When scientists talk about ice and climate change, it’s often about how quickly it’s disappearing. So recentnews storiesabout Antarctic sea ice growing may come as a surprise.

在安塔尔周围的海洋的冰ctica is indeed increasing, but this is only part of what’s going on in the Antarctic as a whole. We’ve put together six things you should know about climate change and Antarctic ice.

1. Antarctic waters are warming faster than the global average

Along with therest of the world, the Antarctic is warming up. The Southern Ocean, which surrounds the continent of Antarctica, has been warming faster than the rest of the world’s oceans since the 1950s, at a rate of0.17 degrees Celsiuscompared to a global average of 0.1 degrees. The increased rate of warming is mainly due to the waylarge weather systemstransport heat to the poles.

2. Despite rapid warming, there’s more Antarctic sea ice

Despite rapidly warming water, the amount of ice that floats on the Southern Ocean around Antarctica – known as sea ice – is slightly increasing. On 26 September 2012, the USNational Snow and Ice Data Centre (NSIDC)confirmed that Antarctic sea ice reached arecord extent– a measure of sea ice cover – of 19.44 million square kilometres.

3. Scientists believe the wind is driving sea ice increase

New researchreleased in the journal Nature Geoscience yesterday tracked Antarctic sea ice between 1992 and 2010. It suggests that trends in sea ice are closely linked to local winds. The main driver of the overall increase in sea ice is the changing strength of cold winds, which blow ice away from the coast and allow the water in between to freeze. (Although there are some differences across the continent.)

The new study says that the wind change may be down to natural climate variability, but that there is evidence that the southern hemisphereozone holealso plays a part.

4. Most of the ice in Antarctica is on land

The new research talks about the ice floating on top of the Southern Ocean. But most of the ice in the Antarctic is actually contained within a vast expanse that covers the land mass and extends into the surrounding ocean – known as the Antarctic ice sheet.

Measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite since 2002 have shown that the mass of the Antarctic ice sheet isdecreasingat an average rate of 100 cubic kilometres every year – the size of a small UK city. Scientists have compared different techniques for measuring this ice loss and foundgood agreement between them.
下面的图,用优雅的数据,显示了rate of ice loss from the Antarctic ice sheet since 2002, relative to the 2002 to 2011 average.

Source: NASA/University of California, Irvine

5. What’s going on in the Arctic is quite different because it’s mainly ocean

While the Antarctic is a land mass surrounded by ocean, the Arctic is an ocean with land around the outside. The different geographies mean that the forces determining sea ice distribution are different. In the Arctic, floating sea ice melts as a direct result of warming water and the wind does not play such a major role. In September, Arctic sea ice reached itslowest extentsince satellite records began in 1979.

6. The world is losing ice overall

Although Antarctic sea ice is growing in extent, the loss of sea ice in the Arctic outweighs this small gain. The graph below from climate science bloggerTaminoshows that globally, sea ice has been decreasing steadily since 1979. The zero point on the left hand side of the graph is the average sea ice extent for the period 1979 to 2011.

Source:Tamino. Data is from USNational Snow and Ice Data Center.

Together with the loss of ice mass from theGreenland and Antarctic ice sheets, this means that the earth is losing ice overall. A loss in ice cover means that the earth’s surface reflects less solar energy, reinforcing atmospheric warming. Melting ice sheets add freshwater to the oceans, contributing tosea level rise.

Focusing on the whole picture

Some media outletshave played down the consequences of climate change for declining global ice cover by focussing on the gains in Antarctic sea ice. While this has led to some confusing and at times apparently contradictory media coverage, there are some very accessible internet resources to keep up to date with the latest changes in polar ice cover. These include the National Snow and Ice Data Center (NSIDC) website, andCryosphere Today.

The information about ice that scientists have to work with is increasing. For example, just last month a team of scientists produced the firstthree-dimensional mapof the underside of Antarctic sea ice using a robot submarine.

Maps like these will help scientists better understand how climate change may be affecting the thickness of sea ice, as well as the area it covers. Only by considering sea and land ice in both hemispheres can we get a full picture of how the planet is responding to global warming.