Energy balance measurements were made simultaneously at a terrestrial site in southern James Bay (SJB) and one in central Hudson Bay (CHB) during the growing season of 1985. Both sites were located 1 km inland from east‐west trending coastlines and both were fully vegetated with sedge grasses growing in standing water. The SJB site is in a non‐permafrost environment, whereas the CHB site is underlain by continuous permafrost.
The measurements indicate that the magnitudes of all components of the energy balance, except net radiation, are strongly dependent on wind direction. Onshore winds are dominant. With onshore winds, the ground heat flux, evaporative heat flux and air temperature are smaller than for offshore winds and the sensible heat flux is larger. These relationships are apparent when the wind is directionally persistent for a full day and when there is a major wind shift between onshore and offshore during the day.
With colder air temperatures the Bowen ratio becomes much larger than would be expected under conditions of potential evapotranspiration. This appears to be caused by a rapid increase in the canopy resistance of sedge grasses which occurs when air temperatures drop below 16°C.
Components of the energy balance are linearly correlated with air temperature. This could be useful in predicting the impact of human activities which result in long term temperature change in the Hudson Bay lowlands, which is a large area with a very sparse climate database.