EM. What total rubbish. You use a value for ice melt from a geothermal flow that you "calculated" from an averaged geothermal flow rate that you somehow constructed from false figures (confusing minimum with minimum average) you assume that this value is constant over time (when it almost certainly isn't) and you assume that from your distant armchair that you have an understanding of Thwaites Glacier dynamics. I was aware of the reference you quote and based my attempt to understand the Glacier upon it. It's not my theory that you so immodestly claim as a failure, it's the interpretation of those who have gathered the data firsthand.
I gave up trying to understand the Glacier when I discovered that the ice floor slopes inland, whereas the ice flows seawards.
I have no further interest in discussing this matter with a back of envelope, armchair sitter with no real understanding of the subject he pontificates upon.

EM & Supertroll

The paper quoted in EM's link is Steig et al 2012. References to the work of Eric Steig find their way into Climate Science blogs quite regularly.

https://wattsupwiththat.com/2012/09/08/rcs-dr-eric-steig-boreholes-himself-on-antarctica/

from the comments
"Geoff, Shevva, Harold and others
Yes, melting of the West Antarctica Ice Sheet adds to sea level. Steig links surface warming in Antarctica generally to increase in sea level. But apart from a few peripheral areas, Antarctica is far too cold to lose ice by surface melting.

The increased outflow of ice into the ocean is thought to be caused primarily by currents of deep oceanwater, itself warmed naturally centuries ago, melting ice shelves from below. Jenkins et al. (Nature Geoscience, vol. 3, 2010), who sent robot submarines under a glacier outlet, concluded that this melting process is continent-wide and has been going on for a long time - too long to be blamed on anthropogenic increases in greenhouse gases."
Sep 8, 2012 at 5:24 PM | Nic Lewis

"Nic -
Switching gears slightly, I was just reading a paper by Schneider et al. on West Antarctic warming in the spring. I was quite surprised to see it use the values from Steig et al. rather than O'Donnell et al.; they mention the latter only in passing as agreeing the large spring trends in WA. Do you have any comment on the Schneider et al. paper?"
Sep 8, 2012 at 6:07 PM | HaroldW

"Harold
I haven't studied the Schneider et al paper in enough detail to comment on its findings, but their use of the Steig results rather than ours (they refer to Steig et al as one of the three major reconstructions of Antarctic temperatures, along with Chapman and Walsh 2007 and Monaghan et al 2008/9, but not O'Donnell et al 2011) seems unscientific to me. Our paper showed that Steig's was mathematically flawed, so that its results could not be correct (except by fluke).

Schneider is an ex colleague of Steig, they have published several papers together, and he (and the peer reviewers - who maybe included Steig) also probably don't like outsiders rocking the boat. So I am not terribly surprised.
Sep 8, 2012 at 6:52 PM | Nic Lewis"

https://noconsensus.wordpress.com/2012/09/07/proof-and-genius/#more-13745

https://climateaudit.org/2013/04/23/steigs-bladeless-hockey-stick/

There are numerous links in the articles above, including to some threads at Bishop Hill.

Steig tried to smear heat from the peninsula all over Antarctica, and blamed it on Global Warming. He failed. Now we know that there is volcanic activity beneath the peninsular, the influence of Steig on IPCC approved Climate Science should be the subject of further review.

Supertroll, unfortunately some armchair experts on Antarctic Ice tend to believe other armchair experts, and then have to be rescued.

Turney must have been advised by the British Antarctic Survey, so how did it go wrong?

https://climateaudit.org/2014/01/15/ship-of-fools/

GolfCharlie. I really do not understand that cross section through the Pine Glacier in the Davies reference that EM provided. Firstly it purports to show positions of the ice edge beneath the ice shelf in 1970 long before any observations could have been made.
Then it shows warm circumpolar water migrating under the ice shelf, there to melt the glacier edge. Since this water lies beneath colder water (which normally would displace it) it must owe its greater density to its higher salinity. So what mechanism drives this water to higher elevations displacing colder but less saline water generated by melting ice? Presumably the ice shelf survives because it is underlain by cold water. The whole system doesn't seem to make dynamic sense to me but perhaps I'm missing something.
Lastly the diagram shows the glacier itself getting higher inland, whereas its base descends in the same direction. This means that the glacier is migrating seaward impelled only by the elevation difference. This force affects the whole ice thickness but at depth the impetus would be vanishingly small. Thinning of the glacier causing inland elevations to diminish should REDUCE the drive causing ice flow rates to diminish, not speed up as has been observed. I just don't understand the dynamics of the glacier either and that diagram is nonsense.

GolfCharlie. Forgot to mention. Steepening of the glacier edge (based on what evidence?) will reduce the contact area between the glacial ice and seawater, reducing the rate of ice melt.

Entropic Man Supertroll and Radical Rodent,

I followed some of the links provided by Entropic Man, which all seem to follow a pattern of what could happen if something else does, based on computer models about processes that are not understood, evidenced by recent observations, in the (almost complete) absence of anything historical (some sea bed sediments)

Try googling "marine ice sheet instability theory" In the same way that "ocean acidification" has been a gold mine for marine biologists, trying to get research funding out of the climate science band wagon, so marine ice sheet instability theory carries a lot of hope for glacier and sea ice experts, who can see that sympathy for drowning polar bears has cooled.

There are gems like this:
http://www.sciencemag.org/news/2015/11/just-nudge-could-collapse-west-antarctic-ice-sheet-raise-sea-levels-3-meters
"Over the past 40 years Pine Island Glacier in West Antarctica has thinned at an accelerating rate1, 2,3, so that at present it is the largest single contributor to sea-level rise in Antarctica4. In recent years, the grounding line, which separates the grounded ice sheet from the floating ice shelf, has retreated by tens of kilometres5. At present, the grounding line is crossing a retrograde bedrock slope that lies well below sea level, raising the possibility that the glacier is susceptible to the marine ice-sheet instability mechanism6, 7, 8. Here, using three state-of-the-art ice-flow models9, 10, 11, we show that Pine Island Glacier’s grounding line is probably engaged in an unstable 40 km retreat. The associated mass loss increases substantially over the course of our simulations from the average value of 20 Gt yr−1 observed for the 1992–2011 period4, up to and above 100 Gt yr−1, equivalent to 3.5–10 mm eustatic sea-level rise over the following 20 years. Mass loss remains elevated from then on, ranging from 60 to 120 Gt yr−1."

Supertroll

As you say, you were a professional geologist. That makes your lack of wit even more embarassing. I will critique you performance later, but first I will answer your questions.

My estimate of geothermal ice melt volume was simple. Multiply the wattage per square metre by the number of seconds in a year to get the amount of energy in Joule/m^2/year. Multiply by the area of the glacier in metres and divide by the latent heat of freezing. Finally divide by 10^12 to convert from grams to cubic kilometres.

Since the paper did not give an average heat flow I did two calculations, one based on the minimum heat flow and one based on the maximum. This gave minimum and maximum bounds for the ice melt. To give your hypothesis the best chance, I used the maximum melt figure in the discussion. Kindly explain why this technique is invalid.

Regarding changes in geological heat flow, I asked for data on the observed heat flow from other rift systems, hoping that an expert geologist like yourself (Yes, in view of your poor professional performance, I am being sarcastic) would be able to quote typical values and give examples of observed rates of change in heat flow with time You gave me nothing.

To obtain the volume of water released when the lakes drained I used the change in elevation data from the link. They said that an area 20km by 40km rapidly lost 20 m elevation.. That is 16 cubic kilometres. Again, please explain why my calculation is invalid.

The profile of a glacier and it's tongue can be surveyed in a variety of methods Satellite and airborne radar gives surface elevation. Sound reflection gives the profile of the tongue underside and the sea bed.

Boreholes can confirm ice thickness and sea bed profile by direct measurement, while measuring the temperature and salinity profile of the water below the glacier. You can even send an ROV under the tongue.jk

You are correct that the flow under the glacier is driven by changes in density. Meltwater from the underside of the tongue is cold but the low salinity gives it a low density. It flows out along the tongue and forms a cold cap on the sea surface. To replace it, warmer, denser, more saline bottom water flows in carrying heat which continues the melt.

If you are wondering where the warm, dense CBW comes from, remember how the thermohaline circulation works. Warm water is carried North into the Greenland Sea. Evaporation cools the surface water and increases its salinity. This saline water then sinks and flows South along the sea bed as a deep water current which is as dense as the 4C bottom water around it, but several degrees warmer. A similar process forms the CBW in the Southern hemisphere.

Yes, a more vertical slope will have a lower surface area and absorb less heat. Depth for depth a surface at 45 degrees will have 41% more surface area than a vertical surface.and melt faster given unlimited energy. In practice I suspect that the limiting factor is flow rate of the CBW rather than the surface area of the ice at the grounding line.

Why should a reverse slope stop ice flow? Precipitation adds ice to the top of the glacier and fills up the basin. Eventually the basin is full and ice flows over the lip into the Amundsen Sea. You are talking about a corrie on a larger scale. The reverse slope creates extra friction at the base of the glacier so there would be more shear. There would be a bigger difference between the speed of flow at the surface and at the base than you would expect of a glacier with a normal slope.

The real worry is that once the grounding line retreats past the lip of the basin, warm CBW will flow downhill into the basin and produce a step change in the melt rate.

Now for my critique.

Overall, your performance as a professional scientist has been poor. You have made a number of claims about geological heat flow which you have not been able to back up with data. You show a lack of understanding of straightforward physical processes such as heat transfer, friction and ice flow. You attack the whole concept of inference and complain when I use straightforward calculations to infer extra information from available data. Finally you make unjustified allegations of a conspiracy between fellow professionals to fiddle glacier data. If you did all this in a professional setting you would be laughed off the stage.

"....... a conspiracy between fellow professionals to fiddle glacier data. If you did all this in a professional setting you would be laughed off the stage.

Oct 9, 2017 at 12:42 PM | Entropic man

But Eric Steig is still welcome on the worldwide stage of Climate Science?

Climate Science does not retract its own, preferring to make accusations against others.

Wow that's told me than. I bow to the superiority of an ex-science teacher.

Estimate of geothermal heat flow melting
This from someone who confuses minimum with minimum average, who accepts values of heat flow based upon a model that is not explained, who converts all of this heat flow into melting ice rather than disseminating some (much?) of it into raising the temperature of the ice column. The paper did give an average, it said the minimum the average could be was..., not the minimum was... I repeat it's not my hypothesis, merely an explanation that seems to me to be the most reasonable.

Oh silly me, of course its just a large cwm. That works of course because there is a steep slope between the upper part of the depression and the lip. Somewhere on Thwaites Glacier there must be similar but much larger slopes. I wonder where they are?

I am not wondering where the CBW comes from (you must have dozed off about here. Is your armchair comfortable? I was wondering how warmer but denser more saline water could migrate upwards to displace less dense water beneath the ice shelf. The diagram offers no explanation of this magic.

With respect to obtaining data on elevations, subsurface profiles and the like, of course but you are not using this, just waving your arms in the air and making your long suffering abacus red hot. BTW you appear to be mixing up glacier, ice shelf and tongue.

Regarding changes in geothermal heat flow. It logically follows that during an eruption flows will be maximal and will markedly decline after the magma chamber has drained, only to increase as more magma is generated. Large areas of West Antarctica have variable heat flow rates (values more than three times the average crustal values not uncommonly being quoted) indicating the presence of magma chambers - some being full, others in which magma is accumulating). It is inconceivable that an area of thinned crust like much of West Antarctica would have a stable thermal regime. But it's true I failed to provide evidence so I must submit to your armchair acquired expertise.

I never disputed your calculation of the volume of water drained from the subglacial lakes, but tell me oh wise one, in what direction did the water flow. If seaward then it would need to flow uphill. Possible but needs a pressure field that the current interpretation is busy decreasing (yet ice flow rates are increasing). Strange that.

To.be continued

Gremlins hit my last post disappearing a short paragraph on cwms (= corries). So I quickly posted what I had only to find that missing para somehow mysteriously transferred itself to an earlier position.

If ice is forced uphill a greater thickness of ice is forced to occupy a smaller space so that either transport rates have to increase or the elevation of the glacier surface must rise. If flow rates increase then there must be more shear and more energy expenditure. Where comes this energy? If the elevation rises then flow has to be uphill, requiring greater energy. Wherefore cometh said energy. Unfortunately the elevation of the entire glacier is being lowered making the problem even more difficult. Oh armchair wizard, where oh where am I going wrong?

Critique
"Overall, your performance as a professional scientist has been poor."

But mighty one I no longer am a professional scientist and clearly am declining fast. I can only apologize for my intemporate scepticism of calling into question your most impressive calculations.

"You have made a number of claims about geological heat flow which you have not been able to back up with data".

Guilty milord, but I couldn't be arsed. Reasoning partially given in previous post.

"You show a lack of understanding of straightforward physical processes such as heat transfer, friction and ice flow".

Really? I think you should look in a mirror more often.

"You attack the whole concept of inference and complain when I use straightforward calculations to infer extra information from available data".

I do? How very impertinent of me to question your data and the relevance of your calculations. I find myself in good company. Strange that when I infer variations over time in geothermal heat flow you attack that (goose sauce and gander?)

"Finally you make unjustified allegations of a conspiracy between fellow professionals to fiddle glacier data'.

I did? Must be getting Alzheimers.

" If you did all this in a professional setting you would be laughed off the stage."

Never happened before, but there's always a first time. Ever been laughed out of a classroom? Children can be so cruel and will find out any weakness.

Cleanse thyself of bile EM and you will feel better.

"The real worry is that once the grounding line retreats past the lip of the basin, warm CBW will flow downhill into the basin and produce a step change in the melt rate."
Oct 9, 2017 at 12:42 PM | Entropic man

Just how warm is this "warm CBW", and how much of it will flow downhill until the basin downhill is full? Then what will happen according to "marine ice sheet instability theory" that is based on computer models?

Is this really a real worry worth worrying about, or do you need to ask someone first?

Oct 9, 2017 at 5:11 PM | Supertroll

If only EM could find a Climate Scientist who could remember how it was agreed that CO2 was the Earth's Temperature Control Knob. Unfortunately Climate Scientists who were around at the time can't remember, and none of them can find their notes from the meetings.

Some of these Senior Climate Scientists are now trying to support claims that "Exxon Knew", when Climate Science was still talking about a new Ice Age.

The memories of Climate Scientists hold little of use or value.

A paper discussed over at No Tricks Zone claims that a doubling of CO2 will produce a temperature change insignificant compared to natural variability. In passing, the paper criticises the lack of data, the quality of the data and the abuse of data at the hands of climate scientists.

"... the paper criticises the lack of data, the quality of the data and the abuse of data at the hands of climate scientists."

Oct 9, 2017 at 7:02 PM | Schrodinger's Cat

Mann's Hockey Stick has been difficult to replicate, though Climate Scientists keep trying.

For more on the integrity of Climate Science and Eric Steig (Ice Expert):
http://bishophill.squarespace.com/blog/2011/2/8/steig-snippets.html

and this comment provides an introduction:
Feb 8, 2011 at 9:42 AM | lapogus

Supertroll

Tell me again about the AGW Thought Police, and how they force authors to conform.

How is it possible for water to flow over a weir when the river bed is lower than the lip of the weir?

Understand that and you will understand how ice can flow over the bedrock lip separating the Thwaites basin from the Amundsen Sea.

Look at the profile of the Thwaites basin and ice in graph d) here.

The bedrock lip, the grounding line at the seaward end of the basin, is 700m below sea level. That allows a tongue at least 700m thick to flow over the lip. Inland the bed is up to 1700m deep, but covered with 2700m thickness of ice. Plenty of scope for ice to flow downhill to the sea.

How can the water under the ice flow uphill to the lip? Hydraulic pressure. The weight of the overlying ice produces more than enough pressure to force water uphill from the basin and into the sea under the ice flowing over the lip.

"Tell me again about the AGW Thought Police, and how they force authors to conform".

EM. You badly need a refresher course in Climategate.

"How can the water under the ice flow uphill to the lip? Hydraulic pressure. The weight of the overlying ice produces more than enough pressure to force water uphill from the basin and into the sea under the ice flowing over the lip".

Well in the same manner that you treated me, can you supply me with evidence that hydraulic pressure causes water to flow uphill in the Thwaites Glacier? Recall that it's not actually hydraulic pressure that causes liquids to move, but a hydraulic gradient. Clearly the presence of subglacial lakes indicated gradients were for a time towards the lakes, but at some point changed allowing them to drain (towards the sea?). Oh great one, has your armchair science discovered a reason?

Also if meltwater is being driven upslope towards the sea by a suitably oriented hydraulic gradient, why are climate alarmists getting their knickers in a twist about seawater migrating downslope there to melt the base of glaciers, thereby destabilizing the whole of West Antarctica and raising sealevel a bundle. Surely this deadly seawater cannot flow against your hydraulic gradient? Perhaps you should write to these eminent glaciologists and tell them that your armchair says there's nothing to worry about.

Concerning the cross section you incorporated in your post. The only way the lower ice can migrate seawards is either for the entire glacier to speed up or for it to expand laterally in the third dimension. Otherwise the lower part of the ice would remain stagnant. If you look carefully EM you can even see this effect in a weir. Flow across the weir increases, and upstream of obstacles flow may markedly slow or even reverse. Each year people get trapped and drown in weirs because of this effect. I never said ice couldn't flow uphill, merely that the lower parts might be almost stagnant (unless the hydraulic gradient caused by elevation differences were sufficiently high. I also pointed out that reducing the overall ice thickness, which would imply a lowering of the ice surface, would reduce the drive (= hydraulic gradient) causing ice flow rates to lessen. Yet from all accounts flow rates are speeding up. Can your mighty armchair supply enlightenment rather than spewing insults?

I have expressed my inability to understand how the Thwaites Glacier operates, yet EM you fail to understand the problem and accuse me of lacking an understanding of basic physics. I worry about you sometimes. Not often.

Schrodinger's Cat I apologize for my part in taking over your most interesting discussion thread by a topic having nothing much to do with CO2.

EM. Widespread wlplparm ice at the base of the Thwaites Glacier is inferred from a radar attenuation study

https://www.cambridge.org/core/journals/journal-of-glaciology/article/adaptively-constraining-radar-attenuation-and-temperature-across-the-thwaites-glacier-catchment-using-bed-echoes/83A84DF184CD3E2434428F4E2333C43F

Where this "warmth" occurs away from the seaward edge of the glacier, where does this warmth come from? Not from the ocean, nor from CO2 driven global warming?

Supertroll, implausible deniability walks hand-in-hand with GHG Theory, Step by Step.

Steig introduced data smearing to Antarctica so soon after Climategate, with full support from Real Climate and the usual suspects in the defining of what Climate Science is.

Steig is still quoted as an authoritive expert in papers that Climate Science relies on, as EM has just proved.

It could be that Steig is 97% correct, but......

Oct 10, 2017 at 10:16 AM | Supertroll

I think this first part of the Abstract of the paper you linked to, provides a summary of so much that is wrong in Climate Science.

Abstract

"Englacial temperature is a major control on ice rheology and flow. However, it is difficult to measure at the glacier to ice-sheet scale. As a result, ice-sheet models must make assumptions about englacial temperature and rheology, which affect sea level projections. This is problematic if fundamental processes are not captured by models due to a lack of observationally constrained ice temperature values."

Supertroll

Perhaps you should be asking what impedes ice and water flow.

I live among the glacial deposits of County Tyrone, including eskers left by flow channels under the ice.

Similar channels have been mapped under Thwaites. Glacial lakes, both under the ice and downstream of the ice edge on land are intermittent features. They grow when their drainage channel is blocked and disappear when the blockage breaks. This is normal behaviour. Why do exclude this as a mechanism?

It is quite possible that there is stagnant ice at the bottom of the Thwaites basin. It is also possible that the lower ice is squeezed out horizontally by the weight of ice above it. Around the inland margin of the basin horizontal flow rates at the surface are very low, yet the ice thickness is not increasing with time. Where is it going?

Two options. It is melting or moving downwards. There is not much surface melting so it must be moving downwards. If it is moving downwards then the ice at the bottom must be melting or moving sideways. We have discussed melting already and it is not enough, so we are left with basal ice flow.

You can see from the ice flow maps that the surface rapid ice flow is along a path starting in the middle of the basin and flowing towards the sea. This is consistent with ice flowing from the margin towards the centre under the surface and then towards the sea. Think of the ice as a viscous fluid subject to the usual rules of fluid flow.

Regarding CBW flow under the ice. Under the tongue the water stratifies with the low density meltwater water close to 0C on top and the denser CBW at 7C underneath. Since the thickness of the tongue decreases as you move seawards the low density buoyant meltnwater flows upwards and outwards and the denser CBW moves in along the seabed towards the grounding line to replace the meltwater. With the CBW comes heat.

Similarly in a flow channel which opens at the grounding line. Low density meltwater flows upwards and outwards along the roof of the channel while saline CBW flows downwards along the base of the channel.

Why are you looking for extra energy? As discussed earlier, geothermal heating plays only a small part in the ice loss. 99% of the ice loss from Thwaites is ice flow out into the Amundsen Sea, with the increasing loss presently due to the decreased butressing as CBW melting shrinks the tongue.

What is wlplparm ice? I've never heard of it and nor have my search engines.

Supertroll, golf Charlie

I read Schroeder at al (2016)

For golf Charlie, this is an example of using observation to validate model predictions. Perhaps you should have quoted from the conclusion.

"We find that this approach is capable of capturing the catchment-scale attenuation-rate structure predicted by the ISSM numerical ice-sheet model. The greatest difference between estimated and modelled values occurs in areas with large slopes in bed topography; however, even this difference falls within the estimated fitting error of the technique."

For Supertroll, how do you convert from attenuation to temperature? The paper mentions that the base of the ice is warmer, as would be expected, but does not say by how much.