August 31, 2022
An Uplifting Thing
John Lees
Today I have been doing a deep deep dive into Antarctic (and Greenland) ice mass loss/gain.
As many of you are aware, the estimate of how much ice is being lost or gained depends almost entirely on assumptions made regarding the motion of the bedrock beneath the ice.
Now, this is something almost comical. In 2012 a paper was published in which a comparison was made between the predicted bedrock uplift and values obtained via actual measurement using a form of ultra accurate GPS.
So, here is the plot of the predicted and measured values.
Anyone familiar with statistics textbooks will recognize this plot.
It's a random cluster of values with no correlation.
So what do we learn? The predictions clearly had little value.
The problem for Antarctica is that there are only a few locations where the rock breaks the surface of the ice sheet. And everywhere else, you can not measure the motion of the bedrock.
So for those vast regions of solid ice, the untested predicted values are all that we have. And the predicted values are plainly crap:
from: https://academic.oup.com/gji/article/190/3/1464/570434
Frank Lasee replies:
There is almost no snow in Antarctica. It stands to reason that there is little motion. Because extremely cold and little snow. Little expansion of the glaciers.
Greenland huge snows. And it warms some more in the summer. And is subject to different more variable ocean currents. glaciers constantly growing and lots of ice bergs. Caused by the growing glaciers.
Mr. Lees responds:
This motion (bedrock uplift) is caused by the removal of vast quantities of ice at the end of the last glaciation. The same reason why Sweden or Canada are rising. So, this is a measure of the "rebound" not the accumulation of snow currently.
Tim adds:
That makes me wonder John; is perhaps there so much more dry land in the northern hemisphere at least in part a function of the smaller ice mass in the Arctic as opposed to the Antarctic? As you say less wieight is causing Canada and Sweden to rise. Perhaps the greater weight of ice in Antarctica has prevented more land from uplifting in South America? Just a speculative thought.
Today I have been doing a deep deep dive into Antarctic (and Greenland) ice mass loss/gain.
As many of you are aware, the estimate of how much ice is being lost or gained depends almost entirely on assumptions made regarding the motion of the bedrock beneath the ice.
Now, this is something almost comical. In 2012 a paper was published in which a comparison was made between the predicted bedrock uplift and values obtained via actual measurement using a form of ultra accurate GPS.
So, here is the plot of the predicted and measured values.
Anyone familiar with statistics textbooks will recognize this plot.
It's a random cluster of values with no correlation.
So what do we learn? The predictions clearly had little value.
The problem for Antarctica is that there are only a few locations where the rock breaks the surface of the ice sheet. And everywhere else, you can not measure the motion of the bedrock.
So for those vast regions of solid ice, the untested predicted values are all that we have. And the predicted values are plainly crap:
from: https://academic.oup.com/gji/article/190/3/1464/570434
Frank Lasee replies:
There is almost no snow in Antarctica. It stands to reason that there is little motion. Because extremely cold and little snow. Little expansion of the glaciers.
Greenland huge snows. And it warms some more in the summer. And is subject to different more variable ocean currents. glaciers constantly growing and lots of ice bergs. Caused by the growing glaciers.
Mr. Lees responds:
This motion (bedrock uplift) is caused by the removal of vast quantities of ice at the end of the last glaciation. The same reason why Sweden or Canada are rising. So, this is a measure of the "rebound" not the accumulation of snow currently.
Tim adds:
That makes me wonder John; is perhaps there so much more dry land in the northern hemisphere at least in part a function of the smaller ice mass in the Arctic as opposed to the Antarctic? As you say less wieight is causing Canada and Sweden to rise. Perhaps the greater weight of ice in Antarctica has prevented more land from uplifting in South America? Just a speculative thought.
Posted by: Timothy Birdnow at
09:00 AM
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There is almost no snow in Antarctica. It stands to reason that there is little motion. Because extremely cold and little snow. Little expansion of the glaciers.
Posted by: Breitling Replica at June 16, 2023 07:48 AM (SUYyh)
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