In Search Of Ocean Heat - 14

Awaiting Thwaites
("enough ice to raise
sea levels by 10 feet")

I. Background

Two papers published recently addressed a subject Dredd Blog has discussed in various and sundry ways at various and sundry times.

The first paper is "Suppressed basal melting in the eastern Thwaites Glacier grounding zone" (hereinafter "Nature 2023, Suppressed basal melting"); the other one is  "Heterogeneous melting near the Thwaites Glacier grounding line" (hereinafter "Nature 2023, Heterogeneous melting").

The various and sundry Dredd Blog series on the subject matter are (Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers, 2, 3, 4, 5, 6, 7; In Pursuit of Plume Theory, 2, 3; Antarctica 2.0, 2, 3, 4, 5, 6 [& supplements A, B, C, D, E, F], 7, 8, 9, 10, 11;
Mysterious Zones of Antarctica, 2, 3, 4; etc.).

II. The Issues

Dr. Eric Rignot is one of the authors in both papers referred to above in Section I.

He was voted into the Academy of Sciences not too long ago (Academy of Sciences; cf. How Ice is Melting and What We Should Do About It).

Some of his work involves increasing the accuracy of calculating the ever changing location of the "grounding line" of tidewater glaciers along the coastline of Antarctica (ibid).

That has been helpful to those who want to do research there, of course, and so we have now reached the obvious:

"Thwaites Glacier is thought to be susceptible to runaway retreat triggered at the grounding line (GL) at which the glacier reaches the ocean. Recent ice-flow acceleration and retreat of the ice front and GL indicate that ice loss will continue."

(Nature 2023, Hetergeneous melting, at 471, emphasis added). Why that is significant is explained on the same page of that paper:

"Offshore ocean and atmospheric conditions force warm circumpolar deep water (CDW) onto the Amundsen Sea continental shelf, where it contributes to ice loss and GL retreat of glaciers draining this sector of the West Antarctic Ice Sheet, including Thwaites Glacier. Thwaites Glacier extends seaward from the Walgreen Coast, forming the Thwaites Glacier Tongue (TGT) to the west and the TEIS that rests on a prominent sea-floor pinning point (Fig. 1a). Warm CDW flows towards the glacier along the coastline and through sea-floor channels, where it drives melting. The bed underneath the upstream grounded ice deepens to a maximum of 2,300 m below sea level, making it susceptible to large-scale retreat from ocean-driven melting. Collapse of Thwaites Glacier, which itself represents more than half a metre of global sea-level-rise potential, could also destabilize neighbouring glaciers that account for a further 3m of future sea level rise."

(ibid p. 471, emphasis added). Ice shelf (not ice sheet) melt also is impacted:

"The rate of ice-shelf mass loss has increased by 70% between 1994 and 2012, precipitating a shift towards faster drainage of grounded ice into the ocean. Several major grounding lines in the Amundsen Sea sector have retreated rapidly inland, raising the possibility of an unstable collapse of the WAIS. Nowhere are these processes more apparent and potentially serious than at Thwaites Glacier, which drains about 10% of the WAIS. Thwaites is largely grounded below sea level on a retrograde bed 4 (that is, a bed that deepens inland) and is particularly susceptible to marine ice-sheet instabilities. Its grounding line has retreated 14 km inland since the late 1990s and, in some regions, is retreating by up to 1.2 km per year at present."

(Nature 2023, Suppressed basal melting, at 479, emphasis added). This same likelihood exists at various and sundry locations all around the glacial bases all around the ~58,000 km of grounding lines along the coast of the continent of Antarctica.

III. New

The Southern Ocean around Antarctica was only recently officially recognized (New Ocean), but the scientific models still don't recognize it:

"Models of ocean forcing are often limited by resolution or available parameterizations. Generally, models represent ice shelves simplistically as wedges of ice with flat or curved interfaces and an inferred sea-floor geometry as a function of distance from the presumed GL. Usually a zero-melt condition is imposed at the GL, which is inconsistent with evidence of thinning and GL retreat. Although retrograde bed slopes facilitate positive feedback in grounded ice loss from ocean-forced melt, glaciers resting on prograde slopes still face influence from warm water undercutting the ice."

(ibid p. 471). Dredd Blog has pointed out in various and sundry ways that the science of Oceanography needs to enter the quantum physics age where photons really do exist (Quantum Oceanography, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16).

IV. Parting Ways

Where I part ways with the two papers is when they mention "a thousand years" within a inference of "nothing to see here folks, move along."

The scientist who warned congress on related matters in 1988 (3 and a half decades ago) was aware of that phenomenon and wrote a paper laying it all out:

"I suggest that a 'scientific reticence' is inhibiting the communication of a threat of a potentially large sea level rise. Delay is dangerous because of system inertias that could create a situation with future sea level changes out of our control. I argue for calling together a panel of scientific leaders to hear evidence and issue a prompt plain-written report on current understanding of the sea level change issue."

 (Scientific Reticence, Hansen). The reason I take issue with how long it will take for Antarctica to melt is that it is utterly irrelevant.

What matters is how long will it take for a tiny, tiny portion of the Cryosphere (1.14%) or of Antarctica (1.25%) to melt to do substantial damage to civilization as we know it (The Extinction of Robust Sea Ports, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13).

V. Closing Comments

Regular readers might also remember (The Ghost-Water Constant, 2, 3, 4, 5, 6, 7, 8, 9; The Gravity of Sea Level Change, 2, 3, 4, 5; NASA Busts The Ghost; The Ghost Plumes, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15; and The Ghost Photons, 2, 3).  

The next post in this series is here, the previous post in this series is here.

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