RESEARCH HIGHLIGHT

Northern Alaska Connections II: Soil Moisture Measurement and Modeling

January 3, 2008

The North Slope region of Alaska is home to abundant wildlife and Iñupiat Eskimos and has become one of the largest oil producing areas in the nation.  It is also a region especially sensitive to changes in climate. Environmental monitoring and research has become of primary importance for this area because in the Arctic, climate change is amplified, directly affecting human communities and activities, and the ecology of the region.   The International Arctic Research Center has become increasingly involved in research on the North Slope to help assess and understand specific environmental changes.  We are partnering with a number of other institutions and our researchers are investigating a wide variety of issues including wetland hydrology, biochemical feedbacks, precipitation, sea-ice trends, severe weather activity, and terrestrial carbon balance.  We also conduct summer schools and community based transformative education/outreach efforts across northern Alaska. 

This is the second in a series of research highlights on IARC research and educational efforts in Northern Alaska.  Our focus today is on soil moisture field research and modeling.

The Northern Alaska Coastal System and North Slope regions have extensive wetlands, despite near desert precipitation levels. This is an energy-limited system, where evapotranspiration* is highly dependent on incoming solar radiation and relatively impermeable permafrost reduces sub-surface water storage capacity in the flat landscape. 

Climate models predict a warming of the Arctic region in the future with thawing of the permafrost. Depending on the soil moisture condition, large amounts of CO₂ or the 20 times stronger greenhouse gas CH₄ is released to the atmosphere when permafrost thaws, as 20 to 30% of the global terrestrial carbon is stored in the permafrost soils. A deeper thaw induced by climate change, can therefore lead to a positive feedback on a global scale.

The North Slope region could experience drastic future changes in near-surface soil moisture. In permafrost regions, snowmelt and rainfall infiltration into soil is limited to the active layer, the ground above the permafrost that experiences seasonal freezing and thawing, because of the ice-rich permafrost below. As the future active layer thickens, water is able to drain away from the surface, and these changes will likely affect local ecosystems and economies. Due to the several hundred meter thick permafrost, residents of Alaska’s North Slope region are dependent on surface waters for all their needs. Many birds migrate to the tundra in spring to feed. Fires are expected to be more common as the near-surface dries. 

Anna Liljedahl, a research assistant at IARC, is working on a project that combines measurements and modeling to study the hydrological regime on a watershed scale. Soil moisture is of particular interest, especially for future scenarios. The study requires an exchange of data between snow, soil thermal regime, vegetation, and hydrology models. Liljedahl is also collecting field measurements to test the accuracy of geographical representations in model simulations.

Liljedahl hopes to answer these questions with her research: What is the present spatial and temporal distribution of soil moisture in several scales across the polygon and drained thaw lake landscape? How will the future (end of 21st century) soil moisture distribution look like? What are the major processes behind a possible future change in soil moisture distribution? (Changes in vegetation, hydraulic gradients, storage capacity of soil etc.)  How does the physically based hydrological model TopoFlow perform on this landscape?

The project is a part of the Study of Northern Alaska Coastal System (SNACS), under a subgroup called Carbon Interconnections.  Liljedahl plans to collaborate with other researchers who are studying carbon fluxes by providing future scenarios of thaw and soil moisture conditions.

* The process of transferring moisture from the earth to the atmosphere by evaporation of water and transpiration from plants.

References:

A. Liljedahl, L. Hinzman, Y. Harazono, 2008. The role of meteorological variables on arctic wetland evapotranspiration. American Water Resources Association Alaska Section 2008 Annual Meeting, January 28-31, Juneau, AK

A. Liljedahl, L. Hinzman, 2008. TopoFlow soil moisture simulations and validation. American Water Resources Association Alaska Section 2008 Annual Meeting, January 28-31, Juneau, AK

A. Liljedahl, L. Hinzman, Y. Harazono and D. Zona, 2007. Dependence of evapotranspiration on meteorological variables, Barrow, Northern Alaska, POSTER U41C-0622 2007 American Geophysical Union Fall Meeting, December 10-14, 2007, San Francisco, CA

A. Liljedahl, L. Hinzman, 2006. Historic and future spatial hydrologic variations at a coastal Arctic watershed, Alaska, POSTER C51B-0416. 2006 American Geophysical Union Fall Meeting, December 11-15, 2006, San Francisco, CA

Photos:

Anna and Bob installing soil moisture sensors, Barrow Environmental Observatory.

Installation of liquid water content reflectometer and a single measurement of soil thermal properties.