Oceanography. The drifters consisted of an ARGOS transmitter inside a cylinder with system electronics, a 1 m long drogue centered 0.5 m below the surface, and a thermistor. Most drifters documented the initial freeze-up of the Mackenzie Shelf Sea, however, all but 2 drifters failed within 30 days of their deployment. Encroaching ice probably sheared off small balls providing buoyancy. More rugged drifters were deployed in 1995 into the Chukchi and East Siberian Shelf Seas. Some 40 inexpensive drifters with holey sock drogues were manufactured by Horizon Marine Inc. to specification. Each drifter consisted of a cylindrical body housing antenna, electronics, and batteries and a separate 2 m holey sock drogue centered 2 m below the surface about 3 m besides the surface cylinder. About half the drifters deployed in the fall of 1995 survived into the summer of 1996 tracking ice motions off Siberia during the winter of 1995/96.

　

4. MACKENZIE SHELF (1994)

　

As part of the Beaufort Arctic Storms Experiment (BASE) scientists monitored the property distribution of the ice, the atmosphere, and the ocean in the Canadian Western Arctic during the fall of 1994. Weather and ice conditions varied dramatically durin9 the week long cruise when 15 drifter were deployed from the CCGS Arctic Ivik during CTD/ADCP survey work. No ice and little wind was present during the first 4 days of the experiment while a moderate gale advected the ice edge as well as large amounts of scattered ice onto the shelf from offshore. Figure 2 shows the hydrography shortly after the deployment of the drifters. A strong upwelling front is visible. It separates a strongly stratified mid-shelf from a more weakly stratifiled inner shelf. The front separates salty waters inshore from buoyant Mackenzie plume waters offshore. Figure 3 indicates drifter

deployment locations and 5-day long trajectories. Drifters deployed on the inner shelf indicate a surface flow in the direction of the wind while those deployed offshore indicate a flow almost perpendicular to the wind direction. A balance between surface and bottom stresses would explain the inshore trajectories while further offshore the Coriolis force contributes significantly also (Csanady, 1978). Data from vessel-mounted acoustic Doppler current profilers and sealevel oscillations (not shown) indicate that large spatial and temporal gradients cause signifcant accelerations also.

5. EAST SIBERIAN SHELF (1995)

During the ice-free summer season of 1995 scientists aboard the R/V Alpha Helix deployed 39 surface drifter into the East Siberian and Chukchi seas in order to test the hypothesis that the discharge from the Kolyma River forces a buoyancy driven coastal current towards Alaska. Figures 4 and 5 show the trajectories and the derived mean flow field for the period from Aug. 24 through Oct. 17, 1995. They reveal a surface flow in the opposite direction. This flow is statistically significant at the 95% confidence level for both Eulerian and Lagrangian ensemble averages. Instead of a coastally trapped eastward flow I find a laterally sheared westward flow with maximum velocities offshore that correlate only weakly with the local winds (not shown). At a daily, probably wind dominated time scale the drifters reveal

BACK　　　CONTENTS　　　NEXT