Abstract
Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000–2010) record of summer-time energy balance components (net radiation, Rn; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G) from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD) during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (β=H/LE) compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (Ds) was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/Rn and LE/Rn and decreasing G/Rn and β, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system.
Highlights
The energy balance of northern high-latitude permafrost regions is crucial for most ecosystem processes in Arctic land areas, including permafrost thermal conditions, plant growth, microbial activity, carbon (C) and nutrient cycling, hydrology and geomorphology
Regional and local climate are strongly influenced by surface energy partitioning (Eugster et al, 2000), and changes in energy balance partitioning may feedback on the climate system (Chapin et al, 2005)
In this study, using an extensive data set from a high Arctic heath site in Zackenberg, NE Greenland, we observed an increased partitioning of available energy into H and LE, and decreased partitioning into G, between 2000 and 2010
Summary
The energy balance of northern high-latitude permafrost regions is crucial for most ecosystem processes in Arctic land areas, including permafrost thermal conditions, plant growth, microbial activity, carbon (C) and nutrient cycling, hydrology and geomorphology. Changes in Arctic energy balance partitioning may by itself induce further feedback effects on the local and global climate system (Chapin et al, 2005). Observations from circumpolar Arctic permafrost monitoring sites reveal increasing permafrost temperatures (Osterkamp, 2005; Akerman and Johansson, 2008; Christiansen et al, 2010; Romanovsky et al, 2010). Dependent upon site specific conditions in permafrost and hydrological regimes increasing active layer depths (ALD) and permafrost thawing may lead to wetter (Johansson et al, 2006) or dryer (Oechel et al, 1993) soil conditions. The observed increase in shrub growth and associated increases in vegetation greenness and productivity across the circumpolar north creativecommons.org/licenses/by/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license
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