Writing in Nature Geoscience the scientists describe how they reached their conclusions after analysing cores of sediment taken from the seabed. Sediment builds up as seawater drops its burden of particles—dust and other debris carried into the sea by wind and erosion of the continents. Strong winds can create strong currents that are capable of carrying larger particles than the weaker currents created by weaker winds.
Thus, the particle sizes of sediment obtained by taking samples of the mud at different depths in the sea bed can provide an indication of prevailing current speed, and in some cases the driving wind speed, at the time the sediment was laid down. However, this happens only where the current driven by the wind reaches all the way to the seabed and there are not many areas of the world where this occurs in the deep sea.
Read more at: Phys.org