The role of permafrost and seasonal frost in the hydrology of northern wetlands in North America

Wetlands are a common landscape feature in the Arctic, Subarctic, and north Temperate zones of North America. In all three-zones, the occurrnce of seasonal frost results in similar surface-water processes in the early spring. For example, surface ice and snow generally melt before the soil frost thaws, causing melt water to flow into depressions, over the land surface and at times, across low topographic divides. However, evapotranspiration and ground-water movement differ among the three climatic zones because they are more affected by permafrost than seasonal frost. The water source for plants in the Arctic is restricted to the small volume of subsurface water lying above the permafrost. Although this is also true in the Subarctic where permafrost exists, where it does not, plants may receive and possibly reflect, more regional ground-water sources. Where permafrost exists, the interaction of wetlands with subsurface water is largely restricted to shallow local flow systems. But where permafrost is absent in parts of the Subarctic and all of the Temperature zone, wetlands may have a complex interaction with ground-water-flow systems of all magnitudes.