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.
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 per year. That ±44 Gt represents ±0.00017%
Anyway, here's the actual abstract of the nature article [2]
"The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain."
For those not familiar, East Antarctica is much bigger than West Antarctica, so it's natural for any measurement to be least certain. However, take a look at the prior estimates from the GRACE studies [3]
"An early analysis of GRACE-based studies data indicated that the EAIS was losing mass at a rate of 57 billion tonnes per year and that the total Antarctic ice sheet (including WAIS, and EAIS coastal areas) was losing mass at a rate of 152 cubic kilometers (c. 139 billion tonnes) per year.[4] A more recent estimate published in November 2012 and based on the GRACE data as well as on an improved glacial isostatic adjustment model indicates that East Antarctica actually gained mass from 2002 to 2010 at a rate of 60 ± 13 Gt/y."
This ± 13 Gt accuracy listed here is well below 0.0001%
> 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 straw man you create and then destroy. Time to turn that skepticism inwards.
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?
Yeah, but that same study showed that the rate of gains was slowing and more recent work by the same people using the same processes show it is now shedding mass.
credit_guy|7 years ago
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 per year. That ±44 Gt represents ±0.00017%
Anyway, here's the actual abstract of the nature article [2]
"The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain."
For those not familiar, East Antarctica is much bigger than West Antarctica, so it's natural for any measurement to be least certain. However, take a look at the prior estimates from the GRACE studies [3]
"An early analysis of GRACE-based studies data indicated that the EAIS was losing mass at a rate of 57 billion tonnes per year and that the total Antarctic ice sheet (including WAIS, and EAIS coastal areas) was losing mass at a rate of 152 cubic kilometers (c. 139 billion tonnes) per year.[4] A more recent estimate published in November 2012 and based on the GRACE data as well as on an improved glacial isostatic adjustment model indicates that East Antarctica actually gained mass from 2002 to 2010 at a rate of 60 ± 13 Gt/y."
This ± 13 Gt accuracy listed here is well below 0.0001%
[1] https://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_E...
[2]https://www.nature.com/articles/s41586-018-0179-y
[3]https://en.wikipedia.org/wiki/East_Antarctic_Ice_Sheet
flukus|7 years ago
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 straw man you create and then destroy. Time to turn that skepticism inwards.
brylie|7 years ago
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?
breakyerself|7 years ago
shookness|7 years ago