The three authors have been studying a sea level rise that took place 129,000 years ago.
By Chris Fogwill, Chris Turney and Zoë Thomas
The Conversation
Rising global temperatures and warming ocean waters are causing one of the world’s coldest places to melt. While we know that human activity is causing climate change and driving rapid changes in Antarctica, the potential impacts that a warmer world would have on this region remain uncertain. Our new research might be able to provide some insight into what effect a warmer world would have in Antarctica, by looking at what happened more than 129,000 years ago.
We found that the mass melting of the West Antarctic Ice Sheet was a major cause of high sea levels during a period known as the Last Interglacial (129,000-116,000 years ago). The extreme ice loss caused more than three metres of average global sea level rise – and worryingly, it took less than 2 degrees Celsius of ocean warming for it to occur.
To conduct our research, we travelled to an area on the West Antarctic Ice Sheet and drilled into so-called blue ice areas to reconstruct the glacial history of this ice sheet.
Blue ice areas are areas of ancient ice which have been brought to the surface by fierce, high-density winds, called katabatic winds. When these winds blow over mountains, they remove the top layer of snow and erode the exposed ice. As the ice is removed by the wind, ancient ice is brought to the surface, which offers insight into the ice sheet’s history.
While most Antarctic researchers drill deep into the ice to extract their samples, we were able to use a technique called horizontal ice core analysis. As you travel closer to the mountains of the ice sheet, the ice that been brought to the surface by these winds progressively gets older. We then were able to take surface samples on a straight, horizontal line across the blue ice area to reconstruct what happened to the ice sheet in the past.
Our team took many measurements. We first looked at the fine layers of volcanic ash in the ice to pinpoint when the mass melting took place. Alarmingly, the results showed that most ice loss happened at the start of Last Interglacial warming, some 129,000 years ago – showing how sensitive the Antarctic is to higher temperatures. We think it’s likely this melting started well before the ocean warmed by 2 degrees Celsius. This is concerning to us today, as ocean temperatures continue to increase, and the West Antarctic is already melting.
We also measured temperature-sensitive water molecules across the blue ice area. These isotopes revealed a large shift in temperatures, highlighting a major gap in our record at the start of the Last Interglacial. This indicates a period of sustained ice loss over thousands of years.
This period of missing ice coincides with extreme sea level rise, suggesting rapid ice melt from the West Antarctic Ice Sheet. DNA testing of ancient microbes preserved in the ice revealed an abundance of methane-consuming bacteria. Their presence suggests that the release of methane gases from sediments under the ice sheet may have also played a role in accelerating the warming process.
The West Antarctic ice sheet can tell us a lot about the effect of warming ocean temperatures because it rests on the seabed. It’s surrounded by large areas of floating ice, called ice shelves, that protect the central part of the sheet. As warmer ocean water travels into cavities beneath the ice shelves, ice melts from below, thinning the shelves and making the central sheet highly vulnerable to warming ocean temperatures. This process is currently being researched on the West Antarctic Thwaites Glacier, nicknamed the “Doomsday Glacier”.
Using data from our fieldwork, we ran model simulations to investigate how warming might affect the floating ice shelves. These ice shelves protect the ice sheets and help slow the flow of ice off the continent. Our results suggest a 3.8 metre sea level rise during the first thousand years of a 2 degrees Celsius warmer ocean. Most of the modelled sea level rise occurred after the loss of the ice shelves, which collapsed within the first two hundred years of higher temperatures.
These findings are worrying – especially if persistent high sea surface temperatures could prompt the larger East Antarctic Ice Sheet to melt, driving global sea levels even higher. But our findings suggest the West Antarctic Ice Sheet may be close to a tipping point. Only a small temperature increase could trigger abrupt ice sheet melt and a multi-metre rise in global sea levels.
At the moment, research suggests that global sea levels could rise between 45-82cm over the next century. However, it’s thought that Antarctica will only contribute around 5cm of this – most of this sea level rise will be caused by warmer ocean waters and the melting of the Greenland Ice Sheet. But based on our findings, Antarctica’s contribution could be much greater than anticipated.
Despite 197 countries committing under the Paris agreement to restricting global warming to 2 degrees Celsius by the end of this century, our findings show that even minor increases in temperature could have far-reaching impacts.
Chris Fogwill is professor of glaciology and palaeoclimatology at Keele University; Chris Turney is professor of earth science and climate change at the ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW; and Zoë Thomas is an ARC DECRA fellow at UNSW.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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So again…what do you intend to do about it?
No! No! No! President Trump doesn’t want to hear about it. It’s a threat to his hold on power. A study by our NASA? Defund them immediately!! The Koch’s are against it!
Will the melted ice water have any impact on ocean acidity?
It happens every interglacial. Earth has been in an ice age for 2 million years. On average Earth cycles between 100,000 years of cold glacial periods which lowers atmospheric CO2 to levels that plants can barely survive at, followed by warmer interglacials of 10,000-20,000 years where CO2 levels rise in response and ice melts.
Human civilization has never experienced a glacial period and began at the current interglacial (holocene) optimum 6000 years ago , which was warmer than today. Agriculture made civilization possible. That followed the great flood due to massive glacial melting.
Homosapiens, at least those out of Africa have only survived 1 glacial period as hunter gatherers, and barely at that. In todays civilized world totally dependent on agriculture, without further preparation. 90% of the population will not survive the next glacial period, because crops don’t grow in glacial weather at low CO2.. Thats the real threat.
It’s not really about the change per se – clearly the climate has changed in the past – it’s about the *rate* of change.
The next ice age will probably gradually approach over 1000’s of years – giving humans plenty of time to adapt.
When we look back at history – K-T extinction that included the large dinosaurs for example – estimates are in the 10’s of thousands of years for how long it took – though nobody really knows.
Here – because of the enormous effect of human activity on the world – we are potentially talking decades or low hundreds of years now, and whereas humans have lots of tools to be able to adapt very quickly – the plants and animals we rely on to feed us, and regulate the environments we live in ( in ways we don’t yet understand ) don’t.
Also the conflict it will create between humans, and the awful destructive power at our disposal isn’t a good mix…
Currently we are racing at 100 mph down a foggy road which we know has a very sharp bend, and somehow hoping it will be ok.
It’s not the bend, but the speed that kills.
The real threat is caused by too much CO2, not too little. Duh!
A longtime skeptic, people like me have to be careful that we don’t close our minds to the possible. A few opportunistic persons have misled the public for years by predicting things in the near time that didn’t come to pass. That is not a good argument for deciding the environmental findings and predictions are bogus.
One concern about the focus on rising sea levels and dramatic climate change is that it can damage the movements that are based on accepted fact and that need to be addressed. Solid waste management, the creation and disposal of waste is a crises occurring right before out eyes yet it has failed to capture the Hollywood celebrities attention. Ditto energy conservation, that we can all agree on and the list of doable and discernible things that are good for the environment goes on.
That we can agree on and do if the will is there.
And a reminder when you see someone throw trash on the sidewalk, confront them and pick it up in there presence.
Wow, never heard of “temperature-sensitive water molecules” before. Sounds amazing!
The name “Doomsday Glacier”, doesn’t at all sound biased, speculative, fear-mongering or propagandistic!
I wonder why the Antarctica didn’t melt and the world didn’t end during the Medieval Warm Period.
NEWSFLASH! There were approximately 400 million humans on the planet during the 10th-13th centuries when the Medieval Warming Period was occurring, whereas now there are 7 billion+ humans living in a globally interconnected world. A cursory glimpse at the math involved here renders your scenario unworthy of discussion much less even the dignity of a reply, but here I am beating my head against the wall anyway.
It’s about a major disruption of life as we currently know it as well as death for a significant portion of the world’s population and not “the world ending” per se, so enough with the Revelations-esque hyperbole please.
“*the* Antarctica” malapropism says it all though….head back in sand please.
Because the warming was only regional, not global. Duh!
No problem with the science, but the melting was driven by natural processes during The Last Interglacial Period. Since then the climate cooled, ice returned, and then the ice began disappearing 10,000 years ago as the climate warmed. We are in the current Interglacial which began naturally. This seems an argument against fighting manandwoman made global warming since history tells us the ice is going to melt anyway.
No, history does not tell us that. Science tells us that present day global warming is caused by the burning of fossil fuels.
The Antarctic Ice is getting thinner in the West due to Volcanic activity under the Ice Sheet. The Antarctic Ice is getting thicker elsewhere.
Thank you for beginning to address climate change. This one issue eclipses almost all others. If worst-case scenario climate predictions happen, many of the other issues covered so very well by CN will not exist any more.
We have had extensive coverage of climate change for years now. Check out our archive.
Good work. This is the sort of thing that becomes more valuable when added to other work, on things like the Arctic’s melting, and the shutdown of the Atlantic Current transferring heat, and changes in tropical rain patterns. What is happening requires many teams doing many different investigations, and then someone pulling it all together.
Does this prove that Assad DID gas his own people in Douma? – Very similar sort of scientific evidence.