Today seems to be the first day in this current melt season that sees an
indication that the minimum ice extent may have been reached (at around 3.5
million sqkm according to the NSIDC measure - see
http://nsidc.org/arcticseaicenews/ and, as has already been highlighted,
breaking the previous minimum by a wide margin). It's possible of course
that this is a temporary lull in net melting and that there may be a further
downtick in extent over the next several days but, unsurprisingly given that
we're well into September now, the final minimum can't be too far away.

The Northern sea passage seems to have open for several weeks now. The NW
passage is probably also open, with some careful navigation at least, but
it's a little difficult to tell from the published extent maps because
there's clearly some fragmented ice still around in the relevant channels of
the Canadian Archipelago eg to the south of Devon Island.

JGD

On Sat, 8 Sep 2012 16:16:37 +0100
"johnd" wrote:

Today seems to be the first day in this current melt season that sees
an indication that the minimum ice extent may have been reached (at
around 3.5 million sqkm according to the NSIDC measure - see
http://nsidc.org/arcticseaicenews/ and, as has already been
highlighted, breaking the previous minimum by a wide margin). It's
possible of course that this is a temporary lull in net melting and
that there may be a further downtick in extent over the next several
days but, unsurprisingly given that we're well into September now,
the final minimum can't be too far away.

I think it's a bit early to be suggesting we may have reached the
minimum extent just based on one day of flat-lining. I pointed out a few
days ago elsewhere that things may stall for a while due to change in
wind patterns. I think we've normally got about another week of slow
decline, possibly two if it goes along the lines of 2007.


The Northern sea passage seems to have open for several weeks now.
The NW passage is probably also open, with some careful navigation at
least, but it's a little difficult to tell from the published extent
maps because there's clearly some fragmented ice still around in the
relevant channels of the Canadian Archipelago eg to the south of
Devon Island.


The channel to the south of Devon Island is almost always the first to
be clear of ice - last year by the and of June - so, although this year
looked late, I doubt there's ice there. I suspect what looks like ice
is an artefact associated with the problems Windsat has with coastal
areas. There's also "clearly some fragmented ice" in the Gulf of
Finland! ;-)
Roll on AMSR-2!



--
Graham Davis, Bracknell, Berks. E-mail: change 'boy' to 'man'
"A neighbour put his budgerigar in the mincing machine and invented
shredded tweet." - Chic Murray
openSUSE Linux: http://www.opensuse.org/en/

On Sep 8, 6:26*pm, Graham P Davis wrote:
On Sat, 8 Sep 2012 16:16:37 +0100

"johnd" wrote:
Today seems to be the first day in this current melt season that sees
an indication that the minimum ice extent may have been reached (at
around 3.5 million sqkm according to the NSIDC measure - see
http://nsidc.org/arcticseaicenews/*and, as has already been
highlighted, breaking the previous minimum by a wide margin). It's
possible of course that this is a temporary lull in net melting and
that there may be a further downtick in extent over the next several
days but, unsurprisingly given that we're well into September now,
the final minimum can't be too far away.

I think it's a bit early to be suggesting we may have reached the
minimum extent just based on one day of flat-lining. I pointed out a few
days ago elsewhere that things may stall for a while due to change in
wind patterns. I think we've normally got about another week of slow
decline, possibly two if it goes along the lines of 2007.



The Northern sea passage seems to have open for several weeks now.
The NW passage is probably also open, with some careful navigation at
least, but it's a little difficult to tell from the published extent
maps because there's clearly some fragmented ice still around in the
relevant channels of the Canadian Archipelago eg to the south of
Devon Island.

The channel to the south of Devon Island is almost always the first to
be clear of ice - last year by the and of June - so, although this year
looked late, I doubt there's ice there. I suspect what looks like ice
is an artefact associated with the problems Windsat has with coastal
areas. There's also "clearly some fragmented ice" in the Gulf of
Finland! *;-)
Roll on AMSR-2!

--
Graham Davis, Bracknell, Berks. E-mail: change 'boy' to 'man'
"A neighbour put his budgerigar in the mincing machine and invented
*shredded tweet." - Chic Murray
openSUSE Linux:http://www.opensuse.org/en/

'There's also "clearly some fragmented ice" in the Gulf of
Finland! ;-) '
There certainly is!
They serve a very nice Vodka Cloudberry on ice on the ferries from
Helsinki to Tallinn, and also Helsinki to Stockholm.
Personal experience.
:--))

Len
Wembury

On Sep 8, 7:23*pm, Len Wood wrote:
On Sep 8, 6:26*pm, Graham P Davis wrote:





On Sat, 8 Sep 2012 16:16:37 +0100

"johnd" wrote:
Today seems to be the first day in this current melt season that sees
an indication that the minimumiceextent may have been reached (at
around 3.5 million sqkm according to the NSIDC measure - see
http://nsidc.org/arcticseaicenews/*and, as has already been
highlighted, breaking the previous minimum by a wide margin). It's
possible of course that this is a temporary lull in net melting and
that there may be a further downtick in extent over the next several
days but, unsurprisingly given that we're well into September now,
the final minimum can't be too far away.

I think it's a bit early to be suggesting we may have reached the
minimum extent just based on one day of flat-lining. I pointed out a few
days ago elsewhere that things may stall for a while due to change in
wind patterns. I think we've normally got about another week of slow
decline, possibly two if it goes along the lines of 2007.

The Northernseapassage seems to have open for several weeks now.
The NW passage is probably also open, with some careful navigation at
least, but it's a little difficult to tell from the published extent
maps because there's clearly some fragmentedicestill around in the
relevant channels of the Canadian Archipelago eg to the south of
Devon Island.

The channel to the south of Devon Island is almost always the first to
be clear ofice- last year by the and of June - so, although this year
looked late, I doubt there'sicethere. I suspect what looks likeice
is an artefact associated with the problems Windsat has with coastal
areas. There's also "clearly some fragmentedice" in the Gulf of
Finland! *;-)
Roll on AMSR-2!

--
Graham Davis, Bracknell, Berks. E-mail: change 'boy' to 'man'
"A neighbour put his budgerigar in the mincing machine and invented
*shredded tweet." - Chic Murray
openSUSE Linux:http://www.opensuse.org/en/

'There's also "clearly some fragmentedice" in the Gulf of
Finland! *;-) *'
There certainly is!
They serve a very nice Vodka Cloudberry oniceon the ferries from
Helsinki to Tallinn, and also Helsinki to Stockholm.
Personal experience.
:--))

Len
Wembury

It's generally the case that Arctic ice reaches its minimum in mid-
September. I wonder if this will still be the case in future years?.
Rather than staying just above freezing, there must be appreciable
warming of the Arctic Ocean now that areas of it are ice-free for
considerably longer than previously. One would expect this latent heat
to delay the time at which the heat balance goes negative. Any
thoughts?

On 14/09/2012 10:06, haaark wrote:
On Sep 8, 7:23 pm, Len Wood wrote:
On Sep 8, 6:26 pm, Graham P Davis wrote:

On Sat, 8 Sep 2012 16:16:37 +0100

"johnd" wrote:
Today seems to be the first day in this current melt season that sees
an indication that the minimumiceextent may have been reached (at
around 3.5 million sqkm according to the NSIDC measure - see
http://nsidc.org/arcticseaicenews/ and, as has already been
highlighted, breaking the previous minimum by a wide margin). It's
possible of course that this is a temporary lull in net melting and
that there may be a further downtick in extent over the next several
days but, unsurprisingly given that we're well into September now,
the final minimum can't be too far away.

I think it's a bit early to be suggesting we may have reached the
minimum extent just based on one day of flat-lining. I pointed out a few
days ago elsewhere that things may stall for a while due to change in
wind patterns. I think we've normally got about another week of slow
decline, possibly two if it goes along the lines of 2007.

The Northernseapassage seems to have open for several weeks now.
The NW passage is probably also open, with some careful navigation at
least, but it's a little difficult to tell from the published extent
maps because there's clearly some fragmentedicestill around in the
relevant channels of the Canadian Archipelago eg to the south of
Devon Island.

The channel to the south of Devon Island is almost always the first to
be clear ofice- last year by the and of June - so, although this year
looked late, I doubt there'sicethere. I suspect what looks likeice
is an artefact associated with the problems Windsat has with coastal
areas. There's also "clearly some fragmentedice" in the Gulf of
Finland! ;-)
Roll on AMSR-2!

--
Graham Davis, Bracknell, Berks. E-mail: change 'boy' to 'man'
"A neighbour put his budgerigar in the mincing machine and invented
shredded tweet." - Chic Murray
openSUSE Linux:http://www.opensuse.org/en/

'There's also "clearly some fragmentedice" in the Gulf of
Finland! ;-) '
There certainly is!
They serve a very nice Vodka Cloudberry oniceon the ferries from
Helsinki to Tallinn, and also Helsinki to Stockholm.
Personal experience.
:--))

It's generally the case that Arctic ice reaches its minimum in mid-
September. I wonder if this will still be the case in future years?.
Rather than staying just above freezing, there must be appreciable
warming of the Arctic Ocean now that areas of it are ice-free for
considerably longer than previously. One would expect this latent heat
to delay the time at which the heat balance goes negative. Any
thoughts?

I expect it will slightly but once you got past 21/9 there will be a
small but gradually increasing area in permanent twilight and then total
darkness and increasingly longer nights. It will clearly take some time
for the sea to cool down again so I would be more inclined to expect the
refreezing to be delayed rather than the actual ice minimum.

I doubt if you can see anything in a single years behaviour but trends
over a couple of decades are probably a reasonable indicator.

A single event could just be a fluke combination of weather conditions
but if it happens again and again then it is increasingly likely that it
is part of the predicted Arctic warming trend.

The really tricky question is since the one year old thinner ice will in
future cover a larger proportion than the thicker more robust stuff how
fast will the melting be in the next year and subsequent ones.

--
Regards,
Martin Brown

haaark wrote:

It's generally the case that Arctic ice reaches its minimum in mid-
September. I wonder if this will still be the case in future years?.
Rather than staying just above freezing, there must be appreciable
warming of the Arctic Ocean now that areas of it are ice-free for
considerably longer than previously. One would expect this latent heat
to delay the time at which the heat balance goes negative. Any
thoughts?

Using the graph at
http://i137.photobucket.com/albums/q...nStepMelts.png
there does not seem to have been any trend in the date of minimum ice extent
at least since 1979, when the minimum ice extent was about twice this year's
value.

Nevertheless, perhaps one might expect that water in areas that are ice-free
over a longer period than hitherto would become more mixed than before and
the surface layers there would be more salty and have a correspondingly
lower freezing point. I don't know if this is good science though.

Roger

"Roger Smith" wrote in message
...
haaark wrote:

It's generally the case that Arctic ice reaches its minimum in mid-
September. I wonder if this will still be the case in future years?.
Rather than staying just above freezing, there must be appreciable
warming of the Arctic Ocean now that areas of it are ice-free for
considerably longer than previously. One would expect this latent heat
to delay the time at which the heat balance goes negative. Any
thoughts?

Using the graph at
http://i137.photobucket.com/albums/q...nStepMelts.png
there does not seem to have been any trend in the date of minimum ice
extent at least since 1979, when the minimum ice extent was about twice
this year's value.

Nevertheless, perhaps one might expect that water in areas that are
ice-free over a longer period than hitherto would become more mixed than
before and the surface layers there would be more salty and have a
correspondingly lower freezing point. I don't know if this is good
science though.

Roger

From that graph, the latest minimum was also the least in 2007. The
question is: was the least minimum the result of it melting for longer or
was the meltng for longer caused by the least minimum? The latter makes more
sense to me and so I expect the minimum to happen later this month.

Cheers, Alastair.

"Alastair McDonald" wrote in message
...

"Roger Smith" wrote in message
...
haaark wrote:

It's generally the case that Arctic ice reaches its minimum in mid-
September. I wonder if this will still be the case in future years?.
Rather than staying just above freezing, there must be appreciable
warming of the Arctic Ocean now that areas of it are ice-free for
considerably longer than previously. One would expect this latent heat
to delay the time at which the heat balance goes negative. Any
thoughts?

Using the graph at
http://i137.photobucket.com/albums/q...nStepMelts.png
there does not seem to have been any trend in the date of minimum ice
extent at least since 1979, when the minimum ice extent was about twice
this year's value.

Nevertheless, perhaps one might expect that water in areas that are
ice-free over a longer period than hitherto would become more mixed than
before and the surface layers there would be more salty and have a
correspondingly lower freezing point. I don't know if this is good
science though.

Roger

From that graph, the latest minimum was also the least in 2007. The
question is: was the least minimum the result of it melting for longer or
was the meltng for longer caused by the least minimum? The latter makes
more sense to me and so I expect the minimum to happen later this month.

Cheers, Alastair.

What I should have written is:

From the graph it can be seen that 2007 was the year with the latest
minimum. It was also the year with the least minimum ice extent. The
question is did the late minimum cause the least minimum, or did the least
minimum cause the late minimum.

I suspect it is the latter. For the sea surface temperature to fall to -10C,
the temperature as which sea ice forms, then it has to be cooled by winds at
tempertures at of below -10C. These winds cannot form over unfrozen sea but
can form over ice. So, if the area of ice is small, then the cold air masses
will form more slowly, and the refreeze will begin later i.e. when the air
temperature over the smaller ice pack has fallen to -15 C.

Hope this makes more sense than by previous post.

Cheers, Alastair.

On Fri, 14 Sep 2012 17:59:41 +0100
"Alastair McDonald" wrote:

For the sea surface temperature to fall to -10C,
the temperature as which sea ice forms,

Eh? The temperature at which sea-ice forms is about -1.8C. Not sure
where this -10C came from.

--
Graham Davis, Bracknell, Berks. E-mail: change 'boy' to 'man'
"A neighbour put his budgerigar in the mincing machine and invented
shredded tweet." - Chic Murray
openSUSE Linux: http://www.opensuse.org/en/

Graham P Davis wrote:
On Fri, 14 Sep 2012 17:59:41 +0100
"Alastair McDonald" wrote:

For the sea surface temperature to fall to -10C,
the temperature as which sea ice forms,

Eh? The temperature at which sea-ice forms is about -1.8C. Not sure
where this -10C came from.

Notwithstanding that apparent error, Alastair seems to be stating that new
ice will only form if the wind is blowing from adjacent ice masses (or land
at sub-zero temperatures). All that this means is that in the autumn the
existing sea ice will expand outwards, rather than that new, isolated areas
of ice will form, and I would not disagree with that. But it says nothing
about any link between the area of sea ice and the date on which refreezing
will start to occur.

As an aside, and using the same argument, if the sea-ice disappeared
entirely, then new ice would only form initially adjacent to very cold land
areas.

Roger