24 mars : séminaire de David Mosher

NAMOC:
the Northwest Atlantic Mid-Ocean Channel

 

David Mosher, Center for Coastal and Ocean Mapping / Joint Hydrographic Center, University of New Hampshire

lundi 24 mars, 14h30, amphi D, IUEM

The Northwest Atlantic Mid-Ocean Channel (NAMOC), at 3800 km,  is the longest deep sea channel in the World.  It wends its way from seaward of Hudson Strait, through the Labrador Sea, around the Grand Banks of Newfoundland and into the Sohm Abyssal Plain. Although first observed in 1949 and subsequently studied and mapped further through the 20th century using technologies of the day, newly acquired multibeam data reveal intricate details.  

Surprisingly, the channel width of ~5 km and ~100 m depth is maintained throughout its length.  It is a remarkably straight channel with no significant meanders, despite the fact that it runs on a gradient of <0.05° and has clear influences of Coriolis, as indicated by its higher and better developed western levee. Frequent levee collapses are apparent, and the channel floor hosts a thalweg with possible point-bar deposits around channel bends. Its formation has always been presumed to be a result of glaciogenic outwash from the Labrador margin but this new evidence suggests the Hudson Strait as a more likely principal source.  Few tributaries enter the channel but the Imarssuak Mid-Ocean Channel feeds into NAMOC just south of Greenland.  Evidence of a late glacial outwash event or events appear to be prominent in the northern reaches of the channel. The mouth of the channel is relatively unremarkable and simply dissipates into the Sohm Abyssal Plain in a series of distributary channels.