Research Hub
ANSTO's research capabilities, led by the OPAL nuclear research reactor and associated instruments provide access to users investigating areas as diverse as materials, life sciences, climate change and mining/engineering.
About the science project
Following on from his blogs from Antarctica in 2012 and earlier in 1997 and 2005, ANSTO Research Scientist Dr Andrew Smith is continuing his work studying isotopes produced by cosmic rays, this time from the summit of Greenland where he and a team of researchers will face some of the coldest temperatures on Earth.
The project is a National Science Foundation (NSF) funded scientific expedition #1203779.
The NSF has generously funded Dr Andrew Smith's participation and the transportation of the ice cores he collect back to the USA with ANSTO generously allowing Dr Smith to participate in this expedition.
Thanks also has to be given to the Australian Antarctic Division who assisted with provision of cold weather clothing.
Research collaborators and roles
University of Rochester
Contributors:
- Dr Vasilii Petrenko, Expedition Leader
- Benjamin Hmiel, 1st year Postgraduate student
Radiocarbon, 14C, is produced ‘in situ’ in the ice by cosmic ray neutrons and muons interacting with the oxygen atoms in the water molecules.
Overall, this project seeks to understand the fate of in situ produced 14C in the firn layer and near-surface ice in accumulating ice sheets; this season’s study is focusing on the firn air. The next and following seasons will focus on the firn itself, using the Blue Ice Drill to recover large 10” diameter core and the large melter to recover gases from within the firn ice crystals. This is knowledge is important for: using 14C as an absolute dating tool (if in-situ 14CO2 is not conserved or can be quantified), as a tracer of the past cosmic ray flux (if in-situ 14CO is conserved) and as a recorder of the past fossil fraction of the global CH4 budget (if 14CH4 is not conserved or can be quantified).
Vas is also interested in stable isotopes of CO below the lock-in zone to try and better understand the variations in CO sources and sinks over the last few decades. The air will be extracted and measured at INSTAAR in collaboration with Jim White.
Another interest is in 14CO beneath the lock-in zone, extracted from bubbles in ice; this study will be undertaken next season. Due to the low concentrations of CO in air (seasonal variations in the N hemisphere can range between 80 and 180 ppb, compared with 40 to 80 ppb in the S hemisphere, peaking in the winter due to reduced OH concentrations), the addition of in-situ produced 14CO should make it an ideal tracer and proxy for past cosmic ray flux.
Critical to the project is the establishment of the air age/depth relationship and age spread, which will be undertaken in collaboration with Christo (‘firn air diffusion modelling’). This will use tracers such as the 14C02 bomb pulse, CO2, CH4 and CFCs concentrations, for instance.
Extraction of CO2, CO and CH4 from the firn air gas will be undertaken on the new Rochester processing line.
Rattaché au Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE) & Stony Brook University
Contributors:
- Jerome Chappellaz (LGGE)
- John Mak
Measurement of CO concentrations and stable isotopes. Measurements undertaken by two laboratories will help to verify the record and to improve LGGE’s analytical capabilities.
Scripps Institute
Contributor:
- Jeff Severinghaus
Using neon stable isotopes to study the bubble close-off process.
Neon is strongly fractionated being a small diameter molecule. When bubbles begin to form the walls are thin and as the bubbles become pressurised small diameter molecules are able to diffuse more readily through the walls, significantly changing the concentration of the gases inside and outside of the bubbles. The cut-off for this behaviour is about the size of the krypton atom.
This study will examine if this effect is mass dependent as well as being dependent upon molecular size.
Oregon State University
Contributors:
- Dr Christo Buizert,Postdoctoral Fellow
- Jon Edwards, 2nd year Postgraduate student
Studying the bubble-close-off process (from lock in depth ~65 m to close-off depth ~85 m: the “lock-in zone”). The analysis of the WAIS core showed that bubble close-off is more complex than had been thought when looked at in detail.
Seasonal variations in density will affect the close-off process. It is possible that there are age reversals with depth. Another ramification of this is that there is a minimum age resolution that can be expected and we need to know this, for instance if the exact timing of CH4 peaks with temperature changes in the past is to be determined. It may be that for these reasons 15 years is the minimum age resolution that is possible from ice core studies.
Jon and Christo are also interested in last season’s melt layer and the possible in-situ production of CH4 and N2O within it. NEEM melt layers with low air content had enhanced CH4 and N2O (nitrous oxide) ‘spikes’. It is hoped that last season’s melt layer may reveal the underlying phenomena.
National Oceanic & Atmospheric Administration (NOAA)
Contributor:
- Ed Dlugokencky
Ed Dlugokencky is kindly providing measurement of trace gas concentrations CO2, CH4, CO, H, N2O and SF6 on a collaborative basis on the superior NOAA system.
These definitive CO concentrations and stable CO isotopes measurements will be used in preference to the field measured values. Amongst other purposes, these will be used to help tune the firn air diffusion model.
University of California, Irvine
Contributors:
- Murat Aydin
Measurement of hydrocarbons and ultra-trace gases such as . COS (carbonyl sulphide). Hydrocarbons are good tracers of emissions from combustion. COS is a tracer of biospheric productivity.
Australian Nuclear Science and Technology Organisation (ANSTO)
Contributor:
- Dr Andrew Smith
Andrew is involved in 14C measurements for all Rochester studies using ANSTO’s ‘micro-carbon’ accelerator mass spectrometry (AMS) capability.
Using 10Be as a proxy for past solar variability, along with Curtin/Edwards development of continuous flow analysis (CFA) for efficient processing of samples for 10Be AMS. There is a possible synergy between the 14CO study and the 10Be study as proxies for past solar variability.
Curtin/Edwards measurement of black carbon (BC) aerosols along with establishment of the core chronology using water isotopes and other glacio-chemical species. Other studies are also possible.
Ice Drilling and Development Organisation (IDDO)
Contributor:
- Tanner Kuhl, driller
Testing and development of the Blue Ice Drill (BID) for recovery of large-diameter firn core. Anti-torque springs are a large part of this work. The goals are 22 m in 2014, 120 m in 2015.
Drilling procedure
The Eclipse Ice Drill has an inner barrel with flutes on the outside and a cutting head on the front which fits into an outer barrel.
When drilling it hangs vertically like a pendulum from the cable, which has wires inside to power the electric motor above the barrels; the motor speed is adjustable and the current is monitored.
The cable is wound onto a drum by a mechanism which lays it down evenly. The inner barrel spins and cuts its way into the ice at a rate determined by the ‘pitch’ set with three shoes and the three cutting teeth and by the pressure of the drill against the ice surface. This is adjusted manually by the driller and is a balance between a reasonable cutting rate and the need to keep the drill vertical.
A strain gauge mounted below the sheave measures the tension in the cable and the driller monitors this. The outer barrel is prevented from spinning by anti-torque springs above the motor section which press against the bore hole. The anti-torque springs can leave linear marks down the bore hole which could potentially affect borehole sealing in the upper firn section when it is time to sample firn air.
As the ice is cut, the flutes between the two barrels direct ice chips upwards, ultimately falling back down inside the inner barrel; they either fall on top of the ice core or on top of a ‘little man’, an inverted cup-shaped object that fits inside the inner barrel; this is fastened with a string and allows the chips to be separately withdrawn.
Either way, as drilling progresses the weight of the drill increases as the chips accumulate and this is compensated for by the driller.
The depth of the drill is measured by an encoder on the sheave about which the drill cable passes. The driller can see the total depth and the drilling depth which is reset at the commencement of drilling. Once the required length of core has been cut it is time to take it to the surface.
The top ~20m was drilled using an expandable collet. When the drill is raised this grips the core on the outside and snaps it off at the base. Below this depth a pair of core dogs was used. The core dogs are spring loaded and designed so that they slide along the core while drilling but when the drill is raised they bite into the core and sever it at the base.
The core dogs often leave stripes on the bottom section of the core as they dig in and bite. Once the drill reaches the surface the drillers expectantly watch the bottom of the drill. A ‘carrot’, a small section of core protruding from the drill, with a ‘flange’, a slightly larger diameter at the core end indicate a good drill run.
But sometimes too much core is protruding (a ‘hanger’), sometimes less core than expected is retrieved and sometimes no core at all is retrieved. The first case can be problematic because the drill has to be raised from vertical to horizontal and there may not be enough clearance in the ‘slot’ that has been dug for that purpose. In the other two cases, the driller must send the drill down and again to try and retrieve the missing pieces.
Assuming all goes well, the drill is locked onto a cradle and is raised to the horizontal position when a pin is inserted to prevent the cradle moving and the cable drum is locked in position to the prevent the drill moving. The drill is rotated backwards and any ice chips still in the flutes are expelled from the cutting end.
Then the drill is slowly rotated and stopped so that a tool can be inserted to undo three spring loaded pins that attach the inner barrel to the motor. Once this is done the inner barrel can be removed and it is taken to the ice core logging area.
If a ‘little man’ was used this is taken out, along with the ice chips that have accumulated above it. A plunger is inserted from the cutting end to push the ice core up the inner barrel, firstly pushing out any ice chips above. Finally the ice core is removed and is measured for length and inspected by the loggers before being placed inside a labelled plastic tube and packed into an insulated box, ready for transportation back to the ice core laboratory.
There are 11 springs of different tension for the core dogs, 4 different sizes of core dogs, 5 different shoes (with shims) and 3 different cutting teeth for the Eclipse drill; adjustments are made with depth as the nature of the firn and then ice changes… a complex process!