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Antarctic Ice Discussion


pottyprof

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Should we find yearly sea ice dropping back into the 'pack' then I will find it worrying?

 

We know that , eventually over time, Antarctica will see its sea ice decline in line with global warmer temp forcings but the longer we can keep the shelf ice pinned to the coast the better!!

 

Loss of ice protection places swells against the floating shelve inducing 'waggle' and failure of the ice front. With glacier speeds at record levels then it would not be long before the next 'super berg' is in place and ready to break off.

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Posted
  • Location: Tasmania - obvioulsy :)
  • Location: Tasmania - obvioulsy :)

Agree GW. Sea ice acts as an effective barrier for ice shelves against ocean processes - and hence also protects the ice sheets themselves.

 

I coined a term "coastal exposure index" that keeps track of the broad-scale sea ice barrier. You can see it plotted in real time here: http://www.cawcr.gov.au/staff/preid/seaice/gsfc_sh_coastal_exposure.html. It's mostly interesting in summer months. A higher the coastal exposure index means trouble!

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Posted
  • Location: North York Moors
  • Location: North York Moors

Should we find yearly sea ice dropping back into the 'pack' then I will find it worrying?

 

We know that , eventually over time, Antarctica will see its sea ice decline in line with global warmer temp forcings but the longer we can keep the shelf ice pinned to the coast the better!!

 

Loss of ice protection places swells against the floating shelve inducing 'waggle' and failure of the ice front. With glacier speeds at record levels then it would not be long before the next 'super berg' is in place and ready to break off.

 

Quite a feat to make average conditions seem like a portent of doom.

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Posted
  • Location: Tasmania - obvioulsy :)
  • Location: Tasmania - obvioulsy :)

Quite a feat to make average conditions seem like a portent of doom.

 

I think you are misinterpreting what GW has expressed.

 

Nevertheless, a loss of a protective sea ice barrier does leave the shelves vulnerable.

 

Given the sub-surface warming of the ocean and subsequent weakening of the shelves, perhaps even "normal" sea ice conditions over summer months may be something to be concerned about.

Edited by Tasboy
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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Where we not seeing the rapid changes along the Peninsula then such worries would indeed be misplaced but the data from the past 2 decades makes the point made more salient?

 

With ice shelf grounding lines now about to allow a faster Ocean /ice exchange then any move toward less protection , for longer periods over the year, will mean increase in losses and faster retreat into the ice sheet for the grounding lines ( and so accessing more ice to 'float off')?

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Posted
  • Location: Tasmania - obvioulsy :)
  • Location: Tasmania - obvioulsy :)

Speaking of interesting...

 

Sea-ice extent seems to have had a late rally. The annual daily maximum is now in late September, rather than on the 5th September as previously mentioned.

http://www.cawcr.gov.au/staff/preid/seaice/sea_ice_table_extent.html

(It should be noted that there is a small problem with the satellite data for the 29th)

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

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

 

A bit of 'variability' over the last days on C.T. but no 'rally' yet?? ( i don't know how many days behind C.T. runs?) Surely we have gone long enough and have a gap wide enough to call 'max' now?

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Posted
  • Location: Edinburgh (previously Chelmsford and Birmingham)
  • Weather Preferences: Unseasonably cold weather (at all times of year), wind, and thunderstorms.
  • Location: Edinburgh (previously Chelmsford and Birmingham)

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

 

A bit of 'variability' over the last days on C.T. but no 'rally' yet?? ( i don't know how many days behind C.T. runs?) Surely we have gone long enough and have a gap wide enough to call 'max' now?

 

That's area, not extent.

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

That's area, not extent.

 

Whoops ! my bad. Must be showing break up at the ice edge? Is it 15 or 30% counting as '100%'  do you know? 

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Posted
  • Location: Tasmania - obvioulsy :)
  • Location: Tasmania - obvioulsy :)

Whoops ! my bad. Must be showing break up at the ice edge? Is it 15 or 30% counting as '100%'  do you know? 

Happens!

15% is counted as ice edge. And yes, there's lots of break up around the edge, pretty much right around the continent.

 

Unusually, there's a lot of relatively sparse ice around the Peninsular and B&A seas at the moment.

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Posted
  • Location: Solihull, West Midlands. - 131 m asl
  • Weather Preferences: Sun, Snow and Storms
  • Location: Solihull, West Midlands. - 131 m asl

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

 

A bit of 'variability' over the last days on C.T. but no 'rally' yet?? ( i don't know how many days behind C.T. runs?) Surely we have gone long enough and have a gap wide enough to call 'max' now?

 

GW..

 

Extent has gone up by another 60k KSq as of 1st Oct. That is 5 days on the trot of increases. Is that classified as a rally?  Its now at a max for this season. So no max yet.

We may now have a chance of the latest max recorded soon.  These values are according to NSIDC. I will check Tasboy's figures now.

 

I am not trying to make a point, except that this year has been extremely variable. Swinging around wildly, but the fact that it seems to be still increasing even this late in the season means what?

 

MIA

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Posted
  • Location: Solihull, West Midlands. - 131 m asl
  • Weather Preferences: Sun, Snow and Storms
  • Location: Solihull, West Midlands. - 131 m asl

Re,

 

The above tables that Tasboy  presents suggests that the 30/9 was the max for this year and shows a very slight fall for 1/10.

 

However the 30/9 is the equal 3rd latest maximum, with the all time (since measurements began) at 3/10.

Even a slight small gain in the next 2 days could beat this record.

 

So my question is still valid.

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Posted
  • Location: Tasmania - obvioulsy :)
  • Location: Tasmania - obvioulsy :)

GW..

 

Extent has gone up by another 60k KSq as of 1st Oct. That is 5 days on the trot of increases. Is that classified as a rally?  Its now at a max for this season. So no max yet.

We may now have a chance of the latest max recorded soon.  These values are according to NSIDC. I will check Tasboy's figures now.

 

I am not trying to make a point, except that this year has been extremely variable. Swinging around wildly, but the fact that it seems to be still increasing even this late in the season means what?

 

MIA

 

Yep, agree. It's been quite variable.

My take is that sea ice distribution has been responding over the last few months to the El Nino (via synoptic wind pattern), after having been free from ENSO constraints for the last few years.

 

The build up of sea ice in the Bellingshausen and Amundsen seas late in the season (it's the only place where sea ice is beyond it's climatological mean at the moment - http://www.cawcr.gov.au/staff/preid/seaice/gsfc_extent_hov_anom.html) often means that there is a chance that this "excess" sea ice may break over the Peninsula (much like a wave) as it is caught up in the circumpolar current and advects east. From there it is caught in the Weddell Sea gyre where it may expand further. I think that's what's happening at the moment (guess at this stage).

 

Sea surface temperatures in the B&S seas have also been colder than normal - at record lows for this time of the year as it works out. Mmmm, interesting...

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Posted
  • Location: Camborne
  • Location: Camborne

Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin

 

Antarctica’s contribution to global sea-level rise has recently been increasing1. Whether its ice discharge will become unstable and decouple from anthropogenic forcing2, 3, 4 or increase linearly with the warming of the surrounding ocean is of fundamental importance5. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica’s Filchner–Ronne ice shelf within the next two centuries6, 7. The ice basin’s retrograde bed slope would allow for an unstable ice-sheet retreat8, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability9, 10, 11. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner–Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming12, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability.

 

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2808.html

 

Press release

 

http://www.eurekalert.org/pub_releases/2015-10/pifc-twt100215.php

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Posted
  • Location: Camborne
  • Location: Camborne

Gains in Antarctic ice might offset losses

 

So much ice is piling up in the vast expanses of East Antarctica that, overall, it counterbalances the losses seen at glaciers thinning elsewhere on the frozen continent. It will take decades for Antarctic melting to overtake the mass gains and begin contributing substantially to sea-level rise, a new study argues.

 

The calculations are the latest in a long-running effort to weigh Antarctica’s ice. Whereas melting in Greenland has dramatically reduced its ice sheet, the situation in Antarctica is more complex.

 

“Parts of Antarctica are losing mass faster than before,†says Jay Zwally, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of a paper to appear in the Journal of Glaciology1. “But large parts have been gaining mass, and they’ve been doing that for a very long time.â€

 

The findings do not mean that Antarctica is not in trouble, Zwally notes. “I know some of the climate deniers will jump on this, and say this means we don’t have to worry as much as some people have been making out,†he says. “It should not take away from the concern about climate warming.†As global temperatures rise, Antarctica is expected to contribute more to sea-level rise, though when exactly that effect will kick in, and to what extent, remains unclear.

 

http://www.nature.com/news/gains-in-antarctic-ice-might-offset-losses-1.18486?WT.mc_id=TWT_NatureNews

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

New study projects that melting of Antarctic ice shelves will intensify

 

 

New research published today projects a doubling of surface melting of Antarctic ice shelves by 2050 and that by 2100 melting may surpass intensities associated with ice shelf collapse, if greenhouse gas emissions from fossil fuel consumption continue at the present rate.

Read more at: http://phys.org/news/2015-10-antarctic-ice-shelves.html#jCp

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Posted
  • Location: Camborne
  • Location: Camborne

Study Sees Powerful Winds Carving Away Antarctic Snow

 

 

A new study has found that powerful winds are removing massive amounts of snow from parts of Antarctica, potentially boosting estimates of how much the continent might contribute to sea level. Up to now, scientists had thought that most snow scoured from parts of the continent was simply redeposited elsewhere on the surface. However, the new study shows that in certain parts, called scour zones, some 90 percent—an estimated 80 billion tons per year—is instead being vaporized, and removed altogether. The finding means that scientists must adjust their models of how much mass Antarctica is losing, and how much it might lose in the future. The study appears this week in the journal Geophysical Research Letters.

 

http://www.ldeo.columbia.edu/news-events/study-sees-powerful-winds-carving-away-antarctic-snow

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

So have they called an early max in Sea ice around Antarctica then?

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Posted
  • Location: Camborne
  • Location: Camborne

yes. It hit max extent on 10/6; El Niño slows late winter Antarctic ice growth. http://goo.gl/ogYQIg 

 

 

2015 Antarctic Maximum Sea Ice Extent Breaks Streak of Record Highs

 

The sea ice cover of the Southern Ocean reached its yearly maximum extent on Oct. 6. At 7.27 million square miles (18.83 million square kilometers), the new maximum extent falls roughly in the middle of the record of Antarctic maximum extents compiled during the 37 years of satellite measurements – this year’s maximum extent is both the 22nd lowest and the 16th highest. More remarkably, this year’s maximum is quite a bit smaller than the previous three years, which correspond to the three highest maximum extents in the satellite era, and is also the lowest since 2008.

 

https://www.nasa.gov/feature/goddard/2015-antarctic-maximum-sea-ice-extent-breaks-streak-of-record-highs

 

Edited by knocker
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Posted
  • Location: Napton on the Hill Warwickshire 500ft
  • Weather Preferences: Snow and heatwave
  • Location: Napton on the Hill Warwickshire 500ft

yes. It hit max extent on 10/6; El Niño slows late winter Antarctic ice growth. http://goo.gl/ogYQIg 

 

 

2015 Antarctic Maximum Sea Ice Extent Breaks Streak of Record Highs

 

https://www.nasa.gov/feature/goddard/2015-antarctic-maximum-sea-ice-extent-breaks-streak-of-record-highs

 

 

It goes up and up year after year and then one year, this year it drops and its all 'natural variability'. Apparently that doesn't work in the NH all ice variability is down to global warming.. How is it 22nd lowest and 16th highest ?? and previous  'recovery' from what ?, maybe the ice extent in the  1980s were below average in the SH and above average in the NH. ...and no mention of 'wind'

 

“There may be more high years in the future because of the large year-to-year variation in Antarctic extent, but such extremes are not near as substantial as in the Arctic, where the declining trend towards a new normal is continuing.â€

Edited by stewfox
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Posted
  • Location: Tasmania - obvioulsy :)
  • Location: Tasmania - obvioulsy :)

It's nice to have you back Stew. I was missing you!

 

I don't know that I would call it (2015 Antarctic sea ice extent pattern) natural variability - perhaps it might be best described as a sudden response (it was quite a sudden slowdown in growth) to lower latitude forcings. But then again, that is part of natural variability...

 

It goes up and up year after year and then one year, this year it drops and its all 'natural variability'. Apparently that doesn't work in the NH all ice variability is down to global warming.. How is it 22nd lowest and 16th highest ?? and previous  'recovery' from what ?, maybe the ice extent in the  1980s were below average in the SH and above average in the NH. ...and no mention of 'wind'

 

“There may be more high years in the future because of the large year-to-year variation in Antarctic extent, but such extremes are not near as substantial as in the Arctic, where the declining trend towards a new normal is continuing.â€

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Posted
  • Location: bingley,west yorks. 100 asl
  • Location: bingley,west yorks. 100 asl

Highs,lows lol.

We'll always have variability.In both hemispheres.History says and warming has been alot greater in the past at times.The earth will end through natural causes or alien invasion lol imo.

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Posted
  • Location: Napton on the Hill Warwickshire 500ft
  • Weather Preferences: Snow and heatwave
  • Location: Napton on the Hill Warwickshire 500ft

It's nice to have you back Stew. I was missing you!

 

I don't know that I would call it (2015 Antarctic sea ice extent pattern) natural variability - perhaps it might be best described as a sudden response (it was quite a sudden slowdown in growth) to lower latitude forcings. But then again, that is part of natural variability...

 

I think it shows sea ice variability can change rapidly from year to year.

 

Antarctic sea ice is more seasonal then the Arctic however  to a degree as the min extents  rise year on year in the Antarctic that's becoming less marked.

 

Perhaps 'finding' a human explanation on 10 year scales is pointless  ?

Edited by stewfox
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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Who's to say that the forcings that drove the year on year increases from the early 80's also allowed further extension in certain areas due to alterations in wind/storm tracks? 

 

If we are seeing this phase ending then the sort of 'slowdown' we witnessed this year may become increasingly common over the whole of the re-freeze period limiting the extent by unfavorable wind/wave action at the ice edge?

 

No matter how much ice is created at the shore polynias the 'extent' is maintained by destruction /float off and melt of ice at the outside of the pack?

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