319 replies to this topic

[pottyprof]

It's that time of year when we start to watch how the Arctic creates it's new winter coat. 2011 sees us close to the record minimum achieved in 2007. At some point over the next couple of weeks there should be the call of extent minima. Currently we are seeing a few tentative signs of growth but will we see further reductions before we know for sure the the refreeze has commenced?

I will be leaving the melt season thread open until we are sure the freeze has started so please finish any discussion about melt in that thread. --> http://forum.netweat...ice-discussion/


Enjoy..!!

[Gray-Wolf]

Well here we are again!

As with last year I would expect 're-freeze' to be of interest to us all. I feel that points to watch for are how long certain areas remain ice free (remember Hudson last year?) and how much transport from the basin the winter provides.
We may (eventually) have the Cryosat2 data on ice thickness and this should prove very informative as the season progresses.
Let's all have fun and try and keep 'bickering/sniping' to a minimum?

[4wd]

It's looking like minimum extent was on the 9th, with steady gains since then making it seem unlikely there'll be a late dip.
How does that compare to recent years?
It seems relatively early.

[BornFromTheVoid]

4wd, on 15 September 2011 - 11:35 , said:

It's looking like minimum extent was on the 9th, with steady gains since then making it seem unlikely there'll be a late dip.
How does that compare to recent years?
It seems relatively early.

On my phone at the moment so don't have the data to hand, but I think around '95 was the last time there was an earlier minimum. I can post up a list of the minima dates since '79 this evening if you like...

[BornFromTheVoid]

Largest daily increase (65,156km2) for the first half of September since 2003 which had a daily gain of nearly 75k on the 13th. Still quite impressive and unexpected I have to say.

[BornFromTheVoid]

A 20,000km2 loss on the IJIS site, but somewhere around 250,000km2 gained over the last 2 days on Cryosphere today.

Been working on creating some kind of " Arctic Dipole" index recently as part of my dissertation work this year.
I used 2 sets of co-ordinates [81.67, -93.0]-[80.21, 91.8] + [83.28, -41.8]-[80.22, 23.2], and the esrl daily composite mean air pressure maps.
The co-ordinates roughly equate to these locations
81.67, -93.0 = N Coast Ellesmere Island
80.21, 91.8 = Severnaya Zemlya

83.28, -41.8 = N Greenland Coast
80.22, 23.2 = NE Svalbard

I got averaged monthly air pressure maps from '79 to present, April-September (the scope of my project) and took the second locations air pressure from the first for each set, then added the 2 together for each month, giving a single positive or negative number. A positive figure would equate to higher pressure on the Canadian side than the Eurasian side, and vice versa.
Anyway, these are the figures I got



Some interesting results anyway. A huge increase in positive figures from around 2007. Also, despite 2007 having the largest overall dipole for the melt period of the year, it only had 1 exceptional month, August.
Also, 2011, so far, looks like it will have the first negative September since 2000, which may have contributed to the possible early minimum.

Will be doing some further analysis over the coming weeks and will post up anything interesting.

[Gray-Wolf]

Some more 'Cud to chew' as regards how much our current understanding of climate is concerned (as per N.S.'s post on the other thread)

"That contradicts computer model simulations, also used to predict future temperatures, that suggest winter temperatures were below freezing even in the unexplained hothouse period that lasted between 50,000 and 200,000 years ago during the Eocene epoch."

http://www.abc.net.a.../26/2724114.htm

[bobbydog]

are there any comparison graphs/charts showing ice extent for the year to date?

[Gray-Wolf]

http://sites.google....icseaicegraphs/

you'll find a load on the above and links to the 'Mother site' to help you explore further.

[bobbydog]

Gray-Wolf, on 27 September 2011 - 07:38 , said:

http://sites.google....icseaicegraphs/

you'll find a load on the above and links to the 'Mother site' to help you explore further.

thanks, that'll do nicely!

[jethro]

So, how's it going up North?

I confess to being slightly disappointed that the re-freeze season isn't greeted with the same enthusiasm and scrutiny as the melt season - surely it's equally as important.

[songster]

Bit too early to say. We're slightly above the minimum, but not far, bumping along neck and neck with 2008 for second lowest on record, depending which dataset you look at. The re-freeze doesn't really set in until October/November. At that point we'll know how well the areas in Kara/Laptev that thawed early are able to shed the excess accumulated heat. It may be a comparatively rapid return to the pre-2007 re-freeze curve (as in 2008), or it may be substantially delayed (as in 2007, 2009 and 2010).

[Kiwi]

Reading today in October edition of Geographical Magazine that sea ice cover in the Arctic may stabilise or even expand over the next few decades.
This is based on computer modelling undertaken by the US National Center for Atmospheric research.

[jethro]

Thanks for the input folks.

Over in this thread: http://forum.netweat...2/page__st__280 post 296, page 15 there is a graph showing the current re-freeze level - doesn't look too bad to me.

Kiwi, on 29 September 2011 - 09:37 , said:

Reading today in October edition of Geographical Magazine that sea ice cover in the Arctic may stabilise or even expand over the next few decades.
This is based on computer modelling undertaken by the US National Center for Atmospheric research.

That's good news; do they say what they base that on? Solar, ocean currents etc???

[Kiwi]

jethro, on 29 September 2011 - 10:57 , said:

That's good news; do they say what they base that on? Solar, ocean currents etc???

Apparently "variations in atmospheric conditions, such as wind patterns, due to other climatic changes were the most likely explanation"

[jethro]

Kiwi, on 29 September 2011 - 11:06 , said:

Apparently "variations in atmospheric conditions, such as wind patterns, due to other climatic changes were the most likely explanation"

Cheers Kiwi.

You've piqued my curiosity, hopefully I'll find time to read more on what exactly they mean by 'due to other climatic changes' - what changes and why....

[loafer]

Perhaps they realised that their existing models predicting warming weren't being proven by real life events and changed the variables...

[Thundery wintry showers]

I doubt this, given that the Arctic has warmed appreciably over the last decade in particular. My guess is that they are suspecting that atmospheric circulation contributed significantly to the warming and ice melt, and are expecting the atmospheric circulation to revert back to a colder type.

[loafer]

Interesting. Does that change in atmospheric circulation, I wonder, have implications for our more local climate?

Indeed, is it already showing it's effect with changes to the seasons and two harsh winters?

Perhaps I should answer my own question as I just read the relevant piece on their website. http://www2.ucar.edu...en-resume-again

Basically it says that it could just as easily increase as decrease in the short term, as you move to 10 year horizon, the variations of outcome up and down get more extreme (compounding effect on model variables, anyone?!), but in the long term the greenhouse gases melt it all.

Edited by loafer, 29 September 2011 - 16:46 .

[JASON221]

Greenhouse effect is getting worse

Edited by JASON221, 30 September 2011 - 09:52 .