Irina Streletskaya

Permafrost hydrology in changing climatic conditions: seasonal variability of stable isotope composition in rivers in discontinuous permafrost

Role of changing climatic conditions on permafrost degradation and hydrology was investigated in the transition zone between the tundra and forest ecotones at the boundary of continuous and discontinuous permafrost of the lower Yenisei River. Three watersheds of various sizes were chosen to represent the characteristics of the regional landscape conditions. Samples of river flow, precipitation, snow cover, and permafrost ground ice were collected over the watersheds to determine isotopic composition of potential sources of water in a river flow over a two year period. Increases in air temperature over the last forty years have resulted in permafrost degradation and a decrease in the seasonal frost which is evident from soil temperature measurements, permafrost and active-layer monitoring, and analysis of satellite imagery. The lowering of the permafrost table has led to an increased storage capacity of permafrost affected soils and a higher contribution of ground water to river discharge during winter months. A progressive decrease in the thickness of the layer of seasonal freezing allows more water storage and pathways for water during the winter low period making winter discharge dependent on the timing and amount of late summer precipitation. There is a substantial seasonal variability of stable isotopic composition of river flow. Spring flooding corresponds to the isotopic composition of snow cover prior to the snowmelt. Isotopic composition of river flow during the summer period follows the variability of precipitation in smaller creeks, while the water flow of larger watersheds is influenced by the secondary evaporation of water temporarily stored in thermokarst lakes and bogs. Late summer precipitation determines the isotopic composition of texture ice within the active layer in tundra landscapes and the seasonal freezing layer in forested landscapes as well as the composition of the water flow during winter months.

Erosion of Sediment and Organic Carbon from the Kara Sea Coast

Abstract We have estimated the erosion of sediment and organic carbon input from the Kara Sea coast based on extensive mapping, geologic and cryolithologic investigations of coastal zone and seafloor sediments, and revision of previously published data. The amount of coastal sediment eroded into the Kara Sea was determined to be approximately 35 million tons. Twenty-seven million tons are attributed to solid material, 7.6 million to thawed ground ice, 0.4 million to organic carbon, and 0.3 million to soluble salts. The estimate of organic carbon input presented herein is 2.5-fold less than previously published elsewhere. The majority of organic carbon in marine clayey deposits was found to be present in an adsorbed form. Its quantity corresponds to the content of clay particles in Pleistocene sediments. Organic carbon content in clay marine sediments remains unchanged during freeze-thaw processes, indicating that this form of carbon is stable unless thermoerosion is taking place.

New permafrost feature: deep crater in Central Yamal, West Siberia, Russia as a response to local climate fluctuations

This paper is based on field data obtained during short visits to a newly formed permafrost feature in a form of relatively narrow, deep crater. Excluding impossible and improbable versions of the crater’s development, the authors conclude that it originated from warmer ground temperatures and an increase in unfrozen water content, leading to an increase in pressure from gas emissions from permafrost and ground ice. This conclusion is also supported by known processes in the palaeo-geography of Yamal lakes and recent studies of gas-hydrate behavior and subsea processes in gas-bearing provinces.

Methane in ground ice and frozen Quaternary deposits of Western Yamal

The content and the genesis of methane in underground ice and frozen Quaternary sediments of Western Yamal is studied. The minimum concentration of methane in frozen Quaternary deposits was found for sand: 15–100 ppm V. The maximum concentration of methane reaches 3000 ppm V in marine clays. The concentration of methane in the ice wedges is 100–700 ppm V, and in the massive ground ice can be more than 10 000 ppm V. The high content of methane in the massive ground ice we explain by migration of methane from freezing deposits into ice body during its formation. The close connection between methane concentration and organic carbon content is found.

PLEISTOCENE-HOLOCENE PALAEOENVIRONMENTAL RECORDS FROM PERMAFROST SEQUENCES AT THE KARA SEA COAST (NW SIBERIA, RUSSIA)

The Kara Sea coasts were studied using comprehensive stratigraphic and geocryological methods. The paper presents the new analytical studies of ground ice and Quaternary deposits of Western Taymyr and presents the results of spore and pollen, foraminifera, grain-size, mineralogical, geochemical, oxygen isotopic, and other analyses. Several stratigraphic- geocryological transects from Yenisey and Gydan Bays enable us to refine the stratigraphy and palaeogeographical reconstruction of the environments and freezing of Late Pleistocene- Holocene sediments. Marine sedimentation conditions during the late Kargino time (MIS3) changed to continental conditions in MIS2 and MIS1. Marine sediments were frozen syn- and epigenetically with cryotexture and ground ice formation. Ice wedges formation corresponds to the end of the Pleistocene (MIS2) and during cooler periods of the Holocene.

Estimation of atmospheric paleo-circulation based on isotope composition of ice wedges

Cryostratigraphy of frozen late-Pleistocene sediments was studied in natural exposures at the Arctic coastal area. The isotope composition of ice wedges was determined. The data base on isotope composition of syngenetic ice wedges and modern elementary ice veins was compiled for the Eurasian Arctic based on obtained data and available literature sources. Spatial distribution of the isotope composition of ice wedges, which indicates paleo-climatic conditions, was determined separately for Marine Isotope Stages (MISs) from MIS 1 to MIS 4 for the Eurasian Arctic. The pattern of this distribution has remained stable during the last 50 000 years, which indicates a stable trend in atmospheric circulation from 50 000 yr BP to the present.

Geochemistry of Plant-Soil-Permafrost System on Landslide-Affected Slopes, Yamal, Russia as an Indicator of Landslide Age

Cryogenic landslides on saline marine sediments are widely distributed in Typical tundra bioclimatic subzone of the Yamal Peninsula. Interrelation between the height and productivity of the willow tundra, and activation of cryogenic processes are discussed. It is supposed that high willow canopies are the indicators of ancient landslide activities and may serve as fundamental guide for mapping of landslides in the region. Various procedures are proposed to evaluate the relative age of the landslides. They include, study of the succession of vegetation cover, ash content in each vegetation group, groundwater and sediment chemistry on the landslide-affected slopes. It is shown that the landslide process causes desalinization of marine sediments and enriches the active layer with salts. This is an important peculiarity of cryogenic landslides in the region with saline permafrost distribution.

Permafrost aggradation and methane production in low accumulative laidas (tidal flats) of the Kara Sea

It was established that along with permafrost degradation, the processes of permafrost aggradation occur in the modern low accumulative surfaces of Kara Sea. The cycle of observation over the permafrost thermal regime was performed. The mean annual temperatire of the permafrost varies from – 3.5 to – 4.8°C; the thermal flux into the permafrost can reach 8 W/m2. The methane genesis process is realized only in the seasonally thawed layer. It was found that temperature – 4.0°C is threshold for the bacterial methane production.

Study of Plant-Soil-Permafrost System on Landslide-Affected Slopes Using Geochemical Methods on Yamal, Russia

Interrelation between the height and productivity of willow tundra, and activation of cryogenic landsliding is discussed. Cryogenic landslides on saline marine sediments in Typical tundra subzone of the Yamal Peninsula show specific features. Landslide process causes desalinization of marine sediments and enriches the active layer with salts. Landforms of the landslide-affected slopes can serve as indicators of permafrost table change, heterogeneity of saline composition of near-surface sediments.