Sensitivity of active-layer freezing process to snow cover in Arctic Alaska
The contribution of cold-season soil respiration to the Arctic–boreal carbon cycle and its potential feedback to the global climate remain poorly quantified, partly due to a poor understanding of changes in the soil thermal regime and liquid water content during the soil-freezing process. Here, we c...
Published in: | The Cryosphere |
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Copernicus Publications
2019
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Online Access: | https://doi.org/10.5194/tc-13-197-2019 https://www.the-cryosphere.net/13/197/2019/tc-13-197-2019.pdf https://doaj.org/article/96ec022f6c9e4b90bfe9e63925fc3879 |
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fttriple:oai:gotriple.eu:oai:doaj.org/article:96ec022f6c9e4b90bfe9e63925fc3879 2023-05-15T13:09:11+02:00 Sensitivity of active-layer freezing process to snow cover in Arctic Alaska Y. Yi J. S. Kimball R. H. Chen M. Moghaddam C. E. Miller 2019-01-01 https://doi.org/10.5194/tc-13-197-2019 https://www.the-cryosphere.net/13/197/2019/tc-13-197-2019.pdf https://doaj.org/article/96ec022f6c9e4b90bfe9e63925fc3879 en eng Copernicus Publications doi:10.5194/tc-13-197-2019 1994-0416 1994-0424 https://www.the-cryosphere.net/13/197/2019/tc-13-197-2019.pdf https://doaj.org/article/96ec022f6c9e4b90bfe9e63925fc3879 undefined The Cryosphere, Vol 13, Pp 197-218 (2019) envir geo Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2019 fttriple https://doi.org/10.5194/tc-13-197-2019 2023-01-22T19:27:48Z The contribution of cold-season soil respiration to the Arctic–boreal carbon cycle and its potential feedback to the global climate remain poorly quantified, partly due to a poor understanding of changes in the soil thermal regime and liquid water content during the soil-freezing process. Here, we characterized the processes controlling active-layer freezing in Arctic Alaska using an integrated approach combining in situ soil measurements, local-scale (∼50 m) longwave radar retrievals from NASA airborne P-band polarimetric SAR (PolSAR) and a remote-sensing-driven permafrost model. To better capture landscape variability in snow cover and its influence on the soil thermal regime, we downscaled global coarse-resolution (∼0.5∘) MERRA-2 reanalysis snow depth data using finer-scale (500 m) MODIS snow cover extent (SCE) observations. The downscaled 1 km snow depth data were used as key inputs to the permafrost model, capturing finer-scale variability associated with local topography and with favorable accuracy relative to the SNOTEL site measurements in Arctic Alaska (mean RMSE=0.16 m, bias=-0.01 m). In situ tundra soil dielectric constant (ε) profile measurements were used for model parameterization of the soil organic layer and unfrozen-water content curve. The resulting model-simulated mean zero-curtain period was generally consistent with in situ observations spanning a 2∘ latitudinal transect along the Alaska North Slope (R: 0.6±0.2; RMSE: 19±6 days), with an estimated mean zero-curtain period ranging from 61±11 to 73±15 days at 0.25 to 0.45 m depths. Along the same transect, both the observed and model-simulated zero-curtain periods were positively correlated (R>0.55, p<0.01) with a MODIS-derived snow cover fraction (SCF) from September to October. We also examined the airborne P-band radar-retrieved ε profile along this transect in 2014 and 2015, which is sensitive to near-surface soil liquid water content and freeze–thaw status. The ε difference in radar retrievals for the surface (∼<0.1 m) soil ... Article in Journal/Newspaper Alaska North Slope Arctic north slope permafrost The Cryosphere Tundra Alaska Unknown Arctic Merra ENVELOPE(12.615,12.615,65.816,65.816) The Cryosphere 13 1 197 218 |
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English |
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envir geo |
spellingShingle |
envir geo Y. Yi J. S. Kimball R. H. Chen M. Moghaddam C. E. Miller Sensitivity of active-layer freezing process to snow cover in Arctic Alaska |
topic_facet |
envir geo |
description |
The contribution of cold-season soil respiration to the Arctic–boreal carbon cycle and its potential feedback to the global climate remain poorly quantified, partly due to a poor understanding of changes in the soil thermal regime and liquid water content during the soil-freezing process. Here, we characterized the processes controlling active-layer freezing in Arctic Alaska using an integrated approach combining in situ soil measurements, local-scale (∼50 m) longwave radar retrievals from NASA airborne P-band polarimetric SAR (PolSAR) and a remote-sensing-driven permafrost model. To better capture landscape variability in snow cover and its influence on the soil thermal regime, we downscaled global coarse-resolution (∼0.5∘) MERRA-2 reanalysis snow depth data using finer-scale (500 m) MODIS snow cover extent (SCE) observations. The downscaled 1 km snow depth data were used as key inputs to the permafrost model, capturing finer-scale variability associated with local topography and with favorable accuracy relative to the SNOTEL site measurements in Arctic Alaska (mean RMSE=0.16 m, bias=-0.01 m). In situ tundra soil dielectric constant (ε) profile measurements were used for model parameterization of the soil organic layer and unfrozen-water content curve. The resulting model-simulated mean zero-curtain period was generally consistent with in situ observations spanning a 2∘ latitudinal transect along the Alaska North Slope (R: 0.6±0.2; RMSE: 19±6 days), with an estimated mean zero-curtain period ranging from 61±11 to 73±15 days at 0.25 to 0.45 m depths. Along the same transect, both the observed and model-simulated zero-curtain periods were positively correlated (R>0.55, p<0.01) with a MODIS-derived snow cover fraction (SCF) from September to October. We also examined the airborne P-band radar-retrieved ε profile along this transect in 2014 and 2015, which is sensitive to near-surface soil liquid water content and freeze–thaw status. The ε difference in radar retrievals for the surface (∼<0.1 m) soil ... |
format |
Article in Journal/Newspaper |
author |
Y. Yi J. S. Kimball R. H. Chen M. Moghaddam C. E. Miller |
author_facet |
Y. Yi J. S. Kimball R. H. Chen M. Moghaddam C. E. Miller |
author_sort |
Y. Yi |
title |
Sensitivity of active-layer freezing process to snow cover in Arctic Alaska |
title_short |
Sensitivity of active-layer freezing process to snow cover in Arctic Alaska |
title_full |
Sensitivity of active-layer freezing process to snow cover in Arctic Alaska |
title_fullStr |
Sensitivity of active-layer freezing process to snow cover in Arctic Alaska |
title_full_unstemmed |
Sensitivity of active-layer freezing process to snow cover in Arctic Alaska |
title_sort |
sensitivity of active-layer freezing process to snow cover in arctic alaska |
publisher |
Copernicus Publications |
publishDate |
2019 |
url |
https://doi.org/10.5194/tc-13-197-2019 https://www.the-cryosphere.net/13/197/2019/tc-13-197-2019.pdf https://doaj.org/article/96ec022f6c9e4b90bfe9e63925fc3879 |
long_lat |
ENVELOPE(12.615,12.615,65.816,65.816) |
geographic |
Arctic Merra |
geographic_facet |
Arctic Merra |
genre |
Alaska North Slope Arctic north slope permafrost The Cryosphere Tundra Alaska |
genre_facet |
Alaska North Slope Arctic north slope permafrost The Cryosphere Tundra Alaska |
op_source |
The Cryosphere, Vol 13, Pp 197-218 (2019) |
op_relation |
doi:10.5194/tc-13-197-2019 1994-0416 1994-0424 https://www.the-cryosphere.net/13/197/2019/tc-13-197-2019.pdf https://doaj.org/article/96ec022f6c9e4b90bfe9e63925fc3879 |
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undefined |
op_doi |
https://doi.org/10.5194/tc-13-197-2019 |
container_title |
The Cryosphere |
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13 |
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container_start_page |
197 |
op_container_end_page |
218 |
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1766166241077100544 |