New oxygen isotope diagrams of late pleistocene and holocene ice wedges of Mamontova Gora and Syrdah Lake, Central Yakutia

The aim of the study was to obtain the data of stable oxygen isotope composition of Late Pleistocene and Holocene ice wedges of Mamontova Gora and Syrdakh exposures and their chronology, and reconstruction of winter air temperature during the time of ice wedge formation. Direct dating of organic microinclusions from the ice wedges of Mamontova Gora outcrops allowed to establish that the ice wedges are younger than 20 ka, but older than 10 ka BP. δ18O values of the Late Pleistocene ice wedges of Mamontova Gora vary from -24.7 to -30.9 ‰, δ18O values of the Holocene ice wedges of this exposures range from -23.2 to -25.9 ‰. δ18O values in the Late Pleistocene ice wedges near Syrdakh Lake vary from -29.2 to -32.5 ‰. Reconstructed mean winter air temperature during the most part of the ice wedge growth period in Mamontova Gora site within Late Pleistocene varied from -28 to - 31°C, mean January temperature reached -42, -46°C, for the Syrdakh Lake site Late Pleistocene winter conditions were more severe: mean winter air temperature varied from -30 to -32°C, mean January air temperature reached -44, -48°C. Holocene mean winter air temperature were higher and varied from -24 to - 28°C, mean January temperature varied from -36 to -42°C.

Lake water and talik groundwater interaction in continuous permafrost, Central Yakutia

Structural features of a lake talik associated with eolian relief are discussed. Analysis of hydrochemical and hydrological data for 2010-2017 showed that talik groundwater feeds lake and maintains perennial outflow from the lake. Variations in the chemical composition of the lake and outflowing creek are characterized on an annual and interannual basis. Seasonal comparison of hydrochemical data indicates a downward trend in dissolved-solids content of the lake water over the last six years, suggesting an increasing contribution of suprapermafrost groundwater to the lake and lake talik. Probable reason of enhanced suprapermafrost flow is increase of its duration due to observed rise of winter air temperature.

Winter Nocturnal Air Temperature Distribution for a Mesoscale Plain of a Snow-Covered Region: Field Meteorological Observations and Numerical Simulations

Winter air temperatures strongly affect crop overwintering and cold resource usage. To clarify how winter air temperature distributions are formed in a mesoscale plain, field observations and simulations were conducted for the Tokachi region in Japan. Results elucidating the winter climate within the plain revealed that the winter mean air temperature at each site was correlated closely with the mean daily minimum air temperature. The daily minimum air temperature was not correlated with altitude, suggesting that local variation of the daily minimum temperature influences the temperature distribution. Observations at different distances from the upwind mountains revealed that nocturnal air temperatures were higher for stronger winds closer to the mountain foot. Low temperatures associated with wind speed suggest that radiative cooling strongly affects the temperature distribution. Wind and temperature conditions in the boundary layer influence the degree of drop in nocturnal air temperature and its distribution. The wind speed and direction, respectively, affect the extent and direction of the high-temperature zone from the northwest mountain foot. Simulations with a spatial resolution of 2 km reproduced the observed temperatures, but the error exceeded 5°C at sites having complex terrain under moderate or strong wind conditions. A higher-resolution model of 0.5 km showed that simulated temperatures approach the observed temperatures in association with a local wind system of down-valley drainage flow. In conclusion, the synoptic background, wind strength and direction over the plain, and microscale valleys affect boundary layer mixing and, thereby, determine the winter air temperature distribution.