Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing
The overall spatial and temporal influence of shrub expansion on permafrost is largely unknown due to uncertainty in estimating the magnitude of many counteracting processes. For example, shrubs shade the ground during the snow-free season, which can reduce active layer thickness. At the same time,...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Canadian Science Publishing
2019-12-01
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| Series: | Arctic Science |
| Subjects: | |
| Online Access: | https://doi.org/10.1139/as-2018-0028 |
| _version_ | 1819129604402577408 |
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| author | Evan J. Wilcox Dawn Keim Tyler de Jong Branden Walker Oliver Sonnentag Anastasia E. Sniderhan Philip Mann Philip Marsh |
| author_facet | Evan J. Wilcox Dawn Keim Tyler de Jong Branden Walker Oliver Sonnentag Anastasia E. Sniderhan Philip Mann Philip Marsh |
| author_sort | Evan J. Wilcox |
| collection | DOAJ |
| description | The overall spatial and temporal influence of shrub expansion on permafrost is largely unknown due to uncertainty in estimating the magnitude of many counteracting processes. For example, shrubs shade the ground during the snow-free season, which can reduce active layer thickness. At the same time, shrubs advance the timing of snowmelt when they protrude through the snow surface, thereby exposing the active layer to thawing earlier in spring. Here, we compare 3056 in situ frost table depth measurements split between mineral earth hummocks and organic inter-hummock zones across four dominant shrub–tundra vegetation types. Snow-free date, snow depth, hummock development, topography, and vegetation cover were compared to frost table depth measurements using a structural equation modeling approach that quantifies the direct and combined interacting influence of these variables. Areas of birch shrubs became snow free earlier regardless of snow depth or hillslope aspect because they protruded through the snow surface, leading to deeper hummock frost table depths. Projected increases in shrub height and extent combined with projected decreases in snowfall would lead to increased shrub protrusion across the Arctic, potentially deepening the active layer in areas where shrub protrusion advances the snow-free date. |
| first_indexed | 2024-12-22T08:46:21Z |
| format | Article |
| id | doaj.art-6190640b9e724fb48b5ae30830ebc9d2 |
| institution | Directory Open Access Journal |
| issn | 2368-7460 |
| language | English |
| last_indexed | 2024-12-22T08:46:21Z |
| publishDate | 2019-12-01 |
| publisher | Canadian Science Publishing |
| record_format | Article |
| series | Arctic Science |
| spelling | doaj.art-6190640b9e724fb48b5ae30830ebc9d22022-12-21T18:32:06ZengCanadian Science PublishingArctic Science2368-74602019-12-015420221710.1139/as-2018-0028Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timingEvan J. Wilcox0Dawn Keim1Tyler de Jong2Branden Walker3Oliver Sonnentag4Anastasia E. Sniderhan5Philip Mann6Philip Marsh7Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK S7N 3H5, Canada.School of Geography and Earth Science, McMaster University, Hamilton, ON L8S 4K1, Canada.Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.Département de Géographie & Centre d’Études Nordiques, Université de Montréal, Montréal, QC H2V 2B8, Canada.Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.The overall spatial and temporal influence of shrub expansion on permafrost is largely unknown due to uncertainty in estimating the magnitude of many counteracting processes. For example, shrubs shade the ground during the snow-free season, which can reduce active layer thickness. At the same time, shrubs advance the timing of snowmelt when they protrude through the snow surface, thereby exposing the active layer to thawing earlier in spring. Here, we compare 3056 in situ frost table depth measurements split between mineral earth hummocks and organic inter-hummock zones across four dominant shrub–tundra vegetation types. Snow-free date, snow depth, hummock development, topography, and vegetation cover were compared to frost table depth measurements using a structural equation modeling approach that quantifies the direct and combined interacting influence of these variables. Areas of birch shrubs became snow free earlier regardless of snow depth or hillslope aspect because they protruded through the snow surface, leading to deeper hummock frost table depths. Projected increases in shrub height and extent combined with projected decreases in snowfall would lead to increased shrub protrusion across the Arctic, potentially deepening the active layer in areas where shrub protrusion advances the snow-free date.https://doi.org/10.1139/as-2018-0028frost tableactive layershrubssnowmelthummocks |
| spellingShingle | Evan J. Wilcox Dawn Keim Tyler de Jong Branden Walker Oliver Sonnentag Anastasia E. Sniderhan Philip Mann Philip Marsh Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing Arctic Science frost table active layer shrubs snowmelt hummocks |
| title | Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing |
| title_full | Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing |
| title_fullStr | Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing |
| title_full_unstemmed | Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing |
| title_short | Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing |
| title_sort | tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing |
| topic | frost table active layer shrubs snowmelt hummocks |
| url | https://doi.org/10.1139/as-2018-0028 |
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