Freezing and thawing of lakes on the Nelson and King George Islands, Antarctic, using Sentinel 1A synthetic aperture rad
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Freezing and thawing of lakes on the Nelson and King George Islands, Antarctic, using Sentinel 1A synthetic aperture radar images Cristiano Niederauer da Rosa & Ulisses Franz Bremer & Waterloo Pereira Filho Manoel Araujo Sousa Júnior & Gisieli Kramer & Fernando Luis Hillebrand & Janisson Batista de Jesus
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Received: 23 January 2020 / Accepted: 27 July 2020 # Springer Nature Switzerland AG 2020
Abstract This article aims to analyze the dynamics of freezing and thawing of Antarctic lakes located in icefree areas on Nelson Island and Fildes Peninsula, where response to changes in air temperature and precipitation rates occur rapidly, during the period from July 2016 to December 2018. In these places, which are difficult to access, remote sensing is an important alternative, especially considering the use of active remote sensors such as the Synthetic Aperture Radar (SAR), which has less restriction regarding the presence of clouds over the study area. Three backscatter thresholds were defined (σ) for the identification of the physical state of the water of the lakes of the study region, applied in Sentinel 1A SAR (S1A) images under Horizontal Horizontal (HH) polarization and Interferometric Wide (IW) imaging C. N. da Rosa (*) : U. F. Bremer : F. L. Hillebrand Polar and Climate Center, Postgraduate Program in Remote Sensing, Federal University of Rio Grande do Sul-UFRGS, Avenida Bento Gonçalves, 9500, Building 43136, rooms 208 and 210, Porto Alegre, Rio Grande do Sul 91501-970, Brazil e-mail: [email protected]
U. F. Bremer e-mail: [email protected] F. L. Hillebrand e-mail: [email protected] W. Pereira Filho Department of Geosciences, Federal University of Santa Maria, Av. Roraima, 1000, Santa Maria, Rio Grande do Sul. 97105-900, Brazil e-mail: [email protected]
mode. These images, along with the air temperature data obtained by the Interim Re-Analysis (ERA-Interim) atmospheric reanalysis model, provided the evidence for the interpretation of the freezing and thawing periods of the lakes. The thresholds applied for the definition of the physical state of the lake water were greater than − 14 dB for frozen water, between − 14 and − 17 dB for the surface, with up to 60% of their frozen area, and less than − 17 dB for open water. The temporal analysis revealed that the lakes start to thaw in October, become completely thawed in February, and freeze again in March. Nevertheless, it can be said that the S1A satellite allows a satisfactory identification of the liquid and solid phases of the water in the lakes of the study region.
M. A. Sousa Júnior Department of Rural Engineering, Federal University of Santa Maria, Av. Roraima, 1000, Santa Maria, Rio Grande do Sul 97105-900, Brazil e-mail: [email protected] G. Kramer Postgraduate Program in Geography, Federal University of Santa Maria, Av. Roraima, 1000, Santa Maria, Rio Grande do Sul 97105-900, Brazil e-mail: [email protected] J. B. de Jesus Postgraduate Program in Remote Sensing, Federal University of Rio Grande do Sul, Avenida Bento Gon
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