The East Greenland Spill Jet as an important component of the Atlantic Meridional Overturning Circulation

Abstract

The recently discovered East Greenland Spill Jet is a bottom-intensified current on the upper continental slope south of Denmark Strait, transporting intermediate density water equatorward. Until now the Spill Jet has only been observed with limited summertime measurements from ships. Here we present the first year-round mooring observations demonstrating that the current is a ubiquitous feature with a volume transport similar to the well-known plume of Denmark Strait overflow water farther downslope. Using reverse particle tracking in a high-resolution numerical model, we investigate the upstream sources feeding the Spill Jet. Three main pathways are identified: particles flowing directly into the Spill Jet from the Denmark Strait sill; particles progressing southward on the East Greenland shelf that subsequently spill over the shelfbreak into the current; and ambient water from the Irminger Sea that gets entrained into the flow. The two Spill Jet pathways emanating from Denmark Strait are newly resolved, and long-term hydrographic data from the strait verifies that dense water is present far onto the Greenland shelf. Additional measurements near the southern tip of Greenland suggest that the Spill Jet ultimately merges with the deep portion of the shelfbreak current, originally thought to be a lateral circulation associated with the sub-polar gyre. Our study thus reveals a previously unrecognized significant component of the Atlantic Meridional Overturning Circulation that needs to be considered to understand fully the ocean's role in climate.

On the hydrography of Denmark Strait

“…(An earlier version of this figure appears in von Appen et al . [], but is only discussed briefly regarding a specific feature not considered in the present study.) We now describe the major features of the mean section and discuss the seasonality as well as interannual trends in the water masses in the Strait.…”

Observing the Atlantic Meridional Overturning Circulation yields a decade of inevitable surprises

“…2 the Meridional Overturning Variability Experiment (MOVE) array at 16°N (34), the Deep Western Boundary Current (DWBC) arrays at around 39°N (35) and 53°N (36), the 34.5°S array (37,38), the use of altimetry and Argo at around 41°N (39,40), and the Observatoire de la Variabilité Interannuelle et Décennale en Atlantique Nord (OVIDE) hydrographic sections (41). Recently, a new component of the AMOC, the so-called East Greenland spill jet, has been identified from a year of mooring observations (42), but its importance in the long-term for the overall AMOC remains to be confirmed.…”

Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

“…Percentages of up to 20% of PIW are present within the 10 realm of DSOW (Fig. 4f), supporting the existence of entrainment of East Greenland shelf waters into DSOW (Tanhua et al, 2008;Falina et al, 2012;von Appen et al, 2014). PIW is also found in the continental shelves of Greenland and Canada, with the greatest contribution found on the Canadian shelf.…”