Subglacial channel
Encyclopedia
A subglacial meltwater channel is a channel beneath an ice mass, like ice sheet
s and valley glaciers, roughly parallel to the main ice direction. These meltwater channels can have different sizes, ranging from very small channels of a metre deep and wide to big valleys which can be up to a kilometres wide. The dimensions of these channels are regulated by several factors, like: temperature, meltwater volume, debris content in the water, ice wall
closure rates and squeezing of fluidized sediment (Menzies, 2002).
In the scientific literature
three forms of sub glacial melt water channels are commonly mentioned.
The first type of channels is the R-channels (Röthlisberger, 1972). These are semi-circular channels cut upward into the ice. The balance between channel enlargement by viscous heating and closure by ice deformation when the channels are water-filled reflects their size and water pressure.
The second type mentioned is the H-channels. These channels are broad, flat channels cut upward into the ice that tends to follow local bed slope. Such channels form where water flows at atmospheric pressure
beneath thin ice and on steep downglacier bedslopes.
The last type, the N-channels (Nye, 1973), are incised into bedrock, perhaps suggesting long-term channel stability under some alpine glaciers.
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
s and valley glaciers, roughly parallel to the main ice direction. These meltwater channels can have different sizes, ranging from very small channels of a metre deep and wide to big valleys which can be up to a kilometres wide. The dimensions of these channels are regulated by several factors, like: temperature, meltwater volume, debris content in the water, ice wall
Ice wall
Ice wall may refer to:* Any wall made of ice.* According to the Flat Earth Society the Ice Wall is a wall that encloses the perimeter of a flat, circular earth. Said to be formed by intense cold and pressure, this is used to explain why the ocean doesn't fall off the edge of the world on the flat...
closure rates and squeezing of fluidized sediment (Menzies, 2002).
In the scientific literature
Scientific literature
Scientific literature comprises scientific publications that report original empirical and theoretical work in the natural and social sciences, and within a scientific field is often abbreviated as the literature. Academic publishing is the process of placing the results of one's research into the...
three forms of sub glacial melt water channels are commonly mentioned.
The first type of channels is the R-channels (Röthlisberger, 1972). These are semi-circular channels cut upward into the ice. The balance between channel enlargement by viscous heating and closure by ice deformation when the channels are water-filled reflects their size and water pressure.
The second type mentioned is the H-channels. These channels are broad, flat channels cut upward into the ice that tends to follow local bed slope. Such channels form where water flows at atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
beneath thin ice and on steep downglacier bedslopes.
The last type, the N-channels (Nye, 1973), are incised into bedrock, perhaps suggesting long-term channel stability under some alpine glaciers.