Up the hill, down South

by Paul Vallelonga

One of the goals of ice2ice is to reconstruct the history of Arctic sea ice from Greenland ice core records. Ice core scientists currently have two methods for doing this (sodium and Methanesulphonic acid, MSA) although in collaboration with colleagues in Italy (University of Venice) and Australia (Australian Antarctic Division, AAD) we are working on a third sea ice proxy: halogens.

The halogen elements (Fluorine, Bromine, Chlorine, Iodine) are highly reactive and happen to be key elements in chemical reactions that take place on the sea ice surface. Understanding the link between sea ice, halogen chemical reactions and ice cores requires that we take samples from a variety of locations, covering the range of variability in sea ice and snow deposition conditions.

Arriving in Antarctica! The Airbus 319 is in the background, on the apron of the Wilkins blue ice aerodrome.

Antarctica is a great place to collect samples because most of the research into sea ice reconstructions are based on Antarctic ice cores and the sea ice variability is somewhat simpler than in the Arctic. I was able to go to East Antarctica to collect snow samples from the Antarctic coast in order to study how all three sea ice proxies (Sodium, MSA and halogens) respond to recently observed sea ice changes.

Getting to Antarctica is pretty easy nowadays: rather than taking a 3 week voyage on an icebreaker through the Southern Ocean, we can just fly there in 4 hours on an Airbus 319 which is chartered by the AAD. This service makes it possible to go to Antarctica, wait for a window of good weather at the sampling site, and then fly back to Australia in less than three weeks!

Driving up to Law Dome in the AAD Hägglunds tractors. The surface was smooth fresh snow which allowed us to travel up to Law Dome without too many bumps.

Setting up camp at Law Dome. The two “Häggs” are in the background. Note the perfect drilling conditions: clear skies and no wind!

Together with Tessa Vance (AAD researcher) and an expert support team we drove up to Law Dome for the sampling. Law Dome is a special zone of high snow accumulation as it receives over a metre of snow every year, and has been a site for studying sea ice reconstructions for more than 20 years. We spent two days at Law Dome, during which we drilled an 8 metre snow core and sampled surface snow around the drill site. The support team also set up a weather station, so we know more about the local conditions at Law Dome over the coming years.

Tessa drags equipment to the sampling site. We did the sampling 175 metres upwind from the camp to ensure that diesel emissions from the tractors did not disturb the samples we collected.

Logging the snow core length and storing it in plastic bags for transport back to Australia. In the background, Tessa is drilling the next sample.

The automatic weather station is now up and running. There is so much snow accumulation at Law Dome that the 7 metre high pole will need to be replaced in 3 or 4 years otherwise it will be completely buried!

The next step is to do the measurements. All three sea ice proxies (Sodium, MSA and halogens) will be measured in parallel in the snow core and snow surface samples to produce a consistent story about sea ice at the Law Dome coast over the past 5 years. These measurements will be done in Australia, in Italy and at the Centre for Ice and Climate in Denmark.

I hope to present the results at the upcoming European Geophysical Union conference in Vienna in April.