2008 ozone hole larger than last year





Ozone hole during 7 October 2008 as measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) atmospheric sensor onboard ESA’s Envisat. - Credits: KNMI/ESA
Ozone hole during 7 October 2008 as measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) atmospheric sensor onboard ESA’s Envisat. – Credits: KNMI/ESA

The 2008 ozone hole – a thinning in the ozone layer over Antarctica – is larger both in size and ozone loss than 2007 but is not as large as 2006.



Ozone is a protective atmospheric layer found in about 25 kilometres altitude that acts as a sunlight filter shielding life on Earth from harmful ultraviolet rays, which can increase the risk of skin cancer and cataracts and harm marine life.



This year the area of the thinned ozone layer over the South Pole reached about 27 million square kilometres, compared to 25 million square kilometres in 2007 and a record ozone hole extension of 29 million square kilometres in 2006, which is about the size of the North American continent.



The depletion of ozone is caused by extreme cold temperatures at high altitude and the presence of ozone-destructing gases in the atmosphere such as chlorine and bromine, originating from man-made products like chlorofluorocarbons (CFCs), which were phased out under the 1987 Montreal Protocol but continue to linger in the atmosphere.



Depending on the weather conditions, the size the Antarctic ozone hole varies every year. During the southern hemisphere winter, the atmosphere above the Antarctic continent is kept cut off from exchanges with mid-latitude air by prevailing winds known as the polar vortex – the area in which the main chemical ozone destruction occurs. The polar vortex is characterized by very low temperatures leading to the presence of so-called stratospheric clouds (PSCs).



As the polar spring arrives in September or October, the combination of returning sunlight and the presence of PSCs leads to a release of highly ozone-reactive chlorine radicals that break ozone down into individual oxygen molecules. A single molecule of chlorine has the potential to break down thousands of molecules of ozone.



Julian Meyer-Arnek of the German Aerospace Centre (DLR), which monitors the hole annually, explained the impact of regional meteorological conditions on the time and range of the ozone hole by comparing 2007 with 2008.



“In 2007 a less concentric and larger polar vortex led to an early onset of the ozone destruction in the sunlit parts of the polar vortex,” Meyer-Arnek said. “Therefore, we saw an ozone hole formation in the beginning of September 2007 which corresponded to the average behaviour of the years 1995-2006.”



“In 2008 a more concentric polar vortex led to a delay of the onset of the ozone destruction of about one week. The preconditioning of the polar chemistry was about the same for both years, although in 2008 the temperatures were slightly below the 2007 temperatures leading to slightly improved formation of PSCs,” he continued.



“Since the polar vortex remained undisturbed for a long period, the 2008 ozone hole became one of the largest ever observed.”


Minimum values of the ozone layer of about 120 Dobson Units are observed this year compared to around 100 Dobson Units in 2006. A Dobson Unit is a unit of measurement that describes the thickness of the ozone layer in a column directly above the location of measurement.



DLR’s analysis is based upon the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) atmospheric sensor onboard ESA’s Envisat, the Global Ozone Monitoring Experiment (GOME) aboard ESA’s ERS-2 and its follow-on instrument GOME-2 aboard EUMETSAT’s MetOp.



Scientists say that since the size and precise time of the ozone hole is dependent on the year-to-year variability in temperature and atmospheric dynamics, the detection of signs of ozone recovery is difficult.



“In order to detect these signs of recovery, a continuous monitoring of the global ozone layer and in particular of the Antarctic ozone hole is crucial,” Meyer-Arnek said.



In order to train the next generation of atmospheric scientists to continue the monitoring, students at ESA’s Advanced Atmospheric Training Course, held 15-20 September at University of Oxford, UK, were given the task of analysing this year’s ozone hole with Envisat sensors.



Studying the Envisat data, the students’ findings were in line with atmospheric scientists that the south polar vortex was more concentric in 2008 than in 2007, leading to a relatively late onset of ozone depletion, and that the size of this year’s hole is similar to previous years.



“This exercise led us to realise that although many questions have been answered and much has been learned about the stratospheric chemistry and atmospheric dynamics driving ozone hole behaviour, many new questions must be raised especially concerning ozone hole recovery,” said Deborah C Stein Zweers, a post-doc satellite researcher from the Royal Netherlands Meteorological Institute (KNMI) who attended the course.



“We want to know when the ozone hole will recover, how its recovery will be complicated by an environment with increasing greenhouse gases and how atmospheric dynamics will shape future ozone holes. These and many other questions will attract the attention of our generation of scientists for the next several decades.”

Volcanic eruption signals simulated in lab for first time


For the first time, seismic signals that precede a volcanic eruption have been simulated and visualized in 3-D under controlled pressure conditions in a laboratory. The ability to conduct such simulations will better equip municipal authorities in volcanic hot spots around the world in knowing when to alert people who live near volcanoes of an impending eruption.



The international research team that conducted the experiments at the University of Toronto published its findings in an article in the prestigious journal, Science, on Oct. 10.



Using equipment funded by the Canada Foundation for Innovation, scientists tested fracture properties of basalt rock from Mount Etna, the active volcano found on the island of Sicily in southern Italy. They were able to record the seismic signals that are routinely generated during earthquakes that occur before volcanic eruptions. The seismic (sound) waves recorded by the team were similar to those emitted by a church organ pipe and are ubiquitous in active volcanic regions.



“The holy grail of volcano research is to be able to predict with complete accuracy when and how exactly a volcano will erupt,” said Philip Benson, Marie-Curie Research Fellow in Earth Sciences at University College London (UCL), who conducted the experiments in U of T’s Rock Fracture Dynamics Facility. “We are not there yet and, frankly, we may never be able to achieve that level of detail. However, being able to simulate the pressure conditions and events in volcanoes greatly assists geophysicists in exploring the scientific basis for volcanic unrest, ultimately helping cities and towns near volcanoes know whether to evacuate or not.”


Benson noted that nearly 500 million people live near enough to the Earth’s 600 active volcanoes to endure physical and economic harm should a serious eruption occur. “That is why improved understanding of volcanic mechanisms is a central goal in volcano-tectonic research and hazard mitigation.”



The international collaborators in the simulation experiments were Sergio Vinciguerra of the National Geophysics and Volcano Institute (INGV) in Rome, Italy; Philip Meredith of the Rock and Ice Physics Laboratory at UCL; and Paul Young, Keck Chair of Seismology and Rock Mechanics at the University of Toronto and the university’s vice-president (research).



Young noted that while this particular rock fracture research focused on volcano dynamics, the knowledge generated from investigation into rock fracturing also has direct application in a wide variety of areas, such as mining, construction of buildings and bridges, oil and gas exploration and in earthquakes and other earth sciences phenomena.



He added that U of T has been “extremely fortunate” to have Benson as a visiting Lassonde Institute Research Fellow. “Philip could have gone anywhere in the world with this prestigious Marie-Curie Fellowship and he chose the University of Toronto. The investment by the Canada Foundation for Innovation enabled the design and construction of a state-of-the-art experimental fracture facility that has led to globally competitive research innovation and a strengthening of our ability to attract the best talent to Canada. This is also a perfect example of how government support of research has huge societal benefits.”

Future Risk of Hurricanes: The Role of Climate Change


Scientists focus on hurricane-prone Gulf of Mexico and Caribbean Sea to assess likely changes



Researchers are homing in on the hurricane-prone Gulf of Mexico and Caribbean Sea to assess the likely changes, between now and the middle of the century, in the frequency, intensity, and tracks of these powerful storms. Initial results are expected early next year.



The National Center for Atmospheric Research (NCAR) in Boulder, Colo., working with federal agencies as well as the insurance and energy industries, has launched an intensive study to examine how global warming will influence hurricanes in the next few decades.



The goal of the project is to provide information to coastal communities, offshore drilling operations, and other interests that could be affected by changes in hurricanes.



“This science builds on years of previous investment,” said Cliff Jacobs, program director in the National Science Foundation (NSF)’s Division of Atmospheric Sciences, which is funding the project. “The outcome of this research will shed light on the relationship between global warming and hurricanes, and will better inform decisions by government and industry.”



The project relies on an innovative combination of global climate and regional weather models, run on one of the world’s most powerful supercomputers.



“It’s clear from the impacts of recent hurricane activity that we urgently need to learn more about how hurricane intensity and behavior may respond to a warming climate,” says NCAR scientist Greg Holland, who is leading the project. “The increasingly dense development along our coastlines and our dependence on oil from the Gulf of Mexico leaves our society dangerously vulnerable to hurricanes.”



The new study follows two major reports, by the U.S. Climate Change Science Program (CCSP) and Intergovernmental Panel on Climate Change (IPCC), that found evidence for a link between global warming and increased hurricane activity.



But many questions remain about future hurricane activity. For example, the CCSP report concluded that future changes in frequency were uncertain, and that rainfall and intensity were likely to increase, but with unknown consequences.



Improved understanding of climate change and hurricanes is an especially high priority for the energy industry, which has a concentration of drilling platforms, refineries, pipelines and other infrastructure in the region that are vulnerable to severe weather.



Hurricanes Gustav and Ike damaged offshore oil production and several refineries, disrupting gasoline supplies.


The project is part of a larger effort examining regional climate change between 1995 and 2055.



The simulations are being run on NCAR’s bluefire supercomputer with support from NSF, NCAR’s sponsor, and through a long-term collaboration with the insurance industry through the Willis Research Network.



“This research program by NCAR is a major contribution to the insurance industry and public policy makers,” says Rowan Douglas, managing director of Willis.



“The primary way to improve our understanding of present and future hurricane risk is to generate computer simulations of storms in unprecedented detail.”



For the project, the model will examine three decades in detail: 1995-2005, 2020-2030, and 2045-2055. Scientists will use statistical techniques to fill in the gaps between these decades.



A major goal is to examine how several decades of greenhouse-gas buildup could affect regional climate and, in turn, influence hurricanes and other critical weather features. Scientists will also investigate the impact of the powerful storms on global climate.



One of the most difficult technical challenges for such a project is to create a model that can capture both the climate of the entire world and the behavior of a single hurricane.



To get around this roadblock, NCAR has developed an approach called Nested Regional Climate Modeling (NRCM). The center “nests” a special version of its high-resolution weather model (the Weather Research and Forecasting model, or WRF) inside its lower-resolution, global climate model (the Community Climate System Model, or CCSM).



The resulting simulations show fine-scale detail for certain regions, like the Gulf of Mexico, while also incorporating global climate patterns.



For each of its decade-long time slices, the NRCM’s resolution will be about 20 miles across Africa, Europe, and the South Atlantic, 7.5 miles across the tropical Atlantic and northeastern United States, and an even sharper 2.5 miles over the Caribbean and Gulf of Mexico, southeastern United States, and drought-prone western United States.



“Combining weather and climate models in this way enables more detailed projections of hurricanes in a warming world than any study to date,” says Holland. “These projections will help reduce the uncertainty of current assessments, and they also serve the very important role of providing experience about applying future predictions of changes to high impact weather systems in general.”

Preserved by ice: Glacial dams helped prevent erosion of Tibetan plateau





A shortened moraine dam on the Tsangpo River stands amid the Himalaya mountains at Namche Barwa in Tibet, at the head of the Tsangpo gorge. - Credit: Bernard Hallet/University of Washington
A shortened moraine dam on the Tsangpo River stands amid the Himalaya mountains at Namche Barwa in Tibet, at the head of the Tsangpo gorge. – Credit: Bernard Hallet/University of Washington

The Tsangpo River is the highest major river in the world, starting at 14,500 feet elevation and plunging to the Bay of Bengal, scouring huge amounts of rock and soil along the way. Yet in its upper reaches, the powerful Tsangpo seems to have had little effect on the elevation of the Tibetan Plateau.



New research suggests that the plateau edge might have been preserved for thousands of years by ice during glacial advances and by glacial debris deposited at the mouth of many Tsangpo tributaries during warmer times when glaciers retreated. Those debris walls, or moraines, acted as dams that prevented the rapidly traveling water in the main Tsangpo gorge from carving upstream into the plateau.



“At the edge of the plateau, the river’s erosion has been defeated because the dams have flattened the river’s slope and reduced its ability to cut into the surrounding terrain, making it more like a lake,” said David Montgomery, a University of Washington geomorphologist.



Montgomery is co-author of a paper in the Oct. 9 issue of Nature that describes a new hypothesis of why the Tibetan Plateau has maintained its elevation when it appears it should have been worn down in the area of the Tsangpo system.



The paper’s lead author is Oliver Korup of the Swiss Federal Institute for Snow and Avalanche Research in Davos, Switzerland. The work was financed in part by the European Commission and the National Science Foundation in the U.S.



The researchers focused on the three primary rivers of the Tsangpo system, the Yarlung Tsangpo and its two major tributaries, the Yigong Tsangpo and the Parlung Tsangpo. The scientists mapped geologic evidence of more than 300 natural dams, including 260 moraines, that have formed repeatedly at the mouths of tributaries in the last 10,000 years to block water flow on the three main streams.


The first evidence of the dams was found at the edge of the Tibetan Plateau, and additional evidence continued to be found upstream, Montgomery said. The dams essentially formed giant lakes along the river and prevented the water from carving into bedrock.



“The glaciers seem to have helped preserve the edge of the plateau by keeping the river from ripping into it,” he said. “This isn’t the explanation for why the rest of the plateau is so well preserved, but it might work for this area where the Tsangpo crosses the edge of the plateau.”



There are two well-recognized mechanisms that typically are thought to be responsible for preserving a feature such as the edge of the Tibetan Plateau. But one of them, the plateau’s arid climate, is not to blame because the Tsangpo is already a large river at the point that it enters the world’s deepest and fastest-eroding gorge. The other conventional explanation, that tectonic faults continually push new rock to the surface and thus offset any erosion by the river, might be at work in concert with the glacial damming, the scientists believe.



In the Tsangpo gorge, also called Yarlung Tsangpo Grand Canyon, the river plunges from about 10,000 feet to about 1,000 feet in a span of 150 miles. Eventually the river becomes the Brahmaputra River, flowing through India and Bangladesh and into the Bay of Bengal.



“Up in the gorge, the river is very steep and the erosion is very high, and one would think that back through geologic time it should have sliced upstream into the Tibetan Plateau,” Montgomery said.



The question is why that didn’t happen. Korup and Montgomery suspect that the glacial dams on tributaries right to the edge of the plateau prevented such pronounced erosion.



“It’s a transition from where the river is doing all the erosion at lower elevations to where the glaciers are doing all the erosion at high elevations, and the glaciers are limited on how deeply they erode,” Montgomery said. “They shave off the top but they don’t erode farther down, and the rivers can’t erode back past the glaciers.”

Extinction by asteroid a rarity


Evidence suggests that ‘sick Earth’ extinctions more likely



In geology as in cancer research, the silver bullet theory always gets the headlines and nearly always turns out to be wrong.



For geologists who study mass extinctions, the silver bullet is a giant asteroid plunging to earth.



But an asteroid is the prime suspect only in the most recent of five mass extinctions, said USC earth scientist David Bottjer. The cataclysm 65 million years ago wiped out the dinosaurs.



“The other four have not been resolvable to a rock falling out of the sky,” Bottjer said.



For example, Bottjer and many others have published studies suggesting that the end-Permian extinction 250 million years ago happened in essence because “the earth got sick.”



The latest research from Bottjer’s group suggests a similar slow dying during the extinction 200 million years ago at the boundary of the Triassic and Jurassic eras.



At the 2008 Joint Annual Meeting of the Geological Society of America, USC doctoral student Sarah Greene drew similarities between ocean conditions at the Triassic-Jurassic boundary and after the end-Permian extinction.


At both those times, bouquet-like structures of aragonite crystals formed on the ocean floor. Such structures are extremely rare in Earth’s history, Greene said.



“The fact that these deposits have only been found at these two specific times that are associated with mass extinction suggests at the very least that maybe there’s some shared ocean geochemistry … that could be related to the cause of the extinctions,” Greene said.



“The Triassic-Jurassic extinction cause is totally up for grabs at the moment,” she added.



Also at the meeting, USC doctoral student Rowan Martindale presented results from her studies of coral reefs during the Triassic-Jurassic extinction.



“The coral reefs look actually very similar to modern coral reefs,” she said. “At the end-Triassic mass extinction, you lose all your reef systems. And nobody’s figured out why that is.”



Martindale identified two distinct types of ancient reefs: one dominated by coral and another consisting mainly of mud and debris, possibly held together by bacteria.



A theory for the end-Triassic extinction needs to explain how both types of reefs could have been killed off, Martindale said.



Any knowledge about end-Triassic reef death could be useful in understanding the current reef crisis, widely attributed to climate change.



“We’re looking at it as a model to give us any insight that we might have for today’s decline for coral reefs,” Bottjer said.

Most Alaskan Glaciers Retreating, Thinning, and Stagnating





This August 1941 photograph is of Muir Glacier in Glacier Bay National Monument, Alaska. It shows the lower reaches of Muir Glacier, then a large, tidewater calving valley glacier and its tributary, Riggs Glacier. For nearly two centuries before 1941, Muir Glacier had been retreating. In places, a thickness of more than two-thirds of a mile of ice had been lost. Photo courtesy of the National Snow and Ice Data Center and Glacier Bay National Park and Preserve Archive
This August 1941 photograph is of Muir Glacier in Glacier Bay National Monument, Alaska. It shows the lower reaches of Muir Glacier, then a large, tidewater calving valley glacier and its tributary, Riggs Glacier. For nearly two centuries before 1941, Muir Glacier had been retreating. In places, a thickness of more than two-thirds of a mile of ice had been lost. Photo courtesy of the National Snow and Ice Data Center and Glacier Bay National Park and Preserve Archive

Most glaciers in every mountain range and island group in Alaska are experiencing significant retreat, thinning or stagnation, especially glaciers at lower elevations, according to a new book published by the U.S. Geological Survey. In places, these changes began as early as the middle of the 18th century.



Although more than 99 percent of Alaska’s large glaciers are retreating, a handful, surprisingly, are advancing.



The Glaciers of Alaska, authored by USGS research geologist Bruce Molnia, represents a comprehensive overview of the state of the glaciers of Alaska at the end of the 20th century and beginning of the 21st century. Richard Williams Jr., an emeritus senior research glaciologist with the USGS, said the 550-page volume will serve as a major reference work for glaciologists studying glaciers in Alaska in the years and decades to come.



The report uses a combination of satellite images, vertical aerial photographs (black-and-white and color-infrared photos taken from airplanes, looking straight down), oblique aerial photographs (color photos taken from the air at an angle, such as most regular photos), and maps, supported by the scientific literature, to document the distribution and behavior of glaciers throughout Alaska.


The author concludes that, because of the vast areas encompassed by the glacierized regions of Alaska, satellite remote sensing provides the only feasible means of monitoring changes in glacier area and in position of termini — the end of a glacier — in response to short- and long-term changes in the marine and continental climates of Alaska.



Alaskan glaciers are found in 11 mountain ranges, one large island, one island chain, and one archipelago. Details about the recent behavior of many of Alaska’s glaciers are contained in this richly illustrated book, with multiple photographs and satellite images, as well as hundreds of aerial photographs by Molnia, taken during his more than four decades of work in Alaska.



Three other USGS glaciologists authored two sidebar sections of the book: Columbia and Hubbard Tidewater Glaciers, by Robert M. Krimmel; and The 1986 and 2002 Temporary Closures of Russell Fiord by the Hubbard Glacier, by Bruce F. Molnia, Dennis C. Trabant, Rod S. March, and Robert M. Krimmel. A third section, Geospatial Inventory and Analysis of Glaciers: a Case Study for the Eastern Alaska Range, was authored by William F. Manley, Institute of Arctic and Alpine Research (INSTAAR), University of Colorado.



This professional paper (USGS Professional Paper 1386-K) is available in print and online at http://pubs.usgs.gov/pp/p1386k/. It is the 8th volume to be published in the Satellite Image Atlas of Glaciers of the World series; the other seven volumes are available in print and online at http://pubs.usgs.gov/fs/2005/3056/ More than 100 glaciologists from the United States and other nations have collaborated with the USGS to produce these 11 volumes.

Tech Student Helping with Advanced Exploration on Vast Ore Deposit





Melissa Lindholm
Melissa Lindholm

A New Mexico Tech graduate student is contributing significant geological research into development of the second largest gold and copper deposit in the world.



Melissa Lindholm (right), a master’s student in geology, recently worked on her second summer research season at the Pebble Deposit in remote southwest Alaska. She presented her research into the geology of the untapped deposit at a recent mining conference in Grants.



Landing this summer internship was like striking gold for Lindholm. She has worked on the Western Hemisphere’s second largest untapped deposit of copper and gold for two summers, enjoying the temperate climate and getting hands-on experience in geology and mining.



The Pebble Deposit was first discovered in 1988. Extensive drilling in 2005 confirmed a resource of 42.1 million ounces of gold, 24.7 billion pounds of copper, 1.35 billion pounds of molybdenum and additional silver. In 2007, a second deposit was found – Pebble East – that contains an additional 49 billion pounds of copper, 45 million ounces of gold and 2.8 billion pounds of molybdenum.



“They are in advanced exploration phase, but it’s not totally defined. It’s still open in some directions,” she said.



In her abstract, Lindholm wrote that Pebble is near two small native villages and straddles two important watersheds. Development in the area presents environmental challenges for clean mining.



“Nevertheless, Pebble’s spectacular size and potential make any investigation of this system interesting to exploration geologists as well as ore genesis researchers,” she wrote.



Lindholm landed the job through Dr. William Chavez, professor of mineral engineering at Tech. A colleague of Chavez at Pebble asked him if he knew of a graduate student who could work on advanced exploration on site. Lindholm jumped at the chance to work and learn on such a vast project in an exotic locale.



During the summer, Lindholm did what she called typical junior geologist duties – visually estimating mineral grade and describing textures, inspecting drill rigs and describing drill core samples. The two seasons in Alaska involved mostly work, but Lindholm had her share of fun.



“We get to fly in helicopters and see grizzly bears,” she said. “The area is so beautiful.”



The site of the deposit is about 40 miles inland from Cook Inlet on the southwest tip of Alaska. The site is accessible only by helicopter.



During the summer months, about 100 staff members work at the headquarters and at the site, with as many as 100 outside contractors filtering in and out of the area.



The company funded her research, so Lindholm was allowed to bring core samples back to Socorro for testing.


Her tests involve two main objectives: studying the sulfur isotopes in the samples and petrography, which means giving a detailed chemical and geological description of the rocks.



For her petrography study, she sliced thin sections of rock, which allowed her to examine and analyze the mineral composition. That study has no direct mining application, but could potentially be useful as a metallurgical analysis and provide a geological framework for the deposit, she said.



Lindholm anticipates publishing one of the first – if not the first ever – research papers about the Pebble East deposit.



“It’s fascinating for us to be involved, because we’re getting involved on the ground floor,” said her co-advisor Dr. Andrew Campbell. “Hopefully, Melissa’s work will be some of the good, early work. As this prospect develops into a mine, they’ll be referring back to her work for years to come.”



Lindholm said recent research in Australia and the Canadian west have identified sulfur isotope patterns that appear to correlate with copper and gold grades. She is comparing cores from Pebble East to the other sulfur isotope research papers.



“Most copper and gold is found in alkalic rock, meaning the have more sodium and potassium, as opposed to other deposits that have more sulfur and are acidic,” she said.



Lindholm is studying the sulfur isotopes from various core samples from the Pebble East deposit in an attempt to make a connection between sulfur isotopes and recoverable minerals – mainly copper and gold. For the sulfur isotope study, Lindholm used Dr. Campbell’s mass spectrometer to determine the isotopic composition of the sulfide minerals.



“No one has ever done this sort of study at Pebble,” she said. “I am testing to see if I get the same pattern that was found in Australia and British Columbia.”



A native of Fergus Falls, Minn., Lindholm completed her bachelor’s in geology at Bryn Mawr College in Pennsylvania. After finishing her master’s in geology later this year at New Mexico Tech, she hopes to return to Alaska to start her career working on the Pebble deposits as a full-time geologist.



“It’s pretty unusual to work on a deposit starting with exploration and continue through feasibility and into mining,” she said. “That would be amazing.”

Arctic sea ice annual freeze-up underway





Arctic sea ice extent as seen by Envisat’s Advanced Synthetic Aperture Radar (ASAR) sensor during mid-September 2007 and mid-September 2008. The Arctic sea areas covered by ice in September 2008, but ice-free in September 2007, are visible in blue. The Arctic sea areas covered by ice in September 2007, but ice free in September 2008, are visible in dark brown. The Arctic sea covered by ice both in September 2007 and September 2008 are visible in light brown. - Credits: ESA
Arctic sea ice extent as seen by Envisat’s Advanced Synthetic Aperture Radar (ASAR) sensor during mid-September 2007 and mid-September 2008. The Arctic sea areas covered by ice in September 2008, but ice-free in September 2007, are visible in blue. The Arctic sea areas covered by ice in September 2007, but ice free in September 2008, are visible in dark brown. The Arctic sea covered by ice both in September 2007 and September 2008 are visible in light brown. – Credits: ESA

After reaching the second-lowest extent ever recorded last month, sea ice in the Arctic has begun to refreeze in the face of autumn temperatures, closing both the Northern Sea Route and the direct route through the Northwest Passage.



This year marked the first time since satellite measurements began in the 1970s that the Northern Sea Route, also known as the Northeast Passage, and the Northwest Passage were both open at the same time for a few weeks.



“NIC analysis of ESA’s Envisat and other satellite datasets indicated that the Northern Sea Route opened when a path through the Vilkitski Strait finally cleared by 5 September,” NIC Chief Scientist Dr Pablo Clemente-Colón said via email from aboard the US Coast Guard icebreaker Healy in the Arctic, where he is conducting joint mapping operations with the Canadian Coast Guard.



“This is the first time in our charting records that both historic passages opened up in the same year,” Clemente-Colón said. “Both of the routes appeared as closed by 22 September.”



The Northwest Passage’s most direct route, a long-sought shortcut from Europe to Asia through the Canadian Arctic that has been historically impassable, opened up for the second consecutive time this year.



“As early as 18 August 2008 the Northwest Passage began appearing navigable in the US National Ice Center (NIC) analysis of Envisat Advanced Synthetic Aperture Radar (ASAR) data although we were cautious in announcing it as a significant amount of ice was still prevalent,” Clemente-Colón said.



The indirect, more southerly route – called the Amundsen Northwest Passage – opened up in July 2008, and according to ASAR images is about to close in the coming days.



The Northern Sea Route extends from the Norwegian Sea, along the Arctic coast of Asia and through the Bering Sea to the Pacific Ocean, while the Northwest Passage runs along the north coast of the North American continent.


Each year, the Arctic Ocean experiences the formation and then melting of vast amounts of ice that floats on the sea surface, but the rate of overall loss has accelerated.



During the last 30 years, satellites that have been observing the Arctic have witnessed reductions in the minimum ice extent at the end of summer from around 8 million km² in the early 1980s to the historic minimum of less than 4.24 million km² in 2007, as observed by Envisat.



The fact that this year’s minimum extent, which was well below the long-term average, did not break last year’s record does not signify a recovery.



“Although last year’s summer sea ice minimum extent record was not broken, a record amount of the thickest multiyear sea ice was actually lost this season impacting the thickness of the sea ice presently found around the North Pole region and setting the stage for more minimum or near-minimum records in upcoming years,” Clemente-Colón said.



The Arctic is one of the most inaccessible regions on Earth and is prone to long periods of bad weather and extended darkness, so obtaining measurements of sea ice was difficult before the advent of satellites.



Radar instruments aboard Earth observation satellites, such as Envisat’s ASAR sensor, are particularly suited for monitoring Polar Regions because they are able to acquire images through clouds and darkness.



ESA has been providing satellite data on the cryosphere for more than 20 years. The agency is currently contributing to the International Polar Year 2007-2008, one of the most ambitious coordinated science programmes ever undertaken in the Arctic and Antarctic.



Further exploitation of data collected over the Arctic since 1991 is part of an ESA Initiative on Climate Change that will be proposed to the ESA Member States at its Ministerial Conference in November 2008. The proposal aims to ensure delivery of appropriate information on climate variables derived from satellites.



In 2009, ESA will make another significant contribution research into the cryosphere with the launch of CryoSat-2. The observations made over the three-year lifetime of the mission will provide conclusive evidence on the rates at which ice thickness and cover is diminishing.

Bays on US Gulf Coast vulnerable to flooding


3 decades of data point to troubling century ahead for Gulf bays



The most comprehensive geological review ever undertaken of the upper U.S. Gulf Coast suggests that a combination of rising seas and dammed rivers could flood large swaths of wetlands this century in one or more bays from Alabama to Texas.



“In terms of sea-level increases and river sediments flowing into the bays, we’re rapidly approaching a time when bays will face conditions they last saw in the Holocene, from about 9,600 until 7,000 years ago,” said lead researcher John Anderson, the W. Maurice Ewing Professor in Oceanography and professor of Earth science at Rice University. “That period was marked by dramatic and rapid flooding events in each of these bays — events that saw some bays increase their size by as much as one-third over a period of 100 or 200 years.”



Anderson is presenting the findings at next week’s annual meeting of the Geological Society of America (GSA) at Houston’s George R. Brown Convention Center. Anderson said the magnitude of flooding seen in bays during the Holocene — the geological epoch that began 10,000 years ago — would be noticeable and apparent, even on a year-to-year timescale.



“If you lived at the head of Galveston Bay, near Anahuac (Texas), you could see the bayhead move northward by as much as the length of a football field each year,” Anderson said.



Anderson and colleagues, including Antonio Rodriguez of the University of North Carolina at Chappell Hill, compiled their research in a new 146-page monograph published by the GSA, “Response of Upper Gulf Coast Estuaries to Holocene Climate Change and Sea-Level Rise.”


Their findings stemmed from an analysis of 30 years of data from hundreds of bayfloor sediment samples, radiocarbon tests and seismic surveys from Galveston, Matagorda and Corpus Christi bays in Texas, Mobile Bay in Alabama, Calcasieu Bay in Louisiana and Sabine Lake on the Texas-Louisiana border.



“There is no question that sea levels are rising in this region at a rate today that approaches what we saw in the Holocene,” Anderson said.



He said the Holocene was also marked by alternating wet and dry periods upstream, particularly in central and western Texas. There was significantly less sediment flowing into the bays during the dry periods, and the researchers found that the most dramatic flooding events occurred when less sediment was flowing into the bays at the same time that sea levels were rising faster than four millimeters per year.



Anderson said that’s a particularly troubling finding because several recent studies have confirmed that the rate of sea-level rise along the Gulf Coast has doubled in the past century to a current rate of about three millimeters per year. At the same time, the installation of dams upstream has slashed the amount of sediment flowing into every southern U.S. bay.



“Our research paints a pretty clear picture of what happened in these bays the last time they encountered the circumstances that we expect to see during the coming century,” Anderson said. “Our hope is that policymakers will take note of the potential danger and take steps to help alleviate it.”



For example, Anderson said it doesn’t make environmental sense to keep a navigation channel open between the lower Trinity River and upper Galveston Bay because the channel diverts the sediment that is flowing into the bay, preventing it from replenishing the upper bay wetlands near Anahuac.



“Now that we’re aware of the dangers, there are clearly things we can do to try and avoid them,” he said.

Gas From the Past Gives Scientists New Insights into Climate and the Oceans





The bubbles visable in this piece from an Antarctic ice core sample contain carbon dioxide and other gases that were trapped in the ice when formed thousands of years ago. Researchers carefully crush the piece and capture the gases that escape when the bubbles break. This allows them to better understand what carbon dioxide levels were over time. - Credit: Courtesy of Oregon State University
The bubbles visable in this piece from an Antarctic ice core sample contain carbon dioxide and other gases that were trapped in the ice when formed thousands of years ago. Researchers carefully crush the piece and capture the gases that escape when the bubbles break. This allows them to better understand what carbon dioxide levels were over time. – Credit: Courtesy of Oregon State University

Ice core and ocean deposit comparisons show complex links between carbon dioxide levels, ocean currents and climate; may help explain past, present and future climate trends



In recent years, public discussion of climate change has included concerns that increased levels of carbon dioxide will contribute to global warming, which in turn may change the circulation in the earth’s oceans, with potentially disastrous consequences.



In a paper published today in the journal Science, researchers presented new data from their analysis of ice core samples and ocean deposits dating as far back as 90,000 years ago and suggest that warming, carbon dioxide levels and ocean currents are tightly inter-related. These findings provide scientists with more data and insights into how these phenomena were connected in the past and may lead to a better understanding of future climate trends.


With support from the National Science Foundation, Jinho Ahn and Edward Brook, both geoscientists at Oregon State University, analyzed 390 ice core samples taken from Antarctic ice at Byrd Station. The samples offered a snap shot of the Earth’s atmosphere and climate dating back between 20,000 and 90,000 years. Sections of the samples were carefully crushed, releasing gases from bubbles that were frozen within the ice through the millennia. These ancient gas samples were then analyzed to measure the levels of carbon dioxide contained in each one.



Ahn and Brook then compared the carbon dioxide levels from the ice samples with climate data from Greenland and Antarctica that reflected the approximate temperatures when the gases were trapped and with ocean sediments in Chile and the Iberian Peninsula. Data from the sediments provided the scientists with an understanding of how fast or slow the ocean currents were in the North Atlantic and how well the Southern Ocean was stratified during these same time periods.



The researchers discovered that elevations in carbon dioxide levels were related to subsequent increases in the Earth’s temperature as well as reduced circulation of ocean currents in the North Atlantic. The data also suggests that carbon dioxide levels increased along with the weakening of mixing of waters in the Southern Ocean. This, the researchers say, may point to potential future scenario where global warming causes changes in ocean currents which in turn causes more carbon dioxide to enter the atmosphere, adding more greenhouse gas to an already warming climate.



Ahn and Brook state that a variety of factors may be at work in the future that alter the relationship between climate change and ocean currents. One potential factor is that the levels of carbon dioxide in today’s atmosphere are much higher than they were during the period Ahn and Brook studied. The researchers hope that future studies of the ancient gas from a newly drilled ice core may allow a higher resolution analysis and yield more details about the timing between CO2 levels and the temperature at the earth’s poles.