Just idle curiosity, but can anyone who understands these things kindly
explain:

If I look at the map of _Antarctic_ sea ice (not the graph, the map) at:

http://nsidc.org/arcticseaicenews/

then I'm looking at the Ross Sea - the major inlet right below the S pole:

1. What is the mass of ice apparently floating away from the continent - it
looks huge but completely unconnected to and some considerable distance from
the nearest coastline.

2. What's happened to the Ross Ice Shelf? Isn't that meant to fill a large
area of the Ross Sea? But the median extent line for what is presumably the
minimum ice extent at about this time of year shows largely open water for
the Ross Sea. Or is the ice shelf drawn to be part of the Antarctic land
mass in this presentation?

(Not uninteresting looking at this map: much of the slight excess of
Antarctic sea ice seems to concentrated in the Weddell Sea for some reason,
whereas the coastal area from the Peninsula round to the Ross Sea seems well
below 'normal'. Looks like a very marked change away from the median
distribution, or is this just a one-year picture - ie every year shows a
different distribution and this just happens to be the picture this year?)

On Friday, 27 February 2015 17:49:38 UTC, General wrote:
Just idle curiosity, but can anyone who understands these things kindly
explain:

If I look at the map of _Antarctic_ sea ice (not the graph, the map) at:

http://nsidc.org/arcticseaicenews/

then I'm looking at the Ross Sea - the major inlet right below the S pole:

1. What is the mass of ice apparently floating away from the continent - it
looks huge but completely unconnected to and some considerable distance from
the nearest coastline.

2. What's happened to the Ross Ice Shelf? Isn't that meant to fill a large
area of the Ross Sea? But the median extent line for what is presumably the
minimum ice extent at about this time of year shows largely open water for
the Ross Sea. Or is the ice shelf drawn to be part of the Antarctic land
mass in this presentation?

(Not uninteresting looking at this map: much of the slight excess of
Antarctic sea ice seems to concentrated in the Weddell Sea for some reason,
whereas the coastal area from the Peninsula round to the Ross Sea seems well
below 'normal'. Looks like a very marked change away from the median
distribution, or is this just a one-year picture - ie every year shows a
different distribution and this just happens to be the picture this year?)

You mean this link ?

http://nsidc.org/data/seaice_index/i...tent_hires.png

I wouldn't worry it all starts to freeze again now.

On Friday, 27 February 2015 17:49:38 UTC, General wrote:
Just idle curiosity, but can anyone who understands these things kindly
explain:

If I look at the map of _Antarctic_ sea ice (not the graph, the map) at:

http://nsidc.org/arcticseaicenews/

then I'm looking at the Ross Sea - the major inlet right below the S pole:

1. What is the mass of ice apparently floating away from the continent - it
looks huge but completely unconnected to and some considerable distance from
the nearest coastline.

I can't see and Antarctic sea ice on the page you linked but this map shows the current state of sea ice in the Antarctic.
http://polar.ncep.noaa.gov/seaice/sh.html

The mass you mention is an island of sea ice that has formed during the SH summer melt.

2. What's happened to the Ross Ice Shelf? Isn't that meant to fill a large
area of the Ross Sea? But the median extent line for what is presumably the
minimum ice extent at about this time of year shows largely open water for
the Ross Sea. Or is the ice shelf drawn to be part of the Antarctic land
mass in this presentation?

Yes, the ice shelf is mapped as part of the Antarctic land mass. Sea ice is a few feet thick and reforms each year. Ice shelves are about 1000 feet or more thick.

(Not uninteresting looking at this map: much of the slight excess of
Antarctic sea ice seems to concentrated in the Weddell Sea for some reason,
whereas the coastal area from the Peninsula round to the Ross Sea seems well
below 'normal'. Looks like a very marked change away from the median
distribution, or is this just a one-year picture - ie every year shows a
different distribution and this just happens to be the picture this year?)

The Weddell Sea is sheltered from the circumpolar current by the Antarctic Penisula so the sea-ice melt is less there.

On the map I linked you can animate the last month of sea ice and sea that island form. You can also click to see the se-ice this time last year.

"Alastair" wrote in message
...

I can't see and Antarctic sea ice on the page you linked

Sorry, I skipped a couple of short steps: Click on the blue bar below the
map images that says 'Antarctic Daily Images' and then on left-hand map
image to enlarge that.

but this map shows the current state of sea ice in the Antarctic.
http://polar.ncep.noaa.gov/seaice/sh.html

I guess that's a different representation of the same thing

The mass you mention is an island of sea ice that has formed during the SH
summer melt.

That's pretty odd though isn't it? Perhaps not, but it just seems unlikely.
How big is that 'island' - the size of Tasmania or something - difficult to
get a sense of scale? It's not like it's just a big iceberg. And how/why has
it calved off like that rather than melting from the ocean edge? That's what
caught my curiosity.

Yes, the ice shelf is mapped as part of the Antarctic land mass. Sea ice is
a few feet thick and reforms each year. Ice shelves are about 1000 feet or
more thick.

OK, that makes some sense. But I'd have preferred to see the landmass still
outlined separately from the shelves.

On Saturday, 28 February 2015 18:04:31 UTC, General wrote:
"Alastair" wrote in message

but this map shows the current state of sea ice in the Antarctic.
http://polar.ncep.noaa.gov/seaice/sh.html

I guess that's a different representation of the same thing

The mass you mention is an island of sea ice that has formed during the SH
summer melt.

That's pretty odd though isn't it? Perhaps not, but it just seems unlikely.

I think it is unusual, but that's normal! There is less sea ice than the median in the Ross Sea, but more in the Weddel Sea.

How big is that 'island' - the size of Tasmania or something - difficult to
get a sense of scale? It's not like it's just a big iceberg. And how/why has
it calved off like that rather than melting from the ocean edge? That's what
caught my curiosity.

You can see on your map that there are other areas of sea ice which have melted next to the coast rather than from the outer edge.

If you run the animate on the page I linked you can see that it melted first on the edge of the ice shelf then on the coast at each end.

Yes, the ice shelf is mapped as part of the Antarctic land mass. Sea ice is
a few feet thick and reforms each year. Ice shelves are about 1000 feet or
more thick.

OK, that makes some sense. But I'd have preferred to see the landmass still
outlined separately from the shelves.

It is on this map.
http://nsidc.org/data/seaice_index/i...tent_hires.png

One might expect the Antarctic continent to be surrounded by sea-ice stretching out to a line of latitude in winter and withdrawing to another higher line of latitude in summer. But Earth Science is not like that. Moreover, over recent years the Arctic sea ice has got less while the Antarctic sea ice has increased. But as I said that mainly applies only in the Weddel Sea.

We live in interesting times!

On Sat, 28 Feb 2015 18:04:21 -0000
"General" wrote:

"Alastair" wrote in message
...

I can't see and Antarctic sea ice on the page you linked

Sorry, I skipped a couple of short steps: Click on the blue bar below
the map images that says 'Antarctic Daily Images' and then on
left-hand map image to enlarge that.

but this map shows the current state of sea ice in the Antarctic.
http://polar.ncep.noaa.gov/seaice/sh.html

I guess that's a different representation of the same thing

And here's another one showing charts of Arctic and Antarctic ice in
greater detail (after you click on the appropriate map):
http://www.iup.uni-bremen.de:8084/amsr2/



The mass you mention is an island of sea ice that has formed during
the SH summer melt.

That's pretty odd though isn't it? Perhaps not, but it just seems
unlikely. How big is that 'island' - the size of Tasmania or
something - difficult to get a sense of scale? It's not like it's
just a big iceberg. And how/why has it calved off like that rather
than melting from the ocean edge? That's what caught my curiosity.

It's just an area of ice floes that have been separated from the rest
by the action of wind and current.


Yes, the ice shelf is mapped as part of the Antarctic land mass. Sea
ice is a few feet thick and reforms each year. Ice shelves are about
1000 feet or more thick.

OK, that makes some sense. But I'd have preferred to see the landmass
still outlined separately from the shelves.


Yes, that would have been more useful. All I can suggest is to compare
those ice charts with this map of Antarctica which shows the land and
ice shelves.
http://www.mapsofworld.com/antarctica/

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
The brain is a wonderful organ. It starts working the moment you get
up and does not stop until you get into the office. – ROBERT FROST
Posted with Claws: http://www.claws-mail.org/

On Saturday, 28 February 2015 21:01:02 UTC, Graham P Davis wrote:
On Sat, 28 Feb 2015 18:04:21 -0000
"General" wrote:

OK, that makes some sense. But I'd have preferred to see the landmass
still outlined separately from the shelves.


Yes, that would have been more useful. All I can suggest is to compare
those ice charts with this map of Antarctica which shows the land and
ice shelves.
http://www.mapsofworld.com/antarctica/

Graham,

The ice shelves are shown in dark grey on a map you linked:
http://www.iup.uni-bremen.de:8084/am..._AMSR2_nic.png

Cheers, Alastair.

On Friday, February 27, 2015 at 5:49:38 PM UTC, General wrote:
Just idle curiosity, but can anyone who understands these things kindly
explain:

If I look at the map of _Antarctic_ sea ice (not the graph, the map) at:

http://nsidc.org/arcticseaicenews/

then I'm looking at the Ross Sea - the major inlet right below the S pole:

1. What is the mass of ice apparently floating away from the continent - it
looks huge but completely unconnected to and some considerable distance from
the nearest coastline.

2. What's happened to the Ross Ice Shelf? Isn't that meant to fill a large
area of the Ross Sea? But the median extent line for what is presumably the
minimum ice extent at about this time of year shows largely open water for
the Ross Sea. Or is the ice shelf drawn to be part of the Antarctic land
mass in this presentation?

(Not uninteresting looking at this map: much of the slight excess of
Antarctic sea ice seems to concentrated in the Weddell Sea for some reason,
whereas the coastal area from the Peninsula round to the Ross Sea seems well
below 'normal'. Looks like a very marked change away from the median
distribution, or is this just a one-year picture - ie every year shows a
different distribution and this just happens to be the picture this year?)

Is there an archive to see if it an annual occurrence?

"Graham P Davis" wrote in message
news:20150228210100.740d6c25@linux-pkou...

And here's another one showing charts of Arctic and Antarctic ice in
greater detail (after you click on the appropriate map):
http://www.iup.uni-bremen.de:8084/amsr2/

====================================

Thanks, that's clearly a more detailed and informative representation. The
grid shows the size of the separated ice mass at roughly 5° longitude by 5°
latitude (albeit at near polar latitudes), but still a pretty sizeable area,
so something like the UK in size would that be? (Or not - can't quickly get
a sense of how much smaller in area each 5x5 grid 'square' at eg 70°S is
compared to mid-latitudes?)

But the colour scheme does show, as Graham noted, that the overall area is
much more heterogeneous in terms of ice density that the simplistic map in
my original nsidc link suggested, with a substantial proportion in the range
50-75% ice concentration rather than as a single solid ice mass. But still
there remains a large core to the 'island' which is at or close to 100%.

I'm still curious as to what forces caused this ice island seemingly to
fracture along such a long southerly boundary so that it could float free.
Is this just a natural wind/current/weather phenomenon or could there be
some eg volcanic heating from underneath? Or something like a discrete
warmer (relatively!) current of water running below the surface maybe at the
boundary of the ice shelf and the sea ice? Or is it a chunk of ice shelf
that's calved off?

On Sun, 1 Mar 2015 01:52:24 -0800 (PST)
Alastair wrote:

On Saturday, 28 February 2015 21:01:02 UTC, Graham P Davis wrote:
On Sat, 28 Feb 2015 18:04:21 -0000
"General" wrote:

OK, that makes some sense. But I'd have preferred to see the
landmass still outlined separately from the shelves.


Yes, that would have been more useful. All I can suggest is to
compare those ice charts with this map of Antarctica which shows
the land and ice shelves.
http://www.mapsofworld.com/antarctica/

Graham,

The ice shelves are shown in dark grey on a map you linked:
http://www.iup.uni-bremen.de:8084/am..._AMSR2_nic.png


Yes, I thought that was the case but regarded it as a bit misleading
since Tierra del Fuego would then appear to be an ice shelf. ;-)

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
The brain is a wonderful organ. It starts working the moment you get
up and does not stop until you get into the office. – ROBERT FROST
Posted with Claws: http://www.claws-mail.org/