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Russian scientists offer optimal method for mapping subsea permafrost

The deposits of land-based and subsea permafrost contain remains of plants and animals as well as huge reserves of hydrocarbons, including in the form of the so-called clathrates

TASS, June 9. Russian researchers offered an optimal approach to mapping permafrost deposits, hidden on the East Siberian Sea shelf and in other Arctic coastal regions. By using this method scientists will forecast more accurately how quickly methane reserves, hidden under the permafrost, will be released, press service of the Moscow Institute of Physics and Technology (MIPT) reported on Thursday.

"Our specialists have been using actively the TDEM methods to study perennially frozen soils. We have managed to confirm as effective the technology to obtain the subsea permafrost's images in conditions of the Arctic shelf," the press service quoted the institute's Senior Researcher Dmitry Alekseev as saying. "This is extremely important to understand the current conditions of the "permafrost-hydrate" subsea system and fur future studies of the Arctic seas."

The deposits of land-based and subsea permafrost contain remains of plants and animals as well as huge reserves of hydrocarbons, including in the form of the so-called clathrates. Scientists use this notion for compressed and frozen gas hydrates, compounds of water and methane that remain stable at low temperatures, high pressure, or in their combinations.

Huge clathrate reserves got accumulated at the bottom of the Arctic seas and in the coastal areas during the glaciation era. Recently, they have begun to appear because of rising temperatures and terrain changes caused by the thawing ice cap. Thus, craters have appeared on the ocean floor and in the circumpolar lands.

Optimal approach to bottom mapping

Scientists study actively conditions of these permafrost deposits. For those studies they need new approaches to monitoring marine soil layers on a large scale. The expert and his colleagues have found that for such measurements the best was the TDEM methods, widely used in geology to study structures and properties of near-surface rock deposits on land and in the sea.

For such measurements, geologists would place above the studied area of land or sea a set of antennas and coils, through which an electric current is sent periodically. This generates reciprocal electromagnetic vibrations in the sediments, and their nature depends on their structure and composition. Thus, scientists can make 3D maps of the subsurface at depths between a few dozen centimeters to several hundred meters.

The Russian scientists have calculated that the TDEM methods suit well studies of subsea permafrost deposits located at a depth of up to 20 meters from the sea surface. According to the scientists, this restriction is explained by the fact that salty seawater conducts current well, which masks signals generated inside permafrost deposits in response to electricity pulses passing through the observation equipment.

According to the scientist and his colleagues, this is not a problem for the shallow coastal regions of the East Siberian Sea, where, presumably, about 70% of the marine permafrost reserves are concentrated. Thus, scientists may use the TDEM methods to make accurate maps showing the permafrost deposits distributed in the given Arctic area, the experts concluded.