Ocean Science
www.ocean-sci.net
1812-0784
1812-0792
2
2
2006
10.5194/os-2-291-2006
http://www.ocean-sci.net/2/291/2006/
http://www.ocean-sci.net/2/291/2006/os-2-291-2006.html
http://www.ocean-sci.net/2/291/2006/os-2-291-2006.pdf
291
304
2006-12-11
High resolution modelling of the North Icelandic Irminger Current (NIIC)
K. Logemann
I. Harms
harms@ifm.uni-hamburg.de
Centre for Marine and Climate Research, Institute for Oceanography, University of Hamburg, Bundesstraße 53, 20146 Hamburg, Germany
now at: University of Iceland, Askja, Sturlugata 7, 101 Reykjavik, Iceland
The northward inflow of Atlantic Water through Denmark Strait – the North
Icelandic Irminger Current (NIIC) – is simulated with a numerical model of
the North Atlantic and Arctic Ocean. The model uses the technique of
adaptive grid refinement which allows a high spatial resolution (1 km
horizontal, 10 m vertical) around Iceland. The model is used to assess time
and space variability of volume and heat fluxes for the years 1997–2003.
Passive tracers are applied to study origin and composition of NIIC water
masses.
<br><br>
The NIIC originates from two sources: the Irminger Current, flowing as part
of the sub-polar gyre in 100–500 m depth along the Reykjanes Ridge and
the shallow Icelandic coastal current, flowing north-westward on the
south-west Icelandic shelf. The ratio of volume flux between the deep and
shallow branch is around 2:1. The NIIC continues as a warm and saline branch
northward through Denmark Strait where it entrains large amounts of polar
water due to the collision with the southward flowing East Greenland
Current. After passing Denmark Strait, the NIIC follows the coast line
eastward being an important heat source for north Icelandic waters.
<br><br>
At least 60% of the temporal temperature variability of north Icelandic
waters is caused by the NIIC. The NIIC volume and heat transport is highly
variable and depends strongly on the wind field north-east of Denmark
Strait. Daily means can change from 1 Sv eastward to 2 Sv westward within a
few days. Highest monthly mean transport rates occur in summer when winds
from north are weak, whereas the volume flux is reduced by around 50% in
winter. Summer heat flux rates can be even three times higher than in
winter. The simulation also shows variability on the interannual scale. In
particular weak winds from north during winter 2002/2003 combined with mild
weather conditions south of Iceland led to anomalous high NIIC volume
(+40%) and heat flux (+60%) rates. In this period, simulated north
Icelandic water temperatures are at least 0.5 K warmer than average.
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