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Greenland’s icecap loses stability

April 13, 2014 in Arctic, Glaciers, Greenland, Ice Loss, Sea level rise, Warming

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The calving front of the Jakobshaven Glacier in western Greenland in April 2012 Image: NASA ICE via Wikimedia Commons

The calving front of the Jakobshaven Glacier in western Greenland in April 2012
Image: NASA ICE via Wikimedia Commons

By Tim Radford

Greenland is losing ice from part of its territory at an accelerating rate, suggesting that the edges of the entire ice cap may be unstable.

LONDON, 13 April – Greenland – the largest terrestrial mass of ice in the northern hemisphere – may be melting a little faster than anyone had guessed.

A region of the Greenland ice sheet that had been thought to be stable is undergoing what glaciologists call “dynamic thinning”. That is because the meltwater from the ice sheet is getting into the sea, according to a study in Nature Climate Change.

In short, Greenland’s contribution to sea level rise has been under-estimated, and oceanographers may need to think again about their projections.

Shfaqat Khan from the Technical University of Denmark and colleagues used more than 30 years of surface elevation measurements of the entire ice sheet to discover that overall loss is accelerating. Previous studies had identified melting of glaciers in the island’s south-east and north-west, but the assumption had been that the ice sheet to the north-east was stable.

Four times as fast

It was stable, at least until about 2003. Then higher air temperatures set up the process of so-called dynamic thinning. Ice sheets melt every Arctic summer, under the impact of extended sunshine, but the slush on the glaciers tends to freeze again with the return of the cold and the dark, and since under historic conditions glaciers move at the proverbial glacial pace, the loss of ice is normally very slow.

But global warming, triggered by rising levels of greenhouse gases in the atmosphere, has changed all that. Greenland’s southerly glaciers have been in retreat and one of them, Jakobshavn Isbrae, is now flowing four times faster than it did in 1997.
Now the Danish-led team has examined changes linked to the 600 kilometre-long Zachariae ice stream in the north-east.

This has retreated by about 20 kms in the last decade, whereas Jakobshavn has retreated about 35 kms in 150 years. The Zachariae stream drains around one-sixth of the Greenland ice sheet, and because warmer summers have meant significantly less sea ice in recent years, icebergs have more easily broken off and floated away, which means that the ice stream can move faster. The researchers used satellite studies to measure ice loss.

“North-east Greenland is very cold. It used to be considered the last stable part of the Greenland ice sheet,” said one of the team, Michael Bevis of Ohio State University in the US.

Deep impacts

“This study shows that ice loss in the north-east is now accelerating. So now it seems that all of the margins of the Greenland ice sheet are unstable.”

The scientists used a GPS network to calculate the loss of ice. Glacial ice presses down on the bedrock below it: when the ice melts, the bedrock rises in response to the drop in pressure, and sophisticated satellite measurements can deliver enough information to help scientists put a figure on the loss of ice.

They calculate that between April 2003 and April 2012, the region was losing ice at the rate of 10 billion tons a year.

“This implies that changes at the margin can affect the mass balance deep in the centre of the ice sheet,” said Dr Khan. Sea levels are creeping up at the rate of 3.2 mm a year. Until now, Greenland had been thought to contribute about half a mm. The real figure may be significantly higher. – Climate News Network

Greenland’s fastest glacier picks up pace

February 6, 2014 in Arctic, European Space Agency, Glaciers, Greenland, Ice Loss, Lakes, Sea level rise

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An iceberg calved from the rapidly accelerating Jakobshavn Isbræ floats in Greenland's Disko Bay Image: Courtesy of Ian Joughin, PSC/APL/UW

An iceberg calved from the rapidly accelerating Jakobshavn Isbræ floats in Greenland’s Disko Bay
Image: Courtesy of Ian Joughin, PSC/APL/UW

By Tim Radford

Research from the Arctic shows Greenland’s fastest-flowing glacier has doubled its summer flow pace in a decade, and ice cover on Alaskan lakes is declining.

LONDON, 6 February – A fast-moving Arctic glacier which has earned a place in history is now accelerating even more quickly. The Jakobshavn Isbrae (the Danish word for glacier) is a massive river of ice from the Greenland ice sheet to an Atlantic ocean fjord and is thought – there is no way of proving this – to be the source of the giant iceberg that sank the Titanic in 1912.

According to research published in the European Geosciences Union journal The Cryosphere, summer flow speeds have doubled yet again since a Nasa measurement in 2003. And that in turn represented a doubling of flow speeds since 1997.

The Jakobshavn glacier is Greenland’s fastest-flowing glacier. It now moves at 17 kilometres a year. That works out at 46 metres a day. With accelerations like this, phrases like “glacial pace” may no longer serve as clichés of lethargic movement. These speeds are recorded in the summer, when all glaciers are more likely to be a bit friskier. But even when averaged over the whole year, the glacier’s flow has accelerated threefold since the 1990s.

Icebergs “calve” from glaciers – they break off and drift out to sea. The Arctic ice sheet is thinning, and most of the planet’s glaciers are retreating as climates warm, so the Jakobshavn glacier is carrying less ice, at a faster rate, over shorter distances than ever before, and by the end of the century could have shifted 50 kilometres upstream. But right now it is also contributing to sea level rise at a faster rate.

“We know that from 2000 to 2010 this glacier alone increased sea level by about 1mm”, said Ian Joughin, of the Polar Science Centre at the University of Washington, who led the research. “With the additional speed it will likely contribute a bit more than this over the next decade.”

The scientists used satellite data to measure the rate of summer change in Greenland. But other satellite radar imagery has begun to reveal an ominous picture of change elsewhere in the Arctic, on the north slope of Alaska. Even during the winter months, ice on the lakes of Alaska has begun to decline. Warmer climate conditions means thinner cover on shallow lakes and a smaller fraction that freeze entirely during the winter months.

“We were stunned to observe such a dramatic ice decline during a period of only 20 years”

Cristina Surdu of the University of Waterloo in Canada and colleagues report in The Cryosphere that there has been a 22% fall in grounded ice – frozen from surface to lakebed – between 1991 and 2011.

They expected to find a decline in ice thickness when they embarked on a study of radar observations of 402 lakes near Barrow in Alaska from the European earth resources satellites ERS-1 and ERS-2. That was because they already had temperature and precipitation records from Barrow dating back five decades.

Freeze dates in the region are now occurring on average six days later than in the past, and the ice is breaking up on average around 18 days earlier.

“At the end of the analysis, when looking at trend analysis results, we were stunned to observe such a dramatic ice decline during a period of only 20 years”, Surdu said. – Climate News Network

Ocean warming narrows climate options

September 28, 2013 in Antarctic, Arctic, Climate, Global Ocean Commission, Greenland, Marine ecology, Ocean acidification, Polar ice, Sea level rise

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Sunrise at Southwold in eastern England: What is happening in the deep oceans? Image: Brenda and Ken Bent via Wikimedia Commons

Sunrise at Southwold in eastern England: What is happening in the deep oceans?
Image: Brenda and Ken Bent via Wikimedia Commons

Professor Chris Rapley is a former director of both the British Antarctic Survey and  the Science Museum in London. What the IPCC’s Fifth Assessment Report, AR5, says about the oceans alarms him.

LONDON, 28 September – The messages are ever clearer: climate change is real, we humans are the driver, and we need to act resolutely and soon to reduce the risk of serious disruption.

The IPCC’s latest report took over 250 experts from 39 countries to sift 9,000 pieces of scientific research and address over 54,000 comments under the close scrutiny of 190 governments. The result: a fresher and sharper image of the physical state of our planet and the changes it is undergoing.

It confirms that each of the most recent three decades has been warmer than its predecessor and that the change – almost 1°C since the beginning of the last century – is significant on a timescale of ten thousand years.

In the context of an unabated planetary energy imbalance, and evidence that the 93% of the energy build-up taken up by the oceans continues to accumulate, the recent slow-down in the rise of surface temperatures, much heralded by the climate dismissers, appears a minor and temporary fluctuation.

In the meantime, the melting and retreat of polar ice shocks experts such as myself – with the loss of ice from Greenland and Antarctica both having increased by a factor of 5-6 over the decades 1990-1999 and 2000-2009.

“…we are fast losing the possibility of restricting warming to 2°C.”

The consequence? In combination with ocean thermal expansion, an accelerating rise in global mean sea level, currently running at 35 cm per century. This is already approaching one third of the rate sustained for 10,000 years during the transition from the last Ice Age to the current warm period, when sea level rose by 120 metres.

The predictions? That we are fast losing the possibility of restricting warming to 2°C. We have at most half a trillion tons of carbon left that can be burned, after which we will be committed to temperature rises outside those experienced by the planet for hundreds of thousands of years.

The scientists have done their job; now is the time for politicians to take a lead, and everyone to act.

Professor Chris Rapley CBE
Department of Earth Sciences
University College London
 

 

Note: The Global Ocean Commission says the IPCC report “shows that the ocean is shielding humanity from climate change impacts at significant cost to its own health”. Specifically, AR5 says:

- the upper part of the ocean is warming by about 0.1°C per decade
– the deep ocean is warming too, and will continue to do so for centuries even if emissions are curbed immediately
– sea levels are rising, currents are changing, the rapid shrinking of Arctic sea ice is freshening water around the region, and concentrations of dissolved oxygen are declining
– acidification will make up to half of the Arctic ocean uninhabitable for shelled animals by 2050.Climate News Network

The IPCC’s Fifth Assessment Report

September 27, 2013 in Antarctic, Arctic, Climate, Extreme weather, Greenhouse Gases, Greenland, Permafrost, Polar ice, Science, Sea level rise, Warming

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Vatnajökull in Iceland: The IPCC says humans are the main cause of recent warming Image: Andreas Tille via Wikimedia Commons

Vatnajökull in Iceland: The IPCC says humans are the main cause of recent warming
Image: Andreas Tille via Wikimedia Commons

By the editors

Summary for Policymakers of the Working Group I contribution to the Fifth Assessment Report

A note from the Climate News Network editors: we have prepared this very abbreviated version of the first instalment of the IPCC’s Fifth Assessment Report (AR5) to serve as an objective guide to some of the headline issues it covers. It is in no sense an evaluation of what the Summary says: the wording is that of the IPCC authors themselves, except for a few cases where we have added headings. The AR5 uses a different basis as input to models from that used in its 2007 predecessor, AR4: instead of emissions scenarios, it speaks of RCPs, representative concentration pathways. So it is not possible everywhere to make a direct comparison between AR4 and AR5, though the text does so in some cases, and at the end we provide a very short list of the two reports’ conclusions on several key issues. The language of science can be complex. What follows is the IPCC scientists’ language. In the following days and weeks we will be reporting in more detail on some of their findings.

In this Summary for Policymakers, the following summary terms are used to describe the available evidence: limited, medium, or robust; and for the degree of agreement: low, medium, or high. A level of confidence is expressed using five qualifiers: very low, low, medium, high, and very high, and typeset in italics, e.g., medium confidence. For a given evidence and agreement statement, different confidence levels can be assigned, but increasing levels of evidence and degrees of agreement are correlated with increasing confidence. In this Summary the following terms have been used to indicate the assessed likelihood of an outcome or a result: virtually certain 99–100% probability, very likely 90–100%, likely 66–100%, about as likely as not 33–66%, unlikely 0–33%, very unlikely 0–10%, exceptionally unlikely 0–1%. Additional terms (extremely likely: 95–100%, more likely than not >50–100%, and extremely unlikely 0–5%) may also be used when appropriate.

Observed Changes in the Climate System

 

Atmosphere

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased

Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.

For the longest period when calculation of regional trends is sufficiently complete (1901–2012), almost the entire globe has experienced surface warming.

In addition to robust multi-decadal warming, global mean surface temperature exhibits substantial decadal and interannual variability. Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.

As one example, the rate of warming over the past 15 years, which begins with a strong El Niño, is smaller than the rate calculated since 1951.

Changes in many extreme weather and climate events have been observed since about 1950. It is very likely that the number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale

Ocean

Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 (high confidence ). It is virtually certain that the upper ocean (0−700 m) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971.

On a global scale, the ocean warming is largest near the surface, and the upper 75 m warmed by 0.11 [0.09 to 0.13] °C per decade over the period 1971–2010. Since AR4, instrumental biases in upper-ocean temperature records have been identified and reduced, enhancing confidence in the assessment of change.

It is likely that the ocean warmed between 700 and 2000 m from 1957 to 2009. Sufficient observations are available for the period 1992 to 2005 for a global assessment of temperature change below 2000 m. There were likely no significant observed temperature trends between 2000 and 3000 m for this period. It is likely that the ocean warmed from 3000 m to the bottom for this period, with the largest warming observed in the Southern Ocean.

More than 60% of the net energy increase in the climate system is stored in the upper ocean (0–700 m) during the relatively well-sampled 40-year period from 1971 to 2010, and about 30% is stored in the ocean below 700 m. The increase in upper ocean heat content during this time period estimated from a linear trend is likely.

Cryosphere

Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent (high confidence).

The average rate of ice loss from the Greenland ice sheet has very likely substantially increased … over the period 1992–2001. The average rate of ice loss from the Antarctic ice sheet has likely increased … over the period 1992–2001. There is very high confidence that these losses are mainly from the northern Antarctic Peninsula and the Amundsen Sea sector of West Antarctica.

There is high confidence that permafrost temperatures have increased in most regions since the early 1980s. Observed warming was up to 3°C in parts of Northern Alaska (early 1980s to mid-2000s) and up to 2°C in parts of the Russian European North (1971–2010). In the latter region, a considerable reduction in permafrost thickness and areal extent has been observed over the period 1975–2005 (medium confidence).

Multiple lines of evidence support very substantial Arctic warming since the mid-20th century.

Sea Level

The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901–2010, global mean sea level rose by 0.19 [0.17 to 0.21] m.

Since the early 1970s, glacier mass loss and ocean thermal expansion from warming together explain about 75% of the observed global mean sea level rise (high confidence). Over the period 1993–2010, global mean sea level rise is, with high confidence, consistent with the sum of the observed contributions from ocean thermal expansion due to warming, from changes in glaciers, Greenland ice sheet, Antarctic ice sheet, and land water storage.

Carbon and Other Biogeochemical Cycles

The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification

From 1750 to 2011, CO2 emissions from fossil fuel combustion and cement production have released 365 [335 to 395] GtC [gigatonnes - one gigatonne equals 1,000,000,000 metric tonnes] to the atmosphere, while deforestation and other land use change are estimated to have released 180 [100 to 260] GtC.

Of these cumulative anthropogenic CO2 emissions, 240 [230 to 250] GtC have accumulated in the atmosphere, 155 [125 to 185] GtC have been taken up by the ocean and 150 [60 to 240] GtC have accumulated in natural terrestrial ecosystems.

Drivers of Climate Change

The total natural RF [radiative forcing - the difference between the energy received by the Earth and that which it radiates back into space] from solar irradiance changes and stratospheric volcanic aerosols made only a small contribution to the net radiative forcing throughout the last century, except for brief periods after large volcanic eruptions.

Understanding the Climate System and its Recent Changes

Compared to AR4, more detailed and longer observations and improved climate models now enable the attribution of a human contribution to detected changes in more climate system components.

Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.

Evaluation of Climate Models

Climate models have improved since the AR4. Models reproduce observed continental-scale surface temperature patterns and trends over many decades, including the more rapid warming since the mid-20th century and the cooling immediately following large volcanic eruptions (very high confidence).

The long-term climate model simulations show a trend in global-mean surface temperature
from 1951 to 2012 that agrees with the observed trend (very high confidence). There are, however, differences between simulated and observed trends over periods as short as 10 to 15 years (e.g., 1998 to 2012).

The observed reduction in surface warming trend over the period 1998–2012 as compared to the period 1951–2012, is due in roughly equal measure to a reduced trend in radiative forcing and a cooling contribution from internal variability, which includes a possible redistribution of heat within the ocean (medium confidence). The reduced trend in radiative forcing is primarily due to volcanic eruptions and the timing of the downward phase of the 11-year solar cycle.

Climate models now include more cloud and aerosol processes, and their interactions, than at the time of the AR4, but there remains low confidence in the representation and quantification of these processes in models.

The equilibrium climate sensitivity quantifies the response of the climate system to constant radiative forcing on multi-century time scales. It is defined as the change in global mean surface temperature at equilibrium that is caused by a doubling of the atmospheric CO2 concentration.

Equilibrium climate sensitivity is likely in the range 1.5°C to 4.5°C (high confidence), extremely unlikely less than 1°C (high confidence), and very unlikely greater than 6°C (medium confidence). The lower temperature limit of the assessed likely range is thus less than the 2°C in the AR4, but the upper limit is the same. This assessment reflects improved understanding, the extended temperature record in the atmosphere and ocean, and
new estimates of radiative forcing.

Detection and Attribution of Climate Change

Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.

It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period.

Future Global and Regional Climate Change

Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation.

It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century as global mean surface temperature rises. Global glacier volume will further decrease.

Global mean sea level will continue to rise during the 21st century. Under all RCP scenarios the rate of sea level rise will very likely exceed that observed during 1971–2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets.

Sea level rise will not be uniform. By the end of the 21st century, it is very likely that sea level will rise in more than about 95% of the ocean area. About 70% of the coastlines worldwide are projected to experience sea level change within 20% of the global mean sea level change.

Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO2 in the atmosphere (high confidence). Further uptake of carbon by the ocean will increase ocean acidification.

Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2.

A large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible on a multi-century to millennial time scale, except in the case of a large net removal of CO2 from the atmosphere over a sustained period.

Surface temperatures will remain approximately constant at elevated levels for many centuries after a complete cessation of net anthropogenic CO2 emissions. Due to the long time scales of heat transfer from the ocean surface to depth, ocean warming will continue for centuries. Depending on the scenario, about 15 to 40% of emitted CO2 will remain in the atmosphere longer than 1,000 years.

Sustained mass loss by ice sheets would cause larger sea level rise, and some part of the mass loss might be irreversible. There is high confidence that sustained warming greater than some threshold would lead to the near-complete loss of the Greenland ice sheet over a millennium or more, causing a global mean sea level rise of up to 7 m.

Current estimates indicate that the threshold is greater than about 1°C (low confidence) but less than about 4°C (medium confidence) global mean warming with respect to pre-industrial. Abrupt and irreversible ice loss from a potential instability of marine-based sectors of the Antarctic Ice Sheet in response to climate forcing is possible, but current evidence and understanding is insufficient to make a quantitative assessment.

Methods that aim to deliberately alter the climate system to counter climate change, termed geoengineering, have been proposed. Limited evidence precludes a comprehensive quantitative assessment of both Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) and their impact on the climate system.

CDR methods have biogeochemical and technological limitations to their potential on a global scale. There is insufficient knowledge to quantify how much CO2 emissions could be partially offset by CDR on a century timescale.

Modelling indicates that SRM methods, if realizable, have the potential to substantially offset a global temperature rise, but they would also modify the global water cycle, and would not reduce ocean acidification.

If SRM were terminated for any reason, there is high confidence that global surface temperatures would rise very rapidly to values consistent with the greenhouse gas forcing. CDR and SRM methods carry side effects and long-term consequences on a global scale.

Then and Now

For comparison, here are the IPCC’s projections in four key areas: from the 2013 AR5, in bold – from the 2007 AR4, in regular type

Probable temperature rise by 2100: 1.5-4°C under most scenarios – from 1.8-4°C
Sea level rise: very likely faster than between 1971 and 2010 – by 28-43 cm
Arctic summer sea ice disappears: very likely it will continue to shrink and thin – in second half of century
Increase in heat waves: very likely to occur more frequently and last longer – increase very likely

Cruise will weigh Arctic drilling risks

August 19, 2013 in Economy, Polar ice, Technology, Wildlife

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Preparations for Arctic exploitation go on apace: the cruise should help them Image: T J Guiton via Wikimedia Commons

Preparations for Arctic exploitation go on apace: the cruise should help them
Image: T J Guiton via Wikimedia Commons

By Alex Kirby

A research cruise to the coast of Greenland is aiming to extend understanding of Arctic sea ice to aid attempts to exploit the region as the planet warms.

LONDON, 19 August – An ambitious attempt to learn more about what is happening to the Arctic sea ice is getting under way with the start of a two-week research cruise to the waters off the north-eastern coast of Greenland.

The scientists will measure a range of parameters of the sea ice, icebergs and how they interact with their ship, the Swedish polar icebreaker Oden. The voyage, coming at the end of the northern hemisphere summer, coincides with the lowest levels of ice in the Arctic

The researchers are returning to an area they studied last year, allowing them to retrieve instruments moored underwater since then which have been collecting ice and ocean current data in the meantime.

This will help the team to learn more about the potential impact of ice on shipping and other structures which may use the area, and to prepare the way for the exploitation of the Arctic’s mineral wealth.

Five marine mammal researchers will also be aboard the Oden to conduct acoustic research and combine conventional observations with more high-tech approaches.

The multinational group sailed from Longyearbyen in the Svalbard archipelago. It includes Arctic offshore engineering scientists from the Norwegian University of Science and Technology (NTNU) and colleagues from nine international universities and companies, and from the Swedish Polar Research Secretariat.

“The offshore area north-east of Greenland is a very interesting place for us, because it is a place with multi-year ice and with quite heavy drift of sea ice and icebergs”, says Raed Lubbad, the cruise leader.

He is an associate professor based at SAMCoT, NTNU’s centre for Sustainable Arctic Marine and Coastal Technology, and says SAMCoT “works with the development of robust technology necessary for sustainable exploration and exploitation of the valuable and vulnerable Arctic region.”

Retrieval conundrum

The US space agency NASA said last year that the older, thicker multi-year Arctic sea ice was disappearing faster than the younger ice. “The rapid disappearance of older ice makes Arctic sea ice even more vulnerable to further decline in the summer”, said Joey Comiso, senior scientist at NASA’s Goddard Space Flight Center.

One of Oden’s most challenging tasks will be to retrieve four underwater installations deployed last year, whose instruments include upward-looking sonar and acoustic doppler current profilers (ACDPs), which measure water currents.

The ship will send a signal to the instruments which tells them to release their moorings and pop up to the surface – but if there is too much ice over the area where they are it will be hard to find them, or to retrieve them.

“These are very important”, Lubbad says. “They give us long time series data on ice thickness, drift and sea currents that enable us to quantify the physical environment.”

Ice ridges

The team says some of the most interesting data from the instruments concerns the frequency and thickness of ice ridges. An ice ridge forms when two ice sheets are pressed against each other and consists of accumulated pieces of broken ice, so that its total thickness is much greater than that of the original ice.

“These ice ridges typically produce the highest loads on structures”, Lubbad says. “Knowing how thick these ridges are, how fast they drift and how frequent they are is very important for the design of ships and floating structures.”

The marine mammal biologists will not only be able to study a relatively remote area but also to work with colleagues in identifying ice features that can be important habitat for marine mammals such as polar bears.

They will use hydrophones to listen for animals underwater, as well as an infrared camera which will enable to them to find animals that might be difficult to detect visually.

The 32 participants are from 14 countries and come from universities in Norway, the Netherlands, Russia, Spain and the US, and from Norwegian and Canadian companies. – Climate News Network

Earth’s inner heat melts Greenland ice

August 13, 2013 in Glaciers, Greenland, Science, Sea level rise

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The edge of the Greenland icesheet, near Kangerlussuaq, Greenland. Image: L. Chang

The edge of the icesheet, near Kangerlussuaq, Greenland.
Image: L. Chang via wikimedia commons

By Tim Radford

Greenland’s icesheet is melting, at the surface and at its base. Don’t worry: it isn’t global warming that is thawing the base of the Greenland ice cap. It is just the normal warmth of an active rocky planet. 

 LONDON, 13 August – Greenland is the largest single reservoir of ice in the northern hemisphere and, with Antarctica, a big contributor to sea level rise. The island sheds 227 billion tonnes of ice every year, and this alone lifts the mean ocean levels by 0.7mm (the seas are rising by 3mm each year in total). Alexey Petrunin and Irina Rogozhina of the GFZ German Research Centre in Potsdam report in Nature Geoscience on a new approach to the great Greenland riddle: what is happening to the ice?

They coupled an ice/climate model that should simulate what happens as temperatures shift, and linked it to a thermo-mechanical model of the planet’s crust and upper mantle far below the island.

Geophysicists call this region the lithosphere: temperatures below the surface increase steadily with depth, and it is the heat from the mantle that powers sea-floor spreading and sends continents drifting across the globe on tectonic plates. Heat from the lithosphere is also the driver, around the world, for boiling mud pools, hot springs, geysers, volcanic discharges and unexpectedly wet, slippery rocks at the base of glaciers.

But there is a catch for scientists who try to model the processes in the lithosphere, especially in heavily glaciated regions. The colossal weight of ice presses down on the rocky crust, and deforms it. The mountains of Scandinavia, once covered by thick glaciers during the ice age, are still rebounding as the depressed lithosphere springs back into shape. What the Potsdam scientists had to do was adjust the model to square with temperature differences observed at separate boreholes and variations in seismic and magnetic data.

Thin rocks and thick ice

At the bottom, Greenland’s subglacial rocks can be warm in one place, cold in another – and very thin, for a 2 billion year old slab of crust, “anomalously thin” say the Potsdam team. This lithosphere heat  would be of no great consequence  if Greenland were exposed rock, but because it bears a permanently insulating sheet of thick ice, the heat flow from deep in the Earth becomes an important part of the pattern of change.

They ran their model to cover a simulated three million-year span, and settled the argument: the dynamics of the Greenland ice sheet are affected by the heat flow from the planet’s interior. “Our model calculations are in good agreement with the measurements,” said Dr Petrunin. “Both the thickness of the ice sheet as well as the temperature at its base are depicted very accurately.”

Now researchers know a bit more about the dynamics of the ice sheet, they can start to calculate the rate of melting in the decades ahead, and in the Proceedings of the National Academy of Sciences, a large group of international scientists, led by Sarah Shannon of the University of Bristol in the United Kingdom, has been trying to make sense of the flow of surface and subterranean meltwater from the Greenland ice sheet.

The concern is that the melting at the base could lubricate the movement of the glaciers and possibly accelerate the loss of ice as great blocks of the stuff hit the coast and calve as icebergs. They conclude that it could, but there’s no evidence to say that it is doing so right now.  For the moment, on the evidence of simulations based on climate models, and on observations so far, they calculate that Greenland’s contribution to sea level rise from basal melting will be small: no more than 5%. – Climate News Network

Scientists mull Arctic’s slow CO2 loss

July 28, 2013 in Permafrost, Vegetation changes, Warming

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Ice-rich permafrost sample collected in Zackenberg, NE Greenland in the summer of 2012. Image: Bo Elberling, CENPERM, Center for Permafrost, University of Copenhagen

Ice-rich permafrost sample collected in Zackenberg, NE Greenland in the summer of 2012.
Image: Bo Elberling, CENPERM, Center for Permafrost, University of Copenhagen

By Tim Radford

The Arctic permafrost thaws each year, but – to the surprise of scientists from Denmark – in some areas it is not releasing the carbon dioxide it contains nearly as fast as they had expected.

LONDON, 28 July – Think of permafrost as a slush fund of so-far uncertain value. The levels of Arctic permafrost that thaw each year and freeze again are growing at depths of 1cm a year, but the carbon locked away in the soils is – so far – not being released at an accelerating rate.

This is good news for climate change worriers, but only for the time being. Bo Elberling of the Centre for Permafrost at the University of Copenhagen in Denmark and colleagues report in Nature Climate Change that the soggy summer soils of Greenland, Svalbard and Canada where they have taken samples are not releasing carbon dioxide at the rate some had feared.

But the results are based on preliminary research and they still have to work out why carbon release is so slow – and whether it will remain slow.

The “active permafrost” is a natural feature of sub-Arctic life: there is a shallow thaw each summer, plants flower, insects arrive, migrating birds follow the insects, grazing animals forage, predators seize a chance to fatten, and then winter returns with the shorter days.

But of all the climate zones, the Arctic is responding fastest to global warming, with a startling loss of sea ice; the glaciers, too, are in retreat almost everywhere.

Professor Elberling and colleagues have been taking measurements over the three or four months of the thaw for the last 12 years; they have also modelled changing conditions in the laboratory.

Slow decay rate

There they could change the drainage and control the temperature, and they found that a layer of thawing permafrost could lose significant quantities of carbon, as the microbes resumed the business of decay: in 70 years of such annual thaw and freeze, up to 77% of the soil carbon could turn into carbon dioxide, with serious consequences for yet further global warming.

But, they report in Nature Climate Change, that does not seem to be happening at any of the sites under test: if the water content of the thawing soils remains high, then carbon decay is very slow, and the eventual release of this carbon could take hundreds of years.

So anyone who wants to model this release will have to think about whether there is enough oxygen to speed up the release, or whether cold water will dampen the process and slow it down.

“It is thought-provoking that micro-organisms are behind the entire problem – micro-organisms which break down the carbon pool and which are apparently already present in the permafrost. One of the critical decisive factors – the water content – is in the same way linked to the original high content of ice in most permafrost samples.

“Yes, the temperature is increasing, and the permafrost is thawing, but it is, still, the characteristics of the permafrost which determine the long-term release of carbon dioxide,” says Elberling. – Climate News Network

Science still puzzles over polar ice

July 14, 2013 in Climate, Science, Warming

FOR IMMEDIATE RELEASE

Iceberg in Greenland: But hos fast is it melting? Image: Jerzy Strzelecki via W ikimedia Commons

Iceberg in Greenland: But hos fast is it melting?
Image: Jerzy Strzelecki via Wikimedia Commons

By Tim Radford

New research shows that glaciologists still cannot say for certain whether the Earth’s north and south polar ice is melting faster as the years pass.

LONDON, 14 July – Here is a non-conclusion: after nine years of close observation, researchers still cannot be sure whether the planet is losing its ice caps at an accelerating rate.

That is because the run of data from one satellite is still not long enough to answer the big question: are Greenland and Antarctica melting because of global warming, or just blowing hot before blowing cold again in some long-term natural cycle?

The question is a serious one. If the loss of ice that seems to be happening now is really going to accelerate, then by 2100, mean sea level will rise 43 centimetres higher than the original notional prediction, and hundreds  of millions of people who live on estuaries, deltas, coral atolls and great city river basins face serious losses.

Bert Wouters, a glaciologist at the University of Bristol in the UK and the University of Colorado at Boulder, Colorado, in the US, and colleagues report in Nature Geoscience that their most up-to-date and consistent measuring system, a satellite called Grace, needs to run for a lot longer before there can be a clear answer.

Grace stands for Gravity Recovery and Climate Experiment and it measures changes in mass in the landscape over which it flies, and the biggest variations in mass come from the changes in ice cover.

The main targets of the study are the ice sheets of Greenland and Antarctica because these amount to more than 99% of the planet’s snow and ice, and were these to melt completely, sea levels would rise by 63 metres, with calamitous consequences.

Shared caution

To be sure of detecting an accelerating mass loss of give or take 10 billion tonnes a year per year, the experiment needs at least 10 years for Antarctica and perhaps 20 years for Greenland.

But the results so far are ominous. “It has become apparent that ice sheets are losing substantial amounts of ice – about 300 billion tonnes each year – and the rate at which these losses occur is increasing. Compared to the first few years of the Grace mission, the ice sheets’ contribution to sea level rise has almost doubled in recent years,” said Dr Wouters.

But he is talking, of course, of a consistent finding from one experiment: other research has shown that the melting so far is real enough. The question is: could this just be the consequence of some natural rhythm so far unidentified?

Dr Wouters’ caution is echoed through the glaciological community. “Although ice is lost beyond any doubt, the period is not long enough to state that ice loss is accelerating,” said Wolfgang Rack of the University of Canterbury in New Zealand.

“This is because of the natural variability of the credit process, snowfall, and the debit process, melting, and iceberg calving, which both control the ice sheet balance.” – Climate News Network

Greenland faces ‘modest’ but risky melt

July 10, 2013 in Arctic, Science

EMBARGOED until 1200 GMT on Wednesday 10 July

Greenland's glaciers are expected to play a smaller part in raising sea levels Image: NASA/Michael Studinger via Wikimedia Commons

Greenland’s glaciers are expected to play a smaller part in raising sea levels
Image: NASA/Michael Studinger via Wikimedia Commons

By Alex Kirby

Scientists now believe that surface melting of the Greenland ice sheet will add more to global sea levels than the island’s glaciers – and they say even a modest rise could have serious consequences.

LONDON, 10 July – Greenland’s contribution to sea-level rise between now and 2200 is likely to be relatively modest, scientists say. But they couple this with a warning against complacency over the possible consequences of even a fairly small rise.

They say the Greenland ice sheet is expected to increase its contribution to higher sea levels over the next two centuries. But there will be significant changes in the way the island loses ice as glaciers retreat.

Their findings, published in the Journal of Glaciology (Sensitivity of Greenland ice sheet projections to model formulations, by Dr Heiko Goelzer et al), suggest that ice melting from the land surface will be the dominant way of raising sea levels. Outlet glaciers, which form an ice shelf once they reach the sea and then discharge into it, are expected to play a smaller part.

The Greenland ice sheet contains enough ice to cause global sea levels to rise by more than seven metres, if it were ever to melt completely.

Changes in its total mass happen mainly because of fluctuations in melting and snowfall on its surface, and changes to the number of icebergs released from the glaciers.

Glaciers’ smaller role

Researchers from the Vrije Universiteit Brussel,, funded by Ice2sea, a European Union project, wanted to know how both surface melting and iceberg formation will evolve and affect one another.

They used a computer model which projects future ice sheet evolution with high accuracy, and found a way to generalise earlier projections about just four of Greenland’s outlet glaciers.

This let them apply the earlier findings to all calving glaciers around the Greenland ice sheet. Their results indicate a total sea-level contribution from the sheet for an average warming scenario after 100 and 200 years of 7 and 21 cm respectively.

But the balance between the two processes, melting and calving, will change considerably, so that icebergs may account for only between 6% and 18% of the total sea-level contribution after 200 years.

This matters, because variations in outlet glacier dynamics have often been suspected of being able to cause very large contributions to sea-level rise.

The glaciers will be less important in future because of their retreat back onto land, and because strongly increasing surface melting, caused by global warming, will remove ice before it can reach the sea edge.

“Sea-level rise is not about the waves chasing us up the beach. It’s about those storm and flood return periods”

Ice2sea coordinator Professor David Vaughan, of the British Antarctic Survey, said: “This scenario is no reason to be complacent. The reason the significance of calving glaciers reduces compared to surface melting is that so much ice will be lost in coming decades that many glaciers currently sitting in fjords will retreat inland to where they are no longer affected by warming seas around Greenland.”

Professor Vaughan told the Climate News Network: “The numbers we’ve come up with are roughly comparable to those the Intergovernmental Panel on Climate Change presented in its 2007 report.

“Other researchers have suggested much higher possibilities, based on projections of past changes. The big step forward here is that our work is tied to a specific, rigorous approach to modelling.

“But we can’t afford complacency. Peripheral glaciers – those not directly connected to the ice sheet – and thermal expansion of sea water could easily add up to global sea-level rise of 50 cms by 2100.

“What’s important there is not so much the rise itself, but the way it alters the return period of big storms and floods.

“If you had a 50 cm rise in the Thames estuary, downstream from London, then a storm you’d normally expect once in a thousand years could arrive every century. A rise in sea level to nearer a metre would mean you could expect that 1,000-year storm once every ten years.

“Sea-level rise is not about the waves chasing us up the beach. It’s about those storm and flood return periods. And what could happen to the Thames is the same story for many European coastlines.” – Climate News Network

More storms, more heat says WMO

July 3, 2013 in Climate, Science, Warming

EMBARGOED till 1100 GMT on Wednesday 3 July

Baffin Island: As the Arctic warms, Greenland's temperature reached 3.2C above average in 2010 Image: NASA/Michael Studinger, via \Wikimedia Commons

Baffin Island: As the Arctic warms, Greenland’s temperature reached 3.2C above average in 2010
Image: NASA/Michael Studinger, via \Wikimedia Commons

By Alex Kirby

In the first decade of this century global sea level rise increased at about double the rate of the preceding hundred years, the World Meteorological Organization says.

London, 3 July – If you think the world is warming and the weather getting nastier, you’re right, according to the United Nations agency committed to understanding weather and climate.

The World Meteorological Organization says the planet “experienced unprecedented high-impact climate extremes” in the ten years from 2001 to 2010, the warmest decade since the start of modern measurements in 1850.

Those ten years also continued an extended period of accelerating global warming, with more national temperature records reported broken than in any previous decade. Sea levels rose about twice as fast as the trend in the last century.

A WMO report, The Global Climate 2001-2010, A Decade of Climate Extremes, analyses global and regional temperatures and precipitation, and extreme weather such as the heat waves in Europe and Russia, Hurricane Katrina in the US, tropical cyclone Nargis in Myanmar, droughts in the Amazon basin, Australia and East Africa, and floods in Pakistan.

It says the decade was the warmest for both hemispheres, and for both land and ocean surface temperatures. There was a rapid decline in Arctic sea ice and accelerating loss of net mass from the Greenland and Antarctic ice sheets and from the world’s glaciers.

This melting and the thermal expansion of sea water caused global mean sea levels to rise about three millimetres annually, about double the observed 20th century trend of 1.6 mm per year. Global sea level averaged over the decade was about 20 cm higher than in 1880, the report says.

Global-average atmospheric concentrations of carbon dioxide rose to 389 parts per million in 2010, 39% higher than at the start of the industrial era in 1750. Methane rose to 1,808.0 parts per billion (158%) and nitrous oxide to 323.2 ppb (20%).

The WMO secretary-general, Michel Jarraud, said: “A decade is the minimum possible timeframe for meaningful assessments of climate change.

Clear upward trend

“WMO’s report shows that global warming accelerated in the four decades of 1971 to 2010 and that the decadal rate of increase between 1991-2000 and 2001-2010 was unprecedented.”

He added: “Rising concentrations of heat-trapping greenhouse gases are changing our climate, with far-reaching implications for our environment and our oceans, which are absorbing both carbon dioxide and heat.”

His reference to the oceans’ role as a sink for CO2 and heat is significant in the present debate about the apparent slight slow-down in the pace of atmospheric warming and the likelihood that the heat is going into the oceans instead.

Mr Jarraud said: “Natural climate variability, caused in part by interactions between our atmosphere and oceans – as evidenced by El Niño and La Niña events – means that some years are cooler than others.

“On an annual basis, the global temperature curve is not a smooth one. On a long-term basis the underlying trend is clearly in an upward direction, more so in recent times.”

The report says that between 2001 and 2010, there was no major El Niño event, which normally leads to higher temperatures (as in the then-record warm year of 1998). Much of this last decade experienced either cooling La Niña or neutral conditions, except for the 2009/2010 moderate to strong El Niño.

It says the average land and ocean-surface temperature for 2001-2010 was estimated to be 14.47°C, or 0.47°C above the 1961-1990 global average and +0.21°C above the 1991-2000 global average (with a factor of uncertainty of ± 0.1°C).

The average 1991-2000 decadal temperature was itself +0.14°C warmer than 1981-1990. Every year of this latest decade except 2008 was among the 10 warmest years on record.

Warming Greenland

The warmest year ever recorded was 2010, with a temperature estimated at 0.54°C above the 14.0°C long term average of the 1961-1990 base period, followed closely by 2005.

Greenland recorded the largest decadal temperature anomaly, at +1.71°C above the long-term average and with a temperature in 2010 of +3.2°C above average. Africa experienced warmer than normal conditions in every year of the decade.

When it came to precipitation and floods, the decade was the second wettest since 1901. Globally, 2010 was the wettest year since the start of instrumental records.

Yet the WMO says droughts affect more people than any other kind of natural disaster because of their large scale and long duration. The decade saw droughts across the world, with some of the longest and most severe in Australia (2002 and other years), East Africa (2004 and 2005, resulting in widespread loss of life) and the Amazon basin (2010).

Tropical cyclones were reported to have killed nearly 170,000 people and to have affected more than 250 million, causing economic damage of US$ 380 billion.

More than 370,000 people died during the decade as a result of extreme weather and climate conditions – heat, cold, drought, storms and floods, according to data from the Centre for Research on the Epidemiology of Disasters. This was 20% higher than 1991-2000.

But the WMO says there was a 16% decline in deaths due to storms and a 43% decline in those from floods, thanks mainly to better early warning systems and increased preparedness, and despite an increase in populations in disaster-prone areas. – Climate News Network