19 Jun 2023
 | 19 Jun 2023

Snowmelt-mediated isotopic homogenization of shallow till soil

Filip Muhic, Pertti Ala-Aho, Matthias Sprenger, Björn Klöve, and Hannu Marttila

Abstract. The hydrological cycle of sub-arctic areas is dominated by the snowmelt event. Understanding the mechanisms that control water fluxes during high-volume infiltration events in sub-arctic till soils is needed to assess how future changes in the timing and magnitude of snowmelt can affect soil water storage dynamics. We conducted a tracer experiment with deuterated water to irrigate a plot on a forested hilltop in Lapland, tracked water fluxes of different mobility and monitored how the later snowmelt modifies the labelled soil water storage. We used lysimeters and destructive soil coring for soil water sampling, and monitored and sampled the groundwater. Surface water flow during the tracer experiment was largely controlled by fill-and-spill mechanism. We found that labelled water remained in deeper soil layers over the winter, but the snowmelt event gradually displaced all deuterated water and fully homogenized all water fluxes at the soil-vegetation interface. The conditions required for the full displacement of the old soil water occur only during snowmelt with a persistently high groundwater table. We propose a conceptual model where infiltration into the soil, and eventual soil water replenishment, occurs in three stages. First, unsaturated macropore flow is initiated via surface microtopography and is directed towards the groundwater storage. The second stage is characterized by groundwater level rise through the macropore network, and subsequent pore water saturation and horizontal connectivity of macropores. Shallow subsurface lateral fluxes develop in more permeable shallow soil layers. In the third stage, which materializes during a long period of a high groundwater table and high hydrological connectivity within the soil, the soil water is replenished via enhanced matrix flow and pore-water exchange with the macropore network.

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Filip Muhic, Pertti Ala-Aho, Matthias Sprenger, Björn Klöve, and Hannu Marttila

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-884', Anonymous Referee #1, 22 Jul 2023
    • AC1: 'Reply on RC1 and RC2', Filip Muhic, 12 Sep 2023
  • RC2: 'Comment on egusphere-2023-884', Anonymous Referee #2, 08 Aug 2023
    • AC2: 'Reply on RC2 and RC1', Filip Muhic, 12 Sep 2023
Filip Muhic, Pertti Ala-Aho, Matthias Sprenger, Björn Klöve, and Hannu Marttila
Filip Muhic, Pertti Ala-Aho, Matthias Sprenger, Björn Klöve, and Hannu Marttila


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Short summary
Snowmelt event governs the hydrological cycle of sub-arctic areas. In this study, we conducted a tracer experiment on a forested hilltop in Lapland, to identify how high-volume infiltration events modify the soil water storage. We found that a strong tracer signal remained in deeper soil layers after the experiment and over the winter, but it got fully displaced during the snowmelt. We propose a conceptual infiltration model that explains how the snowmelt homogenizes the soil water storage.