36. Margin-Scale Sedimentation—Carbon Sequestration by Marine Geological Processes

The delivery of particulate organic carbon (POC) from continents to the ocean by rivers and its eventual burial in ocean sediments are critical processes in the global cycle of carbon.  Sequestration of POC in marine sediments is the major long-term sink of CO₂ on Earth and a net source of oxygen over millennial time scales. Among river basins, the combined small basins with high relief are now recognized to account for the majority of the global sediment flux to the ocean, and recent work suggests they contribute a similar fraction of the terrigenous POC flux.  Burial of POC offshore of small, mountainous rivers may also be more efficient than offshore of large rivers due to rapid deposition rates during flood events.  In spite of its potential global importance, a quantitative understanding of POC flux from small, mountainous rivers and its subsequent burial on ocean margins is lacking.

Research under this Opportunity is intended to correct this knowledge deficit by the investigation of the fundamental processes that control the magnitude, frequency and distribution of sediment and POC delivery/burial along the land-ocean continuum of mountainous coastal river systems.  Because more than 5,000 ‘small’ rivers with watershed areas <15,000 km2 drain into the coastal ocean, detailed sampling of all of these watersheds and margins is not possible.  As an alternative, the postdoctoral fellow would identify general principles that explain the burial and sequestration of POC from well-described small, mountainous rivers (for example, Eel, Santa Clara, Waipaoa, Waiapu, Fly, and Po Rivers), and upscale these processes to margin-length scales.  This would allow for a better understanding of carbon delivery and sequestration on the along margin-scales that are relevant to global carbon cycles.

The goal of this research is to evaluate the mechanisms and patterns (in space and time) of POC delivery and burial along the margin of the U.S. West Coast.  The proposed study area is a region with active tectonics and large POC and sediment fluxes, and it has been the focus of a number of well-documented source-to-sink studies (for example, Eel, Columbia and Santa Clara Rivers).  The postdoctoral fellow will develop innovative methods to upscale results from these single-river studies to the broader margin.  Specific methods may include–but are not limited to–development and synthesis of river and oceanographic observations and development of scaling relationships using numerical process models. The research results will provide important information for understanding the role of the U.S. West Coast margin on the global carbon cycle. 

The postdoctoral fellow will also have the opportunity to work with a multi-disciplinary research program funded by NSF that is actively investigating and measuring POC and sediment fluxes from U.S. West Coast rivers and sedimentation rates within and offshore of these river basins.   This research group consists of the two research advisors and the following investigators:  M. Goni (OSU), G. Pasternack (UCD), and J. Borgeld (HSU).  She/he will also be able to develop partnerships with researchers from the USGS,  academia, and other federal agencies (EPA, NOAA, NASA).  The postdoctoral researcher will be at the forefront of interdisciplinary research in the United States and will participate in significantly improving our understanding of the delivery of terrestrial carbon to the coastal ocean and its impact on the global carbon cycle.

Proposed Duty Station: Santa Cruz, CA; Corvallis, OR

Areas of Ph.D.: Geology, geochemistry

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Chemist

(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): Jon Warrick, (831) 427-4793, jwarrick@usgs.gov; Rob Wheatcroft, (Oregon State U), 541-737-3891, raw@coas.oregonstate.edu

Human Resources Office contact: Candace Azevedo, (916) 278-9393, caazevedo@usgs.gov

Summary of Opportunities