Environmental and climate dynamics in northeastern Siberia according to diatom oxygen isotopes

The sedimentary sequence from Lake Emanda (65°17′N; 135°45′E; 675 m a.s.l), one large freshwater body (33.1 km2) in the continuous permafrost of the Verkhoyansk Mountains, has been investigated within the German-Russian ‘Paleolimnological Transect’ (PLOT) project. It provided important insight into the environmental and climate dynamics in northeastern Siberia

Northern Eurasian large lakes history: sediment records obtained in the frame of Russian-German research project PLOT

Russian-German project PLOT (Paleolimnological Transect) aims at investigating the regional responses of the quaternary climate and environment on external forcing and feedback mechanisms along a more than 6000 km long longitudinal transect crossing Northern Eurasia. The well-dated record from Lake El´gygytgyn used as reference site for comparison the local climatic and environmental histories. Seismic surveys and sediment coring up to 54 m below lake floor performed in the frame of the project on Ladoga Lake (North-West of Russia; 2013), Lake Bolshoye Shchuchye (Polar Ural; 2016), Lake Levinson-Lessing and Lake Taymyr (Taymyr Peninsula; 2016-2017), Lake Emanda (Verkhoyansk Range; 2017). Fieldwork at Polar Ural and Taymyr Peninsula was conducted in collaboration with the Russian-Norwegian CHASE (Climate History along the Arctic Seaboard of Eurasia) project. Here, we present the major results of the project obtained so far

Climatic and environmental changes in the Yana Highlands of north‐eastern Siberia over the last c. 57 000 years, derived from a sediment core from Lake Emanda.

The sediment succession of Lake Emanda in the Yana Highlands was investigated to reconstruct the regional late Quaternary climate and environmental history. Hydro‐acoustic data obtained during a field campaign in 2017 show laminated sediments in the north‐western and deepest (up to ̃15 m) part of the lake, where a ̃6‐m‐long sediment core (Co1412) was retrieved. The sediment core was studied with a multi‐proxy approach including sedimentological and geochemical analyses. The chronology of Co1412 is based on 14C AMS dating on plant fragments from the upper 4.65 m and by extrapolation suggests a basal age of c. 57 cal. ka BP. Pronounced changes in the proxy data indicate that early Marine Isotope Stage (MIS) 3 was characterized by unstable environmental conditions associated with short‐term temperature and/or precipitation variations. This interval was followed by progressively colder and likely drier conditions during mid‐MIS 3. A lake‐level decline between 32.0 and 19.1 cal. ka BP was presumably related to increased continentality and dry conditions peaking during the Last Glacial Maximum (LGM). A subsequent rise in lake level could accordingly have been the result of increased rainfall, probably in combination with seasonally high meltwater input. A milder or wetter Lateglacial climate increased lake productivity and vegetation growth, the latter stabilizing the catchment and reducing clastic input into the lake. The Bølling‐Allerød warming, Younger Dryas cooling and Holocene Thermal Maximum (HTM) are indicated by distinct changes in the environment around Lake Emanda. Unstable, but similar‐to‐present‐day climatic and environmental conditions have persisted since c. 5 cal. ka BP. The results emphasize the highly continental setting of the study site and therefore suggest that the climate at Lake Emanda was predominantly controlled by changes in summer insolation, global sea level, and the extent of ice sheets over Eurasia, which influenced atmospheric circulation patterns

Seismic stratigraphical record of Lake Levinson-Lessing, Taymyr Peninsula: evidence for ice-sheet dynamics and lake-level fluctuations since the Early Weichselian

A multi-channel, high-resolution seismic reflection survey using a Micro-GI airgun was carried out in the framework of the Russian-German project PLOT (Paleolimnological Transect) on Lake Levinson-Lessing, Taymyr Peninsula, in 2016. In total, similar to 70km of seismic reflection profiles revealed in unprecedented detail the glacial and postglacial sedimentary infill of the lake basin. Five main seismic units have been recognized and interpreted as glacial (Unit V), subglacial and proglacial (Unit IV), marine (Unit III), fluvial-lacustrine (Unit II) and lacustrine (Unit I) sediments. Of particular significance are imbricated, south-orientated structures present in the southernmost part of the lake basin within Unit V and a large topographic ridge recognized in front of those structures. We interpret these structures as push moraines and an end moraine, respectively, left by the glacier after its retreat. The depositional pattern of the units above the moraines documents past lake-level fluctuations. We interpret Unit IV, Unit III and Unit I as highstand deposits, and Unit II as lowstand deposits. Gas-charged sediments dominate the northern part of the lake basin, whilst they occur only sporadically and in limited spatial extent in the central and southern parts of the lake. In the latter areas, the seismic and echo-sounder data suggest recent tectonic activity. Our study contributes to the reconstruction of environmental conditions in the Taymyr Peninsula directly following the Early Weichselian deglaciation and shows that deep tectonic lake basins affected by several glaciations can preserve important palaeoenvironmental records, which contributes significantly to our understanding of palaeoenvironmental changes in the Taymyr Peninsula and the central Russian Arctic

Climatic and environmental changes in the Yana Highlands of north‐eastern Siberia over the last c. 57 000 years, derived from a sediment core from Lake Emanda

The sediment succession of Lake Emanda in the Yana Highlands was investigated to reconstruct the regional late Quaternary climate and environmental history. Hydro‐acoustic data obtained during a field campaign in 2017 show laminated sediments in the north‐western and deepest (up to ̃15 m) part of the lake, where a ̃6‐m‐long sediment core (Co1412) was retrieved. The sediment core was studied with a multi‐proxy approach including sedimentological and geochemical analyses. The chronology of Co1412 is based on 14C AMS dating on plant fragments from the upper 4.65 m and by extrapolation suggests a basal age of c. 57 cal. ka BP. Pronounced changes in the proxy data indicate that early Marine Isotope Stage (MIS) 3 was characterized by unstable environmental conditions associated with short‐term temperature and/or precipitation variations. This interval was followed by progressively colder and likely drier conditions during mid‐MIS 3. A lake‐level decline between 32.0 and 19.1 cal. ka BP was presumably related to increased continentality and dry conditions peaking during the Last Glacial Maximum (LGM). A subsequent rise in lake level could accordingly have been the result of increased rainfall, probably in combination with seasonally high meltwater input. A milder or wetter Lateglacial climate increased lake productivity and vegetation growth, the latter stabilizing the catchment and reducing clastic input into the lake. The Bølling‐Allerød warming, Younger Dryas cooling and Holocene Thermal Maximum (HTM) are indicated by distinct changes in the environment around Lake Emanda. Unstable, but similar‐to‐present‐day climatic and environmental conditions have persisted since c. 5 cal. ka BP. The results emphasize the highly continental setting of the study site and therefore suggest that the climate at Lake Emanda was predominantly controlled by changes in summer insolation, global sea level, and the extent of ice sheets over Eurasia, which influenced atmospheric circulation patterns.Bundesministerium für Bildung und Forschun

The Lastglacial and Holocene seismostratigraphy and sediment distribution of Lake Bolshoye Shchuchye, Polar Ural Mountains, Arctic Russia

Seismostratigraphical studies of the 11.8-km(2)-large and similar to 140-m-deep Lake Bolshoye Shchuchye, Polar Ural Mountains, reveal up to 160-m-thick acoustically laminated sediments in the lake basin. Using a dense grid of seismic lines, the spatial and temporal distributions of the sedimentary history have been reconstructed. Three regional seismic horizons have been identified and correlated with the well-dated 24-m-long sediment core retrieved from the lake. Isopach maps constructed from the seismic data show four phases of sedimentation. A contour map of the deepest regional seismic reflector represents the earliest hemipelagic sedimentation in the lake. Three contour maps represent time intervals covering the last 23cal. ka based on the well-dated core stratigraphy from the lake. The detailed time constraints on the upper stratigraphical units in the lake allow calculation of the lake's development in terms of sediment fluxes and the denudation rates from the Last Glacial Maximum (LGM) to the present. The sedimentation in Lake Bolshoye Shchuchye has been dominated by hemipelagic processes during at least the last 24cal. ka BP only locally interrupted by delta progradation and slope processes. A major shift in the sediment accumulation at c.18.7cal. ka BP is interpreted to mark the end of the local glacial maximum, greatly reduced denudation and the onset of the deglaciation period; this also demonstrates how fast the glaciers melted and possibly disappeared at the end of the LGM. The denudation rate during the Holocene is only a fifth of the LGM rate. The age of the oldest stratified sediments in Lake Bolshoye Shchuchye is not well constrained, but estimated as c. 50-60 ka

Biogeochemistry analysis of sediment core Co1412 in the Yana Highlands

The sediment succession of Lake Emanda in the Yana Highlands was investigated to reconstruct the regional late Quaternary climate and environmental history. Hydro-acoustic data obtained during a field campaign in 2017 show laminated sediments in the north-western and deepest (up to ~15 m) part of the lake, where a ~6-m-long sediment core (Co1412, latitude 65°17.6490N, longitude 135°45.5540E) was retrieved. The sediment core was studied with a multi-proxy approach including sedimentological and geochemical analyses. The chronology of Co1412 is based on 14C AMS dating on plant fragments from the upper 4.65 m and by extrapolation, suggesting a basal age of c. 57 cal. ka BP.Biogeochemistry analysis of sediment Co1412: TOC=total organic carbon (%), TN=total nitrogen (%), TOC/TN (atomic), TS=total sulphur (%), TIC=total inorganic carbon (%) data of sediment Co1412 against composite depth (cm) and age (cal. a BP)