Polar Ice

[Gray-Wolf]

I hope I'm not stepping on J1's toes here but we are now past ice max and into the summer melt season so I've opened a new thread to post our observations/news/views on this years melt season as it progresses.

[BornFromTheVoid]

Ice extent up to the 18th is now up to 13,768,594km2, still the highest in the last 8 years and increase of just over 2,000km2 on the 17th.

Rate of melt over the last 10 days is still averaging just over 41,000km2/day, which is roughly average for the time of year and 4th fastest in the last 8, with 2004 fastest with 73,500km2/day and the slowest being 2006 at just 8,500km2/day, all just over the last 10 days.

Once again the gap over the other years has been increasing with 2009 now the closest, but still 207,000km2 off and 2004 being the farthest away having 913,500km2 less. We are now 511,000km2 above the average for the last 8 years.

Overall, the ice is holding up surprisingly well so far this year, considering how warm the arctic was this winter. The true state of the ice won't really be known for another few months at least, but so far so good.

[Gray-Wolf]

Here's an image (Ta! NSIDC) of the currents through the Arctic. Note the ingress through Barents and exit west of Greenland. Once the channels in the Canadian Archipelago are cleared of old perennial/shore ice/shelf ice then you can see the potential for the current to flow faster and remain warmer on it's transit keeping the channels ice free and opening another route (apart from Nares) out of that sector of the Arctic.

Seeing that ice formation was poor through that sector this winter watch for increased flow through there this summer. Also take the odd peep to see how the channels shed the last of the 'old perennial' that had choked them since 07's melt.

If we now look at current SST's (and over the past 4 years this 'anom' has been growing)

you'll see cold surface water at the end of the 'new current'. Eventually this current must 'find', and then join, the main body of cold heading south towards the south Atlantic.

EDIT: I've just found this;

http://www.scientifi...n_bridges_nares

and apart from re-enforcing my own views of what I have seen (regarding Nares) this winter it illustrates well (with MODIS imagery) how we have arrived at this point.

The rapid breakup around the Fram straight is also illustrated and the gentleman poses the possibility of ice loss across the top of Greenland this year with it exiting through Fram (this area used to be solid,impenetrable perennial).

Edited April 19, 2010 by Gray-Wolf

[Gray-Wolf]

That's interesting.

With Davis pretty mobile (and empty!) and Baffin Bay well fractured and mobile (and Nares open all winter) Lancaster Sound is already on the move. With only the remnants of 07's melt (now 2yrs more fragmented/melted) in there the start (eastern end) to the deep water passage through the NW Passage is starting to clear. I believed that this occured in late July through Aug.

With the exit to the Atlantic clearing fast (poor ice year) it is begining to look like the NW Passage will be navigable before Aug this year as it's single year ice/framented bay ice/old perennial remnants will not 'jam' on it's way south.

NSIDC (Mark Serezze) gave a 2 to 3 year 'blockage from 'rubble' from the 07' melt and it looks like he was correct.

The other area to watch is N .Greenland. Should this fragment small enough then it will join the ice in the Nansen Basin (NW Svalbard/Frans Joseph Land) through Fram and into the N. Atlantic.

Could we have a year where we can sail around Greenland?

[SteveB]

I'll be up there with my rubber dingy Gray-wolf

[Gray-Wolf]

The other thing which keeps troubling me is the upcoming hurricane season. It's looking like all the ingredients are there for us to have another busy season and that means a number of 'extra tropical storms' prowling both the Canadian and our side of 'the pond'. The wind and swells that these bring with them could not be worse timed being towards the end of melt season with the remnant ice being most fragile and lots of ice poised to exit the Arctic should the correct wind/current pick them up.

A poor start to the season (in the high arctic), the potential for rapid melt mid season (due to the state of the pack) and the potential for a poor end to the season (stormy at times smashing ice ,moving ice out of the Arctic and mixing the 'open' waters smashing the top layer)

[stewfox]

A poor start to the season (in the high arctic), the potential for rapid melt mid season (due to the state of the pack) and the potential for a poor end to the season (stormy at times smashing ice ,moving ice out of the Arctic and mixing the 'open' waters smashing the top layer)

I suppose the only 'fact' we have at present 13.65 million sq kms up there as of St Georges Day

cf

13.32 2003

12.68 2004

12.97 2005

12.93 2006

12.80 2007

13.10 2008

13.36 2009

The 'potential' for George the Dragon to start firing up and melt some of this annoying ice of course remains

Edited April 24, 2010 by stewfox

[Gray-Wolf]

And so the Arctic ice's toe's feel the edge of the precipice.

All down hill from here.

[jethro]

It's Summer, of course it's downhill from here - come Winter, it'll be an uphill journey.

[Gray-Wolf]

It's Summer, of course it's downhill from here - come Winter, it'll be an uphill journey.

It's the speed of the 'downhill' that might surprise you 'J'.

If I'm right about the ice then the area of poor ice (both in and out of the Arctic circle) dictates a rapid decline over the next 2 months before we even get a chance to see how the central pack is shaping up. I worry that we'll continue on with the rate of decline as the central pack opens up and reveals the areas of poor ice formation over winter.

Then there's the weather up there this summer (forecast 'warmest year' and that new study showing a stat relationship between Low solar activity /H.P.'s over us ,blocking the Atlantic and keeping Canada/parts of the Arctic extra warm) and it's impacts on the 'stable' pack.

[jethro]

It's the speed of the 'downhill' that might surprise you 'J'.

If I'm right about the ice then the area of poor ice (both in and out of the Arctic circle) dictates a rapid decline over the next 2 months before we even get a chance to see how the central pack is shaping up. I worry that we'll continue on with the rate of decline as the central pack opens up and reveals the areas of poor ice formation over winter.

Then there's the weather up there this summer (forecast 'warmest year' and that new study showing a stat relationship between Low solar activity /H.P.'s over us ,blocking the Atlantic and keeping Canada/parts of the Arctic extra warm) and it's impacts on the 'stable' pack.

I suppose it would be futile to say "stop worrying". There's absolutely nothing that anyone of us can do to influence the volume of ice or the weather systems, we're utterly powerless . Observe without fretting is my advice. We're not to blame for the decline in ice, we may have contributed to it but that influence is dwarfed by forces outside our control.

Worrying is a waste of energy IMO.

[cooling climate]

My prediction for the summer Arctic melt season...

Gray Wolf who is becoming more and more isolated in his views and beliefs on the demise of

Arctic ice contrary to what is really happening in the Arctic, will fall silent by the end of the melt

season as another of his woefully poor and totally misguided predictions fail to surface above

a resilient and increasingly healthy Arctic ice pack.

Gray Wolf far more knowledgeable people in this field than us (NSIDC, etc ) were caught out or

jumped to the wrong conclusions following the 2007 melt season, don't let your stubbornness

blind you to the fact to what is happening in the Arctic rather than what you believe should be

happening in the Arctic following the 2007 summer melt and loss of multi- year ice.

Cheers.

[Guest North Sea Snow Convection]

My prediction for the summer Arctic melt season...

Gray Wolf who is becoming more and more isolated in his views and beliefs on the demise of

Arctic ice contrary to what is really happening in the Arctic, will fall silent by the end of the melt

season as another of his woefully poor and totally misguided predictions fail to surface above

a resilient and increasingly healthy Arctic ice pack.

Gray Wolf far more knowledgeable people in this field than us (NSIDC, etc ) were caught out or

jumped to the wrong conclusions following the 2007 melt season, don't let your stubbornness

blind you to the fact to what is happening in the Arctic rather than what you believe should be

happening in the Arctic following the 2007 summer melt and loss of multi- year ice.

Cheers.

Yes daily obsessive doomwatch prophesising, repeating the same mantra day in day out is not a healthy lifestyle. There is more going on out there in life beyond a computer screen and ice and satellite graphics.

And as I have said recently, even if the ice volumes do not have a good season it does not validate any doomwatch prophecy either. The more these are repeated, the less seriously the prophet is taken.

[Gray-Wolf]

Hi C.C. ,J,

When I was little I used to build dams in the local stream (turf and rocks). I'd spend an age building and shoring up but then I'd sit and watch. I couldn't bare take my eyes off it as I wanted to see 'how' the collapse started and the catastrophic breach (and wave) when it came.

The Arctic has become like that to me over the past 15yrs. I'm not worrying about it (the time that we could have done something about it is long gone) but I am fascinated by it as a process.

NSIDC,NASA,ESA have ,if anything, been a little conservative over the time scales involved here (and so were taken by surprise by 07' ......weren't we all?) but they have all been consistent in their warnings about the continued loss of Ice mass since 07' as the pseudo science skeptik outlets had been crying 'recovery' and confusing/mis-leading portions of folk who have interest but little experience in such matters.

As I have repeated (ad infinitum) 07',08',09' have effectively destroyed the last areas of ice that gave the Arctic it's potential to maintain a summer pack .I am not saying that there will be 'no ice' in the Arctic over summer times (1 million sq km or less is considered the threshold for a 'seasonal pack') and that those small enclaves of ice (Bay ice and areas where conditions are 'favourable for retention' that season) will vary in 'extent' year to year but the conditions that enabled the 'old perennial' to form and maintain a sizable summer ice pack will be lost.

A warm summer this year with favourable currents/winds and we will reach this 1 million km mark. If not we will still challenge the 07' 'record' even without 'exceptional circumstances' up there.

We will find this occurring from now on.

If I have a worry it is that we know so little about both the wider impacts this brings and also the 'speed' that those impacts will assert themselves.

Edited April 26, 2010 by Gray-Wolf

[Yorkshiresnows]

It's the speed of the 'downhill' that might surprise you 'J'.

If I'm right about the ice then the area of poor ice (both in and out of the Arctic circle) dictates a rapid decline over the next 2 months before we even get a chance to see how the central pack is shaping up. I worry that we'll continue on with the rate of decline as the central pack opens up and reveals the areas of poor ice formation over winter.

Then there's the weather up there this summer (forecast 'warmest year' and that new study showing a stat relationship between Low solar activity /H.P.'s over us ,blocking the Atlantic and keeping Canada/parts of the Arctic extra warm) and it's impacts on the 'stable' pack.

It's the speed of the 'downhill' that might surprise you 'J'.

If I'm right about the ice then the area of poor ice (both in and out of the Arctic circle) dictates a rapid decline over the next 2 months before we even get a chance to see how the central pack is shaping up. I worry that we'll continue on with the rate of decline as the central pack opens up and reveals the areas of poor ice formation over winter.

Then there's the weather up there this summer (forecast 'warmest year' and that new study showing a stat relationship between Low solar activity /H.P.'s over us ,blocking the Atlantic and keeping Canada/parts of the Arctic extra warm) and it's impacts on the 'stable' pack.

Panic not GW ..... there's little you can do in any case and you'll make yourself ill at this rate.

I'd also suggest that with a -PDO, decaying El Nino (with La Nina set to appear by Autumn) and depressed Jet, continuing low solar activity, then this next winter could be a great comeback by the Arctic.

The optimist see's the doughnut, The pessimist the hole !!

Y.S

Edited April 26, 2010 by Yorkshiresnows

[Gray-Wolf]

This seems to be the point that many of you are missing regarding 'Polar ice'. Once the Ocean is 'open water' the 'layering' that has been so important in ice formation/retention is attacked by wind / wave action ( some deep water waves go down as far as 200m as were measured off Hawaii recently) and without this 'novel' zoning it becomes like a normal ocean and ice development is 'limited' over winter making it all the easier for it to melt out over summer.

The reduction in sea ice thickness ,as measured by GRACE/ICESat through the noughties, highlights this issue with 2m thickness now becoming the norm.

The reports from this springs missions across the ice have noted how 'strange' the ice is and noted 'odd' behaviours of the pack as they travelled.

Polar ice is not as simple as a 'covering/extent' it runs far deeper than that. You could look at summer ice extent changes as a sign of this 'deeper' change.

Most folk (I've read) agree that the old layering of the Arctic ocean came about through the permanent ice cover through the last ice age. The odd polynya opening up does not allow the wind/wave action enough scope to destroy the zones but the large tracts of open water we are now accustomed to does.

The loss of these 'layers' also impacts the shallow shelf seas off Siberia allowing year round warm water to bathe the permafrost on the shelf allowing the methane leaks we have heard so much about.

As I said in my last post I do not 'worry' about the ice loss (and how low it will get over summer), I have my own understanding of that and 'worrying' would not change this, I do worry about the wider impacts of Arctic change on the planets circulations (ocean /air) and those impacts on the weather systems/climate cycles we have recognised.

You also mention 'Low Solar Activity'. Didn't a recent paper say that this 'statistically' means more Atlantic blocking?? (as we had this winter) and so more warm air over the Arctic (as we had this winter)??

How can this be a 'good thing'?

Edited April 27, 2010 by Gray-Wolf

[Guest North Sea Snow Convection]

Hi C.C. ,J,

When I was little I used to build dams in the local stream (turf and rocks). I'd spend an age building and shoring up but then I'd sit and watch. I couldn't bare take my eyes off it as I wanted to see 'how' the collapse started and the catastrophic breach (and wave) when it came.

The Arctic has become like that to me over the past 15yrs. I'm not worrying about it (the time that we could have done something about it is long gone) but I am fascinated by it as a process.

NSIDC,NASA,ESA have ,if anything, been a little conservative over the time scales involved here (and so were taken by surprise by 07' ......weren't we all?) but they have all been consistent in their warnings about the continued loss of Ice mass since 07' as the pseudo science skeptik outlets had been crying 'recovery' and confusing/mis-leading portions of folk who have interest but little experience in such matters.

As I have repeated (ad infinitum) 07',08',09' have effectively destroyed the last areas of ice that gave the Arctic it's potential to maintain a summer pack .I am not saying that there will be 'no ice' in the Arctic over summer times (1 million sq km or less is considered the threshold for a 'seasonal pack') and that those small enclaves of ice (Bay ice and areas where conditions are 'favourable for retention' that season) will vary in 'extent' year to year but the conditions that enabled the 'old perennial' to form and maintain a sizable summer ice pack will be lost.

A warm summer this year with favourable currents/winds and we will reach this 1 million km mark. If not we will still challenge the 07' 'record' even without 'exceptional circumstances' up there.

We will find this occurring from now on.

If I have a worry it is that we know so little about both the wider impacts this brings and also the 'speed' that those impacts will assert themselves.

John Holmes didn't say any of that. Or was it supposed to be some subtle personal jibe from the model thread? Dam making might still be appropriate for you in terms of acting your age.

Regarding 'pseudo science sceptics'. The majority of people do not eschew that the stabilisation of the ice over the last couple of years means anythig more than that. It has been a recovery within the context of speaking about the situation from 2007. It is only the silly extremists that have been saying the type of things you claim but they also exist within the AGW fringe do they not?

Edited April 27, 2010 by North Sea Snow Convection

[Gray-Wolf]

Now I am confused? What has J.H. got to do with my previous post? Jethro ,yes ('J') but J.H.? I don't think he even graces us with his presence down here on The Polar threads?

As for the 'Pseudo -Science' . I have seen no studies by any contrarian regarding ice formation /loss. I've seen piccies of Subs at the [pole in 56' ,67' 74' 91 and so on (Subs cannot surface with more than 1m of ice above them so 'sonar' leads to surface under). I've seen admiralty reports of the area up to Davis from the early 1800's (showing that there is natural variability of the pack) but nothing other than silly remarks regarding any ice thickness measures and the equipment used to gain such. I've even seen then criticising the Cryosat2 mission before any data has been released !!!

So NSSC, what do you take issue with? Is it the loss of Arctic ocean Zones? Is it the permafrost thaw? is it the loss of the majority of the perennial ice over the past 17yrs? is it the poor ice formation over this past winter? Is it the redrawing of ice type maps since Dr B's revelations last Autumn? What is your beef?

EDIT: Modis back up and running so we can see how Bering is doing;

http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2010116/crefl1_143.A2010116225000-2010116225500.500m.jpg

as you can see the ice is now on the verge of melt with a lot of 'small ice' now midst the larger floes. 8 or 9 days will see the 'small ice gone and the floes fragmenting.

Same order of play through Baffin/Davis;

http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2010116/crefl2_143.A2010116163000-2010116163500.500m.jpg

Edited April 27, 2010 by Gray-Wolf

[Guest North Sea Snow Convection]

Now I am confused? What has J.H. got to do with my previous post? Jethro ,yes ('J') but J.H.? I don't think he even graces us with his presence down here on The Polar threads?

As for the 'Pseudo -Science' . I have seen no studies by any contrarian regarding ice formation /loss. I've seen piccies of Subs at the [pole in 56' ,67' 74' 91 and so on (Subs cannot surface with more than 1m of ice above them so 'sonar' leads to surface under). I've seen admiralty reports of the area up to Davis from the early 1800's (showing that there is natural variability of the pack) but nothing other than silly remarks regarding any ice thickness measures and the equipment used to gain such. I've even seen then criticising the Cryosat2 mission before any data has been released !!!

So NSSC, what do you take issue with? Is it the loss of Arctic ocean Zones? Is it the permafrost thaw? is it the loss of the majority of the perennial ice over the past 17yrs? is it the poor ice formation over this past winter? Is it the redrawing of ice type maps since Dr B's revelations last Autumn? What is your beef?

Regarding the first bit it is not worth explaining/pursuing and taking the thread O/T

As for the rest, like many people, I have not exactly been happy with the levels of ice over recent years but my 'beef', as you put it, is being uneccessarily alarmist about the future. Especially in terms of the fact that the forces/feedbacks responsible are so uncertain. There are very probably several factors at work in terms of the ice movements and ebbs and flows. A large percentage of these are, imo, of a cyclical nature. The trouble with that I realise, is that it leads into the usual circular argument about what period of history we choose to demonstrate when ice has similarly diminished and then returned and also try to show which forcings were prevelant now which were present then and which are, supposedly, only present now in terms of justifying alarmism over some runaway ice extinction through forces created by our control that have, supposedly, got out of control.

Supposition leads often to fear through 'what ifs'. AGW forces depend on assumptions and suppositions regarding positive warmth amplyfying feedbacks created through the relationship between CO2/GHG's that are, assumedly, if they exist, and if they are really in the assumed numbers are behind the assumed 'nightmare scenario' of out of control alarmism that the forebing predictions centre around. Surely better to investigate the supposition to see if it is justified before prematurely predicting terminal doom, as well as examine other largely cyclical forces and local erratic short term patterns and phenomenon which can and do have notable effects over varying periods of time before expressing that fear too vociferously and far,far too often. That is my beef.

Edited April 27, 2010 by North Sea Snow Convection

[Gray-Wolf]

I think ( which is why I choose to focus there) the zoning of the Arctic ocean (unlike any other ocean) is the best way to satisfy yourself that this is 'beyond natural variation'. Seasonal ice forms such a layer but it is very shallow when you compare it to the depth of the zones that used to exist in the Arctic ocean. Only extreme lengths of time under ice (no waves to mix it up) will allow such depths to form. The size of the old perennial bergs attest to the depth that this layer used to extend too as it protected the base of the berg from the warmer,saltier waters below. Ice is not making much depth any more is it? The ice may have the cold over winter but ,as it grows, it pushes into the warmer ,saltier waters below and melts out. To me it is easy to see 'how' the ice continues to thin even over winter. It is not about the weather up top but the waters below.

I do not think that anyone argues that the Arctic has 'good ' and 'bad' years as far as 'ice extent' is concerned but the ice loss across the high Arctic (within the Arctic basin) is not within the sphere of such cyclical variation (as both the mud logs and ocean layering attests to).

Now either something changed to bring different currents into the Arctic Basin ,melting the base of the ice so summer melt (on the surface) proved sufficient to melt out large stretches and allow waves to mix the surface layer (the fresh ,cold layer that helps keep the thick perennial as ice over summer and to aid it's growth over winter) or all those pesky Sub's did a quick whisk job on those layers since the 1950's which allowed the basal melt which then let summer surface melt take out large stretches of ice and letting waves finish off the mixing job.

EDIT: If you doubt any of this then look to the southern sea ice and see how this does in a well mixed ocean and ,more importantly, what happens to it over summer. The Arctic WAS different in that it was a closed ocean (a giant pond) and these special zones were able to develop through the past ice ages. These zones are now disappearing (only the old haunts of the 'old perennial' left to mix now). Dr B's discoveries of the Chameleon ice means that the last areas of zoned ocean are now starting to suffer the same fate as the Siberian side of the Basin so soon we will have an ocean like all the rest in the Basin. That will mean the end of any chance of 'recovery' to the type of Arctic ice we used to know without the intervention of the 'deep cold' of an ice age. We WILL still have winter ice, those who measure the 'health' of the Arctic via ice extent will no doubt STILL cry 'recovery' each winter but the ice 'volume' is what is important and Cryosat2 followed by ICESat2 will be bringing us that data from now on.

EDIT:EDIT Another view of Baffin Bay/davis straight yesterday;

http://www.scienceda...00426131603.htm

you can 'see' the ice movement from the ice chunks and the way they orientate.

Now we have MODIS back I'm also a little unhappy with the look of the ice to the East of Frans Joseph land (where the gap opened in late March?) as it seems very close to melt out already.

With ALL the areas that put on the late 'spurt' in March now set to melt and the areas of poor ice formation in the high Arctic looking vulnerable in late April I am even more assured of the level of melt we will see this summer. If the ice to the north of Greenland is as bad as our glimpses lead me to believe then I'd expect migration across the top of Greenland to occur this year to so a bust year for Fram (hope the meltwater doesn't blight our chances of a hot summer!!!).

Edited April 27, 2010 by Gray-Wolf

[stewfox]

Yes daily obsessive doomwatch prophesising, repeating the same mantra day in day out is not a healthy lifestyle.

I thought this was about Arctic Ice not politics??.

Not sure what the personal digs at GW are about, people know his views.

He is one of the main running characters in this long running soap.

Anyway I prefer the apocalyptic version then the 'wait and see'.

What would people give to see a min of 8m sqkms by summer end and how GW handles that ?

[Gray-Wolf]

Thanks Stew, I believe it is!

As for 8m sq km , it'd depend on how thick it is and where it's hanging out (lol).

It's when will we be talking about the winter max being 8m km sq that concerns me......

I am sorry that some folk get so sad about things, it's not like we have any control over what is happening there is it? If you were me you'd be seeing the end of a process that started with ocean warming and subtle changes in circulations compounding other 'natural cycles' and augmenting their impacts.

Once the process was underway further 'natural' warming of the Arctic ,the ice, started a 'double whammy' with the erosion of the perennial in it's traditional enclaves (north of Greenland and throughout the Canadian Archipelago) and here we are.

Even a 'cold downturn' would not (IMHO) be enough to reverse the process. With the loss of the perennial and mixing of the ocean in the basin a new era in the Arctic dawned (the end of the post glacial period?) and we must now wait to see how the climate is impacted by the loss of it's air con. unit.

07' gave us an early glimpse of where we were in the 'change' but folk need to realise that this alteration has continued, to the point of completion, over the past 2 years and this year may well reveal how close we are to a pack that would be perennial if 07's synoptics were repeated (i.e. ,weather permitting)

[jethro]

I could well be being incredibly dense here but I still fail to see why this would matter. What catclysmic events would unfold if we only had ice in the winter?

[Gray-Wolf]

Maybe we should retire to the 'ice free Arctic' thread Jethro?

[Gray-Wolf]

http://www.catlinarc...aspx?newsid=104

Seems that 79 degrees north, in April, can now expect rain showers!!

The snippit tells us of the 'warm air' being currently pumped into the Arctic on the Southerlies that flank the H.P. system over Resolute Bay.

EDIT: and this from 'Nature'

http://www.nature.co...ature09051.html

Sea ice loss driving Arctic warming cycle, scientists confirm

Study identifies cycle of ice loss and temperature rise that could see Arctic's icy cover disappear sooner than expected

The Arctic is locked into a destructive cycle that could see its icy cover rapidly disappear, scientists have confirmed. A new analysis shows that dwindling levels of sea ice are responsible for unusual levels of global warming in the region. The findings reinforce suggestions that a positive feedback between ice loss and temperature rise has emerged in the Arctic, which increases the chances of further rapid ice loss and warming.

The study could re-ignite claims that the Arctic has passed a key tipping point, which could see ice disappear much sooner than expected. While most estimates say the summertime Arctic will not be ice-free until the middle of the century, some models suggest it could vanish within a decade.

James Screen, a researcher at the University of Melbourne, Australia, who led the study, said: "The concept of Arctic sea ice having a tipping point is still hotly debated. Our results cannot prove whether we have passed a tipping point or not. What we can say is that the emergence of these strong ice-temperature feedbacks can only increase the likelihood of further rapid warming and sea ice loss."

Temperatures in the Arctic have risen twice as fast as the rest of the world in recent decades, a phenomena known as Arctic amplification. Scientists have long suspected that loss of sea ice was responsible, but other factors such as changes in wind, clouds and ocean currents have also been blamed.

Writing in the journal Nature, Screen and his colleague Ian Simmonds, say they used new data to show that the projected ice-temperature feedbacks are now being observed. "Previous studies have been hampered by a lack of quality data for the Arctic," Screen said. "The ice temperature feedbacks have likely strengthened in the last decade or so due to the dramatic declines in sea ice. Prior to this, the signal may have been harder to detect."

Part of this change is down to the albedo effect, with white, reflective ice replaced by dark water, which absorbs more of the sun's heat. The removal of ice has also led to more summer evaporation of water, which acts as a powerful greenhouse gas in the atmosphere, and speeds temperature rise.

Screen said: "The albedo effect is very important here, but there are other factors related to the loss of sea ice that likely play a role."

Edited April 29, 2010 by Gray-Wolf