Arctic ice loss is worrying, but the giant stirring in the South could be even worse

Arctic ice loss is worrying, but the giant stirring in the South could be even worse
Field camp on the East Antarctic ice sheet. Credit: Nerilie Abram

A record start to summer ice melt in Greenland this year has drawn attention to the northern ice sheet. We will have to wait to see if 2019 continues to break ice-melt records, but in the rapidly warming Arctic the long-term trends of ice loss are clear.

But what about at the other icy end of the planet?

Antarctica is an icy giant compared to its northern counterpart. The water frozen in the Greenland ice sheet is equivalent to around 7 metres of potential sea level rise. In the Antarctic ice sheet there are around 58 metres of sea-level rise currently locked away.

Like Greenland, the Antarctic ice sheet is losing ice and contributing to unabated global sea level rise. But there are worrying signs Antarctica is changing faster than expected and in places previously thought to be protected from rapid change.

The threat from beneath

On the Antarctic Peninsula—the most northerly part of the Antarctic continent—air temperatures over the past century have risen faster than any other place in the Southern Hemisphere. Summer melting already happens on the Antarctic Peninsula between 25 and 80 days each year. The number of melt days will rise by at least 50 percent when global warming hits the soon-to-be-reached 1.5℃ limit set out in the Paris Agreement, with some predictions pointing to as much as a 150 percent increase in melt days.

But the main threat to the Antarctic ice sheet doesn't come from above. What threatens to truly transform this vast icy continent lies beneath, where warming waters (and the vast heat carrying capacity of seawater) have the potential to melt ice at an unprecedented rate.

Almost all (around 93 percent) of the extra heat human activities have caused to accumulate on Earth since the Industrial Revolution lies within the ocean. And a large majority of this has been taken into the depths of the Southern Ocean. It is thought that this effect could delay the start of significant warming over much of Antarctica for a century or more.

However, the Antarctic ice sheet has a weak underbelly. In some places the ice sheet sits on ground that is below sea level. This puts the ice sheet in direct contact with warm ocean waters that are very effective at melting ice and destabilising the ice sheet.

Scientists have long been worried about the potential weakness of ice in West Antarctica because of its deep interface with the ocean. This concern was flagged in the first report of the Intergovernmental Panel on Climate Change (IPCC) way back in 1990, although it was also thought that substantial ice loss from Antarctica wouldn't be seen this century. Since 1992 satellites have been monitoring the status of the Antarctic ice sheet and we now know that not only is ice loss already underway, it is also vanishing at an accelerating rate.

The latest estimates indicate that 25 percent of the West Antarctic ice sheet is now unstable, and that Antarctic ice loss has increased five-fold over the past 25 years. These are remarkable numbers, bearing in mind that more than 4 metres of global sea-level rise are locked up in the West Antarctic alone.

Arctic ice loss is worrying, but the giant stirring in the South could be even worse
Antarctic ice loss 1992–2019. Credit: European Space Agency.

Thwaites Glacier in West Antarctica is currently the focus of a major US-UK research program as there is still a lot we don't understand about how quickly ice will be lost here in the future. For example, gradual lifting of the bedrock as it responds to the lighter weight of ice (known as rebounding) could reduce contact between the ice sheet and warm and help to stabilise runaway ice loss.

On the other hand, melt water from the ice sheets is changing the structure and circulation of the Southern Ocean in a way that could bring even warmer water into contact with the base of the ice sheet, further amplifying ice loss.

There are other parts of the Antarctic ice sheet that haven't had this same intensive research, but which appear to now be stirring. The Totten Glacier, close to Australia's Casey station, is one area unexpectedly losing ice. There is a very pressing need to understand the vulnerabilities here and in other remote parts of the East Antarctic coast.

The other type of ice

Sea ice forms and floats on the surface of the polar oceans. The decline of Arctic sea ice over the past 40 years is one of the most visible impacts on Earth. But recent years have shown us that the behaviour of Antarctic sea ice is stranger and potentially more volatile.

Arctic ice loss is worrying, but the giant stirring in the South could be even worse
Antarctic sea ice extent (July-June averages)

The extent of sea ice around Antarctica has been gradually increasing for decades. This is contrary to expectations from climate simulations, and has been attributed to changes in the ocean structure and changing winds circling the Antarctic continent.

But in 2015, the amount of sea ice around Antarctica began to drop precipitously. In just 3 years Antarctica lost the same amount of sea ice the Arctic lost in 30.

So far in 2019, sea ice around Antarctica is tracking near or below the lowest levels on record from 40 years of satellite monitoring. In the long-term this trend is expected to continue, but such a dramatic drop over only a few years was not anticipated.

There is still a lot to learn about how quickly Antarctica will respond to climate change. But there are very clear signs that the icy giant is awakening and—via global sea level rise—coming to pay us all a visit.


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Warming waters in western tropical Pacific may affect West Antarctic Ice Sheet

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Jul 12, 2019
For years and years the cold winds blowing off the Antarctic continent have maintained the edge of the single year ice as the multi year ice grew thinner and thinner.
Same thing happened up north where I live but up here we ran out of multi year ice close to twenty year ago.
Established trends say a dirt coastline will surround Antarctica during summers within the next twenty years.
Opinion, yes, but based on my and the Polar Bears watching the arctic ice disappear within our lifetime.
Thicker ice just took longer to get started, makes perfect logic. Spock would approve.

Jul 13, 2019
And still no mention of the heat from underground or undersea volcanos heating the water that is melting the ice. Antarctica does have volcanos which are still active, but they are an inconvenient truth, so are seldom talked about by "climate scientists". But even climate scientists still fly in fossil-fueled airplanes to get to the Paris Convention (Paris Accords). The fossil fuels that they abhor is still much too convenient a commodity to give up entirely.

Jul 13, 2019
Because jebus will fix global warming!!!!!111!!eleventyone!!

https://www.memed...art-Deux

Unbelievable. What do these people think they're doing?

Jul 13, 2019
Because jebus will fix global warming!!!!!111!!eleventyone!!

https://www.memed...art-Deux

Unbelievable. What do these people think they're doing?
says Schneib

You still have never explained nor identified who this jebus is that you mention so often. Or is it that you prefer not to use the name of "Jesus" because of your possible fear of horrible retribution after the death of your bag of cells?
If that's the case, then your obfuscation by changing the spelling will not be your protection from the coming horrors that you so richly deserve.
Just sayin'

Jul 13, 2019
No, I'm just making fun of you and all the other dipshits who think that jebus made the universe. Or rides a unicorn. Or has lasers shooting out of his eyes. Or would ever touch a gun.

Jul 13, 2019
"In just 3 years Antarctica lost the same amount of sea ice the Arctic lost in 30."

Nothing to do with the AEB/CIA/Pentagon increasing the critical mass limit for all Plutonium on Earth ?

No no no it's CO2 storing all the heat in it's proton and heavier particle structures because of simple combustion, combustion that the Earth has been dealing with for hundreds of millions of years.
Let alone the impossibility of photon based heat getting that deep in the G space.

BAN PLUTONIUM!.

Jul 14, 2019
No, I'm just making fun of you and all the other dipshits who think that jebus made the universe. Or rides a unicorn. Or has lasers shooting out of his eyes. Or would ever touch a gun.
says Schneib

LOL You're not making fun of ME. You're making fun of those who have already condemned your filthy blackened soul to eternal pain and suffering, Schneib. Your walking bag of cells will not be saved from your fate by your evil Master, Beelzebub (Lucifer, Satan). But take heart, Schneib. The little time that you have left in a vertical position will go fast, I assure you. The event of your demise will be a cause for celebration - even your family secretly believes that.

Jul 14, 2019
Sure I'm making fun of you. Meanwhile, all you have is threats.

Sorry, I don't think jebus ever threatened anyone, either.

Jul 14, 2019
its a crisis !!!!!!!!

https://earth.nul...3.08,396

and u can check other yrs

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