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Abstract This study integrated spatially distributed field observations and soil thermal models to constrain the impact of frozen ground on snowmelt partitioning and streamflow generation in an alpine catchment within the Niwot Ridge Long‐Term Ecological Research site, Colorado, USA. The study area was comprised of two contrasting hillslopes with notable differences in topography, snow depth and plant community composition. Time‐lapse electrical resistivity surveys and soil thermal models enabled extension of discrete soil moisture and temperature measurements to incorporate landscape variability at scales and depths not possible with point measurements alone. Specifically, heterogenous snowpack thickness (~0–4 m) and soil volumetric water content between hillslopes (~0.1–0.45) strongly influenced the depths of seasonal frost, and the antecedent soil moisture available to form pore ice prior to freezing. Variable frost depths and antecedent soil moisture conditions were expected to create a patchwork of differing snowmelt infiltration rates and flowpaths. However, spikes in soil temperature and volumetric water content, as well as decreases in subsurface electrical resistivity revealed snowmelt infiltration across both hillslopes that coincided with initial decreases in snow water equivalent and early increases in streamflow. Soil temperature, soil moisture and electrical resistivity data from both wet and dry hillslopes showed that initial increases in streamflow occurred prior to deep soil water flux. Temporal lags between snowmelt infiltration and deeper percolation suggested that the lateral movement of water through the unsaturated zone was an important driver of early streamflow generation. These findings provide the type of process‐based information needed to bridge gaps in scale and populate physically based cryohydrologic models to investigate subsurface hydrology and biogeochemical transport in soils that freeze seasonally.
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This content will become publicly available on June 30, 2026
Projections of Permafrost and Seasonally Frozen Ground Along an Elevation Gradient at Niwot Ridge, Colorado, USA
ABSTRACT The intensity, duration, and spatial distribution of frozen soil influences hydrologic flow paths, soil biogeochemistry, and slope geomorphology. In cold regions, where the ground thermal regime is controlled by the seasonal snowpack, representation of the snowpack in models simulating seasonally frozen ground is required and leads to significant improvements in soil temperature estimates. With long‐term climate and ground temperature observations, Niwot Ridge, a seasonally snow‐covered alpine catchment in the headwaters of the Boulder Creek watershed, serves as an ideal location for analyzing frozen ground under a changing climate. In this study, we use a coupled thermo‐hydrologic model to provide novel perspectives on cryosphere research at Niwot Ridge. We project how end‐of‐21st‐century changes in Front Range air temperature, snowfall, and snowpack cold content will influence the ground thermal regime, including seasonally frozen ground and permafrost, in comparison to the 1952–1970 period. In projections of seasonally frozen ground, the model predicts two additional months of unfrozen soils by the end of the 21st century compared with the 1952–1970 time period, which is expected to lead to an increase in the number of days favorable for microbial respiration. Our permafrost analysis supports the occurrence of permafrost above 3800 m with active layer thickness 1.8 m (1952–1970), 2.2 m (2001–2013), and 38 m by end of 21st century. The simulated deep soil thaw over the last several decades (1970–2020) is small compared with projected deep soil thaw through the current century, which is expected to lead to reductions in frost cracking.
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- Award ID(s):
- 1331828
- PAR ID:
- 10614863
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Permafrost and Periglacial Processes
- ISSN:
- 1045-6740
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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