Upstream Sources of the Denmark Strait Overflow: Observations from a High-Resolution Mooring Array

We present the first results from a densely instrumented mooring arrayupstream of the Denmark Strait sill, extending from the Icelandshelfbreak to the Greenland shelf. The array was deployed fromSeptember 2011 to August 2012, and captured the vast majority ofoverflow water denser than 27.8 kg m-3 approaching the sill. The meantransport 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 confirmthe presence of two main sources of overflow water: one approachingthe sill in the East Greenland Current and the other via the NorthIcelandic Jet. Using an objective technique based on the hydrographicproperties of the water, the transports of these two sources areestimated. We further partition the East Greenland Current source intothat carried by the shelfbreak jet versus that transported by aseparated branch of the current on the Iceland slope. Over the courseof the year the total overflow transport through the array variesconsiderably less than the flux in each of the branches, demonstratingthat compensation takes place among the pathways. This is especiallytrue for the two East Greenland Current branches whose transports varyout of phase with each other on weekly and longer time scales. Weargue that wind forcing plays a large role in this partitioning.