Temporal dynamics of the giant Anmangynda aufeis characteristics in changing climate, 1962-2021 (North-Eastern Eurasia)
Authors: Zemlianskova Anastasiia , Alexeev Vladimir , Makarieva Olga , Nesterova Nataliia , Shikhov Andrey , Ostashov Andrey 
Published: March 2022

&lt;p&gt;Significant changes are observed in the water exchange system of the North-Eastern Eurasia which still is the remote and poorly studied region of the cryosphere. Aufeis which are well recognized from the space may serve as the indicators of such changes. Aufeis are the ice sheets formed in permafrost environment due to the layer-by-layer freezing of discharged underground or surface water, their size may reach tenths of square kilometers. The primary goal of this study is to assess the changes in the dynamics of the characteristics (area and volume) of the giant Anmangynda aufeis based on historical and modern observational data. It is located in the zone of mountainous continuous permafrost of the Magadan region of Russia and was extensively studied in 1962-1992.&lt;/p&gt;&lt;p&gt;We combined and analyzed the data of historical materials (1962-1992) with recent data from Landsat and Sentinel images (2000-2020) and our own ground-based observations on the perennial and annual dynamics of aufeis area (2020-2021). Aufeis volume was measured in 1962-1992 and in 2020-2021, but for the period of 2000-2019 the values were estimated based on the regional formula developed by [Sokolov, Sarkysyan, 1981].&lt;/p&gt;&lt;p&gt;Maximum area of aufeis reached 6.6 km&lt;sup&gt;2&lt;/sup&gt; (about 1.6% of the basin area) in 1967. According to the data of 1969 its volume may grow up to 15.7 million m&lt;sup&gt;3&lt;/sup&gt;. The greatest amplitude of fluctuations in the size of the aufeis (up to 30% of the average long-term value) was observed in the period up to 1976, then it did not exceed 10-15%. The smallest sizes of aufeis were 4.1 km&lt;sup&gt;2&lt;/sup&gt; and 5.3 million m&lt;sup&gt;3&lt;/sup&gt; in 1974, 4.3 km&lt;sup&gt;2&lt;/sup&gt; and 6.4 million m&lt;sup&gt;3&lt;/sup&gt; in 1990. Thus, over the thirty-year period of observations, the volume of aufeis has halved.&lt;/p&gt;&lt;p&gt;In the recent period, according to satellite data, these values reached the maximum of 5.8 km&lt;sup&gt;2&lt;/sup&gt; and 12.4 million m&lt;sup&gt;3&lt;/sup&gt; (2002). The lowest values were 2 times lower than the historical ones (1.9 km&lt;sup&gt;2&lt;/sup&gt; and 3.6 million m&lt;sup&gt;3&lt;/sup&gt;, 2014). Now, to study the dynamics of aufeis area and volume, the authors have been using UAV shooting. The thickness of the ice is determined by measuring the height of the surface at different periods of the aufeis development. In 2021, the maximum ice thickness reached 4.4 m, and the historical maximum was 8 m.&lt;/p&gt;&lt;p&gt;The intra-annual dynamics of aufeis has also changed. Now the aufeis gets melted completely by August-September, and in the earlier periods the part of the ice sheet (about 4% of its maximum area) remained and was included in the formation of aufeis for the next year.&lt;/p&gt;&lt;p&gt;According to natural and climatic conditions, the river basin in which the Anmangynda aufeis is formed is representative for the mountainous landscapes of the North-Eastern Eurasia. Comprehensive interdisciplinary observations at this site are important to characterize the impact of climate change on natural processes in this region.&lt;/p&gt;&lt;p&gt;The study was carried out with the support of RFBR (19-55-80028, 20-05-00666), Russian Geographical Society (project 07/2021-I (continue)) and St. Petersburg State University (project 75295776).&lt;/p&gt;