Upstream Sources of the Denmark Strait Overflow: Observations from a High-Resolution Mooring Array
Upstream Sources of the Denmark Strait Overflow: Observations from a High-Resolution Mooring Array
Abstract:
We present the first results from a densely instrumented mooring array
upstream of the Denmark Strait sill, extending from the Iceland
shelfbreak to the Greenland shelf. The array was deployed from
September 2011 to August 2012, and captured the vast majority of
overflow water denser than 27.8 kg m-3 approaching the sill. The mean
transport of overflow water over the length of the deployment was 3.54
± 0.16 Sv. Of this, 0.58 Sv originated from below sill depth,
revealing that aspiration takes place in Denmark Strait. We confirm
the presence of two main sources of overflow water: one approaching
the sill in the East Greenland Current and the other via the North
Icelandic Jet. Using an objective technique based on the hydrographic
properties of the water, the transports of these two sources are
estimated. We further partition the East Greenland Current source into
that carried by the shelfbreak jet versus that transported by a
separated branch of the current on the Iceland slope. Over the course
of the year the total overflow transport through the array varies
considerably less than the flux in each of the branches, demonstrating
that compensation takes place among the pathways. This is especially
true for the two East Greenland Current branches whose transports vary
out of phase with each other on weekly and longer time scales. We
argue that wind forcing plays a large role in this partitioning.
upstream of the Denmark Strait sill, extending from the Iceland
shelfbreak to the Greenland shelf. The array was deployed from
September 2011 to August 2012, and captured the vast majority of
overflow water denser than 27.8 kg m-3 approaching the sill. The mean
transport of overflow water over the length of the deployment was 3.54
± 0.16 Sv. Of this, 0.58 Sv originated from below sill depth,
revealing that aspiration takes place in Denmark Strait. We confirm
the presence of two main sources of overflow water: one approaching
the sill in the East Greenland Current and the other via the North
Icelandic Jet. Using an objective technique based on the hydrographic
properties of the water, the transports of these two sources are
estimated. We further partition the East Greenland Current source into
that carried by the shelfbreak jet versus that transported by a
separated branch of the current on the Iceland slope. Over the course
of the year the total overflow transport through the array varies
considerably less than the flux in each of the branches, demonstrating
that compensation takes place among the pathways. This is especially
true for the two East Greenland Current branches whose transports vary
out of phase with each other on weekly and longer time scales. We
argue that wind forcing plays a large role in this partitioning.