[First paragraph abridged -cr:
A new model… suggests that… may be… could eventually… sea level rise.]
CREDIT: COURTESY OF ANDY THOMPSON
A new model developed by Caltech and JPL researchers suggests that Antarctica’s ice shelves may be melting at an accelerated rate, which could eventually contribute to more rapid sea level rise. The model accounts for an often-overlooked narrow ocean current along the Antarctic coast and simulates how rapidly flowing freshwater, melted from the ice shelves, can trap dense warm ocean water at the base of the ice, causing it to warm and melt even more.
The study was conducted in the laboratory of Andy Thompson, professor of environmental science and engineering, and appears in the journal Science Advances on August 12.
Ice shelves are outcroppings of the Antarctic ice sheet, found where the ice juts out from land and floats on top of the ocean. The shelves, which are each several hundred meters thick, act as a protective buffer for the mainland ice, keeping the whole ice sheet from flowing into the ocean (which would dramatically raise global sea levels). However, a warming atmosphere and warming oceans caused by climate change are increasing the speed at which these ice shelves are melting, threatening their ability to hold back the flow of the ice sheet into the ocean.
“If this mechanism that we’ve been studying is active in the real world, it may mean that ice shelf melt rates are 20 to 40 percent higher than the predictions in global climate models, which typically cannot simulate these strong currents near the Antarctic coast,” Thompson says.
In this study, led by senior research scientist Mar Flexas, the researchers focused on one area of Antarctica: the West Antarctic Peninsula (WAP). Antarctica is roughly shaped like a disk, except where the WAP protrudes out of the high polar latitudes and into lower, warmer latitudes. It is here that Antarctica sees the most dramatic changes due to climate change. The team has previously deployed autonomous vehicles in this region, and scientists have used data from instrumented elephant seals to measure temperature and salinity in the water and ice.
The team’s model takes into account the narrow Antarctic Coastal Current that runs counterclockwise around the entire Antarctic continent, a current which many climate models do not include because it is so small.
“Large global climate models don’t include this coastal current, because it’s very narrow—only about 20 kilometers wide, while most climate models only capture currents that are 100 kilometers across or larger,” Flexas explains. “So, there is a potential for those models to not represent future melt rates very accurately.”
The model illustrates how freshwater that melts from ice at the WAP is carried by the coastal current and transported around the continent. The less-dense freshwater moves along quickly near the surface of the ocean and traps relatively warm ocean saltwater against the underside of the ice shelves. This then causes the ice shelves to melt from below. In this way, increased meltwater at the WAP can propagate climate warming via the Coastal Current, which in turn can also escalate melting even at West Antarctic ice shelves thousands of kilometers away from the peninsula. This remote warming mechanism may be part of the reason that the loss of volume from West Antarctic ice shelves has accelerated in recent decades.
“There are aspects of the climate system that we are still discovering,” Thompson says. “As we’ve made progress in our ability to model interactions between the ocean, ice shelves, and atmosphere, we’re able to make more accurate predictions with better constraints on uncertainty. We may need to revisit some of the predictions of sea level rise in the next decades or century—that’s work that we’ll do going forward.”
The paper is titled “Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica.” In addition to Flexas and Thompson, additional coauthors are Michael Schodlok and Hong Zhang of JPL, and Kevin Speer of Florida State University. Funding was provided by the National Science Foundation, the NASA Physical Oceanography program and Cryospheric Sciences program, NASA’s Internal Research and Technology Development program (Earth 2050 project), JPL, and Caltech. Caltech manages JPL for NASA.
JOURNAL
Science Advances
DOI
ARTICLE TITLE
Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica
ARTICLE PUBLICATION DATE
12-Aug-2022
Uses the words and logic of a flimflam.
“model accounts for an often-overlooked narrow ocean current along the Antarctic coast“
Overlooked?
“and simulates how rapidly flowing freshwater“
Now, magical mysterious freshwater sources flow “rapidly”? Their model’s algorithms sounds predisposed to give you that data. Confirmation bias is an understatement here.
Yawn.
Another model showing that it’s worse than we thought. Again.
Why bother to read it?
In the fable, “The Boy Who Cried Wolf”, the wolf was real, it had come before, and it eventually came again.
But everyone should have noticed by now that the climate wolf is late.
Ice floating in water will not raise the level of the water by melting.
New Computer model = new Video game.
So what?
No actual ice was melted in producing that paper.
One frequently reads such claims. However, for it to be true, there would have to be negligible friction at the ice-bedrock boundary upslope from the shoreline. In reality, the controls on all glacier movement, in all environments, are a function of the ice thickness, the micro-level rock friction (modified by water films), the macro-level friction which incorporates the sub-ice topography and the average slope of the bedrock. When the bedrock topography is quite irregular, ice either has to be pushed uphill, or if there is insufficient force, the ice has to shear over the obstructions. All this can be modeled as different kinds of friction.
Newton’s First Law states that an object in motion tends to continue in a straight line unless acted upon by another force. This is sometimes referred to as inertia. If a glacier with forward motion enters the ocean, and new ice freezes onto the leading edge, the new ice inherits the forward velocity of the glacial ice. Thus, some force will be required to slow or stop the ice glacial ice. The floating sea ice isn’t it because it has the same velocity as the glacier. Once again, the alarmists have got cause and effect backwards.
If the glacier enters water shallow enough that it is still grounded, the buoyancy reduces the bottom friction; when the ice (whatever its origin) is floating there is little ‘friction.’ (Consider the effort necessary to push a 100-lb block of ice across the rough concrete deck of a swimming pool, versus what it takes to move that block once it falls into the pool.) Then, in addition to upslope friction with the bedrock, there will be a lesser amount of friction added to that land friction controlling the overall speed. If the shelf ice, whether riding on the bottom or not, encounters a transverse bedrock ridge, or former terminal moraine, then there will be a compressive or shearing force resisting the forward motion. However, one would expect to see ice piling up and thickening, as in the ridges in the Arctic pack ice. Instead, the more obvious Antarctic features are tension cracks.
The quoted assertion at the top is over-simplified. While it provides a mental image that one can relate to, it leaves too much out to be considered to be much more than hand waving.
In the end it all comes down to this. Where is the water? We have been promised catastrophic sea level rise for decades. We have been pummeled with supposed “science” that says that the ice sheets of Antarctica and Greenland are melting away for decades.
And yet no catastrophic SLR! The rise continues at the moderate rate of the pre-industrial age. Manhattan is still above water. The west side hwy is still above water. The tunnels of the big dig in Boston are still dry. Venice is still there. New Orleans is still there.
SLR talks and the rest of the bull shit walks! Put up or shut up you liars.
If we take Professor Andy Thompson’s definition at its face value sic Ice shelves are outcroppings of the Antarctic ice sheet, found where the ice juts out from land and floats on top of the ocean. The shelves, which are each several hundred meters thick, act as a protective buffer for the mainland ice, keeping the whole ice sheet from flowing into the ocean (which would dramatically raise global sea levels) – it is clear that the ice shelves have already displaced their own weight in water. Therefore, melting of the ice shelf will have no result in sea level changes.
I would suggest that the researchers including Thompson get an age approximation profile of the shelf ice and the land-bound ice. Of course, the shelf ice as described by Thompson is unrelated time-wise to the permanent and continuously accreting ice cap such the area intersected by such core holes as Vostok 3 etc. Drilling to 3,200 metres (Vostok 3) is not possible unless the ice is absolutely and perfectly stable and not moving. That the permanent ice has been accumulating for close to 1 million years without a break signifies a stable climate. That is despite the 6 or so glacial periods and accompanying sea level changes that have occurred over that interval of time.
sounds like that might be what some fools used today at the adelaide advertiser to claim SA coastal waters are rising faster than other places?
pay to read;-(
Just filed this one in the climate cabinet marked, ‘It’s worse than we thought’
Fed up with this kind of demagoguery:
” Antarctica’s Ice Shelves Could be Melting Faster Than We thought ”
“Could be” OR “are“???
At each “could be” that I stumble upon, I stop reading: this is a BS signal)
What is the probability of a “could be” event? 50%? Or lower? Things are bad enough that climatology measurements often have uncertainties that are +/-50% or more of the nominal measurement. It is much worse when the sign of the value isn’t even known with any reliability and the proponent has to resort to vague probabilities such as the sun ‘could’ supernovae at any time.
“The model illustrates how freshwater that melts from ice at the WAP is carried by the coastal current and transported around the continent. The less-dense freshwater moves along quickly near the surface of the ocean and traps relatively warm ocean saltwater against the underside of the ice shelves.”
Models do not match observations so are garbage and wrong.
Since when has trapping relatively warm ocean seawater from the WAP been -2c?
Can they explain how -2c water melts the underside of the ice shelves?
This is an example from Summer back in 1998 with relatively warm ocean water between -0.6c and -2c.
I forgot to add that this coastal current will also be below the surface where the Ice shelf can go 50m+ below sea level. The temperature does get slightly warmer the further down the depth with the peak being 2c at 400m depth.
The link below using Argo-data shows selected depths of the circum-antarctic ocean. The Argo-data shows either no warming or very little warming (<0.2c) at different depths for the duration.
It never ceases to amaze me that people persist in calling these computer modelling exercises ‘studies’. They are not studies, studies use the available data to make determinations. These computer modelling exercises make guesses about what the data will look like in the future, then make guesses about what that may cause. That is not a study.
““If this mechanism that we’ve been studying is active in the real world, it may mean that ice shelf melt rates are 20 to 40 percent higher than the predictions in global climate models,”
Antarctic Sea Ice is unchanging for 50 years or so….see: https://www.epa.gov/climate-indicators/climate-change-indicators-antarctic-sea-ice
Area of Antarctic Ice Shelves does not seem to be a metric that is recorded.
Anyone have a source for that? Antarctic Ice shelf area?
Try the following FTP site, linked to from some NSIDC webpages, which they say measure “sea ice” rather than “ice shelves” :
ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G02135/north/monthly/data/
Although the files are titled “*_extent_v3.0.csv” each header line is :
“year, mo, data-type, region, extent, area”
Note that the “./north/daily/data/” directory only contains an “Extent” column of data though.
Mark ==> Thanks — Antarctic Sea Ice Extent is fairly well documented….I am looking for actual data to back-up or refute the idea that Antarctic Ice Shelves are losing ice/getting smaller. .
This is an unclear target to aim at.
My plot of the data from the “./G02135/south/monthly/data/” files (up to the March minima, the last time I updated that particular spreadsheet).
NB : “Extent” is the solid line, “Area” is the dashed one.
Could you extract the “idea” you have in mind from the (monthly) data used to generate that graphic ?
PS : MattG’s coloured “ice shelf area” data sum to around 1 million square kilometres, while the minimum in the graph below is 1.3 (in February 1993).
I don’t think those (limited) “ice shelves” have ever melted (since 1979). They have always been seen (by satellites) as “100% ice covered”.
Mark ==> Yes, it is the area of ” those (limited) “ice shelves” have [n]ever melted (since 1979). They have always been seen (by satellites) as “100% ice covered”.” that I am looking for. Some measurement…..
The ice shelves do change area when a piece breaks off at the sea edge (calving).
There is a hypothetical that the ice shelves are “losing ice”….
An idea I had just after the “Edit” time on my previous post had expired …
If you assume the “annual minimum” value for “sea-ice extent/area” comes each year just as 100% of the “ocean” sea-ice has melted … that would mean the “extent/area” number that’s left is equal to the (coastal ?) “ice shelf extent/area” …
Tenuous I know, but the “appropriate” (???) graphic then becomes the one below :
Mark ==> I appreciate your help — that might be possible. But the Ice Shelves themselves are 100s of feet thick and sea ice is confined to a few meters — I think that minimum Antarctic sea ice is changes each year … if it were th same each year, then we could assumed that the remainder of ice over water was ice shelf.
I know this is from wikipedia but it does have the size in area of all ice shelves.
The link doesn’t seem to show the values so I have added them below.
Antarctica’s major ice shelves: Ross (472,960 km2) Filchner-Ronne (422,420 km2) Amery (62,620 km2) Larsen (48,600 km2) Riiser-Larsen (48,180 km2) Fimbul (41,060 km2) Shackleton (33,820 km2) George VI (23,880 km2) West (16,370 km2) Wilkins (13,680 km2)
Matt ==> Thank you for the effort. Getting closer. Maybe we could measure extent of ice shelves with Google Earth?
Actually, I am looking for some physically measured metric of Ice Shelves area — increasing decreasing, etc.
Appreciate the help.
Came across this paper while looking, but it’s paywalled (for me, et least).
Greene et al (2021), “Antarctic calving loss rivals ice-shelf thinning” : Link
The “Supplementary Table 1” Excel spreadsheet, in the (freely available !) “Supplementary information” section, has “per ice-shelf” (area and mass) data from 1997/2000 up to 2021.
If you can access the full paper maybe you can check whether their “Methodology” section is compatible with what your looking for …
No warming of any kind is happening in and around Antarctica as a whole. It’s slowly cooling. Downwelling of cold deep water from the continent’s margins is accelerating.
https://ptolemy2.wordpress.com/2020/09/12/widespread-signals-of-southern-hemisphere-ocean-cooling-as-well-as-the-amoc/
https://ptolemy2.wordpress.com/2022/01/13/cooling-in-the-deep-south/
https://ptolemy2.wordpress.com/2022/05/27/elephant-seals-in-the-ross-sea-what-more-proof-needed-that-mwp-was-real-and-global/
It’s doom again. And not before time. We need a good dose of doom to keep us going.
“If this mechanism that we’ve been studying is active in the real world, …”
But what if it isn’t? Any evidence that the mechanism is real?
“… As of this report, Antarctic sea ice extent persists at record low levels …” (NSIDC, Aug 2022).