cores from snowmelt-dominated alpine catchments in the Upper Colorado River Basin are well situated to document past snowpack variability.  However, linking marine and terrestrial sediment records from locations that record seasonal moisture transport to the northern and southern portions of the Colorado River Basin is necessary to discern and compare the spatial climate patterns of past severe droughts. 

This Research Opportunity is focused on the synthesis of lake and marine sediment records to improve understanding of late Holocene moisture-source variability and forcing.  This research will help to establish a paleoclimatic baseline by focusing on decade-to-century climate records of the last ~2000 to 6000 years, a period when large-scale climate boundary conditions, with the exception of anthropogenic CO2, were largely similar to those of today.

We are looking for new and innovative approaches from the complementary disciplines of paleoceanography and paleolimnology to address the difficult problem of distinguishing seasonal moisture from climate-proxy data.  This could include utilizing existing sediment records or by new field-based research but the emphasis should be on justifying a multi-proxy methodology and presenting a focused study plan that will propel our understanding of late Holocene seasonal moisture sources and drought. 

In addition to the wealth of paleoclimatic expertise and resources in the Denver-Boulder area within the USGS, NOAA, NCAR and the University of Colorado, successful candidates will also immediately benefit from ongoing USGS projects in Northern Arizona, within the core of the region affected by the North American monsoon [Late Quaternary Paleohydrologic history of the Mojave Desert Region and Climate Change, Land Use, and Environmental Sensitivity (CLUES)].   

References

Anderson, L., Abbott, M.B., Finney, B.P., and Burns, S.J.,  2005,  Regional atmospheric circulation change in the North Pacific during the Holocene inferred from lacustrine carbonate oxygen isotopes, Yukon Territory, Canada:  Quaternary Research, v. 64, p. 21–35.

Barron, J.A., Bukry, D., and Bischoff, J.L.,  2004, High resolution paleoceanography of the Guaymas Basin, Gulf of California, during the past 15,000 years: Marine Paleontology, v. 50, p. 185–207.

Proposed Duty Station: Denver, CO; Menlo Park, CA

Areas of Ph.D.: Geology, geochemistry, hydrology, oceanography, limnology, ecology

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Chemist, Research Oceanographer, Research Hydrologist, Environmental Scientist

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisor(s): ): Lesleigh Anderson, (303) 236-1296, land@usgs.gov; John Barron, (650) 329-4971, jbarron@usgs.gov

Human Resources Office contact: Vanessa Chambless, (303) 236-9584, vchambless@usgs.gov

Summary of Opportunities