The field operation waa conducted during extremely adverse 

 weather conditions. Air temperatures dropped to as low as -k^°F, 

 and wind speeds averaged 15 knots. At times, zero visibility 

 ("whiteout") conditions prevented personnel movement over the ice. 

 Tvd.ce, the tracked vehicle started to break through the ice, but 

 was carried across the fract\ired area ("wet cracks") by the forward 

 fflomentvun of the vehicle. Needless to say, special precautions and 

 procedures were adhered to during the operation. The Air Force as- 

 signed a siiTvival expert. Sergeant JOHN KERSHNER to work with the 

 scientific party for the duration of the field operation. Sergeant 

 KERSHNER not only assured personnel safety but also contributed to 

 the success of the mission by suggesting arctic procedures and ac- 

 tively participating in the field work. 



Original plans specified 2k hours surface and bottom ciirrent 

 measurements at each of the seven sites shown in Figiire 2. In addi- 

 tion, a string of five current meters was to be installed at Site 1 

 at the beginning of the operation for continual data recording until 

 retrieval of the meters at the completion of the operation. Bottom 

 photographs also were to be taken at each of the sites upon comple- 

 tion of the cvirrent meastirements . The current meters and camera were 

 to be lowered and raised with a winch mounted in a specially construct- 

 ed mobile laboratory. 



Rapid deterioration of the ice in the vicinity of Sites k, 5, 6, 

 and 7 necessitated relocation of the originally selected sites. The 

 positions of the relocated sites are shown in Figure 2. Figure 5 

 shows the approximate ice limits observed by aerial reconnaissance on 

 7 April 1968. Dangerous ice conditions prevented moving the heavy mo- 

 bile laboratory to sites 5, ^, 5, 6, and 7. As a resiolt, operations 

 at these sites were limited to sxirface cxirrent measurements obtained 

 by lowering and raising the current meters by hand. Bottom photo- 

 graphs were obtained only at Sites 1 and 2. 



The mobile laboratory was designed by us at Thule using available 

 material. A large flat-bed truck was located in the surplus lot of 

 the motor pool, and its flat-bed section we-s used as a rolling plat- 

 form. V/e had brought along a gasoline powered winch and derrick for 

 use on the operation. The Air Force Base support group ;inder Lt. 

 Colonel T.W. Evans motinted the winch and derrick on the flat -bed sec- 

 tion and constructed an enclosing shed. Since this was an oceano- 

 graphic operation, we commissioned the mobile laboratory "the Research 

 Vessel THULE." 



The R/V thule is shown in Figiores 4A, kB, and kC. Figure k-A shows 

 the R/V thule being towed to its station by an Air Force trucked vehicle 

 (IRACKMASTER). The reason that we used a rolling bed rather than a 

 sledded bed was the towing capability of available tracked vehicles. 

 This arrangement was adequate for the type of ice cover present, which 

 was first-year plate ice with occasional embedded icebergs. Figiore hH 

 shows the R/V THULE on station. The winch mounted inside the shed is 



320 



