Lake Winnipeg coastal submergence over the last three centuries

Radiocarbon dating of marsh facies peat and drowned trees along the barrier beaches at the south end of Lake Winnipeg, indicates water levels are presently rising. Lagoonal sediment and associated trees are being buried as the barrier islands move landward in response to rising water levels. Estimates based on radiocarbon dating suggest the water level has been rising 20 cm/century over the last three hundred years. This estimate is consistent with lake level records and models of isostatic uplift which suggest the level of the lake should be rising between 6.7 and 12 cm/century along the south shore. However, additional radiocarbon dates on submerged trees from Observation Point, at the north end of South Basin, and the Spider Islands, near the northern outlet, indicate that at least part of the water-level rise is basin wide. Southward transgression of Lake Winnipeg, throughout the Holocene, is believed to be the result of isostatic tilting of the basin, whereas the recent basin-wide water-level rise is more likely the result of a combination of isostatic tilting and increased precipitation associated with climate change.[PUBLICATION ABSTRACT]