|Fig. 1 Antarctic Ice Stream|
Both are mistaken oversimplifications that leave out the crucial factors required for a robust understanding of the ongoing dynamics such as the fact that the "ice sheet" is actually hundreds of "ice streams," both small and large, like the sizes of creeks and rivers in water systems, flowing together and merging during a march to the sea.
There are some posts that detail some of the large ice streams in Greenland that are almost a thousand km in length (The Question Is: How Much Acceleration Is Involved In SLR - 5?).
Information in the video below indicates there are even longer ice streams in Antarctica.
|Fig. 2 Inverse color view of Fig. 1|
|Fig. 3 Ice stream flow|
Inverse colors of the same streams are shown in Fig. 2 and Fig. 4.
|Fig. 4 Inverse color view of Fig. 3|
Click on the images to enlarge them.
Anyway, you can see that these are more like river systems where small creeks feed large ones, then they flow into small rivers, which then flow into large rivers which empty into the sea.
The take away information is that these systems are not a large ice cube, they are large ice rivers that are constantly moving, constantly losing ice and mass at an accelerating rate.
That acceleration is being forced by the use of fossil fuels, which increases the quantity of greenhouse gases in the atmosphere.
Which accelerates global warming.
Since the north and south poles are heating at about 4 times or more higher than the rate of the non-polar regions, this is why Dredd Blog software models project an acceleration of sea level rise (SLR).
|Fig. 5 10.726 - 6.757 = 3.969m (20yr dbl)|
See if you notice when Dr. Rignot explains observations by scientists of an 8-fold acceleration of ice stream flow as the ice shelfs weaken to the point that large sections break off and float away.
Deniers claim that as the area of the ice shelf increases, it ipso facto means that the quantity of ice floating on the ocean surface increases.
That is mathematically false, as demonstrated by fifth grade science (How Fifth Graders Calculate Ice Volume, 2, 3, 4, 5).
|Fig. 6 18.694 - 6.757= 11.937m (10yr dbl)|
Big, big difference.
In closing, consider the impact of SLR on Washington, D.C. (where all the women are beautiful, and all the children are above average).
As shown by graphs in Fig. 5 and Fig. 6, the sea level has been and will continue to change.
D.C. is Station #360 in the PSMSL system, its tide gauge records began in 1931.
Those two graphs show SLR acceleration based on "10 and 20 year doubling."
The IPCC projected a 1-3m SLR for the same span of time ending in the year 2100.
Enjoy the video.
An up-to-date discussion of ice shelves vs. ice sheets, using the nomenclature of ice stream science:
15:29 when the ice shelf "Larsen A" collapsed the entire glacier's flow speed toward the sea increased ...
18:50 "Larsen B" ice shelf collapse caused the same thing ... the entire glacier's flow accelerated toward the sea ...
19:30 when the ice shelf goes away so does the restraint on the glacier, and they then move faster, 8 times faster, toward the sea
27:15 the East Antarctica Totten Glacier basin contains about as much ice as all of Western Antarctica, and it is destabilizing
30:30 the condition of the ice shelf controls what happens to the ice sheet