Preprints
https://doi.org/10.5194/egusphere-2024-350
https://doi.org/10.5194/egusphere-2024-350
15 Feb 2024
 | 15 Feb 2024
Status: this preprint is open for discussion.

High-resolution 4D ERT monitoring of recently deglaciated sediments undergoing freeze-thaw transitions in the High Arctic

Mihai O. Cimpoiasu, Oliver Kuras, Harry Harrison, Paul B. Wilkinson, Philip Meldrum, Jonathan E. Chambers, Dane Liljestrand, Carlos Oroza, Steven K. Schmidt, Pacifica Sommers, Lara Vimercati, Trevor P. Irons, Zhou Lyu, Adam Solon, and James A. Bradley

Abstract. Arctic regions are under immense pressure from a continuously warming climate. Understanding the physical mechanisms and processes that determine soil liquid moisture availability contributes to the way we conceptualize and understand the development and functioning of terrestrial Arctic ecosystems. However, harsh weather and logistical constraints limit opportunities to directly observe subsurface processes year-round, hence automated and uninterrupted strategies of monitoring soil physicochemical properties are essential. Geoelectrical monitoring using electrical resistivity tomography (ERT) has proven to be an effective method to capture soil moisture distribution in time and space. ERT instrumentation has been adapted for year-round operation in high- latitude weather conditions. We installed two geoelectrical monitoring stations on the forefield of a retreating glacier on Svalbard, consisting of semi-permanent surface ERT arrays and co-located soil sensors, which track seasonal changes in 3D of soil electrical resistivity, moisture and temperature. One of the stations observes recently exposed sediments (5–10 years since deglaciation), whilst the other covers more established sediments (50 years since deglaciation). We obtained a one-year continuous measurement record (Oct 2021–Sep 2022), which produced 4D images of soil freeze-thaw transitions with unprecedented detail, allowing us to calculate the velocity of the thawing front in 3D. At its peak, this was found to be 1 m/day for the older sediments and 0.4 m/day for the younger sediments. Records of soil moisture and thermal regime obtained by sensors help define the conditions under which snowmelt takes place. Our data reveal that the freeze-thaw shoulder period, during which the surface soils experienced the zero-curtain effect, lasted 23 days at the site closer to the glacier, but only 6 days for the older sediments. Furthermore, we used unsupervised clustering to classify areas of the soil volume according to their electrical resistivity coefficient of variance, which enables us to understand spatial variations in susceptibility to water phase transition. Novel insights about soil moisture dynamics throughout the spring melt will help parameterize models of biological activity to build a more predictive understanding of newly emerging terrestrial landscapes and their impact on carbon and nutrient cycling.

Mihai O. Cimpoiasu, Oliver Kuras, Harry Harrison, Paul B. Wilkinson, Philip Meldrum, Jonathan E. Chambers, Dane Liljestrand, Carlos Oroza, Steven K. Schmidt, Pacifica Sommers, Lara Vimercati, Trevor P. Irons, Zhou Lyu, Adam Solon, and James A. Bradley

Status: open (until 14 Apr 2024)

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  • RC1: 'Comment on egusphere-2024-350', Anonymous Referee #1, 02 Mar 2024 reply
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  • RC3: 'Comment on egusphere-2024-350', Anonymous Referee #3, 08 Apr 2024 reply
Mihai O. Cimpoiasu, Oliver Kuras, Harry Harrison, Paul B. Wilkinson, Philip Meldrum, Jonathan E. Chambers, Dane Liljestrand, Carlos Oroza, Steven K. Schmidt, Pacifica Sommers, Lara Vimercati, Trevor P. Irons, Zhou Lyu, Adam Solon, and James A. Bradley
Mihai O. Cimpoiasu, Oliver Kuras, Harry Harrison, Paul B. Wilkinson, Philip Meldrum, Jonathan E. Chambers, Dane Liljestrand, Carlos Oroza, Steven K. Schmidt, Pacifica Sommers, Lara Vimercati, Trevor P. Irons, Zhou Lyu, Adam Solon, and James A. Bradley

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Short summary
Young Arctic sediments, uncovered by retreating glaciers, are in continuous development, shaped by how water infiltrates and is stored in the near subsurface. Harsh weather conditions at high latitudes make direct observation of these environments extremely difficult. To address this, we deployed two automated sensor installations in Aug 21 on a glacier forefield in Svalbard. These recorded continuously for one year revealing unprecedented images of the ground’s freeze-thaw transition.