|Fig. 1 Antarctica Sectors & Zones|
This series details the textbook changes in our understanding of the "land down under the land down under".
It was the land that never changed, the land out of sight, and the land out of mind.
Not much was known about it, except that it never changed in a million years because it was way down near, or at, the edge of the flat Earth where one could fall off the edge, never to see the light of day again (that was Antarctica 1.0).
Nowadays, Antarctica is not only the largest desert on Earth, it is one of the most studied places on earth, one of the most consequential places on Earth, and perhaps even the greatest threat to modern civilization (Antarctica 2.0, 2, 3, 4, 5, 6 [& supplements A, B, C, D, E, F], 7, 8, 9, 10).
|Territory of Plumes|
To those scientists it is still Antarctica 1.0, a place which grows in terms of its number of gigatons of ice, because they think that the annual precipitation increases the ice mass there (They do not consider that the Sahara Desert receives more annual precipitation per square mile than Antarctica, the greatest desert on Earth, receives).
III. Today's Focus
Today we get back to the "Grounding Line", a place that is what we should focus on and pay special attention to, according to Dr. Rignot (see the video below if you haven't already).
In compliance with his urging, I have isolated the focus into six "areas" or "sectors" of the tidewater glacier coastline, where the grounding lines tend to be (Fig. 1).
The grounding line is constantly changing, more in some areas/sectors than others, as today's appendices point out.
A lot of the WOD zones (Fig. 1) along the grounding line have not yet been measured in situ by researchers with CTD drones or otherwise, so the grounding line conditions in such zones are not featured in today's presentation.
Thus, as it turns out, today's presentation likely contains understatements in terms of the potential sea level impact that tidewater glacier melt at the grounding lines is having.
Today, however, I am not going to speculate on how much more sea level rise would ensue if we knew the in situ values of the WOD zones in those, at this time, missing values.
So, on with the show:
|Western Pacific |
IV. What To Focus On
While reading the appendices, keep in mind the focus of the formulas being applied to the in situ measurements.
That focus is on the melting ice at the grounding line, which is ice that is land based.
That means the melt water from that grounding line ice has an SLE (sea level equivalent) factor unlike the floating ice shelf beyond the grounding line (i.e ice that is floating in the tidewater).
The ice shelf beyond the grounding line has already displaced sea water, which impacts the sea level, however the ice sitting on land at the grounding line does not have an impact on sea level until it melts.
Another factor is acceleration via "buoyancy", in that, there is an additional upward acceleration of the plume melt water flow in addition to the buoyancy flow caused by the density difference between the fresh-water plume and the ambient seawater (sea water is more dense than they fresh-water plume).
That additional upward acceleration factor is caused by the impact of the seawater as it flows into the volume gap caused when the ice becomes water (ice takes up more space than fresh water does, so, a small void is created when melt takes place).
And finally for today, note that the values in those appendices listed above (in section III) are based on a one meter (1m) melt face (i.e a 1m plume height).
That tiny 1m of melt action, creating an upward flowing plume, totals (adds up) to a "4.26196 mm yr" SLE.
That is, it would cause 4.26 mm of mean sea level rise (see Appendix Combo).
That 4.26 mm yr figure is more than the actual mean average sea level rise (which is ~3.5 mm yr).
Thus, we know that less than 1m of melt takes place along the 46,387 (km) grounding line length being focused on ... which means ... drum roll ... that a lot of melt potential is there at the grounding line (ibid).
Some of the glaciers have many, many meters of ice there waiting to melt into plumes.
V. Closing Comments
Here are some graphs showing the difference between plume density and ambient seawater density (Graphs).
The plume density is less than the seawater density, so the plume water is forced upward.
The previous post in this series is here.