ALBERT

Description: Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007–2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.

Description: Situated in the Yana-Highlands, the Batagai profile is one of the few inland permafrost outcrops in Yakutia and, for the time being, the biggest and most active thermoerosional cirque worldwide. With Yerkhoyansk recorded as place of the pole of cold, the Yana Highlands represent the region with the most severe climatic continentality in the northern hemisphere. In contrast to the numerous sequences in today’s coastal lowlands, the Batagai sequence was always unaffected by maritime climate influence during its formation and thus better indicates the macro-climate evolution in NE-Siberia. As result of intense thermal degradation, the outcrop formed within 30 years only and cut deep into ice-rich permafrost deposits. The 60 m deep outcrop is now about 850 m in diameter, but erosion rates as high as 15 m/year are changing the dimensions continuously. The Batagai profile thus represents a unique window into the past (and future) of ice-rich permafrost deposits in Yakutia. Field based observations have shown that the permafrost sequence consists of 4 distinct units: below a thin Holocene surface cover, a 30 meter thick Ice Complex with characteristic thick ice wedges has formed. At the base of the Ice Complex, there is an up to 2 m thick layer of plant material including large woody remains. Subjacent to this organic layer of supposedly Eemian origin, there is a horizontally stratified unit composed of silty-sand and without thick syngenetic ice wedges presumably deposited during the Middle Pleistocene. At the very base of the sequence, there appears to emerge another unit including syngenetic ice wedges. This unit was not accessible for sampling. The accessible upper about 45 meter of the sequence were sampled from top to bottom in one meter steps using, due to the difficult accessibility of the permafrost wall, thermokarst mounds in the less steep part of the outcrop. The samples were taken for sedimentological analyses and especially for plant macrofossil and other palaeoecological studies. Whereas sediments give insight into the genesis of the sequence, fossil plant macroremains provide information on local vegetation patterns and habitats at the time of deposition; while palynological analyses reflect the regional vegetation and climate history. First palaeobotanical results will be represented in Session 13: Palaeoenvironments in permafrost affected areas. The sedimentological analyses revealed that, despite clearly delimitable bedding units visible at the outcrop, there is no distinct litho-stratigraphical differentiation recognizable in the grain size distribution or other sedimentological parameters. Accordingly, the sequence is characterized by a grain size signature typical for Ice Complex deposits. In comparison to other Yakutian ice-rich permafrost sequences, e.g. in the coastal lowlands, the Batagai profile is however distinguished by a higher fraction of fine sand over the whole recorded sequence. This might be due to increased aeolian deposition from local sources, e.g. from barren ridges in the highlands uncovered by vegetation. The assumption that aeolian deposition played a substantial role in the formation of the sequence is also suggested by impressive dunes in the immediate vicinity of the profile at the boundary of Batagai city.