Peatlands are globally important wetlands that, despite their small global area, store approximately one third of total global soil carbon. Over hundreds to thousands of years, soil carbon accumulates as peat (partially decomposed organic matter), due mainly to slow decomposition of plant litter in waterlogged and anoxic conditions. In the Arctic, peat-forming ecosystems are "hotspots" of long-term carbon sequestration and are an important component of the overall carbon budget. Shallow “peat patches” typically dominated by peat moss (Sphagnum) and cotton grass (Eriophorum) are distributed across tundra landscapes. These patches, with a surface organic layer generally too thin (< 30 cm) to be classified as peatlands, may represent the initial stage of peatland formation in the Arctic region in a warming climate.

In this project we examined the history of peat accumulation and Sphagnum establishment at three sites in the North American Arctic: Alaska’s North Slope, Cambridge Bay on Victoria Island, Nunavut, and on southern Baffin Island.  Field visits were constrained by Covid-19 pandemic restrictions in several summers, but the North Slope was visited in 2019, Cambridge Bay in 2019 and 2022, and Baffin Island in 2022.  Landscape vegetation and soil surveys were completed, with samples collected and returned to Lehigh, Bowdoin, and Texas A&M labs for analyses. These field investigations were coupled with experiments and modeling to examine the processes controlling peatland carbon storage and accumulation broadly in the Arctic.

In the lab, soil carbon content, carbon accumulation rate, chronology, and paleoecological analysis were performed on short ‘peat’ cores to assess the dynamics and history of the soils across the 3 study areas. Our results revealed that Sphagnum moss rapidly expanded during the past few decades on the North Slope and on southern Baffin Island. Additional analyses revealed this Sphagnum expansion was linked to rising temperatures and a lengthening of the snow-free season. Lab experiments revealed that soil characteristics (peat vs. non-peat) were better at explaining differences in CO₂ production than temperature. A data synthesis that consisted of amassing and synthesizing all existing data on decadal- to centennial-scale peat carbon dynamics was conducted.

The project also included simulations with two peatland models. Using a site-level model we assessed peat carbon vulnerability to 21^st Century warming along a transect of sites in central Canada, from a permafrost-free site at the southern permafrost boundary in Ontario to continuous permafrost near the Arctic Ocean in Nunavut. Simulations indicated that while these peatlands continue to accumulate carbon in their surface soil layers through enhanced vegetation growth, more carbon is lost from slightly deeper in the soil profile. As a result, most sites were projected to lose relatively small amounts of carbon compared to how much they contain (<5%). A regional-scale model was used to simulate the accumulation of about 400 billion tonnes of peat carbon across ~3 million square kilometers of northern peatlands over the past 15,000 years. Under recent warming, simulated peat carbon accumulation rates increased in the colder permafrost regions, while in the warmer discontinuous permafrost and permafrost-free regions peat C accumulation rates decreased. This result suggests that if permafrost regions switch to permafrost-free conditions, the peat C accumulation rate of the entire pan-Arctic region will decrease with higher temperatures. With that said, upon refinement of the nitrogen cycle module within the model, higher CO₂-C sink capacity in northern peatlands was found under warming conditions, with the side effect of increasing CH₄ emissions, weakening the net cooling effect of northern peatlands under future climate scenarios.

Undergraduate and graduate students, as well as early-career researchers, were trained in this project, and the project enhanced opportunities for women in biogeochemistry research. These researchers have had the opportunity to learn state-of-the art field and laboratory measurement and simulation modeling techniques, and to develop their own scientific studies within the context of the larger project. All wrote and presented their research in theses, national and international conferences, as well as peer-reviewed scientific publications. We have disseminated the results of the research at conferences in North America and Europe, collaborated with other teams of scientists, and presented our findings in the peer-reviewed scientific literature. We have organized town halls and workshops to further engage and discuss our findings with peers. We have developed outreach materials that took the form of class activities, outreach blogs, and public lectures.  As a culminating, public-facing event, Bowdoin college hosted a public lecture on arctic greening that was co-sponsored by the Peary-MacMillan Arctic Museum, Earth and Oceanographic Science Department, and Environmental Studies Program.

Last Modified: 11/13/2024
Modified by: Robert K Booth