Explicitly modelling microtopography in permafrost landscapes in a land surface model (JULES vn5.4_microtopography)
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Explicitly modelling microtopography in permafrost landscapes in a land surface model (JULES vn5.4_microtopography). / Smith, Noah D.; Burke, Eleanor J.; Aas, Kjetil Schanke; Althuizen, Inge H. J.; Boike, Julia; Christiansen, Casper Tai; Etzelmüller, Bernd; Friborg, Thomas; Lee, Hanna; Rumbold, Heather; Turton, Rachael H.; Westermann, Sebastian; Chadburn, Sarah E.
In: Geoscientific Model Development, Vol. 15, No. 9, 2022, p. 3603-3639.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Explicitly modelling microtopography in permafrost landscapes in a land surface model (JULES vn5.4_microtopography)
AU - Smith, Noah D.
AU - Burke, Eleanor J.
AU - Aas, Kjetil Schanke
AU - Althuizen, Inge H. J.
AU - Boike, Julia
AU - Christiansen, Casper Tai
AU - Etzelmüller, Bernd
AU - Friborg, Thomas
AU - Lee, Hanna
AU - Rumbold, Heather
AU - Turton, Rachael H.
AU - Westermann, Sebastian
AU - Chadburn, Sarah E.
N1 - CENPERMOA[2022] Publisher Copyright: © 2022 Noah D. Smith et al.
PY - 2022
Y1 - 2022
N2 - Microtopography can be a key driver of heterogeneity in the ground thermal and hydrological regime of permafrost landscapes. In turn, this heterogeneity can influence plant communities, methane fluxes, and the initiation of abrupt thaw processes. Here we have implemented a two-tile representation of microtopography in JULES (the Joint UK Land Environment Simulator), where tiles are representative of repeating patterns of elevation difference. Tiles are coupled by lateral flows of water, heat, and redistribution of snow, and a surface water store is added to represent ponding. Simulations are performed of two Siberian polygon sites, (Samoylov and Kytalyk) and two Scandinavian palsa sites (Stordalen and Iškoras). The model represents the observed differences between greater snow depth in hollows vs. raised areas well. The model also improves soil moisture for hollows vs. the non-tiled configuration ("standard JULES") though the raised tile remains drier than observed. The modelled differences in snow depths and soil moisture between tiles result in the lower tile soil temperatures being warmer for palsa sites, as in reality. However, when comparing the soil temperatures for July at 20ĝ€¯cm depth, the difference in temperature between tiles, or "temperature splitting", is smaller than observed (3.2 vs. 5.5ĝ€¯ĝ C). Polygons display small (0.2ĝ€¯ĝ C) to zero temperature splitting, in agreement with observations. Consequently, methane fluxes are near identical (+0ĝ€¯% to 9ĝ€¯%) to those for standard JULES for polygons, although they can be greater than standard JULES for palsa sites (+10ĝ€¯% to 49ĝ€¯%). Through a sensitivity analysis we quantify the relative importance of model processes with respect to soil moisture and temperatures, identifying which parameters result in the greatest uncertainty in modelled temperature. Varying the palsa elevation between 0.5 and 3ĝ€¯m has little effect on modelled soil temperatures, showing that using only two tiles can still be a valid representation of sites with a range of palsa elevations. Mire saturation is heavily dependent on landscape-scale drainage. Lateral conductive fluxes, while small, reduce the temperature splitting by ĝ1/4ĝ€¯1ĝ€¯ĝ C and correspond to the order of observed lateral degradation rates in peat plateau regions, indicating possible application in an area-based thaw model.
AB - Microtopography can be a key driver of heterogeneity in the ground thermal and hydrological regime of permafrost landscapes. In turn, this heterogeneity can influence plant communities, methane fluxes, and the initiation of abrupt thaw processes. Here we have implemented a two-tile representation of microtopography in JULES (the Joint UK Land Environment Simulator), where tiles are representative of repeating patterns of elevation difference. Tiles are coupled by lateral flows of water, heat, and redistribution of snow, and a surface water store is added to represent ponding. Simulations are performed of two Siberian polygon sites, (Samoylov and Kytalyk) and two Scandinavian palsa sites (Stordalen and Iškoras). The model represents the observed differences between greater snow depth in hollows vs. raised areas well. The model also improves soil moisture for hollows vs. the non-tiled configuration ("standard JULES") though the raised tile remains drier than observed. The modelled differences in snow depths and soil moisture between tiles result in the lower tile soil temperatures being warmer for palsa sites, as in reality. However, when comparing the soil temperatures for July at 20ĝ€¯cm depth, the difference in temperature between tiles, or "temperature splitting", is smaller than observed (3.2 vs. 5.5ĝ€¯ĝ C). Polygons display small (0.2ĝ€¯ĝ C) to zero temperature splitting, in agreement with observations. Consequently, methane fluxes are near identical (+0ĝ€¯% to 9ĝ€¯%) to those for standard JULES for polygons, although they can be greater than standard JULES for palsa sites (+10ĝ€¯% to 49ĝ€¯%). Through a sensitivity analysis we quantify the relative importance of model processes with respect to soil moisture and temperatures, identifying which parameters result in the greatest uncertainty in modelled temperature. Varying the palsa elevation between 0.5 and 3ĝ€¯m has little effect on modelled soil temperatures, showing that using only two tiles can still be a valid representation of sites with a range of palsa elevations. Mire saturation is heavily dependent on landscape-scale drainage. Lateral conductive fluxes, while small, reduce the temperature splitting by ĝ1/4ĝ€¯1ĝ€¯ĝ C and correspond to the order of observed lateral degradation rates in peat plateau regions, indicating possible application in an area-based thaw model.
U2 - 10.5194/gmd-15-3603-2022
DO - 10.5194/gmd-15-3603-2022
M3 - Journal article
AN - SCOPUS:85129821161
VL - 15
SP - 3603
EP - 3639
JO - Geoscientific Model Development
JF - Geoscientific Model Development
SN - 1991-959X
IS - 9
ER -
ID: 307365120