Expedition August 17 to August 25, 2007 by Humfrey Melling Previous | Next Second Report on Progress CCGS Henry Larsen returned to Kennedy Channel late on Friday August 17. During the night we worked three quarters of the primary CTD section across the strait, until stopped by heavy ice on the Ellesmere side. During Saturday, we tried to recover moorings at three sites under about five tenths ice cover on the Greenland side; sites further west were inaccessible in heavy pack. We were successful at two of these; a string of CT recorders and an ice-profiling sonar were brought to the surface, with complete 12-month within all instruments. The CT mooring at KS09 did not respond to interrogation; we have subsequently concluded on the basis of repeated attempts that this mooring has been lost to ice. From site KS09 we also tried to communicate with transponders on two moorings that were deemed lost in 2006 (KS11, KS15). A response from the transponder on the KS15 mooring indicated that our modified Benthos 867A transponding release did in fact have the four-year endurance that we had planned. Unfortunately, the range revealed that this mooring had moved 7½ km from its deployment location. In parallel activity, the NRC team was deployed via helicopter to survey a multi-year ice floe near Franklin Island, their fourth of this expedition. Our ship followed the Greenland side northeastward towards Hall Basin during the evening. We completed a CTD section across the northern end of Kennedy Channel during the night and arrived at Offley Island on Petermann Fjord after breakfast on Sunday August 19. Our efforts to communicate with the transponder on a shallow mooring in the shelter of this island were unsuccessful, both from the ship 2.2 km distant and from the FRC at progressively shorter ranges. While working from the FRC, the Benthos transponding unit suddenly failed. Following subsequent unsuccessful attempts to snag the mooring via grappling line, we have concluded that this mooring also has succumbed to ice scouring sometime since its deployment four years ago. After the NRC ice-survey group was deployed in Polaris Bay (multi-year floe #5), we took the helicopter first to St Patrick Bay, to retrieve oceanographic flotsam reported by Parks Canada and next to Discovery Harbour, to investigate a pressure recorder positioned there in 2003. The transponder in Discovery Harbour was operational but the pop-up float did not surface when the release was activated. We surmise that bio-fouling during the intervening four years prevented unreeling of the recover line attached to the float. Unfortunately we were not able to deploy the FRC with grappling gear because access to the bay was blocked by ice. This mooring is well sheltered and will presumably remain in place for possible future recovery. During the evening, we completed a CTD section along the glacial ice front of Petermann Fjord, seeking evidence of glacial-marine interaction beneath the floating ice tongue that extends out 100 km from the grounding line. CCGS Henry Larsen returned to southern Kennedy Channel overnight. On Monday August 20 we were back looking for opportunities to recover moorings along the KS line. We were successful in retrieving a string of CT recorders at KS07, but further west at KS20 (ice-profiling sonar) we were again thwarted by ice. Repeated attempts to communicate with paired transponders on three ADCP moorings (KS04, KS06, KS08) were made from both sites; moorings at KS04, KS06 and KS08 were in place in August 2006 but did not surface when the releases were activated. Obviously separation of the buoyant and heavy parts of these moorings had not occurred. We had thought in 2006 that the obstruction of moving parts was likely weak and that disturbance by grappling gear would have shaken the instruments free. Unfortunately, dragging was not practical in 2006 because of ice obstruction and limited ship time. The obstructions must later have weakened to permit the moorings to drift away. They are now considered lost. Today the NRC group surveyed a sixth floe (roughly an 8-hour activity for four people - two NRC and two crew) and placed a satellite-tracked beacon upon it. We spent the evening finding the lost mooring from KS15 via triangulation using the acoustic transponder. It was tracked to a location south of the original and south of Cape Jefferson in about 77 m of water. A small iceberg was grounded close by as if to illustrate the cause of the displacement. On August 21 we started again at KS20, selecting an ice-free pond in the pack and waiting to drift over the mooring for its release. Unfortunately the anticipated opportunity was lost with a change in the direction of drift. We then re-crossed the strait to bergy waters on the Greenland. Unsuccessful efforts to drag up the errant mooring from KS15 occupied the remainder of the day. A seabed littered with rock debris prevented tightening a loop around the moorings and repeatedly bent back the prongs on the grapples. Overnight, we completed a 12-hour CTD time series at KS09, seeking evidence of internal tides. On Wednesday August 22 we were prepared to start deploying new moorings along the KS-line as well as to recover some of the elusive originals. The KS line is the 'picket fence' of moored instruments stretching from Ellesmere Island to Greenland that we need in order to measure volumes and properties of seawater passing down the strait. Again we spent more than four hours drifting in a patch of ice-free water towards KS20, only to be thwarted by erratic drift. We were successful, however, in using the same technique to reach the planned deployment sites and to drop Long Ranger ADCPs within pack ice at KS10 and KS12 on the Greenland side. However, the attempt at KS-08 failed because of 'uncooperative' ice. The NRC group today surveyed their seventh floe. With time running short, we focused Thursday (August 23)'s activity upon the deployment of new moorings. Again with appreciable interference from drifting ice, a Long Ranger ADCP was deployed at KS-08 and strings of CT recorders at KS07 and KS09. Attempts to deploy at KS06 and KS11 were prevented by heavy ice. The new mooring at KS09 surprised everyone by re-surfacing shortly after deployment; for reasons not clear the long Kevlar line above the release float had parted during freefall of the anchor from the surface. After the release had been activated and recovered, the mooring was rebuilt and deployed for a second time without mishap. August 24 was a bleak day with moderate wind, our first 'weather' after days of idyllic clear calm and sunny conditions. The focus of work was again mooring deployment, with successful installations of a string of CT recorders at KS11 and of ice-profiling sonar at KS30. Subsequent initiatives were blocked by heavy ice. However, the same ice provided joy for the NRC group, which completed its eighth ice-floe survey today. With time running out, the possibility of installing an array that spanned the strait was fading. Our frail hope was the forecast of south-west gales overnight, which gave some reason to expect more navigable ice conditions on the Ellesmere side tomorrow. On Saturday morning, our optimism concerning improved ice conditions was rewarded. Under influence of a 30-knot south-west wind, the pack had diverged to permit a relatively unchallenged transit towards Ellesmere Island. We quickly deployed Long Ranger ADCPs at KS-06 and KS-04. Retrieval of the ice-profiling sonar at KS20 was again prevented by ice, as was access to KS03 to deploy a CT string. However, after patient waiting (6 hours) for a tide change and southerly ice drift we did deploy the CT string early in the evening at KS05. After the NRC group returned from their ninth ice-floe survey - a floe of 5-10 m thickness - we turned south. During the overnight transit to Smith Sound, we measured a longitudinal section by CTD of waters in the deep channel along the western side of Kane Basin. Under the circumstances, I am content with the slightly skimpy array that we have established for the IPY. The failure to recover the ice-profiling sonar at KS-20 has little consequence, since it has batteries to operate for another two years. We will now turn our attention to the second location for Canadian Arctic through-flow, Cardigan Strait and Hell Gate at the southwest corner of Ellesmere Island. Instruments were placed in the remaining two pathways during other IPY expeditions earlier this summer, in Barrow Strait from CCGS des Groseilliers in early August and in Bellot Strait in late July.