UKC

This week's Friday Night Video is bound to make some palms sweaty. Scott Adamson sets off on a pitch of outrageously thin ice that becomes thinner the higher he gets. As raw footage goes, this is pretty terrifying!

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Yet he seems to remain remarkably composed throughout

Effectively soloing on ice that thin while it's in the process of melting? I'm no ice climber but I'd say this guy doesn't have long to live in statistical terms.

Adamson did die on the Ogre a year or two after this was filmed, but nevertheless thin ice can be surprisingly climbable, it's just obviously not protectable. If it's not that steep, it's not even particularly hard as you aren't swinging or kicking as much as on thicker ice. With thin ice it has generally formed at same time (i.e. over one cold day, so it doesn't have layers in it as later season ice does. That make judging it easier as it tends to be very consistent.

I didn't know that. But I just had a quick read. Apparently the first attempt saw him break his leg after a 30m fall then both of them fall another 100m when the belay ripped, it sounds like luck alone that they didn't die then and there. You can only be lucky for so long if you keep pushing it that close to the limit.

It's hard to tell how steep the route is in the video, or how far he actually is above his belayer (far enough to be seriously injured is almost certainly the answer though) but I was struck a little that he didn't opt to downclimb to the gear - that suggests it was a was a pretty hard and sketchy but of climbing.

And then there is the fact that you can see water running down the ice and dripping off it... again, I have very little knowledge here but that just intuitively seems like a serious warning sign on such a thin, poorly protected route. 

Which perhaps makes this video a bit of a weird thing to show on UKC.

I was gutted when I found out. It's clear that they were two exceptional climbers who were fully aware of the risks involved but chose to go for it nonetheless. Not everyone would attempt such an ascent, and far fewer would go back for another shot after the events of their first try. Scott's climbing partner for the Ogre was Kyle Dempster, who was a 2 time Piolet D'Or winner. His attitudes towards risk and adventure were portrayed in The Road from Karakol, one of my favourite mountain films youtube.com/watch?v=DhFx17s4a2E&

The most realistic and gripping film of ice-climbing I've ever seen. You feel the stress associated with each placement, and the constant "shall I/shalln't I?" questioning. And the final retreat off questionable gear rings completely true. One comment though, I feel he would have done better to just clip one rope into the tool to lower off. That way he'd have retained some protection from the piece below, and slightly softened the loading on the tool he was lowering from. Perhaps North Americans are less familiar with British-style twin rope technique.

That's what I was thinking - it would have made the lower off a lot safer, especially as he got closer to the good cam???

Other than that, amazing composed climbing up thin ice with just one bit of gear

Thanks for posting that - what an exceptional little film.  Mindblowing.  If anyone hasn't yet watched it, then treat yourself to some of the most adventurous journeying I've ever seen.

 In what way? What do you think the line should be?

I would have rather hoped that UKC would have at least aknowledged his death in the article and not just post a video of him climbing something sketchy where he could have very easily have died.  Better perhaps, would have been if UKC had expanded on the article and gave a little bit of history of the climber and his accomplishments, etc.
My best guess is that UKC weren't aware of his death and posted the video as Friday night clickbait entertainment.

So not only is it impossible to discuss a death when it happens we must now not even bring up the achievements of someone who has died?

I thought he showed how calm he was and in a way how controlled, as he did not come across as being unnerved by the situation. After all he lowered of straight from an axe, when a cameraman presumably on an abb rope was only a few feet away. and could presumably have instigated some form of rescue if necessary.

This is a great example of how not to retreat from a poor placement. If he had abseiled from the axe on one of his ropes, he would have loaded it with just half the force he did by getting lowered. The other rope should have been kept as a back-up belay. 

Obviously, same applies to retreating off sketchy gear on a rock climb.

I'n not sure I'd be keen to hang on that tool while pulling half a rope through, and this only as fast as the belayer can pay it out.

A better plan may have been to put the one rope he was being lowered on through his own belay/abseil device and lower himself. Functionally pretty much identical to being lowered by his belayer, but with half the load on the dodgy piece and very little extra time or faff.

Did you read my comment that I posted at 2052 last night?
To summarise, I'm surprised that UKC didn't at the very least acknowledge that the climber had subsequently been killed in a mountaineering accident and could have added a bit of a description of his achievements, etc. 
A few extra minutes would have been needed by the writer of the article which is surely not much to ask from a climbing website.
As I also said, I'm guessing that UKC didn't know that he had been killed and therefore why they posted it in the way they did.

Discussed at length back in September too https://www.ukclimbing.com/forums/winter_climbing/most_intense_ice_lead_and...

Classic example of why ice hooks (Bulldogs) are great. Why wouldn't he carry one - light and ideal for thin ice pro / abseils?

They are great in turf. They are terrifying in ice.

Have you actually done what you are suggesting? On vertical or near vertical ice, "hammered" a spectre or bulldog into a cm or so of ice and then lowered off it? I could think of many words for that but "idea" is not one of them. 

It's certainly a nice idea. But I don't think it's a particularly realistic ask of a small organisation like UKC. They don't have an exhaustive database of climbing knowledge in their heads and the Friday Night Video format isn't supposed to be a researched article, it's literally just a quick hit video recommendation. They sometimes do in-depth researched journalism, but if you want everything they post to be that, you won't get more research, you'll just get less posts.

They could have Googled it and I'm surprised that it isn't standard practice for basic research to be carried out on any article/video prior to it being released.

If you clip into the tool, you free up both hands and only have x1 bodyweight on the tool (actually less coz you can still keep your crampons in the ice). Then, you untie the rope that has the poorest protection on it, tie it to the bottom of the tool and ab off. After about 5m the other rope would  have him on a top-rope backup. As soon as you clip the rope into the tool and get the belayer to take you, you are loading it by almost x2.

Actually, self-lowering functions more like abseiling than being lowered by the belayer. The force exerted on the anchor is x1 (split 50/50 between each rope)

... which was the whole point of the suggestion! 🙂 No need to untie from anything either!

Ah yes, apologises, I misread your post!

Bowline or figure of eight...just maybe easier in the situation just to get on with it.He looked reasonable comfortable with what he was doing.

It's not a question of comfort.

Getting lowered almost doubles the load on the anchor as compared to abseiling because the belayer has to exert a force to counter your bodyweight.

The tool placement was bomber and he lowered off successfully and took a fair bit of faff to retrieve, he probably had a better view of all the variables from where he was rather than your armchair!

Not sure why your tone is so dismissive.  It's not that difficult to place a bulldog even when it's steep (start it in a pick hole), and as a get-out-of-jail card it's well worth having on thin ice pitches.  I always do, and have used one to retreat in this way.  It's not ideal, but you (should) know what you're getting into before starting up a pitch like that.

The placement he had was pretty bomber too, half his pick was buried, hardly "a cm or so" at that point.

I think this is directed at me.

It's just simply about physics. My abseil method loads the anchor by x1 and provides an ever improving backup belay on the other rope. His method loads the anchor by x2 and with every metre he descends the backup protection becomes less and less effective until it is useless.

How in the world can his system be better?!

I'm guessing this climber didn't understand the physics of the manoeuvre rather than 'had a better view of the variables'. And I'm also guessing a lot of posters on this thread are in the same boat.

That's the camera angle, you can't see how much is in, because it's a candle of ice sticking out between the camera and the pick placement, obscuring the lower half of pick. If it was half a pick in good ice I doubt you'd be able to flick the rope enough to make the tool pop out. My view of Grivel blades never coming out might be prejudiced by having to ab down to hammer out with my tool one of my mates new Taa-k-oons after I managed to place it with one swing so firmly neither of us could get it out just by arm strength when holding on to the other tool! 😆

You can see, and hear, that the tool is well set and solid.  However scary it looks, for a constant downward pull I'd say there was probably a decent margin above his lowering weight in that placement. 

If it starts waggling around all bets are off, which is probably why he opted for the smoothest and least faff option of lowering with both ropes rather than the armchair physicists approach.

It was also slabby. The faff of setting up the abb would be crazy.just as much risk of something going wrong..if not more so.

Smoothest! Do you really think being lowered by someone who is off to one side and a good 15/20m below you is smoother than controlling your own descent?

I actually think he sub-consciously realises the folly of being lowered because for the first part he holds onto the rope, effectively turning the manoeuvre into a self-lower. Eventually, however, he has to let go and has 2x bodyweight on that placement with zero backup.

As for the faff factor, as soon as you've clipped into the axe and freed up both hands the faff goes down by 90%. I mean you're going to ab off it, so you really shouldn't be concerned about sitting on it.

That placement looks solid for moving up on, but as an anchor, really?! He certainly thinks it's super sketchy so why use a technique that doubles the load?

I find bizarre these attempts to justify what he has done and undermine a more reasoned approach. I'm guessing this thread will be read mainly by ice-climbers gearing up for the coming season. It would benefit from being as educational as possible. You are unlikely to end up in a situation like this (personally never lowered off an axe in 30+ years of ice climbing), however you may get pumped and want to rest hanging from your axe. DO NOT CLIP IN AND GET YOUR BELAYER TO TAKE YOUR WEIGHT! Clip yourself directly into the axe. This can be facilitated by having an adjustable leash, otherwise make sure you can tie a clove hitch with one hand.

You are obsessing over one variable and you have no knowledge of the others in play here. He knows how solid that placement is. He's been stood on his points for 15 minutes on a vertical wall and he decided that trying to set up an abseil from that position isn't going to be feasible so opts to lower.

A very accomplished climber too: 
https://publications.americanalpineclub.org/articles/13201214268/Scott-Adam...

You wouldn't believe the number of accomplished climbers who have very little knowledge about some very elementary concepts, including the fact that being held by your belayer loads the anchor by a factor of 2.

Back in the 90s, DMM actually produced a technical ice axe with a notch in the head for putting the rope into so you could get held by your belayer. I seem to remember it was Stevie Haston's idea. Anyway this feature was copied by no-one and has been discontinued for obvious reasons!

Aid climbers tend to be the ones who are most savvy about it, which is understandable given that marginal gear placements are the main focus of their activity. This is why they always clip directly into the next placement with a daisy-chain or adjustable leash.

In Europe, the 'pulley effect' is common knowledge amongst climbers. Perhaps the more centralised system of grassroots training via local Alpine Clubs plays a part. In the UK, knowledge seems to be spread more informally and a lot of clarity is lost along the way. Maybe the BMC, media and equipment manufacturers need to be more invested in educating climbers.

How does it compare to the number of accomplished physicists who have very little knowledge of high standard ice climbing? I mean, I get your point and it’s not wrong, but as other posters have said, there will have been multiple factors in play. 

Nobody has yet said what what these mystery unseen factors could be.

Nothing warrants clipping both ropes into the iceaxe. By doing this he basically makes his runner placements redundant as backup.

Clipping one rope in and getting lowered could be justified if the anchor was bomber, but it's quite evident from what he's saying that this is not the case.

Was there an imminent danger and he decided that speed was the priority? I see no sign of this in the video, and anyway given the tenuous way he is descending, I'm not sure that clipping in and setting up an abseil on one rope would have been any slower.

But I am interested in hearing ideas about what other variables/parametres/factors people think might be influencing his decision-making...

For one, lowering off with a good long length of dynamic rope out is probably going to result in lower peak forces on the tool than abbing off it, even being *really* careful with your descent. 

Secondly, it is much simpler, with less opportunity to screw up while in a precarious position.

Yes well done you get your armchair physics points for explaining the pulley effect, but he wasn't giving a physics lecture, he was trying to get down safely off a sketchy ice route. Many other aspects of the practical and psychological context comes into play. 

Can you explain why? 

Best way not to screw up is to clip in, sit down, take a long, slow breath, and listen to the birds sing for a few seconds! Stress is your worst enemy in situations like this. And hey, suddenly you have both hands free to do the ropework!

I'm really looking forward to hearing your physics explanation for your first point! And how it makes getting down safer.

Do you not recognise the risk in setting up the abb . How do you factor that risk in? You are not possibly not looking at the " whole " situation, never mind the physics.That is what posters are saying to you.

No please explain

I don't think I would describe him as particularly stressed in any part of the video. He handles an insanely stressful situation in a calm and measured way.

Yep, he's a cool customer for sure!

Surely this is pretty obvious...... with 15-20m of rope out to the belayer any movement by the climber or belayer, or any variation in the speed of paying out is safely absorbed by the rope stretch. Abbing off it you start with next to zero dynamic rope between you and the anchor and are highly likely to exert higher peak loads on the tool with even with the gentlest paying out.

Secondly, he doesn't just lower off into space fully weighting the anchor, he keeps his points and other tool in the ice as he descends so never applies the theoretical doubled load you are obsessing over. 

Why didn't the camerman just lower him the fixed line?

No doubt your physics is sound, but you refuse to account for Scott's experience and judgement (proved to be correct) that the placement was good enough for his lowering weight.  I imagine his rational mind knew this well but the appearance of it still causes some stress, hence the 'looks sketchy' commentary.

If the axe didn't rip when he bounce tested it, then as long as the lower is smooth and the load is constant, it's not going to rip half way down.

There's theoretical best practices and then there's the real world where 'good enough' works and simplicity is a risk reduction measure in itself. 

I think it is also important to remember that he made it out and realistically did everything right. We can talk about ways it could have been done better, but until you are in the situation you don't know how you will respond.

To very quickly make a decision on the correct course of action and act on that is often the hardest thing to do in situations like this. Yes he could have stopped and thought for a while, or spent a while setting up a proper ab anchor, but he made a decision and followed through, no panic.

Yes, in retrospect it is useful to analyse, but he made no mistakes.

He has clipped in and lower off. That is a lot simplistic to do than clip in, thread a  rope through, transfer onto the abb and so on. That invites mistakes as others have mentioned. 
 So the balance of risk suggests that whilst what you are saying maybe right , there are risks of something going wrong with what you are suggesting. So look  at it holistically, not through one issue.  

For the benefit of the thread, can you elaborate on your own experience of ice climbing and of performing in stressful situations?

I think you're saying that if the belayer lets the climber down quickly and then stops almost instantly the rope will absorb some of the impact. Why would she do this? One of the basic tenets of climbing is that you must trust your belayer not to do something insanely stupid. Personally I'd rather abseil than be lowered by someone who I think might fck around with the speed of descent.

How does this work? You are saying that the approx 80daN of force the abseiler exerts on the anchor will somehow increase because there is no elasticity in the system. If you hang off an anchor on a bungee cord or a wire cable you're still loading it with just your bodyweight. If anything the bouncing around might create higher loads. The dynamic properties of climbing ropes only reduce impact forces and you don't get these while abseiling.

Silly me. But seriously how would you feel abseiling off that ice-axe with your mate on your back!!

Not sure how this will facilitate the understanding of my words, but... trust me bro, I was pretty handy back in the day!

I don't mean it in a critical way or in any way other than to give context to your words, because you're a new user with a non-existent profile. From my perspective, it feels like you're not giving weight to any of the "climbing factors" involved. There's a world of difference between textbook and in-the-moment, sometimes, and there's a world of difference between post-even analysis with a cup of tea, and actually doing something under stress.

Frankly, for a climber of Scott Adamson's ability and mental fortitude, tying a rope to an ice-axe, attaching a belay plate and abseiling off is pretty much unfck-uppable

But I don't think I've had harsh words for, or been judgemental about, Scott Adamson. I'm just pointing out to people how he could have done it in a much safer way so they are better equipped for a similar situation. Frankly, I think quite a few people on here could benefit from my explanations.

Ok buddy, you are definitely the smartest person on UKC, enjoy.

So there's a bit of a misconception here. The logic that has been stated is that the climber is attaching themself to a perfect pulley on the anchor with climber's weight on one end of the rope, and belayer's weight on the other end of the rope, meaning that the anchor (in this case the ice axe) is holding effectively double the climber's weight. However, this approach neglects the friction of the rope running over the carabiner, which can be accounted with a "pulley efficiency" term. For a rounded carabiner, pulley efficiency is about 50% and for an I-beam carabiner it's about 43% (test results here https://www.alpinesavvy.com/blog/pulley-vs-carabiner-whats-the-difference if anyone has extended test results for a wider range of forces please let me know). So replacing the "perfect pulley" with an I-beam carabiner, and considering a climber mass of 70kg, there is a force equivalent to the weight of a 0.43*70=30kg mass on the belayer's side of the rope, making for a total weight on the anchor of 100kg for a 70kg climber. Anyone who has seen/been a climber lowered off by a belayer who is considerably lighter can attest to the friction in the system preventing the belayer from flying up in the air.

Another comment is on the angles involved. Ice axes are directional, and the further out from the wall the direction of pull, the more marginal the placement becomes. Scott was very careful with the ropes to make sure that the pull on the axe was downwards. If you clip your harness to the ice axe while it is within reach, the angles are such that you are always going to be pulling the tool handle away from the ice, making the placement worse. Now if you can bury the tool in thick ice this may not be a problem, but if the ice is thin then it may become a factor. There is also the question of committing completely to one point of attachment. The suggested approach of clipping the tool means you are completely committed, and if that tool pops you're in very big trouble. Here, Scott left himself a back-up option until pretty much the last possible moment.

My opinion is that this was a situation which is far removed from the concept of "best practice". The climber improvised, got out of a very complex and dangerous situation, and even retrieved all his gear. It's hard to deny that the decisions led to a good outcome, and all available options were risky. Lots of people watching would have done differently, but most of us wouldn't have even started up that pitch in the first place.

We both all know all the elite and other climbers who have been killed in abbing incidents.Just fumbling to retie your knot with gloves on  and potentially getting that wrong is a risk( Lynn Hill of all people got that wrong once as you not doubt know).

Another point to this, by lowering he was able to keep 3 points of contact on the ice while setting up his lower. An abseil would have required him to at a minimum take both hands off of the ice tools and clip in, something which would scare me far more than a lower where I had contact at all times.

More interesting than the video are the responses in the thread, the expert halo is strong! I find it fascinating that, because the climber is an expert and he survived, a lot of the posters assume that his decision making is perfect and cannot be criticized.

There has been a lot of research and discussion about heuristic traps in avalanche safety circles and a significant proportion can be applied to climbing. A lot of people make bad decisions in avalanche terrain and don't die, if you ski regularly in a big ski resort you will see it nearly every time you are on skis, especially after snowfall. This can lead those people to think they have made good decisions and start to believe they are good at judging and managing avalanche conditions. In reality, they have just been lucky.

The fact that this solution worked, does not mean it was the best solution. Discussion and analysis after any incident, whether it was a good or bad outcome, is healthy.

I was surprised by these figures because they are by far the lowest I've ever seen on the subject.

So, I did a little test today using a bag of cement, a rope-tarp, a length of double rope, a carabiner and a digital spring balance.

I put the cement in the rope-tarp and weighed it. Then I attached the rope, put it through a high carabiner, placed the balance on the free end and weighed again. I repeated both measurements multiple times. The worst pulley efficiency rating I got was 80%. This time I was surprised at how little friction there was in the system.

I have no doubt that results will vary immensely depending upon the thickness/condition of the rope and the profile of the carabiner, but I really don't think your calculations should be used to justify the idea that it's fine to lower off marginal gear.

NB. I was going to write a paragraph for all those that said Scott Adamson must have made the right decision because he survived the event, but Galpinos nailed it in his post.

Thing is, these climbers made their mistakes through complacency, not stress. Lynn Hill was at the foot of a sports crag when she forget to finish her knot. Scott was not in a position to be complacent.

Speaking for myself I don't assume his decision making was perfect, but the dogmatic insistence that he messed up by lowering rather than abseiling is frankly unhelpful and an unnecessarily black and white view of it.  The fact is he solved a tricky problem by considering the situation calmly and choosing an option that worked out.  There were other options that would also have probably worked, abseiling being one of them.  Empathising with the choice he made is not the same as refusing to countenance criticism of it. 

For your own sanity, I think you might want to let it go (metaphorically)...

Insanity according to Dave=doing your own test rather than blindly accepting/dismissing someone else's data. It's a funny, old world!

Nice! Kudos for gathering some data- I'm a big fan of testing assumptions. Also, if you have any pointers to other datasets let me know.

I'd also be keen to run a few experiments on this, but don't currently have the equipment. I've got a few questions. How heavy was the bag of cement? From what I've seen, people typically assume a constant pulley efficiency regardless of weight, but I am curious as to whether the response is weight dependent (e.g. rope deformation over the surface of the metal changing the coefficient of friction). Also, it sounds like your measurements were made statically. Is this correct? Or did you release tension in the rope until the cement bag started to move?

With a dynamic measurement (rope moving over the carabiner) the kinetic friction is approximately constant. However, with a static measurement the static friction is approximately proportional to the applied force until the threshold of motion is reached (it's probably easier to look at a graph of it than to try to make sense of my description). This means that whenever the climber is not moving, there can be a significant range of tensions in the belayer's end of the rope while the tension on the climber's side of the rope stays the same. This is because the tension in the belayer's rope is the tension in the climber's rope minus (or plus, if trying to haul the climber up) the variable static friction. However, while lowering the climber at constant velocity the tension in the belayer's rope is the tension in the climber's rope minus the (constant) kinetic friction.

I think one important difference between skiers and this situation is the rarity of such an event. How many times do you think Scott did this? How many times do you think this has been done by anyone, ever? And by this, I mean retreating off a single axe in thin ice because of an upcoming section of detached ice with sod all gear and a likely death fall. I know people who have backed of ice axes, but never like this.

I agree that it's important to examine case studies and have a healthy discussion and analysis of the points that will be relevant to future situations that we might encounter, but I think that some (not all) of the comments in this thread apply to scenarios which are more common and less tenuous than the one shown here. I think it's important to recognise, holy sh*t, this guy was out on a limb here in a way that the vast majority of us never will be. I'm reminded of the folk who took delight in telling Greg Boswell about the textbook way to fight off a bear.

I googled and found a link that says what you are saying: https://www.alpinesavvy.com/blog/anchor-forces-from-lowering

To be honest I'm really puzzled and frankly skeptical about this. The climber has the potential energy= mgh (eg 70kg x 9.8N/kg x 20m = 13720Nm aka 13720J

When the climber is lowered or abseils that potential energy all has to be dissipated via friction as heat such that when back on the ground the climber no longer has any of that potential energy.

In a frictionless system, the climber lowering off would sink to the ground whilst the belayer would be hoisted up to the anchor. The force on the anchor would only be 70kg x 9.8N/kg and both the lowering off climber and the belayer would be effectively weightless whilst they exchanged places. The potential energy of the system at the end would be exactly the same as at the beginning.

A "frictionless abseil" amounts to falling through a vacuum. The climber would accelerate at 9.8m/s/s and then their potential energy would dissipate over whatever distance they mushed down once they hit the deck.

Basically it is all about the friction through the abseil/belay device and making sure that the lowering off/abseiling happens very smoothly such that the potential energy gets dissipated evenly over as long a distance as possible (energy=force x distance)

I'm basing all of this from remembering school lessons from many decades ago. It would be great if someone more clued up than me could weigh in!

If he'd had one of those bolt guns like off Cliffhanger he could have nailed himself to the wall and then waited for a helicopter

Presumably whoever was filming had a good anchor. Couldn't the camera person have rescued him?

It seems a bit sick to me to commercialise someone lowering off a dodgy anchor as a spectator sport.

And yet we all watched it. 
Besides, I doubt it was conceived as a 'will he/won't he plummet' film, and surely wouldn't have been uploaded if it had ended badly. Presumably it's simply intended as slightly nerve-wracking but ultimately affirmative championing of coolness under pressure.

I actually stopped watching it first time around but then the discussion about lowering off vs abseiling compelled me to watch the last few minutes. I haven't watched the whole thing but I guess nerdery regarding the physics overrode my initial principled stance!

I still haven't seen the middle part of the video.

I'll plead that debunking/clarifying that meme claiming lowering off doubles the force on the anchor is potentially consequential if it influences what others may do in such a situation in future.

When the video came out either on here or social media (sorry I'm too lazy to search it out) it was explained the camera man was actually way off to the side and was well out of reach.

Apologies for my muddle over that whole lowering off versus abseiling thing. I think I was totally wrong. I wrote before:

I don't know what I was thinking. I think you are correct and the force on the anchor would be 2 x 70kg x 9.8N/kg.

Of course when both people were dangling, it is especially obvious the force is that of both their weights.

I was thinking he could have also done with putting a prussic on the rising side of the rope to minimise the fall to the next gear if the axe were to fail.

Correct- but only if there is no friction at th carabiner.

Also correct- but only if dangling. In the case of lowering, the belayer is not typically dangling. The force on the anchor is the tension on the belayer's rope plus the tension on the climber's rope. The tension in the climber's rope is the climber's weight. The tension in the belayer's rope is the tension in the climber's rope minus the friction at the anchor. For carabiners, the common rule of thumb is that 50% if the tension is tranferred from the climber's side to the belayer's side, with the other 50% going to friction. This is question 3 in the link you sent. oureed2 on this thread performed a test where they reckon the carabiner transferred 80% of the tension and 20% was lost as friction, which seems to be a different result to the other results I've found.

In short, the force on the anchor is approx. the weight if the climber if the climber abseils orbself lowers. If the climber is lowered by the belayer, the force on the anchor is (according to results quoted in this thread) between 1.43 and 1.8 times the weight of the climber, where the bulk if testing has come out at the lower end (around 1.5).

Being 70 I'm long past my climbing days but am I old fashioned or don't ice climbers secure tools to wrists or has that changed due to...??

My terra's that I sold in my shop in North Wales (does that show my age) were always secured to my wrists. It's very thin this ice but cams look like they would be appropriate along this potential route. 

Reading some of the comments am I correct to say this lad is no longer with us? Please excuse my ignorance.

Leashless climbing started on the competition circuit around the turn of the millennia. It came in to ever wider use through the 2000s. I would say the vast majority of winter climbers now climb leashless (no wrist loops). I think all modern climbing tools are designed to be used without leashes.

I always thought I was the last ice climber to stop using wrist loops, but even I can't remember the last time I used them - maybe about 8 years ago?

25kg bag of cement and static measurements only. 

I did look to see if the guage changed as I lowered the bag, but couldn't see anything conclusive.

Interesting discussion.  The guy describing some physics gets dinged for possibly denting the halo of the expert.  His mistake was linguistic---saying that the video was a good example of what not to do triggered a whole lot of folks. 

I think he provided information worth considering by others if they get in an analogous situation, but that value got lost in the criticisms. Imagine if he had said, "Fantastic retreat by Adamson under incredibly trying circumstances!  Folks finding themselves in analogous situations might want to consider whether abbing off the fixed piece might sometimes be a better strategy."  His points would all have been the same, but would all the downvotes still have accumulated?

As to those points. 

1. Carabiner efficiency has been tested over and over.  Of course, there is a distribution of results and probably a pretty big standard deviation, considering the vast variation in testing protocols.  But the predominant evidence seems to be somewhere around 50-66% efficiency.  So no, the load on the top piece won't be doubled in general, but it is going to be 50-66% higher than with the ab approach.  It seems to me that this is hardly grounds to dismiss the point that on marginal gear we'd hope for the lowest load we can get, most especially since no one, no matter how expert, can judge the solidity of a marginal placement with the accuracy needed to rule out the need for a lower possible load. In other words, the validity of oureed2's remarks is unchanged in the light of the friction reduction in total load.

2. The idea that having a lot of rope in the system will reduce the load to the top piece when holding or lowering is false as far as I can tell, and the proposer hasn't offered any reason to believe it.

3. There is a bit of a hitch in the abbing proposal.  As everyone knows, ropes stretch, even when you just apply your weight without actually falling.  When this happens, there is a peak tension in the rope equal to double body weight.  This peak tension is transitory; the rope bounces back and the tension declines to the weight of the load, but still there is going to be a moment when the anchor gets double body weight, even in the abbing scenario.  Moreover, any little bounce during the rappel may again bring the rope tension up above body weight, so the chance of higher loads to the anchor remains a danger.  On the other hand, in the lowering scenario, little drops are also possible and probably more likely, and the anchor is continually, over time, loaded to 50--66% body weight, and this might well prove to be a worse situation than just an instantaneous peak load, making abbing probably still preferable even if not as advantageous as advertised.

4. I think untying one of the ropes to ab makes little sense, considering you can get the same effect by self-lowering.  And what if the anchored piece turns out to be unexpectedly decent? Then you've lost the rope tied to it.  No, pop a carabiner on the harness, throw on a Munter hitch (easy to do one-handed), and down you go. But definitely use just one of the pairs of ropes!  In the situation in the video, it looks to me that by the time he decided to retreat, Adamson was far enough above his pro to hit the ledge.  If the belayer could have taken in one strand as the leader descended, the pro could come back into play. Any way you look at it, lowering with both strands was a mistake which, like many we make, did not involve any consequences.

5. And speaking of the pro, there is one thing not mentioned (I think) that surprised me, and that is that the leader only placed a single cam in a crack that would easily have taken two.  Doubling up on mission-critical pieces when possible is pretty sensible, but most especially in a situation involving cams in wet sandstone, which can be far more subject to failure than cams in, say, dry granite.

Very well said.

So many of the tedious tiffs on here could be avoided by people learning that kind of lesson.

Edit: But of course I'm assuming that people, having made an assertion that gets questioned, would prefer not to spend hours, days or even weeks 'proving' that they were right all along.

An excellent summary, makes a fantastic TL;DR for the thread!

Some questions/comments on your points.

3. You say that the peak tension in the rope is double the weight. This is news to me, and I'm sure to many others reading. Is this based on theory or experiment? Could you please offer some clarification, or point us to a source of information on the topic?

4. One minor comment: self lowering uses more rope than abseiling. If you're 40m up on a 60m rope, this option won't be available to you.

This is straight elastic theory.  This isn't a good place to display math, but it is pretty simple in this case.  I'm assuming the rope behaves as a classical undamped spring, which means (Hooke's Law) that the tension in the rope is proportional to the relative stretch, T = k(s/L) where s is the actual amount of stretch and L is the amount of rope involved.  It follows that the work done in stretching the rope by an amount s, the integral of T ds, is k/(2L) s^2.  The peak tension in the rope occurs when at maximum stretch---let this now be s. the climber weighting the rope loses ms in potential energy (m being the mass of the climber).  The loss in potential energy is absorbed in work done stretching the rope, so k/(2L) s^2=ms.  Eliminating the solution s=0, the equation becomes (k/L)s = 2m, and the left side is the tension in the rope at the instant of maximum elongation.  The rope springs back after maximum elongation, at which point the tension in the rope becomes equal to m.

If you use the standard equation for maximum rope tension for a fall with fall-factor F, and put F=0 in that equation, you'll get the same peak tension value of 2m.

You can get a tactile sense of this effect with a rubber band and (relatively heavy) weight.

Of course the rope doesn't behave exactly like an undamped spring.  If it did, the climber would be bouncing up and down forever. A better model, but one harder to calculate with, is to admit some damping effect (coming from internal friction between fibers and between sheath and fibers) and account for work done against the damping, which would lower the peak rope tension.  But the undamped calculation is a good approximation, especially when variations in how the rope is weighted in practice are involved, since in some cases there might be a tiny free fall involved.

On the other hand, using tools in ice and/or holds on rock, the climber might be able to slowly lower themselves into the position of maximum elongation.  Using their limbs to take some of the load would lower their effective mass as far as the rope is concerned and might quite possibly keep the maximum tension at body weight.  The trick would be to not grab the rope in order to get into position, and this isn't exactly the most natural instinct.

Yes, but lowering by the belayer doesn't work either, so in that case you'll have to rappel, it won't be a strategy choice.

Nice, thanks for that and for explaining the calculation method- I followed along and it's a neat way of thinking about it. In an attempt to drag this thread wildly off topic, I had a quick go at throwing in a damping term, and assumed that the system is critically damped to make the calculations easier and to see what that would mean (this doesn't seem too unrealistic to me. On a few longer falls I've definitely bounced on rope stretch, but usually I've felt like I've stopped at the bottom of the rope stretch, and stayed there). To do this I took the general equation of motion (x(t)) for a damped simple harmonic oscillator, differentiated it wrt time twice to get the acceleration, then subbed in the critical damping condition to simplify the expression. If tension is T, then I get that the force acting on the climber as a function of time t is of the form (T-mg)=ma=-A k exp(-sqrt(k/m) t) where A is the initial amplitude (if you like, the climber's starting location before weighting the rope), k is the spring constant. Plugging in some numbers gives a peak tension magnitude equal to mg (which intuitively makes sense, given the assumptions. In this case the climber never accelerates to the extent of bouncing, so it makes sense for peak tension to equal mg). While I reckon it's highly likely I've made a few errors in the calculations, I also think that the damping coefficient is very important in determining the peak force and should not be neglected.

A long shot, but does anyone on this thread design or test ropes? If so, what sort of damping characteristics are typical?

You explain why this is the case in your next paragraph. Note I mentioned peak force, not load. Any little bounce on the system will have a quite different effect on the anchor when it's being directed through 20m of dynamic rope (as when being lowered), versus virtually zero dynamic rope when beginning the ab. Not to mention, while setting up the ab he's presumably going to be attached to the anchor by a sling/draw which will make it extremely easy to exert high forces on the anchor without being extremely careful about maneuvering.

Nomics would be a voyage.  Tech machines okey dokey.