How Antarctic ice melt can be a tipping point for the whole planet’s climate


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Melting Antarctic ice can trigger effects on the other side of the globe.
NASA/Jane Peterson

Chris Turney, UNSW; Jonathan Palmer, UNSW; Peter Kershaw, Monash University; Steven Phipps, University of Tasmania, and Zoë Thomas, UNSW

Melting of Antarctica’s ice can trigger rapid warming on the other side of the planet, according to our new research which details how just such an abrupt climate event happened 30,000 years ago, in which the North Atlantic region warmed dramatically.

This idea of “tipping points” in Earth’s system has had something of a bad rap ever since the 2004 blockbuster The Day After Tomorrow purportedly showed how melting polar ice can trigger all manner of global changes.

But while the movie certainly exaggerated the speed and severity of abrupt climate change, we do know that many natural systems are vulnerable to being pushed into different modes of operation. The melting of Greenland’s ice sheet, the retreat of Arctic summer sea ice, and the collapse of the global ocean circulation are all examples of potential vulnerability in a future, warmer world.


Read more: Chasing ice: how ice cores shape our understanding of ancient climate.


Of course it is notoriously hard to predict when and where elements of Earth’s system will abruptly tip into a different state. A key limitation is that historical climate records are often too short to test the skill of our computer models used to predict future environmental change, hampering our ability to plan for potential abrupt changes.

Fortunately, however, nature preserves a wealth of evidence in the landscape that allows us to understand how longer time-scale shifts can happen.

Core values

One of the most important sources of information on past climate tipping points are the kilometre-long cores of ice drilled from the Greenland and Antarctic ice sheets, which preserve exquisitely detailed information stretching back up to 800,000 years.

The Greenland ice cores record massive, millennial-scale swings in temperature that have occurred across the North Atlantic region over the past 90,000 years. The scale of these swings is staggering: in some cases temperatures rose by 16℃ in just a few decades or even years.

Twenty-five of these major so-called Dansgaard–Oeschger (D-O) warming events have been identified. These abrupt swings in temperature happened too quickly to have been caused by Earth’s slowly changing orbit around the Sun. Fascinatingly, when ice cores from Antarctica are compared with those from Greenland, we see a “seesaw” relationship: when it warms in the north, the south cools, and vice versa.

Attempts to explain the cause of this bipolar seesaw have traditionally focused on the North Atlantic region, and include melting ice sheets, changes in ocean circulation or wind patterns.

But as our new research shows, these might not be the only cause of D-O events.

Our new paper, published today in Nature Communications, suggests that another mechanism, with its origins in Antarctica, has also contributed to these rapid seesaws in global temperature.

Tree of knowledge

The 30,000-year-old key to climate secrets.
Chris Turney, Author provided

We know that there have been major collapses of the Antarctic ice sheet in the past, raising the possibility that these may have tipped one or more parts of the Earth system into a different state. To investigate this idea, we analysed an ancient New Zealand kauri tree that was extracted from a peat swamp near Dargaville, Northland, and which lived between 29,000 and 31,000 years ago.

Through accurate dating, we know that this tree lived through a short D-O event, during which (as explained above) temperatures in the Northern Hemisphere would have risen. Importantly, the unique pattern of atmospheric radioactive carbon (or carbon-14) found in the tree rings allowed us to identify similar changes preserved in climate records from ocean and ice cores (the latter using beryllium-10, an isotope formed by similar processes to carbon-14). This tree thus allows us to compare directly what the climate was doing during a D-O event beyond the polar regions, providing a global picture.

The extraordinary thing we discovered is that the warm D-O event coincided with a 400-year period of surface cooling in the south and a major retreat of Antarctic ice.

When we searched through other climate records for more information about what was happening at the time, we found no evidence of a change in ocean circulation. Instead we found a collapse in the rain-bearing Pacific trade winds over tropical northeast Australia that was coincident with the 400-year southern cooling.


Read more: Two centuries of continuous volcanic eruption may have triggered the end of the ice age.


To explore how melting Antarctic ice might cause such dramatic change in the global climate, we used a climate model to simulate the release of large volumes of freshwater into the Southern Ocean. The model simulations all showed the same response, in agreement with our climate reconstructions: regardless of the amount of freshwater released into the Southern Ocean, the surface waters of the tropical Pacific nevertheless warmed, causing changes to wind patterns that in turn triggered the North Atlantic to warm too.

The ConversationFuture work is now focusing on what caused the Antarctic ice sheets to retreat so dramatically. Regardless of how it happened, it looks like melting ice in the south can drive abrupt global change, something of which we should be aware in a future warmer world.

Chris Turney, Professor of Earth Sciences and Climate Change, UNSW; Jonathan Palmer, Research Fellow, School of Biological, Earth and Environmental Sciences., UNSW; Peter Kershaw, Emeritus Professor, Earth, Atmosphere and Environment, Monash University; Steven Phipps, Palaeo Ice Sheet Modeller, University of Tasmania, and Zoë Thomas, Research Associate, UNSW

This article was originally published on The Conversation. Read the original article.

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Article: Japan – Nuclear Threat at Fukushima Contained


The following link is to an article reporting on the latest at the Fukushima Daiichi Nuclear Power Plant in Japan, following the 2011 earthquake and tsunami. The situation is said to be contained, however this would seem to be only to a certain point.

For more visit:
http://www.reuters.com/article/2012/05/26/us-japan-nuclear-idUSBRE84P0DQ20120526

Bison to Enjoy Increased Protection at Yellowstone


Having been driven to near the point of extinction, Bison have been making a come back in the United States. The article that follows deals with an increase in protected lands for migrating Bison from Yellowstone National Park, providing more good news for a species that was almost lost.

For more visit:
http://www.defendersblog.org/2011/04/big-win-for-bison/#1

Destination: Back Packing Holiday


I have pretty much determined that my holiday is going to be a back packing trip through the wilderness along the ‘Tops to Myall’s Heritage Trail.’ Now I need to decide on just what part of the trail I’ll do, if indeed not all of it.

One of the determining factors for the trip will be the availability of transport. I would need to get to the Barrington Guesthouse in order to start the walk if doing the whole walk, or either get home from the Gloucester area or to the Gloucester area to start the walk. The start from near Gloucester wouldn’t be an issue – that would be fairly easy to solve with Countrylink and family I think (combo). I’m not sure about the Guesthouse option just yet, but looking into it a little. I could easily walk from where I live to the Gloucester area (and for that matter do a return walk if necessary – though I’d prefer to not do so). I also think that Countrylink could easily drop me off near the start of the walk up that way (along the Buckets Way) should that be necessary.

The most likely outcome is that I’ll travel to Gloucester with Countrylink and then get a lift to the walk starting point from my family the next day. I could try getting a lift to the guesthouse with the family also, but that is unlikely to be an option I would think.