2010-10-26 14:57:24Interesting Article from WUWT
Robert Way

robert_way19@hotmail...
142.162.11.6
Hello all,
I thought this was interesting

http://wattsupwiththat.com/2010/10/25/antarctic-ocean-the-big-kahuna-of-glacial-period-carbon-sinks/#more-26963

Its a new study and it helps us understand where the carbon went during the glacials....
2010-10-26 15:24:08Very interesting
John Cook

john@skepticalscience...
124.186.160.198

Not so interesting is the bile spewed forth in the WUWT comments but I can only read the first batch before averting my eyes.

This brings up a topic I've been meaning to nail down for ages. My understanding of the deglaciation process has always been as follows:

  1. Orbital changes mean warmer springs in Antarctica, melting ice
  2. Warming Southern Ocean leads to outgassing of CO2 after ~ 800 years (this new paper illuminates this process further)
  3. CO2 amplifies initial warming (positive feedback)
  4. CO2 also mixes through the atmosphere, spreading the warming north to the equator and Northern Hemisphere. Consequently, ocean cores at the equator find warming and CO2 rise synchronous. I seem to recall the Greenland ice cores also have CO2 changes and warming also synchonous but I'm not 100% certain of that.

So basically, deglaciation starts in the south then spreads north. But I've heard a few people (including some distinguished scientists) say deglaciation is initiated by insolation changes in the Northern Hemisphere. So can anyone confirm whether I've got this right or not?

2010-10-27 02:53:18Comment
Robert Way

robert_way19@hotmail...
134.153.163.105
My understanding was that it was in fact initiated in the North through changes in insolation. That's what I took from Ruddiman's book at least... that the northern hemisphere insolation changes initiated the melting of the ice sheets and that the insolation changes were also warming the oceans which caused CO2 outgasing plus any CO2 locked in the ice. Plus as the ice sheets start melting they get lower which causes them to be at a lower elevation and therefore melt further because temperature decreases with height. Finally when the ice sheets melt enough their effect on climate is minimized (an important thing to consider is how much ice sheets affect climate) and they start being controlled by the climate which will by this point be dominated by higher insolation and GHGs... that's just a general thought I have. Add in the ice albedo effect and stuff..
2010-10-27 04:35:10
Riccardo

riccardoreitano@tiscali...
93.147.82.79

There no single accepted explanation for the mechanism. The timing of the various phases in the Arctic and Antarctic is too uncertain.

This new paper deals with the storage of CO2 during the ice ages and although there is a consensus on the role of the Antarctic Ocean, apparently this is the first direct evidence on where the CO2 came from. This paper on ocean circulation during the glacial cycles may be of interest. A while ago I started writing a post on it for an italian blog, but it was too technical and I put it aside. Now that the ideas have "sedimented" for a few months, I could try again.

2010-10-28 06:49:50Just added the peer-reviewed paper to the database
John Cook

john@skepticalscience...
124.186.160.198

Here's the paper: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo987.html

So does this strengthen the evidence that deglaciation begins in the south, not the north?

2010-10-28 08:10:20
Riccardo

riccardoreitano@tiscali...
93.147.82.83
I do not have access to NatGeo. From the abstract and the news at UFL, it says nothing on the deglaciation starting in the north or the south. In both cases, it is the upwelling in the southern ocean that controls the release CO2.