December 01, 2020

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Efficient Dynamic Inundation Model for Ice Wedge Polygons

Improved understanding of polygonal tundra landscape drainage by understanding individual polygon drainage.

Schematic diagram of our three-dimensional axisymmetric analytical model of inundated low-centered polygon drainage. The diagram represents an idealized “pie wedge” section of a low-centered polygon, including pools in the center and trough.
[Image Credit: Reprinted from Zlotnik, V. A., D. R. Harp, E. E. Jafarov, C. J. Abolt, C.J. “A model of ice wedge polygon drainage in changing Arctic terrain.” Water 12(12), 3376 (2020). DOI:10.3390/w12123376]

The Science

The timing and flow patterns of ice-wedge polygon drainage have important hydrological, ecological, biogeochemical, and thermal implications for polygon tundra landscapes. Understanding the basic hydrological unit of polygonal tundra landscapes (the single polygon) is key to understanding the overall drainage of these landscapes. To this end, the researchers have developed an efficient model of inundated ice-wedge polygon drainage based on fundamental hydrologic first-principles.

The Impact

The model has been validated against a 22-day polygon drainage event at the Barrow Environmental Observatory. The model simulates the drainage event in under 5 seconds on a 3.1 GHz processor and requires no external libraries, making the model amenable to inclusion in Earth system models.

Summary

As ice wedge degradation and the inundation of polygonal troughs become increasingly common processes across the Arctic, lateral export of water from polygonal soils may represent an important mechanism for the mobilization of dissolved organic carbon and other solutes. However, drainage from ice wedge polygons is poorly understood. The researchers constructed a model which uses cross-sectional flow nets to define flow paths of meltwater through the active layer of an inundated low-centered polygon towards the trough. The model includes the effects of evaporation and simulates the depletion of ponded water in the polygon center during the thaw season. In most simulations, the team discovered a strong hydrodynamic edge effect: only a small fraction of the polygon volume near the rim area is flushed by the drainage at relatively high velocities, suggesting that nearly all advective transport of solutes, heat, and soil particles is confined to this zone. Estimates of characteristic drainage times from the polygon center are consistent with published field observations.

Principal Investigator

Dylan Harp
Los Alamos National Laboratory
dharp@lanl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

This research has been supported by the Office of Biological and Environmental Research in the DOE Office of Science (NGEE-Arctic) in collaboration with Dr. Vitaly Zlotnik of the University of Nebraska-Lincoln.

References

Zlotnik, V. A., D. R. Harp, E. E. Jafarov, C. J. Abolt. "A model of ice wedge polygon drainage in changing Arctic terrain". Water 12 (12), 3376   (2020). https://doi.org/10.3390/w12123376.