This week at Casey: 2 March 2012

One of the last flights of the season into Wilkins Aerodrome began much like any other; the Wilkins crew was out of bed around midnight to prepare the runway for the incoming A319 flight and just before sunrise the expeditioners at Casey station rose to drive the 70 kilometres inland to the aerodrome.

On this particular morning a forward party consisting of a truck full of boys (Tim, Nigel, Michael, Jan, Glenn and Dave) struck out first from the station, followed by a Hägglunds full of girls (Caz, Bec, Nisha and Annalise). The truck roared off in a shower of snow, tail lights glowing, leaving the girls to putt along behind at a bumpy Hägg pace.

However, soon those same tail lights came into sharp focus again. The truck was well and truly bogged up to its axles in soft snow. How the boys had managed to do this only they know. It was well and truly stuck. They were standing around, frowns on their faces and scratching their behinds, looking at each other in bewilderment wondering how to tackle the task at hand of freeing the truck.

Equipped with superhero capes, the girls bounded out of the Hägg (accompanied by the appropriate superhero music) and put their winch training into practice. With those boys looking on in amazement the truck was soon rescued from its icy grip and, after whispering their thanks, once again roared off towards Wilkins. We girls then packed away all the winching equipment, checked our vehicle to ensure further safe travel was possible and continued on our way, slowly and cautiously.

After another few bumpy hours we soon neared our destination, but again saw a set of tail lights parked at an odd angle in the distance. The truck was once again bogged when it “pulled off” at a scrub down station prior to entering the aerodrome precinct. Unbelievably those boys were scratching those same behinds, though this time when they saw us approaching, sheepishly requested further assistance. As if it was a daily occurrence, those same girls, again, came to the rescue and, of course, have never mentioned their tale of heroism to anyone.

Needless to say, we girls arrived at the Wilkins Aerodrome on time and before the boys with their toy.

During the month of February a field party consisting of two scientists (Andy and Ulla) from the Australian Nuclear Science and Technology Organisation (ANSTO), Casey’s Senior Field Training Officer (James) and one of the station's Senior Diesel Mechanics (Cam) set off to Law Dome with the intention to recover shallow ice cores and snow pit samples to assist with studies of the variability of our local star — the Sun.

The Hägglunds ride to Law Dome took approximately 5 hours with work commencing immediately on arriving at 1930.  James and Cam quickly dug a 1m snow pit while Andrew and Ulla prepared the equipment to take PICO cores using a hand-powered auger.

With the pit dug, Andrew commenced to square off on face of the pit — the quarrying face.  At 0100 the snow pit sampling was completed with thirty six 10x10x20 cm samples taken from various levels.  By 0200 the PICO coring was completed with three cores of 3m length and one at 5m length successfully extracted.

This completed the first stage in what will be an unusual journey for the samples, or at least for the beryllium-7 (⁷Be) and beryllium-10 (¹⁰Be) atoms that are trapped in the ice sheet. These atoms are radioactive isotopes of beryllium that were produced in the atmosphere by cosmic radiation.  Cosmic rays continually bombard the Earth, originating deep in the universe, probably from distant supernova.  When they collide with the oxygen and nitrogen nuclei in the Earth’s atmosphere they smash them into smaller pieces and these smaller pieces in turn cause more nuclear reactions to take place as the energy of the initial cosmic ray is lost. 

Some of these nuclear reactions give rise to ⁷Be and ¹⁰Be that become attached to aerosols and are transported though the atmosphere to the surface of the Earth.  Because polar ice sheets are annually layered we can tell when they made it to ground.  But to detect them is a complex business and requires a very specialised technique called Accelerator Mass Spectrometry, or ‘AMS’ and a very large particle accelerator called ANTARES at ANSTO in Lucas Heights, Sydney.  ¹⁰Be has a very long half-life of 1.4 million years, so we have plenty of time to make the measurements.  ⁷Be has a very short half-life of 53 days, and this is where the Australian Antarctic Divisions Air Link comes in: we are able to rapidly return the samples to Australia, process and get them in to the accelerator quickly for measurement.  Speed is of the essence!

The rate at which the ⁷Be and ¹⁰Be is produced depends upon the intensity of the Sun.  This is because most of the cosmic rays are electrically charged particles and are thus deflected by the Sun’s magnetic field that permeates our Solar system.  For instance, the well-known 11 year Solar cycle can be readily distinguished in the measured concentration of ¹⁰Be in the ice sheet.  But the Sun also varies over much longer timescales and we are interested to know about this because the Sun drives the Earth’s climate system.

Once the samples make it back to Hobart the three short cores are cut to size, combined, melted, filtered and passed through an ion exchange column; this is then returned to Sydney for further processing with ¹⁰Be atoms trapped inside. Snow pit samples from each level are combined and processed similarly, but this time we are also interested in the ⁷Be atoms trapped along with the ¹⁰Be atoms.  But without an accurate chronology all this effort would be wasted. This is where our colleagues in the Antarctic Division play an essential role, establishing the chronology of the longer core and matching it and the other samples to the ‘master’ DSS chronology.

This Antarctic Science project (#3064) doesn’t aim to go far back in time, but rather to develop a detailed record, at monthly resolution, of ⁷Be and ¹⁰Be concentrations.  In combination with neutron monitor data, satellite observations of the Sun and numerical Global Circulation Models (GCMs) we are trying to separate atmospheric transport effects from the production signal.  We have been doing this since 2000 and we are now better able to interpret the much longer records we hope to take in future years.

After collecting the samples our work was not over and the remaining tasks were still being finalised at 03:00 by the Hägglunds’ headlights with the full moon in the sky and the sun rising on the horizon.

Then began the long journey back to Casey, arriving at 09:15 on Friday.

All up, a good day’s work!

Winter is indeed coming as the overnight minimum of −18 degrees reminded us all during the week. As well as looking to finish off the summer science and works programs, people on station are also turning their attention to preparing the winter expeditioners for the seven months of isolation ahead. This preparation includes finalising training on vehicles and field travel and ensuring that wintering personnel get plenty of experience out in the elements.

During the week the last three wintering expeditioners to receive their training in driving Hagglands tracked vehicles were given their tickets (Mark the Station Leader, Sheri the Doctor and Craig the Senior Met Observer). The training included learning to drive with the windows blacked out and only using GPS and radar — to simulate whiteout conditions during a blizzard. This was equal parts good fun and terrifying, depending to some extent on who was behind the wheel (no names please). 

As well as Hagg training most of the wintering group had a chance to go polar camping, staying out in Polar Pyramid tents on the Mitchell Peninsula in two groups. Group 1 (Mark H, Sheri, Craig, Cam, Dan, JLo and James the SFTO) enjoyed a beautiful night out in balmy conditions barely below freezing. Group 2 (Mark G, Rob, Jason, Mike, Phill, Jeb, Bri, Gavin, Dave, Andy and James again plus FTO Ian) ‘enjoyed’ a night out in somewhat more challenging conditions that included strong winds, driving snow, and temperatures 10 — 15 degrees cooler. What a difference a couple of days makes! Bad luck guys. 

Despite variable weather and the hardships of being away from our accustomed fine dining and the benefits of plumbing, everybody enjoyed the chance to get out into the Antarctic wilderness and away from the hustle and bustle of life on station.

The next training challenge for the wintering team will be a solid week’s work on Search and Rescue (SAR) scheduled for a couple of week’s time.