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JOURNAL OF PHYSICAL OCEANOGRAPHY 
VOLUME 50 
72°N 
strait and more cyclones west of this. Satellite altimetry data 
nave revealed enhanced levels of surface eddy kinetic energy in 
:he vicinity of the strait (Hoyer and Quadfasel 2001; Hävik 
et al. 2017b). 
A series of recent papers have further characterized 
che high-frequency variability of the DSOW at the sill. Two 
dominant features have been identified, referred to as boluses 
and pulses. The former corresponds to the passage of a large 
‚enses of overflow water and are associated with cyclonic 
circulation (von Appen et al. 2017). Mastropole et al. (2017) 
identified boluses in 46 out of 111 transects across the strait 
occupied since 1990. These features export the very densest 
DSOW. Pulses correspond to a thinning and acceleration of the 
DSOW layer, and are associated with anticyclonic circulation 
‘von Appen et al. 2017). The two types of features have been 
identified in a high-resolution numerical model, with charac- 
:eristics similar to the observations (Almansi et al. 2017). Both 
the boluses and pulses result in increased transport of DSOW 
over a period of several days (von Appen et al. 2017). Almansi 
st al. (2020) have shown that the surges in transport result in 
:he generation of cyclones downstream of the sill. These are 
:he well-known ““DSOW cyclones’” that emanate from the 
strait and propagate southward along the East Greenland 
zontinental slope (Bruce 1995; Spall and Price 1998; von 
Appen et al. 2017). 
The numerical study of Spall et al. (2019) determined that 
ooluses and pulses are part of a single dynamical process, 
associated with baroclinic instability of the hydrographic 
front in Denmark Strait. This front divides the southward- 
lowing water emanating from the Nordic Seas and the 
1orthward-flowing NIIC. The instability process results in 
irontal meanders that propagate southwestward through the 
strait. Meander troughs are associated with boluses, whereby 
:he NIIC shifts toward Iceland and more overflow water is 
present in the center of the strait. Meander crests are asso- 
ciated with pulses, when the NIIC moves farther into the 
strait toward Greenland. Spall et al. (2019) demonstrated that 
:his process is dictated by the interplay between the confluent 
nean flow in the strait that tends to sharpen the front, and the 
5aroclinic instability which works to relax the front. These 
'esults show that the dynamics of the DSOW are closely tied 
:o those of the NIIC. 
Based on the large number of shipboard occupations of 
:he Lätrabjarg transect across Denmark Strait (Fig. 1), we 
10w have a good characterization of the two-dimensional 
ıydrographic structure across the strait. However, we lack 
an analogous view of the kinematic structure. Over the 
vears, moorings have been deployed in the deepest part of 
‘he sill, which is referred to as the trough (see Fig. 4). These 
me series have provided information on the vertical structure 
ınd transport of the overflow water (e.g., Jochumsen et al. 
1017; von Appen et al. 2017; Spall et al. 2019). Recently a five- 
mMooring array was deployed on the western flank of the trough. 
Using empirical orthogonal function analysis on the yearlong 
velocity time series, Jochumsen et al. (2017) found that the 
äirst mode reflects a barotropic flow that pulses in time, the 
second mode represents lateral shifts of the flow, and the third 
mode corresponds to the mesoscale eddy features noted above, 
70° N 
58° 
S6°MN 
ART TE 
64° 
36° 
31°W 
26°W 
21° W 
(6° 
FIG. 1. Schematic circulation in the vicinity of Denmark Strait, 
ıncluding the two branches of the East Greenland Current 
‘EGC)—the shelfbreak EGC and separated EGC— as well as the 
North Icelandic Jet (NIJ) and the North Icelandic Irminger 
Current (NIIC). The blue line across Denmark Strait is the 
Lätrabjarg transect from Mastropole et al. (2017). The bathym- 
etry is from ETOPO2v2. Bathymetry contours are in meters. 
of the historical data suggests that the water stems from the 
Greenland Sea (Huang et al. 2020). Based on a large collection 
of shipboard transects occupied over 15 years, Semper et al. 
(2019) documented that the NIJ steadily increases in transport, 
particularly in the downstream of Kolbeinsey Ridge (Fig. 1), as 
it flows toward Denmark Strait, accounting for a sizable frac- 
(‚on of the dense water that overflows the sill. 
Using data from a yearlong mooring array across the 
Blosseville Basin (roughly 200 km north of the sill), Harden 
et al. (2016) calculated mean transports for the three indi- 
vidual pathways: 1.50 + 0.16Sv for the shelfbreak EGC, 
1.04 + 0.15 Sv for the separated EGC, and 1.00 + 0.17 Sv for 
the NIJ. There was very little seasonal variation, in line with 
che weak seasonality observed at the sill (JTochumsen et al. 
2012). However, Harden et al. (2016) revealed that the trans- 
»orts of the three branches vary on intraseasonal time scales, 
and that they tend to compensate each other such that the total 
overflow transport remains fairly steady. They argued that 
wind stress curl forcing causes the compensation between the 
NIJ and the two EGC branches. 
On synoptic time scales, the flow of DSOW is highly ener- 
getic (Smith 1976; Bruce 1995; Rudels et al. 1999; Girton and 
Sanford 2003; Käse et al. 2003; von Appen et al. 2017). Using 
ıhe mooring data from the aforementioned Blosseville Basin 
array, Huang et al. (2019) demonstrated that high-frequency 
variability is driven by mean-to-eddy baroclinic conversion at 
he shoreward edge of the NIJ. Using a yearlong mooring array 
ın Denmark Strait, Moritz et al. (2019) resolved the passage of 
addies, finding more anticyclones in the deepest part of the 
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