- Date published:
6:00 pm, May 11th, 2009 - 20 comments
Categories: climate change - Tags: antarctica
In east Antarctica, the sea ice sheets have been larger recently. Predictably this has been seized on by the scientifically simple-minded climate change deniers (CCD’s) as evidence that climate change models are incorrect. This is despite it being predicted very closely by the same climate models well before it happened. I remember it being pointed out as a counter-intuitive effect in the 1990’s (no link I’m afraid) of global warming. Hypothesis, prediction and confirmation are the essence of the scientific process. Finding a predicted effect happening tends to confirm an hypothesis rather than refute it.
Increasing greenhouse gases cause climate change, but not always climatic warming in particular areas. As the climate patterns change, some areas will get a lot colder as the overall world climate heats up. It all depends on that the weather patterns and ocean currents do in response to the changes in heat balance shifts. The heating and desertification of the tropics during temperate latitude glaciations is a similar counter-intuitive effect of weather pattern changes.
In this case as Adding Noughts in Vain points out in a post (note that sea ice sheets are NOT the same as the more important ice shelfs pictured right and discussed below)
Why does increasing Antarctic sea ice not challenge current scientific thinking about global warming? I’ll defer to the US agency the National Snow and Ice Data Center
“Another important point is that the increase in Antarctic sea ice extent is not surprising to climate scientists. When scientists refer to global warming, they don’t mean warming will occur everywhere on the planet at the same rate. In some places, temporary cooling may even occur. Antarctica is an example of regional cooling. Even our earliest climate models projected that Antarctica would be much slower in responding to rising greenhouse gas concentrations than the Arctic. In large part, this reflects the nature of the ocean structure in Antarctica, in which water warmed at the surface quickly mixes downward, making it harder to melt ice.
In terms of sea ice, climate model projections of Antarctic sea ice extent are in reasonable agreement with the observations to date. It also appears that atmospheric greenhouse gases, as well as the loss of ozone, have acted to increase the winds around Antarctica. Perhaps counter intuitively, this has further protected the Antarctic from warming and has fostered more ice growth.
The one region of Antarctica that is strongly warming is the Antarctic Peninsula, which juts out into the Atlantic Ocean and is thus less protected by the altered wind pattern. The Antarctic Peninsula is experiencing ice shelf collapse and strongly reduced sea ice.”
Adding Noughts goes on to explain that the east Antarctica sea ice sheets aren’t that important in sea level calculations because they routinely break up in summer anyway and float away. They’d be of interest for climate change model if they remained in place over summer because that would constrain the flow of ice from the ice streams on land behind them.
The opposite effect has shown in the west Antarctica Peninsula ice sheets where the disintegration of relatively permanent ice shelfs have produced an increase in the speed of the ice-streams behind them. After the final breakup of the Larsen B sea ice sheet in 2002, there was a marked increase in the flow of the ice streams in that area (as had previously been observed in 1995 final breakup of the Larsen A sea ice shelf). This has resulted in considerable mass wasting across the ice streams on the Antarctica Peninsula as each of the sea shelf disintegrated.
There is a very good discussion of ice shelf disintegration at the NSIDC. The one to watch is the Ross ice shelf which is the exit point for the West Antarctica Ice Sheet (WAIS), which is fortunately still inside the stronger weather pattern around Antarctica.
The Ross Ice Shelf is the main outlet for several major glaciers from the West Antarctic Ice Sheet. This single ice sheet contains enough above-sea-level ice to raise global sea level by 5 meters. At present, the Ross Ice Shelf’s mean annual temperature is well below freezing. Although summer temperatures in the warmest part of this shelf are currently just a few degrees too cool for the formation of melt ponds, there is no evidence of a strong warming trend on the Ross Ice Shelf at this time.
If summer temperatures start to rise in this area as has happened over decades in the Antarctica Peninsula, we’re likely to get the same kind of breakups. Apart from the immediate drowning effect, there is a real risk that it would increase the speed of the WAIS.
The West Antarctic Ice Sheet(WAIS) is a unique marine ice sheet, anchored to bedrock, and in places it dips thousands of metres below sea level with margins that are floating. Other marine ice sheets existed in the Northern Hemisphere during the last glacial maximum but all disintegrated and melted away during the current warm period. The West Antarctic Ice Sheet is the only marine ice sheet remaining from the last glacial period.
The resulting mass-wasting of the WAIS after the Ross ice shelf disintegrated (as has been seen in the Antarctica Peninsula) would then start to cause some serious sea level rises. What has been shown is that once one of these shelves breaks up, everything happens rapidly.
Now to stop being so rational and enter the same space as the idiotic writings of some CCD’s. Fortunately for the BustedBlonde, her liver should have given out from gin poisoning within the decade long before any of this happens. Probably no real loss, as her brain looks like it is long gone already from her limited understanding and shallow pronouncements on climate change. If she isn’t getting the DT’s on schedule, she should get a lot more water in her gin over the next couple of decades because some of these effects look like they’re starting to feedback on each other.
The resulting mass-wasting of the WAIS after the Ross ice shelf disintegrated (as has been seen in the Antarctica Peninsula) would then start to cause some serious sea level rises
You are obviously scientifically illiterate to make such a statement.
I suggest you check out Archimedes principle before posting on this topic again.because as it is you look more foolish than those you criticize.
Andrei, you’re new here, welcome to The Standard.
You should know that a lot of the debate here is well informed. Make quite sure you know what you’re talking about before you accuse other people of foolishness. In particular, you should be aware that the author of this post, lprent, knows his climate science.
In this case the mistake is yours. The Ross shelf floats, Archimedes applies. But the post refers to the West Antarctic Ice Sheet (WAIS), which doesn’t float, and will cause sea level rises as stated.
In this case the mistake is yours. The Ross shelf floats, Archimedes applies. But the post refers to the West Antarctic Ice Sheet (WAIS), which doesn’t float,…
“if your enemy is hungry, feed him. For if he is thirsty, give him a drink. If you do this, you will pile burning coals on his head.”
Indeed so but the major part of West Antarctic Ice Sheet that is not floating is well below sea level and a curious feature of H2O is that in its solid form it has a lower density than when in liquid form (hence ice floats).
Therefore the melted WAIS would take up less volume than today’s solid WAIS. So rather than adding to sea level rise it could potentially lower it as the oceans fill the void in the basin it currently inhabits.
Its all hypothetical anyway because its not going to happen in our lifetimes nor nor anytime in the foreseeable future
So rather than adding to sea level rise it could potentially lower it as the oceans fill the void in the basin it currently inhabits.
Yeah nice try at a recover, but contradicted by the experts who actually know something about it. From the Wikipedia link WAIS above:
Its all hypothetical anyway because its not going to happen in our lifetimes nor nor anytime in the foreseeable future
You continue to be just as wrong as wrong can be. Read the Wikipedia stuff. It’s happening now.
I suggest that you do, and please read the post and background materials.
In particular the height of the WAIS and its average depth, and its probable volume above sea level. It is going to give you a shock.
You are obviously scientifically illiterate to make such a statement
No it’s exactly right
Suggest you do a little research
We wondered where the traffic to roarprawn was coming from. Keep the debate up – debate is good. Drinking is better though. Sort of loosens you up a bit and may we recommend that you drink more often – you see better after a couple of gins. And we are happy being shallow – less likelihood of drowning… hugs and kisses
PS Anyone over here know Rangi Kemara?
Poor taste drinking gin. When I used to drink spirits it was always a single malt scotch. However it eventually it interfered with learning and programming too much, so was left behind with my other youthful pursuits like playing ‘tag’ or ‘bottles’.
How do we measure historic sea levels when land masses are also sinking and rising over time?
Fortunately the sea level at one point in time is close to being the same world wide and block faulting and other geomorphological deformation tends to be site specific. So the only real issue is to date and look at averages.
Look at numbers of sites with coastal features across geographical regions and date them – typically using carbon dating in buried seashells and other techniques. You can eliminate sites with obvious signs of block faulting.
The average across sites world-wide at roughly the same time will give a pretty accurate measure. The further back in time you push this the less accurate it gets. Firstly because the inaccuracy of the dating techniques errors increase, and secondly because there is more geomorphological movement. Therefore you need more sites.
However the sea level history above our current levels has been pretty well established for the last couple of million years during the Pleistocene and Holocene. The lower sea levels (during glaciations) have had less sites currently available, and those mainly block faulted upwards. So I’d guess they are still pretty inaccurate.
It is tricky, but they’ve been doing this particular task decades before I was at uni the first time in the late 70’s.
Is this research to improve the accuracy of your new site? It needs it. 😈
So the short answer is we can’t accurately determine mean sea levels over time.
Imagine if I spread 10cm of rocks over the bottom of my bath and just covered them in water. If I then pushed all the rocks into a pile I could conclude that the water level has dropped because there would be rocks sticking out of the water and the water level would have dropped relative to the top of the bath.
Ok one more question lprent. Given that three quarters of the planet surface is water, if sufficient land based ice were to melt causing a 6m increase in sea levels there would need to be an average of 18m of ice covering all land as we know it today. If the land based ice were evenly distributed across all land would it be 18m thick?
Nothing in science can be said to be 100% accurate. Your average physicist will not give you an absolute assurance on really basic matters such as constants like the speed of light or that gravity on earth is a constant when you are looking through time.
What you’re looking for is a reasonable level of certainty under the conditions of what you are using as a framework.
I’m afraid that you have to leave absolute certainty to people of faith who have an ability to ignore evidence that challenges their beliefs. Of course some people still have faith that the earth is flat. Or probably in your case that climate change is not happening despite any evidence to the contrary.
If the land based ice were evenly distributed across all land would it be 18m thick?
It isn’t evenly distributed, and never has been as far as we know (nearest would have been if the Snowball Earth hypothesis actually happened). However ice is many 1000’s of metres thick over large areas in Antarctica and Greenland. For instance the Vostok core in Antarctica was 3623 metres. It isn’t the deepest area (and I don’t think they hit bottom – but I could be wrong).
I presume that there is some illogical reason for the question? You sound like someone looking at a thought experiment like a perfect black body or a sunflower world. They’re useful for determining the extremes of a vastly simplified system, but not for any system with multiple complex factors causing chaotic effects.
No, the short answer is we can.
I like your line of reasoning though – it smacks of desperation when people stop arguing that the warming isn’t happening, and instead begin to dispute the effects. I have a mental image – a slight loosening of the finger in your left ear, and maybe a flicker of a tightly shut eyelid.
BTW Antarctica – land area 14m km/2, average ice depth 1.6km. (that’s 90% of all ice)
Earth – 148m km/2. So antarctic ice over all land would be about 160m. I think…
Maynard: burt is attempting the Wishart style of argument (seen here many times) which is less concerned with finding out information than it is with getting people to admit certainty, which they then argue is a sign of faith rather than science. If you admit to uncertainty then they argue that since the outcomes are unknown we should just carry on what we are doing.
What they hate is the norm of science which is ‘grey’ – looking at reasonable degrees of certainty on outcomes and relative risk levels.
It is one of those really boring techniques that the CCD’s have come up with so they can stop arguing about evidence and argue about people – which is where they feel comfortable. Personally I’d just wish that they’d expend some of that considerable effort simply doing some learning.
Lprent, I know, those who profited from soft coal, DDT, thalidomide and tobacco followed the same pattern, as did the corporate sycophants and useful idiots who supported them out of ideology.
And how much would the temperature have to rise to in Antartica for all that ice to melt …. just wondering ?
No-one really knows, obviously we haven’t seen it before except what has been observed at the Peninsula. There was a 5C change there over 50 years, and after about 30 years the ice-shelfs started breaking up. However that was with a slow effect of about 0.1C increase per year on average. A faster temperature rise is likely to get faster effects.
Problem is that the gas buffering into the oceans that has been largely protecting us isn’t coping with the massive increases over recent decades. The oceans are getting much more acidic more rapidly (which is pretty freaky when you consider how much they have to adsorb to show those effects). That means oceans are unlikely be as effective at adsorption in the future. The question becomes how long the temp rise outside Antarctica in both air and sea temperature goes without disrupting the weather pattern that is keeping most of Antarctica in the deep freeze.
About 2-3 degrees regionally at the Ross shelf would probably be sufficient over a few decades. That seems to be sufficient to cause the ice shelf to get surface melt pools, and under-side mass wasting. At least that is what seems to have happened in the Peninsula. That eventually leads to a breakup of sections. Outside of the current weather pattern around Antarctica there is a pretty strong temperature gradient – at least 5 degrees in summer. So it really depends on if anything disrupts that weather pattern.
But it is more likely that an earlier sea level rise from the rapid melt-off of Greenland icecap (which appears to be proceeding) is going to cause a breakup in the Ross shelf. Ice floats, cracks and would cause mechanical wasting. That would melt causing more sea level rise etc… etc… Nasty feedback effect.
Whole thing is way too risky. I suspect that one way or another we’ll find out over the next 20-30 years if not sooner. Whatever happens, I suspect that once started it will only take a decade to get rid of the Ross and other shelfs. That releases the brakes on the ice streams behind them (like the WAIS). Eventually we start getting ice wasting in the cap.
Fortunately there don’t appear too much happening in East Antarctica. That would give a *lot* of water. But there is no way to predict the potential feedbacks accurately. We’re already beyond the worst projections of the IPCC for effects.
Thanks for the plug, lprent.
Good post. I was digging around on the east Antarctica sea ice when I saw your post. That helped a lot reduce the hunt a lot.