The Irminger current as represented by the Mariano Global Surface Velocity Analysis (MGSVA). The Irminger current is the northward flowing component of the N. Atlantic subpolar gyre. It transports relatively warm water that mixes with colder water transported by the E. Greeland current from the Arctic Ocean. Click here for example plots of seasonal averages.
The Irminger Current (IC), located above the western slope of the Reykjanes Ridge, branches from the North Atlantic Current at about 26°W (Bersch et al. 1999). According to Bersch (1995), the current is deflected north when it is west of the ridge crest and south when it is east of it. This is due to the conservation of potential vorticity when crossing the Reykjanes Ridge. Ship drift observations and a model (Langseth and Boyer 1972) support this observation. Some charts do not show the southward flow; this may be an indication that there is a relatively strong temporal variability of the IC in crossing the ridge (Bersch 1995). Krauss (1995) used CTD profiles and buoys drouged at 100 m to study the flow of the Irminger Current. He found that it branches along the Reykjanes Ridge between 60°N and 62°N. The buoys released off the eastern side of the ridge moved into the Norwegian Sea. Buoys released west of 28°W traveled toward the Greenland continental slope and eventually are advected by the East Greenland Current.

As it encounters the Rockall Plateau at about 24°W, the Irminger Current flows to the west of the Eriador Seamount and enters the Iceland Basin above the Maury Channel with speeds of about 25 cm s-1 (Bersch 1995). At this point it has a sea surface height variability of more than 7 cm, which increases to the northeast. In the region of the eastern branch of the current there is no enhanced variability, and the speeds are below 15 cm s-1. This suggests that the Irminger Current weakens as it circulates cyclonically around the Iceland Basin (Bersch 1995). The western branch of the current, on the other hand, is characterized by relatively stagnant mean currents but vigorous eddies (Krauss 1995).

The Irminger Current transports relatively salty (34.9-35.0 psu) and warm (4°-6°C) water offshore from the East Greenland Current. This water is a mixture of Irminger Sea Water and the warmer and saltier water transported from the east (Reynaud et al. 1995). Heat loss, fresh water input, and mixing eventually transform the upper water masses of the Irminger Current back into Irminger Sea Water. Salt fingering is widespread in the Irminger Current, and this double diffusive process enhances mixing (Krauss 1995).

Clarke (1984, as cited in Krauss 1995) examined current measurements and a hydrographic section that ran from Cape Farewell to Labrador. Based on this information, he concluded that the total current system in the Irminger Sea carries 27-33 Sv southward: 11 Sv of Irminger Current water, 7-9 Sv of North Atlantic Deep Water, 2 Sv of Labrador Sea Water, and 5-6 Sv of North Atlantic Bottom Water (Krauss 1995). Krauss (1995), however, found that the Irminger Current transports not 11 Sv, but 17.7 Sv of Northeast Atlantic Water and Labrador Sea Water across 62°N. Of this amount, 9.6 Sv flow into the Irminger Basin and 8.1 Sv flow into the Iceland Basin. Bersch (1995) obtained an even greater value for the transport of the Irminger Current: 28 Sv, of which 10 Sv are Labrador Sea Water and 14 Sv are Subpolar Mode Water. More research on this current is needed to gain a better understanding of it.

References

Bersch, M., 1995: On the circulation of the northeastern North Atlantic. Deep-Sea Research Part I, 42, 1583-1607.

Bersch, M., J. Meincke, and A. Sy, 1999: Interannual thermohaline changes in the northern North Atlantic 1991-1996. Deep-Sea Research Part II, 46, 55-75.

Clarke, R.A., 1984: Transport through the Cape Farewell-Flemish Cap Section, Rapp. P. V. Reun. Cons. Int. Explor. Mer., 185, 120-130.

Krauss, W., 1995: Mixing in the Irminger Sea and in the Iceland Basin. Journal of Geophysical Research, 100, 10851-10871.

Langseth, M.G. and D. Boyer, 1972: The effect of the Reykjanes Ridge on the flow of water above 2000 meters. In: Studies in physical oceanography - a tribute to George Wust on his 80th birthday, Vol. 1, A.L. Gordon, editor, Gordon and Breach, pp. 93-114.

Reynaud, T.H., A.J. Weaver, and R.J. Greatbatch, 1995: Summer mean circulation in the northwestern Atlantic Ocean. Journal of Geophysical Research, 100, 779-816.