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The sensitivity of permafrost in the context of climate change in the Arctic

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Citation:
Langer, M. and Boike, J. (2012): The sensitivity of permafrost in the context of climate change in the Arctic , Workshop on Evolution of the Environment in Arctic Siberia, Novosibirsk, 11 May 2012 - 13 May 2012 .
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Abstract:

About 24% of the Arctic land area is underlain by permafrost with the largest areas located in Russia. The vast tundra landscapes are considered to play an important role in the Arctic ecosystem as transient storages and processors of carbon and other nutrients. In total, about 1200 to 1600 Gt C are estimated to be stored in permafrost landscapes. The stability of this massive carbon storage and other nutrient pools sensitively depends on biogeochemical conversion and exchange processes with the hydrosphere and atmosphere. Water bodies such as ponds, lakes, streams, and rives are closely related to the permafrost energy and water budget and play an integral role in the carbon cycle. In turn, these processes are largely controlled by the physical stability of permafrost which is highly vulnerable to climate change. In order to investigate the impact of climate change on Arctic ecosystems, environmental observatories which measure a comprehensive set of climatological, biochemical and hydrological parameters are highly needed. Due to the remoteness of most permafrost region satellite based permafrost monitoring is an indispensable tool for global permafrost monitoring. For most of the cryosphere components such as glaciers, ice sheets, and sea ice, satellite monitoring and change detection is well established since several decades. For permafrost, however, which represents the largest component of the Arctic cryosphere operational satellite monitoring schemes do not exist so far. One of the biggest challenges for a satellite based monitoring is that permafrost is a subsurface thermal phenomenon which cannot be directly observed by remote sensing techniques. Modeling techniques can be applied in order to bypass the limitations of satellite sensors. Multi-satellite and weather reanalysis data such as surface temperatures, snow water equivalent, and surface moisture can be assimilated into a transient permafrost model which calculates the subsurface temperature dynamics. The development and validation of such schemes require long-term meteorological and soil physical datasets which are only sparsely available in permafrost regions. Based on the established monitoring systems on Samoylov Island, first proof of concept studies for a satellite based permafrost motoring schemes are currently under investigation. So far, our investigations focus on the surface temperature, snow water equivalent, soil moisture, and thaw depth. Future investigations will include the validation of radar products which show promising results in freeze-thaw and frost heave detection from which subsurface ice contents might be inferable. In addition to past and recent change detection, permafrost has received increased attention in earth system modeling. The next generation of global climate models will include permafrost-carbon modules in order to improve climate predictions. However, the implementation of permafrost into climate models requires thorough knowledge about the physical processes determining the thermal dynamics of the frozen soils. This implies comprehensive knowledge about (i) the energy turnover at the soil-atmosphere interface and (ii) the heat transfer within the ground. In order to develop and validate permafrost schemes of modern earth system models, it is desirable to obtain regional process studies, which deliver important information about the landscape-specific energy balance characteristics and their determining factors. On Samoylov Island comprehensive energy and water balance investigation are conducted. Our studies include year around measurements of atmospheric heat and water fluxes, the radiation balance, the sub-surface heat and water flux, as well as investigations on spatial variabilities of the energy balance. With future augments the Samoylov observatory has the potential to serve as as a benchmark, validation, and development site for earth system models and satellite based permafrost monitoring.

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