K042 : Last Retreat of the Antarctic Ice Sheet in the Ross Region
Antarctica New Zealand November 1992 - December 1992. February 1993.
The project will determine the timing and rate of retreat of the edge of the Antarctic ice sheet across the Ross continental shelf since the last glacial maximum 20,000 years ago to resolve the present substantial differences of opinion. This will involve coring from fast sea ice off the Victoria Land coast in Granite Harbour and northwards, and from a ship in the central Ross Sea.
The cores will penetrate the recent layer of mud, deposited under sea ice/open water conditions like today's, and into diamictite beneath, deposited when the shelf was covered by the extended ice sheet. The corer has been designed to penetrate and recover up to 6 m of both soft mud and diamictite in water depths to 1000 m. The timing of glacial retreat is obtained from carbon dating contemporaneous shell material and organic carbon in organic rich sediment just above the diamictite. Thorium 230 dating by mass spectrometry on suitable carbonate materials may also be attempted.
The main objective of the 1992-93 sea ice based programme was to obtain cores from the sea floor in Granite Harbour. This part of the programme was not successful because of deployment and operational problems with our new coring equipment (vibracorer). The corer performed correctly in 700 m deep water but was unstable on the very soft sea floor and no useful core was recovered.
A ship based programme in February 1993 was very successful, with over 450 nautical miles of 3.5 kHz sea floor profiling data collected from the USCGC Polar Star off the South Victoria Land Coast (Figure 1). Data collected in Granite Harbour and off the Nordenskjold Ice Tongue will be used to map the extent and thickness of the Holocene mud blanket. The data collected offshore of Cape Roberts will be used to characterise the sea floor and compile a high resolution bathymetry map for future proposed drill sites in the area.
The planning of the sea ice part of the programme was relatively straight forward with no significant problems, although testing of the corer occurred later than planned. We also did not get a chance to test our winch with the NZAP Nodwell in New Zealand as it had been sent to Scott Base by ship the previous season. Shipping the event cargo went well due to NZAP efforts and good communication.
Planning the ship based programme to core from a USCGC Icebreaker was difficult because NSF,which controls the ship operations, appears not to have a well developed icebreaker programme prior to the start of the season and could only offer 1-2 days ship time during tanker refuelling.this was insufficient for our programme. Our enquiries via NZAP about the Icebreaker's coring and 3.5 kHz profiling equipment were not passed on to the ship. If our enquiries had been answered then we would have been better prepared to take full advantage of the USCGC Polar Star in February 1993 by digitally recording the 3.5 kHz profiling data.page 2
Figure 1. Ship track, 3.5 kHz profile lines from USCGC polar Star and sea ice coring site 92-1 in Granite Harbour
We hope that in the future better communications will be developed with NSF-OPP and NZAP to enable realistic planning of ship based programmes. It is still necessary where technical questions arise to be able to go directly to the ship or ship operators. The last lesson from this seasons experience is that a ship programme should be ready to go at short notice if an opportunity should arise later than the date when normal planning is finalised. It is a credit to the NZAP operation and flexibility that our February 93 Ice Breaker programme was supported with 3 days notice.page 3
Operating at the Nordenskjold Ice Tongue is still contemplated for the the future. A helo reconnaissance this season showed suitable fast ice was present along the coast to travel and operate around the ice tongue. We did not have time to travel by skidoo to the Nordenskjold for the bathymetry as planned this season. Based on this seasons reconnaissance it would probably take up to 4 days to travel by bulldozer from Scott Base to the Nordenskjold. This is clearly too long to then give sufficient working time in the area within our safe sea ice operating window. Operating at the Nordenskjold would however be practical if faster vehicles (Challenger and Nodwell) were used or if the vehicles were staged and returned to Cape Roberts in a future season. In this case the one way trip would be only 95 km and possible in 1 to 1.5 days travel.
The NZAP medicals changed significantly this season with a marked increase in the number of blood and other tests required, at a time when Government directed costs of these tests rose dramatically. We question whether these tests are necessary, especially when some of them are only voluntary in the USAP programme.
Unaccompanied to Scott Base: 10,447 lb (4750 kg); 527 ft3 (14.8 m3). In 9 boxes up to 6.1 m long, winch and rope drum.
Accompanied to Scott Base: 280 lb (127 kg). Delicate electronic equipment.
Cargo returned to New Zealand by air and the majority by sea, same as above.
|A.||Sea Ice Programme
|B.||Ice Breaker Programme
- Paul Chaplin (Operations Manager)
- Dave Comber (SENZREP)
- Brian Green (Electrician)
- Greg Harris (Mechanic)
- Mike Manon (Lab Technician)
- Dave Milne (Asst. Stores Officer)
Preparations for the Field
Management for this event was carried out efficiently and generally smoothly by Scott Base staff. One unexpected change to the Helo plan was the replacement of two of our party (scientist and plant operator) were replaced by 2 Scott Base staff (operations manager and FTC leader)for their familiarisation of the area. Most of our event people are new each season and this helo reconnaissance provides a quick and reliable means for them to become familiar with the sea ice route and area of operation which I consider is vital for event operation and safety. If this familiarisation is also considered necessary for Scott Base staff then the helo time should be programmed as part of base operation and not be taken from the event allocation.
Ten days were required to prepare the scientific, field equipment and cargo train. This was about 3 days longer than planned and was caused by a combination of factors including first time assembly of the vibracorer at Scott Base and setting up of the Nodwell ice drill and winch in Antarctica. In future seasons the preparation period will be shortened to increase time on the sea ice. We are modifying our equipment to make it easier and faster to assemble in Antarctica but we will still require some help from the mechanics, engineers and plant operators during this period. Work could be identified by us and NZAP (technical services) that could be done prior to the event personnel arriving on the ice.
Some Scott Base equipment required work before being serviceable for the journey to Granite Harbour. The D5 required a new alternator, a Cantago sledge required rewelding the drawbar and the Nodwell ice drill needed commissioning and modifications. The Nodwell HIAB crane pressure relief was also increased to the design specifications. The Nodwell tasks were anticipated and did not cause significant delay.
All vehicles were generally in good condition when allocated to the event and the only problems were minor, (see para. on the D5 and Cantago sledge above). The D5 towed 3 Cantago sledges (incl. NZ1) and a TAE sledge. Consumption of JP8 was 230 1/100 km. Detailed checks of these sledges is time consuming but should be done at the end of summer by an engineer so that repairs can be made during as part of the winter work programme.
The NZAP Nodwell performed well in the field especially considering the age and history of the chassis (1962). The new Isuzu engine started easily was fuel efficient and with about 3000lb on the deck and no towed load consumed JP8 at 125 1 per 100 km. The only major problem we encountered with this vehicle was the lack of spare tyre and wheel. USAP use special foam filled tyres for their Nodwell vehicles which eliminates the need to carry a spare. Perhaps NZAP should adopt this practice also.page 5
Two Alpine II skidoos (AL1, AL2) were used by the event. The machines performed very well for all the purposes we required and no breakages occurred. The use of a low sledge (TAE) for towing the skidoos when they are not in use with the slow moving cargo train is a useful option.
Some fuel (JP8 and MOGAS) was supplied from Scott Base but the majority of JP8 was supplied from USAP at Marble Pt. into 11 209 1 empty drums hauled from Scott Base. This reduced cargo loading to Marble Pt. by 5,000 lb (2270 kg) which is clearly advantageous. The disadvantage is that an extra day was required to traverse over rough ice into Marble Pt., onto land to the air facility to fill the drums. It would be a significant advantage if fuel was pre positioned on sea ice north of Gneiss Pt. to avoid the normal rough ice in Marble Pt. bay (Arnold Cove) and the land travel to the Helo fuelling facility.
Bridging equipment for heavy plant and sledges operating on the sea ice is still required in the NZAP programme. Bridging should be quick and easy to setup to provide safe operation and crossing of several vehicle and sledge types. A long low sledge with drop ramps towed behind heavy plant could be a relatively low cost option. Such bridging equipment will be required for the Cape Roberts programme.
The helicopter sea ice reconnaissance to the Nordenskjold Ice Tongue was straightforward and went smoothly. Skidoo fuel positioned on this flight was later returned to Scott Base by a passing Helo (Italian) after we cancelled that part of the programme due to a lack of field time. The fuel in 20 1 containers was documented and carried with passengers without difficulty. Equipment and resupplies available to us on an opportunity basis were also appreciated. The only concern with helo operations is discussed in the previous Preparations for the Field section.
The Icebreaker Cruise (1-5 February) went very smoothly and the help from the 6 Scott Base staff was appreciated. The ships crew were also very helpful and pleased to be doing some useful science. The dry lab with the 3.5 kHz profiler and GPS receiver were the only ship facilities used. Helicopter operation was not required as part of the scientific plan and the SENZREP's short familarisation. was not part of the scientific programme. No scientific work was carried out on deck in this cruise and normal clothing issue was sufficient. Deck work would require water and wind proof anoraks, salopettes and gloves over which a "Mustang jacket" could be worn. Planning ship operations is discussed previously in section on Planning.
|Sea Ice Programme|
|5 November||Arrive Scott Base. (Pyne, Carter, Gee, Anderson.)page 6|
|6||November||Field Training. (Carter, Gee, Anderson.)|
|Bucket auger tests with Nod well (Pyne.)|
|7 November||Field Training. Auger modifications and tests.|
|8 November||Attach winch on Nodwell and GPS receiver in garage.|
|9 November||Helo Recce. to Granite Harbour and Nordenskjold Ice Tongue. (Pyne, Carter, Gee.) Skidoo fuel cached at ice tongue (76 14 99,162 47 75).|
|10 November||Battery housings fitted on Vibracorer in garage. Checked field equipment. Spliced winch rope.|
|11 November||Vibracorer outside with loader on forks, erect mast tubes, chains and returned vibracorer inside.|
|12 November||Batteries and Electronics tested on vibracorer.|
|13 November||Electrical problems with to shipping.|
|14 November||Electrical problems, (limit switches), packed up sledges.|
|15 November||Final packing and moving out from Scott Base at 1500 hrs. Camp Position: 77 40 83 / 165 28 28 at 2200hrs (38 km from Scott base).|
|16 November||Marble Point at 2030 hrs, weather poor.|
|17 November||Refuelled at helo facility. Bad winds and poor visibility.|
|18 November||Travelling to Cape Roberts, arrived at 2030 hrs.|
|19 November||Cape Roberts; skua count, restocked emergency box. New wind speed/direction and 2nd temperature sensors fitted to Met. tower, down loaded data and checked wiring on Vibracorer, travelled onto Granite Harbour.|
|20 November||Drilled sea ice hole at site 92-1, 736 m deep in Granite Harbour.|
|21 November||Continuity problems with Vibracorer, removed battery housing and batteries (transport damage ?), checked out winch with large weights.|
|22 November||Problems with data logger power, katabatic winds in the evening.|
|23 November||Dead batteries data logger, transducer fault with rev counter, chuck jamming after lowering into water, winch capstan creeping backwards and banging in neutral and braked.page 7|
|24 November||Removed capstan to check on air in the system, replaced it and tested again with weights. Then ran a test using the TAE sledge as a weight.|
|25 November||Tested the winch using the TAE sledge plus the weights to 100 m. At 1830 hrs started to lower the Vibracorer, stopping every 100 m to readjust the Hiab which was sagging. At above 600 m the comms. cable broke, winched the Vibracorer to the surface by 220 hrs. Repair comms cable.|
|26 November||Broken comms cable (D5),repaired. Lowered the Vibracorer down at 1500 hrs, reached the bottom at about 700 m and ran the Vibracorer through coring programme but the barrel did not retract the last 2 m. Vibracorer winched to surface to find the core barrel had been bent about 30 degrees. It took from 2200 hrs to 2400 hrs to remove the bent core barrel from the vibracorer.|
|27 November||DVs visit started drilling new hole about 30 m west of 1st hole, used the winch cable of D5 to saw between the holes. Katabatic winds in the evening.|
|28 November||Prepared the Vibracorer for lowering, started lowering at 1600 hrs. Lowered to the bottom and ran through the same procedures to find that the barrel would not retract. Returned to the surface to find another bent core barrel.|
|29 November||Packed and moved to Cape Roberts.|
|30 November||Science DVs visit, drilled hole for current meter, unloaded the vibracorer for the DVs, surveyor arrived and did local topo survey. Repacked the corer.|
|1 December||Skua count, surveyors permanent staff erected for tide gauge levelling.|
|2 December||Bathymetry and sea ice measurements made along seismic line off shore Cape Roberts to the Ice Edge.|
|3 December||Reprogrammed data logger on Met. tower, repacked sledges, survey of glacier edge Granite Harbour.|
|4 December||Started travelling south at 1000 hrs, complex crack system south east of Spike Cape negotiated. Nodwell flat tyre removed and all deck cargo. Stopped at New harbour at 0130 hrs next day.|
|5 December||Travelling back to Scott Base, large crack in sea ice early in the day (New Harbour Crack), arrived back at Scott Base at 0130 hrs.|
|6 December||Brought tractor train back to Scott Base.page 8|
|7 December||Started dismantling Vibracorer.|
|8 December||Packed up Vibracorer returned cleaned field equipment.|
|9 December||Finished packing.|
|10 December||Carter return to NZ.|
|11 December||Pyne, Gee, Anderson return to NZ.|
|Ice Breaker Cruise (1993).|
|31 January||Pyne, Henrys to Chch and Scott Base.|
|1-5 February||Embark USCGC Polar Star 0900 hrs departure and begin 3.5 kHz survey. Disembark 1700 hrs at McMurdo Pier.|
|6 February||Pyne, Henrys return to NZ.|
The weather was good for most of the sea ice programme and little field time was lost. A day of blowing snow and poor visibility occurred while refuelling at Marble Pt. and 2 katabatic events, each of a few hours duration where experienced in Granite Harbour, (see diary).
Two "sleepy" box sledges were used by this event. Repairs were required in the field to the part where the ski attaches to the sledge which had become damaged due to metal fatigue. This is the result of a design weakness which should be remedied in the future. The plywood sides and ends were in a poor state of repair when the sledges were allocated and should be renewed.
The field food is generally good quality and continues to upgraded each year. Living and cooking in a Wannigan means that more exciting food can be prepared than in a basic tent camp if the appropriate food items were available. Some new occasional "luxury" items could be introduced such as cans of fruit (pineapple, peaches etc.) mushrooms and other vegetables. The other suggestion is that items should be small and usefully packaged for field use, for example chicken pieces instead of whole chickens, small tins items. The new bags of lamb/ pork strips available this season is an example to develop. Some bulk items can be usefully pre processed/packaged at Scott Base, for example grated cheese in ziplok bags. More insulated containers/boxes are still needed for frozen food storage in warm areas (sea ice).page 9
NZ1 was used for cooking and messing between 5 to 7 people. The wannigan is very crowded and the cooking area should be redesigned to provide more useful bench space, a LPG oven/ grill top burner combination in addition to the newly installed microwave. The microwave, cutlery and dishes needs to be secured better for travelling especially over sea ice. The layout of a galley on a small boat could provide a suitable model for redesign. A table in addition to the dining table still should be retained for instruments. Extra seating that doubles as inside rubbish containers are also required. Large containers (210 1 drums or plastic drums) with locking lids are also needed for cargo train rubbish handling.
A 200 mm Fin auger was used to make holes in the sea ice. the cutting edges of these augers are in need if careful machine grinding because hand stoning can't make a sharp lasting edge and new cutting heads could also be purchased.
Radio communications were not very satisfactory during the sea ice season especially in the Granite Harbour area 150 km from Scott Base. Communication was established when needed although with some difficulty. The HF Codan equipment installed in NZ1 is normally good enabling comms with Scott Base using the roof mounted whip aerial but this season it worked satisfactorily only with a dipole aerial from Granite Harbour. The whip aerials and mounting should be checked by an electronics technician before next season. The small "butter box" HF sets were inadequate even from New Harbour (70 km).
The VHF communication is also inadequate. The blind coastal area from Marble Pt. northwards on the Mt. Newall repeater (channel 5) appeared to be larger than in previous years. The Mt. Erebus repeater (channel 3) did not work at all for us this season and was intermittent at best the previous season. We suggest NZAP investigate the siting of a repeater on Mt. Marston which should give good coverage within Granite Harbour and probably southwards along the coast about to Marble Pt.
The VHF equipment is also becoming dated and less reliable. NiCad batteries are always difficult to charge properly in the field and a field discharger may help improve performance. A connector to 12 VDC lead acid cells would also be an advantage for any party with vehicles. The connections to the Hi-Gain aerials also need regular checking, could be replaced with reusable fittings and a flexible cable better suited to field use should be used. New equipment should be less bulky to keep warm inside clothing, still retain the remote aerial option and have a suitable charger/discharger if powered by NiCad batteries.
The Scott Base radio schedule system has almost become too efficient and easy to initiate from the Scott Base end. It is more difficult however in the field especially when travelling and working on tasks requiring concentration over several hours.
Human waste and grey water was returned to the sea via holes drilled in the sea ice. All other waste was returned to Scott base for processing or disposal. An NZAP environmental return is appended.