Effects of meteorology and soil moisture on the spatio-temporal evolution of the depth hoar layer in the polar desert snowpack

Gautier Davesne,Florent Domine,Daniel Fortier

doi:10.1017/jog.2021.105

Abstract

AbstractIn polar deserts, depth hoar (hereinafter: DH) growth is not systematic unlike on tundra and this is critical for snowpack properties. Here, we address the spatio-temporal variability of the DH layer in the polar desert at two sites in the Canadian High Arctic: Ward Hunt Island (83° N) and Resolute Bay (75° N). Our data show that, over humid areas, DH represented a larger fraction of the snowpack and was characterized by lower density and coarser crystals than over dry gravelly areas. Increased soil moisture extends the zero-curtain period during freeze-up, leading to stronger temperature gradients in the snowpack and greater kinetic metamorphism. Our results also demonstrate that the large inter-annual variability in DH is primarily driven by wind conditions in the fall since this key variable controls the initial snow density and snow onset date. These strong controls exerted by soil moisture and meteorological conditions on DH growth in polar deserts highlight the possibility of major changes in polar snowpacks physical properties in response to the rapid climate and environmental changes currently affecting these regions.

Highlights

As a mix of air and ice, snow exhibits unique thermophysical and optical properties, which include: (1) its high shortwave albedo and high-thermal emissivity; (2) its high-thermal insulation capacity and (3) its capacity to store and release water and energy as latent heat (Warren, 1982; Pomeroy and Brun, 2001)
Part of the offset between unmanned aerial vehicle (UAV) and manual measurements can be attributed to the bias associated with the snow probing which can overestimate by a few centimeters when the probe penetrates the ground, especially on gravel surfaces or organic soils (Stuefer and others, 2020)
Our study provides new insights into DH development and its spatio-temporal variability at WHI, the main site, and RB, the secondary site, which are both representative of polar desert environments in terms of landscape and climate conditions

Summary

Introduction

As a mix of air and ice, snow exhibits unique thermophysical and optical properties, which include: (1) its high shortwave albedo and high-thermal emissivity; (2) its high-thermal insulation capacity and (3) its capacity to store and release water and energy as latent heat (Warren, 1982; Pomeroy and Brun, 2001). Polar deserts are characterized by low winter precipitation, unevenly redistributed across the landscape during and after snowfalls by strong winds, and the predominance of nonvegetated mineral soils These conditions make polar deserts fundamentally different from Arctic tundra regions in terms of climatic and environmental conditions (soil composition, vegetation and surface hydrology) with direct consequences on the snowpack. DH formation is related to a strong vertical temperature gradient (>20°C m−1) within the early season snowpack which induces a water vapor pressure gradient It results in an intense upward water vapor flux by diffusion from the warmer to the cooler layers of the snowpack leading to kinetic grain growth by recrystallization (Sturm and Benson, 1997). These upward heat and mass transfers can be enhanced by convection (Trabant and Benson, 1972; Sturm and Benson, 1997) and windinduced air advection (wind-pumping; Cunningham and Waddington, 1993; Albert and others, 2002)

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Conclusion