Antarctic ice tipping point or irregularity

Summer sea ice in Antarctica dropped significantly last year and remains low. Scientists say time is needed (years) to determine if it is a one-off irregularity, or if a tipping point  has been passed and Antarctica is catching up with Arctic warming.

AntarcticSeaIce2017

Source: http://nsidc.org/arcticseaicenews/

2017 (blue) is similar to an unusual low on 2002 (green), both well below median.

Newshub: ‘Daunting’ Antarctic sea ice plummet could be tipping point

A dramatic drop in the amount of sea ice around Antarctica has scientists wondering if the continent has hit a tipping point.

There has been a record 30 percent decrease in the total amount of sea ice, and this summer it’s disappearing from the Ross Sea at a rate not seen in more than 30 years.

The rapidly changing conditions are having a major impact on this year’s scientific research at Scott Base, with scientists describing the changes as “unusual”, “unprecedented” and “daunting”.

One of the affected scientists is Antarctic oceanographer Dr Natalie Robinson, who studies sea ice and what lies beneath it.

“We had about 200km of sea ice to play with last year, but this year we’re down to about 25-30km, so it’s certainly a very different ball game,” she told Newshub.

The Antarctic sea ice growth in winter and melt in summer is the biggest annual change on the planet. Dr Robinson describes it as the heartbeat or pulse of Earth, and it affects everybody because it drives global weather.

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During November the sea ice edge is usually around 100km further north of where it is this year. For it to have broken out this early is a significant change and it’s causing alarms bells to ring.

“This is my 30th trip into the Southern Ocean and Antarctica,” climate scientist Professor Gary Wilson told Newshub.

“Of all the visits I’ve made down here, we haven’t seen the sea ice break out as much as it has this early.”

The sea ice is not only melting ahead of schedule, there’s a lot less of it to begin with. Last year there was 30 percent less ice – a drop of around 1 million square kilometres.

Climate scientists believe Antarctica may have hit a tipping point.

“This could be the moment that Antarctica is catching up with the Arctic,” Prof Wilson said.

Climate scientists will be watching closely over the next few years to establish whether this is a one-off event, or the moment Antarctica began to succumb to a rapidly warming planet.

A problem with monitoring the climate is it can take years to determine whether changes are normal fluctuations or signifying trends – and trends are unlikely to be smooth progressions.

Larsen C ice shelf breaks

As expected a huge iceberg has split off the Larsen C ice shelf on the Antarctica Peninsula.

The Larsen C Ice Shelf, which is between 200 and 600 metres thick, floats on the edge of The Antarctic Peninsula, holding back the flow of glaciers that feed into it.

Professor Adrian Luckman of Swansea University, lead investigator of the MIDAS project, said:

“We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice. We will continue to monitor both the impact of this calving event on the Larsen C Ice Shelf, and the fate of this huge iceberg.

The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters.

Project Midas:  Larsen C calves trillion ton iceberg

A one trillion tonne iceberg – one of the biggest ever recorded – has calved away from the Larsen C Ice Shelf in Antarctica. The calving occurred sometime between Monday 10th July and Wednesday 12th July 2017, when a 5,800 square km section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tonnes.  Its volume is twice that of Lake Erie, one of the Great Lakes.

The final breakthrough was detected in data from NASA’s Aqua MODIS satellite instrument, which images in the thermal infrared at a resolution of 1km, and confirmed by NASA’s Suomi VIIRS instrument.

NASA Suomi VIIRS panchromatic image
from July 12 2017, confirming the calving

The development of the rift over the last year was monitored using data from the European Space Agency Sentinel-1 satellites – part of the European Copernicus Space Component. Sentinel-1 is a radar imaging system capable of acquiring images regardless of cloud cover, and throughout the current winter period of polar darkness.

The iceberg weighs more than a trillion tonnes (1,000,000,000,000 metric tonnes), but it was already floating before it calved away so has no immediate impact on sea level.

Although the remaining ice shelf will continue naturally to regrow, Swansea researchers have previously shown that the new configuration is potentially less stable than it was prior to the rift.  There is a risk that Larsen C may eventually follow the example of its neighbour, Larsen B, which disintegrated in 2002 following a similar rift-induced calving event in 1995.

Dr Martin O’Leary, a Swansea University glaciologist:

“Although this is a natural event, and we’re not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position. This is the furthest back that the ice front has been in recorded history. We’re going to be watching very carefully for signs that the rest of the shelf is becoming unstable.”

This is a huge iceberg and a big event. Calving of ice shelves is a natural occurrence, but they could be influenced by warming temperatures and they could influence the effects of climate change. These things are difficult to determine accurately.

Antarctic glaciers may be melting less quickly

A study of some glaciers in Antarctica has found that they may be melting less quickly than previous studies have found.

UPI: Study suggests Antarctic glaciers are more stable than previously estimated

New research suggests ice flow among the glaciers on the southern Antarctic Peninsula isn’t as dramatic as previously estimated.

Glacial flow has increased since the 1990s, glaciologists at Leeds University found, but only a third as much as what was previously reported by scientists at the University of Bristol.

“Dramatic changes have been reported in this part of Antarctica, so we took a closer look at how its glaciers have evolved using 25 years of satellite measurements dating back to the early 1990s,” Leeds researcher Anna Hogg said in a news release.

Researchers used satellite data to track the advances of 30 different glaciers on the peninsula and found a significantly smaller rate of glacial advance and ice loss.

Bristol researchers reported significant ice loss and glacial thinning using a different set of satellite observations, but Hogg and her colleagues say their measurements don’t agree with such an interpretation.

The latest study, published this week in the journal Geophysical Research Letters, suggests most of the glaciers in the region of the Antarctic Peninsula known as Palmer Land are still moving relatively slowly and have only accelerated slightly over the last two decades.

This is how science works – more research generally moves science towards greater accuracy.

But glacial trends are complex. An acceleration may stop or reverse, or it may speed up.

A cynical post on this marred by omissions at Whale Oil: The south pole is melting at only a third of the rate “scientists” have been saying it has

“Cameron Slater” claimed:

They actually checked on the assertion made by “scientists” and found there was no basis to their inflated and scary numbers.

That’s not what the report or the scientists said at all.

I may be a layperson, but if the largest mass of ice on the planet is melting at two thirds of the rate we have been expecting, aren’t we just getting a bit ahead of ourselves predicting substantial sea level rises?

The report said “only a third as much”, but they also said “suggests most of the glaciers in the region of the Antarctic Peninsula known as Palmer Land” – that’s nothing like “the largest mass of ice on the planet”, it is just a part of the Antartic Peninsula, which itself is just a small part of Antarctica.

And “predicting substantial sea level rises” misrepresents the range of predictions that have been made about possible sea level rises.

And “Cameron Slater” omitted a key paragraph from the report:

The authors of the newest analysis say they aren’t discounting the risk of climate change and global warming’s effects on Antarctica glaciers. They say it’s essential that scientists continue to monitor the impacts of warming on glaciers and sea level rise.

Further scientific research is essential on such a complex and potentially world changing thing.

There is one certainty with climate change science – variability. The climate varies all the time. Research on climate and associated science will give us varying results. And if the planet is in fact warming there will be varying effects in different places, including different parts of Antarctica.

This will mean different rates of melting and different rates of accumulation of ice over time and in different regions.

Rubbishing past scientific research because newer research gives different results is either dumb or trying to discredit things people don’t want to hear.

All research has to be considered on it’s merits accumulatively, and if it is done well greater accuracy will be attained over time. As will better knowledge and more informed debate amongst those who want to consider all science and not just the bits that suit their agendas.

Larsen C ice shelf rift grows

It looks like the Larsen C ice shelf will break off in West Antarctica soon (in the next few months) after a sudden extension of the rift by 18 km in December, leaving just 20km holding 5000 square kilometre shelf on.

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Larsen A broke off in 1995, and Larsen B broke off in 2002.

This is what happens to ice shelves over time. There is no way of knowing if the process is being sped up by climate change or not.

RNZ: Huge iceberg poised to break off Antarctica

A long-running rift in the Larson C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5000 sq km piece from floating away.

…in December the speed of the rift went into overdrive, growing by a further 18km in just a couple of weeks. What will become a massive iceberg now hangs on to the shelf by a thread just 20km long.

“If it doesn’t go in the next few months, I’ll be amazed,” project leader Prof Adrian Luckman, from Swansea University, told BBC News.

While very interesting this isn’t abnormal.

NZ Antarctic Research Institute director Gary Wilson said this was a fairly normal process for ice shelves to carve off when they came into enough interaction with storm swells.

He said the questions would be whether it would cause warmer water to get further under the ice shelf, and whether it would allow the storm swells to break up further back.

Larsen C is about 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.

As it floats on the sea, the resulting iceberg from the shelf will not raise sea levels. But if the shelf breaks up even more, it could result in glaciers that flow off the land behind it to speed up their passage towards the ocean. This non-floating ice would have an impact on sea levels.

According to estimates, if all the ice that the Larsen C shelf currently holds back entered the sea, global waters would rise by 10cm.

That’s likely to be a long term thing, if it happens. Sea levels have risen since the last ice age.

post-glacial_sea_level

What has changed recently is the huge increase in population and the establishment of settlements in low lying areas.