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Messages - Whit

Pages: [1]
1
Antarctica / Re: Discussion of the Antarctic Peninsula
« on: January 10, 2016, 06:57:07 PM »
Larsen has the blues.

http://go.nasa.gov/1OIprQU

2
Arctic sea ice / Re: Arctic Image of the Day
« on: January 23, 2014, 10:59:15 PM »
So, how did they smell?

Sorry, just curious.  :)
You smell their breath if you're downwind of them when they blow, and it's not really what you would expect from the scenery ... Imagine a really awkward moment in an elevator, amplified by a 30-ton herring-feeding machine ;)

3
Arctic sea ice / Re: Arctic Image of the Day
« on: January 23, 2014, 10:48:22 PM »
I lige måde, Espen :)

4
Arctic sea ice / Re: Arctic Image of the Day
« on: January 23, 2014, 10:14:56 PM »
The ocean around Tromsø (69 N) in the north of Norway has been teeming with herring over the last few years. This attracts other species, especially larger predators. After the herring-populations increased the humpback-whales started to make extended feeding-stops in the fjords on their way from the Arctic Ocean to their breeding grounds in the Carribbean.

They tend to leave around the middle of January, and I was lucky to get a last look at them waving goodbye, for now.

The first image was shot with a wide angle lens, just to give you an idea of how close they got. At the same time two packs of killer-whales kept a more respectful distance. We had four of these 15 meter long 30-ton giants playing and showing off around our small RIB, at times so close that we could have touched them. We most certainly could smell them ...

5
Arctic sea ice / Re: Arctic Image of the Day
« on: December 12, 2013, 08:47:08 PM »
Not about ice, but still worth mentioning I think.

Nordic Nature Photographer of the Year also happens to be a professor in biology at the University of Tromsø. Dr. Audun Rikardsens research on salmon and arctic char has given us fascinating new insights like salmon diving to depths of 800 m and more off the west coast of Svalbard and arctic char heading into full salty sea-water at 2C. Stuff we didn't think was possible until Rikardsens team radio tagged a bunch of our finned friends ...

But his pictures ... oh man.

Have a look.

One of my favorites, arctic char in midnight sun, Spitsbergen:


6
Consequences / Re: Effects on Arctic Wildlife
« on: August 13, 2013, 03:21:03 PM »
It's changing quite rapidly, and the weather is weirding on my side of things. I'm heading for the north coast of the Kola peninsula in 2 weeks. There's been almost no rain for the last 2-3 months. The rivers are 50-60 cm below average. I was hoping for some cloudberries in addition to the odd trout, but I can't see that happening. Temperatures have been up to 34 C as far as I know.

I've fished and travelled the north coast of Kola for nearly a decade and norwegian Lapland for twice as long. The insect hatches are coming earlier and earlier, and spring is early. The most striking and easily visible change is the vegetation. The tundra on the norwegian side is "slowly" turning into forest.

Trout are displacing arctic charr in a couple of rivers i know of. The fish-scientists I talk to blame a combination of temperature and possibly pressure from sea-lice from the fish farms. The displacement is happening in rivers where none of the fish go to sea as well, so I'll put my money on temperature.

I'll give a brief report about the state of things on the ground up there when I get back.

7
Arctic sea ice / Re: Arctic Image of the Day
« on: August 05, 2013, 10:35:52 AM »

8
Who thinks we will still see a New Record?
One week ago it seemed that 2013 could catch 2012, but now?
Anyway, I think we will see another cliff soon.
I don't think we'll see a new record. But according to TOPAZ4 ice thickness, the set up for a record was there, if that model can be trusted. The weather just saved the ice this time. As long as the volume sticks to it's trend we will have an ice free state in a few years. The differences in thickness in TOPAZ4 2012 and 2013 are quite staggering.

9
Arctic sea ice / Re: IJIS/JAXA
« on: July 17, 2013, 05:24:07 PM »
It may very well be like Whit suggests.
through a quick check on MODIS r04c05 I saw nothing suggesting that the 'process' is interrupted, like IJIS seems to suggest when one sees it's graph.
Fast ice over there is quickly breaking up (Buor Kaya and Khatanga Gulf).
Such processes may temporarily enhance extent in these regions.
It would nearly be a first according to my wife.

if I try to visualize it I just imagine a glass of water with two ice-cubes and measure area and extent. Then I smash the cubes until they're all nice and frappé-like and measure them again. Thickness has gone down, while area and extent has gone up. Still the ice should be in a more vulnerable state.

The icecubes are smaller this year it seems. It should make them disperse more and cover a larger area, thus keeping the albedo lower. My total lack of training in maths and physics leaves me totally undergunned for tackling this problem. At least, when you know very little, it's easy to learn a lot :)

10
There it was :) Than you!

11
The process of ice melt within a given year and the year-on-year reduction in the amount of ice remaining at the summer minimum are completely different physical processes!
Certainly. I don't think anyone has said anything contrary to that either. If I have said something that could be interpreted that way, it certainly wasn't my intention.

However, there are similarities. In a small system, like an alpine lake, you have day and night variations with substantial refreeze during the night in the beginning of the melting season. So you get variations around a negative trend, just like we see year-to-year in the Arctic.

Ice that undergoes a melt/freeze cycle is weaker and warmer than ice that just stays frozen. As the ice thins the ratio of the active melt/refreeze zone vs. the frozen zone decreases, thereby decreasing tensile strength of the ice-column by shifting the ratio of weak vs. strong ice.

Exponential loss of ice can be inferred by these and other factors, like volume to surface area ratio and ice-quality, that are quite similar in small and large systems. And as we have seen, the degree of loss has not been modeled very well. Speculating about why is interesting, and other bodies of ice might just provide a clue as to what is happening.

At least that's my 5 cents, and I don't think it's all conjecture either. Our eyes in the sky are amazing tools, but sometimes you actually have to get out there to get the full picture. Extent and area c an only tell you so much. I'll just quote Barber et al 2009; Perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009:

[1] In September 2009 we observed a much different sea icescape in the Southern Beaufort Sea than anticipated, based on remotely sensed products. Radarsat derived ice charts predicted 7 to 9 tenths multi-year (MY) or thick first-year (FY) sea ice throughout most of the Southern Beaufort Sea in the deep water of the Canada Basin. In situ observations found heavily decayed, very small remnant MY and FY floes interspersed with new ice between floes, in melt ponds, thaw holes and growing over negative freeboard older ice. This icescape contained approximately 25% open water, predominantly distributed in between floes or in thaw holes connected to the ocean below. Although this rotten ice regime was quite different that the expected MY regime in terms of ice volume and strength, their near-surface physical properties were found to be sufficiently alike that their radiometric and scattering characteristics were almost identical.

12
Arctic sea ice / Re: IJIS/JAXA
« on: July 17, 2013, 11:08:05 AM »
Crumbling and fragmenting won't affect extent and area immediately, will it? It might even add to area and extent as I see it.

13
Thanks for the replies. This weird season just keeps giving and I must admit I was slightly surprised by the slow onset. Nightvid, modelling based on a smaller enclosed body of sea-ice seems like a good idea. Perhaps trying different scenarios with different kinetics.

The Icefjord on Spitsbergen rarely freezes over completely, but I got to see one ice-off there. It was in the late nineties IIRC. First the sun worked the ice for a while, weakening it. And when the winds where right it all disintegrated while hitching a ride towards the open sea. You see the same in lakes, although wind seems to influence ice-off slightly less in smaller bodies of water. That's a generalization. Topography matters a lot it seems.

Espen, yeah. To me it seems completely counterintuitive that ice disappears in a slow linear fashion as predicted by the standard models. I can see a tail of sorts in areas where FYI is compacted, but given the right conditions I feel quite certain that we will get below 1 mill km2 in a stunningly rapid series of events. Most certainly not this year, but if the perennial ice is going (and that's almost a given now) it should go as other forms of floating ice goes - in a flash, when the conditions are right. I believe it could have happened this year. At the same time I haven't written of the possibility for a new minimum record this year. The fragmentation event and the small size of the floes should add to both area and extent. Slush covers more than icebergs ... Whether it makes the ice more resistant to melt is another story.

Barbers study in Beaufort is right on the ball IMO. He states that the new regime of rotten ice should be incorporated in the models. From that I infer that it isn't already. And to me that seems like a plausible explanation for the models complete lack of ability when it comes to predicting the speed of ice-loss we have been seeing.

Waynes work has been most illuminating. I think there might be something to learn from the the ratio between frozen ice and the melt/freeze zone you get in spring. At least for me. You guys might have covered it already :)

14
I am confused by the SIA increases. It is simply not cold enough for significant ice creation.  Where is it coming from ?!
Fragmentation and dispersion could contribute, especially in areas where the ice is warm, soft and slushy.

15
Arctic sea ice / Re: Canadian Arctic Archipelago
« on: June 23, 2013, 10:39:17 PM »
It's quite a difference in just a week.
June 16:


The main fracture is clearly visible June 10, but if I remember correctly it has been there for a while, just refrozen with fres ice a couple of times.

16
Arctic sea ice / Re: Canadian Arctic Archipelago
« on: June 23, 2013, 10:32:53 PM »
A few days ago I was having a look around Worldview and Kind of Blue by Miles Davis just found it's way to the speakers. in particular stood out.

17
Counldn't the fragmentation actually contribute to larger extent for a while?

Grab a disk shaped icecube with an elliptical cross-section. Grab another disk of the same volume, but make it uniformly thick, like a slab. Then grab the same volume of ice and smash it to pieces with a hammer. Put them in a separate glasses with a slightly larger diameter then the disks and see what happens.

The crushed ice will keep its area and extent longer than the compact pieces due to being more easily dispersed, but it will be the first one to go completely.

The distribution of the ice this season is somewhere between the slab and the crushed ice in my analogy. More ice has been pushed towards the margins, where its chance of survival is rather small.

Analogies from an amateur certainly has limited usability, especially when comparing the Arctic to an ice-cube in a glass of water. But I would not be surprised if we saw more and more of Barbers feedback entering the stage from now on.

18
Developers Corner / Re: Rapid Response vs. Worldview
« on: June 10, 2013, 02:37:50 PM »
Thanks :)

19
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: June 10, 2013, 12:02:04 PM »
The break-up in the Lincoln-Sea is quite interesting. It seems like the ice there is much more vulnerable than last season.

20
Developers Corner / Rapid Response vs. Worldview
« on: June 08, 2013, 08:51:17 PM »

Is there any difference in image-quality?

I see most people here use the RR images, and I can understand why if you want large files that caver a lot of area. However, I find the Worldview-interface so much better. If all you need is a cropped image from 100% zoom, is there any point in not using Worldview?

Inquiring noobs want to know :)

21
Thanks.  I've sharpened thousands of images, I just had never heard it called "increasing details".  It's selective contrast boosting of edges, doesn't actually add new details.
Totally agree. Sharpening just makes details easier to see, but it doesn't add any information. However, detail in a high-resolution image can get lost when downsizing. Sharpening sometimes help, sa Im sure you're aware.

As a sidenote, Adobe calls the entire sharpening tool block "Detail". Apple Aperture calls it definition, and I have no idea what the similar function is called in GIMP. "Increasing detail" seemed more accessible at the time of writing :)

22
What does "increased the details" mean?

Do you mean that you increased contrast and lowered brightness to make the details easier to see?
It's just a simple sharpen filter. I suppose I coud do a better job if I used Photoshop or similar software.

I see that it got too dark too. That's what you get for editing on a laptop while commuting :)

Depending on the image and the screen I'm viewing it on, sometimes detail gets lost in the highlights. You can get some back through increasing contrast and pulling highlights, exposure or brightness. I guess we could get a lot more detail from the highlights if we had access to png or tiff-files. Information might get lost when they are converted to jpg, and when going from whatever native colorspace they use to sRGB.

I just started looking at this and I suspect I might be treading old ground ... I do remember a discussion at the blog about editing satellite images with GIMP.

Sorry for going OT Neven. Feel free to move.

23
I'm still sticking to 1.75-2.0
and wondering about Arctic Melt Pole and Cyclone circling around
Look. The beginning of a polar donut.

1.75-2.0 here as well.

24
This is from a cloudless area between Jim's image and CAA. I have increased contrast, lowered exposure and increased the details to show the degree of fragmentation that's going on. To me it seems much more fragmented than in August last season.

25
It looks to me, and this is mostly based on a pure visual inspection of the ice supported by Piomas thickness data from the eminent Mr. Reynolds, that in general the margins are in slightly better shape than last season, while the interior is worse off.

That in itself is an argument for a steeper drop-off when the Barberque gets past the margins.

As a caveat, it also mirrors my preconceptions about how ice behaves, which might be a bad thing as analysis goes.

26
Arctic sea ice / Re: The Summer Acceleration
« on: May 25, 2013, 04:03:17 PM »
I really wish we had more information about what is going on below the ice, and the state of submerged ice.

Like Wayne has showed there is an active melt-refreeze zone of porous ice. The more porous the ice is, the higher the effective area vs. volume is. And the higher the effective area vs. volume heat is allowed to work on, the faster the melt will be. If the ice is thin enough this porous zone will also contribute through decreased albedo.

From this laymans perspective the low quality of the 2012 ice could be a significant part of the explanation behind the rapid and extensive reduction last season.

If the quality of the ice is worse than last season 2013 might prove to be even more of a surprise than last year, especially if you just consider volume and area, without considering the quality of the ice itself.

If some of that warm atlantic water upwelled during the winter (and it probably did in Chukchi at least) we could have huge areas of porous low-quality ice, primed for accelerated melt when insolation starts doing it's thing.

I know most of this is pure speculation, but I just can't get past the similarities between the way a high alpine lake behaves at ice-off and the way the Arctic sea ice has behaved the last 5 years.

I just skimmed Ice Tank Experiments Highlight Changes in Sea Ice Types. Does anyone know if a similar experiment has been done in reverse?

27
Arctic sea ice / Re: Arctic Ocean 'acidifying rapidly'
« on: May 18, 2013, 11:54:11 AM »
Quote
It is well know that CO2 warms the planet, but less well-known that it also makes the alkaline seas more acidic when its absorbed from the air.

Something can not become "more acidic" if it is not acidic to start with.

What they should state is that it is becoming less alkaline, possibly, one could say more neutral.

The oceans never have been and never will be "acidic".

Mind you,  science literacy never was strong point in climate reporting at the BBC, where they have adopted an official policy not to abide by their legal obligations of neutrality on climate reporting.
You suggest more neutral as nomenclature, while calling the correct use of the term acidification a word game?

Less alkaline or more acidic are in fact synonyms. The word games are the ones that are usually being performed by less than knowledgeable "skeptics" or pure bullshit-artists (as defined by Harry Frankfurt). Why you are echoing this semantic pedantry is a mystery, as the labels we put on the process is completely irrelevant to the outcome.

The facts are clear. Whether we call the process of lowering the oceans pH de-alkalinisation or acidification is irrelevant. The reduction in ocean pH is faster than any other event we know of, and the chemical processes behind them are well known.

The entire point of claiming the oceans aren't acidifying is to belittle the huge problems several oceanic foodwebs will be facing. We have clear parallels in freshwater systems, where trout, charr and salmon have been eradicated completely in huge areas in southern Norway. Not only did trout disappear. Their main food, small crustaceans and several species of aquatic insects disappeared much earlier than the fish were unable to breed successfully. Fish growth was stunted, both due to lack of food, but also due to changes in water-chemistry. We are still fighting this problem, long after acid rain was reduced. The only solution seems to be adding chalk to the water, year in and year out. And we probably have to keep at for decades to come. We have seen the destruction of entire ecosystems caused by acidification. That is why the term carries such weight.

I am sorry for piling on but this issue provokes me. The word game is one of denial of the underlying chemical process and the inherent dangers to most major ecosystems on the planet. It is being performed on blogs, by politicians, and is clearly reverberating through the internet and in other media.

The mass extinction we are laying the ground for by changing the compostion of the atmosphere and oceans will be of cataclysmic proportions long before the oceans become acidic. They are still acidifying, and the problems persists, no matter what we call the process. If the process stops at an average ocean pH of 7.6 the oceans are still alkaline. And the mass-extinction event caused by such an acidification will be inevitable.

Word-games indeed.

28
I'd not considered the albedo impacts? with much of the ice cemented together by young ice once melting begins in earnest will we not see a dramatic drop in albedo of the central pack (normally pretty high albedo for contiguous ice?)?

The other thing that comes with a very fragmented pack is a lessening of the dampening from swells. will this lead to more overwash and edge melt over the early season?
The albedo-impacts from refrozen cracks are clearly visible from space, so I suspect they will play a part as insolation increases. I am wondering what it does for melt-pond formation.

When it comes to your second paragraph, my experience with ice is that once you get to a certain stage of fragmentation it all just disappears really fast, at least partially for the reasons you mentioned. There is also the issue of volume vs. surface area that needs to be considered.

Whether we are close to the disintegration-stage now is a completely different question and I'm not competent to answer it. However, a visible inspection can say a fair bit about ice-quality, and it seems to be decreasing year for year. Additionally, if the porosity increases as the thickness decreases we are in for rapid change.

All IMHO.

29
Pretty soon we should start to get the answer to what role the cracking events this winter will play. I have a feeling they will be a major player. The cracks are weaknesses, and have generally lower albedo than solid ice. We should see the old cracks opening up again. And in some areas there are a lot more of them than we can see at the moment.

Snapshot near the Pole, May 16th 2012.

Same area, May 14th 2013.

30
I think if we were close to the edge of the cliff the Joint Chiefs would be telling us in no uncertain terms.
He may not be the official spokesman for the Joint Chiefs, but Admiral Samuel Locklear seems to be aware that the house is burning. In fact, he considers climate change the greatest security risk of our time. I agree with him.

I have no idea how serious the situation will get the next century or so. But we've started several processes that seems to have the potential for acceleration with feedbacks upon feedbacks. The Arctic is just the starting point, and the transition to where we're going seems more likely to be bumpy than not.

Funny sidenote. The denialists seems to think the admiral is just saying it to get funding ...

31
The rest / Re: The Iceman
« on: May 03, 2013, 10:40:09 AM »
Yes, he certainly has that druid-thing going for him :)

32
The rest / The Iceman
« on: May 03, 2013, 10:12:07 AM »
His bearded head showed up near that near-permanent area of open water in The Chuckchi Sea. This is from May 1st. The ice almost seems to fall into the hole in that area, so I don't think he will stay around for too long.

33
Comparing this years ice to last years it seems that this years ice in the cracked up areas are of a different quality. I don't think everything can be attributed to thickness alone.

In several areas in for instance The Beaufort and Chuckchi-seas, the cracks last year were more angular and seemed to "fit better" in the pattern left after the cracking events.

This year the cracked areas have several patterns where the floes seem more rounded and the cracks seem messier.

Based on this I would say the ice in the cracked areas generally is softer and more prone to crumbling than it was on May 8th 2012. It's a general impression I get just by comparing images in eos worldview.

Granular uneven cracks and varying floe-sizes (2013) vs. angular even cracks with more uniform floe-sizes (2012), might be one way of expressing what I'm thinking about.

Has anyone else got the same impression?

34
Consequences / Re: When and how bad?
« on: April 17, 2013, 03:15:18 PM »


I took a Physical Geography course before global warming was a concern and according to basic science every one of those feedbacks was in play during times leading up to a glacial max or an interglacial thermal max. Albedo changes are positive feedbacks in cooling and warming, just like all other feedbacks are. They all involve basic science of how the Earth behaves.

You don't see any similarities and everything that is happening has happened like this before and we know it as a fact. This is not the first time the arctic sea ice has melted, so if warming continues, the Earth will respond as it has in the past.
I must have been unusally unclear. I thought I wrote that the feedbacks are similar, although I doubt they will be identical. However, the initiating forcing is radically different, and I can't see how you've argued against that.

Quote
The primary source of warming or cooling is never the only source. Warming or cooling always makes changes to all the other things that cause forcing. You can't warm or cool without changing the albedo of the Earth. You can't warm or cool without changing the greenhouse gas concentrations of the Earth. You can go down the list and all things that cause radiative forcing come into play. There is no rule that something only minorly contributing to warming or cooling today has to stay that way tomorrow. The 24/7 comment doesn't make sense, because it's always continuous radiative forcing, even if it's negative or zero.
Have I ever stated that the primary forcing was the only source? Regarding feedbacks, see above.

The 24/7 comment is just about the difference between an orbital forcing and an atmospheric one. Maybe I should have called it something else, like a 24/7/365/360 degree forcing.

The orbital forcing in question during the HTM caused a redistribution of insolation on the planet. This to me seems like a major difference. I agree with the previous poster however - paleoclimatology can tell us  a lot about the boundaries of climate change under different forcing regimes. However, it tells us very little about the transition to such a boundary or equilibrium in our current situation. There is one other factor that means we cannot trust the HTM as a guide to equilibrium conditions under the current regime. During the period with the highest insolation, several thousand years prior to the HTM, there was still quite a lot of ice covering the planet. So the albedo-feedbacks would be very slow compared to todays situation. One thing that hints at this is the fact the HTM occurs several thousand years after the time of max insolation.

Quote
I don't know what you mean about 7% more insolation, unless you are talking about the difference in insolation between the max and min of Milankovitch Cycles, which I thought was 6% in the HTM. We shouldn't be far from the max today, so the Northern Hemisphere insolation isn't that much different now than what it was during the HTM. Presently, less than a third of the radiation absorbed by the Earth's surface comes directly from the sun.
Well, July insolation at 65N decreased by app. 50 W/m2 throughout the Holocene. If I remember correctly we are about halfway between max and min now.

Quote
When someone is saying the Earth's seas will boil and the Earth will become like Venus, it's science fiction and not science.
I totally agree. And I if had said something even remotely like that I trust you would let me know. For the moment I don't see the relevance of neither Venus or boiling seas to our discussion.

Quote
It isn't science to claim the global temperatures are warmer now than they were during the HTM.
Of course not. Good thing I never compared todays temperatures to those of the HTM then.  Again, you seem to be reading a bit too much into my post.

Quote
The winters in Scandinavia during the HTM were mild enough to allow the treeline to be further north and that is true throughout the Northern Hemisphere.
For the dominant species of birch and pine that are de facto at the tree lne, winter temperatures is not the main limiting factor. Snowfall, length of growing season, wind, nutrients and other factors are.

Quote
The albedo of a forested area is much different with snow cover than a tundra. The albedo of a temperate forest and the conditions to have one are different than a boreal forest, so oak trees in Scandinavia during the Eemian prove a much warmer climate. Since it's a scientific fact these things occurred during interglacials, it's also a fact it will happen again if it's warm long enough. The primary condition that allowed more radiative forcing during the Eemian was the Earth's tilt, but that condition isn't required to cause enough radiative forcing to let it happen in the near future. It's the summation of radiative forcing that matters and not an individual component. For example, aerosols have a negative radiative forcing and their effect has a large margin of error. That means that aerosol pollution is masking some of the warming from greenhouse gases and you can see how they subtract from the sum and create more uncertainty in the estimates.
I agree with most of what you're saying. However, the difference between GHG-forcing and its orbital counterpart still stands. Comparing to the HTM again, that was in fact a situation when the orbital forcing was waning, while the feedbacks we're playing catch-up and eventually became the main cause of warming. Today we have a growing GHG-forcing and the same feedbacks that you mentioned above.

Quote
The science does not support the Earth warming and giving up massive amounts of methane, it supports mankind doing it.
Can science rule that out while we are on our current emission-trajectory? Please keep in mind that we are experiencing changes in the cryosphere that we have no analogue to. It's all unknown terrain from here. All I know is that rapid changes in the cryosphere seem to go hand in hand with major climatic upheaval for lack of a better word.

Quote
Comparing past CO2 levels to present isn't very meaningful, because the Earth is responding to net radiative forcing and a very small amount of that is natural forcing. Since the past CO2 levels didn't have other anthropogenic greenhouse gases and aerosols with them, the whole picture has to be compared.
I completely agree. That's why I think we need to accept that we are on a completely different path than the one that moved the climate between glacials and interglacials. It's just not a very comparable situation.

35
Consequences / Re: When and how bad?
« on: April 16, 2013, 08:17:53 PM »
In my opinion paleoclimate - almost regardless of how far back you need to go to find an ultimate greenhouse analog - is valid for setting upper limits for change. To that extent I think I would agree with ggelsrinc.

Where I would tend to disagree is perhaps in terms of the severity of the threat to civilisation, rather than to that of a habitable (in some regions at least) planet. I also think focussing on the end state implied by paleoclimatic periods is to overlook the rather important matter of the transition process.
Not much to disagree with here. The transitions are what worries me the most as well. The Pliocene Warm Period was probably not a bad state for the world to be in for us humans. But the transition to and from such a state is a completely different beast.

My main point is that we cannot expect the transition in the cryosphere to be similar to that of the HTM, simply because the distribution of energy is so different. When it comes to permafrost in particular I fear that higher winter and spring temps, reduced snowcover on the tail-end of the freeze-season, reduced refreeze as well as a longer thawing season as we see now is fundamentally different to the orbitally induced forcing of the HTM.

The tree line in my part of Scandinavia is already where it was during during and a while after HTM, if we correct for isostatic rebound. The trees just haven't grown big enough yet, and some species are (still) missing. But we have more than enough heat in the system to make sure that the changes we have seen  so far are just the beginning. But then I probably don't need to convince anyone here about that :)

36
Arctic sea ice / Mechanical tipping points - are we seeing one now?
« on: April 16, 2013, 06:53:05 PM »


First time poster here. I decided to jump straight in.

I've been following the blog since last season, while becoming a more and more avid ice-watcher since I started noticing the changes around 10-15 years ago. I'm a complete amateur when it comes to the science of ice, oceans and hydrology.

I hang around in the sub-arctic quite a lot, and the changes in wildlife, vegetation, natural cycles of insects, spring run-off etc has changed tremendously in the areas i frequent. I was born and grew up between 69N and 78N. That background has given me the opportunity to experience a lot of ice-offs, both in fresh and salt water.

Looking at the satellite images and the cracking I'm reminded of what it's usually like when you wait for ice-off on an alpine lake north of the polar circle.

When the ice cracks and takes on a more porous character one early morning, it's usually completely gone the next day. Ice-fishermen have been forced to swim to shore after pitching their tent on what they thought was solid ice.

I believe it has as much to do with mechanics as with how much thermal energy is available to melt ice. What happens IMHO, at least in fresh water, is that as the ice cracks, the surface that water or air can transfer heat to increases exponentially. It's not just the cracks per se. It's also the way the ice turns porous at the onset of melt. This porosity again increases the effective surface of the ice by several orders of magnitude. The porosity also translates to lower albedo.

My gut feeling is that the mechanical and thermodynamic interaction of ice and water, and the way the quality and character of ice changes when at the onset of melt, is underestimated in the models. In particular the extreme increase in effective surface area when the ice first cracks up and then as porosity increases. In addition there is increased surface area for kinetic energy to work, higher drift speed translating to even higher kinetic energy, less resistance towards mechanical forces like wind and waves and so on.

If I'm right 2014 or 2015 at the most seems like a good bet for ice-off considering the current state of the ice, and considering the current trend. Please take into account that ice-off is not the same as ice-free. Ice-off is the last phase before an ice-free state, at least in my vocabulary :)

This isn't based on much besides personal experience with ice, and I realize the limitations of using freshwater high alpine lakes in the arctic as models of sea-ice. Any input would be much appreciated. I have already learned a lot from the ASIB and ASIG, and now is as good time as any to join the eminent ASIF :)

37
Consequences / Re: When and how bad?
« on: April 16, 2013, 06:24:24 PM »
My prognosis is the Earth isn't going to be able to tell how it was warmed, it's going to respond in the same manner as it has in the past.
With all due respect; I believe your prognosis is based on a faulty premise. The forcings that made HTM possible are quite different from what we see today.
Today we see the results of an increased, but relatively weak radiative forcing from the atmosphere. This forcing works 24/7 over practically the entire planet. And then there's feedbacks, like albedo-reductions etc.
The HTM was made possible by a Milankovitsj-forcing and subsequent feedbacks. The albedo-changes might have been similar, but probably not identical due to the different temporal and spatial distribution of the Milankovitsj-forcing compared to a forcing from higher concentrations of GHG's.

In Scandinavia I know that winters during the HTM were just as cold as climatology. Summers however were warmer. This goes for a lot of the Northern Hemisphere iirc.  The way I see it the situation during the HTM, with 7% more insolation the Northern hemisphere, during summer, is quite different from our current 24/7 all-over forcing.

Therefore I see no reason why the climate system in general and the cryosphere in particular, would respond similarly, considering the fact that the temporal and spatial distribution of warmth during the HTM was so different from what we see today.

Let's hope I'm wrong.

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