Antarctic sea-ice growth in Nature Geoscience

There’s a new paper on Antarctic sea-ice in Nature Geoscience so I thought it might be a good time to have a quick look at how this story has developed recently. (The short version: the small increase in Antarctic sea ice is most likely a result of a complicated coruination of: density changes in the surface layer of the Southern Ocean (a result of temperature and salinity changes), which stops warm deep water reaching the surface and melting the sea ice; changing wind patterns (partially a result of ozone depletion) that leads to ice drift increase and increased sea ice extent; and melting from the bottom of ice shelves adding cool water to the ocean surface layer that further reduces deeper warm water reaching the surface and reducing sea ice melt.)

Firstly, though, why does anyone care about Antarctic sea-ice? Well, it’s been increasing a little recently. This isn’t quite what you’d expect in a changing climate where the change is being driven by an increase in energy being retained in the system by an increase in greenhouse gases in the atmosphere.

In contrast, we often hear about sea-ice loss in the Arctic, which is often linked with climate change. However, if we compare the Arctic loss with the Antarctic gain you can see that one is clearly more of an issue than the other:

Sea ice extent for the month when its at its minimum (i.e. the end of local summer) Source: James Hansen

Nonetheless, its still interesting to think about why Antarctic sea ice is increasing.

The best theory around five years ago (Zhang 2007) was that the surface layer of the Southern Ocean was changing density and that this stops the warmer water below getting to the surface and melting the sea ice. The change in density itself is driven by a couple of factors, such as increased evaporation from warmer Southern waters that increases rainfall in the seas around Antarctica and freshens the water and changes in salinity driven by the sea ice changes themselves (sea ice rejects salt as it forms).

Last year, the big advance was the use of satellite observations to show that changing wind patterns in the Southern Hemisphere (which I’ve written about here) were driving the sea ice extent increase via increased ice drift (Holland and Kwok 2012).

The new paper (Bintanja et al. 2013) shows that melting from the bottom of ice shelves – where the Antarctic glaciers flow out over the ocean – produces a layer of cold water that stops warmer water below reaching the surface and slowing sea-ice growth. Although,  Holland (of Holland and Kwok) isn’t convinced that the experiments are a good demonstration of the mechanism.

So this is quite a complicated situation to understand. However, the ocean and air temperatures around Antarctica aren’t decreasing so that isn’t the reason for the sea ice increase, even though it may seem like the most obvious. To find out the real reason you need to dig a little deeper.

In the immortal words of Father Jack Hackett…

“Award! Award! Award!”

To be more specific: I found out a few weeks ago that I’ve been awarded the Royal Meteorological Society‘s (RMetS) Michael Hunt Award, which is “for excellence in increasing the understanding of meteorology or its applied disciplines among members of the general public”. Get me!

And don’t worry, I’m sure it wasn’t given to me for this blog, which has only rarely been updated in the last year or so – I blame having kids and my change from postdoc to lecturer, which have occurred since I started blogging. I also do other outreach/public engagement things like school visits, Skeptics in the Pub talks, science festival events and wotnot. It’s usually a lot of fun and to get an award for doing it is great!

Oddly enough, though, my previous post on this blog was slightly critical of a recent RMetS Meeting on climate change communication; I’m glad that they didn’t hold that against me!

So, to continue that theme, I thought I’d make another couple of points about RMetS and how it communicates with the outside world…

Most of RMetS’ effort goes into their meetings and publications, which are excellent for academics but what about everyone else?

I know that they run events in schools and at science festivals, which is great.

The previous RMetS Chief Exec had a blog for a while (it was quite fun, I enjoyed the posts about his watch) and it’s now become a more general society blog but I think that there’s still room in the weather and climate blogosphere (ugh, never though I use that word seriously) for coverage of big issues. For example, The Carbon Brief has only been going since 2011ish and it has become an excellent resource. Whilst I suspect that RMetS want to keep it a bit more light-hearted, there’s still some low hanging fruit here that I’m sure RMetS could grab. Even the columns in the (recently departed) “theWeather” magazine would have made excellent blog posts that I’m sure would get widely read but they were never (as far as I know) made available online.

I loved “theWeather” magazine and it even won an award or two but, given the way that publishing and reading habits are changing, perhaps it wasn’t the time to launch a subscription only print magazine.

I just hope that the RMetS can find more of a place online where most people do their communicating these days, particularly in terms of climate change. (Whether that’s a good thing is another matter!)

What I would do is set up a network of early career meteorologists, climatologists, oceanographers etc. to run a collaborative blog on the RMetS website. One of the most interesting and exciting things I’ve done outreach-wise was the EPSRC-funded (now EPSRC-non-funded) NOISEmakers ambassadors scheme. It was great meeting up with scientists that you wouldn’t normally work with and discuss ideas (perhaps a little bit like the JASONs but not as serious!) In my case, this led to writing some nice general audience pieces, starting my own blog, networking with other people about communication and even working on papers and research proposals with people I met through NOISEmakers.

Finally, I also thought I should find out who Michael Hunt was and found this clip on youtube, you can see Hunt at 3.39, he’s got a good look!