Characteristics of summer-time energy exchange in a high Arctic tundra
                        heath 2000–2010

Lund, Magnus; Hansen, Birger Ulf; Pedersen, Stine Højlund; Stiegler, Christian; Tamstorf, Mikkel P.

doi:10.3402/tellusb.v66.21631

Cited by 32 publications

(52 citation statements)

References 75 publications

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“…An increase in sensible heat flux rates as a response to shifts in the partitioning of the available net radiation is the most direct pathway to change the temperature of the atmospheric boundary layer Lund et al, 2014). This statement is supported by Chapin et al (2000), who expect a high potential for positive feedbacks between land-atmosphere energy exchange and regional temperature changes throughout high-latitude regions, disregarding potential shifts in land cover structure.…”

Section: Implications For Arctic Climate Changementioning

confidence: 49%

“…Within permafrost landscapes, a large portion of the net energy input from radiation is used to thaw the frozen ground, and increase the thaw depth over the course of the growing season (e.g., Lund et al, 2014). Permafrost constitutes a substantial heat sink, reducing the soil temperatures and also the energy available to feed turbulent heat flux exchange with the atmosphere Langer et al, 2011a).…”

Section: Impact Of Permafrostmentioning

confidence: 99%

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Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

et al. 2017

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Abstract. Hydrologic conditions are a key factor in Arctic ecosystems, with strong influences on ecosystem structure and related effects on biogeophysical and biogeochemical processes. With systematic changes in water availability expected for large parts of the northern high-latitude region in the coming centuries, knowledge on shifts in ecosystem functionality triggered by altered water levels is crucial for reducing uncertainties in climate change predictions. Here, we present findings from paired ecosystem observations in northeast Siberia comprising a drained and a control site. At the drainage site, the water table has been artificially lowered by up to 30 cm in summer for more than a decade. This sustained primary disturbance in hydrologic conditions has triggered a suite of secondary shifts in ecosystem properties, including vegetation community structure, snow cover dynamics, and radiation budget, all of which influence the net effects of drainage. Reduced thermal conductivity in dry organic soils was identified as the dominating drainage effect on energy budget and soil thermal regime. Through this effect, reduced heat transfer into deeper soil layers leads to shallower thaw depths, initially leading to a stabilization of organic permafrost soils, while the long-term effects on permafrost temperature trends still need to be assessed. At the same time, more energy is transferred back into the atmosphere as sensible heat in the drained area, which may trigger a warming of the lower atmospheric surface layer.

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Section: Implications For Arctic Climate Changementioning

confidence: 49%

Section: Impact Of Permafrostmentioning

confidence: 99%

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

et al. 2017

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“…Values fitted for A, S and B were 0.31, 10 800 and 74 000, respectively. Although c G values for Arctic tundra were not found in the literature, several studies (Beringer et al, 2005;Eugster et al, 2000Eugster et al, , 2005Boike et al, 2008b;Eaton et al, 2001;Kodama et al, 2007;Langer et al, 2011;Soegaard et al, 2001;Westermann et al, 2009;Mendez et al, 1998;Lund et al, 2014) present the relationship between R N s and G during the summer months in similar tundra areas. According to these studies, a mean value of 0.14, as a maximum value of c G in Eq.…”

Section: Refinements In Soil Heat Flux Parameterization: C G Coefficimentioning

confidence: 98%

“…Alternatively, measurements of bulk (soil plus canopy) for Arctic tundra systems are available (Beringer et al, 2005;Eaton et al, 2001;Eugster et al, 2005;Engstrom et al, 2002;Mendez et al, 1998;Lund et al, 2014), suggesting a mean value of around 0.92. This bulk value might suggest that α PTC could also be lower for Alaska tundra summer conditions.…”

Section: Priestley-taylor Coefficientmentioning

confidence: 99%

Estimation of surface energy fluxes in the Arctic tundra using the remote sensing thermal-based Two-Source Energy Balance model

Cristóbal

Prakash

Anderson

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. The Arctic has become generally a warmer place over the past decades leading to earlier snow melt, permafrost degradation and changing plant communities. Increases in precipitation and local evaporation in the Arctic, known as the acceleration components of the hydrologic cycle, coupled with land cover changes, have resulted in significant changes in the regional surface energy budget. Quantifying spatiotemporal trends in surface energy flux partitioning is key to forecasting ecological responses to changing climate conditions in the Arctic. An extensive local evaluation of the Two-Source Energy Balance model (TSEB) -a remotesensing-based model using thermal infrared retrievals of land surface temperature -was performed using tower measurements collected over different tundra types in Alaska in all sky conditions over the full growing season from 2008 to 2012. Based on comparisons with flux tower observations, refinements in the original TSEB net radiation, soil heat flux and canopy transpiration parameterizations were identified for Arctic tundra. In particular, a revised method for estimating soil heat flux based on relationships with soil temperature was developed, resulting in significantly improved performance. These refinements result in mean turbulent flux errors generally less than 50 W m −2 at half-hourly time steps, similar to errors typically reported in surface energy balance modeling studies conducted in more temperate climatic regimes. The MODIS leaf area index (LAI) remote sensing product proved to be useful for estimating energy fluxes in Arctic tundra in the absence of field data on the local biomass amount. Model refinements found in this work at the local scale build toward a regional implementation of the TSEB model over Arctic tundra ecosystems, using thermal satellite remote sensing to assess response of surface fluxes to changing vegetation and climate conditions.

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“…To ensure that the eddy covariance measurements capture all scales of mixed-layer turbulence, cospectral analysis (Wyngaard and Cote, 1972) between the vertical wind velocity and turbulent energy flux was performed at both study locations. Data processing for both study locations is further summarized in Soegaard et al (2001) and Lund et al (2012Lund et al ( , 2014.…”

Section: Measurementsmentioning

confidence: 99%

Two years with extreme and little snowfall: effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

et al. 2016

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Abstract. Snow cover is one of the key factors controlling Arctic ecosystem functioning and productivity. In this study we assess the impact of strong variability in snow accumulation during 2 subsequent years (2013-2014) on the landatmosphere interactions and surface energy exchange in two high-Arctic tundra ecosystems (wet fen and dry heath) in Zackenberg, Northeast Greenland. We observed that recordlow snow cover during the winter 2012/2013 resulted in a strong response of the heath ecosystem towards low evaporative capacity and substantial surface heat loss by sensible heat fluxes (H ) during the subsequent snowmelt period and growing season. Above-average snow accumulation during the winter 2013/2014 promoted summertime ground heat fluxes (G) and latent heat fluxes (LE) at the cost of H . At the fen ecosystem a more muted response of LE, H and G was observed in response to the variability in snow accumulation. Overall, the differences in flux partitioning and in the length of the snowmelt periods and growing seasons during the 2 years had a strong impact on the total accumulation of the surface energy balance components. We suggest that in a changing climate with higher temperature and more precipitation the surface energy balance of this high-Arctic tundra ecosystem may experience a further increase in the variability of energy accumulation, partitioning and redistribution.

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Characteristics of summer-time energy exchange in a high Arctic tundra heath 2000–2010

Cited by 32 publications

References 75 publications

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

Estimation of surface energy fluxes in the Arctic tundra using the remote sensing thermal-based Two-Source Energy Balance model

Two years with extreme and little snowfall: effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

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