Abstract
The presence of permafrost influences the flow paths of water through Arctic landscapes and thereby has the potential to impact stream discharge and thermal regimes. Observations from 11 headwater streams in Alaska showed that July water temperatures were higher in catchments with more near-surface permafrost. We apply a fully coupled cryohydrology model to investigate if the impact of permafrost on flow path depth could cause the same pattern in temperatures of groundwater discharging from hillslopes to streams. The model simulates surface energy and water balances, snow, and subsurface water and energy balances for two-dimensional hillslope model cases with varying permafrost extent. We find that hillslopes with continuous permafrost have more shallow flow paths and twice as high rates of evapotranspiration, compared to hillslopes with no permafrost. For our simulated cases, 6.7% of the horizontal water flux moves through the top organic soil layers when there is continuous permafrost, while only 0.5% moves through organic layers without permafrost. The deeper flow paths in permafrost-free simulations buffer seasonal temperature extremes, so that summer groundwater discharge temperatures are highest with continuous permafrost. Our results suggest that permafrost thawing alters groundwater flow paths and can lead to decreases in summer stream temperatures and reductions in evapotranspiration in headwater catchments. These changes are of potential importance for stream biotic components of ecosystems, however, the full impact remains unknown.
| Original language | English |
|---|---|
| Article number | e2020WR027463 |
| Journal | Water Resources Research |
| Volume | 57 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 2021 |
Funding
This research was funded by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas) grant number 2015‐00790 (Y. Sjöberg), and supported by the Changing Arctic Ecosystems Initiative of the Wildlife program of the U.S. Geological Survey Ecosystems Mission Area, and the National Park Service's Arctic Inventory and Monitoring Network and staff from the Western Arctic Parklands in Kotzebue, Alaska. Oak Ridge National Laboratory's contribution to this work was supported by the Next‐Generation Ecosystem Experiment—Arctic (NGEE‐Arctic) project. The NGEE‐Arctic project is supported by the Office of Biological and Environmental Research in the U.S. Department of Energy's Office of Science. The simulations were performed on resources at Chalmers Centre for Computational Science and Engineering (C3SE) provided by the Swedish National Infrastructure for Computing (SNIC). For calculations of incoming solar radiation, based on latitude and day of year, a script by Felix Hebeler (available at https://www.mathworks.com/matlabcentral/fileexchange/19791-solar-radiation ) was modified for the site conditions and study purposes. Meteorological data collection was supported by the Arctic Land Conservation Cooperative. All analyses of soil samples were conducted by the laboratory at Daniel B. Stephens & Associates, Inc. This manuscript benefitted greatly from reviews by Marty Briggs, Sean Carey, two anonymous reviewers, the USGS Office of Science Quality and Integrity, as well as the guidance from Associate Editor Dan Moore. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. This research was funded by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas) grant number 2015-00790 (Y. Sj?berg), and supported by the Changing Arctic Ecosystems Initiative of the Wildlife program of the U.S. Geological Survey Ecosystems Mission Area, and the National Park Service's Arctic Inventory and Monitoring Network and staff from the Western Arctic Parklands in Kotzebue, Alaska. Oak Ridge National Laboratory's contribution to this work was supported by the Next-Generation Ecosystem Experiment?Arctic (NGEE-Arctic) project. The NGEE-Arctic project is supported by the Office of Biological and Environmental Research in the U.S. Department of Energy's Office of Science. The simulations were performed on resources at Chalmers Centre for Computational Science and Engineering (C3SE) provided by the Swedish National Infrastructure for Computing (SNIC). For calculations of incoming solar radiation, based on latitude and day of year, a script by Felix Hebeler (available at https://www.mathworks.com/matlabcentral/fileexchange/19791-solar-radiation) was modified for the site conditions and study purposes. Meteorological data collection was supported by the Arctic Land Conservation Cooperative. All analyses of soil samples were conducted by the laboratory at Daniel B. Stephens & Associates, Inc. This manuscript benefitted greatly from reviews by Marty Briggs, Sean Carey, two anonymous reviewers, the USGS Office of Science Quality and Integrity, as well as the guidance from Associate Editor Dan Moore. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Keywords
- hillslope hydrology
- modeling
- permafrost
- stream temperatures