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- Thermal state of permafrost and active-layer monitoring in the antarctic: advances during the international polar year 2007-2009Publication . Vieira, Goncalo; Bockheim, James; Guglielmin, Mauro; Balks, Megan; Abramov, Andrey A; Boelhouwers, Jan; Cannone, Nicoletta; Ganzert, Lars; Gilichinsky, David A.; Goryachkin, Sergey; López-Martínez, Jerónimo; Meiklejohn, Ian; Raffi, Rossana; Ramos, Miguel; Schaefer, Carlos; Serrano, Enrique; Simas, Felipe; Sletten, Ronald; Wagner, DirkResults obtained during the International Polar Year (IPY) on the thermal state of permafrost and the active layer in the Antarctic are presented, forming part of ANTPAS (‘Antarctic Permafrost and Soils’), which was one of the key projects developed by the International Permafrost Association and the Scientific Committee for Antarctic Research for the IPY. The number of boreholes for permafrost and active-layer monitoring was increased from 21 to 73 during the IPY, while CALM-S sites to monitor the active layer were increased from 18 to 28. Permafrost temperatures during the IPY were slightly below 08C in the South Shetlands near sea-level, showing that this area is near the climatic boundary of permafrost and has the highest sensitivity to climate change in the region. Permafrost temperatures were much lower in continental Antarctica: from the coast to the interior and with increasing elevation they ranged between 13.38C and 18.68C in Northern Victoria Land, from 17.48C to 22.58C in the McMurdo Dry Valleys, and down to 23.68C at high elevation on Mount Fleming (Ross Island). Other monitored regions in continental Antarctica also showed cold permafrost: Queen Maud Land exhibited values down to 17.88C on nunataks, while in Novolazarevskaya (Schirmacher Oasis) at 80 m a.s.l. the permafrost temperature was 8.38C. The coastal stations of Molodeznaya at Enderby Land showed permafrost temperatures of 9.88C, Larsemann Hills – Progress Station in the Vestfold Hills region – recorded 8.58C, and Russkaya in Marie Byrd Land, 10.48C. This snapshot obtained during the IPY shows that the range of ground temperatures in the Antarctic is greater than in the Arctic.
- Active layer dynamics in three topographically distinct lake catchments in Byers Peninsula (Livingston Island, Antarctica)Publication . Oliva, Marc; Hrbacek, Filip; Ruiz-Fernández, Jesús; de Pablo, Miguel Ángel; Vieira, Goncalo; Ramos, Miguel; Antoniades, DermotTopography exerts a key role in controlling permafrost distribution in areas where mean annual temperatures are slightly negative. One such case is the low-altitude environments of Maritime Antarctica, where permafrost is sporadic to discontinuous below 20–40 m asl and continuous at higher areas and active layer dynamics are thus strongly conditioned by geomorphological setting. In January 2014 we installed three sites for monitoring active layer temperatures across Byers Peninsula (Livingston Island, South Shetland Islands) at elevations between 45 and 100 m. The sites are situated in lake catchments (lakes Escondido, Cerro Negro, and Domo) that have different geomorphological and topographical conditions. Our objective was to examine the role of topography and microclimatic conditions in determining the active layer thermal regime in order to identify the factors that control geomorphic processes in these lake catchments. At each site a set of loggers was installed to monitor air temperature (AT), snow thickness (SwT) and soil temperature (ST) down to 80 cm depth. Mean annual air temperatures (MAAT) showed similar values in the three sites (−2.7 to −2.6 °C) whereas soil temperatures showed varying active layer thicknesses at the three catchments. The ground thermal regime was strongly controlled by soil properties and snow cover thickness and duration, which is influenced by local topography. Geomorphological processes operating at the lake catchment scale control lacustrine sedimentation processes, and both are dependent on the combination of topographical and climatic conditions. Therefore, the interpretation of lake sediment records from these three lakes requires that soil thermal regime and snow conditions at each site be taken into account in order to properly isolate the geomorphological, environmental and climatic signals preserved in these lake records.
- 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.
- Recent shallowing of the thaw depth at Crater Lake, Deception Island, Antarctica (2006–2014)Publication . Ramos, M.; Vieira, Goncalo; de Pablo, M.A.; Molina, A.; Abramov, A.; Goyanes, G.The Western Antarctic Peninsula region is one of the hot spots of climate change and one of the most ecologicallysensitive regions of Antarctica,where permafrostis near its climatic limits. The research was conducted in Decep-tion Island, an active stratovolcano in the South Shetlands archipelago off the northern tip of the Antarctic Pen-insula. The climate is polar oceanic, with high precipitation and mean annual air temperatures (MAAT) close to−3 °C. The soils are composed by ashes and pyroclasts with high porosity and high water content, with ice-rich permafrost at−0.8 °C at the depth of zero annual amplitude, with an active layer of about 30 cm. Resultsfrom thaw depth, ground temperature and snow cover monitoring at the Crater Lake CALM-S site over the period2006 to 2014 are analyzed. Thaw depth (TD) was measured by mechanical probing once per year in the end ofJanuary or early February in a 100 × 100 m with a 10 m spacing grid. The results show a trend for decreasingthaw depth from ci. 36 cm in 2006 to 23 cm in 2014, while MAAT, as well as ground temperatures at the baseof the active layer, remained stable. However, the duration of the snow cover at the CALM-S site, measuredthrough the Snow Pack Factor (SF) showed an increase from 2006 to 2014, especially with longer lasting snowcover in the spring and early summer. The negative correlation between SF and the thaw depth supports the sig-nificance of the influence of the increasing snow cover inthaw depth,evenwith notrendin the MAAT.The lack ofobserved ground cooling in the base of the active layer is probably linked to the high ice/water content at thetransient layer. The pyroclastic soils of Deception Island, with high porosity, are key to the shallow active layerdepths, when compared to other sites in the Western Antarctic Peninsula (WAP). Thesefindings support thelack of linearity between atmospheric warming and permafrost warming and induce an extra complexity tothe understanding of the effects of climate change in the ice-free areas of the WAP, especially in scenarios withincreased precipitation as snow fall.
- 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.
- Interannual variability of ground surface thermal regimes in Livingston and Deception islands, Antarctica (2007–2021)Publication . Pablo, M. A. de; Ramos, M.; Vieira, Gonçalo; Molina, A.; Ramos, R.; Maior, C. N.; Prieto, M.; Ruiz‐Fernández, J.The absence of vegetation in most ice-free areas of Antarctica makes the soil surface very sensitive to atmosphere dynamics, especially in the western sector of the Antarctic Peninsula, an area within the limits of the permafrost zone. To evaluate the possible effects of regional warming on frozen soils, we conducted an analysis of ground surface temperatures (GSTs) from 2007 to 2021 from different monitoring sites in Livingston and Deception islands (South Shetlands archipelago, Antarctica). The analysis of the interannual evolution of the GST and their daily regimes and the freezing and thawing indexes reveals that climate change is showing impacts on seasonal and perennially frozen soils. Freezing Degree Days (FDD) have decreased while Thawing Degree Day (TDD) have increased during the study period, resulting in a balance that is already positive at the sites at lower elevations. Daily freeze–thaw cycles have been rare and absent since 2014. Meanwhile, the most common thermal regimes are purely frozen – F1 (daily temperatures < = 0.5C), isothermal – IS (ranging between 0.5C to +0.5C), and purely thawed – T1 (> = +0.5C). A decrease in F1 days has been observed, while the IS and T1 days increased by about 60 days between 2007 and 2021. The annual number of days with snow cover increased between 2009 and 2014 and decreased since then. The GST and the daily thermal regimes evolution point to general heating, which may be indicative of the degradation of the frozen soils in the study area.
- Transition from a Subaerial to a Subnival Permafrost Temperature Regime Following Increased Snow Cover (Livingston Island, Maritime Antarctic)Publication . Ramos, Miguel; Vieira, Gonçalo; de Pablo, Miguel Angel; Molina, Antonio; Jiménez Cuenca, Juan JavierThe Antarctic Peninsula (AP) region has been one of the regions on Earth with strongest warming since 1950. However, the northwest of the AP showed a cooling from 2000 to 2015, which had local consequences with an increase in snow accumulation and a deceleration in the loss of mass from glaciers. In this paper, we studied the e ects of increased snow accumulation in the permafrost thermal regime in two boreholes (PG1 and PG2) in Livingston Island, South Shetlands Archipelago, from 2009 to 2015. The two boreholes located c. 300 m apart but at similar elevation showed di erent snow accumulation, with PG2 becoming completely covered with snow all year long, while the other remained mostly snow free during the summer. The analysis of the thermal regimes and of the estimated soil surface energy exchange during the study period showed the e ects of snow insulation in reducing the active layer thickness. These e ects were especially relevant in PG2, which transitioned from a subaerial to a subnival regime. There, permafrost aggraded from below, with the active layer completely disappearing and the e ciency of thermal insulation by the snowpack prevailing in the thermal regime. This situation may be used as an analogue for the transition from a periglacial to a subglacial environment in longer periods of cooling in the paleoenvironmental record.