Archive for October 9th, 2019

Antarctica Icy Locks Are Going To Give Way: Huge Sea Level Rise

October 9, 2019

Applying Basic Common Sense To Sea Level Rise

When talking Sea Level Rise, one has to think about what it would take to melt Antarctica. The answer? Not much. One has to look at the temperature map. In the temperate zone, surface temperatures lose roughly 20 Centigrades in 30 degrees. That is, at 30 degrees in latitude represent 3,300 kilometers, one loses roughly one degree Centigrade per one hundred fifty kilometer going towards a pole.

The Drake passage separates Patagonia from Antarctica, it’s 1,000 kilometers wide. One expects a drop of 6 C, going across. In Patagonia, glaciers melt as soon as they touch the sea.  

Temperatures are rising faster in Polar regions, probably because of the decreasing albedo (less sunlight is reflected back into space as ice and snow shrink… or become dirtier, or less covered with white snow, but dark ice instead, as is happening so obviously in Greenland, one can see it from planes flying over)   – around the Arctic Peninsula temperatures have risen 2.5 degrees in 50 years (twice the overall rise).

One needs to meditate this map. Its details contains a drastic message: it will not take much to melt Antarctica.

This may not seem a lot but it actually makes a huge difference: it is equivalent of making Antarctica slide more than 425 kilometers towards the tropics (from my little computation above). It’s likely we are going at least one degree C in the next twenty years, overall Earth temp, so that would correspond to a slip northward of 1,000 kilometers… for Antarctica. A casual look at the map show that thousands of kilometers of the icy continent’s margin will then be exposed to what used to be Patagonian conditions… So the glaciers will melt, as soon as they touch the sea. Problem: these are sometimes the mouths of icy basins the bottoms of which are a mile below sea level, and whose total area is probably around half of that of the USA. At least.

The situation with Greenland is paradoxically much safer: most of the world’s largest island is covered by an ice cap the bottom of which is above sea level (there are huge canyons, though, including one going all the way to the center…)

Here is an exchange with a reader:

Erik Frederiksen

Oakland, CA Oct. 8 @Patrice Ayme 

And there’s no need to lose the Ross ice shelf to lose the West Antarctic Ice Sheet.

Thwaites Glacier in the Amundsen Sea Sector drains around a meter of sea level rise equivalent of ice, but when it collapses it will entrain the rest of the ice sheet because it gets hit from behind.

The retreat rate of Thwaites Glacier is below, about 14 km in 19 years in the main flow.  Maybe 70 km until it gets deep and starts a rapid retreat.

https://cloudfront.escholarship.org/dist/prd/content/qt0wz826xt/qt0wz826xt.pdf

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See how much of East Antarctica hugs the Polar circle? That makes it nearly as far from the Pole as Iceland is… (OK, Iceland bathes in the Gulf Stream… However…)

Agreed, Erik. Excellent remark. I was space limited. I have a more robust list of melting horrors on the essay I wrote on my site, developing that theme (of which I have spoken for more than a decade). The Ross shelf melting 400K ago is new science  (2019). The gigantic Twaites glacier has long been known to be very dangerous: as the grounding line retreats, the bottom will fall off, warm water will get below, and the whole thing could collapse in a matter of years. See details in: 

https://thwaitesglacier.org/about/science

There is so much melting there that local gravity is going down, and satellites can measure that.

Even worse: the giant Wilkes and Aurora basin in East Antarctica, four kilometers thick, are in a similar situation, with their bottoms a mile below sea level. Also their outlet are nearly at the Antarctic circle, very north, so potentially very warm. If they melted, sea level would go up 200 feet… “Experts” used to say, not before 5,000 years… But, all well considered, melting very soon is entirely plausible. Actually a French scientific panels of all top French climate experts just predicted a possible seven meter Sea Level rise by 2100…

Erik Frederiksen

Oakland, CA @Patrice Ayme 

In support of that potential for a 7 meter rise by 2100, here is the most respected glaciologist in the US, Richard Alley last year.

“If we don’t change our ways we’re expecting something like 3 feet of sea level rise in the next century, and it could be 2 and it could be 4 and it could be 20.

The chance that we will cross thresholds that commit us to loss of big chunks of West Antarctica and huge sea level rise is real. So when you start doing “Well you’re not sure,” but there’s a chance of really bad things and the uncertainties are mostly on the bad side, could be a little better or a little worse or a lot worse, but we’ll be breaking things.”

https://www.youtube.com/watch?v=l2yclMcDroQ&feature=youtu.be&t=47m4s

 

Once again, it’s very simple: there are icy locks to the icy bottom of Antarctica, which would appear as an archipelago if all sea level ice melted. Those icy locks are at relatively low latitudes, just 1,500 kilometers south of tree covered Patagonia (tree covered at sea level). Those icy locks are extremely sensitive to a temperature rise of a few degrees Centigrades, which we are sure to get. Sure to get there (even if we keep the overall supplementary rise at 2C, we will get at least 4 C there).

So a sea level rise of the order of twenty, thirty meters is guaranteed. Maybe as soon as 2100…

I am not saying it will, I am saying it’s entirely possible.

Like it should have seem entirely possible that there would be an iceberg in the way of the Titanic…

Patrice Ayme