Yet another new paper reveals that the ice shelves of Antarctica are degenerating from below.
The paper surprisingly points out that some of that upwelling water sometimes even reaches the surface of the ice shelves.
II. Ice Shelf Stressors
The ocean tides bend and stress ice shelves each and every day (NASA Tracking the Influence of Tides on Ice Shelves In Antarctica).
Weak spots caused by cracking and other imperfections (dirt etc.) in the ice shelf: "Our observations show that basal channels are associated with the development of new zones of crevassing, suggesting that these channels may cause ice fracture." (Impacts of warm water on Antarctic ice shelf). [or be made by fractures]
The creation of sub-ice-shelf water channels is also caused or enhanced by ice sheet gravity:
"The mapping shows that basal channels have a tendency to form along the edges of islands and peninsulas, which are already weak areas on ice shelves. The team observed two locations where ice shelves are fracturing along basal channels, clear evidence that basal channel presence can weaken ice shelves to the point of breaking in vulnerable areas."(Warming ocean water undercuts Antarctic ice shelves, emphasis added).
Then the incessant pull of ice sheet gravity (like a continual high tide) on the ocean water under the ice sheets pulls it upward and presses it against then into cracks and other weak places (Polynyas)
Some polynyas form without channels and persist for years: see "Years observed", "Channel type ... None" (Supplementary Info, Appendix B, p. 22, PDF).
The result of this in the commentariat world is "worse than previously thought" (Rising Seas Could Threaten the World's Coastal Cities Much Sooner than Scientists Thought, Study Confirms; World’s Coastal Cities Unsavable; If We Don’t Slash Carbon Pollution, Ice melt could make seas rise 6 feet by 2100, study says).
III. Deeper Ghost Water Discovery
The ghost-water science is moving along on another front too:
"So Rignot and an international team of researchers took it upon themselves to map out 14 glacial fjords in West Greenland, north of the famous Ilulissat Glacier. At various points between 2007 and 2014, they measured temperature and depth in these fjords and used sonar to map out underwater topographic features. They found that the actual seafloor depths were anywhere from 100 to 1,000 meters deeper than what was previously suggested by the charts.(Greenland’s melting, OMG). Regular readers will remember that uncertainty in this area had caused me to be very conservative in calculations concerning how much ghost-water was located along the shores of ice sheet supporting land masses (The Ghost-Water Constant - 4).
The Oceans Melting Greenland, or OMG, mission kicked off last April with the goal of measuring ocean temperatures and modeling the shape and depth of the seafloor in Greenland to help scientists better understand the role the ocean plays in the melting of the ice sheet."
I may have to increase the percentage that I now use, once these studies become more robust by way of further discoveries.
IV. Warm Air Also Accelerates The Process
The ghost-water science is moving along ... faster ... in another area too:
Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6–9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics—including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs—that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.(Antarctica Melting). Over, around, under, and through is the way ghost-water is working to accelerate sea level change (by accelerating ice shelf disintegration which accelerates ice sheet flow into the ocean).
V. The Graphs of Wrath
That brings up the graphs in today's post, so let me describe them as pieces of portions of the evolving model.
I have not completely finished the fingerprint modules that project into the future, although some of the work is producing graphing data now.
The part that is unfinished has to do with the high-end estimates of future sea level change, and the expected finger prints in the future.
Anyway, the historical data is the basis of all of them.
Even he future projecting algorithms are all based on and spring from the official PSMSL official historical records.
Today's area involved in the graphs is AM.NW.SE (Hawaiian Islands).
This zone involves stations 2129 PORT ALLEN (HANAPEPE BAY, KAUAI ISLAND), 756 NAWILIWILI BAY (KAUAI ISLAND), 155 HONOLULU, 823 MOKUOLOE ISLAND, 2273 LANAI ISLAND KAUMALAPAU, 521 KAHULUI HARBOR (MAUI ISLAND), 2128 KAWAIHAE (HAWAII ISLAND), 300 HILO (HAWAII ISLAND).
The area's PSMSL mean historical sea level is shown in Fig. 1, the geographical fingerprint in Fig. 6, and the geophysical fingerprint is shown in Fig. 7 .
The graph at Fig. 8 shows how some ghost-water flows from the sea level fall areas in northern latitudes down to the AM.NW.SE sea level rise area of Hawaii, as rotational pull relocates it nearer to the equator.
The graphs at Fig. 2 and Fig. 5 show (in two graph styles) the historical, then future low-end IPCC / Hansen et. al. projections for the area.
The graphs at Fig. 3 and Fig. 4 show the geographical and geophysical effects on sea level change at the IPCC low end projections out beyond historical levels to the year 2100.
When I finish the high-end projections I will publish more graphs.
The bottom line for today's post is that ghost-water is a larger player in accurate projections than thermal expansion is, and that displacement (see Fig. 7) caused by calving and ice sheet melt is the big dog in sea level change.
The next post in this series is here, the previous post in this series is here.