My apologies if this is drifting into the technical, but when looking at the debris field, bear in mind that wind and swell are both factors to consider, after the debris has entered the water, even independent of the direction of prevailing currents. Most of the studies on this subject are to do with oil spills, but I guess are relevant here too. The net effect of wind will be between 2.5% and 4.4% of prevailing wind speed, depending on wave interaction, with a mean average of 3.5%, so wind alone will cause floating objects, such as an oil spill or debris field to drift about 1knot per 30 knots of wind. Swell also has an effect, although less pronounced.