Q&A Interview: Digging Deep: Ion Chromatography and Climate Change

LCGC spoke to Dr Ailsa Benton — an “ice core” analytical scientist from the British Antarctic Survey (BAS) research team— about the role of chromatography in climate change.

Q. What is your role in British Antarctic Survey (BAS) team?

A: I have worked at the British Antarctic Survey for nearly three years. BAS is a world- leading environmental research centre and is responsible the for the UK’s scientific activities in Antarctica.

I drill and analyse ice cores from both polar regions, revealing their chemical composition with a suite of instruments ranging from simple ultraviolet (UV) detection to inductively coupled plasma mass spectrometry (ICP–MS) and fast ion chromatography (FIC). I melt down the ice cores, which are essentially a record of climate and how environmental conditions have changed over time. This information is preserved in snow that has transformed to ice – the oldest ice lies deeper in the ice sheet. The melt water I produce is then subjected to different analytical techniques while preserving the resolution of the annual layers in the ice as one metre of core can contain many thousands of years of snow accumulation; therefore melting slowly to preserve resolution as you go deeper in to the ice core maintains a detailed chronology of the environmental record.

Q. What is the research project that you are currently working on?

A: I am currently working on a project mapping the climate of the Southern end of the Antarctic Peninsula over a 300-year period, using ice cores from six different sites, many hundreds of kilometres apart. The logistics for retrieving these cores are very challenging and BAS provides this expertise.

Q. What are you measuring in the ice-cores and why?

A: I measure a number of chemical constituents that help to determine the age of the ice by counting the peaks and troughs as we go deeper into the ice. These are linked to seasonal cycles, rather like counting tree rings. For example, hydrogen peroxide requires light and ozone for its formation and can reveal when solar minima and maxima occurred. I also measure certain chemicals that can be used as “proxies” for an environmental conditions, including methane sulphonic acid which can indicate the extent of sea ice in the region and aluminium which helps to determine the dust composition of the predominant winds.

Q. What methods do you use to analyze ice cores?

A: I use a method that I call “continuous flow analysis with trace elements” together with FIC. This describes my method of melting the ice cores down continuously and feeding the melt water to a variety of analytical instruments through very narrow bore tubes to maintain the depth resolution of the ice core. The ice cores melt at roughly 3 cm per minute, giving me approximately 10 mL/min of melt water to divide between my various analytical instruments.

The system comprises a de-gassing stage, an ICP–MS system, an FIC instrument, two fluorescence detectors for ammonium and hydrogen peroxide detection, a UV detector for nitrate detection, a particle counter and a conductivity detector. I use ICP–MS to determine elemental composition of the ice. We are particularly interested in magnesium, potassium and calcium for indications of salinity, which can tell us about open oceans as opposed to those covered with sea ice in the vicinity.

I also use FIC to look for sulphate, an indicator of volcanic activity, chloride, which informs us about sea water and atmospheric circulation patterns, and nitrate, a biproduct of oxidation of the atmosphere, among other analytes.

Since the samples are so precious, it is a challenge to run all these instruments concurrently, whilst melting the inhomogeneous sample at a controlled speed.

Q. Why have you chosen to study this location?

A: I have been fortunate enough to participate in ice core drilling projects in both Greenland and Antarctica. Choosing a drilling site requires collaboration with radar geophysicists and glacial flow modellers to choose appropriately aged sites and those that are undisturbed in chronology. I have just returned from a three-month project retrieving three cores from around 74° South where the Antarctic Peninsula meets continental Antarctica.

These sites were chosen for their relatively high snow accumulation rate, which yields detailed seasonal records and also because they are in one of the most rapidly warming regions of the planet over the past 50 years. We want to find out what the climate was like in this region before industrialisation to put recent changes into context.

Q. What challenges do you face in your field of research regarding analytical methodology?

A: Since these ice cores are drilled in the cleanest places in the world they can often be cleaner in terms of chemical composition than the “ultra” clean water we use in the lab as our “blank”. Therefore, sensitivity and the limits of detection are my biggest challenges. Our laboratory and analysis system is specially designed to use only the cleanest part of the ice core and to maintain sterility when getting from the sample to the instrument. I’m always interested in new analytical techniques that can achieve lower and more precise concentration determination. Achieving low sensitivity with elemental sulphur is currently my biggest challenge.

Q. In your opinion, is the reported climate warming observed since the 1950s natural or man-made?

A: Climate records from the west coast of the Antarctic Peninsula show that temperatures in this region have risen by nearly 3 °C during the past fifty years. BAS research has shown also that near-surface sea temperatures to the west of the Peninsula have risen by over 1 °C over a similar period. Climate models cannot reproduce the observed levels of warming without including a man-made factor, which in my opinion indicates an anthropogenic influence on climate. However, there is much yet to be understood about the magnitude of both positive and negative feedbacks in the earth system and the significance of recent changes in a longer context.

Q. Where is the most exciting place you have been with your work?

A: My field-work on ice cores has taken me to some of the most remote and isolated places on earth. Before joining BAS I measured atmospheric composition in both clean and polluted places, as varied as a beach in West Ireland and on top of a tall tower in London. However, I have just returned from the most exciting and beautiful place: I spent 50 days in the interior of Antarctica with one engineer and one field assistant for company, sharing a rather small tent at far-sub-zero temperatures to drill three ice cores. There are many stories to tell from such an experience where all your food supplies freeze and 24-hour daylight means you lose track of a normal working day very easily. Suffice to say, Antarctica is in my opinion, the most beautiful and intriguing place on this planet. It requires investigation in an environmentally respectful manner so that it may be preserved and understood as much as possible.

Dr Ailsa Benton is an ice core analytical scientist with the British Antarctic Survey (BAS). An analytical chemist in the field of paleoclimatology, she graduated with a PhD from the University of Cambridge in 2010. Since then, she has worked for BAS on deep field ice core drilling projects in both Greenland and Antarctica.

E-mail: aibe@bas.ac.uk

Website:http://www.antarctica.ac.uk/about_bas/contact/staff/profile/ailsabenton