NBP09-01 Cruise Report - British Oceanographic Data Centre

at the helm.The high iceberg production and retention rates in the eastern Amundsen restricts the use of this type ofmooring to the study of deep water variability, since much of the meltwater produced by the ice shelvesand icebergs appears to be in the upper 400m. Most instruments were located high on the moorings in anattempt to capture changes in the lower pycnocline and deep water volume on the shelf. To monitor changein the upper water column requires a different approach, and led this year to the deployment of an ’IceTethered Profiler’ of the type recently used with considerable success by Toole, Timmermans and Krishfieldin the Arctic. Indeed, the ITP we used is the one they first deployed in the Arctic and was refurbished bythat WHOI group for this project.While Arctic ITPs drift with the pack there and are rarely recovered, a drifting ITP on the Amundsencontinental shelf is likely to ground on one of its many shoals. We thus sought fast ice that seemed likely tostay fast for at least a year, in the greater Pine Island Bay region where both the deep water and shallowerlayers could be monitored over time. Options were limited during 0901, the overall ice cover being on thelight side. The location we settled on (Table 6) was about 6 km south of a fast ice edge that extendedeast from Bear Peninsula (Island). An ice edge has been encountered in that location twice previously, butit was much farther south in 2006 and 2007. Both the ice and snow cover at the ITP site were less thananticipated, but we delayed deployment to as late in the cruise as possible, and were beginning to see newice formation a few days later. The work went smoothly, in good weather and less time than planned, withthe instrument set to profile daily over the upper 750 m of a water column >1300 m-deep (Fig. 23). TheITP did not initially ’call home’ as soon as expected, occasioning a return trip to the site, but by the time itwas reached good-quality profiles were being received at the WHOI end of its Iridium link. Some mid-profiledegradation in salinity has since occurred, perhaps due to biofouling of the pump (M-L Timmermans, pc).The third mooring type consisted of a McLane Moored Profiler (MMP) and ASL Ice Profiler (AIP) anchoredin 4600 m well northwest of the Amundsen continental shelf (66 27 S, 129 28.2 W) for project O-261.Although the weather was deteriorating at the time of deployment, the work went well on an anchor-lastoperation. Unfortunately, the top buoy, meant to end up at 75 m, appeared at the surface during a subsequenttriangulation run. This necessitated recovery, since its AIP would not function there and its buoy wouldlikely work the wire and profiler to excess and then be enveloped in the sea ice. Release and recovery weresuccessful, but its line came up tangled and apparently stretched (the latter perhaps the underlying problem),and the lack of spare line precluded redeployment.Mooring # Latitude S Longitude W Depth (m) Date y/m/d CTD #BSR 1 71 10.539 102 24.498 1094 9/1/13 5BSR 2 71 43.351 103 03.147 744 9/1/14 7BSR 3 73 26.767 106 44.561 902 9/1/16 11BSR 4 74 21.637 104 53.346 1259 9/1/16 13BSR 5 75 03.356 101 59.024 800 9/1/22 47BSR 6 74 54.861 101 52.695 950 9/1/22 48BSR 7 73 09.657 114 59.187 750 9/2/03 113BSR 8 73 57.744 118 01.087 1242 9/2/03 117BSR 9 74 11.060 112 31.014 1048 9/2/05 125BSR 10 71 02.159 105 59.948 1047 9/2/10 134BSR 11 71 07.847 106 00.114 520 9/2/10 135BSR 12 71 34.565 113 02.508 611 9/2/12 142BSR 13 71 23.276 113 23.961 1073 9/2/12 144BSR 14 71 57.537 118 27.781 602 9/2/15 157ITP 1 74 21.265 109 58.285 1340 9/2/05 126BML 5 71 08.21 105 39.97 540 6/3/18 302-1Table 6: Coordinates, water depths, dates and accompanying CTD stations for most of the moorings shownin Fig. 22.NBP09-01 Cruise Report (p. 31 of 83) Revised February 27, 2009