ANSWER 1

Ice in Antarctica is shrinking.

But before we get in to the details, we need to know about the different types of ice in Antarctica. The two main ones are: the ice sheet, which is made up of compressed snow that accumulates over thousands of years; and sea ice, which is frozen sea water.

Because Antarctica is really cold, the snow that falls there usually doesn’t melt. Over millions of years, this snow has built up. As the older snow is buried by new snow, it gets compressed and eventually becomes ice. As the snow keeps falling, this ice gets thicker. The thickest parts are nearly 5 km thick. This ice forms what we call the ice sheet; a massive sheet of ice that blankets most of Antarctica. It holds about 60% of all the freshwater on Earth.

The other main type of ice is called ‘sea ice’. This is a thin layer of frozen ocean water. It’s usually about one to two metres thick, though it can be more than 10 m thick in some places. Most sea ice forms and melts with the seasons. At the summer minimum, it covers an area about half the size of Australia (3 million square kilometres). At the winter maximum it covers an area roughly 2.5 times the size of Australia (19 million square kilometres).

Looking at all the measurements we have, both types of ice are shrinking over the long-term.

This animation by NASA shows the loss of ice from the Antarctic ice sheet that occurred from 2002 until 2025. This is the most recent video available – it takes a while to convert the satellite measurements in to a video. If you look at the last couple of years, you can see that the loss of ice has slowed down. It would be nice if this were the beginning of a recovery, but that is very unlikely. In those years, more snow fell around the edge of Antarctica and this increase in snow fall has offset the melting for now. Predicting the future is hard, but we do not expect that this will last; the Antarctic ice sheet will continue to lose ice as the world warms.

Antarctic sea ice is also declining. Until 2015 it was expanding. This was a perplexing mystery, but we think we’ve solved it; the combination of stronger westerly winds caused by the ozone hole and cold, fresh water from the melting Antarctic ice sheet helped to create a layer of colder, fresher, water at the surface of the ocean that helped shield the sea ice from the warmer water below. This lead to an expansion of Antarctic sea ice. In 2016 it all changed, and Antarctic sea ice shrank rapidly. Since then we’ve seen a reduction in sea ice through out the year (summer lows are lower and winter maximums are also lower).

When trying to understand climate change, it is important to look at all the available data; this helps you see the long-term signal underneath the day-to-day, or year-to-year, variability. Even though both types of ice are shrinking, it is possible to pick small bits of the data that make it look like the ice is expanding. For example, the last couple of years of the NASA video, or the last three years of sea ice data. But that ignores all the ice that was lost in the preceding decades.