Title: Mathematical Modelling of Arctic Polygonal Tundra with Ecosys : 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

Abstract

Microtopographic variation that develops among features (troughs, rims, and centers) within polygon al landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. In this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snow and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R 2  = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALDmore » was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.« less

Authors:

Grant, R. F. ^[1]; Mekonnen, Z. A. ^[2]; Riley, W. J. ^[2]; Wainwright, H. M. ^[2]; Graham, D.  ^[3];

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Torn, M. S. ^[2]

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+ Show Author Affiliations

1. Univ. of Alberta, Edmonton, AB (Canada). Dept. of Renewable Resources
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Science Division
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division

Publication Date:

Fri Nov 17 00:00:00 EST 2017

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1427642

Alternate Identifier(s):

OSTI ID: 1433101

Grant/Contract Number:  

AC05-00OR22725; AC02‐05CH11231; AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Biogeosciences

Additional Journal Information:

Journal Volume: 122; Journal Issue: 12; Journal ID: ISSN 2169-8953

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; active layer depth; ecosys; ecosystem modeling; arctic tundra; microtopography