Modern and fossil diatom assemblages from Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Siberia)

This article discusses the results of a taxonomic and ecological investigation into diatoms from polygonal ponds and quaternary permafrost deposits of Bol’shoy Lyakhovsky Island (New Siberian Archipelago) and the reconstruction of climatic changes on the island during Late Pleistocene/Holocene transition using fossil diatom assemblages from the permafrost deposits. The taxonomic list of diatoms includes 159 diatom species. The main ecological factors that determine the distribution of diatoms in the investigated data set are mean air temperature in July, рН, conductivity, water depth, and the concentration of Si4+ and Al3+. An increase in water depth and stable lacustrine conditions in the Lateglacial–Holocene in the ancient thermokarst lake relate to Lateglacial warming before 11860 ± 160 years BP and during the early Holocene between 11210 ± 160 and 7095 ± 60 years BP

Holocene thermokarst and pingo development in the Kolyma Lowland (NE Siberia)

Ground ice and sedimentary records of a pingo exposure reveal insights into Holocene permafrost, landscape and climate dynamics. Early to mid‐Holocene thermokarst lake deposits contain rich floral and faunal paleoassemblages, which indicate lake shrinkage and decreasing summer temperatures (chironomid‐based TJuly) from 10.5 to 3.5 cal kyr BP with the warmest period between 10.5 and 8 cal kyr BP. Talik refreezing and pingo growth started about 3.5 cal kyr BP after disappearance of the lake. The isotopic composition of the pingo ice (δ18O − 17.1 ± 0.6‰, δD −144.5 ± 3.4‰, slope 5.85, deuterium excess −7.7± 1.5‰) point to the initial stage of closed‐system freezing captured in the record. A differing isotopic composition within the massive ice body was found (δ18O − 21.3 ± 1.4‰, δD −165 ± 11.5‰, slope 8.13, deuterium excess 4.9± 3.2‰), probably related to the infill of dilation cracks by surface water with quasi‐meteoric signature. Currently inactive syngenetic ice wedges formed in the thermokarst basin after lake drainage. The pingo preserves traces of permafrost response to climate variations in terms of ground‐ice degradation (thermokarst) during the early and mid‐Holocene, and aggradation (wedge‐ice and pingo‐ice growth) during the late Holocene

Western Beringia and beyond - three decades of German-Russian paleoenvironmental research on Siberian permafrost

With first joint fieldwork on Taymyr Peninsula during mid-1990s, a successful cooperation of German, Russian, and further international partners on permafrost and Quaternary palaeoenvironments in Siberia was started and resulted in extensive joint research for 3 decades. Studies of permafrost deposits and ground ice provided insights on past environmental and climatic changes, covering several hundreds of thousands of years into the past. They provide multi-proxy evidence for multiple glacial/interglacial cycles and different periods of past climate change or stability in Arctic land environments. Study objects were natural permafrost exposures along coastal sections, thaw slumps, and river banks, studied mostly during summers, complemented by permafrost cores from land, lake and sea ground drilled mostly in spring. Exposure geometry and stratigraphic horizon thickness have been surveyed using laser tachymetry, other measuring equipment, and drones. Based on multi-proxy analyses, mid- and late Quaternary periods were studied, resulting in >300 scientific papers. The approach includes geomorphic studies, various geochronological analyses, analysis of frozen sediments (for ice, carbon, nitrogen, and carbonate contents, grain-size parameters, magnetic susceptibility, heavy mineral compositions), ground ice (stable water isotopes, major ions) and of numerous fossil bioindicators, to reconstruct the Quaternary paleoenvironmental change. Oldest permafrost horizons were dated from the Batagay mega-thaw-slump (Yana Uplands) to about 650 ky with luminescence dating. Here and elsewhere, records of Eemian and Holocene interglacial periods, and environmental conditions associated with it were targeted. Many sites with late Pleistocene Yedoma Ice Complex have been explored. Lateglacial and Holocene warming induced enormous periglacial landscape changes by widespread permafrost degradation and substantial paleoecological changes. For vast Siberian areas where glacial records are not available, we aim on the establishment of permafrost as paleoclimatic archive, emphasizing peculiarities of permafrost age control and record resolution and stressing the great potential for understanding climate variability on glacial-interglacial timescales in Western Beringia

Diatoms of Modern Bottom Sediments in Siberian Arctic

The investigation of the species composition and ecology of diatoms of modern bottom sediments in water bodies of arctic polygonal tundra in three subregions of North Yakutiya has been carried out. As a result, 161 taxons of diatoms were determined; the determinant role of the depth, conductivity, pH of the water, and geographic latitude in their distribution was confirmed, and two complexes of species with respect to the leading abiotic factors were distinguished. The diatoms of the first complex prefer shallow water bodies of high latitudes with neutral and slightly alkaline water and relatively high conductivity. The second complex is confined to the water bodies of lower latitudes with small conductivity, as well as neutral and slightly acidic water

Diatoms from Modern Lake Sediments of Lake Lebedinoe (Yamalo-Nenets Autonomous District, West Siberian Arctic, Russia)

Arctic reservoirs are excellent indicators of the ongoing increase in air temperature on the planet. The West Siberian Arctic, especially its northern part, is poorly studied algologically. The aim of this work was to study the taxonomic composition of diatoms in modern sediments of Lake Lebedinoe (YNAD, West Siberian Arctic, Russia). 18 sediment samples were processed in the range from 1 to 36 cm. As a result 60 taxa of diatoms were identified in modern bottom sediments of the Lake Lebedinoe

Diatoms of Holocene Sediments of Lake Bolshoy Kharbei (Bolshezemelskaya Tundra, Russia)

Арктические озера, не затронутые прямым антропогенным воздействием, являются прекрасными объектами для палеоклиматических реконструкций. Одним из источников информации о произошедших изменениях в экосистемах озер могут быть диатомовые водоросли. Изучение диатомовых водорослей в голоценовых осадках ледникового оз. Большой Харбей Большеземельской тундры позволило установить 122 видовых и внутривидовых таксона, относящихся к 2 классам, 5 порядкам, 18 семействам и 45 родам с преобладанием космополитных алкалифильных бентосных видов стояче-текучих вод, индифферентных к солености, обитающих в умеренных температурных условиях. Была выявлена тенденция формирования диатомовой флоры голоценовых осадков оз. Большой Харбей, проявляющаяся в изменении состава доминантов в связи с потеплением климата. В качестве реакции на рост палеотемператур происходит увеличение периода открытой воды в озере и водности, что способствует лучшему развитию планктонных центрических и мелких пенатных диатомей с последующим возрастанием доли их створок в донных осадкахArctic lakes, which are not affected by direct human impact, are excellent objects for paleoclimatic reconstructions. Diatoms can be a source of information about the changes that occurred in lakes. The recent Holocene sediments from deep glacial arctic Lake Bolshoy Kharbei of Bolshezemelskaya tundra were studied for diatoms. In total, 122 taxa of 2 classes, 5 orders, 18 families, 45 genus of cosmopolitan forms with a predominance of alkaliphilic benthic species of diatoms preferring a standing – flowing waters, indifferent to salinity and moderate temperature conditions were revealed. There is a trend in forming diatom flora of Holocene sediments of Lake Bolshoy Kharbei manifested in changes in the composition of dominants due to climate warming. As a response to increase of paleotemperature, the lengthening of the growing season and period of open water in the lake, the rise of the water level and the rate of water exchange took place, which contributed to the development of planktonic centric and small pennate diatoms with a consequent increasing of their valves share in the sediment