Soil moisture, wind speed and depth hoar formation in the Arctic snowpack

• Published in: Journal of Glaciology
• Main Authors: FLORENT DOMINE, MARIA BELKE-BREA, DENIS SARRAZIN, LAURENT ARNAUD, MATHIEU BARRERE, MATHILDE POIRIER
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2018
• Subjects: arctic snowpack; convection; permafrost; thermal conductivity; water vapor flux; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Arctic; Bylot Island; Hunt Island; Ward Hunt Island; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2018.89; https://doaj.org/article/e861c7b5fa544e158c58212cd5484d32

Basal depth hoar that forms in Arctic snowpacks often has a low thermal conductivity, strongly contributing to the snowpack thermal insulance and impacting the permafrost thermal regime. At Ward Hunt Island (Canadian high Arctic, 83°05′N, 74°07′W) almost no depth hoar was observed in spring 2016 despite favorable thermal conditions. We hypothesize that depth hoar formation was impeded by the combination of two factors (1) strong winds in fall that formed hard dense wind slabs where water vapor transport was slow and (2) low soil moisture that led to rapid ground cooling with no zero-curtain period, which reduced soil temperature and the temperature gradient in the snowpack. Comparisons with detailed data from the subsequent winter at Ward Hunt and from Bylot Island (73°09′N, 80°00′W) and with data from Barrow and Alert indicate that both high wind speeds after snow onset and low soil moisture are necessary to prevent Arctic depth hoar formation. The role of convection to form depth hoar is discussed. A simple preliminary strategy to parameterize depth hoar thermal conductivity in snow schemes is proposed based on wind speed and soil moisture. Finally, warming-induced vegetation growth and soil moisture increase should reduce depth hoar thermal conductivity, potentially affecting permafrost temperature.