Impacts of Hudson Bay on the Terrestrial Climate of the Hudson Bay Lowlands^*

* A version of this paper was presented at the Circumpolar Ecosystems in Winter Symposium, 16-21 February 1990, Churchill, Manitoba, Canada.

Abstract

Hudson Bay remains frozen or is dominated by ice over the summer solstice and throughout much of the high-sun season. This contributes directly to the winterization of summer. The juxtaposition of the mean summer position of the Arctic front and of treeline to the west of Hudson Bay has been clearly documented, and the coincidence of treeline and the southern boundary of continuous permafrost is well known. The strong southward thrust of the Arctic front in summer is, in major degree, a response to cold air masses spawned over Hudson Bay.

On a mesoscale, Hudson Bay generates onshore winds across a strong temperature and pressure gradient. This mesoscale regime dominates the temperature and surface energy balance for a large distance inland across the Hudson Bay Lowlands. Superimposed on the mesoscale wind field is a land-sea breeze, which is sometimes well developed in coastal areas and which can be traced up to 65 km inland. It is, however, of low frequency occurrence and is usually overridden by the regional wind.

Progressing inland from the coast, in the central Hudson Bay Lowlands, the landscape becomes dominated by deep peat soils and a surface vegetation which is resistant to evapotranspiration. As a result, it is much drier than the wetlands near the coast and evapotranspiration is reduced.

The large-scale cold air masses originating over Hudson Bay and the cold mesoscale winds combine to impose cold air temperatures on the adjacent terrestrial environment. Even with abundant solar radiation and saturated surfaces, evaporation is vigorously suppressed by these cold temperatures. Any warming or cooling during climate change will have a double impact on the terrestrial environment through the strong linkages with Hudson Bay.