Upstream sources of the Denmark Strait Overflow : observations from a high-resolution mooring array
2016-02-19,
Harden, Benjamin E.,
Pickart, Robert S.,
Valdimarsson, Héðinn,
Våge, Kjetil,
de Steur, Laura,
Richards, Clark G.,
Bahr, Frank B.,
Torres, Daniel J.,
Børve, Eli,
Jonsson, Steingrimur,
Macrander, Andreas,
Østerhus, Svein,
Håvik, Lisbeth,
Hattermann, Tore
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 July 2012, and captured the vast majority of overflow water denser than 27.8 kgm-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 found to be
2.54 ± 0.17 Sv and 1.00 ± 0.17 Sv, respectively. We further partition the East Greenland Current source
into that carried by the shelfbreak jet (1.50 ± 0.16 Sv) versus that transported by a separated branch of
the current on the Iceland slope (1.04 ± 0.15 Sv). Over the course of the year the total overflow transport is more consistent than the transport in either branch; compensation takes place among the pathways that
maintains a stable total overflow transport. 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 role in this partitioning.