The Southern Ocean is cooling

As I wrote previously:

To a mind in denial, increasing sea ice at the Antarctic suggests that the world is not warming but cooling.

Or at least that the Antarctic is cooling...

The latest meme to spread round the denial blogosphere is a claim that the southern ocean is cooling.

So that extra ice at the Antarctic really is because of cooling.

Paul Homewood becomes my latest global warming bozo for this stupid claim.

He reproduces a graph from Bob Tisdale of Southern Ocean sea surface temperature which shows a decline over the last eight years or so:

But the sea surface is not the ocean.

The Southern Ocean has been getting a lot warmer at depth over the same period:

Graphic adapted from this one shown in full in my previous post.

What actually seems to be happening is an increasing stratification of heat: colder surface, warmer depth.

As I discussed in a previous post, it is a paradox of increased Antarctic sea ice formation that it is happening in a warming Southern ocean.

This paradox was discussed at Skeptical Science by John Cook, who makes the following observation, based on a peer-reviewed scientific study:

The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more stratified and mix less. Less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted (Zhang 2007).

An increase in temperature stratification of the Southern Ocean would seem to confirm the wisdom of John Cook's post.

Paul Homewood, however, uses the decrease in Southern Ocean temperature to ridicule John Cook. An error, and a typical piece of denier personalisation of the argument (Al Gore is fat), which Skeptical Science has identified before.

So, a double bozo award to Paul Homewood. Parp! Parp!

NB: the complexities of the issue are discussed further at Hot Whopper.