HomeLatest ThreadsGreatest ThreadsForums & GroupsMy SubscriptionsMy Posts
DU Home » Latest Threads » Forums & Groups » Topics » Environment & Energy » Environment & Energy (Group) » Nature: Antarctica Is Mel...
Introducing Discussionist: A new forum by the creators of DU

Fri Apr 27, 2012, 10:27 PM

Nature: Antarctica Is Melting From Below

Nature: Antarctica Is Melting From Below, Which ‘May Already Have Triggered A Period of Unstable Glacier Retreat’
By Climate Guest Blogger on Apr 27, 2012 at 12:29 pm

We knew that “deep ocean heat is rapidly melting Antarctic ice.” And we knew that these warm ocean currents melting Antarctica were so intense that, seawater appears to “boil on the surface like a kettle on the stove.”


We also knew that the the West Antarctic ice sheet (WAIS) is inherently far less stable than the Greenland ice sheet because most of it is grounded far below sea level (see below). And JPL has told us that polar ice sheet mass loss is speeding up and is on pace for 1 foot sea level rise by 2050.

Now a new study using NASA satellite data finds the WAIS in particular is “being eaten away from below by warm water” as the AP put it, which “suggests that future sea levels could rise faster than many scientists have been predicting.”
The Nature study itself, “Antarctic ice-sheet loss driven by basal melting of ice shelves,” concludes:

We find that ocean-driven ice-shelf thinning is in all cases coupled with dynamic thinning of grounded tributary glaciers that together account for about 40% of Antarctic discharge and the majority of Antarctic ice-sheet mass loss. In agreement with recent model predictions, we conclude that it is reduced buttressing from the thinning ice shelves that is driving glacier acceleration and dynamic thinning. This implies that the most profound contemporary changes to the ice sheets and their contribution to sea level rise can be attributed to ocean thermal forcing that is sustained over decades and may already have triggered a period of unstable glacier retreat.


This ought to be doubly worrisome since ...


http://thinkprogress.org/climate/2012/04/27/471922/nature-antarctica-melting-from-below-may-already-have-triggered-a-period-of-unstable-glacier-retreat/

13 replies, 1980 views

Reply to this thread

Back to top Alert abuse

Always highlight: 10 newest replies | Replies posted after I mark a forum
Replies to this discussion thread
Arrow 13 replies Author Time Post
Reply Nature: Antarctica Is Melting From Below (Original post)
kristopher Apr 2012 OP
longship Apr 2012 #1
enough Apr 2012 #2
Demeter Apr 2012 #3
kristopher Apr 2012 #4
happyslug Apr 2012 #5
Demeter Apr 2012 #6
kristopher Apr 2012 #7
happyslug Apr 2012 #8
kristopher Apr 2012 #9
happyslug May 2012 #10
kristopher May 2012 #12
happyslug May 2012 #11
LineLineLineLineLineNew Reply .
kristopher May 2012 #13

Response to kristopher (Original post)

Sat Apr 28, 2012, 01:47 AM

1. Important

R&K

Reply to this post

Back to top Alert abuse Link here Permalink


Response to kristopher (Original post)

Sat Apr 28, 2012, 08:58 AM

2. k&r (nt)

Reply to this post

Back to top Alert abuse Link here Permalink


Response to kristopher (Original post)

Sun Apr 29, 2012, 10:54 AM

3. And the Source of this Heat?

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Demeter (Reply #3)

Sun Apr 29, 2012, 02:16 PM

4. Generally speaking...

The heat being discussed that is of concern to us - the larger topic that provides a reason for writing the article - is anthropogenic global warming.

Or are you asking about the transport mechanism that caused the heat to be where it is?

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Demeter (Reply #3)

Mon Apr 30, 2012, 01:24 AM

5. Two sources, one not a problem, the other the major cause

The report mentioned "Boiling water", that can only be caused by a Volcano. Antarctica has several volcano and one theory for the existence of under ice lakes of water is that the water is kept warm by volcano action (i.e. enough heat is provided via some volcano to keep the lake from freezing). Please note it is possible for the lake to never have frozen in the first place, just iced over, but just pointing out the volcano theory and that the Volcano is the best explanation for any boiling water reported in Antarctica.

On the other hand, the vast majority of the heat is being provided by the ocean. The Southern Ocean is a circular rotation of currents that keeps most of Antarctic isolated from the heat in the Indian, Pacific and Atlantic oceans. On a map the Southern Ocean looks like just that part of those three oceans next to Antarctica, but do to the circular rotation of the currents around Antarctica that is NOT the case. The Southern Ocean acts as a barrier to movement of water from those three oceans to the coasts of Antarctica.

The problem with the Southern Ocean is that it is directly connected to the Indian, Pacific and Atlantic Oceans, Thus some heat does get exchanged between those three oceans and the Southern Ocean AND thus Antarctica. Worse the Southern Ocean is at its weakest south of South America, where heat from the Pacific and the Atlantic can get close to Antarctica AND cold water can escape (El Nino is an example of such a movement of Cold water from the Southern Ocean to the Pacific, which also means warmer water from elsewhere entered the Southern Ocean, warming up the Southern Ocean).

A further problem is the West Antarctic Ice Sheet (WAIS) is directly south of South America. Drake Straits is the Closest Antarctica gets to another Continent. Drake Straits is ocean deep, but shadow compared to the rest of the Southern Ocean (In fact do to the Narrowest and shadowiest of Drake Strait, the "Ocean Conveyor belt, goes from the Caribbean Sea to Iceland, where it loses its heat, but retains its salt, then flows south, joined in from cold water from the Mediterranean, then flows south to the Southern Ocean, then east through the Indian ocean to the Pacific, where the salt is lost and the water rises and return as a surface current to the Caribbean).

More on the Ocean Conveyor belt:
http://oceanservice.noaa.gov/facts/conveyor.html
http://oceanmotion.org/html/background/ocean-conveyor-belt.htm
http://www.enviroliteracy.org/article.php/545.html
http://www.sciencedaily.com/releases/2010/06/100618102646.htm

Please note it takes about 1000 years for water to go through this system, but it tends to keep most of the world at the same temperature.

You also have to understand that West Antarctic is NOT one piece of land but a series of interconnected islands, connected by the West Antarctic Ice Sheet (WAIS). Here is a map of Antarctica without ice, notice on the Left, which is West Antarctica mostly islands:


http://en.wikipedia.org/wiki/Antarctica

More maps of Antarctica:
http://commons.wikimedia.org/wiki/Atlas_of_Antarctica

More on the West Antarctic Ice Sheet:
http://en.wikipedia.org/wiki/West_Antarctic_Ice_Sheet
http://earthsky.org/earth/sophie-nowicki-on-weak-underbelly-of-west-antarctic-ice-sheet
http://www.sciencedaily.com/releases/2010/01/100116103350.htm
http://thinkprogress.org/climate/2009/02/05/203656/antarctic-ice-sheet-collapse-even-more-catastrophic-for-us-coasts/
http://science.nasa.gov/science-news/science-at-nasa/2000/ast27dec_1/

More on the Antarctic Circumpolar Current:
http://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current
http://phys.org/news191483678.html
http://www.antarctica.gov.au/about-us/publications/australian-antarctic-magazine/2001-2005/issue-4-spring-2002/the-southern-oceans-global-reach

El Nino tied in with the Antarctic Circumpolar Current:
http://www.spacedaily.com/news/pacific-01b.html

Reply to this post

Back to top Alert abuse Link here Permalink


Response to happyslug (Reply #5)

Mon Apr 30, 2012, 06:50 AM

6. Thank you, that was very helpful and informative

Reply to this post

Back to top Alert abuse Link here Permalink


Response to happyslug (Reply #5)

Mon Apr 30, 2012, 02:23 PM

7. I'm afraid this has nothing to do with a volcano.

The researcher being quoted was referring to the strength of the upwelling current and the force of this newly identified (in 2009), localized convection effect.
One day, near the southern edge of Pine Island Glacier Ice Shelf, the researchers directly observed the strength of the melting process as they watched frigid, seawater appear to boil on the surface like a kettle on the stove. To Jacobs, it suggested that deep water, buoyed by added fresh glacial melt, was rising to the surface in a process called upwelling. Jacobs had never witnessed upwelling first hand, but colleagues had described something similar in the fjords of Greenland, where summer runoff and melting glacier fronts can also drive buoyant plumes to the sea surface.



http://phys.org/news/2011-06-ocean-currents-antarctic-ice.html

Reply to this post

Back to top Alert abuse Link here Permalink


Response to kristopher (Reply #7)

Mon Apr 30, 2012, 04:28 PM

8. There are Volcanos in Antarctica and there are a factor

Volcanoes is the best explanation for seeing "Boiling water" in Antarctica mentioned in the Article, but as I pointed out the volcanoes are at best a minor addition to the warming of Antarctica.

The real problem is the movement of heat from the Pacific, Atlantic and Indian Ocean to the Southern Ocean and then to the Antarctic ice Sheets (via the Surrounding Ice Shelves). The big problem is the increase in water temperature from near freezing to above freezing. The change from solid to liquid takes a good bit of heat, more then just dropping the temperature below the point where something change from solid to liquid.

On the other hand we are NOT talking about temperature of the water being that much higher then the freezing point of water. 33 degree is enough, the problem is to hold temperature at 33 for any length of time requires even more heat input. Up till recently, no such long term temperature increase was noted in the Southern Ocean. That has changed and that is the main concern when it comes to the West Antarctic Ice Sheet.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to happyslug (Reply #8)

Mon Apr 30, 2012, 05:09 PM

9. The context of the quote shows it is not about volcanism

That is simply a statement of fact. With that metaphor the researcher was pointing out the energetic nature of the process that is accelerating the melting process of the shelf. Volcanic activity has nothing to do with it.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to kristopher (Reply #9)

Tue May 1, 2012, 12:42 AM

10. The heat hitting Antarctica is NOT enough to cause water to boil

That requires at least 100 degrees Centigrade (212 Fahrenheit). Thus the only cause for such boiling has to be heat generated locally, and that means volcano or other lava source.

All I was pointing out was the heat hitting Antarctica is NOT enough to produce boiling water. At the same time, the heat that is reaching Antarctica can cause the ice cap to melt (and in the case of the West Antarctic Ice Sheet melt so they ceased being grounded to the floor of the ocean and float).

If the whole West Antarctic Ice Sheet should melt enough to float, world wide sea level will increase at least five meters (or about 15-18 feet). To get that all we need is temperatures ABOVE Freezing and there is more and more evidence that is what is happening in the ice Shelves and to a degree the ice Sheets. 33 degree Fahrenheit water is enough to cause that to happen, you do NOT need 212 degree water to melt ice.

My point is the volcanoes are a factor, but the main factor, as I pointed out in my previous thread, was the exchange of warmer water from the Pacific, Atlantic and Indian Oceans. When it comes to boiling water, the best explanation is a volcano, but the main threat to the Antarctic, as I pointed out in my previous thread, is the gradual warming of the Ice Sheets.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to happyslug (Reply #10)

Tue May 1, 2012, 01:24 AM

12. The context of the quote shows it is not about volcanism

That is simply a statement of fact. With that metaphor the researcher was pointing out the energetic nature of the process that is accelerating the melting process of the shelf. Volcanic activity has nothing to do with it.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to kristopher (Reply #7)

Tue May 1, 2012, 12:49 AM

11. That is NOT boiling water, but upswelling of still cold water

The article used the term "Boiling" and I addressed it. You do have boiling water in the Antarctic do to the Volcanoes, but what is being describe is NOT something boiling but water being pushed upward as the ice over top of it sinks for various reasons. To call it boiling is at best inaccurate and worse misleading. I have seen such swelling (On a small scale on the local creeks and streams when you have ice over unfrozen water and the ice breaks up AND some of the water is pushed out of the way of the Ice). The ice swelling does NOT look like boiling water, it looks more like water escaping from a hose with air mixed in with the water.

Reply to this post

Back to top Alert abuse Link here Permalink


Reply to this thread