New Paper confirms Cryosats validation of Piomas

[The_Global_Warmer]

http://www.personal.soton.ac.uk/pgc1g08/grl50193.pdf

 

 

 

 

 

 

 

 

 

Figure 3. Time-series of monthly Arctic sea ice volume from CS-2 (△) and from PIOMAS (solid line and ◯) for two winter growth periods (October – April).

 

 

 

Figure 1. CryoSat sea ice thickness compared with PIOMAS and ICESat ice thickness measurements. The data are restricted to the “ICESat” domain covering the central Arctic Ocean. (a) shows the 2003-7 average ICESat ice thickness for October/November and ( 2004-8 average for February/March. © and (d) CryoSat thickness for October/November 2010 and February/March 2011 and locations of the airborne EM data (black lines) and OIB data (grey lines) used for validation, ULS moorings (△, ◯, □). (e) and (f) CryoSat thickness for October/November 2011 and February/March 2012 and locations of the airborne EM data (black lines) and OIB data (grey lines) used for validation. (g) PIOMAS for October/November 2011 and (h) February/March 2012.

 

 

 

 

[bluewave]

Thanks for finding the whole paper and posting it.

 

 

 

Our data provides further evidence for the long-term decrease in Arctic sea ice volume simulated by PIOMAS. The average volume loss over both the autumn and winter periods is ~500 km3 a-1, equivalent to an 0.075 m a-1 decrease in thickness, which is close to the peak thinning rates observed in the submarine record [Kwok and Rothrock, 2009]. The rate of decline in autumn ice volume that our data show (~800 km3 a-1) is 60% higher than the decline in the PIOMAS integration analysed in S11. This is further evidence that the PIOMAS estimates of autumn volume loss are conservative (S11). The decline in winter ice volume that we observe is however less than for PIOMAS (by around 25%). These results suggest a greater loss of Arctic sea ice volume in summer and a greater gain of volume in winter than PIOMAS.

Finally we can speculate that the lower ice thickness and volume in February/March 2012, as compared with February/March 2011, may have been one factor behind the record minimum ice extent reached in September 2012.

[SVT450R]

I take it Cryosat still doesn't plan to give access to images/imformation on a monthly or trimonthly basis anyone hear anything different?

[TerryM]

I take it Cryosat still doesn't plan to give access to images/imformation on a monthly or trimonthly basis anyone hear anything different?

 

You're correct, in fact because of the method they use it will only work in the spring and fall seasons when the ice/water mix is within certain parameters. There was a discussion of the at Neven's earlier today.

 

Terry

[dabize]

http://thinkprogress.org/climate/2013/02/14/1594211/death-spiral-bombshell-cryosat-2-confirms-arctic-sea-ice-volume-has-collapsed/
 
The people react.

 

These results suggest a greater loss of Arctic sea ice volume in summer and a greater gain of volume in winter than PIOMAS.

 

I must say that Cryosat-2 showing a greater dynamic between winter and summer than PIOMAS did just makes an ice free state seem even more imminent. 

 

The greater seasonal sensitivity will make us reach the "tipping point" (i.e. an early enough meltout to increase Arctic solar energy absorption beyond the amount that can be seasonally re-radiated) that much sooner. This will be further hastened by the ocean current changes (that are now becoming evident) which seem to be favoring more bottom melting

 

I'm guessing that Cryosat is also telling us that a year round ice free Arctic is coming sooner than we might have thought otherwise.

[skierinvermont]

I'm guessing that Cryosat is also telling us that a year round ice free Arctic is coming sooner than we might have thought otherwise.

 

What does Cryosat have to say about the date of explosion of our sun?

[skierinvermont]

 

The greater seasonal sensitivity will make us reach the "tipping point" (i.e. an early enough meltout to increase Arctic solar energy absorption beyond the amount that can be seasonally re-radiated) that much sooner. 

 

 

Also I'm really not sure what you mean by this. The increased absorption by lowered albedo is balanced by higher temperatures which increase radiation and by a lessened latitudinal temperature gradient which reduces net heat flux into the arctic. There can be no tipping point. Every 1/m2 of increased absorption is immediately balanced by 1w/m2 of increased radiation and reduced net flux into the arctic.

[skierinvermont]

I'm confused I thought PIOMAS agreed well with IceSat 2003-2008. The above chart shows it being 3k too low. 

[bluewave]

A new paper defines tipping point in a different manner which takes into account the abrupt increase in

seasonal amplitude.

 

 

Abstract. There is ongoing debate over whether Arctic sea ice has already passed a "tipping point", or whether it will do so in the future. Several recent studies argue that the loss of summer sea ice does not involve an irreversible bifurcation, because it is highly reversible in models. However, a broader definition of a "tipping point" also includes other abrupt, non-linear changes that are neither bifurcations nor necessarily irreversible. Examination of satellite data for Arctic sea-ice area reveals an abrupt increase in the amplitude of seasonal variability in 2007 that has persisted since then. We identified this abrupt transition using recently developed methods that can detect multi-modality in time-series data and sometimes forewarn of bifurcations. When removing the mean seasonal cycle (up to 2008) from the satellite data, the residual sea-ice fluctuations switch from uni-modal to multi-modal behaviour around 2007. We originally interpreted this as a bifurcation in which a new lower ice cover attractor appears in deseasonalised fluctuations and is sampled in every summer–autumn from 2007 onwards. However, this interpretation is clearly sensitive to how the seasonal cycle is removed from the raw data, and to the presence of continental land masses restricting winter–spring ice fluctuations. Furthermore, there was no robust early warning signal of critical slowing down prior to the hypothesized bifurcation. Early warning indicators do however show destabilization of the summer–autumn sea-ice cover since 2007. Thus, the bifurcation hypothesis lacks consistent support, but there was an abrupt and persistent increase in the amplitude of the seasonal cycle of Arctic sea-ice cover in 2007, which we describe as a (non-bifurcation) "tipping point". Our statistical methods detect this "tipping point" and its time of onset. We discuss potential geophysical mechanisms behind it, which should be the subject of further work with process-based models.

 

http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.html

 

http://www.the-cryosphere.net/7/275/2013/tc-7-275-2013.pdf

 

[skierinvermont]

Ehh I don't really see changing or broadening the definition of tipping point as useful to the discussion. It complicates the terminology rather than simplifies it. Most people think of the first definition of tipping point. Now we have to clarify if we mean reversible or irreversible tipping points. And reversible tipping point sounds like an oxymoron to me. A lot easier to maybe say "a temporarily enhanced positive feedback."

[dabize]

Ehh I don't really see changing or broadening the definition of tipping point as useful to the discussion. It complicates the terminology rather than simplifies it. Most people think of the first definition of tipping point. Now we have to clarify if we mean reversible or irreversible tipping points. And reversible tipping point sounds like an oxymoron to me. A lot easier to maybe say "a temporarily enhanced positive feedback."

 

I suppose that an exploding Sun could be considered a "temporarily enhanced positive feedback" as well.

[TerryM]

http://thinkprogress.org/climate/2013/02/14/1594211/death-spiral-bombshell-cryosat-2-confirms-arctic-sea-ice-volume-has-collapsed/

 

The people react.

 

 

 

 

I must say that Cryosat-2 showing a greater dynamic between winter and summer than PIOMAS did just makes an ice free state seem even more imminent. 

 

The greater seasonal sensitivity will make us reach the "tipping point" (i.e. an early enough meltout to increase Arctic solar energy absorption beyond the amount that can be seasonally re-radiated) that much sooner. This will be further hastened by the ocean current changes (that are now becoming evident) which seem to be favoring more bottom melting

 

I'm guessing that Cryosat is also telling us that a year round ice free Arctic is coming sooner than we might have thought otherwise.

I'm stealing a quote from the comments section in the linked ThinkProgress article.

 

"When the ice cap goes, the Arctic inverts from solar reflector to solar absorber. It’s not merely a different state, it’s the opposite state.."

 

It sums up my thinking quite succinctly.

 

We know from paleo studies that in ice free eras cold blooded creatures were wintering in the Arctic. It's reasonable to assume that the only way this was possible is if dense, low lying clouds were trapping huge amounts of summer heat through the winter blackout months. We know from icebreaker reports last fall that huge fog banks, so optically thick that they were being seen as ice cover by the satellites were observed very close to the pole.

 

Skier has argued that any warming will simply be radiated away, but an inversion layer under the cloud cover precludes that.

 

Tipping points may defy definition but this isn't analogous to having melted away 80 percent of the ice in a beer cooler, this is more like losing 80 % of the ice and finding that the cooler's sitting in the sun and the white paint on top has charred to a flat black surface.

 

We've turned our beer cooler into a solar oven.

 

Terry

[skierinvermont]

I suppose that an exploding Sun could be considered a "temporarily enhanced positive feedback" as well.

 

Of course all tipping points are reversible given a long enough time. But when most people think of a tipping point they think of something that is at least not reversible for a long time or without great opposing effort. 

 

 

For example, it is quite plausible hypothetically that feedbacks in the arctic could be strong enough to cause runaway local warming which irriversibly tips us into a cooler state which is reversible only by major global cooling. It turns out this is probably not the case, but it is still useful terminology to call this concept a tipping point. 

[Jonger]

Of course all tipping points are reversible given a long enough time. But when most people think of a tipping point they think of something that is at least not reversible for a long time or without great opposing effort. 

 

 

For example, it is quite plausible hypothetically that feedbacks in the arctic could be strong enough to cause runaway local warming which irriversibly tips us into a cooler state which is reversible only by major global cooling. It turns out this is probably not the case, but it is still useful terminology to call this concept a tipping point. 

 

Once sea-level rise becomes more of an issue, I think sequestration will get more focus. Right now, most people don't see much change and frankly don't care. Wait until sea levels start rising and Manhattan is affected.

 

Economics have started to reduce CO2 output in the developed world, economics alone won't do enough, habitat loss in prime real estate will bright immediate changes.

[csnavywx]

Changes in low and mid-level lapse rates as well as moisture flux will ensure that some of that heat remains trapped. Radiative cloud feedback (via convective clouds) needs more serious consideration as we move forward.