Beaufort Gyre IOEB Refurbished in 1997
Remarkably, the entire ice camp operation was performed in only 12 days, including all flights, pioneering and breaking down the ice camp. Due to the professional planning, experience and hardwork of the participants, and good fortune, it is inconceivable that the operation could have been performed more efficiently, or in any less time. The operation could have been extended by poor weather, poor ice conditions for landing (thus requiring the additional time and expense of ferrying by helicopter), or numerous other difficulties associated with the recovery, refit, and redeployment of the IOEB. In fact, between the time of the IOEB recovery and redeployment, the ice camp was separated from the Twin Otter by a wide lead. However, the lead closed when it was time for our return flights, thus alleviating the need to construct an emergency landing strip.
Since redeployment, all instruments (except the S4 module) have been functioning properly and broadcasting reliably. While the transmitters are provided with 3+ year battery packs, most instruments have only 2 year battery packs. The ADCP and S4 will fill their memory in only 1 year. Consequently, we can expect the IOEB to continue to transmit data for several years, but would recommend that the system be refurbished on a 1 to 2 year basis.
Recovery of Beaufort Gyre IOEB in 1997Scientists from the Japan Marine Science and Technology Center (JAMSTEC) and Woods Hole Oceanographic Institution (WHOI) participated in the operation. From JAMSTEC were Kiyoshi Hatakeyama and Toru Nakamura; from WHOI were John Kemp, Lawrence Costello and Richard Krishfield. Polar Associates provided one field person on the ice (Jeff Lord), and one based in Mould Bay (Ted Gooch). Transportation to and from the ice was by Twin Otter from Kenn Borek Air, piloted by Monty Stevenson and engineered by Dave Bosma.
The science equipment, camp gear, and fuel required for the operation was transported to Mould Bay in March on several C-130 flights by the 109th ANG from Thule AFB in Greenland. On March 30 and 31, all the field personnel travelled together on commercial airlines from Boston, Massachusetts via Ottawa, Ontario to Resolute, Northwest Territories, to meet the Borek Twin Otter. On April 1, the Twin Otter and all personnel arrived in Mould Bay, and an immediate reconaissance was performed over the IOEB site, approximately 350 km west of Mould Bay. The weather was clear and the buoy apex was easily spotted within a few minutes, approximately 25 m from a large ridge which apparently was formed from the refrozen lead which we used as our runway last year. The IOEB was upright, had a light covering of snow, but the meteorological mast and ice strings were intact and without damage. Although a landing did not take place, the pilot was confident that he could land on same floe with the buoy. Consequently, a helicopter was not required, and a corresponding amount of time and work was saved.
On April 2, the first landing on the icefloe occurred, and a load of camp gear deposited. During the next three days, all the remaining gear and all the personnel were installed at the buoy site, employing a total of 8 Twin Otter flights. The camp consisted of three tents, each providing workspace and housing two individuals. The recovery site and apparatus were prepared on April 5 and 6, and an ice core was taken in the icefloe near the IOEB. On the morning of April 7, the retrieval began.
The weather on this day was excellent for the recovery. The skies were clear, there was little wind, and the temperature hovered around -25 øC. The hot water ice drill was started and began cutting a 50 inch hole around the apex at 9:30 AM local (15:30 Z). In less than two hours, the drill penetrated the 14 10” of ice. The ice around the apex and cable was removed by pickaxe and chainsaw. This required the most time and labor of the recovery operation, and the hole was not completely clear of ice until 21:45 Z. Over the next 2.5 hours, each instrument on the mooring system was removed (while being kept warm by a hot air blower), and placed into the science tent. Although it was impossible to keep the sample cups on the sediment trap from freezing during the recovery, fortunately none cracked and no samples were lost. Later, after allowing the system to warm and dry somewhat, the bottles were removed, sealed and stored in a cool environment. All other instruments were allowed to warm and dry overnight in the science tent, and their data dumped the following day.
Full datasets were obtained from each of the three SeaCats on the mooring system, the upper S4 current meter, the transmissometer/fluorometer module, and the sediment trap. Only the deep S4 current meter failed to respond, even when a substitute battery packed was used. Preliminary analysis of the data indicates that the transmitted data compares precisely to the recovered data for each of these instruments, although the recovered data includes points not transmitted, as expected.
Over the next two days, a redeployment site was prepared, the apex refurbished and all instruments initialized for the reinstallation. Meanwhile, a CTD cast was taken down to 500 m through the hole abandoned by the IOEB. The redeployment site was removed about 50 m away from the recovery site, to provide more space away from the icefloe edge. The icefloe thickness was 13 7" here, and another ice core was taken at this site. On April 9, a new 39" deployment hole was cut through the icefloe, and another CTD cast was performed. During this second cast, bottle water for the sediment trap was taken at 100 m.
Redeployment of Beaufort Gyre IOEB in 1997
The final CTD cast was performed on April 11, while packing the IOEB refurbishment and deployment gear. The next day, three Twin Otter flights brought back most of the gear, and two scientists. On April 13, the weather worsened, and all the remaining camp personnel returned with the last full flight of equipment. In retrospect, we are fortunate to have returned when we did, for the weather would not have allowed flights to the ice for a number of days later.
IOEB Deployed from SHEBA in 1997As part of the Surface Heat Budget of the Arctic Ocean (SHEBA) buoy array, a Japan Marine Science and Technology Center (JAMSTEC) IOEB was deployed from the Des Groseilliers on the way to installing the main ice camp. Initially located about 50 km from the array, the buoy drifted in the same general manner as the main camp, and was recovered from the Louis St. Laurent during breakout of the SHEBA camp the following year. In 365 days, the system drifted a total of 2000 km from the Canada Basin, over the Northwest Ridge and Chukchi Plateau, to the slope of the Makarov Basin. Complete year-long timeseries of air temperature, barometer, buoy drift, and compass heading, were telemetered via Argos during the drift. Partial-year records of wind (< 1/2 year) and ice thermistor profiles (~ 3/4 year) were also acquired. Upon recovery of the buoy, upper ocean temperature and salinity data at 65, 105, and 165 m were retrieved along with current profiles from an ADCP, a timeseries of dissolved oxygen, and biogeochemical samples from a sediment trap.
Scientists from both JAMSTEC and the Woods Hole Oceanographic Institution participated in the field operations. On September 30, 1997 enroute to the desired SHEBA camp site, the Des Groseilliers manuevered into a position where the deployment could be performed with the bow crane. Equipment was loaded onto the icefloe, and a 1 m diameter hole cut through the 1.1 m thick icefloe. Anchor first, each instrument was attached to the mooring system and lowered through the icehole. By 23:50 Z, the mooring and surface apex were installed at 75 deg 5.4' N, 140 deg 54.7' W. The meteorological mast and ice thermistors were subsequently installed, the deployment gear loaded back onto the ship, and the cruise resumed. Later, after a problem with the underwater telemetry of the IOEB was identified, the buoy was visited briefly by helicopter, to make a correction which enabled the air and ice data to be transmitted. The ocean data had to be retrieved upon recovery.
Recovery of IOEB Deployed from SHEBA in 1997Over the next year, the IOEB drifted unattended in a large anticyclonic arc, while constantly updating locations via Argos. In May of 1998, scientists performing maintenance on a nearby buoy did visit the IOEB and surmised that a bear had visited the IOEB, removed the anemometer, and bent the air temperature radiation shield. Actually, the telemetered wind data failed on April 25th (while the IOEB was near 76 N, 164 W), so we believe that was when the bear discovered the buoy. The air temperature measurement does not appear to have been effected.
Recovery of the IOEB was accomplished on October 1, 1998 from the Louis St. Laurent. When found, the surface buoy was tilted at a 30 deg angle within a pressure ridge that appears from tilt data to have surrounded it two weeks previously. The meterorological mast was bent over and the wind monitor was missing, but the apex was undamaged. One out of three ice thermistor strings was still attached to the endcap. These were removed and brought onboard the ship, and ship's bubblers were used in an attempt to blow the mooring free from the broken ice. Due to the high ice concentration, however, the ice could not be removed. Consequently, the icebreaker was maneuvered for several hours to create a large pond. It then became relatively straightforward to pull the mooring system from the water in only a few hours (despite the raw weather), apex first. By 17:12 Z, at 80 deg 39.2' N, 160 deg 10.2' W, the system was completely recovered. Onboard, 24 Mbytes of data from the 150 kHz ADCP was dumped, SeaCat conductivities and temperature timeseries at 3 depths (one with dissolved oxygen) were retrieved, and a complete collection of 21 sediment trap samples were brought back to the lab for further analysis. Unfortunately, the SeaCat at 8 m was found to have failed, and the sensitivity of the fluorometer was too low to provide useful information.
We would like to extend our appreciation to the SHEBA program, chief scientists, and the officers and crew of the Des Grosilliers and Louis St. Laurent, for supporting the IOEB field program.