Preprints
https://doi.org/10.5194/tc-2021-60
https://doi.org/10.5194/tc-2021-60

  07 Apr 2021

07 Apr 2021

Review status: this preprint is currently under review for the journal TC.

Impact of lateral groundwater flow on hydrothermal conditions of the active layer in a high arctic hillslope setting

Alexandra Hamm1,2 and Andrew Frampton1,2 Alexandra Hamm and Andrew Frampton
  • 1Department of Physical Geography, Stockholm University, Stockholm, Sweden
  • 2Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

Abstract. Modeling the physical state of permafrost landscapes is a crucial addition to field observations in order to understand its feedback mechanisms within a warming climate. A common hypothesis in permafrost modeling is that vertical heat conduction is most relevant to derive subsurface temperatures. While this approach is mostly applicable to flat landscapes with little topography, landscapes with more topography are subject to lateral flow process as well. With our study, we want to contribute to the growing body of evidence that lateral surface- and subsurface processes can have a significant impact on permafrost temperatures and active layer properties. We use a numerical model to simulated two idealized hillslopes with inclinations that can be found in Adventdalen, Svalbard, and compare them to a flat control case. We find that ground temperatures within the active layer uphill are generally warmer than downhill in both slopes (up to ~1.2 °C in the steep, and ~0.7 °C in the medium slope). Further, the slopes are found to be warmer in the uphill section and colder in the very bottom of the slopes compared to the flat control case. As a result, maximum thaw depth increases by about 5 cm from the flat (75 cm) to the steep slope (80 cm), while the medium case does not exhibit a deepening in thaw depth (75 cm). Uphill warming on the slopes is explained by additional energy gain through infiltration and lower evaporation rates due to a overall drier environment. The major governing process causing the cooling on the downslope side is heat loss to the atmosphere through evaporation in summer and enhanced heat loss in winter due to wetter conditions and resulting higher thermal conductivity. On a catchment scale, these results suggest that temperature distributions in hilly terrain can vary considerably compared to flat terrain, which might change the response of subsurface hydrothermal conditions to ongoing climate change.

Alexandra Hamm and Andrew Frampton

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-60', Anonymous Referee #1, 22 Apr 2021
    • AC1: 'Reply on RC1', Alexandra Hamm, 09 Jun 2021
  • RC2: 'Comment on tc-2021-60', Anonymous Referee #2, 24 Apr 2021
    • AC2: 'Reply on RC2', Alexandra Hamm, 09 Jun 2021

Alexandra Hamm and Andrew Frampton

Alexandra Hamm and Andrew Frampton

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Short summary
To investigate the effect of groundwater flow on the active layer on slopes in permafrost landscapes, we conducted several modeling experiments. We find that groundwater moving downslope in the subsurface causes areas downhill to be colder than uphill. This effect is explained by increased evaporation downhill and higher heat advection uphill. Therefore, in a changing climate, higher soil moisture could have a cooling effect on the active layer and attenuate warming from higher air temperatures.