The Impact of the Final Lake Agassiz Flood Recorded in Northeast Newfoundland and Northern Scotian Shelves Based on Century-Scale Palynological Data - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 138

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

Elisabeth Levac

Environmental Studies and Geography, Bishop ' s University, Sherbrooke, Quebec, Canada

C. F. M. Lewis

Geological Survey of Canada-Atlantic, Natural Resources Canada, Dartmouth, Nova Scotia, Canada

A. A. L. Miller

marine g.e.o.s., Wolfville, Nova Scotia, Canada

Two high-resolution century-scale palynological records from the eastern Cana-
dian margin were analyzed to estimate the impact of Lake Agassiz 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, signi

' s

agel-
late 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

cant changes in dino

' s Basin, on the northern Scotian Shelf contains similar

changes in dino agellate 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

owed 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

final drainages of Lake Agassiz

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.

1. INTRODUCTION

rst
detected in the Greenland Ice Sheet oxygen isotope records
[Johnsen et al., 1992; Dansgaard, 1993; Alley et al., 1997]
was imputed to have resulted from a slowing in Atlantic
meridional overturning circulation (AMOC) [Alley et al.,

The abrupt cooling event known as the 8.2 ka event,