Perseverance of the ice core specialist

Hubertus Fischer is one of the few researchers to have won two prestigious “ERC Advanced Grants” from the European Research Council. The goal of the current project? A new technique to analyse the world’s oldest ice.

Hubertus Fischer from the Oeschger Centre is one of the main figures in this international initiative to drill into the oldest ice on earth and extract climate information covering the entire last 1.5 million years. In particular, this deep look into the climate’s past should contribute to a better understanding of the interplay between warm and cold periods. About a million years ago – as shown by studies of marine sediments – there was a dramatic change in this interplay. In the time prior to 900,000 years ago, ice ages and warm periods alternated roughly every 41,000 years, but every 100,000 years thereafter. What brought this change about is a mystery, but climate research suggests that greenhouse gases played an important role. An ice core drilling in Antarctica, covering nearly twice the time period of previously analysed ice, should confirm this hypothesis. Ice cores are a particularly powerful climate archive as only they contain the air from the past, which makes it possible to measure past greenhouse gas concentrations directly.

Highly compressed ice at a depth of 2,500 metres

In connection with his ERC Grant, Hubertus Fischer and his team are developing a completely new analysis method for the Oldest Ice project. What’s special about it is that all the greenhouse gases can be measured simultaneously through a single analysis. In addition, the air extracted from the ice samples won’t be lost during the process; instead, it can be used afterwards for further research. Hubertus Fischer calls it “perfect recycling”, noting that “for an ordinary ice core, the huge effort would never be justified – but this is for the oldest ice on earth, of which supplies are extremely limited.”

The €30-50 million “Oldest Ice Project” wants to drill down to the bedrock under the Antarctic ice sheet – about 2.5 kilometres deep. Researchers are especially interested in the lowest 50 to 100 metres, where the ice is extremely compressed. They expect to find thousands of years’ worth of climate history stored within just a few centimetres of the core. This implies that anybody mining this layered archive will have to make do with tiny quantities of atmospheric gases contained in the ice.

New measurement technologies advance research

This non-destructive measurement method doesn’t exist yet, but Hubertus Fischer has a clear vision of how it should work. In order to put these ideas into practice, he has received a strongly contested “ERC Advanced Grant”. It is already the second time that the European Research Council (ERC) has awarded the Bernese climate physicist a grant for cutting-edge research. “The value of new measurement technologies cannot be overstated”, says the professor of experimental climate physics: “Usually, you can only make progress in geo- and atmospheric sciences when you enter new technological territory and if you succeed in measuring things which couldn’t be measured up until now. Nothing beats solid and reliable data.”

The key difference between Fischer’s project deepSLice (“Deciphering the greenhouse gas record in deepest ice using continuous sublimation extraction/laser spectrometry”) and previous methods is that for the first time, both the concentrations of greenhouse gases carbon dioxide, methane and nitrous oxide as well as the isotopic composition of carbon dioxide can be determined by a single measurement of the same sample. On the one hand, this requires a special new measuring device, and on the other hand, new methods must be developed to prepare the sample material. For the measurement device, the project focuses on so-called quantum cascade laser technology, in which two lasers will bombard the same sample with different frequencies to measure the absorption of laser light by the greenhouse gases. Within the framework of “deepSLice”, such a device will be developed together with project partner Empa (Swiss Federal Laboratories for Materials Science and Technology). The device will enable such measurements in air samples of just 1 ml.

The alchemy of sample preparation

The method of gently releasing the air contained in the oldest ice will be at least as important as the actual measuring device; otherwise, the air could be contaminated in the extraction device or via chemical reactions from the ice itself. “The art – the alchemy – is in the extraction. That’s our strength; we’re the world’s specialists for that,” says Hubertus Fischer with an impish smile. The apparatus that Fischer and his team want to build to extract 1.5 million-year-old air will work roughly like this: The ice will be irradiated with infrared light and sublimated, then the water vapour will be frozen on a cold surface and finally, only the components of the atmospheric air will remain.

In Hubertus Fischer’s office there is a strange sculpture made out of signposts. It is modelled after the “Totem poles” to which expedition members at polar research stations attach signs showing how far they are from home. Fischer’s office version was created in 2008 for an informative meeting at the University of Bern. It shows the locations of all of its European ice core partners. One of the signs reads “Oldest Ice, Antarctica” – written in red and punctuated with a question mark. “You can see how long I’ve been thinking about this project,” says the researcher.

Indeed, this project requires a lot of perseverance. If all goes well, the first drilling season will take place in 2019/2020. And by the time the deepest part of the ice core is lifted and can be examined, it will probably be 2022. “The machine that we’re building as part of ‘ deepSLice’ won’t see the oldest ice over the course of the project,” says Hubertus Fischer, “but when the drilling begins, everything has to be finished and tested, and we want to be ready with the perfect analytics.”
(2015)