Elisabeth Levac

Decadal-scale sea ice changes in the Canadian Arctic and their impacts on humans during the past 4,000 years

Abstract Climate warming of >1.5°C over three decades has diminished Arctic sea ice and forced drastic changes on Inuit people of the Canadian Arctic. Discontinuities in archaeological records also suggest that climatic changes may have caused site abandonment and life style shifts in Paleo- and Neo-eskimo societies. We therefore examine the decadal-scale palaeoclimatic changes recorded by quantitative palynological data in marine records from Coburg Polynya, near Palaeo- and Neo-eskimo settlements on the North Devon Lowlands, and from the North Water Polynya between Canada and Northwest Greenland. Palaeotransfer functions from dinoflagellate cyst assemblages provide quantitative estimates of changes in sea surface temperature (SST) and sea ice cover (SIC) with the accuracy of historical measurements. Both sites record temperature variations of 2–4°C corresponding to changes in hunting modes and occupation-abandonment cycles on Devon and Ellesmere Islands. Our data show that from ∼6500 to 2600 BP, there were large oscillations in summer SST from 2–4°C cooler than present to 6°C warmer and SIC ranged from 2 months more sea ice to 4 months more open water. The warmer interval corresponds to the period of pre-Dorset cultures that hunted muskox and caribou. Subsequent marine-based Dorset and Neo-eskimo cultures correspond to progressively cooler intervals with expanded sea ice cover. The warming took ∼50–100 years and lasted ∼300 years before replacement by colder intervals lasting ∼200–500 years. These climate oscillations are more rapid than the archaeological cultural changes, but are of similar length to successive Palaeoeskimo occupations in the Nares Strait region.

Palynological records from bay of islands, Newfoundland: Direct correlation of Holocene paleoceanographic and climatic changes

Abstract A palynological record from Bay of Islands (western Newfoundland) was used to investigate differences in timing between paleoceanographic and paleoclimatic events, and episodic cold sea surface temperature (SST) intervals. Sea surface conditions were reconstructed from dinocyst proxy‐data and paleobioclimatic transfer functions. Correlation of onshore‐offshore pollen records was used to determine ocean‐atmosphere interactions. Between 9.5 and 8.6 ka, cold and lower salinity sea surface conditions and a cold climate may be the result of a large influx of glacial meltwater through the Gulf of St. Lawrence. The marine optimum followed with SST up to 5°C warmer than today until 6.8 ka and coincides with an expansion of boreal forest trees, probably resulting from a climatic amelioration .The terrestrial hypsithermal started only around 6 ka, however, possibly due to the lingering effect of the remaining ice sheet on the regional climate. It coincides with lower summer SST than today. Increased propor...

The Impact of the Final Lake Agassiz Flood Recorded in Northeast Newfoundland and Northern Scotian Shelves Based on Century-Scale Palynological Data

Abrupt Climate C Geophysical Mon Copyright 2011 b 10.1029/2010GM Two high-resolution century-scale palynological records from the eastern Canadian margin were analyzed to estimate the impact of Lake Agassiz’s final drainage at circa 8.3 ka on sea surface conditions and to track the path of the meltwater plume. Core HU87033-19 from Notre Dame Channel on Northeast Newfoundland Shelf contains four distinct detrital carbonate (DC) beds, known to be sediment transported from Hudson Strait and Hudson Bay, and one layer is coeval with the drainage of Lake Agassiz. Within that DC layer, significant changes in dinoflagellate cyst assemblages indicate lower sea surface temperatures and salinity. The drop in salinity is a doublet, suggesting two episodes of meltwater drainage. Core HU84011-12, from St. Anne’s Basin, on the northern Scotian Shelf contains similar changes in dinoflagellate cyst assemblages at the time of the drainage, indicating sea surface cooling accompanied by a slight decrease in salinity. The impact of the meltwater was greater in the Notre Dame Channel. This suggests that most of the meltwater from the final drainages of Lake Agassiz flowed south over the Labrador and Northeast Newfoundland shelves and was not dispersed directly into the Labrador Sea. Instead, it was possibly dispersed into the slope water system and subsequently into the North Atlantic after flowing initially over the continental shelf. This is the first paper describing paleoecological data indicating the presence of the Agassiz meltwater along the eastern Canadian margin.