Global Warming

How Much Ice Can Antarctica Afford to Lose?

Over the past 20 years, ice shelves in Antarctica that normally support the rest of the continent's glaciers have been shrinking, and some have disappeared entirely. How much more ice can disintegrate before Antarctic glaciers start freely tumbling into the ocean?

A recent study led by researchers at the Friedrich-Alexander-Universität, in Germany, has mapped out which Antarctic ice shelves are buttressing the most ice and which are more "passive" and thus can stand to lose a large area without any immediate effect on the rest of the ice shelf.

Ice shelves are slabs of ice several hundred meters thick that extend from the edges of the mainland and float on the surface of the sea. They are firmly linked to glaciers and ice streams in mainland Antarctica, which slowly push the floating ice farther seaward, according to the researchers. When the seaward fronts of these ice shelves break off, they form new icebergs and the loss of ice is naturally replenished by the glacier ice from the mainland flowing in.

Some of the ice shelves, however, also push back on the glaciers, providing resistance and reducing the speed at which the glaciers flow into the ocean, said lead study author Johannes Fürst, a research assistant at the Institute of Geography at the Friedrich-Alexander-Universität.

"Ice shelves restrain the outflow from upstream like a plug in a bathtub," Fürst told Live Science. "If you take the plug out, the water runs out, except this is frozen water and if you take out the ice shelves its flow will accelerate out into the ocean and eventually raise sea levels."

In 1995, Antarctica's Larsen A ice shelf collapsed, removing ice cover from an area equivalent to the size of Berlin, according to Fürst. Seven years later, the much larger Larsen B ice shelf also broke apart. While the disintegration of the two shelves did not have an immediate effect on sea levels, the ice loss resulted in upstream glaciers accelerating by up to eight times their normal flow, according to the researchers.

Overall, the researchers found that 13 percent of the continent's ice shelf area can be classified as passive — an area about twice the size of Spain. This includes the Larsen C ice shelf in the Weddell Sea, which the researchers found is almost entirely a passive ice shelf.

Ice shelves in the Amundsen and Bellingshausen seas, however, are the most susceptible to further ice loss, according to the research findings. They are made up of 7 percent and 5 percent passive ice, respectively, the researchers found.

Global Warming

Antarctic icebergs have surprise role in slowing warming

The biggest icebergs breaking off Antarctica unexpectedly help to slow global warming as they melt away into the chill Southern Ocean, scientists said on Monday.

The rare Manhattan-sized icebergs, which may become more frequent in coming decades because of climate change, release a vast trail of iron and other nutrients that act as fertilisers for algae and other tiny plant-like organisms in the ocean.

These extract carbon dioxide from the atmosphere as they grow, a natural ally for human efforts to limit the pace of climate change blamed on man-made greenhouse gas emissions.

Ocean blooms in the wake of giant icebergs off Antarctica absorbed 10 to 40 million tonnes of carbon a year, the study estimated, roughly equivalent to annual man-made greenhouse gas emissions of countries such as Sweden or New Zealand.

The scientists studied satellite images of 17 giant icebergs off Antarctica from 2003-2013 and found that algae could turn the water greener for hundreds of kms (miles) around the icebergs, with nutrients spread by winds and currents.

There are typically 30 giant icebergs floating off Antarctica at any one time - they can linger for years. The study said the giant icebergs had an outsized impact in promoting ocean fertilization when compared with small icebergs.

Global Warming

Climate change and Antarctica

A world-renowned climate scientist visiting New Zealand will this week present new evidence suggesting a behemoth "sleeping giant" ice sheet is more sensitive to climate change than we ever thought.

To climate scientists, the vast East Antarctic Ice Sheet represents something of the elephant in the room in terms of what it could contribute to global sea level rise.

If all of it melted, the ice sheet, which forms most of Antarctica, would contribute an equivalent of around 50 metres of sea level rise - the vast majority of the total 58 metres that could come from the frozen continent.

The part of the ice sheet that rests on bedrock below sea level is most vulnerable and holds an equivalent of 19 metres of sea level rise.

In the face of climate change, which has brought warmer ocean water to the edges of Antarctica, the vast ice sheet has been long regarded by scientists to be much more stable when compared with the smaller, 25 million square kilometre West Antarctic Ice Sheet, which satellite measurements estimated was losing more than 150 cubic kilometres of ice each year.

But an Australian expedition that managed to reach the typically inaccessible Totten Glacier in East Antarctica in January revealed some of the first direct evidence that warmer waters were having a significant impact there as well.

This means the wider ice sheet's contribution to future sea level rise could be much greater than realised.

Buryatia: where thawing permafrost is turning to steppe

Buryatia has been hit in summer 2015 by the massive destruction of its pristine forests in a series of fast-spreading fires. Most shocking have been the scenes showing uncontrolled burning around Lake Baikal, the oldest and deepest lake in the world, containing 20% of the globe's unfrozen freshwater.

Local scientists have accumulated startling evidence of the changes in temperature which are turning the region's permafrost - established over many millennia - into steppe. Average annual temperatures in a rising number of areas are exceeding zero degrees Celsius.

Warming caused the upper layer of permafrost to become deeper - and where it is thin, to disappear altogether. The average annual precipitation isn't changing, but it evaporates more easily which causes the climate to get drier. This results in changes in flora. It becomes more monotonous, dominated by drought-resistant plants.

As the climate becomes drier, the territory covered in forests and meadows reduces, while the dry steppe - arid grass plains with few trees - increases. Apart from that, there are changes in terms of the radial growth of trees. In dry lands, including Selenginskyi and Kyakhtinskyi districts, growth slows down.

Currently, some 55,000 hectares remain ablaze in Buryatia. In other regions, the figures are 46,000 hectares in Krasnoyarsk and 11,000 in Irkutsk.

Environment

Scientists Find Antarctic Ice is Melting Faster

The summer ice melt in parts of Antarctica is at its highest level in 1,000 years, Australian and British researchers reported on Monday, adding new evidence of the impact of global warming on sensitive Antarctic glaciers and ice shelves.

Researchers from the Australian National University and the British Antarctic Survey found data taken from an ice core also shows the summer ice melt has been 10 times more intense over the past 50 years compared with 600 years ago.

"It's definitely evidence that the climate and the environment is changing in this part of Antarctica," lead researcher Nerilie Abram said.

Abram and her team drilled a 364-metre (400-yard) deep ice core on James Ross Island, near the northern tip of the Antarctic Peninsula, to measure historical temperatures and compare them with summer ice melt levels in the area.

They found that, while the temperatures have gradually increased by 1.6 degrees Celsius (2.9 degrees Fahrenheit) over 600 years, the rate of ice melting has been most intense over the past 50 years.

That shows the ice melt can increase dramatically in climate terms once temperatures hit a tipping point.