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Mesoscale wind and temperature changes over peatlands of the Hudson Bay Lowlands

Mesoscale wind and temperature changes over peatlands of the Hudson Bay Lowlands

Olalekan Balogun

Olalekan Balogun is a recent PhD graduate in Physical Geography from the Faculty of Environmental and Urban Change, York University. With a specialization in Climatology, his doctoral research focused on the climatic changes in the mesoscale wind and temperatures over the peatlands of the Hudson Bay Lowlands and their impacts on the surface energy balance and net ecosystem carbon exchange. Olalekan’s research was supervised by Professors Richard Bello, Kaz Higuchi and Kathy Young.

Peatlands in the Arctic and Subarctic regions account for about one-third of the global soil organic carbon (C) pool. Over the past 12,000 years, these northern peatlands have accumulated large amounts of organic C as a result of the imbalance between plant productivity and microbial decomposition. Recent global warming, Arctic amplification, and land-use changes threaten the ability of northern peatlands to continue to act as a net carbon sink. The overall stability of the peatland C reservoir will depend on the combined response of ecosystem respiration and gross primary production to temperature and moisture changes.

On research fieldwork in Churchill, Manitoba (Northern Hudson Bay Lowlands).

Canadian peatlands cover about 12% of the total land area and account for about one-quarter of the world’s peatlands. The largest peat-accumulating complex in Canada (and the second largest in the world) is found in the Hudson Bay Lowlands (HBL) region, which covers an area of approximately 250,000 km2. The HBL is mainly located in Ontario and extends northwest to Manitoba and east to Quebec. The climate and ecosystem of the HBL are strongly influenced by the adjacent Hudson Bay––a large, relatively shallow, inland subarctic sea, which at its core is 6 °C colder than the average for its latitude. The persistence of sea ice in the Hudson Bay until late July contributes to the occurrence of permafrost along the western coast of the HBL. In recent decades, climate warming has resulted in significant trends toward a longer ice-free season over the Hudson Bay, with earlier sea ice breakup in the summer and later freeze-up in autumn.

Difference between offshore and onshore wind frequency over the Hudson Bay Lowlands.

Prior to Olalekan’s research study, we had a very limited understanding of the long-term changes in the surface energy and carbon balance of the HBL in response to climatic trends over the Bay. Previous studies were constrained by short-term, single-site field measurements, which were very useful but insufficient to provide a comprehensive and accurate picture of the state of environmental changes in the HBL. To overcome these challenges, Olalekan used a combined model and assimilated climate dataset (North American Regional Reanalysis, NARR) to examine the mesoscale wind and temperature changes in the entire HBL and their impacts on the surface energy balance over the past 40 years (1979–2018). Also, he employed a satellite data-driven light-use efficiency model (Vegetation Photosynthesis and Respiration Model, VPRM) to investigate the response of gross primary production, ecosystem respiration and net ecosystem exchange to climatic changes from 2000 to 2019.

Average offshore ground heat flux (QG) anomalies over the HBL (1979–2018). Left: Theil-Sen slope (TSA) for all grid locations. Right: Top 25% of the grid locations with the highest TSA.

Olalekan’s ground-breaking doctoral research will help improve our understanding of the long-term warming-induced changes in the advective influence of the Hudson Bay and its linkage to the changes in the surface energy and carbon balance over peatlands of the HBL. His research findings reveal that, under present and projected climate warming in the HBL, the changes in the mesoscale wind regimes and temperatures and their associated impacts on the surface energy and carbon balance are markedly different than was previously thought. Spatial analyses of the climatic trends show several prominent hotspots found mostly along the coast and at the mouths of rivers such as Churchill, Severn and Winisk, as well as in an extensive narrow belt along the Ekwan and Attawapiskat Rivers in southern HBL. The results of the study are important for policy decisions, suggesting that management strategies may take on an increased sense of urgency in particular areas of the HBL. Moreover, the multidisciplinary implications of the spatial variability in air temperature and ground warming across the region imply that other field scientists researching belugas, polar bears, birds, or permafrost will be able to put their research into context.