Variability and Changes of Unfrozen Soils Below Snowpack

Lun Gao, Ardeshir Ebtehaj, Judah Cohen, Jean Pierre Wigneron

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Using four reanalysis data sets and ground-based observations, this paper uncovers that on average, 30% of the time, Northern Hemisphere snow cover experiences unfrozen bottom soil. It is demonstrated that the probability of occurrence of unfrozen soils is correlated with the snow types and is maximum over the ephemeral followed by the maritime and prairie snow. The results based on reanalysis data unveil that the seasonal evolution of the unfrozen soil areas is not synchronous with the snow cover extent and exhibits sub-annual bi-modality with two annual maxima in April and October. Interannual trend analyses indicate that shrinkage of spring snow in the past few decades has been accompanied by an increase in the proportion of unfrozen bottom soils, more significantly over polar climate regimes dominated by the tundra and taiga snow. The findings imply that the snowpack basal melting could have increased due to global warming.

Original languageEnglish (US)
Article numbere2021GL095354
JournalGeophysical Research Letters
Issue number4
StatePublished - Feb 28 2022

Bibliographical note

Funding Information:
The authors highly acknowledge the support from the Future Investigators in NASA Earth and Space Science (FINESST, 80NSSC19K1333) program through Dr. A. Leidner, and the NASA's Remote Sensing Theory Program through Dr Lucia Tsaoussi (RST, 80NSSC20K1717) Program as well as the NASA's Interdisciplinary Science (IDS, 80NSSC20K1294) program in Earth Science through Dr. Gail Skofronick‐Jackson. L. Gao is also supported by the Heinz G. Stefan Fellowship and Doctoral Dissertation Fellowship from the University of Minnesota. J. Cohen is supported by the US National Science Foundation grants PLR‐1901352. The authors also thank Dr. Chris Derksen at Environment and Climate Change Canada for insightful discussion. The first author also acknowledges technical support from Sagar Tamang at University of Minnesota for trend analysis.

Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.


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