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Over the past 30 years, the Arctic regions have experienced a warming greater than anywhere else on Earth. This warming has led to important consequences such as the beginning of permafrost thaw. Permafrost in the northern circumpolar region holds approximately half of the Earth’s belowground organic carbon pool. This carbon, previously locked in permafrost, now threatens to be released into the atmosphere as Arctic average temperatures continue to rise. Despite the growing attention the northern regions are now receiving, studies spanning multiple decades are practically inexistent and consequence assessments of permafrost thawing over many years remain speculative, based on numerical models or limited to observations of short duration.
The first objective of this project is to revisit a site in the Foucault river valley near Salluit (Nunavik), that was studied extensively in 1990 and to evaluate how it evolved over the past 25 years. Using high-resolution satellite imagery analysis, we plan to measure how climate change affected the landscape and to measure at what rate such changes took place as warming only started around 1993 in this region. This will allow quantifying the eroded volumes of permafrost over the past 25 years. It will also allow elaborating mathematical models based on actual field measurements rather than estimates. We expect significant losses of eroded volumes due to the formation of erosion gullies and landslides.
The second objective is to study the different permafrost carbon release processes that took place in recent decades. We want to identify these processes and quantify the carbon losses that occurred in order to determine the relative importance of each mechanism leading to belowground carbon release. The quantification of these losses is very important because it allows estimating the vulnerability of permafrost and the carbon it contains to climate change. Although carbon release mechanisms are well documented individually for short periods of time, multi-decadal studies investigating simultaneously multiple processes remain fragmented and marginal. We expect to measure a larger amount of carbon available to interact with the environment and carbon depletion in the upper layers of permafrost.
To measure the impact of rising air temperatures on the landscape since 1990, we intend to revisit a dozen sites in the Foucault river valley near Salluit (Nunavik), where we will carry out several surveys and drillings of 2-3 m to compare the current depth of the active layer (the layer that thaws in summer and refreezes in winter) with that measured 25 years ago. We will also measure changes following the melting of the abundant networks of ice wedges mapped in this sector.
Laboratory analyses of the soil cores will provide more information about the content and properties of the carbon stored in the permafrost. By measuring the carbon content at different depths, we will be able to determine whether there was a decrease in belowground carbon in the upper layers, i.e. the areas most vulnerable to surface warming, in recent years. This analysis will allow us to assess how fast soil carbon depletion processes operated and with what magnitude. We will also collect gas samples from soil emissions and analyze the content of the samples to determine the proportion of old carbon emitted.
In short, we plan to conduct a research project that still has no equivalent in the field of climate change impact on permafrost by using a unique source of information and revisiting a research site with state-of-the-art analytical methods.
Gagnon, S., Allard, M., Nicosia, A., 2017. Diurnal and seasonal variations of tundra CO2 emissions in a polygonal peatland near Salluit, Nunavik, Canada. Arctic Science. DOI: https://doi.org/10.1139/as-2016-0045.
Gagnon, S., L’Hérault, E., Lemay, M., Allard, M., 2016. New low-cost automated system of closed chambers to measure greenhouse gas emissions from the tundra. Agricultural and Forest Meteorology, 228: 29-41. DOI: 10.1016/j.agrformet.2016.06.012.