Arctic sea ice over one year

As 2014 draws to a close, what were the key features of the Arctic climate this year? Today let’s look at the sea ice coverage. The US National Snow and Ice Data Centre has a monthly running commentary on ice cover on their website, and in general 2014 has been “extremely ordinary”, by which they mean that sea ice grew and shrank at roughly the rates of the last few years. Ice cover was not as low as 2012, the record-breaking year for sea ice retreat, instead it was pretty average for recent times. Remember that this is still way down on the long-term average.

Monthly Arctic sea ice cover for the last few years (NSIDC)
Monthly Arctic sea ice cover for the last few years (NSIDC)

Using their monthly data, here is an animation of the sea ice changes over the last 12 months. It’s a reminder of just how dynamic the Arctic is. Sea ice cover is important for a number of reasons. First of all, the white colour reflects sunlight that shines onto the ice surface during the summer. Reflecting sunlight back into space means that it does not stay around to warm our planet, so having a decent covering of ice helps to regulate temperatures. As the summer sea ice cover has decreased in recent years, the amount of sunlight reflected back into space has decreased, meaning that there is a positive temperature feedback at work here.

animsm
Arctic sea ice cover over the last year

Sea ice cover is also important for the Arctic Ocean’s biological cycle. Many plankton require sunlight for photosynthesis, so the retreat of sea ice during the spring and summer causes a bloom in biological productivity in the surface ocean which feeds down the food chain, supporting large numbers of fish and whales. As organic geochemists, we can see this plankton bloom by looking in the ocean sediments biomarkers. There are specific chemicals that are produced by marine organisms that can be used to track the productivity, and it seems that there is a direct link between the ice-free areas and the highest amount of biological activity.

State of the climate – a 2013 snapshot

NASA measurements
2013 Temperature Anomaly

In January, NASA and NOAA (the US National Oceanic and Atmospheric Administration) released a joint statement on the temperature and climate patterns seen in 2013. Their short presentation (PDF) gives a summary of last year’s data in relation to long-term trends and averages. Of particular note for Arctic scientists is the relatively cool high-latitude temperatures in mid-summer. These lead to less summer sea-ice melting compared to the previous year’s record-breaking┬áminimum, causing nonsensical headlines from the usual suspects that the world was cooling down. As slides 2,3 and 8 show, 2013 was one of the warmest years on record, while slide 11 shows that Arctic sea ice was still far below average last year.

Polar ice cover graphs
Polar ice cover through time