Ocean currents

Surface circulation around Iceland has been measured using surface drifters. The North Atlantic Drift flows from the south containing warm and saline Atlantic water. When it arrives at the south coast, it splits into two branches. One branch heads east towards the Iceland-Faroe Ridge and follows it towards the Faroes. The other branch, the Irminger Current, flows westwards. Part of it follows the Reykjanes Ridge southwards again, then crosses the ridge and flows northwards along the western slope of the ridge. The part that flows closer to land continues straight westwards, and when it passes Reykjanes it continues northwards along the coast and joins the offshore branch again. Most of this water crosses the Irminger Sea and then follows the East Greenland slope southwards. A relatively small amount continues through the Denmark Strait, mainly over the shelf, and then flows eastwards along the north coast. North of Iceland it is called the North Icelandic Irminger Current. The mean speed of this current has been measured 5-10 cm/s.

The East Greenland Current flows from the north along the shelf and slope of East Greenland, bringing cold water with low salinity close to Iceland. Most of this water mass flows through the Denmark Strait. A small but highly variable amount, however, spills into the Iceland Sea and occasionally covers the shelf off the north coast. This current is swift, with mean flow speeds exceeding 15 cm/s at the surface. A slow cyclonic gyre is stationed over the Iceland Plateau in the Iceland Sea, with mean speeds of the order of 2 cm/s. Over the slope north and east of Iceland, there is a flow of relatively cold waters with mean speeds close to the surface of about 10 cm/s. This is the East Icelandic Current.

There is a coastal water mass that is most visible as a low salinity band close to the coast during spring and summer, when runoff is at its maximum and mixing in the ocean at its minimum. This, however, is probably not a separate current, but flows together with the Irminger current in a clockwise manner around Iceland. As the current passes by a fjord mouth it is partially steered into the fjords. This leads to an inflow into the fjords along the right hand side of the fjord when looking into the fjord from outside. On the other side there is an outflow of water.

The fastest currents around Iceland are not at the surface, but at the bottom over the Iceland-Faroe Ridge and especially in the Denmark Strait. These currents are the results of deep water formation occurring north of the Greenland-Scotland Ridge. This deep water fills up the deep part of the oceans north of the ridge until it spills over the Greenland-Scotland Ridge and into the North Atlantic. The largest source of this water flows through the Denmark Strait at a rate of 3.7 Sv (1 Sv = 1 million m³/s). Mean speeds in the Denmark Strait have been observed to exceed 50 cm/s. Part of this flow has recently been discovered to enter the Denmark Strait along the Icelandic slope in a swift (mean speeds of about 15 cm/s) current that has been traced to the Kolbeinsey Ridge. A smaller amount (0.6 Sv) of water crosses the Iceland-Faroe Ridge just east of the Icelandic slope with mean speeds of about 50 cm/s.

References and further information

References: (Jónsson 2007), (Jónsson & Valdimarsson 2004), (Jónsson & Valdimarsson 2005), (Macrander et al. 2005), (Perkins et al., 1998), (Poulain et al., 1996), (Valdimarsson & Malmberg, 1999)

For full citation and further information on the ecosystem in general see this page

Steingrímur Jónsson, The Marine Research Insitute/University of Akureyri