Threshold sensitivity of shallow Arctic lakes and sublake permafrost to changing winter climate

Arp, Christopher D.; Jones, Benjamin M.; Grosse, Guido; Bondurant, Allen C.; Romanovsky, V. E.; Hinkel, Kenneth M.; Parsekian, Andrew D.

doi:10.1002/2016gl068506

Cited by 80 publications

(78 citation statements)

References 35 publications

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“…Most research on taliks has focused on those below aquatic bodies, such as lakes (Arp et al, 2016;Kokelj et al, 2009;You et al, 2017) and wetlands (O'Donnell et al, 2012;Sjöberg et al, 2016). Water flowing through taliks can introduce energy for permafrost thaw and can serve to limit downward progression of the freezing front in the winter.…”

Section: 1002/2017jf004469mentioning

confidence: 99%

The Influence of Shallow Taliks on Permafrost Thaw and Active Layer Dynamics in Subarctic Canada

et al. 2018

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Measurements of active layer thickness (ALT) are typically taken at the end of summer, a time synonymous with maximum thaw depth. By definition, the active layer is the layer above permafrost that freezes and thaws annually. This study, conducted in peatlands of subarctic Canada, in the zone of thawing discontinuous permafrost, demonstrates that the entire thickness of ground atop permafrost does not always refreeze over winter. In these instances, a talik exists between the permafrost and active layer, and ALT must therefore be measured by the depth of refreeze at the end of winter. As talik thickness increases at the expense of the underlying permafrost, ALT is shown to simultaneously decrease. This suggests that the active layer has a maximum thickness that is controlled by the amount of energy lost from the ground to the atmosphere during winter. The taliks documented in this study are relatively thin (<2 m) and exist on forested peat plateaus. The presence of taliks greatly affects the stability of the underlying permafrost. Vertical permafrost thaw was found to be significantly greater in areas with taliks (0.07 m year−1) than without (0.01 m year−1). Furthermore, the spatial distribution of areas with taliks increased between 2011 and 2015 from 20% to 48%, a phenomenon likely caused by an anomalously large ground heat flux input in 2012. Rapid talik development and accelerated permafrost thaw indicates that permafrost loss may exhibit a nonlinear response to warming temperatures. Documentation of refreeze depths and talik development is needed across the circumpolar north.

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Section: 1002/2017jf004469mentioning

confidence: 99%

The Influence of Shallow Taliks on Permafrost Thaw and Active Layer Dynamics in Subarctic Canada

et al. 2018

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“…The uncertainty in overall magnitude of thermokarst GHG fluxes to the atmosphere is the result of a scarcity of observations (Powers & Hampton, 2016), the poorly understood seasonality of thermokarst lakes (Holgerson & Raymond, 2016), and large differences in emission rates observed among the lakes studied to date (Vonk et al, 2015). The majority of thermokarst lakes are located in regions with limited access for ground observations, particularly during the period of winter snow cover (Arp et al, 2016;Jones et al, 2011). As a result, the data on GHG dynamics in thermokarst lakes are mostly limited to the open-water season (Hampton et al, 2017;Wik, Thornton, et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Winter Accumulation of Methane and its Variable Timing of Release from Thermokarst Lakes in Subarctic Peatlands

2019

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Previous studies of thermokarst lakes have drawn attention to the potential for accumulation of CH 4 under the ice and its subsequent release in spring; however, such observations have not been available for thermokarst waters in carbon-rich peatlands. Here we undertook a winter profiling of five black-water lakes located on eroding permafrost peatlands in subarctic Quebec for comparison with summer profiles and used a 2-year data set of automated water temperature, conductivity, and oxygen measurements to evaluate how the annual mixing dynamics may affect the venting of greenhouse gases to the atmosphere. All of the sampled lakes contained large amounts of dissolved CH 4 under their winter ice cover. These sub-ice concentrations were up to 5 orders of magnitude above air equilibrium (i.e., the expected concentration in lake water equilibrated with the atmosphere), resulting in calculated emission rates at ice breakup that would be 1-2 orders of magnitude higher than midsummer averages. The amount of CO 2 dissolved in the water column was reduced in winter, and the estimated ratio of potential diffusive CO 2 to CH 4 emission in spring was half the measured summer ratio, suggesting a seasonal shift in methanogenesis and bacterial activity. All surface lake ice contained bubbles of CH 4 and CO 2 , but this amounted to <5% of the total amount of the dissolved CH 4 and CO 2 in the corresponding lake water column. The continuous logging records suggested that lake morphometry may play a role in controlling the timing and extent of CH 4 and CO 2 release from the water column to the atmosphere.Plain Language Summary Waterbodies that are formed by the thawing and collapse of ice-rich permafrost ("thermokarst lakes") are known to be major sources of greenhouse emissions in northern landscapes, but the seasonal variation in these emissions is not well understood. In this study, we measured the concentrations of methane and carbon dioxide beneath the ice of five thermokarst lakes in late winter and compared these with summer concentrations and profiles. These "black-water lakes" are located in subarctic peatlands and are darkly colored because of their high concentrations of permafrost-derived, colored organic carbon. The results showed a winter accumulation of gases beneath the ice that would result in 10 to 100 times greater emissions from the surface waters at spring ice breakup than during summer open water conditions. However, continuous in situ measurements of water temperature and oxygen showed that lakes with smaller area to depth ratios may partially retain greenhouse gases that accumulated in their bottom waters throughout winter, thereby limiting the loss of methane in spring that would otherwise occur. More complete mixing occurred during fall cooling and circulation, and release of gases accumulated in the bottom waters during winter and summer may occur at that time. The exact volume of lake water that is mixed during the spring and fall periods is likely related to the wind fetch and depth of the basin. These...

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“…Past broad-scale research has predominantly focused on thermal responses of lakes to climate warming (O'Reilly et al 2015, Arp et al 2016, Woolway et al 2017. Relatively few broad-scale studies have examined lake ecosystem responses to both temperature and precipitation and have often used just one response variable, a relatively homogenous study area, long-term climate averages, or a low number of years.…”

Section: Introductionmentioning

confidence: 99%

Geographic Patterns of the Climate Sensitivity of Lakes

McCullough¹,

Cheruvelil²,

Collins³

et al. 2019

Bulletin Ecologic Soc America

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Threshold sensitivity of shallow Arctic lakes and sublake permafrost to changing winter climate

Cited by 80 publications

References 35 publications

The Influence of Shallow Taliks on Permafrost Thaw and Active Layer Dynamics in Subarctic Canada

The Influence of Shallow Taliks on Permafrost Thaw and Active Layer Dynamics in Subarctic Canada

Winter Accumulation of Methane and its Variable Timing of Release from Thermokarst Lakes in Subarctic Peatlands

Geographic Patterns of the Climate Sensitivity of Lakes

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