A dense bottom water plume in the western Barents Sea: downstream modification and interannual variability

The generation and downstream modification of a cold dense Arctic shelf wat er plume were studied with moored current meters, thermistor chains and con ductivity/temperature sensors deployed from August 1993 to September 1994 s outh of the Storfjord in the Svalbard Archipelago. These observations are c ompared to similar time series from 1991/92. In 1993/94, bottom water with temperatures close to the freezing point drained continuously from Storfjor d between March and September with a mean speed of 0.14 m s(-1). About 1.5 months after the plume front had left the Storfjord, it reached the shelf b reak, 150 km away. The plume had increased its width from 15 km to about 35 km, but its thickness of 50 m remained almost constant and it left the she lf edge at a similar speed. The increased volume transport and the change o f temperature/salinity properties indicate an entrainment of 110% of ambien t Atlantic water into the plume on its way from the production area to the shelf edge. The maximum salinity of the cold plume was 0.2 lower in 1993/94 than in 199 1/92, whilst the temperature/salinity-range of the surrounding Atlantic wat er remained unchanged. Probably as a dynamic consequence, the speed of the plume was considerably lower in 1993/94. The lower salinity of the plume in 1993/94 is a result of both the 30% less ice formation in Storfjord, cause d by lower heat flux and less open water, and a lower surface salinity at t he beginning of ice formation. During 1993/94, the Storfjord plume was too light to sink below 700 m. (C) 1999 Elsevier Science Ltd. All rights reserv ed.