An analysis of buoy drift in the northern North Atlantic with detection of drogue loss events

Abstract

Buoy drift in the northern North Atlantic and adjacent seas was analyzed to study the surface‐layer currents and wind forcing. Two drifters with drogues at depths of 10 and 75 metres were deployed in the Denmark Strait (DS) in August 1993. The buoys drifted in the East and West Greenland Currents (EGC and WGC) and in the ocean basins south of Greenland and Iceland. The drogue loss events of the drifters were estimated from the linear relationship between the drift and geostrophic wind velocities. The linear model produces a set of parameters describing the relationship between the drift and the wind. These parameters were investigated to determine possible drogue loss events. The buoys seem to have lost their drogues near Cape Farewell in December 1993. Currents were calculated with the linear model. Strong current velocities of 0.5 m/s with stable directions were obtained in the EGC, while the currents were weaker, around 0.05 m/s, and the direction fluctuated more in the DS and the open ocean. The speed ratio between the wind‐induced drift and the geostrophic wind ranged from 0.6% in the DS to around 1% in the EGC for drogued drift, while it was about 1.6% in the open ocean for non‐drogued drift. The turning angle between the drift and the geostrophic wind fluctuated by some tens of degrees in coastal conditions, but was close to zero in the open ocean. According to the distribution of the relative drift directions, the drogued drift was directed with the wind 50% of the time while the undrogued drift was directed with the wind 80% of the time.