Previous rapid thinning of Pine Island Glacier sheds light on future Antarctic ice loss

New research, published this week in Science, suggests that the largest single contributor to global sea level rise, a glacier of the West Antarctic Ice Sheet, may continue thinning for decades to come. Geologists from the UK, USA and Germany found that Pine Island Glacier (PIG), which is rapidly accelerating, thinning and retreating, has thinned rapidly before. The team say their findings demonstrate the potential for current ice loss to continue for several decades yet.Their findings reveal that 8000 years ago the glacier thinned as fast as it has in recent decades, providing an important model for its future behaviour. The glacier is currently experiencing significant acceleration, thinning and retreat that is thought to be caused by ‘ocean-driven’ melting; an increase in warm ocean water finding its way under the ice shelf.After two decades of rapid ice loss, concerns are arising over how much more ice will be lost to the ocean in the future. Model projections of the future of PIG contain large uncertainties, leaving questions about the rate, timing and persistence of future sea level rise. Rocks exposed by retreating or thinning glaciers provide evidence of past ice sheet change, which helps scientists to predict possible future change. The geologists used highly sensitive dating techniques, pioneered by one of the team, to track the thinning of PIG through time, and to show that the past thinning lasted for several decades.Lead author Joanne Johnson from the British Antarctic Survey (BAS) said: “Our geological data show us the history of Pine Island Glacier in greater detail than ever before. The fact that it thinned so rapidly in the past demonstrates how sensitive it is to environmental change; small changes can produce dramatic and long-lasting results. Based on what we know, we can expect the rapid ice loss to continue for a long time yet, especially if ocean-driven melting of the ice shelf in front of Pine Island Glacier continues at current rates,”Professor Mike Bentley, a co-leader of the project based at Durham University said: “This paper is part of a wide range of international scientific efforts to understand the behaviour of this important glacier. The results we’re publishing are the product of long days spent sampling rocks from mountains in Antarctica, coupled to some exceptionally precise and time-consuming laboratory analyses. …

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Greenland’s fastest glacier reaches record speeds

Jakobshavn Isbr (Jakobshavn Glacier) is moving ice from the Greenland ice sheet into the ocean at a speed that appears to be the fastest ever recorded. Researchers from the University of Washington and the German Space Agency (DLR) measured the dramatic speeds of the fast-flowing glacier in 2012 and 2013.The results are published today in The Cryosphere, an open access journal of the European Geosciences Union (EGU).”We are now seeing summer speeds more than 4 times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glacier in Greenland,” says Ian Joughin, a researcher at the Polar Science Center, University of Washington and lead-author of the study.In the summer of 2012 the glacier reached a record speed of more than 17 kilometres per year, or over 46 metres per day. These flow rates are unprecedented: they appear to be the fastest ever recorded for any glacier or ice stream in Greenland or Antarctica, the researchers say.They note that summer speeds are temporary, with the glacier flowing more slowly over the winter months. But they add that even the annually averaged speedup over the past couple of years is nearly 3 times what it was in the 1990s.This speedup of Jakobshavn Isbr means that the glacier is adding more and more ice to the ocean, contributing to sea-level rise. “We know that from 2000 to 2010 this glacier alone increased sea level by about 1 mm. With the additional speed it likely will contribute a bit more than this over the next decade,” explains Joughin.Jakobshavn Isbr, which is widely believed to be the glacier that produced the large iceberg that sank the Titanic in 1912, drains the Greenland ice sheet into a deep ocean fjord on the coast of the island. At its calving front, where the glacier effectively ends as it breaks off into icebergs, some of the ice melts while the rest is pushed out, floating into the ocean. Both of these processes contribute about the same amount to sea-level rise from Greenland.As the Arctic region warms, Greenland glaciers such as Jakobshavn Isbr have been thinning and calving icebergs further and further inland. This means that, even though the glacier is flowing towards the coast and carrying more ice into the ocean, its calving front is actually retreating. In 2012 and 2013, the front retreated more than a kilometre further inland than in previous summers, the scientists write in the new The Cryosphere study.In the case of Jakobshavn Isbr, the thinning and retreat coincides with an increase in speed. …

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Underlying ocean melts ice shelf, speeds up glacier movement

Sep. 12, 2013 — Warm ocean water, not warm air, is melting the Pine Island Glacier’s floating ice shelf in Antarctica and may be the culprit for increased melting of other ice shelves, according to an international team of researchers.”We’ve been dumping heat into the atmosphere for years and the oceans have been doing their job, taking it out of the air and into the ocean,” said Sridhar Anandakrishnan, professor of geosciences, Penn State. “Eventually, with all that atmospheric heat, the oceans will heat up.”The researchers looked at the remote Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet because it has rapidly thinned and accelerated in the recent past.”It has taken years and years to do the logistics because it is so remote from established permanent bases,” said Anandakrishnan.Pine Island Glacier or PIG lies far from McMurdo base, the usual location of American research in Antarctica. Work done in the southern hemisphere’s summer, December through January 2012-13, included drilling holes in the ice to place a variety of instruments and using radar to map the underside of the ice shelf and the bottom of the ocean. Penn State researchers did the geophysics for the project and the research team’s results are reported today (Sept. 13) in Science.The ice shelf is melting more rapidly from below for a number of reasons. The oceans are warmer than they have been in the past and water can transfer more heat than air. More importantly, the terrain beneath the ice shelf is a series of channels. The floating ice in the channel has ample room beneath it for ocean water to flow in. The water melts some of the ice beneath and cools. …

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Scientists get dirty at the Robson Glacier

July 24, 2013 — Glacier retreat areas provide an excellent window into the evolution of microbial communities, an ideal opportunity for scientists to study how quickly soil biological functions become established and how ecosystems begin to form. Soils are not static in the landscape, but instead evolve with time under the influence of multiple environmental factors — understanding how these factors interact can lead to advancements in the science and management of soils.Aria Hahn and Dr. Sylvie Quideau, researchers at the University of Alberta, conducted their research in Mount Robson Provincial Park along the Robson Glacier in British Columbia. Standing 3954 m tall, Mount Robson is the highest point in the Canadian Rocky Mountains and supports a large ice- and snowfield. Their study was published today in the Canadian Journal of Soil Science.”We are excited to present some of the first data documenting microbial community diversity, biomass and function along a 100-year-old soil chronosequence in a Canadian glacier retreat area,” says Dr. Quideau. “These beautiful natural wonders provide an excellent opportunity to study the development of soils and the microbial communities that live within them.”Hahn and Quideau measured soil microbial community composition and functional diversity, and determined the influence of Engelmann spruce (Picea engelmannii Parry) and yellow mountain avens (Dryas drummondii Rich.) on soil microbial community succession along the glacier chronosequence. They found that while soil microbial composition remained relatively stable, total biomass and fungal activity of the community responded to changes in the soil environment and increased as the soil aged.Correlations between microbial respiration of carbon substrates with the soil nitrogen content indicated that the soil microbial community was influencing changes in the soil environment. Yellow mountain avens, a plant known to support nitrogen fixation, increased soil microbial biomass, although this effect took 40 years after deglaciation to emerge.”Soils and their inhabiting microbes differ greatly among glacier sites around the Earth. We believe that by understanding the natural phenomena in glaciers here at home, we can not only advance the management of Canadian ecosystems but also contribute valuable knowledge to the global community.”

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Sea level rise: New iceberg theory points to areas at risk of rapid disintegration

July 22, 2013 — In events that could exacerbate sea level rise over the coming decades, stretches of ice on the coasts of Antarctica and Greenland are at risk of rapidly cracking apart and falling into the ocean, according to new iceberg calving simulations from the University of Michigan.”If this starts to happen and we’re right, we might be closer to the higher end of sea level rise estimates for the next 100 years,” said Jeremy Bassis, assistant professor of atmospheric, oceanic and space sciences at the U-M College of Engineering, and first author of a paper on the new model published in the current issue of Nature Geoscience.Iceberg calving, or the formation of icebergs, occurs when ice chunks break off larger shelves or glaciers and float away, eventually melting in warmer waters. Although iceberg calving accounts for roughly half of the mass lost from ice sheets, it isn’t reflected in any models of how climate change affects the ice sheets and could lead to additional sea level rise, Bassis said.”Fifty percent of the total mass loss from the ice sheets, we just don’t understand. We essentially haven’t been able to predict that, so events such as rapid disintegration aren’t included in those estimates,” Bassis said. “Our new model helps us understand the different parameters, and that gives us hope that we can better predict how things will change in the future.”The researchers have found the physics at the heart of iceberg calving, and their model is the first that can simulate the different processes that occur on both ends of Earth. It can show why in northern latitudes — where glaciers rest on solid ground — icebergs tend to form in relatively small, vertical slivers that rotate onto their sides as they dislodge. It can also illustrate why in the southernmost places — where vast ice shelves float in the Antarctic Ocean — icebergs form in larger, more horizontal plank shapes.The model treats ice sheets — both floating shelves and grounded glaciers — like loosely cemented collections of boulders. Such a description reflects how scientists in the field have described what iceberg calving actually looks like. The model allows those loose bonds to break when the boulders are pulled apart or rub against one another.The simulations showed that calving is a two-step process driven primarily by the thickness of the ice.”Essentially, everything is driven by gravity,” Bassis said. “We identified a critical threshold of one kilometer where it seems like everything should break up. You can think of it in terms of a kid building a tower. …

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Huge iceberg breaks away from the Pine Island glacier in the Antarctic

July 10, 2013 — On July 8, 2013, a huge area of the ice shelf broke away from the Pine Island glacier, the longest and fastest flowing glacier in the Antarctic, and is now floating in the Amundsen Sea in the form of a very large iceberg. Scientists of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research have been following this natural spectacle via Earth observation satellites TerraSAR-X from the German Space Agency (DLR) and have documented it in many individual images. The data is intended to help solve the physical puzzle of this “calving.”Scientists from the American space agency NASA discovered the first crack in the glacier tongue on 14 October 2011 when flying over the area. At that time it was some 24 kilometres long and 50 metres wide. “As a result of these cracks, one giant iceberg broke away from the glacier tongue. It measures 720 square kilometres and is therefore almost as large as the city of Hamburg,” reports Prof. Angelika Humbert, ice researcher at the Alfred Wegener Institute.The glaciologist and her team used the high resolution radar images of the DLR earth observation satellite TerraSAR-X to observe the progress of the two cracks and to better understand the physical processes behind the glacier movements. The researchers were thus able to measure the widths of the gaps and calculate the flow speed of the ice. “Above the large crack, the glacier last flowed at a speed of twelve metres per day,” reports Humbert’s colleague Dr. Dana Floricioiu from DLR. …

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In bitter cold subglacial lake, surprising life goes on

July 5, 2013 — Lake Vostok, buried under a glacier in Antarctica, is so dark, deep and cold that scientists had considered it a possible model for other planets, a place where nothing could live.However, work by Dr. Scott Rogers, a Bowling Green State University professor of biological sciences, and his colleagues has revealed a surprising variety of life forms living and reproducing in this most extreme of environments. A paper published June 26 in PLOS ONE (Public Library of Science) details the thousands of species they identified through DNA and RNA sequencing.”The bounds on what is habitable and what is not are changing,” Rogers said.This is the fourth article the group has published about its Lake Vostok investigations. The team included Dr. Paul Morris, biology, who with Scott and doctoral student Yury Shtarkman conducted most of the genetic analyses; former doctoral students Zeynep Koçer, now with the Department of Infectious Diseases, Division of Virology, at St. Jude’s Research Hospital in Memphis, performed most of the laboratory work; Ram Veerapaneni, now at BGSU Firelands, Tom D’Elia, now at Indian River State College in Florida, and undergraduate student Robyn Edgar, computer science.Their work was supported by several grants, including two from the National Science Foundation, one from U.S. Department of Agriculture and one from the BGSU Faculty Research Committee. Together, the amount dedicated to the project was more than $250,000.When thinking about Lake Vostok, you have to think big. The fourth-deepest lake on Earth, it is also the largest of the 400-some subglacial lakes known in Antarctica. The ice that has covered it for the past 15 million years is now more than two miles deep, creating tremendous pressure in the lake. …

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Ancient plants reawaken: Plants exposed by retreating glaciers regrowing after centuries entombed under ice

May 28, 2013 — When University of Alberta researcher Catherine La Farge threads her way through the recently exposed terrain left behind by retreating glaciers, she looks at the ancient plant remains a lot closer than most. Now, her careful scrutiny has revealed a startling reawakening of long-dormant plants known as bryophytes.

La Farge, a researcher in the Faculty of Science, and director and curator of the Cryptogamic Herbarium at the University of Alberta, has overturned a long-held assumption that all of the plant remains exposed by retreating polar glaciers are dead. Previously, any new growth of plants close to the glacier margin was considered the result of rapid colonization by modern plants surrounding the glacier.

Using radiocarbon dating, La Farge and her co-authors confirmed that the plants, which ranged from 400 to 600 years old, were entombed during the Little Ice Age that happened between 1550 and 1850. In the field, La Farge noticed that the subglacial populations were not only intact, but also in pristine condition — with some suggesting regrowth.

In the lab, La Farge and her master’s student Krista Williams selected 24 subglacial samples for culture experiments. Seven of these samples produced 11 cultures that successfully regenerated four species from the original parent material.

La Farge says the regrowth of these Little Ice Age bryophytes (such as mosses and liverworts) expands our understanding of glacier ecosystems as biological reservoirs that are becoming increasingly important with global ice retreat. “We know that bryophytes can remain dormant for many years (for example, in deserts) and then are reactivated, but nobody expected them to rejuvenate after nearly 400 years beneath a glacier.

“These simple, efficient plants, which have been around for more than 400 million years, have evolved a unique biology for optimal resilience,” she adds. “Any bryophyte cell can reprogram itself to initiate the development of an entire new plant. This is equivalent to stem cells in faunal systems.”

La Farge says the finding amplifies the critical role of bryophytes in polar environments and has implications for all permafrost regions of the globe.

“Bryophytes are extremophiles that can thrive where other plants don’t, hence they play a vital role in the establishment, colonization and maintenance of polar ecosystems. This discovery emphasizes the importance of research that helps us understand the natural world, given how little we still know about polar ecosystems — with applied spinoffs for understanding reclamation that we may never have anticipated.”

The research was published in the Proceedings of the National Academy of Sciences.

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