Why is the Arctic melting faster than the Antarctic?

A recent report says the Arctic may be ice-free by 2040. The Antarctic is also melting, albeit far slower, and in a less regular pattern. Why do the two poles react so differently in the face of climate change?

First, the bad news: The Arctic is melting much faster than expected, and could even be ice-free in summer by the late 2030s, a report from the Arctic Council's Arctic Monitoring and Assessment Program suggests. Previous studies had forecast an ice-free North Pole in summer by mid-century.

Nature and Environment | 02.06.2017

While the outlook is bleak for the Arctic, there is a silver lining for the Antarctic: The ice is melting at a slower rate than previously thought. Although glacier flow has increased since the 1990s, scientists from University of Leeds have found the melting rate to be only around a third of what was previously projected.

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Mapping the ice

Operation IceBridge studies the processes that link the polar regions with the Earth's climate system. Rapidly changing polar ice means researchers need to use highly sophisticated airborne technology to measure annual changes in thickness and movement - onboard a retrofitted 1966 Lockheed P-3 aircraft.

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Ready for takeoff

It's all part of a six-year project under NASA's Cryosphere Program, in which researchers are carrying out a series of eight-hour flights over Greenland (from March to May) and Antarctica (October to November) in order to accurately model a three-dimensional view of ice sheets, ice shelves and sea ice.

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Ice meets cloud

In 2003, NASA launched a satellite called ICESat (Ice, Cloud, and Land Elevation Satellite) for the purpose of monitoring changes in polar ice. However, it suddenly stopped collecting data in 2009. With ICESat-II not expected to be ready for launch until 2018, researchers needed to somehow bridge the nine-year data gap between the two satellites.

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Keeping an eye on things

Enter operation IceBridge, which has been keeping a close eye on the polar ice - as well as its cute inhabitants - while ICESat-II is prepped for launch next year. Or is the hare rather watching over these strange bipeds?

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Climate change in action

The data collected during these missions is critical for researchers in predicting the effects climate change is already having on the polar ice, including a rise in sea levels. According to NASA scientists, on March 7, 2017, sea ice in the Arctic reached the lowest maximum wintertime extent ever recorded.

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Seeing past the surface

A glacier is visible through mist above Ellesmere Island. Operation IceBridge allows scientists gather valuable data by using special ice-penetrating radar, which only functions properly when used in lower altitudes.

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Melting landscape

Scientists have long warned that the Arctic Circle will be one of the regions hit hardest by climate change - and effects are already becoming evident. The darker the color, the thinner the ice.

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Rugged terrain

Once ICESat-II is up and running, it will have the ability to take continuous measurements over a much wider area - unlike the current aircraft-based method, which is limited only to annual surveys.

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Trapped icebergs

Icebergs are locked in sea ice, as seen from the research aircraft along the Upper Baffin Bay coast above Greenland. Aircraft-based research allows its human pilots to focus on specific areas of scientific interest, rather than simply conducting a flyover on a fixed path.

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Ice on the retreat

As in Greenland, the ice fields of Ellesmere Island in Canada are also gradually retreating due to warming temperatures. The future of ICESat-II is now in question, as US President Donald Trump has pledged to strip funding for NASA's entire earth science program.

But the Antarctic is still melting. And a rapidly advancing crack in its fourth-largest ice shelf could soon see one of the largest icebergs ever recorded in human history break off into the sea.

Scientists agree that global warming causes both the ice in the North and the South Pole to melt. Air temperatures are climbing, and so are water temperatures. This makes the ice melt faster. The period of winter where the water is actually cold enough to freeze is getting shorter, which means ice floes are getting smaller.

Nature and Environment | 22.04.2017

The Arctic and Antarctic are far from "polar opposites" in the sense that ice at both is melting away in the face of climate change. But why are the Arctic and Antarctic melting at such a different pace?

Same same but different

Because the Arctic and Antarctic are cold, remote, and full of ice, they are often thought of as nearly the same. However, they are in fact quite different.

The first and most visible difference are the animals that call the frosty lands their home. Each polar extreme has a unique biome with many species that only survive there. Polar bears live in the Arctic and penguins only in the Antarctic, for example.

Arktis - Eisbär schwimmt

Polar bears depend on sea ice and may go extinct in the wild if the ice disappears

The second striking contrast is geography. The Arctic is a semi-enclosed ocean and almost completely surrounded by land. This means there is not much space for ice to float around. As a result, ice floes frequently bump into each other and pile up into thick ridges.

Arctic ice is thicker, and stays frozen longer during summer. In winter, the sea ice covers up to 15 million square kilometers (6 million square miles), and 7 million square kilometers remain at the end of the summer melt season.

The Antarctic is almost the geographic opposite of the Arctic - not just because it's on the other side of the world. The Antarctic consists of land surrounded by an ocean. The sea ice is free to move, and often floats northward into warmer waters where it eventually melts during the southern hemisphere's summer months.

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In the Antarctic, almost all of the sea ice that forms during winter melts during summer. In the colder months, up to 18 million square kilometers (7 million square miles) of ocean is covered by sea ice, but by the end of the summer, only about 3 million square kilometers of sea ice remains.

Infografik Arctic and Antarctic: Annual increase and decrease of sea ice ENG

Losses and gains

Growth and thaw of the ice is part of the annual cycle, and small fluctuations in the level of sea ice are normal. But scientists have observed a constant loss of sea ice in both the Arctic and Antarctic since the early 1970s.

This is due to global warming. Since the Arctic is an ocean and consists mostly of sea ice, it has been affected more by rising ocean temperatures than the Antarctic, which consists mostly of ice-covered land.

While the Antarctic has also lost sea ice, scientists discovered that ice is growing in other places. As glaciers in West Antarctica have melted, heavy snowfall in East Antarctica and the interior of West Antarctica led to an increase in ice sheets.

Although it seems counterintuitive, accumulation of snow in the Antarctic is in fact a sign of global warming. The warmer the temperatures are, the more moisture is in the air. And the more moisture there is, the more snow falls.

The Antarctic seems to be growing and melting at the same time. But overall, is it expanding or shrinking? This is the part that scientists don't agree about.

According to data by the NASA, gains in ice have outweighed the losses from thinning glaciers from 1992 to 2008.

Recent research by the University of Bristol, however, contradicts NASA's findings. The scientists claim in a study published early May that the gains in ice were three times smaller than suggested, and that the "Antarctica, as a whole, has been contributing to sea level rise."

Why do scientists find conflicting data?

This is due to differing methodologies, as well as a general lack of data.

Researchers started observing the Antarctic via satellite images in the late 1970s. That's not enough time to understand a complex system like the Antarctic, says Ted Scambos, a scientist at the National Snow and Ice Data Center, a research institute affiliated with the University of Colorado.

"The Antarctic system is highly variable. It's easily pushed around by changes of ocean temperatures and changes in the wind pattern," Scambos told DW. "Trends are not easily detected; we need a lot more time for that."

The Antarctic was long regarded to be immune to global warming. But Scambos believes that the response of the planet's southernmost continent is just slower than that of the Arctic.

While it might be too early to see a trend, recent headlines are worrying. Levels of sea ice is fluctuating strongly at both the Arctic and the Antarctic. In February, sea ice was at a record low both in the Arctic and Antarctic.

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'Great ambassadors'

Penguins – a favorite animal for many because of their clumsy, waddling gait – offer researchers a useful way to measure the health of their habitat. Christian Reiss, an Antarctic fisheries biologist at the US-based National Oceanic and Atmospheric Administration, said: "Penguins are great ambassadors for understanding the need to conserve Southern Ocean resources."

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Hit by climate change

Two thirds of the world's 18 penguin species, which range from the volcanic Galapagos Islands on the equator to the frozen sea ice of Antarctica, are in decline, according to a Pew study from 2015. Antarctic penguins in particular are vulnerable to climate change as shifting ice reduces their habitat and warming seas affect their prey.

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Under pressure

Scientists blame the decline in penguin numbers on intense fishing pressure on forage species such as krill, as well as pollution, damage to penguin breeding grounds, and climate change. Only two types of penguin – the Adélie and the King - are increasing in numbers, according to the International Union for Conservation of Nature Red List of Threatened Species.

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Marine bellwethers

Penguins live most of their lives at sea but return to land to breed and molt. This makes them important gauges of marine health that are easily accessible to researchers, who can then develop conservation strategies. Stanford University marine scientist Cassandra Brooks said: "Scientists need to continue working to untangle the complex interactions between climate change and penguin populations."

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Eco boost

The Ross Sea – one of the last intact marine ecosystems in the world, home to penguins – is getting a boost. A deal sealed last year by the Conservation of Antarctic Marine Living Resources - an international group tasked with overseeing conservation and sustainable exploitation of the Antarctic Ocean - will see a massive US and New Zealand-backed marine protected area in the Ross Sea.

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Biggest of them all

The largest of the 18 penguin species found today are emperors. They are around 120cm tall and weigh about 40kg, although their weight fluctuates through the year. But fossils recovered from the Antarctic peninsula reveal that a huge species of penguin which lived around 37 million years ago would have dwarfed emperors – the ancient penguins may have stood 2 meters tall and weighed up to 115kg.

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Going the distance

Adélie penguins are one of only five species of penguins that live on the Antarctic continent, the others being the emperor, gentoo, chinstrap and macaroni penguins. Like all penguins, Adélies are excellent swimmers - some have been recorded swimming as far as 300 km (150 km each way) to forage for their chicks.

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