|Fig. 1 Tidewater Glacier Areas and Zones|
I. A Brief Review
I began this series by pointing out that, like ghost water around ice sheets, ghost plumes are in effect hidden in plain sight (The Ghost Plumes).
I went on, in subsequent posts in this series, to explain that I think that the "bathtub model" and "thermal expansion model" thinking is what hides the ghost plumes from contemplation (thermal expansion is the "go to guy" when the ice mass loss and sea level data is insufficient to explain sea level change).
That state of being "hidden" is most likely caused by the catch-all buffer hypothesis which says the ocean expands when warmed, so if we can't find enough ice mass loss to account for sea level rise quantities, then we blame it on the mysterious catch-all "thermal expansion".
It is a convenient way out, like what was used to explain sea level fall before we remembered Newton sitting under the apple tree and until NASA caught mean old Mr. Gravity in the act of hiding a great big horde of ghost water (NASA Busts The Ghost).
Finding additional ways the ice could be melting was left by the wayside and the thermal half-truth took charge (On Thermal Expansion & Thermal Contraction - 39).
Then, along came the R. Bindschadler et al. 2011 paper which gave us a good handle on the extent of the grounding lines of tidewater glaciers.
Bindschadler et al. 2011 was recently was followed up by Rignot et al. 2019 which used multi-faceted analyses to tell us more about glacial melt in the tidewaters of Antarctica (Four decades of Antarctic Ice Sheet mass balance from 1979–2017).
II. Measurements, Measurements and Measurements
The gist of the two papers I cited above is that Antarctica is so vast that we have to find non-conventional ways of using measurements to detect what is happening in Antarctica, in terms of tidewater glacial disintegration and their melting.
The Bindschadler crew used photographs of coastal areas taken by satellites to identify where the grounding lines of tidewater glaciers are, then measured the cumulative length of the grounding lines.
The Rignot crew used gravitational readings along with photos to calculate the retreat of tidewater glacier grounding lines to calculate the amount of ice mass loss.
I use both of their research conclusions to try to develop a cognitive radar with which to surmise potential melt in all areas where grounding lines have been detected.
The analysis is basically: "1) if the grounding lines are "X" meters long in a particular zone; 2) if we can reasonably estimate the amount of the ice face of the glaciers contacted by the tidewater; 3) if we can calculate, using in situ measurements, whether the tidewater is of sufficient Conservative Temperature (CT) and Absolute Salinity (SA) values, as calculated using the TEOS-10 software; then 4) we can make reasonable estimates of plume volume potential."
III. Finding Basic Values
I am still perfecting the calculations concerning the grounding lines, so today I present an updated view of those calculations that were presented in the previous post: The Ghost Plumes - 8.
One thing to remember is that the glacial ice is much closer to pure water than it is to seawater because, among other things, the saltiness is ejected during the freezing process.
For that reason, I believe it is more accurate to use today's 361.841 Gt value as the equivalent of 361,841 m3 of melt water.
Previously I used 365 Gt, so that is not much of a change to cause a redo (but there are also commas in the most recent big numbers!).
The bottom line is that in the final result, shown below, the cubic meter melt water values and the gigaton ice mass values have the same digits (but have a different decimal point location).
The graphic at Fig. 1 shows the geographical locations of the "Areas" and the "Zones" listed below.
Remember that this is a display of the values that would be derived in each Area and in each Zone WHEN the ghost plumes cause one millimeter of global mean sea level rise (1 mm GMSL).
IV. The Results
Note that the Area ("A-F") totals are presented at the end of each area's table, and the grand totals of all those Areas combined is presented after all the Areas have been presented.
So here we go:
(1 mm yr due to 361.841 Gt yr Ice mass loss
caused by plumes of melt water)
RE: Global Mean Sea Level (GMSL)
Melt Water at 361,841 m3 raises GMSL one millimeter
(current total GMSL is ~3.4 mm yr)
RE: Relevant Antarctica Grounding Line (AGL)
AGL length: 47,455,400 m (Bindschadler et al. 2011)
West Indian Ocean (Area A)
Area's Percent of AGL (APGL): 14.1758%
Breakdown by WOD Zones in Area A:
|Zone Ice Loss|
Area A Totals: Meltwater volume: 58,133.1 m3; Ice Loss: 58.1331 Gt
East Indian Ocean (Area B)
Area's Percent of AGL (APGL): 16.6161%
Breakdown by WOD Zones in Area B:
|Zone Ice Loss|
Area B Totals: Meltwater volume: 68,140.2 m3; Ice Loss: 68.1402 Gt
Ross Sea (Area C)
Area's Percent of AGL (APGL): 20.3385%
Breakdown by WOD Zones in Area C:
|Zone Ice Loss|
Area C Totals: Meltwater volume: 83,405.5 m3; Ice Loss: 83.4055 Gt
Amundsen Sea (Area D)
Area's Percent of AGL (APGL): 8.04768%
Breakdown by WOD Zones in Area D:
|Zone Ice Loss|
Area D Totals: Meltwater volume: 33,002.4 m3; Ice Loss: 33.0024 Gt
Bellingshausen Sea (Area E)
Area's Percent of AGL (APGL): 31.2306%
Breakdown by WOD Zones in Area E:
|Zone Ice Loss|
Area E Totals: Meltwater volume: 128,072 m3; Ice Loss: 128.072 Gt
Weddell Sea (Area F)
Area's Percent of AGL (APGL): 9.5913%
Breakdown by WOD Zones in Area F:
|Zone Ice Loss|
Area F Totals: Meltwater volume: 39,332.7 m3; Ice Loss: 39.3327 Gt
Antarctica Annual Totals: Meltwater volume: 410,086 m3; Ice Loss: 410.086 Gt
Note: Rignot et al. calculated ice loss at 252 +- 26 Gt/y during 2009-2017 (PNAS)
V. Closing Comments
Note that the Rignot team's value for total gigatons of ice loss is less than that which 1 mm of SLR would compel by my calculations.
That is a good sign because the real scientists always underestimate ;-) ... just kidding ... these values today do not include the "Conservative Temperature (CT) and Absolute Salinity (SA) values, as calculated using the TEOS-10 software" mentioned in Section II above.
These are merely calculations showing what ice melt values would derive @ 1 mm of GMSLR.
I am in the process of fusing the TEOS-10 calculations in The Ghost Plumes - 7
with this calculation set and the Countries With Sea Level Change - 2 set.
But, before it can be universally applied (i.e. include Greenland etc.) I have to derive Greenland etc. values.
In an earlier paper (9 years earlier), Rignot seems to allude to ghost plumes and gives some indication of those values:
"These rates of submarine melting are two orders of magnitude larger than surface melt rates, but comparable to rates of iceberg discharge. We conclude that ocean waters melt a considerable, but highly variable, fraction of the calving fronts of glaciers before they disintegrate into icebergs, and suggest that submarine melting must have a profound influence on grounding-line stability and ice-flow dynamics ... The widespread two to threefold acceleration of the glaciers cannot be explained solely by enhanced lubrication of the bed from surface meltwater, for seasonal variations in glacier velocity do not exceed 8–10%, independent of latitude. Glacier acceleration is instead probably caused by the ungrounding of ice fronts from the bed, which reduces buttressing of inland ice and entrains faster rates of ice flow to the ocean. To unground glaciers from the bed, they must melt and thin. Warmer air temperatures thin the glaciers from the surface and allow the ice flotation margin to migrate inland. Such surface melting is well documented in Greenland. However, melting can also occur along the submarine termini of the glaciers. A warmer ocean will erode submerged grounded ice and cause the grounding line to retreat. In contrast, we know very little about rates of submarine melting along calving fronts. The only measurements of submarine glacier melting so far have been conducted in Alaska"(Rignot et al. 2010, Nature Geoscience, emphasis added). He may have been the first to contemplate ghost plumes.
"Surface melt rates in the lower 5 km of the three glacier systems averaged 4–18 cm d−1 in July–August 2008 (highest value in July; refs 12, 14). Our inferred submarine melting rates are two orders of magnitude larger [than 'Surface melt rates']. Submarine melting is therefore a major ablation process across tidewater glacier fronts. This has several important consequences for glacier dynamics. First, submarine melting is more likely to dislodge glaciers from their beds than surface melting. Enhanced submarine melting, either from warmer ocean waters or enhanced forced convection by increased subglacial discharge, will melt grounded ice directly and cause grounding-line retreat. Our data show that a thermal forcing of 3 ◦ C melts ice at a rate of several metres per day, that is, hundreds of metres in one summer. In comparison, an increase in surface melting will be effective at ungrounding a glacier only if the glacier surface slope is low so that the line of hydrostatic equilibrium retreats rapidly with a small change in ice thickness. Furthermore, if the glacier retreats into deeper waters, submarine melting will increase because the submerged area and the pressure-dependent melting point of ice will both increase, two positive feedbacks. Moreover, submarine melting must have an enormous influence on ice calving mechanics. Pronounced submarine melting will undercut the submerged ice faces and promote calving from below the water surface, a mode of calving frequently observed at tidewater termini."
Anyway, I am marshaling their Greenland data for future inclusion along with the Antarctica data shown in the Section IV. tables above.
The previous post in this series is here.