Tag Archives: Ice Loss

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Bolivian glaciers melt at alarming rate

glaciers
glaciers

A new study mapping the effects of dwindling glaciers on people living in Bolivia reveals rapid shrinkage and potentially dangerous glacial lakes.

LONDON, 22 October, 2016 Between 1986 and 2014 – one human generation – the glaciers of Bolivia shrank by 43%, according to new research.

This presents a problem in the long term for more than 2 million people who rely on glacial meltwater supply in the dry season, and immediate danger in the short term for thousands who might live below precarious glacial lakes.

Glaciers are in retreat as the world warms − a consequence of rising levels of carbon dioxide in the atmosphere in response to the increasing combustion of fossil fuels.

They are dwindling almost everywhere in the Andean chain, in Greenland, in Alaska and Canada, the Himalayas, across the entire mass of Central Asia, and everywhere in the tropics.

Tropical glaciers

But a new study in The Cryosphere, the journal of the European Geosciences Union, is one of the first to examine in detail precisely what this retreat could mean for the human communities in Bolivia, home to one-fifth of the world’s tropical glaciers.

Researchers from two British universities and a Bolivian colleague examined NASA satellite images of the region and found that the area of the Bolivia Cordillera Oriental normally covered by glaciers fell from 530 square kilometres in 1986 to about 300 sq km in 2014 − a shrinkage of more than two-fifths.

They then turned to the glacial lakes − bodies of water left behind as a glacier retreats. Some are in natural dips in the bedrock, some are accidentally dammed behind walls of glacial debris.

All such lakes are precarious: rockfalls, earthquakes and avalanches can breach them or tip water from them to create a dangerous downstream flow.

We mapped hundreds of lakes,” says Simon Cook, senior lecturer in physical geography at Manchester Metropolitan University, who led the study.

Some lakes are very small and pose little risk. Others are very large, but there’s little or no possibility that they would drain catastrophically. Others are large enough to create a big flood, and sit beneath steep slopes or steep glaciers, and could be dangerous.”

Studies such as these are a demonstration that climate change is happening, and that science can deliver practical help to communities in the path of potential disaster or economic stress.

Most glaciers will be gone or much diminished
by the end of the century – so where will the water come from in the dry season?”

Civil engineers, geographers, conservationists and hydraulic engineers are no longer simply warning about the hazards of climate change. They have begun to identify the communities most vulnerable to flooding, the hazards to local biodiversity as forests and grasslands begin to feel the heat, and the cities most at risk from routine coastal flooding as sea levels rise. and the US states that must start planning now for future power disruption as a consequence of drought.

Meltwater matters to mountain communities. It supplies the drive for hydroelectric power and it delivers clean drinking water to the cities and irrigation for crops in the dry season.

Reservoirs at risk

Through the year, the 2.3 million people in the Bolivian cities of La Paz and El Alto get 15% of their water from glacial supplies; in the dry season, this figure doubles. Glacial meltwater also keeps regional rivers and lakes topped up. So as the glaciers retreat and the body of surviving ice dwindles, some of these reservoirs, too, are at risk.

The researchers pinpointed 25 lakes as potentially dangerous. Even the smallest, were it to drain completely, would tip a peak flow of 600 cubic metres of water a second down the hillside. The largest could discharge 125,000 cubic metres − 50 times the volume of an Olympic swimming pool − every second.

A glacial lake outburst in 2009 killed farm animals, destroyed crops and washed away a road, leaving villagers isolated for months.

Dr Cook says: “We considered that a lake was dangerous if there were settlements or infrastructure down-valley from the lake, and if the slopes and glaciers around the lake were very steep, meaning that they could shed ice or snow or rock into the lake, which would cause it to overtop and generate a flood – a bit like jumping into a swimming pool, but on a much bigger scale.

Most glaciers will be gone or much diminished by the end of the century – so where will the water come from in the dry season?

Big cities like La Paz are partially dependent on meltwater from glaciers. But little is known about potential water resource stress in more remote areas. Much more work needs to be done on this issue.” Climate News Network

A new study mapping the effects of dwindling glaciers on people living in Bolivia reveals rapid shrinkage and potentially dangerous glacial lakes.

LONDON, 22 October, 2016 Between 1986 and 2014 – one human generation – the glaciers of Bolivia shrank by 43%, according to new research.

This presents a problem in the long term for more than 2 million people who rely on glacial meltwater supply in the dry season, and immediate danger in the short term for thousands who might live below precarious glacial lakes.

Glaciers are in retreat as the world warms − a consequence of rising levels of carbon dioxide in the atmosphere in response to the increasing combustion of fossil fuels.

They are dwindling almost everywhere in the Andean chain, in Greenland, in Alaska and Canada, the Himalayas, across the entire mass of Central Asia, and everywhere in the tropics.

Tropical glaciers

But a new study in The Cryosphere, the journal of the European Geosciences Union, is one of the first to examine in detail precisely what this retreat could mean for the human communities in Bolivia, home to one-fifth of the world’s tropical glaciers.

Researchers from two British universities and a Bolivian colleague examined NASA satellite images of the region and found that the area of the Bolivia Cordillera Oriental normally covered by glaciers fell from 530 square kilometres in 1986 to about 300 sq km in 2014 − a shrinkage of more than two-fifths.

They then turned to the glacial lakes − bodies of water left behind as a glacier retreats. Some are in natural dips in the bedrock, some are accidentally dammed behind walls of glacial debris.

All such lakes are precarious: rockfalls, earthquakes and avalanches can breach them or tip water from them to create a dangerous downstream flow.

We mapped hundreds of lakes,” says Simon Cook, senior lecturer in physical geography at Manchester Metropolitan University, who led the study.

Some lakes are very small and pose little risk. Others are very large, but there’s little or no possibility that they would drain catastrophically. Others are large enough to create a big flood, and sit beneath steep slopes or steep glaciers, and could be dangerous.”

Studies such as these are a demonstration that climate change is happening, and that science can deliver practical help to communities in the path of potential disaster or economic stress.

Most glaciers will be gone or much diminished
by the end of the century – so where will the water come from in the dry season?”

Civil engineers, geographers, conservationists and hydraulic engineers are no longer simply warning about the hazards of climate change. They have begun to identify the communities most vulnerable to flooding, the hazards to local biodiversity as forests and grasslands begin to feel the heat, and the cities most at risk from routine coastal flooding as sea levels rise. and the US states that must start planning now for future power disruption as a consequence of drought.

Meltwater matters to mountain communities. It supplies the drive for hydroelectric power and it delivers clean drinking water to the cities and irrigation for crops in the dry season.

Reservoirs at risk

Through the year, the 2.3 million people in the Bolivian cities of La Paz and El Alto get 15% of their water from glacial supplies; in the dry season, this figure doubles. Glacial meltwater also keeps regional rivers and lakes topped up. So as the glaciers retreat and the body of surviving ice dwindles, some of these reservoirs, too, are at risk.

The researchers pinpointed 25 lakes as potentially dangerous. Even the smallest, were it to drain completely, would tip a peak flow of 600 cubic metres of water a second down the hillside. The largest could discharge 125,000 cubic metres − 50 times the volume of an Olympic swimming pool − every second.

A glacial lake outburst in 2009 killed farm animals, destroyed crops and washed away a road, leaving villagers isolated for months.

Dr Cook says: “We considered that a lake was dangerous if there were settlements or infrastructure down-valley from the lake, and if the slopes and glaciers around the lake were very steep, meaning that they could shed ice or snow or rock into the lake, which would cause it to overtop and generate a flood – a bit like jumping into a swimming pool, but on a much bigger scale.

Most glaciers will be gone or much diminished by the end of the century – so where will the water come from in the dry season?

Big cities like La Paz are partially dependent on meltwater from glaciers. But little is known about potential water resource stress in more remote areas. Much more work needs to be done on this issue.” Climate News Network

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Satellite mapping shows ice caps’ faster melt rate

Scientists have been able to measure more accurately than ever the thickness of the world’s major ice caps – revealing that melting is causing the loss of 500 cubic kms of ice annually. LONDON, 1 September, 2014 − German researchers have established the height of the Greenland and Antarctic ice caps with greater precision than ever before. And the new maps they have produced show that the ice is melting at an unprecedented rate. The maps, produced with a satellite-mounted instrument, have elevation accuracies to within a few metres. Since Greenland’s ice cap is more than 2,000 metres thick on average, and the Antarctic bedrock supports 61% of the planet’s fresh water, this means that scientists can make more accurate assessments of annual melting. Dr Veit Helm and other glaciologists at the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, report in the journal The Cryosphere that, between them, the two ice sheets are now losing ice at the unprecedented rate of 500 cubic kilometres a year.

Big picture

The measurements used to make the maps were taken by an instrument aboard the European Space Agency’s orbiting satellite CryoSat-2. The satellite gets closer to the poles − to 88° latitude − than any previous mission and traverses almost 16 million sq km of ice, adding an area of ice the size of Spain to the big picture of change and loss in the frozen world. CryoSat-2’s radar altimeter transmitted 7.5 million measurements of Greenland and 61 million of Antarctica during 2012, enabling glaciologists to work with a set of consistent measurements from a single instrument. Over a three-year period, the researchers collected 200 million measurements in Antarctica and more than 14 million in Greenland. They were able to study how the ice sheets changed by comparing the data with measurements made by NASA’s ICESat mission.

More complex

Greenland’s volume of ice is being reduced at the rate of 375 cubic km a year. In Antarctica, the picture is more complex as the West Antarctic ice sheet is losing ice rapidly, but is growing in volume in East Antarctica. Overall, the southern continent − 98% of which is covered with ice and snow − is losing 125 cubic km a year. These are the highest rates observed since researchers started making satellite observations 20 years ago. “Since 2009, the volume loss in Greenland has increased by a factor of about two, and the West Antarctic ice sheet by a factor of three,” said Angelika Humbert, one of the report’s authors. − Climate News Network

Scientists have been able to measure more accurately than ever the thickness of the world’s major ice caps – revealing that melting is causing the loss of 500 cubic kms of ice annually. LONDON, 1 September, 2014 − German researchers have established the height of the Greenland and Antarctic ice caps with greater precision than ever before. And the new maps they have produced show that the ice is melting at an unprecedented rate. The maps, produced with a satellite-mounted instrument, have elevation accuracies to within a few metres. Since Greenland’s ice cap is more than 2,000 metres thick on average, and the Antarctic bedrock supports 61% of the planet’s fresh water, this means that scientists can make more accurate assessments of annual melting. Dr Veit Helm and other glaciologists at the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, report in the journal The Cryosphere that, between them, the two ice sheets are now losing ice at the unprecedented rate of 500 cubic kilometres a year.

Big picture

The measurements used to make the maps were taken by an instrument aboard the European Space Agency’s orbiting satellite CryoSat-2. The satellite gets closer to the poles − to 88° latitude − than any previous mission and traverses almost 16 million sq km of ice, adding an area of ice the size of Spain to the big picture of change and loss in the frozen world. CryoSat-2’s radar altimeter transmitted 7.5 million measurements of Greenland and 61 million of Antarctica during 2012, enabling glaciologists to work with a set of consistent measurements from a single instrument. Over a three-year period, the researchers collected 200 million measurements in Antarctica and more than 14 million in Greenland. They were able to study how the ice sheets changed by comparing the data with measurements made by NASA’s ICESat mission.

More complex

Greenland’s volume of ice is being reduced at the rate of 375 cubic km a year. In Antarctica, the picture is more complex as the West Antarctic ice sheet is losing ice rapidly, but is growing in volume in East Antarctica. Overall, the southern continent − 98% of which is covered with ice and snow − is losing 125 cubic km a year. These are the highest rates observed since researchers started making satellite observations 20 years ago. “Since 2009, the volume loss in Greenland has increased by a factor of about two, and the West Antarctic ice sheet by a factor of three,” said Angelika Humbert, one of the report’s authors. − Climate News Network

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No way back for West Antarctic glaciers

Satellite data analysis reveals the ominous news that the melting glaciers of West Antarctica have passed the ‘point of no return’ as the southern hemisphere gets warmer LONDON, 22 May – The glaciers of the West Antarctic may be in irreversible retreat, according to the evidence of satellite data analysed by scientists at the US space agency Nasa. The study of 19 years of data, due to be reported in the journal Geophysical Research Letters, confirms the ominous news that the southern hemisphere is not just warming − it is that it is warming in a way that speeds up the melting of the West Antarctic glaciers. Long ago, glaciologists began to wonder whether the West Antarctic ice sheet was inherently unstable. The water locked in the ice sheet in the Amundsen Sea region – the area the Nasa researchers examined − is enough to raise global sea levels by more than a metre. If the whole West Antarctic ice sheet turned to water, sea levels would rise by at least five metres.

Steady change

What the latest research has revealed is a steady change in the glacial grounding line, which is the point in a glacier’s progress towards the sea where its bottom no longer scrapes on rock but starts to float on water. It is in the nature of a glacier to flow towards the sea, and at intervals to calve an iceberg that will then float away and melt. The puzzle for scientists has been to work out whether this process has begun to accelerate. Eric Rignot, a glaciologist at the Nasa Jet Propulsion Laboratory and the University of California, Irvine, thinks it has. He and his research partners believe that European Space Agency satellite data has recorded the points at which the grounding lines can be identified in a series of West Antarctic glaciers monitored between 1992 and 2011, as the glaciers flexed in response to the movement of tides. All the grounding lines had retreated upstream, away from the sea − some by more than 30 kilometres. The grounding lines are all buried under hundreds of metres of ice, and are difficult to identify. The shift of ice in response to tidal ebb and flow provides an important clue. It also signals an acceleration of melting, because it is the glacier’s slowness that keeps the sea levels static. As it inches towards the sea, there is time for more snow and ice to pile up behind it.

Speeds up

But if the water gets under the ice sheet, it reduces friction and accelerates the passage of frozen water downstream. So the whole glacier speeds up, and the grounding line moves yet further upstream. Something similar has been reported from the glaciers of Greenland. And once the process starts, there is no obvious reason why it would stop. The melting will still be slow, but the latest evidence indicates that it seems to be inexorable. “We’ve passed the point of no return,” Prof Rignot says. “At current melt rates, these glaciers will be history within a few hundred years. “The collapse of this sector of West Antarctica appears to be unstoppable. The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.” – Climate News Network

Satellite data analysis reveals the ominous news that the melting glaciers of West Antarctica have passed the ‘point of no return’ as the southern hemisphere gets warmer LONDON, 22 May – The glaciers of the West Antarctic may be in irreversible retreat, according to the evidence of satellite data analysed by scientists at the US space agency Nasa. The study of 19 years of data, due to be reported in the journal Geophysical Research Letters, confirms the ominous news that the southern hemisphere is not just warming − it is that it is warming in a way that speeds up the melting of the West Antarctic glaciers. Long ago, glaciologists began to wonder whether the West Antarctic ice sheet was inherently unstable. The water locked in the ice sheet in the Amundsen Sea region – the area the Nasa researchers examined − is enough to raise global sea levels by more than a metre. If the whole West Antarctic ice sheet turned to water, sea levels would rise by at least five metres.

Steady change

What the latest research has revealed is a steady change in the glacial grounding line, which is the point in a glacier’s progress towards the sea where its bottom no longer scrapes on rock but starts to float on water. It is in the nature of a glacier to flow towards the sea, and at intervals to calve an iceberg that will then float away and melt. The puzzle for scientists has been to work out whether this process has begun to accelerate. Eric Rignot, a glaciologist at the Nasa Jet Propulsion Laboratory and the University of California, Irvine, thinks it has. He and his research partners believe that European Space Agency satellite data has recorded the points at which the grounding lines can be identified in a series of West Antarctic glaciers monitored between 1992 and 2011, as the glaciers flexed in response to the movement of tides. All the grounding lines had retreated upstream, away from the sea − some by more than 30 kilometres. The grounding lines are all buried under hundreds of metres of ice, and are difficult to identify. The shift of ice in response to tidal ebb and flow provides an important clue. It also signals an acceleration of melting, because it is the glacier’s slowness that keeps the sea levels static. As it inches towards the sea, there is time for more snow and ice to pile up behind it.

Speeds up

But if the water gets under the ice sheet, it reduces friction and accelerates the passage of frozen water downstream. So the whole glacier speeds up, and the grounding line moves yet further upstream. Something similar has been reported from the glaciers of Greenland. And once the process starts, there is no obvious reason why it would stop. The melting will still be slow, but the latest evidence indicates that it seems to be inexorable. “We’ve passed the point of no return,” Prof Rignot says. “At current melt rates, these glaciers will be history within a few hundred years. “The collapse of this sector of West Antarctica appears to be unstoppable. The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.” – Climate News Network

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E. Antarctic ice basin ‘may be at risk’

The East Antarctic ice sheet is thought by most scientists to be stable. But a German team says it has found how part of it could in time melt unstoppably. LONDON, 4 May – Part of the East Antarctic ice sheet may be less stable than anyone had realised, researchers based in Germany have found. Writing in Nature Climate Change, two scientists from the Potsdam Institute for Climate Impact Research (PIK) say the melting of quite a small volume of ice on the East Antarctic shore could ultimately trigger a discharge of ice into the ocean which would result in unstoppable sea-level rise for thousands of years ahead. Their findings, which they say amount to the discovery of a hitherto overlooked source of sea level rise, appear unlikely to happen any time soon. They are based on computer simulations of the Antarctic ice flow using improved data of the ground profile beneath the ice sheet. “East Antarctica’s Wilkes Basin is like a bottle on a slant,” said Matthias Mengel, the lead author of the study. “Once uncorked, it empties out.” The basin is the largest region of marine ice on rocky ground in East Antarctica. At the moment a rim of ice at the coast holds the ice behind it in place, like a cork holding back the contents of a bottle. The air over Antarctica remains cold, but oceanic warming can cause the ice on the coast to melt. This could make the relatively small “cork” disappear. Once it had gone, the result would be a long-term sea level rise of three to four metres. “The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork,” says the study’s co-author, Anders Levermann. “Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk.”

Stability ‘over-estimated’

Levermann is a lead author of the sea-level change chapter of the most recent scientific assessment report by the Intergovernmental Panel on Climate Change, the IPCC. Its report, published in September 2013, says Antarctica’s total sea level contribution could be up to 16 centimetres during this century. “If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far,” says Levermann. Melting would cause the retreat of the grounding line, where the ice on the solid continental landmass meets the sea and starts to float. The rocky ground beneath the ice in the Wilkes Basin forms a huge valley below sea-level which slopes downwards as it heads inland. When the grounding line retreats from its current position on a ridge into the valley, the rim of the ice facing the ocean becomes higher than before. More ice is then pushed into the sea, eventually breaking off and melting. And the warmer it gets, the faster this happens. For all the ice in the Wilkes Basin to be lost in this way would take 5,000-10,000 years, the simulations showed. But once it had started, the discharge of ice would slowly but relentlessly continue until the whole basin was empty, even if the climate ceased to warm.

Unavoidable consequences

“This is the underlying issue here”, said Matthias Mengel. “By emitting more and more greenhouse gases we might trigger responses now that we may not be able to stop in the future.” He told the Climate News Network: “While the sparse existing observations do not indicate warmer water inflow towards the Wilkes ice sheet margin at present, there is no reason why changes similar to those in West Antarctica could not also occur here.” The possibility remains a distant prospect. Mengel said some simulations produced the warm ocean conditions needed to remove the ice cork within the next 200 years, but It would take around 2,000 years to raise global sea levels by one metre. He added: “The issue is that this would then be unstoppable…We have detected a new and previously overlooked source of sea level rise, therefore these numbers have to be added to the present sea level rise projections of the IPCC. “Sea level as projected for the forthcoming centuries is already potentially devastating for many coastal areas around the globe. Every centimetre of sea level rise on top of these projections is even more significant.” – Climate News Network

The East Antarctic ice sheet is thought by most scientists to be stable. But a German team says it has found how part of it could in time melt unstoppably. LONDON, 4 May – Part of the East Antarctic ice sheet may be less stable than anyone had realised, researchers based in Germany have found. Writing in Nature Climate Change, two scientists from the Potsdam Institute for Climate Impact Research (PIK) say the melting of quite a small volume of ice on the East Antarctic shore could ultimately trigger a discharge of ice into the ocean which would result in unstoppable sea-level rise for thousands of years ahead. Their findings, which they say amount to the discovery of a hitherto overlooked source of sea level rise, appear unlikely to happen any time soon. They are based on computer simulations of the Antarctic ice flow using improved data of the ground profile beneath the ice sheet. “East Antarctica’s Wilkes Basin is like a bottle on a slant,” said Matthias Mengel, the lead author of the study. “Once uncorked, it empties out.” The basin is the largest region of marine ice on rocky ground in East Antarctica. At the moment a rim of ice at the coast holds the ice behind it in place, like a cork holding back the contents of a bottle. The air over Antarctica remains cold, but oceanic warming can cause the ice on the coast to melt. This could make the relatively small “cork” disappear. Once it had gone, the result would be a long-term sea level rise of three to four metres. “The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork,” says the study’s co-author, Anders Levermann. “Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk.”

Stability ‘over-estimated’

Levermann is a lead author of the sea-level change chapter of the most recent scientific assessment report by the Intergovernmental Panel on Climate Change, the IPCC. Its report, published in September 2013, says Antarctica’s total sea level contribution could be up to 16 centimetres during this century. “If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far,” says Levermann. Melting would cause the retreat of the grounding line, where the ice on the solid continental landmass meets the sea and starts to float. The rocky ground beneath the ice in the Wilkes Basin forms a huge valley below sea-level which slopes downwards as it heads inland. When the grounding line retreats from its current position on a ridge into the valley, the rim of the ice facing the ocean becomes higher than before. More ice is then pushed into the sea, eventually breaking off and melting. And the warmer it gets, the faster this happens. For all the ice in the Wilkes Basin to be lost in this way would take 5,000-10,000 years, the simulations showed. But once it had started, the discharge of ice would slowly but relentlessly continue until the whole basin was empty, even if the climate ceased to warm.

Unavoidable consequences

“This is the underlying issue here”, said Matthias Mengel. “By emitting more and more greenhouse gases we might trigger responses now that we may not be able to stop in the future.” He told the Climate News Network: “While the sparse existing observations do not indicate warmer water inflow towards the Wilkes ice sheet margin at present, there is no reason why changes similar to those in West Antarctica could not also occur here.” The possibility remains a distant prospect. Mengel said some simulations produced the warm ocean conditions needed to remove the ice cork within the next 200 years, but It would take around 2,000 years to raise global sea levels by one metre. He added: “The issue is that this would then be unstoppable…We have detected a new and previously overlooked source of sea level rise, therefore these numbers have to be added to the present sea level rise projections of the IPCC. “Sea level as projected for the forthcoming centuries is already potentially devastating for many coastal areas around the globe. Every centimetre of sea level rise on top of these projections is even more significant.” – Climate News Network