Ice wedge degradation and CO2 and CH4 emissions in the Tuktoyaktuk Coastlands, NT

Martin, Abra F.; Lantz, Trevor C.; Humphreys, Elyn

doi:10.1139/as-2016-0011

Cited by 8 publications

(16 citation statements)

References 41 publications

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Section: Introductionmentioning

confidence: 99%

“…This process has significant climate implications because, relative to LCPs or flat terrain, the soil in HCP centers tends to be well drained, driving enhanced seasonal emissions of CO 2 and reduced emissions of CH 4 (Lara et al, 2015;Lipson et al, 2012;Wainwright et al, 2015). Frequently, as HCPs develop, the subsiding troughs become inundated, and the resulting ponds (or thermokarst pools) may also function as sites of enhanced emissions of both CO 2 and CH 4 (Martin et al, 2018) . In the past 30 years, increased air temperatures associated with climate change (Overland et al, 2013;Schuur et al, 2015) have spurred an abrupt acceleration in the onset of ice wedge melting throughout the Arctic (Farquharson et al, 2019;Fraser et al, 2018;Jorgenson et al, 2006Jorgenson et al, , 2015Liljedahl et al, 2016;Raynolds et al, 2014). Once melting initiates, however, the relationship between summer severity and rates of ice wedge degradation is nonlinear, as thermokarst is influenced by an array of competing feedbacks (Jorgenson et al, 2015;Kanevskiy et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Feedbacks Between Surface Deformation and Permafrost Degradation in Ice Wedge Polygons, Arctic Coastal Plain, Alaska

et al. 2020

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In the past three decades, an abrupt, pan‐Arctic acceleration of ice wedge melting has transformed tundra landscapes, spurring the formation of hummock‐like features known as high‐centered polygons (HCPs). This rapid geomorphic transition profoundly alters regional hydrology and influences surface emissions of CO2 and CH4. In Arctic Alaska, most recent instances of ice wedge degradation have arrested within 15–20 years of inception, stabilizing HCP microtopography. However, feedbacks between ground surface deformation and permafrost stability are incompletely understood, limiting our capacity to predict trajectories of landscape evolution in a still warmer future. Here, we use field data from a site near Prudhoe Bay, Alaska, to develop a modeling‐based framework for assessing the strength of positive (i.e., exacerbating) feedbacks on ice wedge degradation, focusing on the importance of heterogeneity in surface drainage and microtopographic conditions. Our simulations suggest that, when troughs are narrow, positive feedbacks on ice wedge melting (associated with thermokarst pool formation) are relatively weak. Positive feedbacks are markedly stronger beneath wide troughs, such as those that form above older, larger ice wedges. Seasonal thaw abruptly accelerates once a talik begins to form beneath wide and deep thermokarst pools. Once a talik initiates, winter severity and snowpack thickness increase in importance as predictors of thaw intensity in summer. Our results indicate that meter‐scale heterogeneity in polygonal microtopography potentially exerts strong, nonlinear controls on thermokarst trajectories. These findings are useful for predicting future thermokarst dynamics and for interpreting the results from coarser‐resolution land surface models operating at greater spatial and temporal scales.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Feedbacks Between Surface Deformation and Permafrost Degradation in Ice Wedge Polygons, Arctic Coastal Plain, Alaska

et al. 2020

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“…Deeper thaw is expected to correlate positively with CO2 emissions since there would be more substrate available for micro-organisms (Zona et al, 2010;Harden et al, 2012;Belshe et al, 2013;Kuhry et al, 2013;Schuur et al, 2015). Soil moisture is found to be an important control on CH4 emissions, with higher emissions at wet or saturated sites such as wet meadow tundra, thaw ponds and polygonal terrain (Fan et al, 1992;Bartlett et al, 1992;Vourlitis et al, 1993;Merbold et al, 2009;Laurion et al, 2010;Martin et al, 2017). In contrast, CO2 emissions were found to be lower at wet or saturated sites compared to drier tundra sites (Fan et al, 1992;Vourlitis and Oechel, 1999;Oberbauer et al, 2007;Merbold et al, 2009).…”

Section: Decomposition Is Reduced When Microbial Activity Is Limited mentioning

confidence: 99%

“…CO2 and CH4 emissions have been found to be highly variable over time and space in the Arctic. For example, measured CH4 fluxes vary from small to large emissions in polygonal terrain (0.155 to > 1397.6 mg CH4 m -2 day -1 ; Martin et al, 2017). Other studies have found lower values across the Arctic with mean values of 29 mg CH4 m -2 day -1 in an Alaskan wet meadow tundra (Fan et al, 1992) and 151.2 mg CH4 m -2 day -1 in a fen located in an Arctic valley in Greenland (Christensen et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…CO2 emissions due to respiration processes are also controlled by hydrological variables, vegetation, and temperature, among other variables (Welker et al, 2000). CO2 emissions are much higher than CH4 emissions ranging between 0.07 and 46.79 g CO2 m -2 day -1 for polygonal terrain in Tuktoyaktuk Coastlands (Martin et al, 2017) or between -0.89 and 5.03 g CO2 m -2 day -1 for thaw ponds located near Bylot Island and Nunavik in the eastern Canadian Arctic and Subarctic (Laurion et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Spatial variability of carbon emissions within a drained lake basin and its surrounding tundra, Illisarvik, Northwest Territories

Laforce¹

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This study investigates the spatial and temporal variations of carbon emissions and their controls at a 38-year-old drained lake basin on Richards Island, NT. Greenhouse gas fluxes were collected from plots with different vegetation throughout the basin and in surrounding tundra during the growing season. Wet Sedge sites were significant sources of methane (7 to 355 nmol m -2 s -1 ) while most other sites were sinks.

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Weak mineralization despite strong processing of dissolved organic matter in Eastern Arctic tundra ponds

Laurion

Massicotte

Mazoyer

et al. 2020

Limnology & Oceanography

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Permafrost thawing mobilizes large quantities of organic carbon that was sequestered in Arctic regions over the last glacial cycle. Processes involved in the oxidation of this carbon need to be further assessed to estimate the fraction to be released into the atmosphere. Shallow tundra ponds are sites of active carbon turnover on the landscape and significant sources of greenhouse gases. Dissolved organic matter (DOM) leached from thawing peat into these ponds is exposed to sunlight, with the potential to accelerate its mineralization directly into CO2 or through the production of more labile molecules. We tested the catalytic effect of sunlight on DOM mineralization in tundra ponds formed on organic‐rich polygonal landscapes originating from syngenetic permafrost, including a pond exposed to active permafrost erosion. Microbial decay rates, measured as the loss of chromophoric DOM, were similar to photodecay rates (1%–3% d−1). Groups of fluorescing molecules were formed through microbial transformation or lost through photolysis at differing rates among studied ponds, with the erosive trough pond presenting a unique response suggesting the involvement of soil microbes. Despite the stimulation of microbial growth under sunlight and the dynamic response of DOM optical properties, the loss of dissolved organic carbon was not significant under any treatment. This suggests that microbial and photochemical mineralization of DOM was slow and potentially substrate‐limited during the dry period when ponds were sampled. The static nature of tundra ponds, with their long water retention time, may thus constrain hot moments when water moves and transports carbon on the landscape.

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Ice wedge degradation and CO2 and CH4 emissions in the Tuktoyaktuk Coastlands, NT

Cited by 8 publications

References 41 publications

Feedbacks Between Surface Deformation and Permafrost Degradation in Ice Wedge Polygons, Arctic Coastal Plain, Alaska

Feedbacks Between Surface Deformation and Permafrost Degradation in Ice Wedge Polygons, Arctic Coastal Plain, Alaska

Spatial variability of carbon emissions within a drained lake basin and its surrounding tundra, Illisarvik, Northwest Territories

Weak mineralization despite strong processing of dissolved organic matter in Eastern Arctic tundra ponds

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