Internal structure of ice ridges and stamukhas based on thermal drilling data

During the resent years (1996–2005) the Arctic and Antarctic Research Institute performed expeditionary research in marginal seas. One of the tasks consisted in the determination of morphometric characteristics of ice ridges and stamukhas with the help of thermodrilling, with recording of the rate using a computer. The record of the penetration rate of the thermodrill and the water column pressure in the borehole as a function of depth, as well as processing of the recorded data, enabled to get information about the boundaries of consolidated layer. Principles of interpretation of the records of penetration rate of the thermodrill are discussed. Depth-wise distribution of volume content of solid phase of ice is presented for ice ridges and stamukhas in the various regions. Methodological grounds are discussed, of the determination of this distribution, based on the results of averaging of the data obtained through thermodrilling. Internal structure of ice ridges and stamukhas is discussed, for the Pechora Sea, the Sea of Okhotsk, the Caspian Sea, the Sea of Azov and near-polar district of Arctic basin, as well as its consideration with respect to other literary sources. Based on the accomplished analysis of the internal structure of ice ridges and stamukhas of the shelf of the Sakhalin Island and the Pechora Sea, a conclusion was made, that the thickness of consolidated layer determined based on the rate of drilling, according to subjective perception of the operator, frequently proves to be overestimated. The ratio between average thickness of consolidated layer of ice ridges and average thickness of level ice which surrounds the same in the regions in question varies within the range of 0.83…1.63, about 1.2 on the average. For stamukhas this ratio varies within the range of 1.3…2.1, about 1.7 on the average. Average porosity of the investigated ice ridges varies within the range of 12–28%, of the stamukhas — 7–20%.