Emergence of New Arctic Peatlands: The Case of Cambridge Bay, Nunavut, Canada

The Arctic is seeing extensive permafrost thaw as a result of ongoing climate warming. While local flooding is often observed due to ground subsidence and water excess, other areas are getting drier because of water flowing across landscapes that have become more hydrologically connected. With these hydrological changes come the potential for new wetland expansion and soil-carbon accumulation in the form of peat, which could potentially increase the carbon sequestration aptitude of high-latitude landmass. However, the dynamics that fuel peatland development in these regions are quite complex and multivariate. For instance, there have been recent observations of Sphagnum peat moss patches "invading" tundra sites on the North Slope of Alaska and quickly building hummocks. Those small landforms could be seen as proto-peatlands; with time, they may grow in size and function like peatlands. But in many other parts of the Arctic that currently do not support Sphagnum, the more classic hydroseral succession, from a shallow wetland to a thicker peat-accumulating fen system, may be a more prevalent soil-carbon sequestration mechanism, as observed at a few sites across the circum-Arctic. With that said, it remains highly uncertain whether the warming Arctic will evolve into a peatland-rich landscape, as the boreal zone is now, or if there are some essential conditions missing and that will prevent this peaty future.

Here we present preliminary results from four high-latitude wetland sites located in the vicinity of Cambridge Bay, Nunavut, Canada. All sites are categorized as "wet sedge fens" and their vegetation is dominated by Carex aquatilis and a few brown moss species. The water table is shallow and those systems are primarily fed by spring/summer snowmelt. Thus far, organic matter content and plant macrofossil analyses have been performed. The organic soil profiles range between 14 and 38 cm in depth. On the basis of the Canadian peatland definition, none of these sites are technically peatlands, as they do not possess 40+ cm of accumulated peat. As for their geochemical composition, it confirms that those soils are highly organic (at least 80% organic matter). The peaty soil matrix is highly decomposed, with the exception of surface samples. Peat basal ages suggest that these wetlands initiated around 1200 cal. yr BP (range: 1100-1300 cal. yr BP), regardless of their thickness. Additional chronological constraints are needed to determine the rate of peat accumulation, for example to see whether there are peat growth hiatuses along those records and/or to determine whether these ecosystems record a recent increase in peat accumulation.

In August 2022, our team will be revisiting one of the sites described above to perform a detailed hydrogeomorphological analysis. A model of the surface hydrology was created in a geographic information system using data from a digital elevation model to represent water flow and look for empirical relationships between hydrology, wetland presence, and peat thickness. Ground-penetrating radar will be used to survey the wetland complex to better understand peat distribution in the basin. Additional cores will be collected, analyzed, and dated to reconstruct the development of the wetland, including its carbon accumulation history.