Tag Archives: Glaciers

Antarctic warming could accelerate sea level rise

Warming would cause more Antarctic ice to break off and melt Image: PIK/R.Winkelmann
Rising concern: warming would cause more Antarctic ice to break off and melt
Image: PIK (R.Winkelmann)

By Alex Kirby

An international study says warming is affecting not only the Arctic but also the Antarctic – and that could significantly raise global sea levels much faster than previously predicted.

LONDON, 20 August, 2014 − The effect of climate change on the world’s two polar regions looks like a stark contrast: the Arctic is warming faster than most of the rest of the Earth, while most of Antarctica appears to remain reassuringly locked in a frigid embrace.

But an international scientific team says the reality is quite different. The Antarctic is warming too, it says, and the southern ice could become the main cause of global sea level rise during this century − far sooner than previously thought.

The study, led by the Potsdam Institute for Climate Impact Research (PIK) in Germany, found that ice discharge from Antarctica could contribute up to 37 centimetres to global sea levels by 2100.

Computer simulations

The study is the first comprehensive estimate of the full range of Antarctica’s potential contribution to global sea level rise based on physical computer simulations. It combines state-of-the-art climate models and observational data with various ice models.

The results of the study − published in the European Geosciences Union’s journal, Earth System Dynamics − reproduce Antarctica’s recent contribution to sea level rise, as observed by satellites over the last two decades.

“If greenhouse gases continue to rise as before, ice discharge from Antarctica could raise the global ocean by an additional 1 to 37 centimetres this century,” says the study’s lead author, Anders Levermann, PIK professor of dynamics of the climate system.

“Science needs to be clear about the uncertainty,
so that decision-makers can consider the potential implications . . .”

“This is a big range – which is exactly why we call it a risk. Science needs to be clear about the uncertainty, so that decision-makers on the coast and in coastal mega-cities like Shanghai or New York can consider the potential implications in their planning processes.”

The scientists analysed how rising global average temperatures resulted in a warming of the ocean around Antarctica, influencing the melting of the Antarctic ice shelves.

Antarctica currently contributes less than 10% to global sea level rise and is a relatively minor player in comparison with the impact of the oceans’ increasing thermal expansion and the melting of glaciers.

But the major contributors to future long-term sea level rise are expected to be the huge volumes of ice locked up in Greenland and the Antarctic ice sheets. The marine ice sheets in West Antarctica alone could raise sea level by several metres over a period of several centuries.

The study’s computed projections for this century’s sea level contribution are significantly higher than the upper end of the latest projections by the Intergovernmental Panel on Climate Change. These suggest a probable rise by 2100 of around 60cm, although other estimates put the figure almost twice as high.

Even if governments can agree and enforce strict climate policies limiting global warming below the international target level of a maximum 2°C increase, Antarctica’s contribution to global sea level rise is expected still to range from 0 to 23cm this century.

Critical input

A co-author of the study, Robert Bindschadler, from the NASA Goddard Space Flight Center, said: “This paper is a critical input to projections of possible future contributions of diminishing ice sheets to sea level by a rigorous consideration of uncertainty of not only the results of ice sheet models themselves but also the climate and ocean forcing driving the ice sheet models.

“Billions of dollars, euros, yuan, etc, are at stake, and wise and cost-effective decision-makers require this type of useful information from the scientific experts.”

But major modeling challenges still remain. Datasets of Antarctic bedrock topography, for instance, are still inadequate, and some physical processes of interaction between ice and ocean cannot yet be sufficiently simulated.

The team also emphasises that the study’s results are limited to this century, while all 19 of the comprehensive climate models used show that the impacts of atmospheric warming on Antarctic ice shelf cavities will hit with a time delay of several decades.

However, Levermann says: “Earlier research indicated that Antarctica would become important in the long term. But pulling together all the evidence, it seems that Antarctica could become the dominant cause of sea level rise much sooner.” − Climate News Network

Human factor speeds up glacial melting

Glaciers such as Artesonraju in the Peruvian Andes are melting at record rates Image: Edubucher via Wikimedia Commons
Glaciers such as Artesonraju in the Peruvian Andes are melting at record rates
Image: Edubucher via Wikimedia Commons

By Tim Radford

Scientists simulating changes in mountain glaciers over the last century and a half have established that rates of melting have increased greatly in recent years – and that humans are the main culprits.

LONDON, 17 August, 2014 – The impact of human activity is melting the glaciers in the world’s mountain regions, and is doing so at an accelerating rate.

Ben Marzeion, a climate scientist at the University of Innsbruck’s Institute of Meteorology and Geophysics, Austria, reports with colleagues in the journal Science that they used computer models to simulate changes in the world’s slow-flowing frozen rivers between the years 1851 and 2010. The study embraced all the world’s glaciers except those in Antarctica.

This kind of manipulation allows researchers to play with the possibilities and see, for instance, how much changes in the sunlight patterns, high-level atmospheric changes because of volcanic eruptions, or simply slow cycles of natural weather patterns might be at work in the ice record.

The answers were unequivocal about human impact on the environment. “In our data, we find unambiguous evidence of anthropogenic contribution to glacier mass loss,” Dr Marzeion says.

In retreat

That glaciers are losing mass − retreating uphill, and melting at a faster rate − is not in doubt. A year ago, one group established without any doubt that worldwide, and overall, glaciers are in retreat.

In South America, some glaciers in the Andes are melting at a record rate, while satellite measurements show that the Jakobshavn glacier in Greenland doubled its flow speed between 1997 and 2003, and has doubled it again since 2003.

In Europe, 19th-century landscape painters, pioneer photographers and mountain guides unwittingly made permanent, easily-accessible records of Alpine glacier geography. These now set a baseline for all modern measurements, and researchers have established that the melt is getting faster.

The challenge is to determine how much of this is due to natural causes, and how much to changes in human land use, and the emission of greenhouse gases.

Higher proportion

The Innsbruck team has calculated that around a quarter of all the melting between 1851 and 2010 can be put down to human activity. But that is the overall picture: the proportion gets higher with time. Between 1991 and 2010, the fraction of melting due to human activity rose to two-thirds.

“In the 19th century and first half of the 20th century we observed that glacier mass loss attributable to human activity is barely noticeable, but since then has steadily increased,” Dr Marzeion says. – Climate News Network

Lakes raise new question on Arctic warming

Thermokarst lakes formed in melting permafrost in Alaska. Image: 16Terezka via Wikimedia Commons
Thermokarst lakes formed in melting permafrost in Alaska.
Image: 16Terezka via Wikimedia Commons

By Alex Kirby

Research into the lakes that form when permafrost melts challenges the widely-held view that they are contributing to Arctic temperature rise by releasing carbon into the atmosphere.

LONDON, 4 August, 2014 − Scientists say there is uncertainty over a previously unquestioned assumption about the way in which temperatures are rising in the Arctic.

New research, supported by the US National Science Foundation (NSF), suggests that a rethink is required on the widely-held scientific view that thawing permafrost uniformly accelerates atmospheric warming.

Instead, the scientists say, their findings show that one type of Arctic lake stores more greenhouse gases (GHGs) than it emits into the atmosphere.

But they say the effect is unlikely to be permanent, because increasing Arctic warmth will probably lead to the renewed release of the gases stored in the lakes.

Melted fresh water

The study, published in the journal Nature, focuses on thermokarst lakes, which appear as permafrost thaws and create surface depressions that fill with melted fresh water, converting previously frozen land into lakes.

The research suggests that Arctic thermokarst lakes are “net climate coolers” when observed over millennial timescales.

The Arctic is one of the fastest-warming regions on Earth. Sea ice has been retreating in the last 30 years or so by 12% a decade, NASA says, and spring and autumn on the Greenland icecap have warmed by more than 3°C.

But the new research suggests the lakes have not been contributing to this recent warmth, although thousands of years ago they did release GHGs.

“Until now, we’ve only thought of thermokarst lakes as positive contributors to climate warming,” said lead researcher Katey Walter Anthony, who is associate research professor at the University of Alaska Fairbanks Institute of Northern Engineering.

“It is true that they do warm climate by strong methane emissions when they first form, but on a longer-term scale they switch to become climate coolers because they ultimately soak up more carbon from the atmosphere than they ever release.”

The team found, thermokarst lakes in ice-rich regions of North Siberia and Alaska began cooling about 5,000 years ago. They stopped emitting methane and carbon dioxide, and instead started storing CO2 from peat-rich sediments.

The researchers used published data, their own field observations of Siberian permafrost and thermokarsts, radiocarbon dating, atmospheric modelling and spatial analyses to study how thawing permafrost is affecting climate change and GHG emissions.

Over the millennia, they say, several factors stimulated high rates of carbon deposits in lake sediments. These included thermokarst erosion and accumulations of organic matter, nutrient release from thawing permafrost, and slow decomposition in cold lake bottoms that lacked oxygen.

Carbon uptake

The study’s co-author, Miriam Jones, of the US Geological Survey, said: “These lakes are being fertilized by thawing yedoma permafrost [a type of permafrost rich in organic material]. So mosses and other plants flourish in these lakes, leading to carbon uptake rates that are among the highest in the world, even compared to carbon-rich peatlands.”

The study also found that when the lakes drain, previously thawed organic-rich lake sediments freeze again, storing a large amount of carbon processed in and under thermokarst lakes.

But the researchers say the new carbon storage will not last indefinitely. Future warming will probably start re-thawing some of the permafrost and release some of the carbon it contains.

Roughly 30% of global permafrost carbon is concentrated within 7% of the permafrost region in Alaska, Canada and Siberia. The study has expanded estimates of how much carbon the circumpolar peat stores in permafrost regions by more than 50%.

And it leaves scientists puzzling over a further question. The thermokarst lakes, according to this study, have been storing GHGs, not emitting them. So what else, despite that, is continuing to warm the Arctic faster than most of the rest of the planet? − Climate News Network

Data adds to confusion over polar sea ice

The expansion of Antarctic sea ice may have been overestimated. Image: Jason Auch via Wikimedia Commons
The expansion of Antarctic sea ice may have been overestimated.
Image: Jason Auch via Wikimedia Commons

By Tim Radford

Possible errors in the interpretation of satellite data may help to explain scientists’ puzzlement over indications that sea ice cover is apparently increasing in the Antarctic, but is shrinking visibly in the Arctic.

LONDON, 26 July, 2014 − Scientists believe they may have found explanations for two inconsistencies in their understanding of global warming.

One cause for head scratching is in the Antarctic, where the sea ice seems to be getting bigger when it ought to be shrinking, and another has been the apparent slowdown overall in the rate of global warming for the last decade.

Climate scientists around the world have been picking away at both puzzles, and not just because climate sceptics and energy industry lobbyists use them as ammunition to argue that global warming is not a problem at all. Scientists are naturally unhappy when data doesn’t match their predictions − and they want to know the reason why.

The Antarctic problem is hard to miss. The Arctic Ocean sea ice is shrinking visibly, and the entire sea could be ice-free most summers in a few decades. But even though there is clear evidence from separate sources that West Antarctica is responding to climate change, the southern hemisphere ice cover, overall, has been increasing.

Or has it? Ian Eisenman, a climatologist at the Scripps Institution of Oceanography at the University of California San Diego, begs to differ. He and colleagues report, in The Cryosphere journal, that it could be due to an error in the way satellite data is processed.

Spliced together

Scientists have been using satellite data to check sea ice cover for 35 years. But the data does not come from one instrument on just one satellite: observations transmitted from a series of satellites have been spliced together.

One report from the Intergovernmental Panel on Climate Change said the sea ice cover was more or less constant, but a later report said it had grown by 16,500 square kilometers a year between 1979 and 2012.

“When we looked at how the numbers reported for the trend had changed, and we looked at the time series of Antarctic sea ice, it didn’t look right,” Dr Eisenman said.

The researchers think that the difference between the two datasets might be linked to a change in satellite sensors in 1991, and the way the data collected by the two instruments was calibrated. What the Scripps team has done is identify a source of possible error, but it hasn’t settled the question one way or the other.

Since the Arctic and Antarctic are very different places, it would be unrealistic to expect the patterns of melting to be the same. And it may still be that southern hemisphere sea ice is growing.

However, while that question remains open, there is less doubt about the long slowdown in the rate of average global warming during the 21st century.

Missing heat

Separate teams of researchers have proposed a series of possible explanations for the failure of the climate to keep up with the projections of the climate scientists. These have included the suggestion that the missing heat may be “concealed” in the deep oceans, and that a pause in warming was going to happen anyway, but it just happened earlier than anyone expected.

Shaun Lovejoy, professor of physics at McGill University in Canada, reports in Geophysical Research Letters that there is yet another explanation. He argues, from statistical analysis, that coincidentally with the increase in man-made emissions of greenhouse gases, there has been a natural cycle at work, and that the most recent human impact on climate has been damped down by a cooling phase.

He had already ruled out with 99% certainty the possibility that natural variation could explain all the ups and downs of global average temperatures since 1800. This time he used the same statistical approach to the data for the 15 years from 1998 to the present.

His research suggests that there has been a natural cooling of 0.28°C to 0.37°C since 1998, which is in line with natural variations that occur every 20 to 50 years. “The pause has a convincing statistical explanation,” Lovejoy says. – Climate News Network

New clue to Antarctic food-web puzzle

Strength in numbers: thousands of Adélie penguins at a rookery Image: Michael Van Woert/NOAA NESDIS, ORA via Wikimedia Commons
Strength in numbers: thousands of Adélie penguins in an Antarctic rookery
Image: Michael Van Woert/NOAA NESDIS, ORA via Wikimedia Commons

By Tim Radford

A landmark research study that shows one species of penguin is thriving while other populations are in rapid decline offers new insight into how climate change is affecting Antarctica.

LONDON, 16 July, 2014 − Good news from Antarctica: the continent may be warming, the ice shelf may be at risk, and the food chain may ultimately become precarious, but the Adélie penguin population – at least for the moment − is higher than ever before.

The news does not suggest that global warming and climate change are actually good for this important indicator species, which has certainly been in decline on the Antarctic Peninsula. But it does represent an advance: for the first time, a comprehensive study has concluded with a full census of the species.

Heather Lynch, assistant professor of ecology and evelotion at Stony Brook University in New York, and Michelle La Rue, research fellow at the University of Minnesota’s Polar Geopspatial Center, used high resolution satellite imagery to measure levels of penguin guano – the fertiliser industry’s preferred term for seabird excrement – on the continent.

They then used that as the basis for calculating the numbers of birds in a colony necessary to account for all that digested and evacuated seafood.

They report in a journal called The Auk: Ornithological Advances that they identified at least 17 populations of Adélie penguins not previously known to exist, but failed to pinpoint 13 already-recorded colonies, and declared eight of them eradicated.

Their estimate for the total Adélie population in and around the Southern Ocean stands at 3.79 million, which is 53% higher than all previous estimates.

Useful evidence

The researchers call their work a “landmark” study, and see it not as evidence that climate change is going to work for the benefit of one particular species, but more as a useful piece of the great food-web puzzle in a changing climate.

Penguins have been in rapid decline in the West Antarctic Peninsula, which has become one of the fastest-warming regions on the planet. Warmer weather and increased rain have already started to take toll of Magellanic penguins in Argentina, and researchers recently predicted long-term decline for the iconic Emperor penguin on Antarctica itself.

But this is only long-term decline. As long as Antarctica stays cold and the ice shelf stays stable, the researchers say, the population could, in the short term, actually rise.

That is because what matters most to the species that nest in Antarctica is the supply of fish and krill around the continent’s edge. The health and resilience of the Adélie population – and the Emperor penguin, the leopard seal, the cetaceans, and so on – ultimately depend on how the krill and fish populations respond to climate change.

Humans, too, fish for commercial supplies of Antarctic krill, which provides a source of food for fish farms.

“Our finding of a 53% increase in Adélie penguin breeding abundance, compared to 20 years ago, suggests that estimates of krill consumption by this species may be seriously underestimated,” Dr Lynch said. “Leaving enough prey for natural krill predators is an important element in ensuring fisheries proceed sustainably.”

But a second team confirms in Nature Communications that there are strong links between climate and marine life, and that changes in factors such as wind speed and sea ice can have knock-on effects right around the Antarctic food web.

Since 1990, scientists aboard US research vessels have been conducting annual surveys along the western side of the Antarctic Peninsula, measuring populations of photosynthetic algae.

These peak every four to six years, according to changes in atmospheric pressure between the mid-latitudes and Antarctica itself.

Glacial meltwater

In winter, when cold southerly winds blow across the Peninsula, the winter ice extends. Winds drop from spring to summer, reducing the retreat of the ice. So the water column in summer then is stable, and the phytoplankton multiply, fed by iron-rich glacial meltwater.

The blooms of phytoplankton are what the krill need to multiply, and when the krill are around in huge volumes, the Adélie and other penguins, fur seals, baleen whales and albatross don’t have to go so far to find food.

But marine scientist Grace Saba, who did her research while with the Virginia Institute of Marine Science, before moving to Rutgers University, New Jersey, reports that these ideal conditions – negative phases of the Southern Annular Mode (SAM), to give it the technical terminology – are not guaranteed in future. If the world goes on burning fossil fuels, conditions will probably change.

“Projections from global climate models under business-as-usual emission scenarios up to the year 2100 suggest a further increase in temperature and in the occurrence of positive-SAM conditions,” Dr Saba said.

“If even one positive SAM episode lasted longer than the krill lifespan – four to six years with decreased phytoplankton abundance and krill recruitment – it could be catastrophic to the krill population.”  − Climate News Network

Arctic warming upsets birds’ breeding calendar

 

A chick of the Arctic migrant bird, the red-necked phalarope Image: US Fish and Wildlife Service via Wikimedia Commons
Early bird: a chick of the Arctic migrant, the red-necked phalarope
Image: US Fish and Wildlife Service via Wikimedia Commons

By Tim Radford

As global warming increasingly causes Arctic snow to melt earlier, researchers warn that it could have a long-term adverse effect on the breeding success of migrant birds.

LONDON, 8 July, 2014 − Arctic migrants are nesting up to seven days earlier as the world warms. The sandpiper makes a beeline for the Alaskan shores, to join the phalarope on the beach and the songbirds in the woods − and all because the winter snows are melting earlier.

Conservation scientists Joe Liebezeit and Steve Zack – both then of the Wildlife Conservation Society (WCS) – and colleagues report in the journal Polar Biology that they looked into nearly 2,500 nests of four shorebird species in Alaska – two sandpipers, two phalaropes − and a songbird called the Lapland songspur over a nine-year period.

Nest timing

They recorded when the first eggs were laid. And they also assessed snow melt in nesting plots at different times in the early spring, and took note of predator abundance and the seasonal flush of vegetation − both of which can affect nest timing − to see what mattered most in terms of breeding.

“It seems clear that the timing of the snow melt in Arctic Alaska is the most important mechanism driving the earlier and earlier breeding dates we observed in the Arctic,” said Liebezeit, now of the Audubon Society of Portland, Oregon.

“The rates of advancement in earlier breeding are higher in Arctic birds than in other temperate bird species, and this accords with the fact that the Arctic climate is changing at twice the rate.”

During the nine years in which the scientists conducted their study, they found that nesting advanced by between four and seven days.

“Migratory birds are nesting earlier in the changing Arctic, presumably to track the earlier springs and abundance of insect pray,” said Steve Zack, who is the WCS co-ordinator of bird conservation.

“Many of these birds winter in the tropics and may be compromising their complicated calendar of movements to accommodate this change. We’re concerned that there will be a threshold where they will no longer be able to track the emergence of these earlier springs, which may impact breeding success or even population viability.”

Ecology changing

The calendar of Arctic life is shaped by ice, and the ecology of the region is beginning to change as the area of sea covered by ice shrinks with successive summers.

But Ingrid Onarheim, of the University of Bergen’s Geophysical Institute, and colleagues warn in the journal Tellus − published by the International Meteorological Institute at Stockholm University − that the Arctic ocean is losing ice even in winter, at least north of the island of Svalbard, Norway.

A study of satellite records shows that this region is losing winter ice at the rate of almost 10% per decade, and the north Atlantic water that enters the Arctic ocean at this point has been warming at 0.3°C per decade. At the same time, the surface air temperature has been warming at 2°C per decade, and researchers have recorded an average rise in winter temperatures of 6.9°C in the last 34 years.

They believe that winds have not caused the long-term warming or loss of ice, so it must be warmer ocean temperatures pushing into the region west of Svalbard. The ice, furthermore, has thinned with the decades, making it more likely to melt and retreat with each succeeding winter. – Climate News Network

Whalers tale sheds new light on Arctic ice

Oil painting by John Wood (1798-49) of British whalers circa 1840 Image: Lee and Juliet Fulger Fund via Wikimedia Commons
Oil painting by John Wood (1798-1849) of British whalers circa 1840
Image: Lee and Juliet Fulger Fund via Wikimedia Commons

By Tim Radford

Vital data on the Arctic ice sheet before extensive fossil fuel use began to impact on climate has been gleaned from a new study analysing the log books of British whaling ships’ journeys more than 200 years ago.

LONDON, 5 July, 2014 − British whaling ships from Tyneside in the north-east of England made 458 trips to the edge of the Arctic ice between 1750 and 1850. Their log books contained detailed records of perilous journeys, whales caught, and the tons of blubber and barrels of oil they brought home.

For Matthew Ayre, a PhD student at the University of Sunderland, UK, and Dennis Wheeler, the university’s Emeritus Professor of Climatology, these log books and other records by merchant ships and Arctic explorers such as Sir John Franklin − who tried in 1845 to navigate the icy North-West Passage between the Atlantic and the Pacific − represent an extraordinary resource.

They give an account of the southern edge of the ice sheet, the prevailing weather, the spring and summer extremes, the storms, and the condition of the Arctic ice shelf.

Planetary climate

And the log books offer a snapshot of conditions in the century before the first systematic use of fossil fuels began subtly to alter the planetary climate.

The catch, of course, is that the log books were composed in the technical language used by the masters of sailing ships more than 200 years ago, augmented by the jargon appropriate to a trade abandoned by the British more than a century ago.

For Ayre, the first great challenge was to compile a systematic sea ice dictionary and translate it into the language used by scientists today. He then validated his data with five weeks on the US Coastguard ice breaker and research vessel, USCGC Healy, exploring the edge of the polar ice at first hand. His study, which is part of the collaborative ARCdoc project, concentrates on the Davis Straits between north America and Greenland, and the north-west Atlantic.

The evidence confirms satellite observations made in the last three decades that the extent of the polar ice was once far greater, and that the Arctic ice is in historic retreat.

“Significantly, this is the first time we have ever had direct observational information on the ice fronts in the north Atlantic and the Davis Straits area before 1900,” Dr Wheeler said. “Until the introduction of satellite information from the 1970s, we didn’t know what the ice was doing.

“These log books contain absolutely vital
climatological information”

“Well, now we know it was more advanced − therefore, the retreat of the ice in the last 30 years is part of a more recent and new pattern of climate change. So these log books contain absolutely vital climatological information.”

All systematic weather records are relatively recent. The oldest continuous temperature series dates from England in 1659, but records from most of the world, until the last century, were random or simply sparse.

So climate researchers go for what they call proxy data – such as ice cores, lake sediments and tree rings – that provides overall clues to changing patterns of climate during the millennia.

There are other secondary sources – such as monastery and historic estate archives recording farm yields − that offer clues to bygone summers.

Life or death

But the richest resource is probably the log books of the naval ships and merchantmen, the whalers and adventurers who took to the seas in the great age of exploration that began in the 16th century. For such men, the state of the ice and the weather at its edge was a matter of life or death.

The challenge was to match what 18th-century observers recorded with the scientific observations to be made now.

Ayre got his chance aboard the US research vessel, using as a guide an epic account of the Arctic regions, written in 1820 by the Whitby whaler and pioneer scientist, William Scoresby.

“I was making observations every four hours aboard Healy, using Scoresby’s definitions and the Healy researchers’ own daily records, testing how accurate our data is to validate what is in the sea ice dictionary,” Ayre said.

“Apart from modern day research vessels, these are the only books in history from ships that seek out the ice edge in great detail and follow it.” – Climate News Network

Emperor penguin’s Antarctic realm is in peril

 

Iconic pose: emperor penguins' habitat is under serious threat Image: John Landis/NSF via Wikimedia Commons
Iconic pose: emperor penguins’ habitat is seriously threatened by climate change
Image: John Landis/NSF via Wikimedia Commons

By Tim Radford

Loss of Antarctic sea ice through climate change threatens the emperor penguin’s habitat to such an extent that scientists say it should now be made an iconic symbol – like China’s endangered giant panda – of the wildlife conservation movement.

 

LONDON, 3 July, 2014 − Global warming will this century take its toll of Antarctica’s most regal predator, the emperor penguin. There are now 45 colonies of this wonderful bird, but by 2100 the populations of two-thirds of these colonies will have fallen by half or more.

Stéphanie Jenouvrier, a biologist at the Woods Hole Oceanographic Institution in the US, and colleagues from France and the Netherlands report in Nature Climate Change that changes in the extent and thickness of sea ice will create serious problems for a flightless, streamlined ,survival machine that can live and even breed at minus 40°C, trek across 120 kilometres of ice, and dive to depths of more than 500 metres.

The researchers took all the data from 50 years of intensive observation of one colony in Terre Adélie and used climate models to project a future for the other 44 colonies known in the Antarctic.

Decisive factor

They found that the decisive factor in emperor penguin survival was the sea ice. If the seas warmed and there wasn’t enough ice, then that affected the levels of krill in the southern ocean, and therefore reduced the available prey. It also made the penguins more vulnerable to other predators.

If the opposite happened and there was too much sea ice, then foraging trips took longer and penguin chicks were less likely to survive.

Aptenodytes forsteri – the Linnean name for the emperor – is not in trouble yet, and its numbers may even grow in the years up to 2050. But this growth won’t last, and decline is likely everywhere. Climate change has already begun to affect penguin species much further north, in Argentina, by taking toll of young chicks.

Endangered class

For different reasons, the average rise in global temperatures forecast by the Intergovernmental Panel on Climate Change (IPCC) could push the emperor into the endangered class.

“If sea ice declines at the rates projected by the IPCC climate models, and continues to influence emperor penguins as it did in the second half of the 20th century in Terre Adélie, at least two-thirds of the colonies are projected to have declined by greater than 50% from their current size by 2100,” Dr Jenouvrier said.

“None of the colonies, even the southernmost locations in the Ross Sea, will provide a viable refuge by the end of the 21st century.”

The researchers end their paper by arguing that the emperor should – like the giant panda in China – become an icon for the conservation movement.

They conclude: “We propose that the emperor penguin is fully deserving of Endangered status due to climate change, and can act as an iconic example of a new global conservation paradigm for species threatened by future climate change.” – Climate News Network

Icebergs strip away rich Antarctic habitat

Icy waters near the Rothera research station in Antarctica Image: Vincent van Zeijst via Wikimedia Commons
Icy waters near the Rothera research station in West Antarctica
Image: Vincent van Zeijst via Wikimedia Commons

By Tim Radford

The scouring effect of drifting icebergs that are increasingly breaking free from Antarctic ice shelves as a result of global warming is wiping out fauna that cling to the boulders in shallow waters

 LONDON, 23 June, 2014 − A once-rich habitat in the Antarctic has become an impoverished zone as icebergs, increasingly breaking free from the surrounding sea ice because of global warming, scour the shallow-water rocks and boulders on which a diversity of creatures cling to life.

A report in the journal Current Biology says that researchers who carried out a survey dive in 2013 at Lagoon Island, off the West Antarctic Peninsula, discovered that “no live mega or macro-fauna can be found, the first time this has been observed there, despite being regularly visited by scientific divers since 1997”.

David Barnes, of the British Antarctic Survey, and colleagues report that boulders on the seabed near the Rothera research station had once been richly encrusted with creatures that competed for living space. Now such rocks might only support a single species.

Early warning system

“The Antarctic Peninsula can be considered an early warning system, like a canary in a coal mine,” Dr Barnes said. “Physical changes there are among the most extreme and the biology considered quite sensitive, so it was always likely to be a good place to observe impacts of climate change.

“But impacts elsewhere are likely to be not too far behind. A lot of the planet depends on the near shore environment, not least for food. What happens there to make it less stable is important.”

A research diver surveys the shallow waters of West Antarctica Image: British Antarctic Survey
A research diver surveys the shallow waters off the West Antarctic Peninsula
Image: British Antarctic Survey

Climate change has already begun to affect Antarctica in different ways. Researchers last year found that as icebergs broke free, the surviving ice shelf had begun to melt from underneath from underneath. The effect of the drifting bergs was mixed: at depth in the fjords of the Peninsula, for instance, the species variety seemed to have got richer, according to one set of observations.

But no such effect was observed in the ocean shallows that are being scraped and scoured by drifting icebergs. The researchers say that although no species has disappeared entirely from the region, the numbers are so low as to be negligible.

In 2013, most of the observations seemed to involve just one opportunistic or pioneer species, a suspension feeder called Fenstrulina rugula. What had once been a rich habitat had become one of the simplest seabed systems to be found anywhere.

Ecological roles

“Reduction of complex systems into very simple ones, where many (formerly important) species become too rare to maintain meaningful ecological roles, is a common reaction to anthropogenic disturbance such as overfishing, pollution, introductions of non-indigenous species, and habitat destruction,” the report’s authors say.

“Across West Antarctica, the levels of these disturbances are among the lowest globally, apart from greenhouse contributions to climate change.”

The scientists conclude: “We expect the deeper seabed to become richer in benthic colonisation with more ice shelf collapses and fast ice losses, but hard surfaces in the shallows are likely to become deserts dominated by rapidly-colonising pioneers and responsive scavengers.” − Climate News Network

Flow chart unclear for glacial rivers

 

Confluence of the Indus and Zanskar rivers that rise in Tibet SImage Sundeep Bhardway via Wikimedia Commons
Confluence of the glacial Indus and Zanskar rivers flowing from Tibet
Image: Sundeep Bhardwaj via Wikimedia Commons

By Kieran Cooke

Glaciers in the high Himalayas and on the Tibetan Plateau are a vital source of water for millions of people in Asia, but scientists question what will happen to supplies if the rate of melting continues to rise due to climate-related factors

 

LONDON, 19 June – A new study examining river basins in the Asia region suggests that amounts of water supplied to the area by glaciers and rainfall in the Himalayas will increase in the coming decades.

At first reading, that looks like good news, as an estimated 1.3 billion people in Pakistan, India, Bangladesh, Nepal, China and elsewhere are dependent for their water supplies on rivers fed by glaciers and snowmelt.

But the less welcome news is that scientists are unsure what will happen after 2050 if the rate at which glaciers melt continues to increase as a result of climate change.

Scientists say rising temperatures and more intense rainfall patterns in the higher Himalayas are causing the retreat of the majority of glaciers in the region.

Heat build-up

They say glacier melt is also being caused by black carbon – particulate matter that, in South Asia, comes mainly from cooking fires, the burning of waste, plus coal burning and diesel exhausts. The black carbon, or soot, falls on the glaciers, reducing reflectivity and increasing heat build-up.

This latest study of glacier melt and water flows, appearing in the journal Nature Climate Change, was carried out by scientists at Future Water, a Netherlands-based research group, Utrecht University, and the Nepal-based International Centre for Integrated Mountain Development.

It assesses the contribution of glacier and snowmelt to the region’s river basins, incorporating some of the world’s mightiest rivers – the Indus, the Ganges, the Brahmaputra, the Mekong and the Salween.

The scientists say that highly-sophisticated modelling techniques were used to study the river basins in unprecedented detail.

They report: “Despite large differences in runoff composition and regimes between basins and between tributaries within basins, we project an increase in runoff at least until 2050, caused primarily by an increase in precipitation in the upper Ganges, Brahmaputra, Salween and Mekong basins and from accelerated melt in the upper Indus Basin.

“These findings have immediate consequences for climate change policies where a transition towards coping with intra-annual shifts in water availability is desirable.”

Uncertain supplies

But while the study says that, up to mid-century, little change is likely in the amount of glacier melt water flowing into river basins, it is unclear what will happen thereafter to the water supplies for  what is a significant portion of the world’s population.

“Our study does not include projections after 2050,” Arthur Lutz, lead author of the study, told Climate News Network. “However, at some point in time, the contribution of glacier melt to the total flow will decrease, because of the decreasing glacier extent. When this happens, it will differ for different river basins and sub-basins.”

The study says the long-term outlook is particularly uncertain for the upper Indus basin. While glacier melt contributes only 11.5% of the total runoff in the upper basin of the Ganges river, it contributes more than 40% of total water runoff in the upper Indus basin.

The Indus river, which flows for nearly 2,000 miles from high up in the Hindu Kush-Karakoram Himalaya mountain range down to the Arabian Sea, is vital to life in Pakistan, providing water for 90% of the country’s agricultural crops. Hydro plants along the Indus also supply about half the country’s electricity. – Climate News Network