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Gray-Wolf

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Stupid Questions
« on: December 05, 2016, 12:48:43 PM »
With the startling drop in sea ice around Antarctica we might need a thread like this as more and more folk take an interest?

So , for starters;

Will the loss of the Larsen's impact the ice cover in Weddell over the years to come? I ask as I could see Ronne suffering if facing open water and swells from storms. I can see the Ross end of the channel ( that makes West Antarctica an Island at our Temp/GHG forcings?) opening up but found it harder to see similar happening in Weddell due to the perennial ice there?
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Tigertown

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Re: Stupid Questions
« Reply #1 on: December 05, 2016, 07:00:12 PM »
If the Sea Ice around Antarctica reaches an early low or just ends with a very extreme low, will this throw the whole system further  off kilter and even affect the Arctic's 2017 melt season? In a more stable system, I would answer; Hardly! Now,though, I am not so sure.

Tealight

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Re: Stupid Questions
« Reply #2 on: December 07, 2016, 09:02:13 PM »
Will the loss of the Larsen's impact the ice cover in Weddell over the years to come? I ask as I could see Ronne suffering if facing open water and swells from storms. I can see the Ross end of the channel ( that makes West Antarctica an Island at our Temp/GHG forcings?) opening up but found it harder to see similar happening in Weddell due to the perennial ice there?

The Weddel Sea is still shelterd by the Antarctic Peninsula so I don't expect the loss of Larsen to have any significant impact.

For Pine Island glacier its a different story. Its is directly connected over channels to the Filchner-Ronne ice shelf. The bedrock is pretty much everywhere below -1000m. In a few hundred years the Antarctic Peninsula could become an actual island.

I just downloaded Bedmap2 for Antarctica and will try to analyze some interesting features.

Attached is Westantarctica as a bedrockmap and surface map. For Bedrock black means above sea level and bright pink below -1000m.


Gray-Wolf

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Re: Stupid Questions
« Reply #3 on: December 09, 2016, 05:00:52 PM »
Do full moon tides impact the ice shelfs more than normal tides?
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AbruptSLR

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Re: Stupid Questions
« Reply #4 on: December 09, 2016, 07:11:00 PM »
In a few hundred years the Antarctic Peninsula could become an actual island.

While your timing might be correct, in Reply #23 of the following linked thread entitled: "Potential Collapse Scenario for the WAIS", I indicate that if we continue on our BAU pathway for a few more decades the Antarctic Peninsula could become an island sometime between 2090 and 2100:

http://forum.arctic-sea-ice.net/index.php/topic,31.0.html
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AbruptSLR

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Re: Stupid Questions
« Reply #5 on: December 09, 2016, 07:12:31 PM »
Do full moon tides impact the ice shelfs more than normal tides?

Yes, ice shelves response directly with the magnitude of the tides, so a full moon tide cases more bending stress in the ice shelves than do normal tides.
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Gray-Wolf

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Re: Stupid Questions
« Reply #6 on: December 09, 2016, 10:30:56 PM »
Thanks for that AbruptSLR!

I kinda figured it must ! With most shelfs now free of sea ice the coming 'Full moon wiggle' is probably and 'extra' that the majority of the last 30 years didn't get due to the attachment of the Sea ice to the shelf front?
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dingojoe

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Re: Stupid Questions
« Reply #7 on: December 09, 2016, 11:13:37 PM »
So, what exactly is the baseline when determining extent and minimum of sea ice in Antarctica?  I assume ice shelves are not included when computing sea ice extent.  Unlike the Arctic, there is quite a bit of sea covered with ice shelves.  Looking at NASA's Worldview, they provide boundaries for the land and for ice shelves.  Sometimes the boundaries seem to have been updated (like for Larsen A and B), others seem to not quite match (not an ice shelf but the boundary for the PIIG is outdated).  Was the area covered by Larsen A and B not considered sea ice covered when they were ice shelves but now that the shelves have collapsed the area is counted?  If the large area of Larsen C were to break off but not immediately move out, does that instantly increase the area covered by sea ice? 

I know these examples are relatively small in the scheme of things, but they do add up.

Tigertown

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Re: Stupid Questions
« Reply #8 on: December 09, 2016, 11:41:59 PM »
The shelves are considered permanent and not counted in sea ice extent. Permanent is a word used a lot more loosely now days. I will leave the rest for others to comment on.

dingojoe

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Re: Stupid Questions
« Reply #9 on: December 10, 2016, 12:51:07 AM »
The shelves are considered permanent and not counted in sea ice extent. Permanent is a word used a lot more loosely now days. I will leave the rest for others to comment on.

So, just to clarify, prior to the breakup of Larsen B, that area was not considered part of sea ice extent, but this year the area that was formerly Larsen B and is currently covered by fast ice is considered part of the sea ice extent calculation.  Correct?

Tigertown

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Re: Stupid Questions
« Reply #10 on: December 10, 2016, 12:58:30 AM »
That fast ice and any other fast ice around Antarctica other than shelf ice would be sea ice. Shelf ice comes from glaciers pushing out past a grounding line into the ocean and are usually much taller than simple fast ice.

Ice shelf in background.
« Last Edit: December 10, 2016, 01:20:45 AM by Tigertown »

Tealight

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Re: Stupid Questions
« Reply #11 on: December 10, 2016, 12:31:53 PM »
The shelves are considered permanent and not counted in sea ice extent. Permanent is a word used a lot more loosely now days. I will leave the rest for others to comment on.

So, just to clarify, prior to the breakup of Larsen B, that area was not considered part of sea ice extent, but this year the area that was formerly Larsen B and is currently covered by fast ice is considered part of the sea ice extent calculation.  Correct?

The NSIDC uses land masks and coastal masks for their extent calculations. These prevent false sea ice detection from continents, islands, ice shelfs and coastlines. I'm pretty sure that they never change these masks to keep data consistent with previous years.

When you look at the latest Antarctica map Larsen A and B are still masked out.
http://nsidc.org/arcticseaicenews/files/1999/12/s_anom_hires.png

Nasa Worldview uses coastlines from different sources and they can update their data as they please.
« Last Edit: December 16, 2016, 01:06:27 PM by Tealight »

Tealight

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Re: Stupid Questions
« Reply #12 on: December 16, 2016, 01:24:51 PM »
I found a strange ice area next to the Thwaites Glacier Tongue. It is a semi-permanent feature and looks different than the normal sea ice around it. In Sentinel1 images it darker than normal sea ice. Does anyone know why this ice is so different?

Link to Worldview: http://go.nasa.gov/2gIuO4R

johnm33

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Re: Stupid Questions
« Reply #13 on: December 16, 2016, 02:05:28 PM »
I'm no expert but when sentinel catches tidal surges they show up much whiter than normal, so maybe this is just thin new ice with a dusting of snow, thus a very smooth surface[?] and not very reflective.

Tigertown

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Re: Stupid Questions
« Reply #14 on: December 16, 2016, 03:26:46 PM »
It stayed attached to the fast ice(or tongue, not sure which) while everything broke up around it, for what that's worth.

EDIT: Last melt season some ice north of this location broke off as the season was ending and then came together at this location and froze together and attached to the ice there, and stayed.


« Last Edit: December 16, 2016, 03:45:28 PM by Tigertown »

Tealight

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Re: Stupid Questions
« Reply #15 on: December 17, 2016, 01:30:53 PM »
From the answers I assume that it is quite unknown and no one has named it yet. I believe it is caused by the Iceberg B22 (the big block to the right of my mentioned area), which calved off in 2002 and a large portion of it is still stuck there. The ocean depth varies between 800m and 300-250m  so the iceberg should disrupt or completly block ocean currents. My mentioned strange ice area  could be caused by this blockage. However is the different color and longevity solely a result of little ice movement or does the iceberg melt and create an area of (fresher)water ice?

Click on the image to start animation.
« Last Edit: February 13, 2017, 12:12:50 AM by Tealight »

CalamityCountdown

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Re: Stupid Questions
« Reply #16 on: December 17, 2016, 07:16:53 PM »
In reporting on the loss on sea ice extent on a daily basis, is it meaningful to report the loss in terms of the reduction in percent of total extent loss?. Is a 300,000 km loss of SIE in a day more  startling when there is 10,000,000 km of Antarctic SIE versus when there is just 6,000,000 km (which could be the extent at some point even before this month ends)?

Tigertown

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Re: Stupid Questions
« Reply #17 on: January 16, 2017, 06:20:10 AM »
@Tealight        You probably were right about that being old tongue ice. I think it may have been there a long time and had old hard frozen snow on it, perhaps giving it the visual difference; maybe or maybe not.
Whatever the case, I think it's days are numbered now.
Also, thanks for spotting it when you did, as it has been interesting to watch.
« Last Edit: January 16, 2017, 06:27:02 AM by Tigertown »

Paddy

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Re: Stupid Questions
« Reply #18 on: January 16, 2017, 08:46:17 AM »
What data sources give updates on the size of the Antarctic ice cap itself, and changes therein?

oren

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Re: Stupid Questions
« Reply #19 on: January 16, 2017, 12:45:17 PM »
There was some good site mentioned on the forum recently which shows ice mass balance for Antarctica, even with a breakdown by region. I have it bookmarked at home, will post later if no one can recall.

Tealight

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Re: Stupid Questions
« Reply #20 on: January 17, 2017, 04:57:08 PM »
@Tealight        You probably were right about that being old tongue ice. I think it may have been there a long time and had old hard frozen snow on it, perhaps giving it the visual difference; maybe or maybe not.
Whatever the case, I think it's days are numbered now.
Also, thanks for spotting it when you did, as it has been interesting to watch.

I closely followed the area everyday. On radar it now looks more similar to sea ice ice. Maybe the snow has melted away and exposed the regular sea ice. It will be interesting to see it melt away completely.


Red

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Re: Stupid Questions
« Reply #21 on: January 29, 2017, 12:12:30 PM »
Concerning the Halloween Crack and other new found surprises is there any evidence that any of this could be related to lessening gravitational pull due to ice mass loss? The rate of thinning is increasing like mad everywhere it would seem. At some point would this not show up as a weakening of the pull at the periphery? If so, would it not cause some lowering of the MSL translating into slightly lower low tides giving added stress to points closer to the coastline? There has to be a critical threshold for the formation of stress cracks that could probably be measured in centimetres.

oren

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Re: Stupid Questions
« Reply #22 on: January 29, 2017, 12:58:49 PM »
Concerning the Halloween Crack and other new found surprises is there any evidence that any of this could be related to lessening gravitational pull due to ice mass loss? The rate of thinning is increasing like mad everywhere it would seem. At some point would this not show up as a weakening of the pull at the periphery? If so, would it not cause some lowering of the MSL translating into slightly lower low tides giving added stress to points closer to the coastline? There has to be a critical threshold for the formation of stress cracks that could probably be measured in centimetres.
The WAIS is at 2.2 million Gt, and the whole AIS is around 25 million Gt.
Mass loss is around 150 Gt/year, which I believe is still quite negligible at this point though I haven't done any math. But if anyone can find measurements of MSL around Antarctica showing a slight lowering this can resolve the question directly.

CalamityCountdown

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Re: Stupid Questions
« Reply #23 on: January 29, 2017, 09:26:26 PM »
I just did a Google search for "albedo sea ice". All the 1st page News articles were focused on the Arctic. Given that it looks like a new satellite era record low for Antarctic SIE will be set within the next few weeks, is there a good reason why so much less attention is being paid to the albedo effect in Antarctica? And the lack of attention gets even more pronounced with a Google search for "albedo effect antarctica". The first listing is a 2015 article that discusses the increase in SIE in the Antarctic

magnamentis

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Re: Stupid Questions
« Reply #24 on: January 29, 2017, 09:53:53 PM »
I just did a Google search for "albedo sea ice". All the 1st page News articles were focused on the Arctic. Given that it looks like a new satellite era record low for Antarctic SIE will be set within the next few weeks, is there a good reason why so much less attention is being paid to the albedo effect in Antarctica? And the lack of attention gets even more pronounced with a Google search for "albedo effect antarctica". The first listing is a 2015 article that discusses the increase in SIE in the Antarctic

i share your general opinion and after a short back and forth discussion after i posted a similar post like yours a few months ago things got a bit more active on the global and antarctic side.

nevertheless i have an idea, must not be correct, but at least an idea as to why this is so. i think the main reason is that the arctic, at least the surrounding land, has been populated for a long time, hence there is a history, more know how and probably people were doing science there even before the existence of the antarctic was even known.

since this is still the case, i mean that the arctic and it's periphery are well populated compared to the antarctic which is basically "not populated" except a few stations, the interest in and knowledge about the arctic is many times greater. perhaps someone else has a better idea/explanation, let's see :-)

EDIT: as to albedo, the impact depending on surface conditions (water, ice, rock etc. ) and latitude (sun angle) should be the same, at least mathematically, again there are pros around here and there is certainly more details to tell but as a general rule of thumb that should be similar like in the arctic. one thing that obviously differs is that the part which is ocean in the north is land in the south and the part which is often land in the north (periphery) is 99% ocean in the south.
« Last Edit: January 29, 2017, 10:00:43 PM by magnamentis »
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Red

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Re: Stupid Questions
« Reply #25 on: January 29, 2017, 10:00:25 PM »
Concerning the Halloween Crack and other new found surprises is there any evidence that any of this could be related to lessening gravitational pull due to ice mass loss? The rate of thinning is increasing like mad everywhere it would seem. At some point would this not show up as a weakening of the pull at the periphery? If so, would it not cause some lowering of the MSL translating into slightly lower low tides giving added stress to points closer to the coastline? There has to be a critical threshold for the formation of stress cracks that could probably be measured in centimetres.
The WAIS is at 2.2 million Gt, and the whole AIS is around 25 million Gt.
Mass loss is around 150 Gt/year, which I believe is still quite negligible at this point though I haven't done any math. But if anyone can find measurements of MSL around Antarctica showing a slight lowering this can resolve the question directly.
Oren that math is way over my pay grade. I'm just curious if there is anything to that thought. The forces in play have a maximum that at some point will be weakened by mass loss. At a certain point it becomes " the straw that broke the camels back". 

FredBear

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Re: Stupid Questions
« Reply #26 on: January 30, 2017, 12:06:51 AM »
I just did a Google search for "albedo sea ice". All the 1st page News articles were focused on the Arctic.

Perhaps the albedo of sea ice is much less important in the southern hemisphere
The differences between North and South poles are:-
1. Apart from Greenland, the land areas in the north loses most of the snow cover, leading to low albedo each year. In the south the land keeps the snow cover each year so that has relatively high albedo.
2. The sea ice in the north used to protect the dark ocean below over vast areas but that albedo is being reduced. In the south, most of the sea ice normally melts out so the albedo effects are changing relatively little (up till now?).
3. Black carbon deposits are more prevalent in the north because of the surrounding land, and organic growth can come up from the underlying sea. (Darkening of the ice is particularly important for reducing albedo in the Greenland Ice Sheet.) In the south the snow cover is relatively pristine until it falls off the edge of the continent.
I have ignored the changes in albedo that occur as snow starts melting as these are also more significant in the north.

Paddy

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Re: Stupid Questions
« Reply #27 on: January 31, 2017, 02:39:23 PM »
Stupid, open-ended question here: do we expect sea ice extent around Antarctica to go back to something vaguely in line with the previous trend next year or to stay low following this year's drop?

Darvince

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Re: Stupid Questions
« Reply #28 on: January 31, 2017, 05:31:42 PM »
CFS, which is trash at predicting Arctic sea ice, does a decent job with Antarctic sea ice, and predicts an even lower maximum for 2017 with the Weddell polynya developing and lasting all winter.