Low sea ice around Antarctica
Climate change and Emperor penguins
At this time of year, Antarctica is in the depths of winter, yet the continent is surrounded by much less sea ice than scientists predict. In July 2023, sea ice averaged 13.5 million square kilometres, the lowest extent observed for the southern hemisphere winter since continuous satellite records began in 1978. (See photo).
Satellite image (7th August 2023)
The yellow line shows the median sea ice extent for July (1981 to 2010).
Photo: NASA
Antarctic sea ice follows a seasonal trend, and each year, 15 million square kilometres of ice grows and melts. Ice growth this year has been very slow. In July, sea ice covered about 2 million square kilometres less than the 1981 to 2010 average.
The satellite image shows ice extent was low nearly everywhere around the continent, but particularly in the Weddell Sea, Ross Sea, and Bellingshausen Sea. The Amundsen Sea was the only area with above-average extent.
According to the National Snow and Ice Data Centre (NSIDC), the average sea ice extent in July 2023 was 1.5 million square kilometres lower than the previous record-low in 2022. The chart below shows the daily sea ice extent up to August 7, 2023 (red) compared to the 2022 record low (orange) and the average extent from 1981 to 2010 (blue). [Figure 1.]
Figure 1. Antarctic Daily Sea Ice extent (km2 millions)
Source: NSIDC
This record-low extent in 2023 is a continuation of a downward trend in Antarctic Sea ice that started following a high in 2014. Up to 2014, ice surrounding the continent was increasing slightly at the rate of 1% per decade. Since then, it has declined sharply with lows in 2017, 2022, and now 2023.
Furthermore, recent research has found that the rate of sea ice decline around Antarctica between 2014 and 2017 far exceeded the declines seen in Arctic Sea ice in recent years and was a much greater decline than anything observed previously.
Some scientists speculate that the sudden decline in Antarctic sea ice means it is undergoing a regime shift towards a generally lower ice extent. Some have suggested that changing warmer ocean conditions, due to climate change, are a possible driver. This ocean heat could be playing a stronger role in limiting autumn and winter ice growth and enhancing spring and summer melting.
The loss of sea ice around Antarctica is linked to the dramatic fall in the number of Emperor penguin chicks in the region.
A short video on this issue from RTE can be viewed here:
'Unprecedented' breeding failure of Emperor penguins in Antarctica - YouTube
A longer video from the BBC can be viewed here:
Thousands of emperor penguins killed in the Antarctic - BBC News - YouTube