Egc

Fig. 28.5 Surface circulation schematic for the summertime boundary current system of the Irminger Sea. Numbered hydrographic sections are from JR105, also indicated on Fig. 28.1. Solid lines show the paths of the East Greenland Current (EGC, blue), the East Greenland Coastal Current (EGCC, green) and the Irminger Current (IC, red; not discussed here - see Sutherland and Pickart 2007); dashed lines indicate possible flow paths induced by bathymetric or wind effects; thin blue ellipses show inferred recirculations around major troughs on the shelf. North of the Kangerdlussuaq Trough (KT) the EGCC's presence is uncertain, though it is likely weaker than what is observed farther south

Fig. 28.5 Surface circulation schematic for the summertime boundary current system of the Irminger Sea. Numbered hydrographic sections are from JR105, also indicated on Fig. 28.1. Solid lines show the paths of the East Greenland Current (EGC, blue), the East Greenland Coastal Current (EGCC, green) and the Irminger Current (IC, red; not discussed here - see Sutherland and Pickart 2007); dashed lines indicate possible flow paths induced by bathymetric or wind effects; thin blue ellipses show inferred recirculations around major troughs on the shelf. North of the Kangerdlussuaq Trough (KT) the EGCC's presence is uncertain, though it is likely weaker than what is observed farther south series of high-resolution hydrographic and velocity sections. They suggest that the EGCC is an inner branch of the EGC that forms south of Denmark Strait, and they argue that bathymetric steering and strong along-shelf wind forcing cause the EGC to split at Denmark Strait. By combining the EGCC and EGC transports, they find a roughly constant seawater flux over their study area (~2 Sv), and a southwards increase of freshwater flux, by ~60%, from 59 to 96 mSv, that is explained by a budget accounting for meltwater runoff, melting sea-ice, melting icebergs, and precipitation minus evaporation (P-E).

Thus far, all observations of the EGCC were made in summer months when the region was accessible to research vessels. We offer next the first observation of the EGCC's likely existence in the winter. In February-March 2000, a group of sea-ice-capable surface drifting buoys (PIMMs: Polar Ice Motion Monitors; Hawker 2005) were deployed from RV Jan Mayen onto ice floes in the sea ice in the Greenland Sea between 72-75° N. The PIMMs were equipped with air temperature sensors on their top plate and sea surface temperature sensors on the underside.

50 60 70 80 90 100

Day of Year (2000)

Fig. 28.6 Speed of PIMMs drifter in winter 2000. See text (Section 28.3) for concordance between day number and track (Fig. 28.1)

50 60 70 80 90 100

Day of Year (2000)

Fig. 28.6 Speed of PIMMs drifter in winter 2000. See text (Section 28.3) for concordance between day number and track (Fig. 28.1)

One of these (the track is shown in Fig. 28.1) followed the EGC as far as Denmark Strait, then crossed onto the shelf and remained roughly in the centre of the shelf, taking 20 days to travel between 67-65° N. Its temperature records confirmed that it remained on its ice floe (and not in the water) until it expired. Its speed is shown in Fig. 28.6.

The first half of the record is when the drifter is in the EGC in the Greenland and Iceland Seas. Between days 76 and 84 it is moving slowly, in northern Denmark Strait, and then on the eastern edge of the shelf. From day 84 to the end of the record, it is moving south-westwards in the centre of the shelf at about 1 m s-1, with high variability. The speed is too high to be due directly to wind forcing so we attribute this (mainly) to advection by the EGCC, but we suggest that the variability in speed may be a response to synoptic meteorological variability, probably by forcing the drifter (and its ice floe) back and forth across the EGCC and so, occasionally, it is outside the current core.

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