Distribution and growth of thaw slumps in the Richardson Mountains–Peel Plateau region, northwestern Canada

Lacelle, Denis; Brooker, Alex; Fraser, Robert; Kokelj, S. V.

doi:10.1016/j.geomorph.2015.01.024

Cited by 122 publications

(165 citation statements)

References 38 publications

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“…For example, TEFs (thermo-erosional features) are discretely distributed across the landscape, following variations in topography (affecting, for example, snow cover; Godin et al, 2015) and ground ice content. While these features can be numerous in impacted areas (Lacelle et al, 2015) they take up a relatively small percentage of the total landscape area (1.5 % in Alaska; Krieger, 2012). Individual TEFs have lifecycles on the order of decades Pearce et al, 2014), and -while they are active -may have intense local impacts on sediment and ionic fluxes to freshwater systems (see below).…”

Section: Press Vs Pulse Disturbancesmentioning

confidence: 99%

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

et al. 2015

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Abstract. The Arctic is a water-rich region, with freshwater systems covering about 16 % of the northern permafrost landscape. Permafrost thaw creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic (still) and lotic (moving) systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying factors determine (i) the degree to which permafrost thaw manifests as thermokarst, (ii) whether thermokarst leads to slumping or the formation of thermokarst lakes, and (iii) the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can Published by Copernicus Publications on behalf of the European Geosciences Union. J. E. Vonk et al.: Effects of permafrost thaw on Arctic aquatic ecosystemsbe considerable, with these modifying factors determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted lakes and streams is also likely to change; these systems have unique microbiological communities, and show differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter, and nutrient delivery. The degree to which thaw enables the delivery of dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO 2 and CH 4 ), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to quantify how permafrost thaw is affecting aquatic ecosystems across diverse Arctic landscapes, and the implications of this change for further climate warming.

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Section: Press Vs Pulse Disturbancesmentioning

confidence: 99%

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

et al. 2015

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“…One such exception occurs when an insulating veneer protects the ground ice, thus slowing down volume losses . Such an insulating cover, principally derived from the thawing sediments themselves, as well as from late-lying snow, commonly persists in early summer Lacelle et al, 2015). Early summer mass wasting may also be subdued because the incoming energy is used to warm the cold permafrost to the melting point before ablation can set in.…”

Section: S Zwieback Et Al: Thaw Slump Mass Wasting Not Energy Limitedmentioning

confidence: 99%

“…Lewkowicz (1987) and Lacelle et al (2015) observed that early season mass wasting can veneer late lying snowdrifts, protecting ice-rich permafrost from early season thawing. Snow cover was still widespread in thaw slumps at the time of the first radar acquisition in early June (Tuktoyaktuk coastlands), but likely limited in depth due to the preceding weeks of above-zero temperatures.…”

Section: Sub-seasonal Mass Wastingmentioning

confidence: 99%

Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale

et al. 2018

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Abstract. Predicting future thaw slump activity requires a sound understanding of the atmospheric drivers and geomorphic controls on mass wasting across a range of timescales. On sub-seasonal timescales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other factors such as rainfall or the formation of an insulating veneer may also be relevant. To study the sub-seasonal drivers, we derive topographic changes from single-pass radar interferometric data acquired by the TanDEM-X satellites. The estimated elevation changes at 12 m resolution complement the commonly observed planimetric retreat rates by providing information on volume losses. Their high vertical precision (around 30 cm), frequent observations (11 days) and large coverage (5000 km 2 ) allow us to track mass wasting as drivers such as the available energy change during the summer of 2015 in two study regions. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm day −1 ) despite the ample available energy, suggesting the widespread presence of early season insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm day −1 ), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August respectively. The observed temporal patterns are poorly related to slump characteristics like the headwall height. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting.

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“…On the Peel Plateau, slumping is largely constrained by the maximum extent of the LIS because the thick layers of ice-rich permafrost necessary for RTS activity are typically not present beyond the glacial limits . Fluvial incision provides the topographic gradient necessary for thaw slump development and RTS features are common; ranging in size from numerous small features to those greater than 20 ha, which are rare (< 5 % prevalence; Lacelle et al, 2015). The recent intensification of slumping on the Peel Plateau is driven in part by increasing air temperatures and summer rainfall .…”

Section: Introductionmentioning

confidence: 99%

Retrogressive thaw slumps temper dissolved organic carbon delivery to streams of the Peel Plateau, NWT, Canada

2017

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Abstract. In Siberia and Alaska, permafrost thaw has been associated with significant increases in the delivery of dissolved organic carbon (DOC) to recipient stream ecosystems. Here, we examine the effect of retrogressive thaw slumps (RTSs) on DOC concentration and transport, using data from eight RTS features on the Peel Plateau, NWT, Canada. Like extensive regions of northwestern Canada, the Peel Plateau is comprised of thick, ice-rich tills that were deposited at the margins of the Laurentide Ice Sheet. RTS features are now widespread in this region, with headwall exposures up to 30 m high and total disturbed areas often exceeding 20 ha. We find that intensive slumping on the Peel Plateau is universally associated with decreasing DOC concentrations downstream of slumps, even though the composition of slump-derived dissolved organic matter (DOM; assessed using specific UV absorbance and slope ratios) is similar to permafrost-derived DOM from other regions. Comparisons of upstream and downstream DOC flux relative to fluxes of total suspended solids suggest that the substantial fine-grained sediments released by RTS features may sequester DOC. Runoff obtained directly from slump rill water, above entry into recipient streams, indicates that the deepest RTS features, which thaw the greatest extent of buried, Pleistocene-aged glacial tills, release low-concentration DOC when compared to paired upstream, undisturbed locations, while shallower features, with exposures that are more limited to a relict Holocene active layer, have within-slump DOC concentrations more similar to upstream sites. Finally, fine-scale work at a single RTS site indicates that temperature and precipitation serve as primary environmental controls on above-slump and below-slump DOC flux, but it also shows that the relationship between climatic parameters and DOC flux is complex for these dynamic thermokarst features. These results demonstrate that we should expect clear variation in thermokarst-associated DOC mobilization across Arctic regions. However, they also show that within-region variation in thermokarst intensity and landscape composition is critical for determining the biogeochemical response. Geological and climate legacy shape the physical and chemical composition of permafrost and thermokarst potential. As such, these factors must be considered in predictions of land-to-water carbon mobilization in a warming Arctic.

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Distribution and growth of thaw slumps in the Richardson Mountains–Peel Plateau region, northwestern Canada

Cited by 122 publications

References 38 publications

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale

Retrogressive thaw slumps temper dissolved organic carbon delivery to streams of the Peel Plateau, NWT, Canada

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