Scientists use fibre optic cable to study Arctic seafloor permafrost. The approach was developed by American geophysicists and climatologists.
The US scientists at Sandia National Laboratories have developed an approach that allows the use of already existing submarine fibre optic cables to study the conditions of the Arctic seafloor, to conduct continuous observations of the state of submarine permafrost, including its temperature and generated methane emissions.
One of the innovations of this project is that we can now use a single fibre to get acoustic and temperature data. We developed a new system to remotely collect both types of data using one fibre strand. We're getting some interesting results, project lead said.
Permafrost deposits at the bottom of the Arctic Ocean contain not only the remains of flora and fauna, but also large amounts of clathrates, compressed and frozen compounds of water and methane that remain stable at low temperatures, high pressures, or a combination of both.
The scientists at Sandia National Laboratories have developed an approach that will allow scientists to monitor the temperature in these sediments, as well as detect episodes of abrupt methane release as a result of clathrate destabilisation. For this purpose, it is possible to use already existing submarine telecommunications fibre optic cables laid on the bottom of the Arctic Ocean and the circumpolar regions of the Atlantic and Pacific Oceans.
According to the scientists, to obtain information, it is enough to pass two laser beams at different wavelengths through the fibre optic cable and watch how the spectrum of their radiation changes as they move through the cable. By tracking shifts in the spectrum, it is possible to calculate the temperature at the bottom of the sea, as well as to catch fluctuations generated by the explosive release of methane or by other changes in the topography and structure of the Arctic Ocean seafloor.
The scientists tested this approach on a fibre optic cable that is laid off the northern coast of Alaska near the Oliktok radar station. Using the cable, the scientists were able to measure Arctic Ocean bottom temperatures at a distance of 28-35 km from the shore, discover previously unknown deposits of submarine permafrost in this polar region, and detect cone-shaped ice accumulations rising from the depths of the ground.
The fact that we can monitor the temperature continuously, we can now pick up changes from year-to-year and season-to-season. We're specifically looking for unexplainable warm spots. We think we'll be able to see areas of seafloor seeps—somewhat like springs coming out of the ground, except on the seafloor. We're interested in them because they're carriers of deeper, carbon-rich fluids and are an indication of warming and change, Sandia National Laboratories researcher, a computational geoscientist, summarised.