Ozone depletion and Antarctic Sea Ice extent

Source: Turner et al 2009

This blog is a departure from the processes described last week into the modelling and measuring of indirect impacts that ozone depletion can have on the environment.

A study by Turner et al 2009, brought to my attention last week in the polar ecosystems lecture, suggests a link between stratospheric ozone depletion and sea ice extent (SIE) in regions of the Antarctic. Using satellite data it was found that there has been a statistically significant increase of annual mean SIE by 0.97% per decade since the 1970s. Two key areas of interest emerged in which SIE appeared to be declining (-6.63%/decade) over the Amundsen Sea and increasing over the Ross Sea (as shown on figure two).

In order to differentiate the anthropogenic forcing from the natural variability the researchers created 2 different models. One used pre industrial ozone levels and the other used ozone levels recorded from the year 2000.

Figure 3d from Turner et al 2009

When the two models were compared spatially over a map of the Antarctic (figure 3d) it clearly showed a “trough” of low pressure over the Amundsen Sea, to the west of the Ross Sea. This area of low pressure creates a cyclone which enhances the strength of winds flowing from the Ross Ice Shelf towards the coast and in turn maintains lower temperatures.  These combine to produce improved conditions for sea ice production, thus SIE is found to increase in the Ross Sea.

The authors of the research raise important issues on the projections of SIE in Antarctica. With particular reference to the estimated ‘recovery’ of the ozone hole by the mid twenty first century along with ever increasing green house gases. It is proposed that the observed increase in SIE over the previous decades will therefore be reversed.

It is interesting to think that this feedback loop from ozone depletion can actually have such a profound effect on SIE in Antarctica and I look forward to investigating further contrasting examples of feedbacks associated with ozone depletion.