AN ANALYSIS OF BUOY DRIFT IN THE NORTHERN NORTH-ATLANTIC WITH DETECTION OF DROGUE LOSS EVENTS

Buoy drift in the northern North Atlantic and adjacent seas was analyz ed to study the surface-layer currents and wind forcing. Two drifters with drogues at depths of 10 and 75 metres were deployed in the Denmar k Strait (DS) in August 1993. The buoys drifted in the East and West G reenland Currents (EGG and WGC) and in the ocean basins south of Green land and Iceland. The drogue loss events of the drifters were estimate d from the linear relationship between the drift and geostrophic wind velocities. The linear model produces a set of parameters describing t he relationship between the drift and the wind These parameters were i nvestigated to determine possible drogue loss events. The buoys seem t o have lost their drogues near Cape Farewell in December 1993. Current s were calculated with the linear model. Strong current velocities of 0.5 m/s with stable directions were obtained in the EGG, while the cur rents 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 oc ean for non-drogued drift. The turning angle between the drift and the geostrophic wind fluctuated by some tens of degrees in coastal condit ions, but was close to zero in the open ocean. According to the distri bution of the relative drift directions, the drogued drift was directe d with the wind 50% of the time while the undrogued drift was directed with the wind 80% of the time.