Ancient Hawaiian glaciers reveal clues to global climate impacts

Gray rubble on the flanks of Mauna Kea on the island of Hawaii lie in contrast to the red volcanic rock behind them, and were deposited by a glacier that disappeared thousands of years ago. (Photo courtesy of Oregon State University)
Gray rubble on the flanks of Mauna Kea on the island of Hawaii lie in contrast to the red volcanic rock behind them, and were deposited by a glacier that disappeared thousands of years ago. (Photo courtesy of Oregon State University)

Boulders deposited by an ancient glacier that once covered the summit of Mauna Kea on the island of Hawaii have provided more evidence of the extraordinary power and reach of global change, particularly the slowdown of a North Atlantic Ocean current system that could happen again and continues to be a concern to climate scientists.

A new study has found geochemical clues near the summit of Mauna Kea that tell a story of ancient glacier formation, the influence of the most recent ice age, more frequent major storms in Hawaii, and the impact of a distant climatic event that changed much of the world.

The research was published in Earth and Planetary Science Letters by scientists from Oregon State University, the Woods Hole Oceanographic Institution, University of British Columbia and U.S. Geological Survey. The work was supported by the National Science Foundation.

“Mauna Kea had a large glacial ice cap of about 70 square kilometers until 14,500 years ago, which has now all disappeared,” said Peter Clark, a professor of geosciences at OSU. “We’ve been able to use new data to determine specifically when, where and most likely why the glacier existed and then disappeared.”

Mauna Kea, at 13,803 feet above sea level, is in a sense the tallest mountain in the world because it rises 30,000 feet from the sea floor. Dormant for thousands of years, it once featured a large glacier on its massive peak at the height of the last ice age about 21,000 years ago. As the ice age ended and the global climate warmed, the glacier began to disappear.

However, the new research found that the glacier on Mauna Kea began to re-advance to almost its ice age size about 15,400 years ago. That coincides almost exactly with a major slowdown of what scientists call the Atlantic meridional overturning circulation, or AMOC, in the North Atlantic Ocean.

The AMOC is part of a global ocean circulation system that carries heat from the tropics to the North Atlantic. This transported heat is the primary reason that much of Europe is warmer in the winter than would be expected, given the latitude of the continent.

Studies of past climate change indicate that the AMOC has slowed a number of times, in surprisingly short periods, causing substantial cooling of Europe. Because of that, the potential future decline of the current is of considerable interest.

But scientists have found that the AMOC does more than just keep northern Europe habitable. Its effects can extend far beyond that.

“The new data from Mauna Kea, along with other findings from geological archives preserved in oceans and lakes in many other areas, show that the decline of the AMOC basically caused climate changes all over the world,” Clark said. “These connections are pretty remarkable, a current pattern in the North Atlantic affecting glacier development thousands of miles away in the Hawaiian Islands.

“The global impact of the AMOC changes,” Clark added, “was just massive.”

The formation, size and movement of glaciers can provide valuable data, he said, because these characteristics reflect current and historic changes in temperature, precipitation or both.

The study concludes that the growth of the Mauna Kea glacier caused by the AMOC current changes was a result of both colder conditions and a huge increase of precipitation on Mauna Kea – triple that of the present – that scientists believe may have been caused by more frequent cyclonic storm events hitting the Hawaiian Islands from the north.

The findings were supported by measurements of an isotope of helium being produced in boulders left by the Mauna Kea glacier thousands of years ago. The amount of this helium isotope reveals when the boulders were finally uncovered by ice and exposed to the atmosphere.

The deposits containing the boulders are the only record of glaciation in the northern subtropical Pacific Ocean. Nearby Mauna Loa probably also was glaciated, but evidence of its glaciation has since been destroyed by volcanic eruptions.

The study by Clark and colleagues provides additional evidence that rapid changes in the AMOC can trigger widespread global change. Some past abrupt decreases in the AMOC have been linked to an increase of freshwater flowing off the continents into the North Atlantic.

The potential under global warming for increases in freshwater from melting ice and changes in precipitation patterns have heightened concerns about the AMOC and related climate effects in the future, researchers said.

Study finds permafrost warming, monitoring improving

University of Alaska Fairbanks Professor Vladimir Romanovsky measures permafrost temperature at a borehole in interior Alaska. -  Photo by A. Kholodov.
University of Alaska Fairbanks Professor Vladimir Romanovsky measures permafrost temperature at a borehole in interior Alaska. – Photo by A. Kholodov.

Permafrost warming continues throughout a wide swath of the Northern Hemisphere, according to a team of scientists assembled during the recent International Polar Year.

Their extensive findings, published in the April-June 2010 edition of Permafrost and Periglacial Processes, describe the thermal state of high-latitude permafrost during the International Polar Year, 2007-2009. Vladimir Romanovsky, a professor with the snow, ice and permafrost group at the University of Alaska Fairbanks Geophysical Institute, is the lead author of the paper, which also details the significant expansion of Northern Hemisphere permafrost monitoring.

“This paper is actually pretty unique,” Romanovsky said, “because it’s the first time such a large geographical area has been involved in one paper.”

During the International Polar Year, Romanovsky and his colleagues launched a field campaign to improve the existing permafrost-monitoring network. The permafrost thermal state is monitored with borehole sensors, which gather data from holes drilled deep into the permafrost. The researchers established nearly 300 borehole sites that serve as permafrost observatories across the polar and sub-polar regions in the Northern Hemisphere. Their work more than doubled the size of the previously existing network

“The heart of monitoring is the measuring of temperatures in boreholes,” Romanovsky said. “For permafrost temperatures, you have to be there. You have to establish boreholes.”

Having data from across the circumpolar North allows scientists to analyze trends affecting permafrost. The article notes that permafrost temperatures have warmed as much as two degrees Celsius from 20 to 30 years ago. They also found that permafrost near zero degrees Celsius warmed more slowly than colder permafrost. According to Romanovsky, this trend is an example of the large-scale analysis possible using data from the expanded network.

The enlarged and revamped observatory network is meant to be a building block for further research. It also has the potential to foster better modeling of future conditions and act as an early warning system of the negative consequences of climate change in permafrost regions. That could, in turn, help policymakers and the public plan for a future with warmer permafrost.

Romanovsky, whose specialty is Russian and North American permafrost conditions, plans to keep building on the legacy of the International Polar Year. With help from a five-year National Science Foundation grant, he continues his collaboration with American and international colleagues, establishing new borehole sites in undersampled areas and analyzing trends evidenced by the newly available data.

The Fourth International Polar Year was a two-year event that began in March of 2007 and focused the attention of the international research community on the Earth’s polar regions. UAF researchers were heavily involved in IPY projects and are still analyzing data from those projects.

Eruptive characteristics of Oregon’s Mount Hood analyzed

New research at Oregon State University has outlined the mechanisms that may lead to the next eruption of Mount Hood, the tallest mountain in Oregon. (Photo courtesy of Oregon State University)
New research at Oregon State University has outlined the mechanisms that may lead to the next eruption of Mount Hood, the tallest mountain in Oregon. (Photo courtesy of Oregon State University)

A new study has found that a mixing of two different types of magma is the key to the historic eruptions of Mount Hood, Oregon’s tallest mountain, and that eruptions often happen in a relatively short time – weeks or months – after this mixing occurs.

This behavior is somewhat different than that of most other Cascade Range volcanoes, researchers said, including Mount Hood’s nearby, more explosive neighbor, Mount St. Helens.

The research is being reported this week in Nature Geoscience by geologists from Oregon State University and the University of California at Davis, in work supported by the National Science Foundation.

It will help scientists better understand the nature of Mount Hood’s past and future eruptions, as well as other volcanoes that erupt by similar mechanisms. This includes a large number of the world’s active volcanoes.

“These data will help give us a better road map to what a future eruption on Mount Hood will look like, and what will take place before it occurs,” said Adam Kent, an OSU associate professor of geosciences. “It should also help us understand the nature of future eruptions and what risks they will entail.”

Mount Hood, at 11,249 feet tall, is the highest mountain in Oregon and fourth highest in the Cascade Range. The last major eruption was in the late 1780’s, and the effects of this eruption where viewed by members of the Lewis and Clark Expedition in 1805. It is considered potentially active and the Oregon volcano most likely to erupt, although the chances of that are still small.

Geologists are already able to use things like gas emissions, the chemistry of hot springs, ground deformation, local earthquakes and other data to help predict when a volcanic eruption is imminent, Kent said, and the new findings will add even more data toward that goal.

Two types of magma, or molten underground rock, are often involved in volcanic processes – mafic magma, which has less silica and is more fluid; and felsic magma, which has a higher silica content and a thicker consistency, like toothpaste. A third type of magma, called andesite, named after the Andes Mountains where it is often found, is composed of a mixture of both felsic and mafic magma.

Andesite is common in volcanoes that form at subduction zones – regions where one tectonic plate is sinking below another – and include those that form around the well-known Pacific Ocean “rim of fire”.

The rocks around Mount Hood, scientists say, are almost exclusively formed from andesitic magma. And research suggests that the recharge of mafic magma to mix with its thicker felsic counterpart often occurs just prior to an actual eruption.

“The intense mixing of these two types of magma causes an increase in pressure and other effects, and is usually the trigger for an eruption,” Kent said. “But this process doesn’t happen in all volcanic events. In the Cascade Range, Mount Hood appears to be one volcano where andesitic magma and recharge-driven eruptions are dominant.”

That may be because of local crustal conditions, Kent said. Even though the Cascade Range is linked to melting rock from the Cascadia Subduction Zone, some parts of the crust are more difficult than others for magma to move through. Mount Hood appears to be in a region where it takes the extra pressure of magma mixing to cause an eruption.

Kent said that researchers study these processes not only to improve their ability to predict eruptions, and to recognize precursors to eruption, but also to assess possible ore deposits associated with volcanic activity, and learn more about the fundamental dynamics of volcanic processes.

Ice core drilling effort to help assess abrupt climate change risks

An international drilling team involving CU-Boulder has hit bedrock 1.5 miles below the icy surface of Greenland, pulling up deep ice cores from the last interglacial period that should help climate scientists assess the risks of abrupt climate change on a warming Earth. -  Image courtesy NEEM ice core drilling project
An international drilling team involving CU-Boulder has hit bedrock 1.5 miles below the icy surface of Greenland, pulling up deep ice cores from the last interglacial period that should help climate scientists assess the risks of abrupt climate change on a warming Earth. – Image courtesy NEEM ice core drilling project

An international science team involving the University of Colorado at Boulder that is working on the North Greenland Eemian Ice Drilling project hit bedrock July 27 after two summers of work, drilling down more than 1.5 miles in an effort to help assess the risks of abrupt future climate change on Earth.

Led by Denmark and the United States, the team recovered ice from the Eemian interglacial period from about 115,000 to 130,000 years ago, a time when temperatures were 3.6 to 5.4 degrees Fahrenheit above today’s temperatures. During the Eemian — the most recent interglacial period on Earth — there was substantially less ice on Greenland, and sea levels were more than 15 feet higher than today.

While three previous ice cores drilled in Greenland in the last 20 years recovered ice from the Eemian, the deepest layers were compressed and folded, making the data difficult to interpret. The new effort, known as NEEM, has allowed researchers to obtain thicker, more intact annual ice layers near the bottom of the core that are expected to contain crucial information about how Earth’s climate functions, said CU-Boulder Professor Jim White, lead U.S. investigator on the project.

“Scientists from 14 countries have come together in a common effort to provide the science our leaders and policy makers need to plan for our collective future,” said White, who directs CU-Boulder’s Institute of Arctic and Alpine Research and is an internationally known ice core expert. “I hope that NEEM is a foretaste of the kind of cooperation we need for the future, because we all share the world.”

Annual ice layers formed over millennia in Greenland by compressed snow reveal information on past temperatures and precipitation levels, as well as the contents of ancient atmospheres, said White. Ice cores from previous drilling efforts revealed temperature spikes of more than 20 degrees Fahrenheit in just 50 years in the Northern Hemisphere.

White said the new NEEM ice cores will more accurately portray past changes in temperatures and greenhouse gas concentrations in the Eemian, making it the best analogue for future climate change on Earth. An international study released by the National Oceanic and Atmospheric Administration last week showed the first decade of the 21st century was the warmest on record for the planet.

The NEEM project involves 300 scientists and students and is led by Professor Dorthe Dahl-Jensen, director of the University of Copenhagen’s Centre of Ice and Climate. The United States portion of the effort is funded by the National Science Foundation’s Office of Polar Programs.

The two meters of ice just above bedrock from NEEM — which is located at one of the most inaccessible parts of the Greenland ice sheet — go beyond the Eemian interglacial period into the previous ice age and contains rocks and other material that have not seen sunlight for hundreds of thousands of years, said White. The researchers expect the cores to be rich in DNA and pollen that can tell scientists about the plants that existed in Greenland before it became covered with ice.

The cores samples are being studied in detail using a suite of measurements, including stable water isotopes that reveal information about temperature and moisture changes back in time. The team is using state-of-the art laser instruments to measure the isotopes, as well as atmospheric gas bubbles trapped in the ice and ice crystals to understand past variations in climate on a year-by-year basis, said White.

As part of the project, the researchers want to determine how much smaller the Greenland ice sheet was 120,000 years ago when the temperatures were higher than present, as well as how much and how fast the Greenland ice sheet contributed to sea level. “We expect that our findings will increase our knowledge on the future climate system and increase our ability to predict the speed and final height of sea level rise during the Eemian,” said Dahl-Jensen.

The NEEM facility includes a large dome, a drilling rig to extract 3-inch in diameter ice cores, drilling trenches, labs and living quarters. The United States is leading the laboratory analysis of atmospheric gases trapped in bubbles within the cores, including greenhouse gases like carbon dioxide and methane.

Other nations involved in NEEM include Belgium, Canada, France, Germany, Iceland, Japan, Korea, the Netherlands, Sweden, Switzerland and the United Kingdom. Other U.S. institutions involved in the effort include Oregon State University, Penn State, the University of California, San Diego and Dartmouth College.

Other CU-Boulder participants include postdoctoral researcher Vasilii Petrenko and doctoral student Tyler Jones. White also is a professor in CU-Boulder’s geological sciences department.

The vast majority of climate scientists attribute rising temperatures on Earth to increased greenhouse gases pumped into the atmosphere as a result of human activity. In 2008 The Intergovernmental Panel on Climate Change concluded that temperatures on Earth could rise by as much as 10 degrees F above today’s temperatures in the next century, primarily due to atmospheric greenhouse gases.

Oxygen fuels the fires of time

Variations in the Earth’s atmospheric oxygen levels are thought to be closely linked to the evolution of life, with strong feedbacks between uni- and multicellular life and oxygen. Over the past 400 million years the level of oxygen has varied considerably from the 21% value we have today. Scientists from The Field Museum in Chicago and Royal Holloway University of London publishing their results this week in the journal Nature Geoscience have shown that the amount of charcoal preserved in ancient peat bogs, now coal, gives a measure of how much oxygen there was in the past.

Until now scientists have relied on geochemical models to estimate atmospheric oxygen concentrations. However, a number of competing models exist, each with significant discrepancies and no clear way to resolve an answer. All models agree that around 300 million years ago in the Late Paleozoic atmospheric oxygen levels were much higher than today. These elevated concentrations have been linked to gigantism in some animal groups, in particular insects, the dragonfly Meganeura monyi with a wingspan of over two feet epitomizing this. Some scientists think these higher concentrations of atmospheric oxygen may also have allowed vertebrates to colonize the land.

These higher levels of oxygen were a direct consequence of the colonization of land by plants. When plants photosynthesize they evolve oxygen. However, when the carbon stored in plant tissues decays atmospheric oxygen is used up. To produce a net increase in atmospheric oxygen over time organic matter must be buried. The colonization of land by plants not only led to new plant growth but also a dramatic increase in the burial of carbon. This burial was particularly high during the Late Paleozoic when huge coal deposits accumulated.

Dr. Ian J. Glasspool from the Department of Geology at the Field Museum explained that: “Atmospheric oxygen concentration is strongly related to flammability. At levels below 15% wildfires could not have spread. However, at levels significantly above 25% even wet plants could have burned, while at levels around 30 to 35%, as have been proposed for the Late Paleozoic, wildfires would have been frequent and catastrophic”.

The researchers, including Professor Andrew C. Scott from the Royal Holloway University of London, have shown that charcoal found in coal has remained at concentrations of around 4-8% over the past 50 million years indicating near to present levels of atmospheric oxygen. However, there were periods in Earth History when the charcoal percentage in the coals was as high as 70%. This indicates very high levels of atmospheric oxygen that would have promoted many frequent, large, and extremely hot fires. These intervals include the Carboniferous and Permian Periods from 320-250 million years ago and the Middle Cretaceous Period approximately 100 million years ago.

“It is interesting”, Professor Scott points out, “that these were times of major change in the evolution of vegetation on land with the evolution and spread of new plant groups, the conifers in the late Carboniferous and flowering plants in the Cretaceous”. These periods of high fire resulting from elevated atmospheric oxygen concentration might have been self-perpetuating with more fire meaning greater plant mortality, and in turn more erosion and therefore greater burial of organic carbon which would have then promoted elevated atmospheric oxygen concentrations. “The mystery to us”, Scott states, “is why oxygen levels appear to have more or less stabilized about 50 million years ago”.

Researchers test cutting-edge technology for underwater mapping at Tahoe basin

A borrowed boat, a small mountain lake and the inaugural run of a half-a-million dollar state-of-the-art multi-beam sonar system made history this month with the successful high-definition mapping by University of Nevada, Reno, and Scripps Institution of Oceanography researchers of the bottom of Fallen Leaf Lake, a tributary lake just upstream from Lake Tahoe. -  Photo by Mike Wolterbeek, University of Nevada, Reno
A borrowed boat, a small mountain lake and the inaugural run of a half-a-million dollar state-of-the-art multi-beam sonar system made history this month with the successful high-definition mapping by University of Nevada, Reno, and Scripps Institution of Oceanography researchers of the bottom of Fallen Leaf Lake, a tributary lake just upstream from Lake Tahoe. – Photo by Mike Wolterbeek, University of Nevada, Reno

A borrowed boat, a small mountain lake and the inaugural run of a half-a-million dollar state-of-the-art multi-beam sonar system made history this month with the successful high-definition mapping of the bottom of Fallen Leaf Lake, a tributary lake just upstream from Lake Tahoe.

“The clarity of the images we produced is unmatched in detail,” said University of Nevada, Reno Seismology Lab Director Graham Kent and co-lead investigator of the project. “We can clearly see 1,000-year-old trees standing upright under 100 feet of water and remnants of earthquake activity along the West Tahoe Fault line. This is a valuable tool for a number of scientific pursuits.”

What the scientists can see:

  • Fault mapping such as the West Tahoe Fault which runs through Fallen Leaf Lake – it’s a magnitude 7.3 capable normal fault that’s approaching the end its characteristic earthquake cycle (almost overdue)
  • The effects of drought, including the Medieval Warm Period (approximately 950-1250 AD); features include: old shorelines at 80- to140-feet underwater; and standing, rooted trees at 110-foot level below the lake’s current surface
  • Substrate identification that has potential uses for biohabitat mapping of various aquatic species, both native and invasive

“The centerpiece of the system comes from rocket technology, with an inertial guidance/gyro system, which allows image stability even as the boat rocks back and forth in the waves,” said Kent, also a professor in the University’s College of Science. “It’s also positioned with a phased GPS array and sound velocity corrections to align or properly register lake-floor pixels. It’s a half-million dollar acoustic system, but mo
st of the cost is in the guidance system.”

While there are many commercial applications of this type of mapping, this system is owned by only a handful of academic institutions worldwide. The technology allows for several centimeter depth resolution (with less than one-meter spatial resolution), giving definition similar to airborne lidar.

“This system helps document the best estimate of how severe the Medieval Warm Period drought was, with perhaps 40 percent less precipitation than we get today, for more than two centuries,” Kent said. “It’s disturbing to think it could happen again. This is possibly the best estimate of medieval drought anywhere in the Sierra.”

Kent and his colleagues from Scripps Institution of Oceanography in San Diego, Calif., geophysicists Jeff Babcock and Neal Driscoll, have been studying the glacially carved lake bottom in conjunction with seismic studies at Lake Tahoe for nearly a decade, and they are excited to use the new tool they have developed to continue and enhance those studies.

“Not only are we using this cutting-edge system to map the geologic substrate but we can use this, for example, to quickly find potential habitat for invasive species at Lake Tahoe such as the Asian Clam,” Kent said.

These expeditions also provide an ideal environment to train the next generation of research scientists; two graduate students, one from the University and one from SIO, participated in the mapping. The team has also been joined by Emeritus Professor John Kleppe from the University’s College of Engineering, who was one of the first to document the submerged trees beneath Fallen Leaf, and his involvement has been significant in both the science and educational aspects of this project.

The Fallen Leaf Lake area was the largest unmapped region of the Tahoe Basin. The lake is three miles long and one mile wide, and the surface is about 150 feet higher in elevation than Lake Tahoe. The lake is about 415 feet deep at its deepest point.

The team has mapped lakes and shallow-seas such as Pyramid Lake, Lake Tahoe, Salton Sea and the Great Salt Lake to name a few of their latest endeavors.