Circumpolar assessment of spatial and temporal variability of permafrost temperature and active layer thickness based on data from the Global Terrestrial Network for Permafrost (GTN-P)тезисы доклада
Дата последнего поиска статьи во внешних источниках: 17 октября 2017 г.
Аннотация:Permafrost is defined as soil, rock, and any other subsurface earth
material that exists at or below 0°C continuously for two or more
consecutive years. On top of permafrost is the active layer, which thaws
during the summer and freezes again the following winter. The mean
annual temperature of permafrost and the active layer thickness (ALT)
are good indicators of changing climate and therefore designated as
essential climate variables by the Global Climate Observing System
Program of the World Meteorological Organization. Permafrost
temperature and ALT are also essential variables in designing, building
and maintaining infrastructure in the Arctic Regions, particularly in the
context of Russia. Unlike majority of the Arctic, Russian permafrost
regions have presence of substantial population and developed
infrastructure. In such cases permafrost changes due to climate are
exacerbated in areas of human activities and infrastructure development
and may have severe socio-economic consequences as negative impacts
of permafrost warming are expected to continue resulting in further
deterioration of the infrastructure if adequate measures are not taken into
account. That is why a reliable source of high quality data on permafrost
temperature and ALT under changing climatic conditions is critically
important for the sustainable development of the Arctic Regions in
general, and in Russia in particular.
The Global Terrestrial Network for Permafrost (GTN-P) provides
systematic long-term measurements of permafrost temperature and active
layer thickness (ALT), and is part of the Global Terrestrial Observing
System of the Global Climate Observing System. Long-term monitoring
of permafrost thermal state and active layer thickness generates essential
baseline information for the assessment of climate change impacts in
polar and high mountain regions and is particularly important in the
context of Russia. The GTN-P data management system (DMS,
gtnpdatabase.org) allows automatic data submission, standardization,
quality control, processing, and data access and provides opportunity to
evaluate spatial and temporal variability of permafrost temperature and
ALT at various cold regions. Presently 1350 TSP boreholes and 250
active layer sites are registered in the DMS. While the majority of
European and North American sites now feature multi-year borehole data,
ground temperature data for the majority of the Russian sites are not
available warranting further data integration from this region. Using DMS
capabilities we selected sites with data available around the last
International Polar Year and in the last five years (2010-2015) and
estimated changes in thermal state of permafrost and active layer
thickness between the two reference periods.
Permafrost temperature has generally increased across the entire
permafrost domain, which is consistent with air temperature trends. The
greatest increases in permafrost temperature are found in the High Arctic
of Canada and western Siberia and are generally pronounced in regions
with cold continuous permafrost such as Russia and North America. In
the Subarctic, where permafrost temperatures are relatively high and
within 2°C of the freezing point, there has been little change and
permafrost temperature is similar to that of the IPY snapshot. In Alpine
permafrost areas most measurement sites also show significant warming
since 2009. In Antarctica, permafrost temperature showed various trends,
depending on regional changes in atmospheric temperature and snow
accumulation.
ALT exhibits large interannual variability, but has generally
increased in the majority of regions, especially in European Arctic where
several sites experienced permafrost degradation to the degree that does
not allow to use mechanical probing to continue monitoring. In several
locations thaw penetration into the ice-rich layer rather than ALT
thickening was observed under warming climatic conditions. This
underscores the importance of thaw subsidence in understanding the
response of permafrost system to climate change.
The results reveal further need for improved geographic coverage
of the observational network, further refining of monitoring standards and
integration of other ecosystem and climatic variables in order to better
assess changes in permafrost system at global scales.