Support the Arctic Sea Ice Forum and Blog

Author Topic: Is Antarctic sea ice really expanding?  (Read 27725 times)

crandles

  • ASIF Upper Class
  • Posts: 2298
    • View Profile
  • Liked: 35
  • Likes Given: 38
Re: Is Antarctic sea ice really expanding?
« Reply #50 on: August 25, 2015, 12:23:05 PM »
and when we see low area like now, is that a good sign, also a bad sign, or a worse sign?
A low winter minimum is obviously a bad sign, but in order for the ice to expand in area, you need it to melt first, then refreeze on the sea surface later. It is not warm enough yet to melt yet this year. So towards the end of the melting season, if melting of icesheet continues as expected, and when re-freeze begins, I presume you would get more thin ice frozen on top of the sea.

I know there is no contradiction between saying high area is a bad sign and low area is a bad sign. It just seemed you were saying high area was a bad sign when we have got low area at the moment.

Next years freeze season getting large area of thin ice seems quite possible. But I wasn't looking that far ahead. A low maximum this year seems likely to result in a low minimum next year. Yes that isn't the end of matters maybe you get an unusual refreeze after such an event. However, it seems necessary to comment on whether a low minimum is likely before we get around to speculating on what happens after that.

Does more open water from low area at minimum have effects on ice sheets? Albedo causing more energy absorption being re-radiated to ice sheets causing melting seems unlikely to be a major effect even if warmer water can melt more sea ice. More snow on ice sheets may be a larger effect than that.

However, I am more inclined to fear the larger effects are from common cause than from effects of open water. i.e. more rising deep water and ENSO having an effect on melting ice shelves that is also causing the low sea ice area. With this I am not clear on likely effects: Does this extra melting mean less saltly sea water and slower melt of sea ice or does the increased rising deep water cause more mixing?

By the time we get to after the minimum, the ENSO heat may well have moved north but how long does a bout of strong upwelling deep water last? Seems plenty to ponder about next 6 months before we start getting too far ahead with considering the next refreeze?


Gonzo

  • ASIF Citizen
  • Posts: 123
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: Is Antarctic sea ice really expanding?
« Reply #51 on: August 25, 2015, 03:07:54 PM »
crandles
Quote
Does more open water from low area at minimum have effects on ice sheets? Albedo causing more energy absorption being re-radiated to ice sheets causing melting seems unlikely to be a major effect even if warmer water can melt more sea ice. More snow on ice sheets may be a larger effect than that.
I think in the Antarctic the factor of increasing winds, due to climate change, is a major factor. The winds push ice around on the surface, and also, if cold enough, can cause freezing of surface, and yes, there could be more snow, so the Antarctic is much harder than the Arctic (as if that's not hard enough), although the calving of glaciers is the main problem, since they suck ice from the interior, so wether the ice gets bigger in area during a re-freeze or not, or gets to a low minimum is not as important as how much ice calves off the glaciers.

Quote
Does this extra melting mean less saltly sea water and slower melt of sea ice or does the increased rising deep water cause more mixing?
Good question. I've heard scientists say that the ice is melting from underneath, so the 'grounding point' of the ice sheets is moving further back all the time (then breaks off), but the constitution of that ice under the glacier, could be very complex, with various minerals built up over a long time, or salt water or fresh water?
They are saying the sea water is warmer, and even if the winds pick up, and there is more snow, the melting under sea ice and glaciers continues unabated.

crandles
Quote
Seems plenty to ponder about next 6 months before we start getting too far ahead with considering the next refreeze?
I'm sorry, I may have read this thread wrongly. I thought it was asking the question 'is the Antarctic getting bigger', and I thought that related to a re-freeze that happened last year, and the denialists went ballistic claiming it disproved global warming, so I was just responding to what the refreeze really means. IE. A bad sign, not a good sign (bad sign meaning bad sign for our planet).
However, to your point about lowest maximum -- we had the lowest maximum for the Arctic this year, and not sure we will get the lowest minimum as a direct correlation, but the season there is not over, and could extend, so not sure, but the Antarctic is very different I would think.
If the glaciers keep being undercut, grounding points keep receding, and they keep calving, that's all that counts, because the glaciers are bringing ice from the interior into the ocean.  So area of ice not very important when talking about sea level rise, especially since re-freeze ice on sea surface and then melt does not increase sea levels.
But you know all this. Thanks for helping me think it through.

crandles

  • ASIF Upper Class
  • Posts: 2298
    • View Profile
  • Liked: 35
  • Likes Given: 38
Re: Is Antarctic sea ice really expanding?
« Reply #52 on: September 01, 2015, 01:00:10 PM »
Anomaly back positive

2015.6576   0.0196874  14.8234634

after gaining impressive 833k in a week. Back in the middle of the pack.

This doesn't rule out a really low minimum as maybe volatility implies the ice cover is thin but looks like I was speculating on that a bit too soon.

Well past lowest maximum:
1986.7206  -0.4888180  14.6039534

Nearer to second lowest maximum:
1984.7041  -0.1074521  14.9482679

Now looks like plenty of time before normal date of maximum to get above that.

Gray-Wolf

  • ASIF Middle Class
  • Posts: 785
    • View Profile
  • Liked: 34
  • Likes Given: 133
Re: Is Antarctic sea ice really expanding?
« Reply #53 on: September 19, 2015, 12:00:38 PM »
And down we go again! Does that mean we passed max at the last peak?

That was an odd summer?

http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html
KOYAANISQATSI

ko.yaa.nis.katsi (from the Hopi language), n. 1. crazy life. 2. life in turmoil. 3. life disintegrating. 4. life out of balance. 5. a state of life that calls for another way of living.
 
VIRESCIT VULNERE VIRTUS

Jim Hunt

  • ASIF Governor
  • Posts: 4051
    • View Profile
    • The Arctic sea ice Great White Con
  • Liked: 131
  • Likes Given: 21
Re: Is Antarctic sea ice really expanding?
« Reply #54 on: September 20, 2015, 01:15:36 PM »
And down we go again! Does that mean we passed max at the last peak?

It certainly looks that way:

http://GreatWhiteCon.info/resources/antarctic-sea-ice-graphs/#Extent

Reality is merely an illusion, albeit a very persistent one - Albert Einstein

AbruptSLR

  • ASIF Emperor
  • Posts: 17105
    • View Profile
  • Liked: 286
  • Likes Given: 209
Re: Is Antarctic sea ice really expanding?
« Reply #55 on: May 16, 2016, 05:10:02 PM »
The linked article explains that there is nothing paradoxical about the recent growth in Antarctic sea ice cover:

S.V. Nghiem , I.G. Rigor, P. Clemente-Colón, G. Neumann & P.P. Li (August 2016, Available online 11 May 2016), "Geophysical constraints on the Antarctic sea ice cover", Remote Sensing of Environment, Volume 181, , Pages 281–292


http://www.sciencedirect.com/science/article/pii/S0034425716301481

Abstract: "The contrast between the slight increase of Antarctic sea ice and the drastic reduction of Arctic sea ice since the 1970s has been a conundrum to be resolved. Sea ice trajectory tracking with satellite scatterometer data in 2008 shows that ice around Antarctica is pushed offshore by katabatic winds influenced by the continental topography. The ice trajectories reveal that sea ice, grown earlier in the ice season, drifts northward away from the Antarctic continent forming a circumpolar frontal ice zone (FIZ) behind the ice edge. The FIZ thereby consists of sea ice that becomes rougher due to a longer exposure to wind and wave actions, and thicker over time by more ice growth and greater snow accumulation.
In the Antarctic circumpolar sea ice zone adjacent to the sea ice edge, satellite data in 1999–2009 exhibit a band of strong radar backscatter, which is consistent with the signature of older, thicker, and rougher sea ice with more snow in the FIZ. This sea ice band, as wide as 1000 km, serves as a ‘Great Shield,’ encapsulating and protecting younger and thinner ice in the internal ice pack. In the young and thin ice region behind the FIZ, ice can grow rapidly as winds continue opening interior areas thereby creating effective “ice factories.” In addition, ridging can enhance ice thickness by convergence toward the circumpolar FIZ that is recirculated by westerly winds and currents. During the ice growth season, the FIZ advances until reaching lower-latitude warm waters at a boundary determined by the southern Antarctic Circumpolar Current front that is constrained by seafloor features. These persistent topographical and bathymetric geological factors help sustain the Antarctic sea ice cover. As such, the behavior of Antarctic sea ice is not a paradox as some have suggested, but instead is consistent with the geophysical characteristics in the southern polar region that starkly contrast to those in the Arctic."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 17105
    • View Profile
  • Liked: 286
  • Likes Given: 209
Re: Is Antarctic sea ice really expanding?
« Reply #56 on: May 23, 2016, 11:14:28 PM »
The linked study offers new insights into Antarctic sea ice cover and the influence of seafloor constraints on Southern Ocean currents:

S.V. Nghiem, I.G. Rigor, P. Clemente-Colón, G. Neumann & P.P. Li (August 2016, Available online 11 May 2016), " Geophysical constraints on the Antarctic sea ice cover", Remote Sensing of Environment, Volume 181, Pages 281–292, doi:10.1016/j.rse.2016.04.005


http://www.sciencedirect.com/science/article/pii/S0034425716301481

Abstract: "The contrast between the slight increase of Antarctic sea ice and the drastic reduction of Arctic sea ice since the 1970s has been a conundrum to be resolved. Sea ice trajectory tracking with satellite scatterometer data in 2008 shows that ice around Antarctica is pushed offshore by katabatic winds influenced by the continental topography. The ice trajectories reveal that sea ice, grown earlier in the ice season, drifts northward away from the Antarctic continent forming a circumpolar frontal ice zone (FIZ) behind the ice edge. The FIZ thereby consists of sea ice that becomes rougher due to a longer exposure to wind and wave actions, and thicker over time by more ice growth and greater snow accumulation.
In the Antarctic circumpolar sea ice zone adjacent to the sea ice edge, satellite data in 1999–2009 exhibit a band of strong radar backscatter, which is consistent with the signature of older, thicker, and rougher sea ice with more snow in the FIZ. This sea ice band, as wide as 1000 km, serves as a ‘Great Shield,’ encapsulating and protecting younger and thinner ice in the internal ice pack. In the young and thin ice region behind the FIZ, ice can grow rapidly as winds continue opening interior areas thereby creating effective “ice factories.” In addition, ridging can enhance ice thickness by convergence toward the circumpolar FIZ that is recirculated by westerly winds and currents. During the ice growth season, the FIZ advances until reaching lower-latitude warm waters at a boundary determined by the southern Antarctic Circumpolar Current front that is constrained by seafloor features. These persistent topographical and bathymetric geological factors help sustain the Antarctic sea ice cover. As such, the behavior of Antarctic sea ice is not a paradox as some have suggested, but instead is consistent with the geophysical characteristics in the southern polar region that starkly contrast to those in the Arctic."

See also:
http://phys.org/news/2016-05-sea-ice-differences-earth-poles.html

Extract: "Why has the sea ice cover surrounding Antarctica been increasing slightly, in sharp contrast to the drastic loss of sea ice occurring in the Arctic Ocean? A new NASA-led study finds the geology of Antarctica and the Southern Ocean are responsible.


To address the question of how the Southern Ocean maintains this great sea ice shield, the team combined sea surface temperature data from multiple satellites with a recently available bathymetric chart of the depth of the world's oceans. Sea surface temperature data reveal that at the peak of ice growth season, the boundary of the ice shield remains behind a 30-degree Fahrenheit (-1 degree Celsius) temperature line surrounding Antarctica. This temperature line corresponds with the southern Antarctic Circumpolar Current front, a boundary that separates the circulation of cold and warm waters around Antarctica. The team theorized that the location of this front follows the underwater bathymetry.
When they plotted the bathymetric data against the ocean temperatures, the pieces fit together like a jigsaw puzzle. Pronounced seafloor features strongly guide the ocean current and correspond closely with observed regional Antarctic sea ice patterns. For example, the current stays near Bouvet Island, located 1,000 miles (1,600 kilometers) from the nearest land, where three tectonic plates join to form seafloor ridges. Off the coast of East Antarctica, the -1 degree Celsius sea surface temperature lines closely bundle together as they cross the Kerguelen Plateau (a submerged microcontinent that broke out of the ancient Gondwana supercontinent), through a deep channel called the Fawn Trough. But those lines spread apart over adjacent deep ocean basins, where seafloor features are not pronounced. Off the West Antarctica coast, the deep, smooth seafloor loses its grip over the current, allowing sea ice extent to decrease and resulting in large year-to-year variations."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 17105
    • View Profile
  • Liked: 286
  • Likes Given: 209
Re: Is Antarctic sea ice really expanding?
« Reply #57 on: July 06, 2016, 10:23:26 PM »
The linked reference associates changes in Antarctic sea-ice extent to changes in the IPO:

Gerald A. Meehl, Julie M. Arblaster, Cecilia M. Bitz, Christine T. Y. Chung & Haiyan Teng (2016), "Antarctic sea-ice expansion between 2000 and 2014 driven by tropical Pacific decadal climate variability", Nature Geoscience, doi:10.1038/ngeo2751

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2751.html

Abstract: "Antarctic sea-ice extent has been slowly increasing in the satellite record that began in 1979. Since the late 1990s, the increase has accelerated, but the average of all climate models shows a decline. Meanwhile, the Interdecadal Pacific Oscillation, an internally generated mode of climate variability, transitioned from positive to negative, with an average cooling of tropical Pacific sea surface temperatures, a slowdown of the global warming trend and a deepening of the Amundsen Sea Low near Antarctica that has contributed to regional circulation changes in the Ross Sea region and expansion of sea ice. Here we show that the negative phase of the Interdecadal Pacific Oscillation in global coupled climate models is characterized by anomalies similar to the observed sea-level pressure and near-surface 850 hPa wind changes near Antarctica since 2000 that are conducive to expanding Antarctic sea-ice extent, particularly in the Ross Sea region in all seasons, involving a deepening of the Amundsen Sea Low. These atmospheric circulation changes are shown to be mainly driven by precipitation and convective heating anomalies related to the Interdecadal Pacific Oscillation in the equatorial eastern Pacific, with additional contributions from convective heating anomalies in the South Pacific convergence zone and tropical Atlantic regions."


See also:
http://www.csmonitor.com/Environment/2016/0706/Scientists-reconcile-growth-in-Antarctic-sea-ice-with-global-warming-models
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson