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

OPTICAL PROPERTIES OF SEA ICE (K132)

page 97

OPTICAL PROPERTIES OF SEA ICE (K132)

Event Summary and Aim

The aim of this year's field event (K132) was to measure the visible and UV light field in and under sea ice and the accompanying seasonal changes as the structure of the ice changes. This was an extension of work carried out during the 1965/86 and 1986/87 seasons in which we were able to characterise the visible light field and observed for the first time that the transmission of light by sea ice decreased as the season progressed. This was found to be associated with increasing turbidity of the ice as brine drained from the surface because of the summer warming. The significant result for 1989/90 is that we have extended the measurement technique into the UV and have confirmed that the same results apply in this spectral range. In particular, we have observed that because of the coincidence of the ozone hole and the period of high UV transparency of sea ice, there is a ten-fold increase in total yearly UV dose for organisms living under sea ice.

Planning

The Tekapo event briefing session was helpful in planning the event. Antarctic Division staff were helpful during this phase, and at Scott Base Garth Varcoe and Eric Saxby, in particular, were helpful.

Cargo

Approximately 10 wooden boxes were shipped from PEL along with a much larger number from K131. On arrival at Scott Base it was found that water had got into some of the boxes. Although no damage resulted this was just fortuitous as most of our equipment is water sensitive. It is important that in future all our cargo is kept dry.

Preparations for the Field

J Southon and R G Buckley arrived at Scott Base on 16 October and were briefed by Don Hammond and Dave Geddes. All our equipment was found to have arrived, although it was clear some of it had got wet in New Zealand. On 17 October we commenced our sea ice survival course. We spent until October 22 in preparation for the field and waiting for the weather to clear. On Monday 23 we made our way to Tent Island and set up camp with K131 in exceptionally good weather. In setting up the camp Garth Varcoe was very helpful.

Field Equipment

In general the field clothing and equipment used in the field was of a high standard and in good condition.

Field Transport

The new motor toboggan we were issued with gave us no trouble, although the cover was found to be unsatisfactory in high winds as elastic gave out.

page 98

Radio Communications

The radios issued to us worked well, and all radio communications were satisfactory.

Event Diary

Oct 16 Buckley and Southon travel to Antarctic
Oct 17 Sea ice training
Oct 18 Snow craft course for Southon, preparation for the field.
Oct 19 Preparation for the field.
Oct 21 Preparation for the field.
Oct 22 Preparation for the feild.
Oct 23 Travel to experimental site, Tent Island, and set up camp with K131.
Oct 24 Continue with set up of camp.
Oct 25 Very bad weather, −19°C wind ~ 30 knots. Visit Camp Evans to help with compressor.
Oct 26 Start optical experiments near camp site - site A. Trodahl and Riches fly to Antarctic.
Oct 27 Continue optical experiments at site A.
Oct 28 Instal thermistor array and continue optical work at A. Sea ice course for Trodahl and snow craft for Riches. Trodahl arrives at Tent Island.
Oct 29 Continue optical work. Begin heat capacity experiment on ice at site A. Riches arrives at Tent Island.
Oct 30 Calibration of optical sources. Continue heat capacity experiment.
Oct 31 Undertake a complete set of optical experiments and sea ice physical property measurements near camp.
Nov 1 Continue heat capacity and ice core photo at site A.
Nov 2 Physical property measures, core photo and optical experiment at new site, site B.
Nov 3 Repeat optical experiments at site A. Initiate density measurements at site A.
Nov 4 Very high winds, no work.
Nov 5 High winds again. Trodahl to Scott Base.
Nov 6 UV backscattering at site A, high winds.
Nov 7 High winds, no work.
Nov 8 High winds still, some optical work but data of poor quality.
Nov 9 Good day. Full optical and physical property measurements including density at sue A.
Nov 10 High winds again, no work.
Nov 11 High winds.
Nov 12 High winds.page 99
Nov 13 Full set of optical and physical property data at site A.
Nov 14 Buckley back to Scott Base.
Nov 15 Buckley fly to New Zealand, some optical measurements.
Nov 16 Pack up camp.
Nov 17 Trodahl, Southon and Riches return to Scott Base.
Nov 18 Bad weather prevents travel to New Zealand.
Nov 19 Bad weather prevents travel to New Zealand.
Nov 20 Bad weather prevents travel to New Zealand.
Nov 21 Trodahl. Southon and Riches return to New Zealand.