Pulsations of optical radiation during the flare of YZ CMi occurred on February 9, 2008

One of the most powerful and long-lived flares on the active red dwarf YZ CMi is considered. The flare was observed in the U band at the Terskol Peak Observatory on February 9, 2008. During the formation of the flare over the course of 30 seconds, the flare-induced stellar luminosity increased and became more than 180 times the preflare value. The total duration of the flare was approximately one hour. At the flare maximum, quasi-periodic pulsations having a specified period of approximately 11 s, an initial modulation depth of 5.5%, and an exponential damping time of 29 s were discovered using wavelet analysis. Assuming that the pulsations were caused by fast magnetohydrodynamic oscillations of a flare loop, the following parameters were determined in the region of energy release using coronal seismology methods: plasma concentration (2 × 10¹⁰ cm⁻³), temperature (3 × 10⁷ K), and magnetic field strength (0.015 T).     

A photometric study of the polar MT draconis in 2005–2009

We have obtained data on various brightness states of the polar MT Dra over five years of observations, including the first multicolor photometry for this close binary. We confirm the known orbital period, which has remained constant over 17 years, which is unusual for cataclysmic binaries. Our observations in October 2006 demonstrated a transition of the polar to its low brightness state within one day.     

Excess CO2 and pHexcess in the Intermediate Water Layer of the Northwestern Pacific

Excess CO₂ and pH_excess showing an increase in dissolved inorganic carbon and a decrease in pH from the beginning of the industrial epoch (middle of the 19th century) until the present time have been calculated in the intermediate water layer of the northwestern Pacific and the Okhotsk Sea. It is concluded that: (1) The Kuril Basin (Okhotsk Sea) and the Bussol' Strait areas are characterized by the greatest concentrations of excess CO₂ at isopycnal surfaces due to the processes of formation and transformation of intermediate water mass. (2) The largest difference in excess CO₂ concentration between the Okhotsk Sea and the western subarctic Pacific (about 8 µmol/kg) is found at the = 27.0. (3) The difference in excess CO₂ between the western subarctic Pacific and subtropical regions is significant only in the upper part of the intermediate water layer ( = 26.7–27.0). (4) About 10% of the excess CO₂ accumulation in the subtropical north Pacific is determined by water exchange with the subarctic Pacific and the Okhotsk Sea.     

Environmental changes on Yugorski Peninsula, Kara Sea, Russia, during the last 12,800 radiocarbon years

New pollen and radiocarbon data from an 8.6-m coastal section, Cape Shpindler (69°43′N; 62°48′E), Yugorski Peninsula, document the latest Pleistocene and Holocene environmental history of this low Arctic region. Twelve AMS ¹⁴C dates indicate that the deposits accumulated since about 13,000 until 2000 radiocarbon years BP. A thermokarst lake formed ca. 13,000–12,800 years BP, when scarce arctic tundra vegetation dominated the area. By 12,500 years BP, a shallow lake existed at the site, and Arctic tundra with Poaceae, Cyperaceae, Salix, Saxifraga, and Artemisia dominated nearby vegetation. Climate was colder than today. Betula nana became dominant during the Early Preboreal period about 9500 years BP, responding to a warm event, which was one of the warmest during the Holocene. Decline in B. nana and Salix after 9500 years BP reflects a brief event of Preboreal cooling. A subsequent increase in Betula and Alnus fruticosa pollen percentages reflects amelioration of environmental conditions at the end of Preboreal period (ca. 9300 years BP). A decline in arboreal taxa later, with a dramatic increase in herb taxa, reflects a short cold event at about 9200 years BP. The pollen data reflect a northward movement of tree birch, peaking at the middle Boreal period, around 8500 years BP. Open Betula forest existed on the Kara Sea coast of the Yugorski Peninsula during the Atlantic period (8000–4500 years BP), indicating that climate was significantly warmer than today. Deteriorating climate around the Atlantic–Subboreal boundary (ca. 4500 years BP) is recorded by a decline in Betula percentages. Sedimentation slowed at the site, and processes of denudation and/or soil formation started at the beginning of the Subatlantic period, when vegetation cover on Yugorski Peninsula shifted to near-modern assemblages.     

The fauna of the Aral Sea in 1989. 2. The zooplankton

Data are presented on the composition and biomass of the Aral Sea zooplankton in August and October, 1989. As salinity gradually increased, a decrease in zooplankton species composition occurred at a salinity of 25–30 g L⁻¹. Because the Aral has now divided into two water-bodies, the zooplankton communities in these lakes have begun to conform with their individual hydrological and biological regimes.     

Interpretation of experimental data on HF propagation on the St. Petersburg-Spitsbergen path

The experimental ionograms of the oblique-incidence sounding of the ionosphere, obtained on the St. Petersburg-Spitsbergen high-latitude HF radio path during the magnetically quiet period December 14–15, 2001, are compared with the model calculations of radiowave trajectories. For this purpose, the corresponding oblique-incidence ionograms are numerically synthesized using the technique based on the shooting method and the computer program for constructing HF radiowave trajectories. The three-dimensional electron density distribution, calculated using the mathematical model of the high-latitude ionosphere previously developed at the Polar Geophysical Institute (PGI), is used to model radio propagation. The numerical calculations make it possible mainly to explain the specific features of the experimental data on the oblique-incidence sounding of the ionosphere.     

Paleontological records indicate the occurrence of open woodlands in a dry inland climate at the present-day Arctic coast in western Beringia during the Last Interglacial

Permafrost records, accessible at outcrops along the coast of Oyogos Yar at the Dmitry Laptev Strait, NE-Siberia, provide unique insights into the environmental history of Western Beringia during the Last Interglacial. The remains of terrestrial and freshwater organisms, including plants, coleopterans, chironomids, cladocerans, ostracods and molluscs, have been preserved in the frozen deposits of a shallow paleo-lake and indicate a boreal climate at the present-day arctic mainland coast during the Last Interglacial. Terrestrial beetle and plant remains suggest the former existence of open forest-tundra with larch (Larix dahurica), tree alder (Alnus incana), birch and alder shrubs (Duschekia fruticosa, Betula fruticosa, Betula divaricata, Betula nana), interspersed with patches of steppe and meadows. Consequently, the tree line was shifted to at least 270 km north of its current position. Aquatic organisms, such as chironomids, cladocerans, ostracods, molluscs and hydrophytes, indicate the formation of a shallow lake as the result of thermokarst processes. Steppe plants and beetles suggest low net precipitation. Littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation. Many of the organisms are thermophilous, indicating a mean air temperature of the warmest month that was greater than 13 °C, which is above the minimum requirements for tree growth. These temperatures are in contrast to the modern values of less than 4 °C in the study area. The terrestrial and freshwater organism remains were found at a coastal exposure that was only 3.5 m above sea level and in a position where they should have been under sea during the Last Interglacial when the global sea level was 6–10 m higher than the current levels. The results suggest that during the last warm stage, the site was inland, and its modern coastal situation is the result of tectonic subsidence.     

Holocene environments and climate in the Mongolian Altai reconstructed from the Hoton-Nur pollen and diatom records: a step towards better understanding climate dynamics in Central Asia

This study presents the results of the palynological and diatom analyses of the sediment core recovered in Hoton-Nur Lake (48°37′18″N, 88°20′45″E, 2083 m) in 2004. Quantitative reconstruction of the Holocene vegetation and climate dynamics in the semiarid Mongolian Altai suggests that boreal woodland replaced the primarily open landscape of northwestern Mongolia at about 10 kyr BP (1 kyr = 1000 cal yr) in response to a noticeable increase in precipitation from 200–250 mm/yr to 450–550 mm/yr. A decline of the forest vegetation and a return to a predominance of open vegetation types occurred after 5 kyr BP when precipitation sums decreased to 250–300 mm/yr. Prior to 11.5 kyr BP diatom concentrations are relatively low and the lake is dominated by planktonic Cyclotella and small Fragilariaceae, suggesting the existence of a relatively deep and oligotrophic/mesotrophic lake. The great abundance of Staurosirella pinnata from the beginning of the record until 10.7 kyr BP might imply intensified erosion processes in the catchment and this is fully consistent with the presence of scarce and dry vegetation and the generally arid climate during this period. From about 10.7 kyr BP, more planktonic diatom taxa appeared and increased in abundance, indicating that the lake became more productive as diatom concentration increased. This change correlates well with the development of boreal woodland in the catchment. Decrease in precipitation and changes in the vegetation towards steppe are reflected by the rapid increase in Aulacoseira distans from about 5 kyr BP. The Holocene pollen and diatom records do not indicate soil and vegetation cover disturbances by the anthropogenic activities, implying that the main transformations of the regional vegetation occurred as a result of the natural climate change. Our reconstruction is in agreement with the paleomonsoon records from China, demonstrating an abrupt strengthening of the summer monsoon at 12 kyr BP and an associated increase in precipitation and in lake levels between 11 and 8 kyr BP, followed by the stepwise attenuation of the monsoon circulation and climate aridization towards the modern level. The records from the neighboring areas of Kazakhstan and Russia, situated west and north of Hoton-Nur, demonstrate spatially and temporally different Holocene vegetation and climate histories, indicating that the Altai Mountains as a climate boundary are of pivotal importance for the Holocene environmental and, possibly, habitation history of Central Asia.     

Middle Weichselian environments on western Yamal Peninsula, Kara Sea based on pollen records

Pollen data from two sections from a coastal cliff on the western Yamal Peninsula (69°43.27′N, 66°48.80′E) document the environmental history during the Karginsky (Middle Weichselian) interstadial. Low pollen concentrations, high amounts of redeposited pollen, and relatively high presence of Artemisia pollen characterize sediments deposited at about 33,000 ¹⁴C yr B.P. Grass-sedge plant associations with few other herbs occupied the area during the late Karginsky interstadial. Artemisia pollen may indicate rather xerophytic vegetation and disturbed soils in the area. The dominance of redeposited pollen reflects scarce (disturbed) vegetation cover and low pollen productivity. The climate was relatively cold and dry. Sediments dated to 32,400 ¹⁴C yr B.P. contain fewer redeposited pollen and concentration of non-redeposited pollen is significantly higher. Pollen contents indicate the dominance of tundra-like grass-sedge vegetation and more humid conditions. Pollen records dated between 30,100 and 25,100 ¹⁴C yr B.P. also reflect scarce tundra-like vegetation during this interval. The presence of Betula nana and Salix pollen may reflect limited presence of shrub communities. This suggests that the climate was somewhat warmer during the latter part of the interstadial. However, generally the pollen records show that harsh environmental conditions prevailed on the Yamal Peninsula during the Karginsky interstadial.