Northwest Atlantic Mid-Ocean Channel
Encyclopedia
The Northwest Atlantic Mid-Ocean Channel (NAMOC) is the main body of a turbidity current
system of channels and canyons running on the sea bottom from the Hudson Strait
, through the Labrador Sea
and ending at the Sohm Abyssal Plain
in the Atlantic Ocean
. Contrary to most other such systems which fan away from the main channel, numerous tributaries
run into the NAMOC and end there. The density of those tributaries is the highest near the Labrador Peninsula
, but the longest tributary, called Imarssuak Mid-Ocean Channel (IMOC), originates in the Atlantic Ocean.
Most topography data on the NAMOC originate from wide-range sonar
scans. With a total length of about 3800 km (2,361 mi), NAMOC is one of the longest underwater channels in the world. It is 100–200 meters deep and 2–5 km wide at the channel floor. The rising levee
s of the NAMOC (about 100 m above the sea bed) often hinder confluence of some tributaries, which instead run along NAMOC for hundreds of kilometers. Its western (right-hand, max. height 250 m) levee rises some 100 meters above the eastern one (max. height 150 m). This asymmetry is attributed to the Coriolis effect
affecting the turbidity currents, which reach velocities of 6–8.5 m/s and deposit silt and clay over the channel. The levee is absent in some parts of the NAMOC, for example between 56°N and 57°N, due to the local side-flows of sand.
The meandering of the NAMOC is relatively small compared to other underwater channels, such as Amazon Canyon
. It is more developed in the northern part with a period increasing from 25 km between 59°45'N and 56°N to 50 km between 56°N and 54°30'N. The channel becomes on average more straight towards the south, but it still contains abrupt turns due to local seamount
s sea bed fractures.
Turbidity current
A turbidity current is a current of rapidly moving, sediment-laden water moving down a slope through water, or another fluid. The current moves because it has a higher density and turbidity than the fluid through which it flows...
system of channels and canyons running on the sea bottom from the Hudson Strait
Hudson Strait
Hudson Strait links the Atlantic Ocean to Hudson Bay in Canada. It lies between Baffin Island and the northern coast of Quebec, its eastern entrance marked by Cape Chidley and Resolution Island. It is long...
, through the Labrador Sea
Labrador Sea
The Labrador Sea is an arm of the North Atlantic Ocean between the Labrador Peninsula and Greenland. The sea is flanked by continental shelves to the southwest, northwest, and northeast. It connects to the north with Baffin Bay through the Davis Strait...
and ending at the Sohm Abyssal Plain
Sohm Abyssal Plain
The Sohm Abyssal Plain is in the North Atlantic and has an area of around ....
in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Contrary to most other such systems which fan away from the main channel, numerous tributaries
Tributary
A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...
run into the NAMOC and end there. The density of those tributaries is the highest near the Labrador Peninsula
Labrador Peninsula
The Labrador Peninsula is a large peninsula in eastern Canada. It is bounded by the Hudson Bay to the west, the Hudson Strait to the north, the Labrador Sea to the east, and the Gulf of Saint Lawrence to the south-east...
, but the longest tributary, called Imarssuak Mid-Ocean Channel (IMOC), originates in the Atlantic Ocean.
Most topography data on the NAMOC originate from wide-range sonar
Side-scan sonar
Side-scan sonar is a category of sonar system that is used to efficiently create an image of large areas of the sea floor...
scans. With a total length of about 3800 km (2,361 mi), NAMOC is one of the longest underwater channels in the world. It is 100–200 meters deep and 2–5 km wide at the channel floor. The rising levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...
s of the NAMOC (about 100 m above the sea bed) often hinder confluence of some tributaries, which instead run along NAMOC for hundreds of kilometers. Its western (right-hand, max. height 250 m) levee rises some 100 meters above the eastern one (max. height 150 m). This asymmetry is attributed to the Coriolis effect
Coriolis effect
In physics, the Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right...
affecting the turbidity currents, which reach velocities of 6–8.5 m/s and deposit silt and clay over the channel. The levee is absent in some parts of the NAMOC, for example between 56°N and 57°N, due to the local side-flows of sand.
The meandering of the NAMOC is relatively small compared to other underwater channels, such as Amazon Canyon
Amazon Canyon
The Amazon Canyon is a submarine canyon within the Amazon Fan in the Atlantic Ocean, located approximately from the mouth of the Amazon River, near South America. It covers an area of . It was formed in the mid to late Miocene period. The canyon is believed to have formed through mass failures,...
. It is more developed in the northern part with a period increasing from 25 km between 59°45'N and 56°N to 50 km between 56°N and 54°30'N. The channel becomes on average more straight towards the south, but it still contains abrupt turns due to local seamount
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...
s sea bed fractures.