Scanning ice cores for climate clues

Ice on the Line

Video transcript

ICE ON THE LINE

Our extensive archive of ice cores is giving up new clues about past climate

Dr TAS VAN OMMEN, Australian Antarctic Division:

Line scanning is a really good example where new technologies come along and offer us the ability to derive new science from cores we might have drilled a decade or more ago.

DR TESSA VANCE, Antarctic Gateway Partnership at University of Tasmania:

An ice core line scanner is a giant piece of very expensive equipment that is basically a very big photocopier.

The scanner reveals thin bands in the ice that could indicate changes in snowfall

DR TESSA VANCE, Antarctic Gateway Partnership UTAS:

Most of the time people have assumed that accumulation in ice cores is relatively uniform throughout the year, but that’s as nonsensical as assuming that rain falls gently all of the time. It doesn’t, it doesn’t anywhere on the earth, so investigating how episodic that snowfall is really interesting because it gives you an understanding of how variable it can be as well.

Dr TAS VAN OMMEN, Australian Antarctic Division:

Drifting snow across the surface leaves a polished surface on the ice, and that can tell us something about periods where there hasn't been snowfall or there have been excessive winds, and we can relate that then to the chemical signatures in the ice.

The key is finding similar bands that are common in ice cores across a large area

DR TESSA VANCE, Antarctic Gateway Partnership UTAS:

We have a scale along the side so we can date the ice cores, and then we know exactly what depth these lines are at in each ice core, so we can find the year that they’re in.

Written in the ice cores are clues to the future of the Antarctic ice sheet

DR TESSA VANCE, Antarctic Gateway Partnership UTAS:

In Antarctica, we get these episodes called ‘atmospheric rivers’ which are essentially rivers in the sky of huge amounts of precipitation coming from the sub-tropics down to Antarctica. Understanding how they vary through time is really important to understand how the surface mass balance of Antarctica can change over time.

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Scientist looks into ice scanning machine
Dr Tessa Vance loads an ice core into the line scanner (Photo: Mark Horstman)
Two scientists in freezer with line scannerRed light shining through iceInterior portion of ice core from 59 metres depthScientist in red light with line scanner

Antarctic scientists are using a high-tech camera to peer inside ice cores and reveal new clues about climate.

Ice cores contain air bubbles, melt layers, isotopes, dust, crystal structure, and sea salt that are used to reconstruct climate histories.

Palaeoclimatologist with the ARC Antarctic Gateway Partnership at the University of Tasmania, Dr Tessa Vance, is also finding fine lines in ice cores with a scanner she describes as “a big expensive photocopier”.

“The line scanner gives us these really high quality images. It reveals fine lines that are quite thin, a millimetre or two, with quite sharp boundaries,” Dr Vance said.

“We have a scale along the side so we know exactly what depth these lines are at in each ice core - we can then use the established date of each ice core to identify the year they occurred in.”

“At the moment we’re still in the process of trying to date the lines because we’re still getting the chemistry and isotope data analysed for the Mt Brown cores.”

Dr Vance led the Australian Antarctic Program team that collected the ice cores in 2017 from Mt Brown, 330 km east of Davis research station.

Now she wants to use the lines found in the ice for climate analysis, but how they were created remains a mystery.

“At the moment we’re going with the idea that it might be something like a temperature inversion, where the temperature near the ground is actually warmer than the temperature above the ground, and that usually happens in atmospherically calm situations.”

“It could be a meteorological process like this, or even the polishing of persistent layers by drifting snow.”

“I’m really excited to see whether these line boundaries define changes in snow accumulation,” she said.

“Most of the time people have assumed that accumulation in ice cores is relatively uniform throughout the year, but that’s as nonsensical as assuming that rain falls gently all of the time.”

“In Antarctica, we get these episodes called ‘atmospheric rivers’ which are essentially rivers in the sky of huge amounts of precipitation coming from the sub-tropics down to Antarctica and falling as snow.”

“Understanding how snowfall varies through time is really important to understand how the surface mass balance of Antarctica can change over time,” said Dr Vance.

Ice core scientist with the Australian Antarctic Division, Dr Tas van Ommen, said the line scanning can unlock more of the information ‘encoded’ in the layering of ice.

“By relating that to the chemistry, we think we can actually get more bang-for-buck from drilling a core in the first place,” he said.

“I think the line scanning will offer us a way of going back at relatively low expense and systematically looking at cores we've collected in the past and actually mining them for additional information.”