Some Observations of Ice Features in the North Caspian Sea

Observations of stamukhi, stamukhi/seabed interaction, and pressure ridges were made in the North Caspian Sea during February 2010. The primary focus of the field programme was to provide information on the frequency and dimensions of seabed disturbances (pits) that form underneath stamukhi, as these may need to be considered in the design of offshore pipelines and other seabed installations in the region. A hot water “thermal drill” was used to penetrate the ice in the stamukhi sails and keels and a pressure transducer was lowered down the thermal drill holes to measure the depth of the seabed below the water level. Transects with holes spaced at 2.5m intervals were conducted to characterize the features, and to identify areas of special interest where additional holes were drilled on 1m × 1m grids. The data provide statistical information on pit depth, width and frequency. The observations also provided some information on where the deepest pits tend to form, which in turn provided some insights into the pit formation mechanism. A small number of observations of pressure ridge sail and consolidated layer properties were also made. These revealed that in at least some instances the consolidated layer of the ridges can be made up of rafted ice. It was also observed that there were almost no ice blocks under the consolidated layers, so that despite having normal looking sails, in effect the ridges did not have ‘keels’.