{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,15]],"date-time":"2025-12-15T04:20:25Z","timestamp":1765772425419,"version":"build-2065373602"},"reference-count":31,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2021,7,22]],"date-time":"2021-07-22T00:00:00Z","timestamp":1626912000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["NNX13AM25G","NNX14A154G","NNX16AH36A","NNX17AC59A"],"award-info":[{"award-number":["NNX13AM25G","NNX14A154G","NNX16AH36A","NNX17AC59A"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>In permafrost regions, active layer thickness (ALT) observations measure the effects of climate change and predict hydrologic and elemental cycling. Often, ALT is measured through direct ground-based measurements. Recently, synthetic aperture radar (SAR) measurements from airborne platforms have emerged as a method for observing seasonal thaw subsidence, soil moisture, and ALT in permafrost regions. This study validates airborne SAR-derived ALT estimates in three regions of Alaska, USA using calibrated ground penetrating radar (GPR) geophysical data. The remotely sensed ALT estimates matched the field observations within uncertainty for 79% of locations. The average uncertainty for the GPR-derived ALT validation dataset was 0.14 m while the average uncertainty for the SAR-derived ALT in pixels coincident with GPR data was 0.19 m. In the region near Utqia\u0121vik, the remotely sensed ALT appeared slightly larger than field observations while in the Yukon-Kuskokwim Delta region, the remotely sensed ALT appeared slightly smaller than field observations. In the northern foothills of the Brooks Range, near Toolik Lake, there was minimal bias between the field data and remotely sensed estimates. These findings suggest that airborne SAR-derived ALT estimates compare well with in situ probing and GPR, making SAR an effective tool to monitor permafrost measurements.<\/jats:p>","DOI":"10.3390\/rs13152876","type":"journal-article","created":{"date-parts":[[2021,7,22]],"date-time":"2021-07-22T22:35:31Z","timestamp":1626993331000},"page":"2876","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Validation of Permafrost Active Layer Estimates from Airborne SAR Observations"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5072-9818","authenticated-orcid":false,"given":"Andrew D.","family":"Parsekian","sequence":"first","affiliation":[{"name":"Department of Geology & Geophysics, University of Wyoming, Laramie, WY 82071, USA"},{"name":"Department of Civil & Architectural Engineering, University of Wyoming, Laramie, WY 82071, USA"}]},{"given":"Richard H.","family":"Chen","sequence":"additional","affiliation":[{"name":"Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7577-6829","authenticated-orcid":false,"given":"Roger J.","family":"Michaelides","sequence":"additional","affiliation":[{"name":"Department of Geophysics, Colorado School of Mines, Golden, CO 80401, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6293-3015","authenticated-orcid":false,"given":"Taylor D.","family":"Sullivan","sequence":"additional","affiliation":[{"name":"Department of Geology & Geophysics, University of Wyoming, Laramie, WY 82071, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7493-8101","authenticated-orcid":false,"given":"Leah K.","family":"Clayton","sequence":"additional","affiliation":[{"name":"Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3072-7334","authenticated-orcid":false,"given":"Lingcao","family":"Huang","sequence":"additional","affiliation":[{"name":"National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO 80309, USA"}]},{"given":"Yuhuan","family":"Zhao","sequence":"additional","affiliation":[{"name":"Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8604-0155","authenticated-orcid":false,"given":"Elizabeth","family":"Wig","sequence":"additional","affiliation":[{"name":"Department of Geophysics, Stanford University, Stanford, CA 94305, USA"}]},{"given":"Mahta","family":"Moghaddam","sequence":"additional","affiliation":[{"name":"Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9931-5237","authenticated-orcid":false,"given":"Howard","family":"Zebker","sequence":"additional","affiliation":[{"name":"Department of Geophysics, Stanford University, Stanford, CA 94305, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5444-9917","authenticated-orcid":false,"given":"Kevin","family":"Schaefer","sequence":"additional","affiliation":[{"name":"National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO 80309, USA"}]}],"member":"1968","published-online":{"date-parts":[[2021,7,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"045010","DOI":"10.1088\/1748-9326\/aafc1b","article-title":"Key indicators of Arctic climate change: 1971\u20132017","volume":"14","author":"Box","year":"2019","journal-title":"Environ. 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