Ocean temperatures and sea level increases 50 percent higher than earlier predictions

Rising ocean and atmospheric temperatures affect glaciers such as Alaska's Hubbard Glacier. - Photo Credit: Bob Hirschfeld
Rising ocean and atmospheric temperatures affect glaciers such as Alaska’s Hubbard Glacier. – Photo Credit: Bob Hirschfeld

New research suggests that ocean temperature and associated sea level increases between 1961 and 2003 were 50 percent larger than estimated in the 2007 Intergovernmental Panel on Climate Change report.

The results are reported in the June 19 edition of the journal Nature. An international team of researchers, including Lawrence Livermore National Laboratory climate scientist Peter Gleckler, compared climate models with improved observations that show sea levels rose by 1.5 millimeters per year in the period from 1961-2003. That equates to an approximately 2½-inch increase in ocean levels in a 42-year span.

The ocean warming and thermal expansion rates are more than 50 percent larger than previous estimates for the upper 300 meters of oceans.

The research corrected for small but systematic biases recently discovered in the global ocean observing system, and uses statistical techniques that “infill” information in data-sparse regions. The results increase scientists’ confidence in ocean observations and further demonstrate that climate models simulate ocean temperature variability more realistically than previously thought.

“This is important for the climate modeling community because it demonstrates that the climate models used for assessing sea-level rise and ocean warming tie in closely with the observed results,” Gleckler said.

Estimates of ocean heat content and sea surface temperature.
Estimates of ocean heat content and sea surface temperature.

Climate model data were analyzed from 13 different modeling groups. All model data were obtained from the WCRP CMIP3 multi-model dataset archived at the LLNL’s Program for Climate Model Diagnosis and Intercomparison (PCMDI).

Although observations and models confirm that recent warming is greatest in the upper ocean, there are widespread observations of warming deeper than 700 meters.

Results were compared with recent estimates of other contributions to sea-level rise including glaciers, ice caps, Greenland and Antarctic ice sheets, and thermal expansion changes in the deep ocean. When these independent lines of evidence are examined collectively, the story is more consistent than found in earlier studies.

The oceans store more than 90 percent of the heat in the Earth’s climate system and act as a temporary buffer against the effects of climate change. The ocean warming and thermal expansion rates are 50 percent larger than previous estimates for the upper 700 meters of oceans, and greater than that for the upper 300 meters.

“This is just the tip of the iceberg, so to speak,” Gleckler said. “Our ability to quantify structural uncertainties in observationally based estimates is critically important. This study represents important progress.”

The team involved researchers from the Centre for Australian Weather and Climate Research (CSIRO), the Antarctic Climate and Ecosystems Cooperative Research Centre and LLNL.

Pyrite deposits across the state may be tied to an Eocene meteor

The Chesapeake Bay - Landsat photo
The Chesapeake Bay – Landsat photo

In 2003, during construction of Interstate 99 in Centre County, Pennsylvania, state road builders hit the mother lode. That’s a bad thing.

At a place called Skytop Mountain, 10 miles west of State College, PennDOT engineers encountered a huge deposit of iron pyrite laced through the sandstone ridge. Exposed to air and water, this highly reactive material became an environmental nightmare, leaching sulfuric acid into a nearby stream and groundwater. Subsequent efforts to contain the damage have so far cost more than $79 million.

What caused this massive — and unexpected — sulfide deposit? Barry Scheetz and his colleague Ryan Mathur pin the blame on a meteor that crashed 35 million years ago smack into Chesapeake Bay.

Scheetz, a professor of materials, civil and nuclear engineering at Penn State and an expert on acid mine drainage, was contracted by PennDOT shortly after the Skytop remediation began, and asked to help predict where such deposits might exist elsewhere around the state.

The first step was analyzing the material at hand. Isotopic tests conducted by Ryan Mathur, a geochemist at nearby Juniata College, showed that the Skytop pyrite was 35 million years old, and was molten (about 400 degrees C) at the time of placement. “It came from the mantle,” Scheetz concluded. So how did it get to the surface?

“You need a competent host,” Scheetz said, meaning a substrate of rock hard enough that “when it fractures and opens up, it stays open.” The sandstone at Skytop fits the bill. The fractures there, called lineaments, formed 250 million years ago when the Appalachian mountains pushed up, and extend all the way to bedrock.

“That’s your plumbing system,” Scheetz said. “And the last thing you need is a driver. So the question becomes, what the hell happened 35 million years ago?”

The answer, he said, is a cataclysmic impact. During the late Eocene epoch, a massive object up to three miles in diameter and moving at 12 miles per second slammed into the coastal shallows of what is now the Tidewater region of Virginia. The evidence for this event, known as the Chesapeake Bay impact crater, runs some 52 miles across and nearly as deep as the Grand Canyon. Hidden under the sediments of the bay, the crater was not even suspected until 1983. Its full extent was not known until the mid-1990s.

“My guess is it probably changed the axis of the Earth,” Scheetz said of the collision. “Everything within a 600-mile radius was utterly destroyed.” The result below the surface was similarly dramatic.

“Have you ever seen pictures of people shooting at jugs of water?” Scheetz asks. “How the water just explodes because of the hydraulic impact? That’s exactly what happened here. This thing hit and this enormous hydraulic pulse surged into the mantle. The fluids that were present there shot up through these pre-existing fractures,” and wound up near the surface at Skytop.

“But it’s not just Skytop,” he said. Scheetz and colleagues have tested samples from nine other deposits, six in nearby Blair and Huntingdon counties, two in York County and one as far away as Montgomery County, in the southeastern part of the state. All have the same isotopic signature. “The fact that we have found 10 of these things tells me they could be anywhere in Pennsylvania,” he said.

He and a graduate student, Chad Ellsworth, have mapped some of the major lineaments in the ridge and valley region, using telltale landscape features like wind and water gaps and the presence of sandstone to locate additional deposits along these fractures. They have mapped 150 known deposits so far — many, Scheetz suspects, have the potential to result from the same wayward meteor. He is looking for funding that would allow him to incorporate aerial reconnaissance and electromagnetic sensing into the search.

“Being able to predict where these isolated deposits are likely to pop up,” he says, “could prevent future Skytops around the state and beyond.”

Ebb and flow of the sea drives world’s big extinction events

If you are curious about Earth’s periodic mass extinction events such as the sudden demise of the dinosaurs 65 million years ago, you might consider crashing asteroids and sky-darkening super volcanoes as culprits.

But a new study, published online today (June 15, 2008) in the journal Nature, suggests that it is the ocean, and in particular the epic ebbs and flows of sea level and sediment over the course of geologic time, that is the primary cause of the world’s periodic mass extinctions during the past 500[sc1] million years.

“The expansions and contractions of those environments have pretty profound effects on life on Earth,” says Shanan Peters, a University of Wisconsin-Madison assistant professor of geology and geophysics and the author of the new Nature report.

In short, according to Peters, changes in ocean environments related to sea level exert a driving influence on rates of extinction, which animals and plants survive or vanish, and generally determine the composition of life in the oceans.

Since the advent of life on Earth 3.5 billion years ago, scientists think there may have been as many as 23 mass extinction events, many involving simple forms of life such as single-celled microorganisms. During the past 540 million years, there have been five well-documented mass extinctions, primarily of marine plants and animals, with as many as 75-95 percent of species lost.

For the most part, scientists have been unable to pin down the causes of such dramatic events. In the case of the demise of the dinosaurs, scientists have a smoking gun, an impact crater that suggests dinosaurs were wiped out as the result of a large asteroid crashing into the planet. But the causes of other mass extinction events have been murky, at best.

“Paleontologists have been chipping away at the causes of mass extinctions for almost 60 years [sc2], ” explains Peters, whose work was supported by the National Science Foundation. “Impacts, for the most part, aren’t associated with most extinctions. There have also been studies of volcanism, and some eruptions correspond to extinction, but many do not.”

Arnold I. Miller, a paleobiologist and professor of geology at the University of Cincinnati, says the new study is striking because it establishes a clear relationship between the tempo of mass extinction events and changes in sea level and sediment: “Over the years, researchers have become fairly dismissive of the idea that marine mass extinctions like the great extinction of the Late Permian might be linked to sea-level declines, even though these declines are known to have occurred many times throughout the history of life. The clear relationship this study documents will motivate many to rethink their previous views.”

Peters measured two principal types of marine shelf environments preserved in the rock record, one where sediments are derived from erosion of land and the other composed primarily of calcium carbonate, which is produced in-place by shelled organisms and by chemical processes. “The physical differences between (these two types) of marine environments have important biological consequences,” Peters explains, noting differences in sediment stability, temperature, and the availability of nutrients and sunlight.

In the course of hundreds of millions of years, the world’s oceans have expanded and contracted in response to the shifting of the Earth’s tectonic plates and to changes in climate. There were periods of the planet’s history when vast areas of the continents were flooded by shallow seas, such as the shark- and mosasaur-infested seaway that neatly split North America during the age of the dinosaurs.

As those epicontinental seas drained, animals such as mosasaurs and giant sharks went extinct, and conditions on the marine shelves where life exhibited its greatest diversity in the form of things like clams and snails changed as well.

The new Wisconsin study, Peters says, does not preclude other influences on extinction such as physical events like volcanic eruptions or killer asteroids, or biological influences such as disease and competition among species. But what it does do, he argues, is provide a common link to mass extinction events over a significant stretch of Earth history.

“The major mass extinctions tend to be treated in isolation (by scientists),” Peters says. “This work links them and smaller events in terms of a forcing mechanism, and it also tells us something about who survives and who doesn’t across these boundaries. These results argue for a substantial fraction of change in extinction rates being controlled by just one environmental parameter.”

  1. The study starts in the Ordovician
  2. 100 years would refer to larger-scale changes in faunal composition

Even the Antarctic winter cannot protect Wilkins Ice Shelf

<IMG SRC="/Images/Wilkins_Ice_Shelf.jpg" WIDTH="350" HEIGHT="339" BORDER="0" ALT="Wilkins Ice Shelf has experienced further break-up with an area of about 160 km2 breaking off. “>
Wilkins Ice Shelf has experienced further break-up with an area of about 160 km2 breaking off.

Wilkins Ice Shelf has experienced further break-up with an area of about 160 km² breaking off from 30 May to 31 May 2008. ESA’s Envisat satellite captured the event – the first ever-documented episode to occur in winter.

Wilkins Ice Shelf, a broad plate of floating ice south of South America on the Antarctic Peninsula, is connected to two islands, Charcot and Latady. In February 2008, an area of about 400 km² broke off from the ice shelf, narrowing the connection down to a 6 km strip; this latest event in May has further reduced the strip to just 2.7 km.

This animation, comprised of images acquired by Envisat’s Advanced Synthetic Aperture Radar (ASAR) between 30 May and 9 June, highlights the rapidly dwindling strip of ice that is protecting thousands of kilometres of the ice shelf from further break-up.

According to Dr Matthias Braun from the Center for Remote Sensing of Land Surfaces, Bonn University, and Dr Angelika Humbert from the Institute of Geophysics, Münster University, who have been investigating the dynamics of Wilkins Ice Shelf for months, this break-up has not yet finished.

“The remaining plate has an arched fracture at its narrowest position, making it very likely that the connection will break completely in the coming days,” Braun and Humbert said.

<IMG SRC="http://www.esa.int/images/asa_imm_geo_sub_L,0.gif" BORDER="0" ALT="Wilkins Ice Shelf has experienced further break-up with an area of about 160 km2 breaking off. “>

Braun and Humbert are monitoring the ice sheet daily via Envisat acquisitions as part of their contribution to the International Polar Year (IPY) 2007-2008, a large worldwide science programme focused on the Arctic and Antarctic.

The ASAR images used to compile these animations were acquired as part of ESA’s support to IPY. ESA is helping scientists during IPY to collect an increasing amount of satellite information, particularly to understand recent and current distributions and variations in snow and ice and changes in the global ice sheets.

ESA is also co-leading a large IPY project – the Global Interagency IPY Polar Snapshot Year (GIIPSY) – with the Byrd Polar Research Centre. The goal of GIIPSY is to make the most efficient use of Earth-observing satellites to capture essential snapshots that will serve as benchmarks for gauging past and future changes in the environment of the polar regions.

ASAR is extremely useful for tracking changes in ice sheets because it is able to see through clouds and darkness – conditions often found in polar regions.

Long-term satellite monitoring over Antarctica is important because it provides authoritative evidence of trends and allows scientists to make predictions. Ice shelves on the Antarctic Peninsula are important indicators for on-going climate change because they are sandwiched by extraordinarily raising surface air temperatures and a warming ocean.

The Antarctic Peninsula has experienced extraordinary warming in the past 50 years of 2.5°C, Braun and Humbert explained. In the past 20 years, seven ice shelves along the peninsula have retreated or disintegrated, including the most spectacular break-up of the Larsen B Ice Shelf in 2002, which Envisat captured within days of its launch.

New mineral named for astronomer

The International Mineralogical Association has named a new mineral, the first to be discovered in a particle from a comet, in honor of Donald Brownlee, a University of Washington astronomer who revolutionized research on interplanetary dust entering Earth’s atmosphere.

The manganese silicide mineral, a combination of manganese and silicon, is now officially called brownleeite and joins a list of more than 4,300 accepted minerals. It was found inside a particle collected from a dust stream entering the atmosphere in 2003.

Brownlee, whose UW office is adorned with a variety of mineral specimens, was clearly pleased with the honor — and somewhat amused.

“I’ve always been very intrigued by minerals, so it’s great to be one,” he said. “I never dreamed I’d have a mineral named after me. I guess maybe being a vitamin is next.”

The particle was captured by a high-altitude NASA aircraft, and NASA researchers in Houston, along with collaborators elsewhere in the United States, Germany and Japan, identified the compound. (See http://www.nasa.gov/home/hqnews/2008/jun/HQ_08143_comet_dust.html .) Brownleeite, a semiconductor material, can be synthesized but has not been found naturally on Earth.

The team that found the manganese silicide was led by NASA scientist Keiko Nakamura-Messenger from the Johnson Space Center in Houston, who provided documentation for the international mineralogical body to declare the specimen to be a new mineral. The team also asked that it be named for Brownlee.

“This really did surprise me because I know it took a lot of effort to get this mineral approved,” Brownlee said.

Nakamura-Messenger’s team believes the dust particle originated in a comet, possibly comet 26P/Grigg-Skjellerup, which was predicted to be the source of an Earth-crossing dust stream in April 2003, when the particle was captured.

The Earth is covered with more than 30,000 tons of particles from space every year, one particle per square meter of planet surface every day. But the particles are so small that it would take 10 billion to fully cover that square meter of surface, so they are extremely hard to find.

“That’s a lot of dirt and it takes 300 million years to build up a layer as thick as the diameter of a human hair,” Brownlee said.

He began his efforts to capture particles of provable extraterrestrial origin while he was a UW doctoral student in the late 1960s. Others had made similar efforts previously, but they proved to be unsuccessful. Using a succession of high-altitude balloons, Brownlee captured a few particles that could be proven to have come from somewhere other than Earth.

His third balloon carried an 800-pound machine he calls “the vacuum monster,” which dangled below the balloon as it drifted at an altitude of 125,000 feet, or about 24 miles. The machine made it possible to sample a very large volume of air, and eventually he was able to capture a total of about a dozen interplanetary dust particles from seven flights.

He later devised a small collector that could be attached to the fuselage of high-flying U2 reconnaissance aircraft and, because the planes remain airborne for so long and fly at high speeds, they are able to collect hundreds of particles.

“Almost all of the flights are done for something else, and these detectors are along for the ride. When they are opened, they just flop out into the atmosphere and gather particles as the plane moves along,” Brownlee said.

Brownlee also is a leading authority on comets. He is the principal investigator of NASA’s Stardust mission, which traveled to comet 81P/Wild-2 beyond the orbit of Mars, captured particles streaming from the comet’s surface, and returned them to Earth in January 2006. The samples are curated by the Johnson Space Center.

Ancient mineral shows early Earth climate tough on continents

Pictured is a false-color microscope image of a 4-billion-year-old zircon, a tiny mineral used to study the ancient rocks in which it formed. Chemical analysis of this crystal by UW-Madison geologists Takayuki Ushikubo and John Valley suggests that rocky continents and liquid water existed on Earth at least 4.3 billion years ago. Evidence of heavy weathering by a harsh climate may help explain why no rock samples older than 4 billion years have ever been found. - Photo: courtesy Mary Diman and John Valley
Pictured is a false-color microscope image of a 4-billion-year-old zircon, a tiny mineral used to study the ancient rocks in which it formed. Chemical analysis of this crystal by UW-Madison geologists Takayuki Ushikubo and John Valley suggests that rocky continents and liquid water existed on Earth at least 4.3 billion years ago. Evidence of heavy weathering by a harsh climate may help explain why no rock samples older than 4 billion years have ever been found. – Photo: courtesy Mary Diman and John Valley

A new analysis of ancient minerals called zircons suggests that a harsh climate may have scoured and possibly even destroyed the surface of the Earth’s earliest continents.

Zircons, the oldest known materials on Earth, offer a window in time back as far as 4.4 billion years ago, when the planet was a mere 150 million years old. Because these crystals are exceptionally resistant to chemical changes, they have become the gold standard for determining the age of ancient rocks, says UW-Madison geologist John Valley.

Valley previously used these tiny mineral grains – smaller than a speck of sand – to show that rocky continents and liquid water formed on the Earth much earlier than previously thought, about 4.2 billion years ago.

In a new paper published online this week in the journal Earth and Planetary Science Letters, a team of scientists led by UW-Madison geologists Takayuki Ushikubo, Valley and Noriko Kita show that rocky continents and liquid water existed at least 4.3 billion years ago and were subjected to heavy weathering by an acrid climate.

Ushikubo, the first author on the new study, says that atmospheric weathering could provide an answer to a long-standing question in geology: why no rock samples have ever been found dating back to the first 500 million years after the Earth formed.

“Currently, no rocks remain from before about 4 billion years ago,” he says. “Some people consider this as evidence for very high temperature conditions on the ancient Earth.”

Previous explanations for the missing rocks have included destruction by barrages of meteorites and the possibility that the early Earth was a red-hot sea of magma in which rocks could not form.

The current analysis suggests a different scenario. Ushikubo and colleagues used a sophisticated new instrument called an ion microprobe to analyze isotope ratios of the element lithium in zircons from the Jack Hills in western Australia. By comparing these chemical fingerprints to lithium compositions in zircons from continental crust and primitive rocks similar to the Earth’s mantle, they found evidence that the young planet already had the beginnings of continents, relatively cool temperatures and liquid water by the time the Australian zircons formed.

A timeline shows the geological context of Jack Hills zircons, ancient minerals that formed when the Earth was less than 500 million years old. - Illustration: Andree Valley
A timeline shows the geological context of Jack Hills zircons, ancient minerals that formed when the Earth was less than 500 million years old. – Illustration: Andree Valley

“At 4.3 billion years ago, the Earth already had habitable conditions,” Ushikubo says.

The zircons’ lithium signatures also hold signs of rock exposure on the Earth’s surface and breakdown by weather and water, identified by low levels of a heavy lithium isotope. “Weathering can occur at the surface on continental crust or at the bottom of the ocean, but the [observed] lithium compositions can only be formed from continental crust,” says Ushikubo.

The findings suggest that extensive weathering may have destroyed the Earth’s earliest rocks, he says.

“Extensive weathering earlier than 4 billion years ago actually makes a lot of sense,” says Valley. “People have suspected this, but there’s never been any direct evidence.”

Carbon dioxide in the atmosphere can combine with water to form carbonic acid, which falls as acid rain. The early Earth’s atmosphere is believed to have contained extremely high levels of carbon dioxide – maybe 10,000 times as much as today.

“At [those levels], you would have had vicious acid rain and intense greenhouse [effects]. That is a condition that will dissolve rocks,” Valley says. “If granites were on the surface of the Earth, they would have been destroyed almost immediately – geologically speaking – and the only remnants that we could recognize as ancient would be these zircons.”

Additional information and images are available on the authors’ Web sites Zircons Are Forever and the Wisc-SIMS ion microprobe facility.

Other co-authors on the paper include Aaron Cavosie of the University of Puerto Rico, Simon Wilde of the Curtin University of Technology in Australia and Roberta Rudnick of the University of Maryland.

Rocky water source

Water from rock, easier than blood from stone

Gypsum, a rocky mineral is abundant in desert regions where fresh water is usually in very short supply but oil and gas fields are common. Writing in International Journal of Global Environmental Issues, Peter van der Gaag of the Holland Innovation Team, in Rotterdam, The Netherlands, has hit on the idea of using the untapped energy from oil and gas flare-off to release the water locked in gypsum.

Fresh water resources are scarce and will be more so with the effects of global climate change. Finding alternative sources of water is an increasingly pressing issue for policy makers the world over. Gypsum, explains van der Gaag could be one such resource. He has discussed the technology with people in the Sahara who agree that the idea could help combat water shortages, improve irrigation, and even make some deserts fertile.

Chemically speaking, gypsum is calcium sulfate dihydrate, and has the chemical formula CaSO4.2H2O. In other words, for every unit of calcium sulfate in the mineral there are two water molecules, which means gypsum is 20% water by weight.

van der Gaag suggests that a large-scale, or macro, engineering project could be used to tap off this water from the vast deposits of gypsum found in desert regions, amounting to billions of cubic meters and representing trillions of liters of clean, drinking water.

The process would require energy, but this could be supplied using the energy from oil and gas fields that is usually wasted through flaring. Indeed, van der Gaag explains that it takes only moderate heating, compared with many chemical reactions, to temperatures of around 100 Celsius to liberate water from gypsum and turn the mineral residue into bassanite, the anhydrous form. “Such temperatures can be reached by small-scale solar power, or alternatively, the heat from flaring oil wells can be used,” he says. He adds that, “Dehydration under certain circumstances starts at 60 Celsius, goes faster at 85 Celsius, and faster still at 100 degrees. So in deserts – where there is abundant sunlight – it is very easy to do.”

van der Gaag points out that the dehydration of gypsum results in a material of much lower volume than the original mineral, so the very process of releasing water from the rock will cause local subsidence, which will then create a readymade reservoir for the water. Tests of the process itself have proved successful and the Holland Innovation Team is planning a pilot study in a desert location.

“The macro-engineering concept of dewatering gypsum deposits could solve the water shortage problem in many dry areas in the future, for drinking purposes as well as for drip irrigation,” concludes van der Gaag.

“Mining water from gypsum” in International Journal of Global Environmental Issues, 2008, 8, 274- 281

Greenland Ice Sheet runoff may more than double by century’s end

The Greenland Ice Sheet is melting faster than previously calculated according to a recently released scientific paper by University of Alaska Fairbanks researcher Sebastian H. Mernild.

The study, published in the journal Hydrological Processes, is based on models using data from the Intergovernmental Panel on Climate Change, as well as satellite images and observations from on the ground in Greenland.

Mernild and his team found that the total amount of fresh water projected to flow from the Greenland Ice Sheet into the North Atlantic Ocean from 2071 to 2100 will be more than double current levels.

Today, the East Greenland Ice Sheet adds 257 cubic kilometers of fresh water to the ocean per year from both melting and iceberg calving. By 2100, those levels are estimated to reach 456 cubic kilometers per year. With land-based runoff factored in, the total fresh water flowing from Greenland into the ocean is estimated to increase from 438 cubic kilometers to 650 cubic kilometers by 2100. The projected increase means that rather than rising at a rate of 1.1 millimeters per year, sea levels would rise by 1.6 millimeters per year.

“The Greenland Ice Sheet mass balance is changing as a response to the altered climatic state,” said Mernild. “This is faster than expected. This affects freshwater runoff input to the North Atlantic Ocean and plays an important role in determining the global sea level rise and global ocean … circulation.”

Mernild is conducting the research as part of the University of Alaska’s International Polar Year efforts. He was appointed a University of Alaska IPY postdoctoral fellow by UA president Mark Hamilton in 2007.

Fossils found in Tibet by geologist revise history of elevation, climate

Kunlun Mountain Pass Basin, Tibetan Plateau - Credit: Courtesy of Associate Professor Yang Wang, Florida State University Department of Geological Sciences
Kunlun Mountain Pass Basin, Tibetan Plateau – Credit: Courtesy of Associate Professor Yang Wang, Florida State University Department of Geological Sciences

About 15,000 feet up on Tibet’s desolate Himalayan-Tibetan Plateau, an international research team led by Florida State University geologist Yang Wang was surprised to find thick layers of ancient lake sediment filled with plant, fish and animal fossils typical of far lower elevations and warmer, wetter climates.

Back at the FSU-based National High Magnetic Field Laboratory, analysis of carbon and oxygen isotopes in the fossils revealed the animals’ diet (abundant plants) and the reason for their demise during the late Pliocene era in the region (a drastic climate change). Paleo-magnetic study determined the sample’s age (a very young 2 or 3 million years old).

That fossil evidence from the rock desert and cold, treeless steppes that now comprise Earth’s highest land mass suggests a literally groundbreaking possibility:

Major tectonic changes on the Tibetan Plateau may have caused it to attain its towering present-day elevations — rendering it inhospitable to the plants and animals that once thrived there — as recently as 2-3 million years ago, not millions of years earlier than that, as geologists have generally believed. The new evidence calls into question the validity of methods commonly used by scientists to reconstruct the past elevations of the region.

“Establishing an accurate history of tectonic and associated elevation changes in the region is important because uplift of the Tibetan Plateau has been suggested as a major driving mechanism of global climate change over the past 50-60 million years,” said Yang, an associate professor in FSU’s Department of Geological Sciences and a researcher at the National High Magnetic Field Laboratory. “What’s more, the region also is thought to be important in driving the modern Asian monsoons, which control the environmental conditions over much of Asia, the most densely populated region on Earth.”

The fossil findings and implications are described in the June 15, 2008 issue of the peer-reviewed journal Earth and Planetary Science Letters.

Yang co-authored the paper (“Stable isotopes in fossil mammals, fish and shells from Kunlun Pass Basin, Tibetan Plateau: Paleoclimatic and paleoelevation implications”) with paleontologists from the Department of Vertebrate Paleontology at the Natural History Museum of Los Angeles County, and the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Beijing). The collaborative research project, which since 2004 has featured summer field study on the remote Tibetan Plateau, is funded by a grant from the Sedimentary Geology and Paleobiology Program of the U.S. National Science Foundation.

“The uplift chronology of the Tibetan Plateau and its climatic and biotic consequences have been a matter of much debate and speculation because most of Tibet’s spectacular mountains, gorges and glaciers remain barely touched by man and geologically unexplored,” Yang said.

“So far, my research colleagues and I have only worked in two basins in Tibet, representing a very small fraction of the Plateau, but it is very exciting that our work to-date has yielded surprising results that are inconsistent with the popular view of Tibetan uplift,” she said.

This summer, Yang and her colleagues from Los Angeles and Beijing will conduct further fieldwork in areas near the Tibetan Plateau. “The next phase of our work will focus on examining the spatial and temporal patterns of long-term vegetative and environmental changes in and around the region,” she said. “Such records are crucial for clarifying the linkages among climatic, biotic and tectonic changes.”

There is much still to learn and understand about those changes.

“Many of the places we’ve visited in Tibet are now deserts, and yet we found those thick deposits of lake sediments with abundant fossil fish and shells,” Yang said. “This begs the question: What came first and caused the disappearance of those lakes? Global climate change? Or, tectonic change?”

Permafrost Threatened by Rapid Retreat of Arctic Sea Ice

Accelerated Arctic warming. Simulations by global climate models show that when sea ice is in rapid decline, the rate of predicted Arctic warming over land can more than triple. The image at left shows simulated autumn temperature trends during periods of rapid sea-ice loss, which can last for 5 to 10 years. The accelerated warming signal (ranging from red to dark red) reaches nearly 1,000 miles inland. In contrast, the image at right shows the comparatively milder but still substantial warming rates associated with rising amounts of greenhouse gas in the atmosphere and moderate sea-ice retreat that is expected during the 21st century. Most other parts of the globe (in white) still experience warming, but at a lower rate of less than 1 degree Fahrenheit (0.5 Celsius) per decade. - Image by Steve Deyo
Accelerated Arctic warming. Simulations by global climate models show that when sea ice is in rapid decline, the rate of predicted Arctic warming over land can more than triple. The image at left shows simulated autumn temperature trends during periods of rapid sea-ice loss, which can last for 5 to 10 years. The accelerated warming signal (ranging from red to dark red) reaches nearly 1,000 miles inland. In contrast, the image at right shows the comparatively milder but still substantial warming rates associated with rising amounts of greenhouse gas in the atmosphere and moderate sea-ice retreat that is expected during the 21st century. Most other parts of the globe (in white) still experience warming, but at a lower rate of less than 1 degree Fahrenheit (0.5 Celsius) per decade. – Image by Steve Deyo

The rate of climate warming over northern Alaska, Canada, and Russia could more than triple during periods of rapid sea ice loss, according to a new study led by the National Center for Atmospheric Research (NCAR). The findings raise concerns about the thawing of permafrost, or permanently frozen soil, and the potential consequences for sensitive ecosystems, human infrastructure, and the release of additional greenhouse gases.

“Our study suggests that, if sea-ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate,” says lead author David Lawrence of NCAR.

The study, by scientists from NCAR and the National Snow and Ice Data Center, will be published Friday in Geophysical Research Letters. It was funded by the U.S. Department of Energy and by the National Science Foundation, NCAR’s sponsor.

The research was spurred in part by events last summer, when the extent of Arctic sea ice shrank to more than 30 percent below average, setting a modern-day record. From August to October last year, air temperatures over land in the western Arctic were also unusually warm, reaching more than 4 degrees Fahrenheit (2 degrees Celsius) above the 1978-2006 average and raising the question of whether or not the unusually low sea-ice extent and warm land temperatures were related.

To investigate this question, Lawrence and his colleagues analyzed climate change simulations generated by the NCAR-based Community Climate System Model. Previous analysis of these simulations suggested that a sustained period of rapid ice loss lasting roughly 5 to 10 years can occur when the ice thins enough. During such an event, the model revealed, the minimum sea-ice extent can drop by an area greater than the size of Alaska and Colorado combined.

The team found that during episodes of rapid sea-ice loss, the rate of Arctic land warming is 3.5 times greater than the average 21st century warming rates predicted in global climate models. While this warming is largest over the ocean, the simulations suggest that it can penetrate as far as 900 miles inland. The simulations also indicate that the warming acceleration during such events is especially pronounced in autumn. The decade during which a rapid sea-ice loss event occurs could see autumn temperatures warm by as much as 9 degrees F (5 degrees C) along the Arctic coasts of Russia, Alaska, and Canada.

Lawrence and his colleagues then used the model to study the influence of accelerated warming on permafrost and found that in areas where permafrost is already at risk, such as central Alaska, a period of abrupt sea-ice loss could lead to rapid soil thaw. This situation, when summer thaw extends more deeply than the next winter’s freeze, can lead to a talik, which is a layer of permanently unfrozen soil sandwiched between the seasonally frozen layer above and the perennially frozen layer below. A talik allows heat to build more quickly in the soil, hastening the long-term thaw of permafrost.

Potential impacts on greenhouse gases

Arctic soils are believed to hold 30 percent or more of all the carbon stored in soils worldwide. Although researchers are uncertain what will happen to this carbon as soils warm and permafrost thaws, one possibility is that the thaw will initiate significant additional emissions of carbon dioxide or the more potent greenhouse gas, methane.

About a quarter of the Northern Hemisphere’s land contains permafrost, defined as soil that remains below 32 degrees F (0 degrees C) for at least two years. Recent warming has degraded large sections of permafrost, with pockets of soil collapsing as the ice within it melts. The results include buckled highways, destabilized houses, and “drunken forests” of trees that lean at wild angles.

“An important unresolved question is how the delicate balance of life in the Arctic will respond to such a rapid warming,” Lawrence says. “Will we see, for example, accelerated coastal erosion, or increased methane emissions, or faster shrub encroachment into tundra regions if sea ice continues to retreat rapidly?”

The study sheds light on how interconnected the Arctic system is, says co-author Andrew Slater, a scientist at the National Snow and Ice Data Center (NSIDC). “The loss of sea ice can trigger widespread changes that would be felt across the region.”

About the article

Title: “Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss”
Authors: David Lawrence, Andrew Slater, Robert Tomas, Marika Holland, and Clara Deser
Publication: Geophysical Research Letters, June 13, 2008