New permafrost is forming around shrinking Arctic lakes, but will it last?

Briggs, Martin A.; Walvoord, M. A.; McKenzie, Jeffrey M.; Voss, Clifford I.; Day‐Lewis, Frederick D.; Lane, John W.

doi:10.1002/2014gl059251

Cited by 61 publications

(49 citation statements)

References 32 publications

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“…The soil heat flux, on the other hand, depended strongly on soil thermal properties. This is in contrast to the studies by Blok et al (2010) and Briggs et al (2014), which identified soil shading as important control of local permafrost thaw. A schematic of the differences we found between key components of the dwarf shrub and wet sedge system can be found in Fig.…”

Section: Discussioncontrasting

confidence: 99%

Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

et al. 2016

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Abstract. Vegetation changes, such as shrub encroachment and wetland expansion, have been observed in many Arctic tundra regions. These changes feed back to permafrost and climate. Permafrost can be protected by soil shading through vegetation as it reduces the amount of solar energy available for thawing. Regional climate can be affected by a reduction in surface albedo as more energy is available for atmospheric and soil heating. Here, we compared the shortwave radiation budget of two common Arctic tundra vegetation types dominated by dwarf shrubs (Betula nana) and wet sedges (Eriophorum angustifolium) in North-East Siberia. We measured time series of the shortwave and longwave radiation budget above the canopy and transmitted radiation below the canopy. Additionally, we quantified soil temperature and heat flux as well as active layer thickness. The mean growing season albedo of dwarf shrubs was 0.15 ± 0.01, for sedges it was higher (0.17±0.02). Dwarf shrub transmittance was 0.36 ± 0.07 on average, and sedge transmittance was 0.28 ± 0.08. The standing dead leaves contributed strongly to the soil shading of wet sedges. Despite a lower albedo and less soil shading, the soil below dwarf shrubs conducted less heat resulting in a 17 cm shallower active layer as compared to sedges. This result was supported by additional, spatially distributed measurements of both vegetation types. Clouds were a major influencing factor for albedo and transmittance, particularly in sedge vegetation. Cloud cover reduced the albedo by 0.01 in dwarf shrubs and by 0.03 in sedges, while transmittance was increased by 0.08 and 0.10 in dwarf shrubs and sedges, respectively. Our results suggest that the observed deeper active layer below wet sedges is not primarily a result of the summer canopy radiation budget. Soil properties, such as soil albedo, moisture, and thermal conductivity, may be more influential, at least in our comparison between dwarf shrub vegetation on relatively dry patches and sedge vegetation with higher soil moisture.

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Section: Discussioncontrasting

confidence: 99%

Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

et al. 2016

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“…Lastly there is the challenge of quantifying “hot spots and moments” and “effective discharge” for biogeochemical processing of nutrients and organic matter in watersheds to understand river corridor functions and [e.g., McClain et al ., ; Doyle et al ., ]. We review the history and progress in these and other river corridor concepts and we also review the tried and true field practices with a view toward emerging techniques such as novel applications of geophysical techniques [ Briggs et al ., ; Lowry et al ., ], thermal imaging [e.g., Dugdale et al ., ; Briggs et al ., b], and satellite observations [e.g., Alsdorf et al ., ; Townsend and Foster , ]. Practical examples relating to management of river corridors are considered, such as concepts to quantify and characterize the chemical reactions of major concern and their relation to practical aspects of the conjunctive management of surface and groundwater management (e.g., bank filtration).…”

Section: Introductionmentioning

confidence: 99%

River corridor science: Hydrologic exchange and ecological consequences from bedforms to basins

2015

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Previously regarded as the passive drains of watersheds, over the past 50 years, rivers have progressively been recognized as being actively connected with off‐channel environments. These connections prolong physical storage and enhance reactive processing to alter water chemistry and downstream transport of materials and energy. Here we propose river corridor science as a concept that integrates downstream transport with lateral and vertical exchange across interfaces. Thus, the river corridor, rather than the wetted river channel itself, is an increasingly common unit of study. Main channel exchange with recirculating marginal waters, hyporheic exchange, bank storage, and overbank flow onto floodplains are all included under a broad continuum of interactions known as “hydrologic exchange flows.” Hydrologists, geomorphologists, geochemists, and aquatic and terrestrial ecologists are cooperating in studies that reveal the dynamic interactions among hydrologic exchange flows and consequences for water quality improvement, modulation of river metabolism, habitat provision for vegetation, fish, and wildlife, and other valued ecosystem services. The need for better integration of science and management is keenly felt, from testing effectiveness of stream restoration and riparian buffers all the way to reevaluating the definition of the waters of the United States to clarify the regulatory authority under the Clean Water Act. A major challenge for scientists is linking the small‐scale physical drivers with their larger‐scale fluvial and geomorphic context and ecological consequences. Although the fine scales of field and laboratory studies are best suited to identifying the fundamental physical and biological processes, that understanding must be successfully linked to cumulative effects at watershed to regional and continental scales.

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“…Most of these change studies [1,30,31] quantify change between two distinct time periods and focus on either a few distinct lakes or the overall regional change. This methodology works reasonably well for mapping forest extent or urban growth that are distinct and comparatively stable, but is less effective with water because water bodies are highly dynamic both inter-annually and seasonally.…”

Section: Introductionmentioning

confidence: 99%

Multi-Decadal Surface Water Dynamics in North American Tundra

Carroll

Loboda

2017

Remote Sensing

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Abstract:Over the last several decades, warming in the Arctic has outpaced the already impressive increases in global mean temperatures. The impact of these increases in temperature has been observed in a multitude of ecological changes in North American tundra including changes in vegetative cover, depth of active layer, and surface water extent. The low topographic relief and continuous permafrost create an ideal environment for the formation of small water bodies-a definitive feature of tundra surface. In this study, water bodies in Nunavut territory in northern Canada were mapped using a long-term record of remotely sensed observations at 30 m spatial resolution from the Landsat suite of instruments. The temporal trajectories of water extent between 1985 and 2015 were assessed. Over 675,000 water bodies have been identified over the 31-year study period with over 168,000 showing a significant (p < 0.05) trend in surface area. Approximately 55% of water bodies with a significant trend were increasing in size while the remaining 45% were decreasing in size. The overall net trend for water bodies with a significant trend is 0.009 ha year −1 per water body.

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New permafrost is forming around shrinking Arctic lakes, but will it last?

Cited by 61 publications

References 32 publications

Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

River corridor science: Hydrologic exchange and ecological consequences from bedforms to basins

Multi-Decadal Surface Water Dynamics in North American Tundra

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