The 2024 Antarctic Freezing Season

[I’M IN LOVE WITH A RAGER]

Per discussion in the melting season thread, here is the new freezing discussion page since Antarctic sea ice is off to the races for the refreeze. I’m personally very interested whether the initial recovery momentum holds on, or if these sort of bursts post-minimum are more a function of greater areas of cooling open water in pole-proximal seas. I’m also hoping that we might get some publications sooner than later providing insight into some of the recent melt season action down south.

[kiwichick16]

current sea ice....

https://climatereanalyzer.org/clim/seaice/

[gerontocrat]

Per discussion in the melting season thread, here is the new freezing discussion page since Antarctic sea ice is off to the races for the refreeze. I’m personally very interested whether the initial recovery momentum holds on, or if these sort of bursts post-minimum are more a function of greater areas of cooling open water in pole-proximal seas. I’m also hoping that we might get some publications sooner than later providing insight into some of the recent melt season action down south.

A large proportion of Antarctic sea ice gains comes from the Ross Sea. At the moment looks like it may be more than "a function of greater areas of cooling open water in pole-proximal seas".

[oren]

Thanks for starting the thread.

[VeliAlbertKallio]

All-time heat record at French Antarctic territories: https://x.com/extremetemps/status/1776363251195892051

[kassy]

In the Crozet islands which are sort of halfway between Antarctica and Madagascar.

[Stephan]

...which might therefore better be transferred into the "heat wave" or "extreme temperatures" thread ?

[oren]

Too difficult to move posts across moderator jurisdictions. Will leave it be, but to all please avoid off topic posts.

[gerontocrat]

Maybe there is a correlation between Antarctic SATs and Antarctic sea ice area daily gains (and losses)

The graph attached roughly matches Antarctic SATs (2023 and 2024 (black)) to Antarctic sea ice area gains for the period late April to mid July - click to enlarge

Maybe I'll think about extracting the numbers for the two variables

[kassy]

The gains are now low for a number of days. Are the seas around Antarctica relatively hot? Transpolar winds slacking? Something else?

[gerontocrat]

The gains are now low for a number of days. Are the seas around Antarctica relatively hot? Transpolar winds slacking? Something else?

Not a clue... but at the moment looks like maximum area and extent could be heading to be in the bottom 5 of the 46 year satellite record.

I thought high circumpolar winds tend to bring warmth closer to the Antarctic shoreline.

Antarctic (66.5 to 90 South) SATs are quite high (as at 29th May)
Offshore there are quite high +ve SAT anomalies (as at 3rd June) in the Ross, Indian Ocean and Amundsen regions where sea ice area is reducing.

Todays one-day NSIDC area and extent graphs show that both are currently more than 2SD below the 2000-2019 average.

click images to enlarge

[uniquorn]

https://det.social/@ZLabe@fediscience.org/112716707123778301

SIC anomaly jun

Last month observed substantial departures in #Antarctic sea ice, which were particularly focused around the Indian Ocean sector and near the Ross/Amundsen Seas. This is a different spatial pattern compared to last year.

[kassy]

Looking back at the recent past.

The “climatic surprise” in Rio Grande do Sul was likely influenced by another phenomenon (and this one is indeed unprecedented): the anomalous behavior of the South Atlantic anticyclone. This system, a large circle of winds that move in a counterclockwise direction, underwent a radical change beginning in 2023 (Figure 6). The South Atlantic anticyclone index remained at a practically constant level over the 43-year period from 1979 to 2022, after which it has oscillated radically. This anticyclone circles around the South Atlantic high-pressure cell.

And see figure 6.

https://news.mongabay.com/2024/07/climate-surprises-amazonia-and-the-lessons-of-brazils-catastrophic-flood-in-rio-grande-do-sul-commentary/

I guess lot´s of ice had to melt to trigger this? Or is it something else? It did not quite settle.

[Yuha]

Gero is reporting on significant sea ice losses in the Indian Ocean and West Pacific regions:
https://forum.arctic-sea-ice.net/index.php/topic,1759.msg405939.html#msg405939

This is probably caused by the stratospheric warming event over those regions that HapHazard mentioned a few days ago:
https://forum.arctic-sea-ice.net/index.php/topic,520.msg405642.html#msg405642

[gerontocrat]

Images attached seem to show a correlation between sea ice change and SATs

[kassy]

Quite a strong recovery. Probably in those regions/seas. Admundsen and Ross have last changes over last week then the other seas?

[gerontocrat]

A strong recovery in JAXA sea ice extent in the last 3 days, due to extreme cold in the Ross Sea and especailly the Weddell Sea, while most of the Antarctic continent basks in a heatwave.

More about it later

[gerontocrat]

And so it continues...

Overall Antarctic SATs (south of the Antarctic Circle) are at record highs, but mostly over the Antarctic continent.

Meanwhile, a very large, very cold blob lies over the Weddell Sea and well into lower latitudes. As the Weddell Sea is the largest of the regional seas, the resulting recent high sea ice area and extent gains in the Wedell Sea have driven above average gains in the Antarctic ocean.

[Phil.]

Although it looks like that warmer air is moving towards the Weddell sea.

[gerontocrat]

Although it looks like that warmer air is moving towards the Weddell sea.

The attached gif of the GFS forecast shows that over the next week or so while some warmer air slowly enters the western edge of the Weddell Sea, most of the air over sea remains cold to very cold, with the coldness extending even further north into lower latitudes.

The gif also shows that SATS over much of the Ross Sea remain very cold.

It still seems probable that sea ice area gains in the Weddell Sea are likely to dominate overall sea ice gain in the Antarctic for the next week or so.

click gif to start, runs 10 times

[gerontocrat]

Antarctic sea ice area graphs attached post 1 of 2

[gerontocrat]

Antarctic sea ice area graphs attached post 2 of 2

[kassy]

Something’s Going On With The Polar Vortex, And It Could Have Consequences

The southern polar vortex is currently showing rare signs of extreme instability, leading to fears that it could collapse, bringing both icy blasts and extreme heatwaves to the southern hemisphere. Likewise, the northern polar vortex had yet another wild winter this year, and with climate change set to intensify these perilous polar patterns, we could be in for some increasingly dramatic weather in the years to come.

The polar vortices are strong stratospheric air currents that circulate over the Arctic and Antarctic during the winter months, trapping cold air above the poles. They are surrounded and enclosed by the jet streams, which act like barriers that prevent this icy polar air from spreading into the mid-latitudes.

However, every now and then, the stratosphere above the Arctic experiences a dramatic increase in temperature and pressure, destabilizing the northern polar vortex and causing it to split, change direction or collapse. When this occurs, the jet stream tends to become warped, allowing icy Arctic winds to encroach further south than they usually would, while warm air is drawn into the polar region.

Known as sudden stratospheric warming (SSW), this phenomenon caused the big freeze that gripped parts of the US in 2019. In early 2024, fluctuations in stratospheric pressure caused the northern polar vortex to change direction twice, bringing cold snaps to the northern hemisphere, although neither event was strong enough to significantly alter the shape of the jet stream.

Down in Antarctica, however, SSWs are much less common, with the only known instance occurring in 2002. Yet that could be about to change, with a series of stratospheric temperature increases since last month raising fears that the southern polar vortex could be about to split.

The first of these was detected in mid-July, when wind speeds in the vortex slowed from their typical velocity of 300 kilometers per hour to just 230 kilometers per hour (186 to 143 miles per hour). This was accompanied by a temperature spike of about 20 degrees Celsius (36 Fahrenheit) above the average.

While these fluctuations were insufficient to trigger an SSW, they were followed by a second slowdown as temperatures rose once again in early August. This event has resulted in cold Antarctic air escaping from the polar region and blasting parts of Australia, New Zealand, and South America with wet and icy weather.

At the same time, warm air from the mid-latitudes has been able to push south into Antarctica, triggering a record-breaking heatwave.

It’s currently unclear how the situation will play out, with some predictions suggesting the southern polar vortex may soon stabilize, while other models hint at a drastic collapse. In the latter scenario, a destabilized jet stream will most likely disrupt another weather system called the southern annular mode, sending it into what’s known as a negative phase.

This would then result in an exceptionally dry and hot summer across Australasia and South America.

...

https://www.iflscience.com/somethings-going-on-with-the-polar-vortex-and-it-could-have-consequences-75509

From the vortex thread.

Quoted in there:

Huge chunks of Antarctica have recently been slapped with (potentially) record-breaking warm temperatures that have lingered for a worryingly long time.

New data from the European Union’s Copernicus Climate Change Service shows that large parts of the ice-covered continent experienced temperatures that were 10 to 12°C (18 to 21.6°F) above average for this time of year in late July 2024, compared to the 1991-2020 reference period.

Provisional data from the Syowa station and Halley station also suggests they may have broken their previous temperature records for July/August, while some days in East Antarctica showed temperatures that were 25°C (45°F) above average.

These anomalies sound shocking, but it’s the length and scale of the heat that’s concerning scientists.

“In Antarctica, it's unsurprising to have a day at some point in the winter (roughly June to August) where the temperature reaches ~25°C [45°F] above normal for the time of year somewhere on the continent. What is remarkable is prolonged high temperatures occurring over a large sector of east Antarctica from the second half of July and into early August, combined with warm surface temperatures offshore," Thomas Caton Harrison, Polar Climate Scientist at British Antarctic Survey (BAS), told IFLScience.

“The main feature of interest is currently not so much the magnitude of the anomalies, though that may change. It's the fact we have seen prolonged warmer than usual conditions over this large sector, making July 2024 a standout month in the long-term average for this sector of east Antarctica,” he added.

...

https://www.iflscience.com/antarctica-is-being-hit-with-a-worryingly-long-heat-wave-potentially-breaking-records-75459

[gerontocrat]

Something’s Going On With The Polar Vortex, And It Could Have Consequences

The southern polar vortex is currently showing rare signs of extreme instability, leading to fears that it could collapse, bringing both icy blasts and extreme heatwaves to the southern hemisphere.

There seem to be consequences.

In August sea ice extent area and extent gains in the Weddell Sea, (and to a lesser extent in the Ross Sea), have been extremely high as well below average SATs spread North. The 1st image attached suggests that this will continue at least for the next few days.

The 2nd image shows how 2 large low pressure systems, one over the Weddell Sea, the other over the Ross Sea, that seem to provide the escape route for Antarctic cold to move North. I don't remeber seeing such a map before in the last 5 years or so.

One consequence is high sea ice gains in the Weddell Sea especially.

Speculation
Is this a rare weather event whose consequences will fade away after some time, or is something happening to the climate system?

A series of weather events that produces climate data that is outside the boundaries assumed in climate models does bring the climate models into question. Over the last few years the Antarctic has produced more than its fair share of these events.

[kassy]

If it reoccurs then it is not that rare. Time shall tell.

[gerontocrat]

If it reoccurs then it is not that rare. Time shall tell.

When extreme events that were rare become less rare, yet another indication all is not well with the climate system, and the climate models?

[kassy]

That is the idea. But we have very little data. If you look at SSW events that is two. If you look at the record ice loss we still don´t know if it recovers or stays low. I would bet there will be more because we have circumstantial evidence. AABW formation declining since the seventies. Huge melt  on the underside of glaciers etc. A lot of warmth has been going there already.

So yes the system is in trouble (high confidence etc) but we can´t predict things like the future frequency of SSWs there or what happens with extent and area.

[uniquorn]

https://det.social/@ZLabe@fediscience.org/113073826792841733

The very large sea ice concentration departures continue across the Indian Ocean sector of the #Antarctic. Overall mean ice extent remains well below average too.

[gerontocrat]

It has been a very odd winter in Antarctica - at all levels.

The weirdness of the temps and winds in the stratosphere in August may have had much to do with the very cold surface air temperatures mainly in the Ross and Weddell Seas during much of August.

https://earthobservatory.nasa.gov/images/153258/a-series-of-rare-disturbances-in-the-stratosphere

A Series of Rare Disturbances in the Stratosphere


It’s been an unsettled winter in the atmosphere above Antarctica. About 30 kilometers above the continent’s icy surface, in the layer known as the stratosphere, a series of warming events took place starting in July 2024.

July temperatures in the stratosphere above Antarctica are typically around minus 80 degrees Celsius (minus 112 degrees Fahrenheit). On July 7, temperatures in the middle of the stratosphere jumped 15°C (27°F), setting a record for the warmest July temperatures observed in the stratosphere in the Antarctic region. The temperature then cooled off on July 22 before rising 17°C (31°F) on August 5.

These sudden stratospheric warming events surprised Lawrence Coy and Paul Newman, atmospheric scientists at NASA’s Goddard Space Flight Center. Coy and Newman develop complex data assimilation and reanalysis models of Earth’s atmosphere for NASA’s Global Modeling and Assimilation Office (GMAO). “The July event was the earliest stratospheric warming ever observed in GMAO’s entire 44-year record,” Coy said.

Westerly winds in this layer of the atmosphere loop around the South Pole in winter, moving about 300 kilometers (200 miles) per hour, forming what is known as the polar vortex. But sometimes something happens that disrupts this symmetric circumpolar flow, causing winds to weaken and the flow to change shape. Instead of circulating the South Pole, the polar vortex becomes elongated and winds weaken; the weakening winds result in considerable stratospheric warming over Antarctica.

The maps above (see 1st image) show air temperatures in the middle stratosphere (at about 30 kilometers altitude or 10 hectopascals of pressure) for August 5, 2023 (left) and August 5, 2024 (right). The elongation of the polar vortex and higher temperatures closer to the pole are evident in the 2024 map. Data for the maps are from NASA’s GEOS forward processing (GEOS-FP) model, which assimilates meteorological data from satellite, aircraft, and ground-based observing systems.

The map below (see 2nd image) shows potential vorticity—a quantity that describes how air masses are spinning—in the stratosphere on August 5, 2024. Areas of high potential vorticity appear yellow and have a clockwise circulation; areas of low potential vorticity appear purple and have a counterclockwise circulation. The polar vortex had elongated and weakened, and the flow of wind was shaped like a peanut instead of its usual circular pattern.

Unlike in the Arctic, which experiences sudden stratospheric warming events about once a year, the polar vortex in the Southern Hemisphere is typically much less active. “Sudden warming events happen in the Antarctic once every five years or so, much less frequently than the Arctic,” Coy said. The reason for this, Coy added, is likely that there is more terrain in the Northern Hemisphere that can disrupt wind flow in the troposphere—the layer of air closest to the ground. These large-scale tropospheric weather systems move upward into the stratosphere and disrupt the polar vortex.

[kassy]

That lines up nicely with the areas missing ice.

[johnm33]

That lines up nicely with the areas missing ice.

Except that it rotates, if time allows I'll make an animation to find the period.

[Iceburn]

Think freezing season will extend a couple more weeks in Antartica this year bringing extent up to 17.5m.