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Espen

I sent the press release to all important papers in Scandinavia, so tomorrow there will be some focus on the problem, I believe!

Wipneus

Peter Ellis: I don't see that. The values are not exactly he same, there is a one day difference.

Peter Ellis

Wipneus: Oh, fair enough. What stood out to me by eye is that Jan 1st 2010 is standing clearly on its own between 2011 and 2008, but on the right hand side Dec 31st 2009 is much closer to 2007.

Neven

Dirk Notz (one of the co-authors of the Tietsche paper discussed here) has written a guest blog post on RealClimate:

Such widespread loss of Arctic sea ice has sometimes given rise to the concern that the total loss of Arctic sea ice at least during summer time can no longer be avoided. In this context, usually the ice-albedo feedback is mentioned, since it provides a mechanism that can in principle lead to a so-called “tipping point” beyond which the loss of the remaining sea ice becomes unstoppable. However, recent research shows that this scenario is too pessimistic. For example, in a paper published in Geophysical Research Letters in January 2011, Tietsche et al. [1] used climate model simulations to examine the evolution of Arctic sea ice after an extreme loss event. In their model simulations, they artificially removed all Arctic sea ice at the beginning of June for selected years and examined if the ice would recover from such extreme event.

Their main result is shown in Fig. 3: It took only about two years after each complete sea-ice removal until the ice had recovered to roughly the extent it had before the removal. Hence, sea ice extent is primarily defined by the prevailing climate conditions; the ice-albedo feedback mechanism is, in isolation, too weak to stabilize a very low sea-ice cover. In examining the mechanisms behind this finding, Tietsche et al. found that unusually large amounts of heat indeed accumulate in the ocean during the ice-free summer. However, this heat is efficiently released to the cold atmosphere already during the following autumn and winter. Once that heat release has cooled the ocean to its freezing temperature, sea ice forms again. Because this ice is initially very thin, the efficient release of heat from the ocean continues for some time, causing a rapid growth of the new sea ice. Much of this ice then survives the following summer, and sea-ice conditions can quickly return to those before the artificial perturbation.

Bob Wallace

It may be that the summer heat is released before the following year, but extra heat should mean that the freezing season will be delayed while the heat is dissipated.

Less freeze time should mean less ice to melt the following year followed by even more season-lengthening heat stored in the water.

--

Heat input during the melting season is almost certainly going to be increasing as the atmosphere warms. Even if we hit some sort of minimum season refreeze base it seems that the melt rate would continue to increase.

I'm willing to accept that Notz knows a lot more about the ice than do I, but from what's posted it seems like he might have left out a couple of factors.

Twemoran

Is anyone aware of a good b&w graph for global ice cover (extent or area) that would work well shrunk to a fairly small size?

I'm writing a short blurb in a low circulation, nationally distributed magazine and want something to show that we are not just looking at a northern hemisphere phenomena.

BTW the nation is Canada

L. Hamilton

Twemoran, I've got the data and it's very easy to generate graphs, B&W or otherwise. Here's one of the global area max/min anomaly, which I think is visually more effective than CT's long skinny "tape" plot.

http://img.photobucket.com/albums/v224/Chiloe/Climate/sea_ice_CTglobal_anom_to_date.png

Bob Wallace

After reading the Notz piece on Real Climate, he does recognize later refreeze dates due to increased heat storage.

It seems that his hope for recovery rests on warmer water freezing faster. But that should hold only until a skim of ice forms on the surface. Then the trapped heat should slow thickening.

Later start and slower freeze rate.

At least that's what I'd guess.... ;o)

Twemoran

Thanks Larry - If they use it I'll be able to get you a hard copy if you would like, or at least the password for the online edition.

L. Hamilton

Sure, let me know if it proves useful.

L. Hamilton

Forgot to say, let me know if they'd prefer a higher-rez version of the graph, .eps or other. For interweb purposes I mostly just use low-rez .png, because everybody can see those.

Wipneus

@Peter Ellis:

After sleeping on it, I realized that there is something wrong about it. The left axis is drawn at the first of Jan, while the right axis is drawn at the last of Dec.

I do ignore leap years, so 2004->2005 and 2008->2009 will jump an extra day.

Does this updated graph look it bit better to you?
https://sites.google.com/site/arctischepinguin/home/piomas/piomas-trnd4.png

Seke Rob

Wipneus,

Not sure what you're doing, but the PIOMAS data file has only 365 days for all years. Did not read the documentation what they do/did with the Feb 29.

Seke Rob

Here's my version of same which draws a line across, the program, not me, from the Dec 31, 2010 datapoint. There's a slight shift because of the inter-day change of 93 cubic km. Also computed the 1979-2010 average per day and plotted that in (black line). The importance to is the big picture... decline, hardly ever reaching over the previous year volume.

Re the ice albedo effect, FY (60%) or MY (80%), does it matter much when there's a snow top that has a 90%+ reflection (IIRC)? I've yet to see a NOAA webcam year when there's not snow on top, have though no feel if this is Arctic wide. Surely with strong winds there will be huddling up in places.

Seke Rob

Oops, the link to Chart

RunInCircles

Neven
How did Dirk Notz explain that we are seeing ice decease every year versus his contention that basically in one winter ice must come back and it will be thick enough to survive the next melting season. All data points to the fact that more ice is lost every summer than is gained in winter. Mr. Notz says that his model shows that if we start with no ice we gain ice thickness so fast that we apparently have more ice thickness than if we start with the current ice cover? Or at enough to bring us within 90cm of the current ice thickness. After all if the ice started 90 cm thinner this year there would only be a few isolated older flows left. I am assuming that he thinks his model is accurate enough to show the continuing decrease of ice thickness we are presently experiencing. After all he is asserting that his model is reflective of what the arctic ocean behavior is.

Wipneus

@Seke Rob:

Thanks, I had not noticed that.

Did not read the documentation what they do/did with the Feb 29.

There does not seem to be any discontinuity. I assume they just squeeze the 366 calendar days into 365 file days.

Peter Ellis

Wipneus: I think it's simply that volume was increasing very rapidly at the end of 2007 and very slowly at the end of 2009.

Specifically, the difference between Dec 31 2007 and Dec 31 2009 is about a third of a million km^3, yet the difference between Jan 1 2008 and Jan 1 2010 is closer to 0.75 million km^3. The difference thus appears to jump a third of a million km^3 in a single day!

RunInCircles: I am convinced this is the difference between climate-driven ice loss (which we're seeing in the real world) and "causeless" ice loss (i.e. them arbitrarily removing all sea ice in their model).

The ice in their model recovers in 2-3 years up to the trendline: it returns to the levels specified by the general climate. In our case, the changing climate itself is driving the ice loss.

There is presumably a lag time of ~2-3 years for ice conditions to adapt to the climatically-specified level. If you like, the ice levels lag a couple of years behind the climate. So, if global warming magically stopped tonight, Arctic ice would continue to drop for another 2-3 years and then stabilise.

In their paper, the modelled climate (i.e. the overall trendline of ice loss absent any magical ice removal) is seemingly not changing fast enough - the model forecasts total ice loss by sometime in 2060-2080, while all the real-world trends indicate it will be well before then.

RunInCircles

Peter
What they are saying then is that the loss of sea ice will have no effect on the earth?
Business as usual, no need to worry.

crandles

The global warming effect over a couple of years is nowhere near as large as removing all the ice so if GW magically stopped, I would suggest the ice would drop for another 1 or maybe 2 years at most before stabilizing. (That is probably within natural variability so it might be hidden or appear longer.)

While the climate clearly wasn't ready to support ice free conditions in 2007, this doesn't tell us how rapidly we are moving towards a climate when it can be supported.

Oslo

Bob, according to Jason Box (2009), the lag time for the Greenland ice sheet (vs. NH) is 10 years, and he argues that the Greenland warming would continue to warm 1.08-1.68C after the warming NH warming flattens out.

- Using the empirical relationships between Greenland and the Northern Hemisphere surface air temperature data, we calculate that if Greenland was to become in phase with the hemispheric pattern, as it did after 1923, an additional 1.08–1.68C warming would occur.

If we take into account what Hansen says, the slow climate feedback (vegetation and ice) might take more than a hundred years before the climatic response is fullfiled.

So the Arctic sea ice is probably doomed even if GHGs level out, it remains to be seen if the Greenland ice sheet can be saved.

Oslo

Sorry, my comment was addressed to Peter Ellis:

There is presumably a lag time of ~2-3 years for ice conditions to adapt to the climatically-specified level.

r w Langford

One parameter that is hard to get a handle on re the discussion on ice recovery is the contribution of warm currents taking energy into the arctic and cold currents moving out at depth. These numbers may not be included in some models that predict rapid ice recovery.

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