Pascal Bohleber and his 3 ‘Marie Curie’ grants to advance ice core science

Ice cores tell us about  hundreds of thousands of years of environmental and climate history of our planet. In Antarctica, European scientists are about to drill the oldest continuous record ever, to date back to 1,5 million years ago. Specialists at Ca’ Foscari University of Venice and at the Institute of Polar Sciences and other few research centres in the world know how to read those history books. However, they know also that new methods and technologies will improve their capability of reading between the lines.

Pascal Bohleber is a German physicist, glaciologist and ice core scientist with a broad interest in the cryosphere. He contributes at the forefront of the scientific challenge of expanding the knowledge on the messages trapped inside the deep ice.

He arrived at Ca' Foscari in 2019 thanks to a Marie Skłodowska-Curie individual fellowship granted for the project Gold-Ice. Recently, he has been awarded a second ‘Marie Curie’, a return ticket to the University of Maine (USA), to work in another state-of-the-art laboratory of Prof. Paul Mayewski. In the meantime, the Ca’ Foscari team led by professors Carlo Barbante and Barbara Stenni contributes to a Marie Curie Innovative Training Networks project, that is looking for 15 talented PhD students who will be trained in state-of-the-art ice-core related climate science with a particular focus on Antarctica. Bohleber will supervise one of those students.

The common thread among those achievements and projects is an analytical, innovative method called ‘laser ablation inductively-coupled plasma mass spectrometry’ or LA-ICP-MS. Why is it so special and promising?

To prepare for future climate change, we need to understand the fundamental dynamics of our climate system. We hope to find an important piece of this puzzle in the deepest and oldest ice layers of Antarctica. However, the deepest layers are inevitably highly thinned, thus calling for ice core analysis at an unprecedented level of detail. LA-ICP-MS is a high-resolution, micro-destructive technique, with only a few tenths of microlitre of ice ablated from the surface by the laser. The ablated sample is transported by an inert carrier gas to the mass spectrometer, where it is analysed for various elemental impurities. My first Marie Curie project GOLD-ICE demonstrated how the application of LA-ICP-MS for imaging the 2D impurity distribution in ice cores can be refined and strongly improved.

How did you choose to study in this field? What were your first steps?

Ever since I was a student at Heidelberg University the interdisciplinary nexus of ice core science has fascinated me, especially the study of deep layers with highly thinned layers. Soon after finishing my PhD in Physics from Heidelberg University in 2011, I obtained my first postdoctoral scholarship to visit the group of professor Paul Mayewski at the University of Maine, USA. I was intrigued by the potential of laser ablation inductively-coupled plasma mass spectrometry. At that time, Mayewski hosted one of just two world-wide existing LA-ICP-MS systems for ice core analysis. That fellowship gave me the opportunity to work on an Alpine ice core focusing on deciphering highly thinned annual layers. After my return from the USA I continued to investigate the deepest and oldest ice layers in the Alps at the Austrian Academy of Sciences.

What inspired you to write a project and choose Ca’ Foscari as host institution?

I was looking for a new opportunity to realize some of my new research ideas around LA-ICP-MS, and the chance to pursue applications also to polar ice cores. Through a fortunate coincidence, I met professor Carlo Barbante at a conference in Paris in 2017. He shared the fascination for the potential of LA-ICP-MS, especially because of his leading role in the “Beyond EPICA: Oldest Ice Core” project. The synergy created between Ca’ Foscari and the Institute of Polar Sciences of the CNR constitutes an important asset for the research in polar regions, making Venice the “pole” of polar research in Italy. Since Barbante was already on his way to set up a LA-ICP-MS system at Ca’ Foscari, our interests were a perfect match. He encouraged me to apply for a Marie Curie European fellowship so that we could work together in Venice. Thanks to the invaluable assistance of the research office I was able to obtain this fellowship in 2018 and start my project GOLD-ICE in Venice in January 2019.

What did you accomplish with this project?

Despite the time invested in setting up the instrument and, not least, delays due to COVID-19, I find that GOLD-ICE has been a great success: by using LA-ICP-MS we were able to introduce a new method to map the spatial distribution of impurities on the ice surface – in 2D. This promises not only new insights into impurity distribution in deep ice core parts but also delivers an improved understanding of the LA-ICP-MS signal origin in ice cores. This can play an important part in disentangling climate- and crystal-related signal components in the LA-ICP-MS analysis of the ‘oldest ice core’ from Antarctica.

Could this technology change ice core science?

In my view, the evolution of laser ablation technology and further refinements in its application to ice cores will render the imaging of even larger ice samples feasible in the near future. In order to analyze an entire ice core, the use of a large cryogenic chamber will be key – and Mayewski has uniquely pioneered the combination of such large cryocells with LA-ICP-MS. Mayewski is also a widely recognized expert on abrupt climate change, another important research field closely linked to high-resolution ice core analysis.

You will soon have the chance to work in that lab and then return to Ca’ Foscari...

Yes, my newly funded Marie Curie Global Fellowship, MICRO-CLIMATE, now brings together, for the first time, two state-of-the-art LA-ICP-MS setups (at the Universities of Maine and Venice) to realize what one partner could not achieve alone: high-throughput and high detail 2D analysis for constraining signal preservation. This will allow us to study abrupt climate change events in Greenland ice cores at an unprecedented level of detail, promising new insights into the mechanics of abrupt climate change, which is also important to better understand our ongoing rapid warming. MICRO-CLIMATE will also advance our understanding of how to interpret ice core geochemistry at high-resolution and produce a refined LA-ICPMS application that can be employed in upcoming ice core projects.
Through the Marie Curie fellowships and the support of Ca’ Foscari my career has taken a great leap forward and I envisage continuing further on this fruitful path as an ice core scientist at Ca’ Foscari.

Enrico Costa