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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2017-71
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model description paper
06 Jun 2017
Review status
This discussion paper is a preprint. A revision of the manuscript was accepted for the journal Geoscientific Model Development (GMD).
Impacts of microtopographic snow-redistribution and lateral subsurface processes on hydrologic and thermal states in an Arctic polygonal ground ecosystem
Gautam Bisht1, William J. Riley1, Haruko M. Wainwright1, Baptiste Dafflon1, Yuan Fengming2, and Vladimir E. Romanovsky3 1Climate & Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
2Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6301 , USA
3Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
Abstract. Microtopographic features, such as polygonal ground, are characteristic sources of landscape heterogeneity in the Alaskan Arctic coastal plain. Here, we analyze the effects of snow redistribution (SR) and lateral subsurface processes on hydrologic and thermal states at a polygonal tundra site near Barrow, Alaska. We extended the land model integrated in the ACME Earth System Model (ESM) to redistribute incoming snow by accounting for microtopography and incorporated subsurface lateral transport of water and energy (ALMv0-3D). Three 10-years long simulations were performed for a transect across polygonal tundra landscape at the Barrow Environmental Observatory in Alaska to isolate the impact of SR and subsurface process representation. When SR was included, model results show a better agreement (higher R2 with lower bias and RMSE) for the observed differences in snow depth between polygonal rims and centers. The model was also able to accurately reproduce observed soil temperature vertical profiles in the polygon rims and centers (overall bias, RMSE, and R2 of 0.59 °C, 1.82 °C, and 0.99, respectively). The spatial heterogeneity of snow depth during the winter due to SR generated surface soil temperature heterogeneity that propagated in depth and time and led to ~10 cm shallower and ~5 cm deeper maximum annual thaw depths under the polygon rims and centers, respectively. Additionally, SR led to spatial heterogeneity in surface energy fluxes and soil moisture during the summer. Excluding lateral subsurface hydrologic and thermal processes led to small effects on mean states but an overestimation of spatial variability in soil moisture and soil temperature as subsurface liquid pressure and thermal gradients were artificially prevented from spatially dissipating over time. The effect of lateral subsurface processes on active layer depths was modest with mean absolute difference of ~3 cm. Our integration of three-dimensional subsurface hydrologic and thermal subsurface dynamics in the ACME land model will facilitate a wide range of analyses heretofore impossible in an ESM context.

Citation: Bisht, G., Riley, W. J., Wainwright, H. M., Dafflon, B., Fengming, Y., and Romanovsky, V. E.: Impacts of microtopographic snow-redistribution and lateral subsurface processes on hydrologic and thermal states in an Arctic polygonal ground ecosystem, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-71, in review, 2017.
Gautam Bisht et al.
Gautam Bisht et al.
Gautam Bisht et al.

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Short summary
The land model integrated in the ACME Earth System Model (ESM) was extended to include snow redistribution (SR) and lateral subsurface hydrologic and thermal processes. Simulation results at a polygonal tundra site near Barrow, Alaska showed inclusion of SR resulted in a better agreement with observations. Excluding lateral subsurface processes had a small impact on mean states but a large overestimation of spatial variability in soil moisture and temperature.
The land model integrated in the ACME Earth System Model (ESM) was extended to include snow...
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