Friday, April 29, 2016

The Ghost-Water Constant - 7

Fig. 1 Nansen, East Antarctica (not Greenland)
In times past I considered software modelling of the climate change projection sort.

Specifically, the solution sought was how do scientists, whether citizen scientists or professional scientists, approach the issue of future sea level change (SLC).

The factor that best addressed the problem of projecting future SLC was a robust understanding of acceleration of ice sheet mass loss (The Question Is: How Much Acceleration Is Involved In SLR?, 2, 3, 4, 5, 6, 7, 8, 9).

The technique used to communicate the issue of acceleration to laypersons by professional scientists was the concept of "doubling":
The increasing Greenland mass loss ... can be fit just as well by exponentially increasing annual mass loss, a behavior that Hansen (2005, 2007) argues could occur because of multiple amplifying feedbacks as an ice sheet begins to disintegrate. A 10-year doubling time would lead to 1 meter sea level rise by 2067 ... 2045 ... for 5-year doubling time and 2055 ... for a 7-year doubling time.
(The Evolution of Models - 7). Let me add that the concept there is a composite with includes Greenland, Antarctica, and land based glaciers that are not attached to ice sheets.

That said, remember that those three sources for increasing ocean volume by melt or by calving, can have an acceleration of ice mass loss individually or collectively.

For example, notice this about one of them:
"Mass loss from the Greenland ice sheet has quadrupled over the last decade due to a combination of increased surface runoff from the ice-sheet periphery, increased frontal ablation (ice discharge and submarine melting) and widespread speed up at tidewater glacier termini ... Concentrated at the ice-sheet margins ... this mass loss impacts both the ice and ocean by changing the hypsometry of the glacier ... increasing submarine melt rates ... and altering the salinity, temperature and circulation of fjord waters ... The
Fig. 2  Greenland
increased ice flow speed at tidewater glaciers is thought to be caused by a number of factors including increased basal sliding due to the increase in meltwater runoff ... changes in back stress as mélange composition and extent fluctuate ... as well as submarine melting at the terminus ... Surface and subglacial meltwater runoff is important in tidewater glacier systems. Runoff is predicted to increase as Greenland's climate continues to warm ... and consequently is expected to continue influencing fjord circulation and submarine melting by enhancing the entrainment of warm ocean waters ... As fresh meltwater enters the fjord at depth, it mixes with ambient ocean water as it moves along the terminus to the surface, concurrently melting the terminus face ... altering the geometry, and, potentially, the calving style ... Therefore, understanding subglacial water transport is critical in identifying meltwater controls on tidewater outlet glacier dynamics and freshwater delivery to the ocean. Furthermore, incorporating these drainage processes into coupled ice/climate, ice/ocean and ice/climate/ocean models will advance our understanding of the long-term influence of these processes on glacier stability.
"
(Annals of Glaciology, emphasis added, 4/28/16). Let's focus on the acceleration value which those researchers used: "quadrupled over the past decade."

That value is the mathematical equivalent of "doubled over the past five years" or in other words a "5-year doubling time."

That happens to be an acceleration rate addressed in the quote of Dr. James Hansen above:
A 10-year doubling time would lead to 1 meter sea level rise by 2067 ... 2045 ... for 5-year doubling time and 2055 ... for a 7-year doubling time.
(The Evolution of Models - 7, emphasis added). It is not clear whether that value can also be applied to Antarctica and mountain glaciers.

There is evidence that those other two areas besides Greenland are also having acceleration of mass loss (Nansen, East Antarctica, Belopolskijbreen, Svalbard, Pacific Northwest Glaciers).

There has been a debate for decades that held East Antarctica to be stable even if West Antarctica was not, but as Fig. 1 shows, that is changing (cf. this).

The acceleration of ice sheet and glacial melt and/or calving does not directly involve ghost water (The Ghost-Water Constant, 2, 3, 4, 5).

What does change the location of ghost-water is the loss of ice sheet gravity (The Gravity of Sea Level Change, 2, 3, 4).

Acceleration of the loss of ice sheet gravity means that the water along the coast, out to the hinge line (The Evolution and Migration of Sea Level Hinge Points) will be relocated toward the equator at an accelerating rate (ibid).

Which means that sea level fall (SLF) near the coast will take place as sea level rise (SLR) takes place on the other side of the hinge line (Proof of Concept , 2, 3, 4, 5, 6, 7, 8).

The bottom line is that SLC will be "worse than previously thought," and we may even see some scientific papers saying "thermal expansion has tripled."

Be sure to ignore that myth if "further adjustments" come down the pike  (On The Evolution of Sea Level Change - 2).

That is, until they see ghost water hidden in plain sight right before their eyes:
"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.
...
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."
(The Ghost-Water Constant - 6, cf. this). What is relevant to that OMG research is the quantity of ghost water which ice mass/gravity loss releases to be relocated toward the Equator (The Ghost-Water Constant - 4).

It has been that way for a long time:
"37. In discussing the disturbance of the sea level attributable to the ice mass of the glacial epoch, it will be of interest to estimate the effect of the rearranged free water [i.e. relocated ghost-water]. For this purpose we may extend the second term of the third member of equation (66) so as to make it assign the effect of the rearranged water [i.e. relocated ghost-water] when the mass is of variable as well as uniform thickness."
(On the Form and Position of the Sea Level, by Robert Simpson Woodward (1888), p. 140, p. 56 PDF; cf. this video).

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





4 comments:

  1. Lies, distortion and misinformation abound in the MSM to continue business as usual. It's not like anyone can do anything about any of it at this point, it's like trying to stop or steer a runaway train.

    Tom

    ReplyDelete
  2. How about this?

    40 Pct. of Greenland ice sheet protected from melting, study says

    http://latino.foxnews.com/latino/lifestyle/2016/04/30/40-pct-greenland-ice-sheet-protected-from-melting-study-says/

    At least 40 percent of Greenland's ice sheet in the Arctic is protected from melting due to a new phenomenon detected by a group of U.S. scientists, according to a study published in Science Advances magazine.

    The study, led by scientists from universities in Chicago, Colorado and Oregon, also had international contributions from France, Denmark and Switzerland.

    Despite the rapid thaw in the Arctic, 40 percent of Greenland's ice sheet "rarely experiences surface melting," the report says.

    The reason is a process scientists have detected for the first time, by which nature "recycles" water to protect the ice sheets from global warming.

    The phenomenon of "recycling," as scientists call it, is based on "sublimated moisture," the process by which meltwater is recondensed into fog particles, "which returns the moisture back to the surface through gravitational settling."

    By means of sublimation, the constant humidity of that area is reintegrated into the ice mass, protecting it from losing volume.

    [note the source]

    Tom

    ReplyDelete
    Replies
    1. I had to look up the paper myself, since the Fox News Science Journal gave an erroneous opinion, but no link.

      If you are going to post links, don't waste people's time by linking to Fox Snooze, link to the paper.

      The paper says:

      "The rate of ice accumulation on the Greenland Ice Sheet (GrIS) emerges from a balance between mass loss from coastal calving associated with melting and sublimation and additions from precipitation and condensation. In coastal regions, the former [ice mass loss] now significantly exceeds the latter [fog "and stuff like that Wally - The Beaver"], leading to a receding ice edge and a contribution to rising sea levels." (Surface-atmosphere decoupling limits accumulation at Summit, Greenland).

      That is interpreted by the cognitively challenged commentariat (The Warming Science Commentariat) to mean 40% of Greenland will not melt, which is not what the paper says.

      If it did say that it would be rubbish based only on their methods at one place in Greenland, not to mention reality.

      The Dredd Blog post we are commenting under links directly to a piece dated 4/28/2016 which says "Mass loss from the Greenland ice sheet has quadrupled over the last decade ..." (see the link 'graciously provided' in the post above the commentariat).

      For those who are cognitively challenged, if your bank account is going down four times faster than what your paycheck puts into the account, you are not experiencing "a balance between" incoming and outgoing.

      Greenland is not making ice by losing ice ... at an increasing, alarming rate of acceleration.

      For you Trump, Cruz, and Ryan fans at Fox Snooze, take note that Greenland has an annual ice mass deficit that puts the government spending deficit to shame (so why create a myth to celebrate a deficit?)

      Anyway, the paper goes on to mention "The exchange of water between the ice sheet and the atmosphere ..." which is a grossly mistaken focus.

      Clue: focus on the exchange of "water between the ice sheet and the ..." [wait for it here it comes, drum roll .....] ocean.

      The predicament posed by ice sheet mass loss is not about a air level, rather, it is about sea level (the greatest climate change threat to civilization).

      They had no "Conclusion" section, so let me conclude by saying that the conditions they describe are de minimus, and those conditions will fade into further insignificance as the ice sheet disintegrates.

      Delete