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Antarctica loses three trillion tonnes of ice in 25 years

bbc.co.uk

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Re: Antarctica loses three trillion tonnes of ice in 25 years

#51

Post by mkempe »

southern_cross wrote: post #50
mkempe wrote: post #49

Earlier quoted context omitted.

Hmm. Let me know when you have some scientific evidence and specific numbers related to these notions. If we're cooking up stories, how about this arbitrary "explanation": Phytoplankton are plentiful. They're reproducing and dying and sinking in such vast quantities to the ocean floor that this floor is steadily growing a new layer, at a rate of a few mm per year. Hence the apparent sea-level rise, relative to the co…

Am I correct in assuming that you're the type who needs a "study" in order to tell you what to think? Or are you the type who can use their own eyes and their own brain and do their own thinking and come up with their own conclusions - maybe ones that are eventually validated by studies after all, but perhaps only years or even decades down the road? I consider the first type a form of education-induced brain damage,…

The latter, of course! I'd be interested in your numbers. H2O is 2.5% of the atmosphere, so I can't see our CO2:H2O production having a significant impact in that respect; but still, an interesting angle since H2O is a major greenhouse gas.

Estimates for biogenic sediment accumulation ranges up to 5 cm per thousand years -- two orders of magnitude smaller than current prediction of the rate of global sea-level rise.

Re: Antarctica loses three trillion tonnes of ice in 25 years

#52

Post by southern_cross »

mkempe wrote: post #51
southern_cross wrote: post #50

Earlier quoted context omitted.

Am I correct in assuming that you're the type who needs a "study" in order to tell you what to think? Or are you the type who can use their own eyes and their own brain and do their own thinking and come up with their own conclusions - maybe ones that are eventually validated by studies after all, but perhaps only years or even decades down the road? I consider the first type a form of education-induced brain damage,…

The latter, of course! I'd be interested in your numbers. H2O is 2.5% of the atmosphere, so I can't see our CO2:H2O production having a significant impact in that respect; but still, an interesting angle since H2O is a major greenhouse gas. Estimates for biogenic sediment accumulation ranges up to 5 cm per thousand years -- two orders of magnitude smaller than current prediction of the rate of global sea-level rise.

Unfortunately I did this seat-of-the-pants calculation years ago, so I no longer have the numbers around. I do remember that using the simplistic 1:1 ratio the net result was considerably smaller than I had originally expected, although still measurable. But when I tried to figure out a more realistic ratio to use I kind of ran into a brick wall. See, for example, the typical molecular complexity of coal: https://en.wikipedia.org/wiki/Coal#/media/File:Struktura_che... (It's been a long time now, but if I remember my organic chemistry correctly each of those unmarked corners is a carbon atom, and each of those may have a hydrogen atom attached to it, and possibly more than one.)

A transition away from coal and towards natural gas (which consists primarily of fully-combustible methane at a ratio of 1:2) should lead to both an increase in H2O output and a decrease in CO2 output as compared to coal. (A recent local power plant transition from coal to natural gas claims a carbon emissions reduction of 60%.) Using your 2.5% number, water vapor is already about 60x more common in the atmosphere than CO2 is at 0.041%, and I've seen estimates that it is probably about 15% higher now than it was in the past. (Presumably any H2O output above that has ended up in the oceans.)

Given that as a greenhouse gas water vapor is at least 2x (IIRC) as powerful as CO2 and apparently also increasing at a steady clip, you'd think that folks would be paying more attention to this, but instead they just tend to ignore it. In fact they just like to ignore water vapor completely, except maybe when it leads to clouds and such.

Re: Antarctica loses three trillion tonnes of ice in 25 years

#53

Post by Retra »

mkempe wrote: post #25
Retra wrote: post #18

Earlier quoted context omitted.

That's also average sea level. If hurricanes get more powerful or more frequent, then you're going to want to account for the storm surge as well.

The historical record shows that hurricanes have gotten neither more frequent nor more powerful. [1] [1] https://www.wsj.com/articles/the-hurricane-lull-couldnt-last...

Perhaps the word "if" doesn't mean what I used it to mean? In that case, you should correct my misconceptions on that subject instead.

Re: Antarctica loses three trillion tonnes of ice in 25 years

#54

Post by mkempe »

Retra wrote: post #53
mkempe wrote: post #25

Earlier quoted context omitted.

The historical record shows that hurricanes have gotten neither more frequent nor more powerful. [1] [1] https://www.wsj.com/articles/the-hurricane-lull-couldnt-last...

Perhaps the word "if" doesn't mean what I used it to mean? In that case, you should correct my misconceptions on that subject instead.

The X in your "if X then ..." is demonstrated false. That's your misconception.

Re: Antarctica loses three trillion tonnes of ice in 25 years

#55

Post by rkul »

mkempe wrote: post #28

For context: there are 26.5 million cubic km of ice in Antarctica, weighing 24.3 million Gt (26.5 / 1.091). Assuming these estimated 2,700 Gt (the rounded 3 trillion) have not been steadily replaced by new water on top of the ice sheet [1] the reported loss amounts to a mere 0.01% of the total ice sheet. I don't see cause for panic. [1] https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-o...

How do you know 0.01% is not a cause for panic?

Re: Antarctica loses three trillion tonnes of ice in 25 years

#56

Post by mkempe »

rkul wrote: post #55
mkempe wrote: post #28

For context: there are 26.5 million cubic km of ice in Antarctica, weighing 24.3 million Gt (26.5 / 1.091). Assuming these estimated 2,700 Gt (the rounded 3 trillion) have not been steadily replaced by new water on top of the ice sheet [1] the reported loss amounts to a mere 0.01% of the total ice sheet. I don't see cause for panic. [1] https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-o...

How do you know 0.01% is not a cause for panic?

At that rate it would take 25,000 years for 10% of the Antarctica ice sheet to melt.

On the other hand 20,000 years ago was the peak of the last Ice Age. Sea level was 120m lower than today. There was more ice in the Northern hemisphere's ice sheets than there is in Antarctica. We happen to live in an interglacial, one that is not even as warm as the previous one. It is far more reasonable to fret over the coming return of the Ice Age than to panic about minor variations in a warm, agriculture-friendly climate.

Further, another NASA study indicated in 2015 that the Antarctica ice sheet is growing (not shrinking) by almost 0.01% every 25 years. Did you panic over that report? More generally, is there a specific, perfect, fixed amount of ice that should be in Antarctica? has there ever been? by what standard?

Re: Antarctica loses three trillion tonnes of ice in 25 years

#57

Post by lostmsu »

southern_cross wrote: post #45
gehwartzen wrote: post #41

Earlier quoted context omitted.

Beyond that I wish articles included the total volume of ice in Antarctica; not that I believe 3 trillion tones of lost ice is not a big deal but I have no idea if that represents 1% or 50% of the available total.

It looks like the total amount of estimated ice in Antarctica is something like 30,000,000 cubic kilometers, give or take. In comparison, the amount of ice being lost here probably doesn't even amount to rounding error; it's more like just noise. (Someone else here has calculated a value of about 0.01%, but I don't know how accurate that is.) That's a common theme with such reports these days, BTW. The numbers quoted…

A poor estimate is that 1 trillion tones of ice is 1000 cubic kilometers.
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