DEEP SEA BEDFORMS AND THEIR BERING ON BOTTOM CURRENTS,IN SOUTHEASTERN ICELAND-FAROE RIDGE

The Iceland-Faroe Ridge is located between the Norwegian Sea and the Northeast Atlantic Ocean, with a water depth of 600~1 200 m at its southeastern flank, where the Norwegian Sea Deep Water (NSDW) flows through the Faroe-Shetland and Faroe Bank Channels (FSC, FBC). Persistent strong bottom currents acting on the seafloor in these areas can transport coarse sediments as big as sands and gravels. A large variety of sedimentary bedforms including sand waves, barchan dunes, sand ribbons and streamers, comet marks, sand shadows and sand sheets, are identified using sidescan sonar images, seismic profiles, seabed photographs. Five areas with different bedforms are recognized along the channels. Some large scale bedforms such as sand dunes and sand ribbons formed during the Atlantic Stage of the Holocene in the northeast Atlantic Ocean are stable at present except for some reactivated old bedforms. Most of the bedforms, however, are active at present in this region.The velocity (0.3~1.0 m/s), direction and pathway of the cold bottom current can be deduced based on both hydrographic observations and sedimentary bedforms. The cold NSDW bottom water with a thickness of 100~200 m flows from (61° N,50° W) towards south, and then turns to west, passes through the third gateway (Iceland Basin), and then gradually mixes with the Northeast Atlantic Water. The total distance is about 850 km, and the width is about 10~30 km or more.