|Fig. 1 Ongoing Ice Shelf Melt (click to enlarge)|
The other ~93% of the story is what is happening to the oceans in terms of warming, and in terms of what that warming is doing to the sources of sea level rise (Why Sea Level Rise May Be The Greatest Threat To Civilization, 2, 3, 4, 5).
I say that, because "Since 1955, over 90% of the excess heat trapped by greenhouse gases has been stored in the oceans ... the smallest fraction of this thermal energy goes into warming the atmosphere" (The Damaged Global Climate System - 4).
The Eric Rignot Research Group explains how that relates to sea level rise:
Ocean waters melting the undersides of Antarctic ice shelves, not icebergs calving into the sea, are responsible for most of the continent’s ice loss ... ice dissolving from underneath, accounted for 55 percent of shelf loss from 2003 to 2008 – a rate much higher than previously thought. Ice shelves, floating extensions of glaciers, fringe 75 percent of the vast, frozen continent ... It turns out that the tug of seawaters just above the freezing point matters more than the breaking off of bergs ... “This has profound implications for our understanding of interactions between Antarctica and climate change. It basically puts the Southern Ocean up front as the most significant control on the evolution of the polar ice sheet”... The three giant ice shelves of Ross, Filchner and Ronne, which make up two-thirds of Antarctica’s ice shelves, accounted for only 15 percent of the melting. Meanwhile, less than a dozen small ice shelves floating on relatively warm waters produced half the total meltwater during the same period ... The researchers also compared the rates at which the ice shelves are shedding ice with the speed at which the continent itself is losing mass and found that, on average, the shelves lost mass twice as fast as the Antarctic ice sheet did ... “Ice shelf melt can be compensated by ice flow from the continent,” Rignot said. “But in a number of places around Antarctica, they [shelves] are melting too fast, and as a consequence, glaciers and the entire continent are changing.”(Warm Ocean Drives Most Antarctic Ice Shelf Loss, emphasis added). This is a critical dynamic, as explained in the first post of this series.
Because, for one thing, the ice sheet streams which end at the ocean, will speed up as much as 8 times as the ice shelves weaken then break up.
|Fig. 2 Antarctica overtakes Greenland|
This ice shelf melting (Fig. 1) does not add much directly, if any, to sea level rise, however, ice flow into the ocean will be facilitated, so there will be an indirect increase in sea level rise as a result.
That is, the demise of the Antarctic ice shelves will lead to the increase of Antarctic ice sheet mass loss (Fig. 2).
Thus, this ~93% of the global warming going into the oceans (Fig. 3), and this ~7% of the
|Fig. 3 Warming @ 400m down (36+ deg. F)|
Canaries that were in reality given only lip service in the recent example (COP21) of the best that current civilization can do (Paris Climate Change Conference Begins).
This will not play out well for the rich, or for the poor (Weekend Rebel Science Excursion - 44, The 1% May Face The Wrath of Sea Level Rise First).
The next post in this series is here, the previous post in this series is here.
A discussion about ice shelves vs. ice sheets:
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
The dramatic calving of icebergs shown in the video below, is not as fast or as big as subsurface melt: