41. Understanding the Physical Properties and Dynamics of Permafrost: An Important Link Among Changes in Climate, Hydrology, and the Ecology of Northern High Latitudes

Recent permafrost degradation in the arctic and subarctic is widespread and expected to continue in response to climate warming. Resulting changes in hydrology and ecology have already been observed (Hinzman and others, 2005). These include drying lakes, thermokarst development, and vegetation shifts. Increased groundwater discharge to large streams has also been detected that may impact oceanic exports of carbon and nitrogen (Walvoord and Striegl, 2007). Connections between the above changes and permafrost thaw are likely, yet in many cases, solid evidence for these links is lacking, as is a fundamental understanding of the coupled processes involved over a broad range of scales. In addition, the physical properties of permafrost and the mechanics of growth and degradation remain poorly defined. In light of our changing climate, there is a pressing need for basic studies that provide these necessary pieces for assessing basin responses to shifting permafrost distributions.

Advancing our understanding of permafrost characterization and the coupled processes involved in growth and melting of ground ice will supply information that is critical, yet currently deficient, for projecting hydrologic and ecosystem responses to climate change in northern watersheds. Multiple opportunities exist for permafrost hydrology research in the northern high latitudes, for example in Russia (W. Siberia) and Canada, and particularly in Alaska as a complement to ongoing USGS Yukon River Basin Studies (http://ak.water.usgs. gov/yukon/). Studies may have field, laboratory, and/or numerical modeling components. Potential laboratory studies might, for example, address the physics of freezing porous media (temperature and pressure dependencies of ice/liquid content and permeability), and the mechanics of a collapsing soil matrix in thermokarst terrain.  Field studies are limited to areas where existing programs are in place, such as the Yukon River Basin, and could include permafrost manipulation studies, geochemical sampling to evaluate groundwater flow paths, and application or development of innovative shallow geophysical techniques for structural and hydraulic characterization of permafrost.  Modeling efforts integrated with laboratory and/or field studies to improve understanding of processes are encouraged. Alternatively, the focus may be primarily on modeling that makes use of existing data or that is theoretical (i.e. the impact of hydrogeologic heterogeneity on thaw patterns and thermokarst development). Coupling models of surface and subsurface water and energy balance processes would be useful for generating climate-scenario simulations to evaluate hydrologic responses of seasonal and long-term changes in the subsurface thermal regime of permafrost]dominated watersheds. Modeling efforts could be aimed to guide future field investigations by identifying regions where hydrologic changes in response to rising global temperatures are expected to be most dramatic.

A research-version of the USGS SUTRA code (Voss and Provost, 2003) that enables the simulation of freezing and thawing of permafrost (SUTRA-ICE) is available for groundwater-flow and energy-transport modeling in arctic and subarctic regions (that is, McKenzie and others, 2007). SUTRA-ICE may be coupled with surface energy balance, solute transport, streamflow routing, and/or deformable mesh capabilities in order to simulate dynamic hydrological processes in permafrost-dominated watersheds. 

A research laboratory is available for investigation of water flow processes in saturated and unsaturated porous materials under temperature-controlled conditions. Equipment includes: a specially-modified centrifuge for measuring variably-saturated hydraulic properties, operable at temperatures down to -20°C; various additional state-of- the-art instruments for hydraulic property measurement; a porous-media flow visualization system; development facilities for new lab and field instruments to observe and measure water flow in soils; and support equipment including laser-scattering particle-size analysis.

References

Hinzman, L., and others, 2005, Evidence and implications of recent climate change in Northern Alaska and other Arctic regions: Climatic Change, v. 72, p. 25 1–298.

McKenzie, J., Voss, C.I., and Siegel, D., 2007, Groundwater flow with energy transport and water-ice phase change: Numerical simulations, benchmarks, and application to freezing in peat bogs: Advances in Water Resources, v. 30, p. 966–983.

Voss, C. I., and Provost, A.M., 2003, SUTRA, A model for saturated-unsaturated variable-density ground-water flow with solute or energy transport: U.S.Geological Survey Water Resources Investigation 02–4231, 250 p.

Walvoord, M.A., and Striegl, R.G., 2007, Increased groundwater to stream discharge from permafrost thawing in the Yukon River basin: Potential impacts on lateral export of carbon and nitrogen: Geophysical Research Letters, v. 34, p. L12402.

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

Areas of Ph.D.: Hydrology, physics, soil science, geochemistry, geology, geophysics

Qualifications: Applicants must meet one of the following qualifications: Research Hydrologist, Research Physicist, Soil Scientist, Research Chemist, Research Geologist, Research Geophysicist

(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): Michelle Walvoord, (303) 236-4998,  walvoord@usgs.gov; Clifford Voss, (703) 648-5274, cvoss@usgs.gov; John Nimmo, (650) 329-4537, jrnimmo@usgs.gov

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

Summary of Opportunities