Global Warming

Antarctica is gaining ice: NASA

An increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

Areas of the continent like the Antarctic peninsula have increased their mass loss in the last decades, says a new NASA study.

The research challenges the conclusion of other studies, including Intergovernmental Panel on Climate Change’s 2013 report which says that Antarctica is overall losing land ice.

According to the analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tonnes of ice a year from 1992 to 2001. The net gain slowed to 82 billion tonnes of ice per year between 2003 and 2008.

“We are essentially in agreement with other studies that show an increase in ice discharge in the Antarctic peninsula and the Thwaites and Pine Island region of West Antarctica,” explained Jay Zwally, glaciologist with NASA Goddard Space Flight Centre in Greenbelt, Maryland.

Our main disagreement is for East Antarctica and the interior of West Antarctica. “Here, we see an ice gain that exceeds the losses in the other areas,” he added. But it might take a few decades for Antarctica’s growth to reverse, according to Zwally.

The study analysed changes in the surface height of the Antarctic ice sheet measured by radar altimeters on two European Space Agency satellites and by the laser altimeter on NASA’s Ice, Cloud, and land Elevation Satellite (ICESat).

“At the end of the last Ice Age, the air became warmer and carried more moisture across the continent, doubling the amount of snow dropped on the ice sheet,” Zwally noted.

“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 mm per year away,” Zwally said. But this is also bad news.

“If the 0.27 mm per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for,” he pointed out in the study which appeared in the Journal of Glaciology.

Environment

Global Warming - Seas Freeze More Off Antarctica

One of the apparent contradictions of global warming is the increased melting of ice in the Arctic, but in Antarctica the extent of ice cover is increasing. A recent study looks for answers.

It seems that global warming is expanding the extent of sea ice around Antarctica in winter in a paradoxical shift caused by cold plumes of summer melt water that re-freeze fast when temperatures drop. Melted ice re-freezes faster than sea water in winter.

An increasing summer thaw of ice on the edges of Antarctica, twinned with less than expected snowfall on the frozen continent, is also adding slightly to sea level rise in a threat to low-lying areas around the world.

Climate scientists have been struggling to explain why sea ice around Antarctica has been growing, reaching a record extent in the winter of 2010, when ice on the Arctic Ocean at the other end of the planet shrank to a record low in 2012.

"Sea ice around Antarctica is increasing despite the warming global climate," said Richard Bintanja, lead author of the study at the Royal Netherlands Meteorological Institute. "This is caused by melting of the ice sheets from below.".

Ice is made of fresh water and, when ice shelves on the fringes of Antarctica thaw in summer because of upwellings of warming sea water, the meltwater forms a cool layer that floats on the denser, warmer salty sea water below.

In winter, the melt water readily turns to ice because it freezes at zero degrees Celsius, above sea water at -2C (28.4F).

At a winter maximum in September, ice on the sea around Antarctica covers about 19 million sq kms (7.3 million sq miles), bigger than Antarctica's land area. It then melts away into the ocean as summer approaches.

On the other hand, among other scientists, Paul Holland of the British Antarctic Survey stuck to his findings last year that a shift in winds linked to climate change was blowing a layer of melt water further out to sea and this was adding to winter ice.

Rescue

Russian sailors rescue this dog stranded on a small iceberg:

 

Environment

Cold in Ontario, Canada.

Stunning image of frozen trees on the shore of Lake Ontario. Captured by photographer Timothy Corbin.

Environment

Ice-Free Arctic Ocean in 2030?

Vast uncertainty remains over the causes of melting Arctic sea ice and when it may disappear altogether during the summer, which would have consequences for oil explorers, shipping firms and the fight against climate change.

The answer will depend on the balance of natural and manmade causes.

Last September sea ice reached its lowest level in the satellite record, which dates back to 1979, a development that has implications for local native communities and wildlife, local coastal erosion and possibly northern hemisphere weather.

Under the albedo effect, dry snow reflects more than 80 percent of solar radiation; bare ice 65 percent; and open water just 5 percent.

And increasing expanse of open water each summer warms up faster than ice-covered sea, meaning new ice will be thinner and more vulnerable the following year.

There are various underlying causes of the melt.

Rising greenhouse gas emissions drive up air and sea temperatures.

Water from a warmer Atlantic entering the Arctic Ocean through the Fram Strait between eastern Greenland and Svalbard, an island due north of Norway.

A similar inflow of warmer Pacific water through the Bering Strait has long been identified as an important process that causes the thinning of ice in the central Arctic.

There are also weather effects that may be natural, partly natural or entirely due to greenhouse gas emissions affecting Arctic ice.

A particular weather pattern contributed to a big melt six years ago by sending warm air towards the central Arctic, according to researchers from the Netherlands, Sweden and Germany.

The cumulative impact from rising greenhouse gas emissions, which combined with a few freak summers, ice export and the albedo effect could finish off summer sea ice rather quickly.

Increasingly, scientists and researchers are coming to believe that a seasonally ice-free Arctic Ocean might be realized as early as 2030.

Shrinking Antarctic Ice

The faster rate of shrinkage suffered by the vast Antarctic ice shelves has been found to be caused by warmer ocean water encroaching from below the ice driven by stronger westerly winds in the Southern Ocean.