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Titel |
Poisson-Voronoi Diagrams and the Polygonal Tundra |
VerfasserIn |
F. Cresto Aleina, V. Brovkin, S. Muster, J. Boike, L. Kutzbach, S. Zuyev |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250059994
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Zusammenfassung |
Sub-grid and small scale processes occur in various ecosystems and landscapes (e.g.,
periglacial ecosystems, peatlands and vegetation patterns). These local heterogeneities are
often important or even fundamental to better understand general and large scale properties of
the system, but they are either ignored or poorly parameterized in regional and
global models. Because of their small scale, the underlying generating processes can
be well explained and resolved only by local mechanistic models, which, on the
other hand, fail to consider the regional or global influences of those features. A
challenging problem is then how to deal with these interactions across different
spatial scales, and how to improve our understanding of the role played by local soil
heterogeneities in the climate system. This is of particular interest in the northern peatlands,
because of the huge amount of carbon stored in these regions. Land-atmosphere
greenhouse gas fluxes vary dramatically within these environments. Therefore,
to correctly estimate the fluxes a description of the small scale soil variability is
needed.
Applications of statistical physics methods could provide useful tools to upscale local
features of the landscape, relating them to large-scale properties. To test this approach we
considered a case study: the polygonal tundra. Cryogenic polygons, consisting
mainly of elevated dry rims and wet low centers, pattern the terrain of many subartic
regions and are generated by complex crack-and-growth processes. Methane, carbon
dioxide and water vapor fluxes vary largely within the environment, as an effect
of the small scale processes that characterize the landscape. It is then essential to
consider the local heterogeneous behavior of the system components, such as the
water table level inside the polygon wet centers, or the depth at which frozen soil
thaws.
We developed a stochastic model for this environment using Poisson-Voronoi diagrams,
which are able to upscale statistical large scale properties of the system taking into account
the main processes within the single polygons. We then compare the results with available
recent field studies and demonstrate that the model captures the main statistical
characteristics of the landscape and describes its dynamical behavior under climatic forcings
(e.g., precipitation and evapotranspiration). In particular, we model and analyze water table
dynamics, which directly influences greenhouse gas emissions and changes in the system.
Hydraulic interconnectivities and large-scale drainage may also be investigated
through percolation properties and thresholds in the Voronoi-Deleaunay graph. |
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