During the period between April and September 2017, two expeditions took place in the Laptev Sea and Lena River Delta areas of northern Yakutia, northeast Siberia, Russia, in cooperation with Russian colleagues and researchers from German Universities. One of the goals of these expeditions was to evaluate techniques and instrumentation that will be used in the development for mobile measurement systems for the Rapid Permafrost Thaw topic in MOSES. Fieldwork activities took place along the coast and on the Samoylov Island, the latter of which has been a base for joint Russian-German research since 1998. The joint Russian-German “LENA” research expeditions are coordinated by the AWI, the Arctic and Antarctic Research Institute in St. Petersburg, as well as the Melnikov Permafrost Institute in Yakutsk. The LENA expedition team has also been running continuous climate and soil measurements at this site since 1998 and multi-year Eddy covariance and hydrological stations since 2002. Since 2013, the LENA expeditions have been using the new Russian Research Station “Samoylov Island” operated by the Trofimuk Institute of Petroleum Geology and Geophysics in Novosibirsk. The rich history of measurements and existing long-term measurement stations make this location an ideal testbed for the development of mobile measurement platforms and the testing of new instrumentation and techniques.
Rates of Permafrost Degradation along the Coast Line and at the Land Surface
The first expedition focused on interactions between water bodies and permafrost along the coast of the central Laptev Sea. By connecting observations from the boreholes with geophysical surveys, the spatial distribution of permafrost beneath an incipient thermokarst lake and a thermokarst lake (Lake Goltsovoe), a saltwater lake within a drained freshwater lake basin (Polar Fox Lake), a coastal lagoon (Uomullyakh Lagoon Lagoon) and in front of the coast can be analysed. Geophysical techniques included electrical resistivity tomography, ground-penetrating radar, and passive seismic. The analysis of multi-temporal remote sensing data provides a temporal context for the expansion of thermokarst water bodies, the progress of coastal erosion, as well as the sediment transport and rates of permafrost aggradation and degradation. The degradation of subaquatic permafrost itself depends on the duration of inundation, warming rate, the coupling of the bed to the atmosphere from bottom-fast ice, the salinity of the water, and brine injections into the seabed. Our objectives were to i) measure the distribution of permafrost-relevant geophysical parameters beneath water bodies representing various stages in the transition of terrestrial to subaquatic permafrost, which will allow us to quantify rates of permafrost degradation (Figure 1) and ii) measure and apply above-water and water column radiometric measurements for the evaluation of satellite ocean colour products (Figure 2). The latter, combined with analyses of surface water for its constituents, will help us to understand how the optical properties of different water masses relate to processes integral to shelf ecosystem and oceanography. In situ concentrations of different biogeochemical water constituents, as well as above-water and in-water reflectance measurements will combine within radiative transfer simulations to improve the retrieval of the optical water properties via remote sensing data.
Areas of Rapid Permafrost Thaw and “CO2 Hot Spots”
The second expedition focused on the collection of very high-resolution topographic information that could be used to detect the rapid thaw of ice-rich permafrost, followed by settling of the ground surface. The team conducted a survey of the ground surface using the terrestrial laser scanning (TLS) technique. The team successfully captured in-situ 3D geodata for various sites on Samoylov Island and the nearby island of Kurungnakh, where research focused on the dynamically changing permafrost system.
The high-precision 3D point cloud data is needed obtain information on micro-topographic and vegetation characteristics of different landscape units. Moreover, the captured data provides a valuable baseline for a timeseries of 3D geodata for long-term analyses and observation of permafrost-related processes in this Arctic tundra environment. In addition to TLS, a close-range photogrammetric approach, Structure from Motion (SfM), to represent permafrost features in 3D will be tested using large sets of images captured on site with regular digital cameras.
Additional field experiments were carried out this year from July to September to test waterproof CO2 concentration probes. These probes were tested for continuous in situ monitoring of CO2, as well as for spatial distributed sampling of CO2 concentrations in several water bodies on Samoylov. First results show very high CO2 concentrations in these water bodies, suggesting that these ponds can be considered “CO2 hot spots”.
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