Deep ice-core drilling at the Elbrus western plateau successfully completed
Ice-core drilling at the Elbrus western plateau was started on 25th of August 2009 when all equipment, outfits and materials, total weight of 2000 kg, and personnel have been brought to the drilling site by MI-8-MTV helicopter of SIMARGL Air Company.
Because of late start of work and logistic difficulties the drilling site was shifted from zone of the thickest ice to the area of ice division between B.Azau and Kukurtlu glaciers in central part of the plateau (43°20’53,9”N, 42°25’36,0”E, altitude 5115 m asl.) (fig.1).
Fig.1. Deep ice core drilling camp.
Drilling was started on 27th August and on the afternoon of the 6th of September the drill has reached bedrock at 181,80 m depth. Drilling was accomplished by three personnel at one shift. Drilling rate was 20 m per day (10-12 hours) in average. An electromechanical ice-core drilling system developed by Geotech Co. Ltd., Nagoya, Japan was used (Fig.2).
Fig.2. Electromechanical ice-core drilling system.
Collected ice-cores after detailed stratigraphy description were packed and brought to the storage at snow pit with temperature of -10 °С (fig.3).
Fig.3. Ice core storage.
Our studies have also included: borehole temperatures measurements, snow cover researches in snow pits, snow and firn isotopic composition sampling and density measurements. For density studies special device - Speedograph – custom-designed and produced by V.S. Zagorodnov in the USA was used (fig.4). Where rate of penetration of mini thermoelectric drill is registering by a computer every 0,1 s. Drilling rate depends mainly on snow and firn density and temperature. Using Speedograph two boreholes (8 and 33 m depth) were drilled.
Temperature was measured in all boreholes using termistor sensor with 0,1°С accuracy. Temperature profiles from different boreholes are in close agreement with each other and with previous studies of 2004. Important result is a temperature profile of the deep borehole where temperature changes from -19 °С at surface to -15 °С at 110 m depth and increases fast below this level to -2,4 °С at the bedrock (fig.5).
Fig.5. Temperature profile (Mikhalenko and others, in press).
Ice-core stratigraphy and temperature data both show representativity of the drilling site for the vast firn area of the glacier where recrystallization type of ice formation prevails.
One of the most interesting results of ice-core drilling was a discovery of 40 cm layer of pyroclastic material at 107,27 depth (fig.6). This layer has a distinct upper boundary and could correspond to the tephra blowout of one of the Elbrus craters (fig.5).
Fig.6. Ice core from 107. 27 m with pyroclastic material.
Following personnel have assisted in work on western Elbrus plateau at different stages: A.A. Abramov, M.N. Ivanov, M.G. Kunakhovich, A.S. Kutuzov, S.S. Kutuzov, I.I. Lavrentiev, V.N. Mikhalenko, S.A. Marchenko, V.I. Okopny, K.E. Smirnov, A.V. Shyshkov.
This study was supported by Russian Academy of Sciences (project №16 of the program №13 Dept. of Earth Sciences RAS) and RFBR grants 07-05-00410 and 09-05-10043.
We are grateful to helicopter crew SIMARGL Air Company and personally to A.N. Semenovich and R.A. Gubzhokov. We thank also Elbrus science-educational base of the geographical faculty MSU and A.D. Oleinikov for help with field studies organization. We would like to thank Mountech official dealer of the Marmot Mountain, LLC. for providing us with quality clothing and equipment.