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- Evaluation of Envisat ASAR IMP imagery for snow mapping at varying spatial resolution (Deception Island, South Shetlands – Antarctica)Publication . Mora, Carla; Vieira, Goncalo; Ramos, MiguelAdvanced synthetic aperture radar image mode precision (ASAR IMP) scenes of Deception Island from December 2008 to September 2010 have been analysed to assess its potential for snow cover classification. Backscattering was checked against ground truth. Despite the good spatial resolution of the ASAR, its applicability for detecting snow cover, and especially wet snow, was only possible at much lower resolutions, since noise was found to be very high. Scenes with bare ground or with dry snow cover showed highest backscattering, with averages from 210 to 212 dB. Wet snow showed a shift towards lower values, peaking at 215 dB. A threshold of 213 to 214 dB was identified between dry/bare ground and wet snow scenes at Crater Lake. The backscatter difference to a reference snow-free scene usually provided better classification results, and a threshold ranging from 22 to 23 dB was found. Results show that, despite the relative ease of use of C-band ASAR, special care is necessary since the results show significant noise, and it should only be applied to large areas. Large seasonal patterns of snow melt were identified on Deception Island.
- Frozen ground and snow cover monitoring in Livingston and Deception islands, Antarctica: preliminary results of the 2015-2019 PERMASNOW projectPublication . De Pablo, M.A.; Jiménez, J.J.; Ramos, M.; Prieto, M.; Molina, A.; Vieira, Gonçalo; Hidalgo, M.A.; Fernández, S.; Recondo, C.; Calleja, J.F.; Peón, J.J.; Corbea-Pérez, A.; Maior, C.N.; Morales, M.; Mora, CSince 2006, our research team has been establishing in the islands of Livingston and Deception, (South Shetland archipelago, Antarctica) several monitoring stations of the active layer thickness within the international network Circumpolar Active Layer Monitoring (CALM), and the ground thermal regime for the Ground Terrestrial Network-Permafrost (GTN-P). Both networks were developed within the International Permafrost Association (IPA). In the GTN-P stations, in addition to the temperature of the air, soil, and terrain at different depths, the snow thickness is also monitored by snow poles. Since 2006, a delay in the disappearance of the snow layer has been observed, which could explain the variations we observed in the active layer thickness and permafrost temperatures. Therefore, in late 2015 our research group started the PERMASNOW project (2015-2019) to pay attention to the effect of snow cover on ground thermal This project had two different ways to study the snow cover. On the first hand, in early 2017 we deployed new instrumentation, including new time lapse cameras, snow poles with high number of sensors and a complete and complex set of instruments and sensors to configure a snow pack analyzer station providing 32 environmental and snow parameters. We used the data acquired along 2017 and 2018 years with the new instruments, together with the available from all our already existing sensors, to study in detail the snow cover. On the other hand, remote sensing data were used to try to map the snow cover, not only at our monitoring stations but the entire islands in order to map and study the snow cover distribution, as well as to start the way for future permafrost mapping in the entire islands. MODIS-derived surface temperatures and albedo products were used to detect the snow cover and to test the surface temperature. Since cloud presence limited the acquisition of valid observations of MODIS sensor, we also analyzed Terrasar X data to overcome this limitation. Remote sensing data validation required the acquirement of in situ ground-true data, consisting on data from our permanent instruments, as well as ad hoc measurements in the field (snow cover mapping, snow pits, albedo characterization, etc.). Although the project is finished, the data analysis is still ongoing. We present here the different research tasks we are developing as well as the most important results we already obtained about the snow cover. These results confirm how the snow cover duration has been changing in the last years, affecting the ground thermal behavior.
- A proxy for snow cover and winter ground surface cooling: mapping Usnea sp. communities using high resolution remote sensing imagery (Maritime Antarctica)Publication . Vieira, Goncalo; Mora, Carla; Pina, Pedro; Schaefer, Carlos E.R.Usnea sp. formations show a spatial distribution coinciding with wind-exposed locations on rock knobs or sedimentary bodies, while they are commonly absent from concave sites. Field collection of georeferenced ground truthing data in the Meseta Norte (Fildes Peninsula, Maritime Antarctica) and the application of supervised classification techniques over a summer high resolution QuickBird satellite scene showed excellent classification accuracy for the different landcover types. The results show that Usnea formation distribution maps are a viable proxy for areas with less snow during the cold season. Such an approach provides input for permafrost and active layer modelling since snow acts as a critical control on ground surface heat balance. Since snow mapping is extremely difficult in Maritime Antarctica our tested approach provides important added-value for empirical–statistical modelling of permafrost distribution.
- Frozen ground and snow cover monitoring in the South Shetland Islands, Antarctica: instrumentation, effects on ground thermal behaviour and future researchPublication . De Pablo, M. A.; Ramos, M.; Molina, A.; Vieira, Goncalo; Hidalgo, M. A.; Prieto, M.; Jiménez, J. J.; Fernández, S.; Recondo, C.; Calleja, J. F.; Peón, J. J.; Mora, C.The study of the thermal behavior of permafrost and active layer on the South Shetland Islands, in the western side of the Antarctic Peninsula (Antarctica), has been our research topic since 1991, especially after 2006 when we established different active layer thickness and ground thermal monitoring sites of the CALM and GTN-P international networks of the International Permafrost Association. Along this period, the snow cover thickness did not change at those sites, but since 2010, we observed an elongation on the snow cover duration, with similar snow onset, but a delay on the snow offset. Due to the important effects of snow cover on the ground thermal behavior, we started in late 2015 a new research project (PERMASNOW) focused on the accurate monitoring of the snow cover (duration, density, snow water equivalent and distribution), from very different approaches, including new instrumentation, pictures analysis and remote sensing on optical and radar bands. Also, this interdisciplinary and international research team intends to compare the snow cover and ground thermal behavior with other monitoring sites in the Eastern Antarctic Peninsula where the snow cover is minimum and remains approximately constant.