HOLOCENE GLACIATION AND CLIMATE HISTORY OF BAFFIN ISLAND, ARCTIC CANADA

The Holocene evolution of climate and glaciation has been reconstructed from a variety of proxies preserved in lake and raised-marine sedimentary archives, and from dated moraines and related ice-recessional features. Cosmogenic exposure dating of glaciated surfaces and erratic blocks, coupled with diagnostic changes in the physical and magnetic properties of sediment in glacier-dominated lacustrine systems, document Laurentide Ice Sheet (LIS) recession of ice from the glacial maximum beginning ~13 ka, with rapid ice retreat until ~10 ka (some outlet glaciers retreated as much as 1000 km in 500 yr). A major readvance of the LIS and mountain glaciers occurred ~9.6 ka (Cockburn Substage). At least one minor but widespread readvance occurred just before 8.0 ka, possibly related to the 8.2 ka event. Local glaciers were behind their present margin before 7 ka, and in some instances much earlier, although the retreating LIS continued to slowly retract to the present day Barnes Ice Cap through the Holocene; Pleistocene ice in the lower levels demonstrates the LIS has yet to completely disappear. The onset of Neoglaciation is well dated to 5.5 ka, with intensification after 2.5 ka. The expansion of local glaciers during the Little Ice Age represents the most extensive advance since 7 ka. Local hilltop ice caps on the plateau of north-central Baffin Island began their most recent expansion 500 years ago. Over the past century melting has reduced their coverage to <5% of their former area. Lakes not covered by the LIS at the LGM remained frozen throughout the year. By 14 ka increasing summer warmth produced moats around some southern lakes, aquatic moss were established, but pollen is exclusively from south of the LIS. By about 12 ka most lakes outside the ice margins thawed. Pollen at this time was dominated by grass, indicating relatively dry, cold summers. Terrestrial and marine conditions as least as warm as present were established by 9 ka. Organic matter accumulation in lake sediment peaked earlier in the south (11 to 9 ka) than in the north (9.5 to 6 ka). Most lakes exhibit a strong increase in minerogenic sediment in the late Holocene, suggesting cooler summers and disruption of vegetation in their catchments. Stronger-than-present penetration of Atlantic water along the east coast of Baffin Island began ~9.5 ka and persisted until ~4 ka.