Category Archives: Antarctic

New Record Antarctic Sea Ice Minimum Extent

Antarctic, , , , , , , , , , , , ,

I should of course add “in the satellite era”, but the title is pretty unwieldy as it is!

I was up early (UTC) to check the latest JAXA data, and sure enough that confirmed a new record minimum Antarctic sea ice extent of 2.11 million km² was reached yesterday:

Having added a note to that effect the Arctic open thread, Lars Kaleschke from the Alfred Wegener Institute pointed out over on Mastodon that the AWI had published a press release about the event this morning:

Let’s take a closer look at what the AWI had to say:

On 8 February 2023, at 2.20 million square kilometres, the Antarctic sea ice extent had already dropped below the previous record minimum from 2022 (2.27 million square kilometres on 24 February 2022). Since the sea ice melting in the Antarctic will most likely continue in the second half of the month, we can’t say yet when the record low will be reached or how much more sea ice will melt between now and then,” says Prof Christian Haas, Head of the Sea Ice Physics Section at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), with regard to the current developments in the Antarctic. “The rapid decline in sea ice over the past six years is quite remarkable, since the ice cover hardly changed at all in the thirty-five years before. It is still unclear whether what we are seeing is the beginning of a rapid end to summer sea ice in the Antarctic, or if it is merely the beginning of a new phase characterised by low but still stable sea ice cover in the summer.”

Here’s how that news looks in the AWI’s official press release:

and here’s how it looks in Lars’ experimental AMSR2 graphic, with current minimum at 1.97 million km²:

By way of prognostication here too is the current JAXA AMSR2 concentration map:

There are some low concentration areas which suggest further extent reductions still to come, despite the recent uptick in the high resolution graph.

Getting back to the AWI’s text:

The melting has progressed since December 2022, especially in the Bellingshausen and Amundsen Seas in the West Antarctic; the former is virtually ice-free. That is also where the research vessel Polarstern currently is, exploring the evidence left behind of past glacials and interglacials. According to expedition leader and AWI geophysicist Prof Karsten Gohl, who is now in the region for the seventh time, having first come in 1994: “I have never seen such an extreme, ice-free situation here before. The continental shelf, an area the size of Germany, is now completely ice-free. Though these conditions are advantageous for our vessel-based fieldwork, it is still troubling to consider how quickly this change has taken place.”

Polarstern in ice free Bellingshausen Sea, West Antarctica, in January 2023. (Photo: Daniela Röhnert)

Analyses of the current sea ice extent, conducted by the Sea Ice Portal team, show that, for the entire month of January 2023, the ice was at its lowest-ever extent recorded for the time of year since the beginning of record-keeping in 1979. The monthly mean value was 3.22 million square kilometres, ca. 478,000 square kilometres (an area roughly the size of Sweden) below the previous minimum from 2017. With regard to its long-term development, the Antarctic sea ice shows a declining trend of 2.6 percent per decade. This is the eighth consecutive year in which the mean sea-ice extent in January has been below the long-term trend.

But what has caused the current lack of Antipodean sea ice? The press release continues:

This intense melting could be due to unusually high air temperatures to the west and east of the Antarctic Peninsula, which were ca. 1.5 °C above the long-term average. In addition, the Southern Annular Mode (SAM) is in a strongly positive phase, which influences the prevailing wind circulation in the Antarctic. In a positive SAM phase (like today), a low-pressure anomaly forms over the Antarctic, while a high-pressure anomaly develops over the middle latitudes. This intensifies the westerly winds and causes them to contract toward the Antarctic. As a result, upwelling of circumpolar deep water on the continental shelf intensifies in the Antarctic, promoting sea-ice retreat. More importantly, it also intensifies the melting of ice shelves, an essential aspect for future global sea-level rise.

Air temperature anomalies in °C at 925 hPa pressure level in Antarctica in January 2023 compared to the long-term mean 1971-2000. (Graphic: meereisportal.de)

The press release concludes:

Historical records also reflect the tremendous changes. For example, in the Antarctic summer 125 years ago, the Belgian research vessel Belgica was trapped in the massive pack ice for more than a year – in exactly the same region where the Polarstern can now operate in completely ice-free waters. The photographs and diaries of the Belgica’s crew offer a unique chronicle of the ice conditions in the Bellingshausen Sea at the dawn of the industrial age, which climate researchers often use as a benchmark for comparison with today’s climate change.

Belgica became ice bound near Peter I island on February 28th 1898. On board was second officer Roald Amundsen. The leader of the expedition, Adrien de Gerlache, published a French language book about the voyage in 1902: “Quinze mois en Antarctique“.

Belgica ice bound in the Bellingshausen Sea

Finally, for the moment at least, here is the University of Bremen’s map of Polarstern’s current location and the sea ice concentration in the vicinity thereof:

[Edit – February 11th]

JAXA Antarctic sea ice extent is now down to 2.06 million km². Accompanied by a significant fall in Arctic extent, JAXA’s flavour of global sea ice extent has now also reached the lowest level ever recorded in the satellite era, at 15.51 million km² :

P.S. The NSIDC’s 5 day averaged extent hasn’t quite reached a record minimum yet:

However their daily extent has reached a new satellite era record minimum:

[Edit – February 14th]

The NSIDC’s 5 day average Antarctic sea ice extent metric has duly reached a new record low level of 1.91 million km² :

P.S. The NSIDC has now published its own article about the record minimum:

With a couple more weeks likely left in the melt season, the extent is expected to drop further before reaching its annual minimum. Much of the Antarctic coast is ice free, exposing the ice shelves that fringe the ice sheet to wave action and warmer conditions…

Extent has tracked well below last year’s melt season levels since mid-December. As noted in our previous post, a positive Southern Annular Mode has led to stronger-than-average westerly winds. Along with a strong Amundsen Sea Low, the weather conditions have brought warm air to the region on both sides of the Antarctic Peninsula. This has largely cleared out the ice cover in the Amundsen and Bellingshausen Seas, and reduced the sea ice extent in the northwestern Weddell Sea. Sea ice is patchy and nearly absent over a long stretch of the Pacific-facing coastline of Antarctica.  Earlier studies have linked low sea ice cover with wave-induced stresses on the floating ice shelves that hem the continent, leading to break up of weaker areas.

Antarctic sea ice extent has been highly variable over the last several years. While 2022 and 2023 have had record low minimum extent, four out of the five highest minimums have occurred since 2008. Overall, the trend in Antarctic minimum extent over 1979 to 2023 is near zero. The current downward linear trend in the Antarctic minimum extent from 1979 to 2023 is 2,400 square kilometers per year, or 0.9 percent per decade, which is currently not statistically significant. Nevertheless, the sharp decline in sea ice extent since 2016 has fueled research on potential causes and whether sea ice loss in the Southern Hemisphere is developing a significant downward trend.

Watch this space!

Thwaites Ice Shelf “within years of failure”?

Antarctic, , , , , , , ,

There have been a plethora of headlines in the last 24 hours along the lines outlined above!

According to an article on Science.org the answer to the question posed above seems to be “yes”:

An alarming crackup has begun at the foot of Antarctica’s vulnerable Thwaites Glacier, whose meltwater is already responsible for about 4% of global sea level rise. An ice sheet the size of Florida, Thwaites ends its slide into the ocean as a floating ledge of ice 45 kilometers wide. But now, this ice shelf, riven by newly detected fissures on its surface and underside, is likely to break apart in the next 5 years or so, scientists reported today at a meeting of the American Geophysical Union.

The most dramatic sign of impending failure is a set of diagonal fractures that nearly span the entire shelf. Last month, satellites spotted accelerating movement of ice along the fractures, says Erin Pettit, a glaciologist at Oregon State University, Corvallis, who is part of a multiyear expedition studying the glacier. The shelf is a bit like a windshield with a series of slowly opening cracks, she says. “You’re like, I should get a new windshield. And one day, bang—there are a million other cracks there.”

Here’s an image from the AGU abstract to illustrate the “cracks” Erin referred to:

Image: Christian Wild, Oregon State University

Once the ice shelf shatters, large sections of the glacier now restrained by it are likely to speed up, says Ted Scambos, a glaciologist at the University of Colorado, Boulder, and a leader of the Thwaites expedition. In a worst case, this part of Thwaites could triple in speed, increasing the glacier’s contribution to global sea level in the short term to 5%, Pettit says.

Here is the AGU press conference that caused all the excitement:




Pine Island Glacier Calves Again

Antarctic, , , ,

An image captured earlier this morning by the Sentinel 1A satellite’s synthetic aperture radar reveals that another huge chunk of the Pine Island Glacier in Antarctica has broken loose:

S1A_PIG_20170923T035511

P.S. Here’s an animation of the calving courtesy of Wipneus:

Pine_Island_Glacier_Sentinel_1A_20170911-20170923

Via Stef Lhermitte on Twitter:

 

[Edit – September 24th]

The latest image from Sentinel 1A:

S1A_IPIG_20170924T043546

Click it for a much closer look.

 

[Edit – October 16th]

Another animation from Wipneus, showing the recently calved section of the Pine Island Glacier coming apart at the seams:

Pine_Island_Glacier_Sentinel_Calving_Crumbles_1A_20171003-20171015

 

[Edit – December 11th]

Another revealing image from Wipneus via the Arctic Sea Ice Forum:

Pine-Island-Glacier-SW-crack-Landsat8-nat-30m-20171210

New cracks are opening on the Pine Island Ice Shelf.

 

[Edit – December 22nd]

Via Susan Anderson at the Arctic Sea Ice Forum:

Pine Island Iceberg Under the Midnight Sun
“Pine Island Iceberg Under the Midnight Sun“

In September 2017, a new iceberg calved from Pine Island Glacier—one of the main outlets where the West Antarctic Ice Sheet flows into the ocean. Just weeks later, the berg named B-44 shattered into more than 20 fragments.

On December 15, 2017, the Operational Land Imager (OLI) on Landsat 8 acquired this natural-color image of the broken berg. An area of relatively warm water, known as a polyna, has kept the water ice free between the iceberg chunks and the glacier front. NASA glaciologist Chris Shuman thinks the polynya’s warm water could have caused the rapid breakup of B-44.

The image was acquired near midnight local time. Based on parameters including the azimuth of the Sun and its elevation above the horizon, as well as the length of the shadows, Shuman has estimated that the iceberg rises about 49 meters above the water line. That would put the total thickness of the berg—above and below the water surface—at about 315 meters.

 

[Edit – December 23rd]

Another graphic Landsat PIG GIF from Wipneus on the ASIF:

Pine-Island-Glacier_SW-crack_growing_landsat-8_20171219

The 2017 Antarctic Sea Ice Minimum Extent

Antarctic, , , , ,

In 2017 Antarctic sea ice extent is beating all the records. All flavours of the metric are already below the minimum of all previous years in the satellite record, and it looks like there’s still some more melting left to go. Here’s the NSIDC’s 5 day averaged extent:

Chantarctic-20170226

and here’s JAXA’s 2 day averaged version:

JAXA-antarctic-feb27-2017

Finally, for the moment at least, here’s the current map of Antarctic sea ice concentration from the University of Bremen:

Bremen_Antarctic_AMSR2_20170227

 

[Edit – March 12th]

It seems highly likely that the 2017 Antarctic sea ice minimum extent has now been reached. Here’s the NSIDC 5 day averaged extent graph:

Chantarctic-20170311

The minimum extent of 2.106 million square kilometers was reached on March 3rd. Here’s the University of Bremen’s Antarctic sea ice concentration map for March 3rd:

asi-AMSR2-s6250-20170303

New Antarctic Sea Ice Resources

Antarctic, , , , , , , , , , , , , , ,

In the Arctic the refreeze is slowing down as the March maximum extent approaches. Meanwhile in the southern hemisphere Antarctic sea ice extent has taken a tumble as the annual minimum extent approaches.

Over the long cold Arctic winter “Wipneus” of ArctischePinguin fame has been porting his northern hemisphere regional sea ice area/extent methodology to cover the South Pole as well. We are pleased to be able to reveal the fruits of his labours on our new regional Antarctic Sea Ice Graphs page. The ultimate source of the information is the University of Hamburg’s sea ice concentration data based on a 3.125 km grid that uses data from the from the AMSR2  instrument on board the Japan Aerospace Exploration Agency’s SHIZUKU satellite. Here’s an overview of Antarctic sea ice area:

2015-02-07-Ant-Area and here’s a close up on the sea ice extent in the Bellingshausen and Amundsen Seas region, where what sea ice there is helps buttress the West Antarctic Ice Sheet:

2015-02-07-West-Extent

In future we will also be bringing you satellite images from Antarctica. By way of example, here’s the latest “Shock News!!!” from the Antarctic, courtesy of LandSat 8:

I
NASA report that:

While large icebergs calve regularly from fast-flowing ice shelves in West Antarctica, the coast of cooler, drier East Antarctica tends to be less active. That made it a mild surprise when a 70-square-kilometer chunk of ice broke off from the King Baudouin Ice Shelf in January 2015. The last time that part of King Baudouin calved such a large iceberg was in the 1960s.

and you can track the current position of the latest large chunk of ex ice shelf on their WorldView web site:

The recently calved King Baudouin Ice Shelf on February 3rd 2015
The recently calved King Baudouin Ice Shelf on February 3rd 2015

Thanks also to “Arcticio” from the Arctic Sea Ice Blog who pointed me in the direction of PolarView, where it was remarkably easy to locate this Sentinel-1A synthetic aperture radar image of the large iceberg in question on January 30th 2015:

RoiBaudouin-600