A team of Canadian researchers has uncovered a surprising seasonal rhythm beneath the icy waters of the sub-Arctic, revealing that the seafloor may not be as static as we think.
In a recently published paper, researchers from Natural Resources Canada, the University of New Brunswick, Dalhousie University, Queen's University, Memorial University and the Nunatsiavut Government found that the seafloor subtly moves up and down with the seasons.
During the colder months when the bottom seawaters cool below freshwater freezing temperature, ice forms in the sediment, causing the seabed to swell and rise. This process creates frost blisters as wide as a car and a foot tall. When the warm waters return, ice thaws and the seabed relaxes back down.
Using high-resolution seafloor mapping from 2021 to 2024 in Webb's Bay, Nunatsiavut, along with temperature sensors on the seabed, the research team led by Dr. Alexandre Normandeau, a research scientist at Natural Resources Canada and an adjunct professor in UNB's and Dalhousie's departments of earth sciences, watched as the frost blisters disappeared by late summer or fall, and returned the following winter revealing a consistent seasonal pattern.
"It's a bit like the way seasonal freeze and thaw cycles on land cause the ground to heave and potholes to form in roads, except here the thawing happens in the autumn when warmer waters mix down to the seafloor," said Dr. Normandeau.
Seafloor mapping in polar regions, an area in which UNB's Ocean Mapping Group has long been a global leader, has revealed features linked to underwater permafrost, such as pingos and the frost blisters.
Permafrost is a key part of the Arctic's frozen environment, known as the cryosphere. It stores vast amounts of carbon, making it essential to the Earth's carbon cycle. While recent studies show subsea permafrost is degrading rapidly, little has been known about how the seafloor changes with the seasons until now.
"This research not only deepens our understanding of seafloor dynamics but also highlights the importance of monitoring these changes for the protection of critical offshore infrastructure," added Dr. Normandeau.
Dr. Audrey Limoges, an associate professor of earth sciences at UNB and researcher on the project, played an important role in co-developing the program.
"This project illustrates the power of multidisciplinary collaboration, especially through our partnership with the Nunatsiavut Government and the community of Nain, who were involved from the very first conversations about what the bathymetric features might represent to collecting data in the field," said Dr. Limoges.
"These project findings are not just fascinating and important for the scientific community but provide crucial knowledge and data for advancing the development and implementation of the Imappivut Marine Plan," said Michelle Saunders, research manager at the Nunatsiavut Government and coauthor of the study.
Much is still unknown about frost blisters and their effects. These seasonal changes may be occurring in many places without detection, which makes them an important consideration when planning offshore infrastructure, such as subsea telecommunication cables, pipelines and offshore renewable energy projects.
"The ground under the ocean is still largely unexplored in comparison to related studies on land," said project team member Dr. Barret Kurylyk, an associate professor in Dalhousie's department of civil and resource engineering and Canada Research Chair in Coastal Water Resources. "Results from these recent ocean expeditions highlight that seasonal freezing and thawing is important on the seafloor and likely impacts ground stability and marine infrastructure.
This project was funded by the Marine Geoscience for Marine Spatial Planning program of Natural Resources Canada, and a Natural Science and Engineering Research Council of Canada Ship-time allocation grant to UNB, with support from the Nunatsiavut government.
