The sound of an ice core
Listening to climate change over deep time with Dr Dieter Tetzner of the British Antarctic Survey for an episode of Short Cuts on BBC Radio 4.
“Understanding climate change can be a problem of temporal perspective,” explains ice dynamics and paleoclimate scientist Dr Dieter Tetzner. “You have to think in timeframes of thousands of years, of tens of thousands of years, of hundreds of thousands of years.” I’m in headquarters of the British Antarctic Survey in Cambridge. There is a conference about the “Doomsday Glacier” going on upstairs, but Dieter and I are down in the ice core lab, where columns of snow from by-gone millennia are being melted, piece-by-piece. Drilled from the ice sheet in cylinders (known affectionately in French as ‘carottes de glace’, or ‘ice carrots’), ice cores are formed of compacted snow and trapped air bubbles that contains atmospheric information about the temperature of the planet, from the present at the surface to the distant past nearer the bedrock.
“It's basically a time machine,” Dieter says. The deeper you dig, the further back you go. Volcanic ash, atomic radiation, phytoplankton, micrometeorites and now microplastics all appear in the ice. Such is the spike in nuclear matter frozen into the ice before the Test Ban Treaty in 1963 that scientists use it as a timestamp. “It's like reading a book,” Dieter continues, although you could also call it a charge sheet. “Each of the pages, each of the layers that we can analyse in the ice brings information about the story of the climate on the planet.”
So far, ice cores have narrated 800,000 years of continuous information about planetary temperature fluctuation - mapping eight ice ages, roughly one every 100,000 years - and its relationship to carbon dioxide in the atmosphere. Since the beginning of the industrial revolution roughly 200 years ago, levels of CO2 measured in the ice have rocketed far beyond anything seen in the last 800,000 years. The research here makes that pretty clear. We are now just waiting for the temperatures to catch up.
Last year I visited Dieter at the BAS offices in Cambridge several times, first to learn about ice cores and then to make an audio documentary for Short Cuts, which was aired on BBC Radio 4 in late December as part of an episode called ‘Earth’. The piece is called ‘Melt Tones’ and it explores the relationship between climate change and deep time through the sound of an Antarctic ice core.
You can listen to ‘Melt Tones’ on the ‘Earth’ episode of Short Cuts here.
Alongside Dieter’s interview, all the sounds featured were recorded inside the ice core laboratory at BAS in Cambridge, many inside the -25c degree walk-in freezer where Dieter and his colleagues melt the ice under controlled conditions. You need to wear a padded jumpsuit and snow boots to enter. I had to leave my Zoom microphone in the fridge for 30 minutes before entering to prepare it for the cold; the batteries lasted less than an hour; the wires froze into solid rods; and everything had to be sealed in a plastic bag before leaving the freezer to avoid the accumulation of condensation which would then freeze on re-entry. I was only in suburban East Anglia, but I’ve never had to record under such challenging conditions.
Short Cuts is by virtue concise, but after spending time with Dieter, I ended up with several hours of conversation which could not be included in the 8-minute audio documentary. I’m hoping to publish more of this interview in the coming weeks here which, although not all related to sound, offered some fascinating and imaginative insights about Antarctica and how we map, record or archive our impact on the planet.
I’d also like to say thank you to Andrea Rangecroft at Falling Tree Productions for commissioning and helping me put together the piece, and Dieter and his colleagues at BAS for letting me poke around with my microphones while they worked.
I hope you enjoy the episode, and if you’re not familiar with it, do check out the incredible archive that Short Cuts have built up over the last twelve years. In late 2024, the BBC announced they would be discontinuing the series, which is both very sad and seriously short-sighted, given how few spaces there are for adventurous audio on the BBC and the role the series has as a springboard for first-timers like myself. You can still sign an open letter to the BBC concerning the decision which currently has over 1,500 signatories, and articulates better than I can what an impact this series has had. The final Short Cuts episode, ‘Midnight’, aired yesterday.
Beautiful read and the Short Cuts episode was brilliant, both very poetic.