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Immediate report of Victoria University of Wellington Antarctic Expedition 1989-90: VUWAE 34

ANTARCTIC BOTTOM CURRENTS (K042)

page 33

ANTARCTIC BOTTOM CURRENTS (K042)

Aims

The purpose of this project was to determine the nature (speed/direction/persistence) of mud-carrying bottom currents in Granite Harbour. Such currents have been suggested to explain deposits of mud flooring the deeper parts of McMurdo Sound and the basins/harbours along the southern Victoria Land Coast (Barrett et al. 1983, Kelly 1986, Macpherson 1987). There is no single obvious source or depositional process for the mud deposits although Anderson et al. (1984) suggested impinging geostrophic currents and subglacial meltwater as potential sources.

This season's programme (1989-90) was to study the movement of sediment entering Granite Harbour from the Ross Sea by mooring the current meter and sediment traps on the sill between the two main basins of the Harbour. The mooring was to be in place for about 2 months (November - January). We also planned to service the tide gauge at Cape Roberts established in November 1968, and if possible add meteorological instruments to record local climate data for future programmes. Inspection of the tide gauge in January 1989 raised doubts about the permanence of the transducer installation which may not survive ice foot breakout.

A further part of this season's work was related to a future proposal aimed at studying the Holocene Marine Glacial History in this area of the Ross Sea. We intended to carry out a reconnaissance survey of both coastal features in Granite Harbour and nunataks on the south side of the MacKay Glacier to find evidence of Holocene glacier expansion both at sea level and well above the present day MacKay Glacier Tongue grounding line.

Planning

The planning phase for this event could not be finalised until mid year when Antarctic Division's vehicle scheduling was decided. It is understandable that some events planning takes longer than others and we appreciate Antarctic Divisions efforts on our behalf. A fuel and cargo cache was to be transported to Cape Roberts for this event. Unfortunately only fuel was cached because of cargo delays to Scott Base but the fuel cache still proved very worthwhile.

The training course briefings are an important part of the event planning. For some events, where planning decisions may have just been made prior to Tekapo or may still need to be made then some discussion and possibly changes should be expected at the briefing session. This may be the first time an event can discuss their programme face to face with the assembled Antarctic Division personnel.

Cargo

Wellington to Christchurch / Scott Base
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Scott Base / Christchurch - Wellington

Preparations for the Field

The arrival briefing at Scott Base is a very important part of the initial preparation to establish a good working relationship for the progression of a successful field season. This season I was dissapointed that the briefing could not be carried out within a few hours of our arrival at Scott Base consequently it was difficult to plan our work programme until much later the following day after the briefing. Some of the points raised at the briefing seemed to be unnecessary and poorly communicated, especially for an event containing several people with previous antarctic experience including a surveyor and a permanent member of Antarctic Division Staff. I also found if difficult to discuss in detail our survival training requirements without the presence of the survival school instructor at the briefing. This later led to a misunderstanding regarding the purpose of our sea ice part of the training. I am very keen to pass on my sea ice experience to the survival school and would like to do so in the future, but would be concerned if this is taken for granted and occurs at the expense of the science event.

All the field equipment was in excellent condition and much of it already allocated to our event thanks to the Scott Base stores staff and system.

The glacier travel part of the survival training was enjoyable and appreciated by those who participated (Goodwin, Rodgers and Möller). The second part of the course we had hoped to do was a shakedown exercise using the Hagglund and winch. Unfortunately this was cancelled due to bad weather and was modified to a sea ice course primarily for the survival school instructors later in the week. This was at the insistence of the Operations Managers even though it was clear that our science programme would then be delayed because of forecasted bad weather.

We were delayed at Scott base two days due to bad weather after completing the sea ice course requirements. In total we spent 7 full days at Scott Base before leaving for the field which is an unusually long period of time considering that a lot of the vehicle and field equipment preparations had been done prior to our arrival by Scott Base Staff.

The NZARP Survival School provides an excellent service but it still seems to be locked into regular two day courses. I would like to see more flexibility both in the scheduling of courses so that field groups can be accommodated quickly after arrival at Scott Base and in the content and duration of courses to better accommodate many NZARP field personnel who have previous Antarctic experience.

The position of Operations Manager at Scott Base is a crucial one for the field science programme. I think the position would be best filled by personnel with previous NZARP Antarctic experience. This is particularly important so that the field season can start quickly and local knowledge would help in seasons like the past one when the weather was unsettled especially in November. Personnel with previous experience also have first hand experience of the NZARP field programmes and would know many of the science people returning in successive seasons.

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Field Transport

NZARP Vehicles
Hagglunds BV206 #H26

This vehicle is in a standard configuration with "trailer caboose" and is powered with a Ford petrol engine. The machine was allocated to K042 for our sea ice operation and glacier travel. A Maudheim sledge was lowed with up to 1800kg of cargo without difficulty up to Cape Roberts, partly unloaded then used within Granite Harbour. H26 generally performed very well without any significant mechanical problems. Ice studs had been fitted to the tracks prior to leaving Scott Base and these certainly improved vehicle traction on polished sea ice and on the 25 - 30° ice slope terminus of New Glacier.

Table 1. Vehicle diary Hagglunds BV206 #H26

It is not possible to accurately measure fuel usage in the field because we did not have a metering fuel pump and the vehicle tank gauges are not accurate. We used approximately 875 of Mogas and travelled 855 km giving an average fuel consumption of 1 litre/km which includes consumption while idling. A consumption rate of 1.25 litre/km should be a suitable figure to use for planning purposes.

This vehicle proved very suitable for general sea ice based work because it was reliable, comfortable, maneuverable and well controlled when crossing sea ice cracks. I would suggest however that some consideration be given to providing a choice of interchangeable modules for the rear caboose. For our sea ice operation a truck type flat deck with skies would be better to transport and operate some of our heavier equipment.

Our experience in extracting H26 from a crevasse has also indicated that rescue equipment should be carried and possibly some operating procedures reviewed. The electric winch on H26 was of little use when the vehicle is stuck and cant turn to level-wind. Consequently the wire cut itself during our first attempt to recover the vehicle. Chain hoists, TIRFOR hoists and a timber jack worked well during the vehicle recovery. It also became obvious that a Hagglunds te very vulnerable in a crevasse rescue situation if the hydraulic rams linking the front cab to the trailer are damaged either when falling into the crevasse or during the recovery operation. It is important therefore to move or lift the vehicle carefully so that the two parts of the vehicle remain in the correct relationship with each other. Any attempt to pull a Hagglunds out with another vehicle (such as a bulldozer) should therefore be considered very carefully to avoid over stressing the linkage system. Some consideration should also be given to page 36 rescuing the vehicle if it falls well below the crevasse lip. In this case some sort of lifting structure (e.g. like a davit) would need to be erected at the edge of the crevasse so that the vehicle could be lifted before being pulled out. Such a structure could be in a "bolt together" form that could be "footed" into the crevasse edge in a similar way to timber dead men. In our experience the survival box carried on the roof of the rear cab also caused difficulties because it was extra weight that was not required because we had our own camp equipment and also made the rear cab top heavy. Our camp equipment was carried in the rear cab which required careful unloading once in the crevasse. We may have been better off spreading our load onto a lowed sledge in this situation. It is also difficult to decide the best preparation for personnel travelling in the driving cab when travelling in areas of potential crevasses. The best compromise in this situation is to have all personnel wearing harnesses and have ropes available both inside and outside the cab to tie into.

Suggested list of extraction equipment, most field operations:
  • 2 × chain hoists (to lift vehicle)
  • 2 × TIRFOR hoists with wire cable
  • 4 deadmen (200 mm × 200 m × 1 m timbers)
  • Chainsaw (to place deadmen)
  • Chain slings
  • vehicle jacks (normally carried in vehicle tool box)
  • Deep field operations (in addition to the above)
  • Lifting frame (timber or steel pipe?) assembled at site to lift vehicle out of crevasse.

In a deep field situation it would be likely that at least two vehicles of similar capacities would be operating. Our crevasse experience does however highlight the problems of a single vehicle operation even though we were well served by helo from Scott Base.

Maudheim Sledge

This sledge was purchased with H26 and is larger than previous maulheim sledges used by NZARP. It is a good size and robust for our operation and has polyethylene shoed skies which makes towing easy although the sledge should only be used on snow or ice. We did note however that a lot of the timber sledge components where laminated and were delaminating in places. The sledge could also have rings fitted to make attaching cargo straps easier.

Helicopter Operations

The RNZAF Iroquois was used during H26 crevasse recovery to bring personnel from Scott Base and bridging timbers from Cape Roberts to the crevasse site. The crew's willingness to standby while the recovery was in progress was most appreciated but the weather conditions were deteriorating and I asked them to return to Marble Point and eventually McMurdo Station.

A Helo operation was scheduled to recover the mooring in Granite Harbour on 5 January. Equipment was underslung from Cape Roberts to the mooring site and later slung back to Scott Base. The operation went well but unfortunately the helo ran out of crew time because they took longer than expected to move the NZARP group in the Convoy Range so we couldn't do the planned aerial photography at Cuff Cape. Pat Sole (K191) however completed this photography later in January. It was also unfortunate that we couldn't programme to stay overnight at Cape Roberts to complete the met. instrument checking because of a high helo use the following day. In general the operation went well and we are grateful to the Scott Base Operations Manager for his programming.

Event Diary
3 Nov Chch - McMurdo flight delayed. Received K042 event Directive in Chch after request to Ant. Div.
4 Nov To Scott Base. Pyne, Goodwin, Möller.page 37
5 Nov Prepared field camp equipment.
6 Nov Sea ice / Hagglund shakedown cancelled due to bad weather.
7 Nov Storm all day - preparations at Scott Base.
8 Nov Goodwin, Möller, Rodgers on glacier travel survival course.
9 Nov Sea ice course to Turtle Rock. K042 and K191 personnel plus G. Kennedy (survival school instructor), and A. Belcher (Radio Operator). Weather deteriorated in the evening - cancelled move to Butter Point.
10 Nov Poor weather - moved sledge 12 km from McMurdo, returned to Scott Base.
11 Nov Storm @ Scott Base - no movement.
12 Nov Left SB for Cape Roberts. Straight line route McMurdo to Marble Point on good first year ice. Refuel @ south side Marble Point 1987 MOGAS. Good travel onwards to Cape Roberts - Total trip time 11 hours. Checked tide gauge and found pressure transducer missing.
13 Nov Prepared mooring equipment, down loaded tide gauge data-lost transducer readings 6 February 1989.
14 Nov Bathymetry in Avalanche Bay for mooring site. Checked terminus of New Glacier for suitable Hagglund (H26) route. All first year ice enroute to New Glacier except 2 km off New Glacier.
15 Nov Helo aerial photography with K191; C.Roberts, ML England, ML Marshall and north peak of Mt Suess where mast/caim were established. K042 return to C.Roberts. K191 to Vanda.
16 Nov Set mooring with current meter and 7 small sediment traps in "Avalanche Bay channel site".
17 Nov Began establishing 4 m met. mast addition to the tide gauge recording equipment at C.Roberts.
18 Nov Completed met. mast installation. Poor weather in early evening.
19 Nov Tested vibro-corer pressure housings to 850 m depth at S-216 site in outer Granite Harbour. Travelled to New Glacier and upwards heading for the Flatiron. H26 fell in crevasse above the crevasse field on the top north side of New Glacier. Extension of the crevasse field not evident on aerial photographs and obscured by 1 m thick snow and wind slab. See accidents section for further details.
20 Nov Recovery of H26 with assistance from Scott Base personnel and Kiwi helo.
21 Nov Scott Base personnel return to SB. Return via New Glacier to Granite Harbour. Recon. of New Glacier moraine below Mt. England, Devils punch bowl, Finger Point and Cuff Cape. Camped with S-216 at NE snout of MacKay Glacier Tongue (MGT)
22 Nov D. Hotop and P. Sole to K042 from Scott Base. Goodwin and Rodgers return to Scott Base. Goodwin return to New Zealand. Recon. of north armpit of MGT and Point Retreat and return to Cape Roberts.
23 Nov Work at Cuff Cape and bathymetry completed at Avalanche Bay. Return to Cape Roberts in evening.
24 Nov Work at Cuff Cape and recover/redeploy the mooring. Weather deteriorated in late afternoon.page 38
25 Nov Work at Cuff Cape survey moraine ridge system related to small hanging glacier.
26 Nov Prepared mooring equipment for January recovery. Packed equipment for return by sledge to Scott Base. Checked met. mast operation and down loaded data.
27 Nov To the Flatiron. Recon. of ponds on the Flatiron and beach ridges at C.Geology and Botany Bay.
28 Nov Left C. Roberts and return to Scott Base. Picked up 44 gal. MOGAS at Butter Pt., tide crack too wide to cross, returned fuel to Scott Base.
29 Nov Equipment return and cleanup. Packed cargo for return to New Zealand.
30 Nov Möller to lower Taylor Valley with K042. Pyne-Boomerang flight, McMurdo-McMurdo.
1 Dec Pyne return Chch.
4 Dec Möller to Scott Base from Taylor Valley.
5/6 Dec 1990 Möller return to New Zealand.
4 Jan Pyne to Scott Base.
5 Jan Pyne, Hotop, Kernot to Granite Harbour. Pick up equipment at C. Roberts. Recover mooring after initial recovery problem. Return to C. Roberts, download current meter data and attempted maintenance of met. mast. Computer problem - left met. mast non operational through winter 1990. Could not do Cuff Cape Aerial photography because of helo crew time overrun.
6 Jan Packed equipment for return to New Zealand. Checked WINKIE drill bits at Scott Base. Pyne transferred to McMurdo to join S-216 for preparation on Ross Sea 90 Cruise.
7-10 Jan Preparation of equipment at McMurdo with S-216. Transferred to USCGC Polar Star in early evening at McMurdo for rendezvous with MV Polar Duke on 11 Jan.
11 Jan-9 Feb Ross Sea 90.
9 Feb-14 Feb Return equipment etc for winter storage at McMurdo.
14 Feb Pyne return to Chch.

Accidents

Hagglunds (H26) recovery from crevasse

H26 became stuck in a crevasse after driving up New Glacier on route to the Flatiron. The crevasse was encountered on a gentle snow covered slope (<10°) above the crevassed area at the top of New Glacier which is obvious on aerial photographs and the 1.250,000 map series. An account of the incident is detailed below.

19 November, 2130 NZST. Began ascent of New Glacier after refuelling and leaving sledge on sea ice at New Glacier Terminus. Travelled up glacier and crossed several small crevasses (up to 1.0 m wide) in blue ice.

2230 NZST. Reached upper New Glacier approx 6-8 km from terminus then turned north to north east towards the Flatiron. Gentle snow slope, travelled at about 10 km/hour (tow ratio, 2 gear)

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2330 NZST. Encountered crevasse parallel to our tracks. Rear cab tilted at 45° resting on crevasse edge hallway up the caboose side, right track and part of the left track in crevasse. No personnel injuries sustained and evacuated uphill and through left side doors without difficulty. Front cab tilted between 10-20° with tracks partially on snow bridge. Goodwin roped up and unloaded survival box and rear cab. Immediate area probed for crevasses and crevasses marked with bamboo canes. Set up timber deadman 15 m away at 10 O'clock to vehicle in small crevasse. Winched vehicle about 1 m forward before wire broke because vehicle couldn't move to level wind the wire.

20 November 0100 NZST. Carried camp about 100-150 m down track and established camp for the night. Informed Scott Base at 0145 NZST that H26 was immobilised in a crevasse and that we would require assistance from Scott Base for the recovery.

1400 NZST. Kiwi helo arrives at crevasse site with Scott Base mechanic, two survival school personnel and recovery equipment. Helo to C.Roberts and returns to site with two bridging timbers. Weather was closing in so helo returned to Marble Point. Crevasse area rechecked and flagged by survival personnel and established safe routes and personnel anchors. Vehicle initially righted with chain hoists, the back cab was slid sideways so that the left rack was on a firm footing. Timbers were slid under the rear cab right track, and the front cab jacked up, then the vehicle was pivoted about the hinge point by a combination of winching and steering and eventually driven off the crevasse. Vehicle recovery completed at 2045 NZST.

All personnel remained at the camp site that evening.

21 November. Kiwi helo returns Scott Base personnel and H26 returns down New Glacier without incident.

We have operated in this area by toboggan in previous years (1981,9182,1983) and a USARP group used toboggans this season to travel up New Glacier to Pegtop Mountain without incident. Hagglunds have a relatively low ground pressure but are still moderately heavy vehicles and it is the total weight which is the important consideration on wind slab snow and snow bridges.

Due to the crevasse incident we decided to cancel the planned work at Mt. Suess and Pegtop Mountain, however we are confident this work could be done with toboggan support in the future.

Radio Communications

K042 was issued with tacit VHF radios and a Compak HF radio. The HF was used during the crevasse rescue at New Glacier because the VHF repeaters at Mt Erebus or Mt Newall were obscured. HF communications varied at times due to atmospheric disturbance which made it difficult to initially inform Scott Base of the detailed situation.

VHF communication was used most of the time from Cape Roberts and on occasion from central Granite Harbour. For some reason communication also varied from day to day or hour to hour both on the Erebus and Mt Newall repeaters. On several occasions at Cape Roberts hut we could not transmit via Mt. Newall on a raised high gain antenna, even though this had given excellent results the previous season. The repeater on Mt. Erebus was also unpredictable and might need realigning or tuning to service Granite Harbour better. A temporary repeater on Mt. England or Mt Marston would service most of the Granite Harbour area.

Cape Roberts Huts

Two huts are now established at Cape Roberts, providing 4 bunks in the previous smaller hut and a kitchen / lab facility in the new hut. The facility is now vastly improved and provided on excellent base to work from in Granite Harbour. The huts required restoring later in the season because the initial piling and deadmen proved inadequate when the thaw began in late November. A new aerial at the hut also improved VHF communication with Scott Base.

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The cooking facilities could be improved by replacing the present old twin burner kerosene optimus with a clean burning LPG gas oven. Kerosene of doubtful quality presently stored at the hut could then be burned in the DFA heater. Extra seating and a more sturdy small table would also be required for a large field group.

Acknowledgements

Equipment was prepared with help from Eric Broughton (RSES, VUW), the members of the VUW mechanical workshop and Peter issacs (NX Met. Service). The S4 current meter was recalibrated (0-50 cm/s) by the Oceanographic Institute DSIR. We are grateful to the Antarctic Division and Scott Base staff who assisted us in the programme planning and in Antarctica Special thanks to our field assistant /Hagglund operators Ron Rodgers and Dave Hotop, and Mike Kernot (RNZAF - 3 Squadron) who helped with the January moving recovery. Thanks also to Rob Dunbar's S-216 group for assistance testing the vibrocorer housing and hospitality while in the field. Pat Sole (K-191) once again provided much appreciated survey assistance to our programme.