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| Titel |
Severity of climate change dictates the direction of biophysical feedbacks of vegetation change to Arctic climate |
| VerfasserIn |
Wenxin Zhang, Christer Jansson, Paul Miller, Ben Smith, Patrick Samuelsson |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095852
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| Publikation (Nr.) |
 EGU/EGU2014-11327.pdf |
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| Zusammenfassung |
| Vegetation-climate feedbacks induced by vegetation dynamics under climate change alter
biophysical properties of the land surface that regulate energy and water exchange with the
atmosphere. Simulations with Earth System Models applied at global scale suggest that the
current warming in the Arctic has been amplified, with large contributions from
positive feedbacks, dominated by the effect of reduced surface albedo as an increased
distribution, cover and taller stature of trees and shrubs mask underlying snow, darkening
the surface. However, these models generally employ simplified representation of
vegetation dynamics and structure and a coarse grid resolution, overlooking local or
regional scale details determined by diverse vegetation composition and landscape
heterogeneity.
In this study, we perform simulations using an advanced regional coupled vegetation-climate
model (RCA-GUESS) applied at high resolution (0.44x0.44°) over the Arctic Coordinated
Regional Climate Downscaling Experiment (CORDEX-Arctic) domain. The climate
component (RCA4) is forced with lateral boundary conditions from EC-EARTH CMIP5
simulations for three representative concentration pathways (RCP 2.6, 4.5, 8.5).
Vegetation-climate response is simulated by the individual-based dynamic vegetation model
(LPJ-GUESS), accounting for phenology, physiology, demography and resource competition
of individual-based vegetation, and feeding variations of leaf area index and vegetative cover
fraction back to the climate component, thereby adjusting surface properties and surface
energy fluxes. The simulated 2m air temperature, precipitation, vegetation distribution
and carbon budget for the present period has been evaluated in another paper. The
purpose of this study is to elucidate the spatial and temporal characteristics of the
biophysical feedbacks arising from vegetation shifts in response to different CO2
concentration pathways and their associated climate change. Our results indicate that the
albedo feedback dominates simulated warming in spring in all three scenarios, while
in summer, evapotranspiration feedback, governing the partitioning of the return
energy flux from the surface to the atmosphere into latent and sensible heat, exerts
evaporative cooling effects, the magnitude of which depends on the severity of
climate change, in turn driven by the underlying GHG emissions pathway, resulting in
shift in the sign of net biophysical at higher levels of warming. Spatially, western
Siberia is identified as the most susceptible location, experiencing the potential to
reverse biophysical feedbacks in all seasons. We further analyze how the pattern of
vegetation shifts triggers different signs of net effects of biophysical feedbacks. |
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