Antarctic Ice Discussion

[joggs]

How's it looking down bottom of our planet?

Anyone? 

[Relativistic]

9 hours ago, joggs said:

How's it looking down bottom of our planet?

Anyone? 

Extent is running very close to the 2000s average currently, and above the 1980s and 1990s averages.

Select "Antarctic" in the region selector on the following web page:
https://ads.nipr.ac.jp/vishop/#/extent

[knocker]

 

[John Badrick]

[knocker]

22 minutes ago, John Badrick said:

I think you will find that this new study was 'discussed' in the thread at the end of last year.

https://www.netweather.tv/forum/topic/64332-antarctic-ice-discussion/?page=64

Shortcut

http://www.realclimate.org/index.php/archives/2015/11/so-what-is-really-happening-in-antarctica/#sthash.RzSrewzh.dpuf

Edited July 25, 2016 by knocker

[BornFromTheVoid]

The rift in the Larsen C shelf continues to grow

A growing rift on Larsen C

For almost two years now, we have been tracking the progress of a large rift in the Larsen C Ice Shelf. This rift, which may threaten the stability of Larsen C, has grown significantly and rapidly during the Antarctic polar night, which is now coming to an end. As of August 2016, the rift is now 22km longer than when satellites were last able to observe it in March of this year.

More here: http://www.projectmidas.org/blog/a-growing-rift-in-larsen-c/

[iapennell]

Currently Antarctic sea-ice extent is close to the long-term norm for August (winter in Southern Hemisphere) and looking at the trend looks like it might be slightly above normal going into September-October:

http://nsidc.org/arcticseaicenews/#antarctic-popup

This is good news because more sea-ice reflects heat from the Sun helping to keep the Earth cooler. The Sun in the Southern hemisphere spring/summer is some 10% stronger than in the Northern hemisphere in our spring/summer (due to perihelion in Earth's orbit around the Sun occurring in January). This means the reflectiveness ice-cover around the Antarctic (which is also in somewhat lower latitudes of the Southern Hemisphere that Arctic ice is in the North) is more important than ice over the Arctic Ocean in reflecting the Sun's heat.

The deficit of ice is the Arctic and possible excess in the Antarctic is also masked by cloud-cover. There is usually a lot of cloud-cove over the high Arctic in summer; often stratus that forms with the supply of moist air off the melting ice and leads in the open ocean. Low stratiform cloud-cover has an albedo of 65% or more and so mutes the effect of removing ice-cover from the Arctic. Around Antarctica is the passage of intense depressions that persists throughout the year; these bring plenty of cloud and snowfall (and rain further north) and the depressions and attendant southern Westerlies to the north have grown more intense in recent years as a result of global warming. Higher rainfall and snowfall in the critical latitudes freshens the surface waters of the Southern Ocean making them slightly easier to freeze, cloud-cover due to the persistent sub-Antarctic depressions helps protect this sea-ice from the Sun in summer but delays cooling in autumn and winter. As in the Arctic, cloud-cover in the sub-Antarctic mutes the effect of increasing or decreasing sea-ice on the albedo of the Earth-atmosphere system locally.

Extensive low cloud-cover over high latitudes in summer is no bad thing if it keeps these regions cool and reduces their overall sensitivity to rising CO₂ levels and delays the onset of disastrous tipping points,-  whereby methane is released from disintegrating methane-clathrates on Arctic coastal shelves and the unstoppable melt of Greenland and West Antarctic Ice-sheets occurs.

ps. The link takes you to the Arctic sea-ice page. From there you need to click on the pop-up that says "Antarctic Daily Images" to see the Antarctic sea-ice extent. I did click on the pop-up to copy that link address but for some reason you are taken to the Arctic sea-ice site, which is fine if you wish to monitor Arctic sea-ice extent (which I do myself because I use it to ascertain what the coming season likely has in store!)

Edited August 19, 2016 by iapennell
add point

[knocker]

 

[stewfox]

On ‎19‎/‎08‎/‎2016 at 21:03, iapennell said:

Currently Antarctic sea-ice extent is close to the long-term norm for August (winter in Southern Hemisphere) and looking at the trend looks like it might be slightly above normal going into September-October:

http://nsidc.org/arcticseaicenews/#antarctic-popup

This is good news because more sea-ice reflects heat from the Sun helping to keep the Earth cooler. The Sun in the Southern hemisphere spring/summer is some 10% stronger than in the Northern hemisphere in our spring/summer (due to perihelion in Earth's orbit around the Sun occurring in January). This means the reflectiveness ice-cover around the Antarctic (which is also in somewhat lower latitudes of the Southern Hemisphere that Arctic ice is in the North) is more important than ice over the Arctic Ocean in reflecting the Sun's heat.

 

The Antarctica ice cover is way down on recent years. How much of influence do you think an extra 2 million sq kms of sea ice would make to the global warming.

Edited August 24, 2016 by stewfox

[BornFromTheVoid]

18 minutes ago, stewfox said:

The Antarctica ice cover is way down on recent years. How much of influence do you think an extra 2 million sq kms of sea ice would make to the global warming.

Lets keep in mind that that there was 1 single short lived period where the anomaly was over +2 million. For the time when the ice coverage shot up (between 2013 and 2015), the anomaly averaged around +1 million km2, peaking at about +1.5 million in the Antarctic winter and dropping back to about 0.5 million during the Antarctic summer. So when it comes to the albedo impact, you're really just looking at about 3 summer with coverage a little more than 0.5 million km2 above average.

[stewfox]

1 hour ago, BornFromTheVoid said:

Lets keep in mind that that there was 1 single short lived period where the anomaly was over +2 million. For the time when the ice coverage shot up (between 2013 and 2015), the anomaly averaged around +1 million km2, peaking at about +1.5 million in the Antarctic winter and dropping back to about 0.5 million during the Antarctic summer. So when it comes to the albedo impact, you're really just looking at about 3 summer with coverage a little more than 0.5 million km2 above average.

I agree probably negligible, say 0.05c ?

However if we are going to build a 3000 mile wide 100 metre deep steel wall up north I think we should know ?

 

[iapennell]

3 hours ago, stewfox said:

The Antarctica ice cover is way down on recent years. How much of influence do you think an extra 2 million sq kms of sea ice would make to the global warming.

Let's see: The surface area of the Earth is 4 X Pi X 6400 X 6400 square kilometres = 514470600 km squared (by approximating Pi to 3.14!!). Two million square kilometres of the Earth's surface represents just under two fifths of 1% of the entire surface of our planet. The mean annual insolation near 60 degrees South where such ice cover fluctuations occur is near 70% of the global mean. So the loss of about 80% of insolation due to ice cover (assuming an albedo of 0.85 to replace that of an ocean surface of albedo 0.05) would be the equivalent to a reduction of about 0.2% of global annual insolation absorbed by the surface. This would produce a global temperature drop of around 0.15C.

However, the high preponderance of fairly reflective cloud cover over the Southern Ocean (most thick cloud cover has an albedo near 0.65) means that the effective change in the local albedo due to extra ice cover and factoring in the higher albedo of ocean surfaces when the Sun is low in the sky (most of the time in these latitudes) then the effective change in albedo is probably less than 0.2. All of this means that the increase in pack-ice extent by 2 million square kilometres will yield a global temperature drop of slightly less than 0.05C. 

By the same token, it is certain that the positive feedback effect caused by reduced ice cover in the Arctic is much smaller than some of the modelling would suggest. The summer over the Arctic Ocean is dominated (largely) by stratocumulus cloud-cover. Even where skies are clear over open ocean the Sun is always low down over the high Arctic and this increases the albedo of surface waters to upwards of 30%. Furthermore the maximum possible insolation that could theoretically be absorbed at the North Pole is scarcely half the average theoretical maximum of insolation that could be absorbed by a given area over the globe as a whole. All this diminishes the potential impact of reduced ice cover in the highest latitudes on global climate. However, that is not to say that at a local level that sea-ice anomalies don't have significant feedback effects.

Edited August 24, 2016 by iapennell
correction

[knocker]

 

[knocker]

 

[Gray-Wolf]

https://sunshinehours.net/

Big drop off in extent recently? First of the spring storms?

[stewfox]

16 hours ago, Gray-Wolf said:

https://sunshinehours.net/

Big drop off in extent recently? First of the spring storms?

Do you see in the next decade or so the Antarctica to start showing sustained downward movement ?

Perhaps recent years were just blips that didn't need extensive theory to explain them.

 

 

[Gray-Wolf]

https://robertscribbler.com/2016/09/02/warm-storm-force-winds-blowing-up-from-the-equator-change-west-antarctic-winter-to-summer/

Bit more info on the recent losses.

Hi stew!! Models show for rapid retreat in sea ice extent over the years up to 2050 so this may well be the beginning of that process ( that was rudely interrupted by the 'slowdown' in global temps years?). With PDO strongly positive for years now and the IPO following suit the conditions that brought us all the losses ( 50's to late 70's) have returned but are still up against the ozone hole forcing..... that said the AGW forcing is far greater now than it was in 1979....

[stewfox]

On 04/09/2016 at 16:56, Gray-Wolf said:

https://robertscribbler.com/2016/09/02/warm-storm-force-winds-blowing-up-from-the-equator-change-west-antarctic-winter-to-summer/

Bit more info on the recent losses.

Hi stew!! Models show for rapid retreat in sea ice extent over the years up to 2050 so this may well be the beginning of that process ( that was rudely interrupted by the 'slowdown' in global temps years?). With PDO strongly positive for years now and the IPO following suit the conditions that brought us all the losses ( 50's to late 70's) have returned but are still up against the ozone hole forcing..... that said the AGW forcing is far greater now than it was in 1979....

Seeing some large losses down there fairly early into the melt season. Already sub 18m km2  cf 20m km2 2014

https://ads.nipr.ac.jp/vishop/#/extent

[knocker]

 

[stewfox]

On 04/09/2016 at 16:56, Gray-Wolf said:

https://robertscribbler.com/2016/09/02/warm-storm-force-winds-blowing-up-from-the-equator-change-west-antarctic-winter-to-summer/

Bit more info on the recent losses.

Hi stew!! Models show for rapid retreat in sea ice extent over the years up to 2050 so this may well be the beginning of that process ( that was rudely interrupted by the 'slowdown' in global temps years?). With PDO strongly positive for years now and the IPO following suit the conditions that brought us all the losses ( 50's to late 70's) have returned but are still up against the ozone hole forcing..... that said the AGW forcing is far greater now than it was in 1979....

Seems to have level off in the last few weeks

 

 

[knocker]

Tropical Pacific SST drivers of recent Antarctic sea ice trends

Abstract: A strengthening of the Amundsen Sea Low from 1979-2013 has been shown to largely explain the observed increase in Antarctic sea ice concentration in the eastern Ross Sea and decrease in the Bellingshausen Sea. Here we show that while these changes are not generally seen in freely-running coupled climate model simulations, they are reproduced in simulations of two independent coupled climate models; one constrained by observed sea surface temperature anomalies in the tropical Pacific, and the other by observed surface wind-stress in the tropics. Our analysis confirms previous results and strengthens the conclusion that the phase change in the Interdecadal Pacific Oscillation from positive to negative over 1979-2013 contributed to the observed strengthening of the Amundsen Sea Low and associated pattern of Antarctic sea ice change during this period. New support for this conclusion is provided by simulated trends in spatial patterns of sea ice concentrations that are similar to those observed. Our results highlight the importance of accounting for teleconnections from low to high latitudes in both model simulations and observations of Antarctic sea ice variability and change.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0440.1

[Gray-Wolf]

Well we're still running record low ice around Antarctica and today the graph went near vertical! NSIDC are worried about the low ice on both sides of the Peninsula and the chances of ice shelf failures if the spend to long at the mercy of open water over the Austral summer?

I know with the Arctic showing record temps and low ice all eyes are up north but just as startling events are also now happening down south!

[Relativistic]

What's going on? Do we abandon our previous theories for the record high ice extent/ area? The ozone hole is still there and now we're at record lows...

Edited November 15, 2016 by Relativistic

[BornFromTheVoid]

1 hour ago, Relativistic said:

What's going on? Do we abandon our previous theories for the record high ice extent/ area? The ozone hole is still there and now we're at record lows...

Most researchers seemed to suggest things would reverse rather soon, but Antarctic sea ice variability is huge anyway so I guess we wait and see where the trend goes for now.

[Gray-Wolf]

13 hours ago, Relativistic said:

What's going on? Do we abandon our previous theories for the record high ice extent/ area? The ozone hole is still there and now we're at record lows...

https://worldview.earthdata.nasa.gov/?p=antarctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&t=2016-11-15&z=3&v=-5595136,-2613248,5595136,2613248

If you take a look at the sat images you'll see the winds flowing off the Continent are still pretty strong and have open polynya all around the coasts? So that leaves us with changes in the Pacific cycles limiting outward extent by either storminess or ( relatively) warm waters now present under the circumpolars?