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Antarctica losing six times more ice mass annually now than 40 years ago

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Re: Antarctica losing six times more ice mass annually now than 40 years ago

#11

Post by credit_guy »

brylie wrote: post #10
credit_guy wrote: post #5

Earlier quoted context omitted.

Fine, it's GRACE. So GRACE has an accuracy of 0.001%? Really? Or rather, is there any estimation technique to measure the ice mass of a whole continent with accuracy of one thousandth of one percent? Wait, actually they claim their accuracy is much higher, sometimes more precise than 0.0002% or even 0.0001% (I kid you not). Here's the wiki link for GRACE [1]. It states that during 2003-2013 the ice loss was 67±44 Gt…

The 0.00001 accuracy argument you are making seems like a red herring. If I measure myself on a scale, do you discredit the measurement because the scale produces a value that is some fractional, fractional, fractional percent of the Earth's mass?

Why are you talking about Earth's mass? We are talking about Antarctica here. If I weight myself on a scale that has 0.2 pound precision (like the one I have), and then somehow I tell people I lost 0.002 pounds, some people will be quite skeptical of my claims. In the case of Antarctica, how is one supposed to quantify the accuracy of its net ice loss? By comparing it with the mass of an elephant of a blue whale [1] ?

[1] https://www.washingtonpost.com/news/energy-environment/wp/20...

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#12

Post by credit_guy »

mturmon wrote: post #9
credit_guy wrote: post #3

Earlier quoted context omitted.

"The team was able to discern that between 1979 and 1990, Antarctica shed an average of 40 gigatons of ice mass annually. (A gigaton is 1 billion tons.) From 2009 to 2017, about 252 gigatons per year were lost." I'm a climate skeptic. This type of research is why I'm a climate skeptic. 252 gigatons per year means a bit less than 0.001% of the mass of the ice sheet of the Antarctic continent. Or, to put it differently…

You know less than you think you do. GPS is not part of the measurement suite in OP, but better than 1.8 cm vertical resolution from GPS has been possible since the late 1990s, using after the fact orbit determination. It is now routine to get sub-cm vertical accuracy in GPS measurements [1, fig. 3, magenta line]. The horizontal displacements are known to about a mm. These displacements are known so accurately that y…

> You know less than you think you do.

Not clear how this ad-hominem enhances your argument.

>If you don’t know how they did the measurement, why are you so sure it is wrong?

I'm not "so sure", I'm just skeptical. I find it hard to believe that one can estimate the net ice loss over a huge and dynamic body of ice with an accuracy better than 0.001%, using any type of measurements conceivable.

You are saying that somehow the whole mass of Antarctica is irrelevant as a base mass to calculate accuracy? Why so? The ice naturally compresses and flows and this happens at continental scale. A large iceberg calving on the western coast of the continent may be offset by a relatively modest ice accumulation on the much larger eastern side. However, that accumulation on the eastern side will be conflated by the general compression that will lead to some ice being pushed towards the edges, etc, etc. There's no natural way to take a part of the continent out of the equation and say "well, we are interested only in this subset".

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#13

Post by credit_guy »

flukus wrote: post #7
credit_guy wrote: post #5

Earlier quoted context omitted.

Fine, it's GRACE. So GRACE has an accuracy of 0.001%? Really? Or rather, is there any estimation technique to measure the ice mass of a whole continent with accuracy of one thousandth of one percent? Wait, actually they claim their accuracy is much higher, sometimes more precise than 0.0002% or even 0.0001% (I kid you not). Here's the wiki link for GRACE [1]. It states that during 2003-2013 the ice loss was 67±44 Gt…

> Fine, it's GRACE. So GRACE has an accuracy of 0.001%? Really? Or rather, is there any estimation technique to measure the ice mass of a whole continent with accuracy of one thousandth of one percent? If some areas are losing/gaining meters then your 1.8cm average is irrelevant as it's not the resolution they're looking at. Your argument is misleading because it assumes uniform ice loss across the continent, it's a…

>Your argument is misleading because it assumes uniform ice loss across the continent

I'm not assuming that. "Average" and "uniform" are two different things. I never said anything about "uniform".

Take a look at the ice loss visualization [1] from NASA's website. On the west side there are ice losses as high as 300m (dark red), on the east side some ice gains of about 100m (light blue). All those losses and gains are estimated with some instruments. If you are in one of the areas where the ice loss was estimated to be about 100m, you look at your initial elevation, final elevation and take the difference. Will you elevation difference be -100m, or -98m? There will be some measurement uncertainty. Overall, uncertainties from different instruments tend to cancel out, that't the law of large numbers. Overall, I doubt we have that many numbers (or so little individual measurement uncertainty to begin with) to end up with a final measurement uncertainty that is so small.

Take a look at article [2] about the estimation of precipitations in Antarctica. It was published in March 2018 in the journal "Polar Science" owned by Elsevier, which as far as I can tell does not publish junk articles. The general tone is that there are large uncertainties in the estimation of precipitation in Antarctica.

"The study of Antarctic precipitation has attracted a lot of attention recently. The reliability of climate models in simulating Antarctic precipitation, however, is still debatable"

"The current method of data collection relies on measurement with limited temporal basis, with distances between measurements exceeding 1300 km (Knuth et al., 2010). This makes instrumental-based measurement of precipitation in Antarctic highly unreliable (Genthon et al., 2003)."

Of course, such an article does not get much press. How would one report it? "New research shows large uncertainties in our understanding of the mass balance in Antarctica" ?

[1] https://svs.gsfc.nasa.gov/30880

[2]https://www.sciencedirect.com/science/article/pii/S187396521...

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#14

Post by dTal »

credit_guy wrote: post #11
brylie wrote: post #10

Earlier quoted context omitted.

The 0.00001 accuracy argument you are making seems like a red herring. If I measure myself on a scale, do you discredit the measurement because the scale produces a value that is some fractional, fractional, fractional percent of the Earth's mass?

Why are you talking about Earth's mass? We are talking about Antarctica here. If I weight myself on a scale that has 0.2 pound precision (like the one I have), and then somehow I tell people I lost 0.002 pounds, some people will be quite skeptical of my claims. In the case of Antarctica, how is one supposed to quantify the accuracy of its net ice loss? By comparing it with the mass of an elephant of a blue whale [1]…

It's a red herring because the total quantity of ice in the Antarctic is irrelevant, both to how the loss rate is measured and the climate significance.

It's like looking at someone who's hair is falling out and saying "look, they're barely losing any weight at all!"

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#15

Post by wmeredith »

macinjosh wrote: post #2

I find headlines like this frustrating and potentially misleading. It provides zero context. Do we know that this is abnormal? Forty years is a short period of time in the grand scheme of things. Six times more than what?

Agreed. It’s poor journalism. My response is, “so?”.

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#16

Post by Proven »

> we expect multi-meter sea level rise from Antarctica in the coming centuries.”

1) Nonsense modeling. 20 year predictions from the 1990's turned out to be laughable, now they're predicting 200 years ahead. How about they try 2 year models, maybe they could get those right?

2) Can't see why I should care about someone's beach property in 2428. Even if their models were correct, which ch they aren't.

Most people live paycheck to paycheck and these lunatics want to tax and spend their hard earned money to prevent fantasy scenarios. Truly appalling.

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#17

Post by freethemullet »

wmeredith wrote: post #15
macinjosh wrote: post #2

I find headlines like this frustrating and potentially misleading. It provides zero context. Do we know that this is abnormal? Forty years is a short period of time in the grand scheme of things. Six times more than what?

Agreed. It’s poor journalism. My response is, “so?”.

Is your point that humans can always ask "so?" after a proposition?

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#18

Post by sjg007 »

macinjosh wrote: post #2

I find headlines like this frustrating and potentially misleading. It provides zero context. Do we know that this is abnormal? Forty years is a short period of time in the grand scheme of things. Six times more than what?

Yes. What causes ice to lose mass? Heat.

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#19

Post by davesque »

credit_guy wrote: post #12
mturmon wrote: post #9

Earlier quoted context omitted.

You know less than you think you do. GPS is not part of the measurement suite in OP, but better than 1.8 cm vertical resolution from GPS has been possible since the late 1990s, using after the fact orbit determination. It is now routine to get sub-cm vertical accuracy in GPS measurements [1, fig. 3, magenta line]. The horizontal displacements are known to about a mm. These displacements are known so accurately that y…

> You know less than you think you do. Not clear how this ad-hominem enhances your argument. >If you don’t know how they did the measurement, why are you so sure it is wrong? I'm not "so sure", I'm just skeptical. I find it hard to believe that one can estimate the net ice loss over a huge and dynamic body of ice with an accuracy better than 0.001%, using any type of measurements conceivable. You are saying that some…

It was actually a fact, not an ad hominem. You clearly know less than you think you do about GPS. Ironically, it seems like the mark of a contrarian to assume that people are attacking you when they aren't and a lot of climate skeptics come off sounding that way to me.

Furthermore, it seems you're still just launching your own arbitrary theories into the discussion and not responding to anything specifically wrong with the article.

Re: Antarctica losing six times more ice mass annually now than 40 years ago

#20

Post by shookness »

credit_guy wrote: post #5
shookness wrote: post #4

Earlier quoted context omitted.

Most of these ice mass measurements are made using GRACE not physical height / GPS measurements. Ice mass loss appears to be accelerating by multiple forms of measurement. https://www.nasa.gov/mission_pages/Grace/index.html

Fine, it's GRACE. So GRACE has an accuracy of 0.001%? Really? Or rather, is there any estimation technique to measure the ice mass of a whole continent with accuracy of one thousandth of one percent? Wait, actually they claim their accuracy is much higher, sometimes more precise than 0.0002% or even 0.0001% (I kid you not). Here's the wiki link for GRACE [1]. It states that during 2003-2013 the ice loss was 67±44 Gt…

Thanks for the sources. The Nature paper is very informative.
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