A team of researchers, including Queen’s University’s Scott Lamoureux and Melissa Lafrenière, Professors in the Department of Geography and Planning, have published a study in Nature Communications that examines the importance of summer rainfall in High Arctic settings. The study, "Emerging Dominance of Summer Rainfall Driving High Arctic Terrestrial-Aquatic Connectivity," presents a new analysis of a long-term hydrological, meteorological, and water quality data set from the Queen’s-led Cape Bounty Arctic Watershed Observatory in Nunavut.
The work documents a shift in the importance of summer rainfall in this High Arctic setting, and how the resulting shift in the timing of river flow, along with the erosive power of rainfall runoff vs snowmelt runoff drive important changes in the amounts of carbon and mineral loads carried by Arctic rivers.
“Our long term research in the High Arctic shows how changing climate and permafrost will alter river flow and water quality,” said Dr. Scott Lamoureaux, Professor and Robert Gilbert Chair, Associate Head, Undergraduate Department of Geography and Planning. “Our work emphasizes the emerging importance of summer rainfall in the High Arctic. Spring snowmelt is no longer always the main source of water, and this changes the way the rivers flow and water quality changes.”
One of the key findings the study identifies is that there is a threshold of stream power (or energy) necessary to move carbon and sediment in the rivers is more important than landscape changes. These changes are due to permafrost disturbances, warming soils, increased plant growth, organic matter production, and mineral weathering to the aquatic environments. The researchers found that the increase in the power of rivers due to summer rainfall is an important control on the amount of carbon coming from these watersheds - and this energy threshold may explain the role that inland waters (lakes, ponds, rivers) play in redistributing carbon in a changing climate.
Another important result is that the increased magnitude and frequency of rainfalls has a greater control on the release of carbon from the watersheds than permafrost disturbances, but that even small permafrost disturbances are important, because they effectively prime the landscape for accelerated changes when future rainfall levels and stream runoff are higher.
Although “permafrost disturbance can have a huge local impact where it occurs," Lamoureaux stated, "the rivers need to have sufficient flow energy to deliver this impact downstream to rivers and lakes.”
This research is extremely novel, as there is no other data set like it in the Arctic that combines river and comprehensive water quality measurements. The research by the Queen’s team and collaborators spans 10+ years and involved sampling by over 100 students and researchers for months at a time. This effort has allowed the research team to document the impact of the warmest years on record, and includes episodes of substantial disturbance to the permafrost and landscape.
“These findings are only possible due to a sustained 10+ year effort by our team at Queen’s and our collaborators, and highlights that it is critital to invest in long-term research sites in order to gain an accurate understanding of the response of permafrost watersheds to climate change,” said Dr. Melissa Lafrenière, Professor, Department of Geography and Planning
These types of long term studies are exceptionally rare in the Arctic, but provide critical understanding about how these fragile environments will respond to climate change. This knowledge is of particular importance for Arctic communities as they manage and adapt to rapid climate change effects to the land and water. Researchers believe it is also very important to understanding how the changes in the Arctic might feedback on climate.
“The team continues this research, working with experts in contaminants and aquatic ecosystems to better understand the implications of the observed changes on human and ecosystem health.” Scott Lamoureaux,
The study was published in Nature Communications.