Ice Free Arctic

  • Thread starter Xnn
  • Start date
  • #26
sylas
Science Advisor
1,646
6
Here is an abstract of the 2009 Wang paper that predicts a nearly sea ice free Arctic by September 2037. It is based on 6 IPCC physics based models. Also, the the top quartile prediction is 2028.
This is more credible than a projection only, IMO, with the proviso of course that sea ice modeling is hard.

We're going to have to finish up here soon, unfortunately, but it may be worth leaving the thread with a link to [post=2374600]msg #23[/post] of thread "State of the Climate", where mheslep gave a link to the Sea Ice Outlook project at the "Arctic Research Consortium US". This was basically a competition between research groups to predict sea ice change one year in advance. A short term prediction is a rather different beast, subject to larger variations with local effects of wind and current obscuring the trends that are in many ways easier to model: but the failings of the models were intriguing.

In brief; loss of summer ice by 2040 is reasonably well founded; but given the uncertainties it might be rather more, or less, time required.

So, I feel confident that my projection is about the same as that obtained from the physics based models.
Yes, that gives a lot more weight to the projections. I'm sure all the modelers will be continuing to look at the matter and refine their models for some time yet. The one consistent feature of applying physics to the problem is that the loss of ice is not merely an aberration, but a real physically well founded consequence of changes that will be continuing to take place for many years yet.

Cheers -- sylas
 
  • #27
907
2
I look forward to fishing at the North Pole in July 2040.
 
  • #28
Xnn
555
0
Here's an image with a projection drawn using the Cyrosphere data.
It is in rough agreement with Wang's published prediction of 2037.

attachment.php?attachmentid=22932&stc=1&d=1262941926.jpg
 

Attachments

  • #29
sylas
Science Advisor
1,646
6
Here's an image with a projection drawn using the Cyrosphere data.
It is in rough agreement with Wang's published prediction of 2037.
Can you be more specific as to what data source you are using? Different groups define the extent in different ways, and the numbers in your graph are not from the definitions I've normally used.

Your graph pretty obviously omits the 2009 figure, which recovered quite a bit from the record minima of 2007/2008, which show up on the graph pretty clearly; but 2009 is not there. Including the data from Sept 2009 makes the match with Wang rather less good... and note also that Wang's group was part of the prediction group I mentioned in the previous post. They underestimated the extent in 2009, as did everyone else; although as usual the number in a given year is in part due to short term changes at the particular weeks of the minimum, not only long term trend. Note that the effort reported must have used different definitions from the numbers in your graph.

Another common source is the National Snow and Ice Data Center (linking to the Oct 2009 report), in which minimum summer extent shows as follows:
20091005_Figure3_thumb.png
(link to full size original)

I wouldn't discount Wang's expectations, but neither would I bet a lot of money on their proposed date. The trend has been substantially faster than estimated in the IPCC 4AR, but Wang's prediction is currently looking to be bit too far the other way.

It's best, I think, to acknowledge that Arctic summer minimum ice extent is hard to predict, and that any specific prediction is tentative, given the limits of models being used. The models do indicate that the decline is real physically founded trend that will be continuing into the future; but quantifying the models to the level of a specific year is... rash.

Cheers -- sylas
 
  • #30
Xnn
555
0
I use the UIUC Cryosphere site. Specifically the following diagram (summer):

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg

I see they report different values than the NSIDC and don't have a value for 2009.

For 2007, NSIDC reports 4.3 Mkm^2
For 2007, UIUC reports 5.5 Mkm^2

The NSIDC chart shows a decline of about 2.5Mkm^2 over the last 30 years.
The UIUC chart shows a decline of about 3Mkm^2 over the last 30 years.

From the above data, it does not appear that the Arctic would be ice free within 30 years. So, for Wang's and others physics based models to be correct there will have to be an acceleration from the rate of ice loss over the last 30 years.

While the 2009 minimum extent was more than 2007/2008, it does not appear to be substantially greater than the trend line.

The differences between the 2 sources of sea ice extent data suggest to me that they may have different definitions of sea ice.
 
  • #31
8
0
For Wang and others to be correct we need an amplification. And an amplification does appear to be underway. I was impressed with this paper that I was a peer reviewer for.
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf. The emphasis is on observed temperature anomalies and increased heat flux from the open ocean from late summer-early winter.
 
  • #32
sylas
Science Advisor
1,646
6
I use the UIUC Cryosphere site. [...]

I see they report different values than the NSIDC and don't have a value for 2009.

For 2007, NSIDC reports 4.3 Mkm^2
For 2007, UIUC reports 5.5 Mkm^2

The NSIDC chart shows a decline of about 2.5Mkm^2 over the last 30 years.
The UIUC chart shows a decline of about 3Mkm^2 over the last 30 years.

From the above data, it does not appear that the Arctic would be ice free within 30 years. So, for Wang's and others physics based models to be correct there will have to be an acceleration from the rate of ice loss over the last 30 years.

While the 2009 minimum extent was more than 2007/2008, it does not appear to be substantially greater than the trend line.

The differences between the 2 sources of sea ice extent data suggest to me that they may have different definitions of sea ice.
I believe the cryosphere today website defines "extent" as the area that has 50% cover or more of ice -- could be 30%, I am not sure. NSIDC uses "extent" as area with 15% cover or more. It may just be me, but I have found it hard to get the information from cryosphere today, by comparison with NSIDC.

I did a bit of private analysis on this last year when the blogosphere suddenly went wild with a bunch of claims about scientific malfeasance based on an exercise by Steve Goddard in the UK counting pixels on images to support some wild accusations. Goddard himself learned from the experience and accepted useful corrections from the NSIDC. But the whole brouhaha did show very clearly just how quick many people are to jump on claims about how climate scientists are all involved in some hoax given even the silliest pretext.

For background on the story, see this poster session on the whole event by Walter N. Meier, Stephanie Renfrow, and Mark Serreze of the NSIDC. Striking back: A case study in addressing a skeptic’s public assertions about sea ice data.

For Wang and others to be correct we need an amplification. And an amplification does appear to be underway. I was impressed with this paper that I was a peer reviewer for.
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf. The emphasis is on observed temperature anomalies and increased heat flux from the open ocean from late summer-early winter.
Quite right! You can see indications of an acceleration in the data, very roughly around 1996/1997. The acceleration is not quite as strong as Wang's proposal, I think, but some acceleration is a consistent feature nearly all physically based models. The graph I provided from NSIDC has a single regression line from 1978, which if extended as a linear trend would indicate no summer sea ice in the Arctic by the end of the century.... but there's an inflection in that graph which would mean any non-linearity makes it likely to be a lot sooner. I wonder if Wang's work relies too much on the 2007/2008 minimum. The abstract states that this minimum is used as a "starting point", but I think the data shows them to be anomalous, even given the accelerating trend.

So... an essentially ice free summer as soon as 2037? Perhaps. This estimate is an average of a number of models, some of which suggest even sooner and others which suggest a bit later. By 2070? Very likely. By 2100? Bet on essentially ice free summers before this. Ice free in this context still allows for isolated floating sea ice and for ice around some coastal margins.

Cheers -- sylas
 
  • #33
34
0
I've spent a bit of time working with the sea ice extent numbers.

The satellite sea ice extent data actually goes back to 1972 but for whatever reason, it has not been matched up/reconcilled to the satellite data starting in 1979 provided by the newer post-1979 satellites.

I've matched up the daily satellite-estimated sea ice extent estimates provided by Jaxa with the Nasa Team algorithm daily data which goes back to 1979. Jaxa used the Nasa team algorithm in developing their algorithm so they are reasonably consistent.

http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

The main point is that, throughout the year, there is some variation in sea ice extents but there is a seasonal range that has not varied as much as the September minimum numbers make it look.

This chart is not the last word and some adjustments were required to match up the two records, but it does provide a little better perspective on the Arctic/NH sea ice extent. The two lowest sea ice extent years (2007 and 2008) and the two highest sea ice extent years (1980 and 1996) are highlighted as well as 2009 (the red line).

There is still a lot of change required before the day 255 (September 12th, the average date of the minimum) sea ice extent hits Zero.

http://img23.imageshack.us/img23/1255/dailyseidec31.png [Broken]
 
Last edited by a moderator:
  • #34
sylas
Science Advisor
1,646
6
I've spent a bit of time working with the sea ice extent numbers.

The satellite sea ice extent data actually goes back to 1972 but for whatever reason, it has not been matched up/reconcilled to the satellite data starting in 1979 provided by the newer post-1979 satellites.

I've matched up the daily satellite-estimated sea ice extent estimates provided by Jaxa with the Nasa Team algorithm daily data which goes back to 1979. Jaxa used the Nasa team algorithm in developing their algorithm so they are reasonably consistent.
I think there are problems with your match up, and that you may be giving values for sea ice minima prior to 2002 that are too low. The lack of an existing match up record is very probably because there are all kinds of difficulties with doing a match up across different satellites and time periods, and such a graph is known to be misleading.

Given the rapidly rising temperature records in the Arctic, it is surprising to see bits of the graph dropping below the 2009 minimum. I think this indicates inaccuracies in how you have merged data from different sources.

Cheers -- sylas
 
  • #35
34
0
I think there are problems with your match up, and that you may be giving values for sea ice minima prior to 2002 that are too low. The lack of an existing match up record is very probably because there are all kinds of difficulties with doing a match up across different satellites and time periods, and such a graph is known to be misleading.

Given the rapidly rising temperature records in the Arctic, it is surprising to see bits of the graph dropping below the 2009 minimum. I think this indicates inaccuracies in how you have merged data from different sources.

Cheers -- sylas
Yes, there is some problems in the match-up. The old NasaTeam data has more of a dip at the minimum (compared to Jaxa's algorithm) than the rest of the year. I just left it the way it turned out but another adjustment could have been applied for that. 2009 should be the third lowest year.

The point is when one looks over the whole year seasonal cycle, there is not as much decline as the "one-day" minimum makes it look. There can also be unusual increases in the trends like the 1996 (blue line) shows.

I guess my other point is that the NSIDC or some other entity should spend some time matching up these older records and producing charts like the above so we can have a better understanding.
 
  • #36
Xnn
555
0
For Wang and others to be correct we need an amplification. And an amplification does appear to be underway. I was impressed with this paper that I was a peer reviewer for.
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf. The emphasis is on observed temperature anomalies and increased heat flux from the open ocean from late summer-early winter.
mspelto;

Wow!
It is really great that we have a professional on board.
Most of us are just motivated amateurs with technical backgrounds.

From the paper:
To summarize: 1) Starting in the late 1990s and relative to
the 1979–2007 time period, Arctic Ocean SAT anomalies in
the NCEP reanalysis turned positive in autumn and have subsequently
grown; 2) Consistent with an anomalous surface
heating source, development of the autumn warming pattern
aligns with the observed reduction in September sea ice extent,
and temperature anomalies strengthen from the lower
troposphere to the surface; 3) Recent autumn warming is
stronger in the Arctic than in lower latitudes; 4) Recent low
level warming over the Arctic Ocean is less pronounced in
winter when most open water areas have refrozen; 5) There
is no enhanced surface warming in summer; 6) Conclusions
1–5 hold for both the NCEP and JRA-25 reanalyses, the major
difference being that temperature anomalies in JRA-25
are somewhat smaller.
One of the things that has been noted earlier in this forum is the
increasing seasonality of the Arctic sea ice. This seems especially pronounced over the last 3 seasons. The greatest deviation has been generally occurring in September. Sometimes, it occurs after sunset. Then there is a rapid rebound towards or sometimes just above the long term average.
 
  • #37
Xnn
555
0
I believe the cryosphere today website defines "extent" as the area that has 50% cover or more of ice -- could be 30%, I am not sure. NSIDC uses "extent" as area with 15% cover or more. It may just be me, but I have found it hard to get the information from cryosphere today, by comparison with NSIDC.
Of course, if we are talking about ice free conditions then even 15% is too high.
However, I can imagine from a data analysis and processing perspective there are reasons to use other values.
 
  • #38
Xnn
555
0
The main point is that, throughout the year, there is some variation in sea ice extents but there is a seasonal range that has not varied as much as the September minimum numbers make it look.
Of course, part of the reason for this is that sea ice is 3 dimensional and we are only looking at it in 2 dimensions. The winter ice thickness is thinner at maximum extent compared to the past than at the season minimum.

In addition, I suspect that seasonal albedo changes are beginning to become a factor.
However, albedo is relatively un-important between Sept 21 to March 21.

So, combine the dimensionality and the albedo factor and the most largest deviation will be occurring around Sept.
 
  • #39
8
0
The main source of the amplification seen is the heat released from the water. Think of a different but related amplification. The Great Lakes famous for their lake effect snows. The snow results from water evaporated and heat lost from the lakes. This snow amplification system shuts off when the lakes freeze. The lakes are still open at this point.
http://www.natice.noaa.gov/pub/ims_gif/DATA/cursnow_usa.gif [Broken]
 
Last edited by a moderator:
  • #40
Skyhunter
I recall a report last October from the NSIDC that attributed the unusually warm Arctic temperatures to the release of latent heat from the phase change from liquid to solid.

[Edit]

On further review, it was the http://nsidc.org/arcticseaicenews/2008/111008.html"

Higher-than-average air temperatures

Over much of the Arctic, especially over the Arctic Ocean, air temperatures were unusually high. Near-surface air temperatures in the Beaufort Sea north of Alaska were more than 7 degrees Celsius (13 degrees Fahrenheit) above normal and the warming extended well into higher levels of the atmosphere. These warm conditions are consistent with rapid ice growth.

The freezing temperature of saline water is slightly lower than it is for fresh water, about –2 degrees Celsius (28 degrees Fahrenheit). While surface air temperatures in the Beaufort Sea region are well below freezing by late September, before sea ice can start to grow, the ocean must lose the heat it gained during the summer. One way the ocean does this is by transferring its heat to the atmosphere. This heat transfer is largely responsible for the anomalously high (but still below freezing) air temperatures over the Arctic Ocean seen in Figure 3. Only after the ocean loses its heat and cools to the freezing point, can ice begin to form. The process of ice formation also releases heat to the atmosphere. Part of the anomalous temperature pattern seen in Figure 3 is an expression of this process, which is generally called the latent heat of fusion.

In the past five years, the Arctic has shown a pattern of strong low-level atmospheric warming over the Arctic Ocean in autumn because of heat loss from the ocean back to the atmosphere. Climate models project that this atmospheric warming, known as Arctic amplification, will become more prominent in coming decades and extend into the winter season. As larger expanses of open water are left at the end of each melt season, the ocean will continue to hand off heat to the atmosphere.
 
Last edited by a moderator:

Related Threads on Ice Free Arctic

  • Last Post
Replies
11
Views
4K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
12
Views
4K
Replies
2
Views
3K
Replies
3
Views
3K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
10
Views
3K
  • Last Post
Replies
10
Views
3K
  • Last Post
Replies
18
Views
8K
Replies
2
Views
2K
Top