A long-lived eddy in the Iceland Basin 1998

A survey was made of a large (100 km) eddy in the Iceland Basin in June 1998. In situ observations from a shallow, undulating conductivity‐temperature‐depth profiler and vessel‐mounted acoustic Doppler current profiler were used to generate sea surface height along two TOPEX/Poseidon tracks. Comparisons were made with the altimetric measurements to arrive at an estimate of the sea surface height for 6 years of TOPEX/Poseidon altimeter data. The 3 month track of a drifting buoy was used to estimate the location of the center of the eddy. Comparison with the altimetric sea surface height showed that the position of the eddy correlated well with an elevated sea surface signal of 25–30 cm. Having identified this signal as a characteristic signature of eddies, inspection of the 6 year record revealed other similar features whose presence and longevity varied considerably. The presence or absence of eddies appeared to link with the large‐scale variability of the subpolar gyre: when the gyre expanded (e.g., 1993–1994), the North Atlantic Current tended to follow a southerly route and eddies in the Iceland Basin were few and weak, especially compared to periods when the gyre contracted (e.g., 1992–1993 and 1996–1998) and the North Atlantic Current turned through the Iceland Basin: then saltier water from the eastern North Atlantic extended westward into the Iceland Basin and into large, long‐lived eddies.