Warm US West, cold East: A 4,000-year pattern

<IMG SRC="/Images/485889256.jpg" WIDTH="350" HEIGHT="262" BORDER="0" ALT="University of Utah geochemist Gabe Bowen led a new study, published in Nature Communications, showing that the curvy jet stream pattern that brought mild weather to western North America and intense cold to the eastern states this past winter has become more dominant during the past 4,000 years than it was from 8,000 to 4,000 years ago. The study suggests global warming may aggravate the pattern, meaning such severe winter weather extremes may be worse in the future. – Lee J. Siegel, University of Utah.”>
University of Utah geochemist Gabe Bowen led a new study, published in Nature Communications, showing that the curvy jet stream pattern that brought mild weather to western North America and intense cold to the eastern states this past winter has become more dominant during the past 4,000 years than it was from 8,000 to 4,000 years ago. The study suggests global warming may aggravate the pattern, meaning such severe winter weather extremes may be worse in the future. – Lee J. Siegel, University of Utah.

Last winter’s curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, and suggests it may worsen as Earth’s climate warms.

“If this trend continues, it could contribute to more extreme winter weather events in North America, as experienced this year with warm conditions in California and Alaska and intrusion of cold Arctic air across the eastern USA,” says geochemist Gabe Bowen, senior author of the study.

The study was published online April 16 by the journal Nature Communications.

“A sinuous or curvy winter jet stream means unusual warmth in the West, drought conditions in part of the West, and abnormally cold winters in the East and Southeast,” adds Bowen, an associate professor of geology and geophysics at the University of Utah. “We saw a good example of extreme wintertime climate that largely fit that pattern this past winter,” although in the typical pattern California often is wetter.

It is not new for scientists to forecast that the current warming of Earth’s climate due to carbon dioxide, methane and other “greenhouse” gases already has led to increased weather extremes and will continue to do so.

The new study shows the jet stream pattern that brings North American wintertime weather extremes is millennia old – “a longstanding and persistent pattern of climate variability,” Bowen says. Yet it also suggests global warming may enhance the pattern so there will be more frequent or more severe winter weather extremes or both.

“This is one more reason why we may have more winter extremes in North America, as well as something of a model for what those extremes may look like,” Bowen says. Human-caused climate change is reducing equator-to-pole temperature differences; the atmosphere is warming more at the poles than at the equator. Based on what happened in past millennia, that could make a curvy jet stream even more frequent and-or intense than it is now, he says.

Bowen and his co-authors analyzed previously published data on oxygen isotope ratios in lake sediment cores and cave deposits from sites in the eastern and western United States and Canada. Those isotopes were deposited in ancient rainfall and incorporated into calcium carbonate. They reveal jet stream directions during the past 8,000 years, a geological time known as middle and late stages of the Holocene Epoch.

Next, the researchers did computer modeling or simulations of jet stream patterns – both curvy and more direct west to east – to show how changes in those patterns can explain changes in the isotope ratios left by rainfall in the old lake and cave deposits.

They found that the jet stream pattern – known technically as the Pacific North American teleconnection – shifted to a generally more “positive phase” – meaning a curvy jet stream – over a 500-year period starting about 4,000 years ago. In addition to this millennial-scale change in jet stream patterns, they also noted a cycle in which increases in the sun’s intensity every 200 years make the jet stream flatter.

Bowen conducted the study with Zhongfang Liu of Tianjin Normal University in China, Kei Yoshimura of the University of Tokyo, Nikolaus Buenning of the University of Southern California, Camille Risi of the French National Center for Scientific Research, Jeffrey Welker of the University of Alaska at Anchorage, and Fasong Yuan of Cleveland State University.

The study was funded by the National Science Foundation, National Natural Science Foundation of China, Japan Society for the Promotion of Science and a joint program by the society and Japan’s Ministry of Education, Culture, Sports, Science and Technology: the Program for Risk Information on Climate Change.

Sinuous Jet Stream Brings Winter Weather Extremes

The Pacific North American teleconnection, or PNA, “is a pattern of climate variability” with positive and negative phases, Bowen says.

“In periods of positive PNA, the jet stream is very sinuous. As it comes in from Hawaii and the Pacific, it tends to rocket up past British Columbia to the Yukon and Alaska, and then it plunges down over the Canadian plains and into the eastern United States. The main effect in terms of weather is that we tend to have cold winter weather throughout most of the eastern U.S. You have a freight car of arctic air that pushes down there.”

Bowen says that when the jet stream is curvy, “the West tends to have mild, relatively warm winters, and Pacific storms tend to occur farther north. So in Northern California, the Pacific Northwest and parts of western interior, it tends to be relatively dry, but tends to be quite wet and unusually warm in northwest Canada and Alaska.”

This past winter, there were times of a strongly curving jet stream, and times when the Pacific North American teleconnection was in its negative phase, which means “the jet stream is flat, mostly west-to-east oriented,” and sometimes split, Bowen says. In years when the jet stream pattern is more flat than curvy, “we tend to have strong storms in Northern California and Oregon. That moisture makes it into the western interior. The eastern U.S. is not affected by arctic air, so it tends to have milder winter temperatures.”

The jet stream pattern – whether curvy or flat – has its greatest effects in winter and less impact on summer weather, Bowen says. The curvy pattern is enhanced by another climate phenomenon, the El Nino-Southern Oscillation, which sends a pool of warm water eastward to the eastern Pacific and affects climate worldwide.

Traces of Ancient Rains Reveal Which Way the Wind Blew

Over the millennia, oxygen in ancient rain water was incorporated into calcium carbonate deposited in cave and lake sediments. The ratio of rare, heavy oxygen-18 to the common isotope oxygen-16 in the calcium carbonate tells geochemists whether clouds that carried the rain were moving generally north or south during a given time.

Previous research determined the dates and oxygen isotope ratios for sediments in the new study, allowing Bowen and colleagues to use the ratios to tell if the jet stream was curvy or flat at various times during the past 8,000 years.

Bowen says air flowing over the Pacific picks up water from the ocean. As a curvy jet stream carries clouds north toward Alaska, the air cools and some of the water falls out as rain, with greater proportions of heavier oxygen-18 falling, thus raising the oxygen-18-to-16 ratio in rain and certain sediments in western North America. Then the jet stream curves south over the middle of the continent, and the water vapor, already depleted in oxygen-18, falls in the East as rain with lower oxygen-18-to-16 ratios.

When the jet stream is flat and moving east-to-west, oxygen-18 in rain is still elevated in the West and depleted in the East, but the difference is much less than when the jet stream is curvy.

By examining oxygen isotope ratios in lake and cave sediments in the West and East, Bowen and colleagues showed that a flatter jet stream pattern prevailed from about 8,000 to 4,000 years ago in North America, but then, over only 500 years, the pattern shifted so that curvy jet streams became more frequent or severe or both. The method can’t distinguish frequency from severity.

The new study is based mainly on isotope ratios at Buckeye Creek Cave, W. Va.; Lake Grinell, N.J.; Oregon Caves National Monument; and Lake Jellybean, Yukon.

Additional data supporting increasing curviness of the jet stream over recent millennia came from seven other sites: Crawford Lake, Ontario; Castor Lake, Wash.; Little Salt Spring, Fla.; Estancia Lake, N.M.; Crevice Lake, Mont.; and Dog and Felker lakes, British Columbia. Some sites provided oxygen isotope data; others showed changes in weather patterns based on tree ring growth or spring deposits.

Simulating the Jet Stream

As a test of what the cave and lake sediments revealed, Bowen’s team did computer simulations of climate using software that takes isotopes into account.

Simulations of climate and oxygen isotope changes in the Middle Holocene and today resemble, respectively, today’s flat and curvy jet stream patterns, supporting the switch toward increasing jet stream sinuosity 4,000 years ago.

Why did the trend start then?

“It was a when seasonality becomes weaker,” Bowen says. The Northern Hemisphere was closer to the sun during the summer 8,000 years ago than it was 4,000 years ago or is now due to a 20,000-year cycle in Earth’s orbit. He envisions a tipping point 4,000 years ago when weakening summer sunlight reduced the equator-to-pole temperature difference and, along with an intensifying El Nino climate pattern, pushed the jet stream toward greater curviness.

Rising mountains dried out Central Asia, scientists say

A record of ancient rainfall teased from long-buried sediments in Mongolia is challenging the popular idea that the arid conditions prevalent in Central Asia today were caused by the ancient uplift of the Himalayas and the Tibetan Plateau.

Instead, Stanford scientists say the formation of two lesser mountain ranges, the Hangay and the Altai, may have been the dominant drivers of climate in the region, leading to the expansion of Asia’s largest desert, the Gobi. The findings will be presented on Thursday, Dec. 12, at the annual meeting of the American Geophysical Union (AGU) in San Francisco.

“These results have major implications for understanding the dominant factors behind modern-day Central Asia’s extremely arid climate and the role of mountain ranges in altering regional climate,” said Page Chamberlain, a professor of environmental Earth system science at Stanford.

Scientists previously thought that the formation of the Himalayan mountain range and the Tibetan plateau around 45 million years ago shaped Asia’s driest environments.

“The traditional explanation has been that the uplift of the Himalayas blocked air from the Indian Ocean from reaching central Asia,” said Jeremy Caves, a doctoral student in Chamberlain’s terrestrial paleoclimate research group who was involved in the study.

This process was thought to have created a distinct rain shadow that led to wetter climates in India and Nepal and drier climates in Central Asia. Similarly, the elevation of the Tibetan Plateau was thought to have triggered an atmospheric process called subsidence, in which a mass of air heated by a high elevation slowly sinks into Central Asia.

“The falling air suppresses convective systems such as thunderstorms, and the result is you get really dry environments,” Caves said.

This long-accepted model of how Central Asia’s arid environments were created mostly ignores, however, the existence of the Altai and Hangay, two northern mountain ranges.

Searching for answers


To investigate the effects of the smaller ranges on the regional climate, Caves and his colleagues from Stanford and Rocky Mountain College in Montana traveled to Mongolia in 2011 and 2012 and collected samples of ancient soil, as well as stream and lake sediments from remote sites in the central, southwestern and western parts of the country.

The team carefully chose its sites by scouring the scientific literature for studies of the region conducted by pioneering researchers in past decades.

“A lot of the papers were by Polish and Russian scientists who went there to look for dinosaur fossils,” said Hari Mix, a doctoral student at Stanford who also participated in the research. “Indeed, at many of the sites we visited, there were dinosaur fossils just lying around.”

The earlier researchers recorded the ages and locations of the rocks they excavated as part of their own investigations; Caves and his team used those age estimates to select the most promising sites for their own study.

At each site, the team bagged sediment samples that were later analyzed to determine their carbon isotope content. The relative level of carbon isotopes present in a soil sample is related to the productivity of plants growing in the soil, which is itself dependent on the annual rainfall. Thus, by measuring carbon isotope amounts from different sediment samples of different ages, the team was able to reconstruct past precipitation levels.

An ancient wet period


The new data suggest that rainfall in central and southwestern Mongolia had decreased by 50 to 90 percent in the last several tens of million of years.

“Right now, precipitation in Mongolia is about 5 inches annually,” Caves said. “To explain our data, rainfall had to decrease from 10 inches a year or more to its current value over the last 10 to 30 million years.”

That means that much of Mongolia and Central Asia were still relatively wet even after the formation of the Himalayas and the Tibetan Plateau 45 million years ago. The data show that it wasn’t until about 30 million years ago, when the Hangay Mountains first formed, that rainfall started to decrease. The region began drying out even faster about 5 million to 10 million years ago, when the Altai Mountains began to rise.

The scientists hypothesize that once they formed, the Hangay and Altai ranges created rain shadows of their own that blocked moisture from entering Central Asia.

“As a result, the northern and western sides of these ranges are wet, while the southern and eastern sides are dry,” Caves said.

The team is not discounting the effect of the Himalayas and the Tibetan Plateau entirely, because portions of the Gobi Desert likely already existed before the Hangay or Altai began forming.

“What these smaller mountains did was expand the Gobi north and west into Mongolia,” Caves said.

The uplift of the Hangay and Altai may have had other, more far-reaching implications as well, Caves said. For example, westerly winds in Asia slam up against the Altai today, creating strong cyclonic winds in the process. Under the right conditions, the cyclones pick up large amounts of dust as they snake across the Gobi Desert. That dust can be lofted across the Pacific Ocean and even reach California, where it serves as microscopic seeds for developing raindrops.

The origins of these cyclonic winds, as well as substantial dust storms in China today, may correlate with uplift of the Altai, Caves said. His team plans to return to Mongolia and Kazakhstan next summer to collect more samples and to use climate models to test whether the Altai are responsible for the start of the large dust storms.

“If the Altai are a key part of regulating Central Asia’s climate, we can go and look for evidence of it in the past,” Caves said.

Borneo stalagmites provide new view of abrupt climate events over 100,000 years

Georgia Tech researchers Stacy Carolin (Ph.D. candidate), Jessica Moerman (Ph.D. candidate), Eleanor Middlemas (undergraduate), Danja Mewes (undergraduate) and two caving guides (Syria Lejau, Jenny Malang) climb out from Cobweb Cave in Gunung Mulu National Park after a day of rock and water sample collection during the Fall 2012 field trip. -  Credit: Kim Cobb
Georgia Tech researchers Stacy Carolin (Ph.D. candidate), Jessica Moerman (Ph.D. candidate), Eleanor Middlemas (undergraduate), Danja Mewes (undergraduate) and two caving guides (Syria Lejau, Jenny Malang) climb out from Cobweb Cave in Gunung Mulu National Park after a day of rock and water sample collection during the Fall 2012 field trip. – Credit: Kim Cobb

A new set of long-term climate records based on cave stalagmites collected from tropical Borneo shows that the western tropical Pacific responded very differently than other regions of the globe to abrupt climate change events. The 100,000-year climate record adds to data on past climate events, and may help scientists assess models designed to predict how the Earth’s climate will respond in the future.

The new record resulted from oxygen isotope analysis of more than 1,700 calcium carbonate samples taken from four stalagmites found in three different northern Borneo caves. The results suggest that climate feedbacks within the tropical regions may amplify and prolong abrupt climate change events that were first discovered in the North Atlantic.

The results were scheduled to be published June 6 in Science Express, the electronic advance online publication of the journal Science, and will appear later in an issue of printed publication. The research was supported by the National Science Foundation.

Today, relatively subtle changes in the tropical Pacific’s ocean and atmosphere have profound effects on global climate. However, there are few records of past climate changes in this key region that have the length, resolution and age controls needed to reveal the area’s response to abrupt climate change events.

“This is a new record from a very important area of the world,” said Kim Cobb, an associate professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. “This record will provide a new piece of the puzzle from the tropical Pacific showing us how that climate system has responded to forcing events over the past 100,000 years.”

Among the findings were some surprises that show just how complicated the Earth’s climate system can be. While the stalagmite record reflected responses to abrupt changes known as Heinrich events, another major type of event – known as Dansgaard-Oeschger excursions – left no evidence in the Borneo stalagmites. Both types of abrupt climate change events are prominently featured in a previously-published stalagmite climate record from China – which is only slightly north of Borneo.

“To my knowledge, this is the first record that so clearly shows sensitivity to one set of major abrupt climate change events and not another,” said Cobb. “These two types of abrupt change events appear to have different degrees of tropical Pacific involvement, and because the tropical Pacific speaks with such a loud voice when it does speak, we think this is extremely important for understanding the mechanisms underlying these events.”

The researchers were also surprised to discover a very large and abrupt signal in their stalagmite climate records precisely when super-volcano Toba erupted nearby, roughly 74,000 years ago.

The team recovered the stalagmites from caves in Gunung Mulu and Gunung Buda National Parks, in northern Borneo, which is located a few degrees north of the Equator in the western Pacific. Back at their Georgia Tech lab, they analyzed the stalagmites for the ratio of oxygen isotopes contained in samples of calcium carbonate, the material from which the stalagmites were formed. That ratio is set by the oxygen isotopes in rainfall at the site, as the water that seeped into the ground dissolved limestone rock and dripped into the caves to form the stalagmites. The stalagmites accumulate at a rate of roughly one centimeter every thousand years.

“Stalagmites are time capsules of climate signals from thousands of years in the past,” said Stacy Carolin, a Georgia Tech Ph.D. candidate who gathered and analyzed the stalagmites. “We have instrumental records of climate only for the past 100 years or so, and if we want to look deeper into the past, we have to find records like these that locked in climate signals we can extract today.”

In the laboratory, Carolin sawed each stalagmite in half, opening it like a hot dog bun. She then used a tiny drill bit to take samples of the calcium carbonate down the center at one-millimeter steps. Because the stalagmites grew at varying rates, each sample represented as little as 60 years of time, or as much as 200 years. The precise ages of the samples were determined by measuring uranium and thorium isotope ratios, an analysis done with the help of Jess F. Adkins, a professor at the California Institute of Technology and a co-author of the study.

Rainfall oxygen isotopic ratios are good indicators of the amount of rainfall occurring throughout the region, as determined by a modern-day calibration study recently published by another graduate student in Cobb’s lab.

Merging data from the four different stalagmites provided a record of precipitation trends in the western Pacific over the past 100,000 years. That information can be compared to stalagmite and ice core climate records obtained elsewhere in the world.

“This record, which spans the entire last glacial period, adds significantly to the understanding of how various climate forcings are felt by the western tropical Pacific,” Carolin added.

Climate scientists are interested in learning more about abrupt climate changes because they indicate that the climate system may have “tipping points.” So far, the climate system has responded to rising carbon dioxide levels at a fairly steady rate, but many scientists worry about possible nonlinear effects.

“As a society, we haven’t really thought enough about the fact that we are moving Earth’s climate system toward a new state very quickly,” said Cobb. “It’s important to remember that the climate system has important nonlinearities that are most evident in these abrupt climate events. Ultimately, we’d like to be able to reproduce the global signatures of these abrupt climate events with numerical models of the climate system, and investigate the physics that drive such events.”

For Carolin, studying the half-meter-long stalagmites brought an awareness that the Earth has not always been as we know it today.

“You have to be impressed with the scope of what you are studying, and recognize that the state our climate is in today is incredibly different from Earth’s climate during the last Ice Age,” she said. “As we consider how humans may be affecting climate, dissecting what was going on tens of thousands of years ago in all regions of the globe can help scientists better predict how the Earth will respond to modern climate forcings.”

Caves point to thawing of Siberia

Evidence from Siberian caves suggests that a global temperature rise of 1.5 degrees Celsius could see permanently frozen ground thaw over a large area of Siberia, threatening release of carbon from soils, and damage to natural and human environments.

A thaw in Siberia’s permafrost (ground frozen throughout the year) could release over 1000 giga-tonnes of the greenhouse gases carbon dioxide and methane into the atmosphere, potentially enhancing global warming.

The data comes from an international team led by Oxford University scientists studying stalactites and stalagmites from caves located along the ‘permafrost frontier’, where ground begins to be permanently frozen in a layer tens to hundreds of metres thick. Because stalactites and stalagmites only grow when liquid rainwater and snow melt drips into the caves, these formations record 500,000 years of changing permafrost conditions, including warmer periods similar to the climate of today.

Records from a particularly warm period (Marine Isotopic Stage 11) that occurred around 400,000 years ago suggest that global warming of 1.5°C compared to the present is enough to cause substantial thawing of permafrost far north from its present-day southern limit.

A report of the research is published in this week’s Science Express. The team included scientists from Britain, Russia, Mongolia and Switzerland.

‘The stalactites and stalagmites from these caves are a way of looking back in time to see how warm periods similar to our modern climate affect how far permafrost extends across Siberia,’ said Dr Anton Vaks of Oxford University’s Department of Earth Sciences, who led the work. ‘As permafrost covers 24% of the land surface of the Northern hemisphere significant thawing could affect vast areas and release giga-tonnes of carbon.

‘This has huge implications for ecosystems in the region, and for aspects of the human environment. For instance, natural gas facilities in the region, as well as power lines, roads, railways and buildings are all built on permafrost and are vulnerable to thawing. Such a thaw could damage this infrastructure with obvious economic implications.’

The team used radiometric dating techniques to date the growth of cave formations (stalactites and stalagmites). Data from the Ledyanaya Lenskaya Cave – near the town of Lensk latitude 60°N – in the coldest region showed that the only period when stalactite growth took place occurred about 400,000 years ago, during a period with a global temperature 1.5°C higher than today. Periods when the world was 0.5-1°C warmer than today did not see any stalactite growth in this northernmost cave, suggesting that around 1.5°C is the ‘tipping point’ at which the coldest permafrost regions begin to thaw.

Dr Vaks said: ‘Although it wasn’t the main focus of our research our work also suggests that in a world 1.5°C warmer than today, warm enough to melt the coldest permafrost, adjoining regions would see significant changes with Mongolia’s Gobi Desert becoming much wetter than it is today and, potentially, this extremely arid area coming to resemble the present-day Asian steppes.’

Researcher finds key to ancient weather patterns in Florida’s caves

This is Darrel Tremaine, a Florida State doctoral student. -  FSU Photography Services, Bill Lax
This is Darrel Tremaine, a Florida State doctoral student. – FSU Photography Services, Bill Lax

Darrel Tremaine has been known to go to extremes for his research, such as crawling on his hands and knees through a dark, muddy limestone cave in Northwest Florida to learn more about the weather thousands of years ago.

His goal? To compare ancient meteorological patterns with modern ones in the northern Gulf of Mexico region and ultimately inform policymakers on how to build a sustainable water supply.

On a recent morning, the Florida State University doctoral student in oceanography huddled with artisan Charlie Scott-Smith at Florida State’s Master Craftsman Studios (http://craft.fsu.edu/). The two were making molds of stalagmites, the natural formations rising from the floor of limestone caves that are formed by the dripping of water containing calcium carbonate. (Their counterparts, stalactites, hang from the ceilings of such caves.)
Video: Digging deep to study ancient climate

Surrounded by the studio’s eye-catching artifacts – models of architectural fittings, an ancient ship, even a copy of the sculpture “Winged Victory” from the Louvre Museum – Tremaine and Scott-Smith worked with a rubbery urethane compound to create stalagmite molds that resembled giant beeswax candles. Next, they filled the molds with cement and glass.

After the cement thoroughly dried, Tremaine returned the reproduction stalagmites to the cave, where, over time, dripping water will coat them with calcite and they will start growing again. The remote, Northwest Florida cave maintains a constant, year-round temperature of 72 degrees and a 100 percent relative humidity level, which means, as Tremaine likes to joke, “that if you start to sweat, you stay wet.”

As part of a three-year climate research project, he harvested the two stalagmites – one 4,000 years old, the other 25,000 years old – from the cave to analyze them for isotopic and trace element variations in an effort to build a 4,000-year paleo-rainfall record for North Florida. In a unique arrangement with the Southeastern Cave Conservancy Inc. (SCCI), a nonprofit group that owns dozens of caves in the southeastern United States, he was allowed to take the stalagmites as long as he made duplicates of them and placed the duplicates back in the cave – a measure of cave conservation.

The real stalagmites will be studied at the National High Magnetic Field Laboratory (http://www.magnet.fsu.edu/) at Florida State, where Tremaine, a graduate research assistant, is currently stationed in the geochemistry lab.

So far, Tremaine has been scrutinizing carbon, oxygen and strontium isotopes on modern calcite grown in the cave on glass microscope slides – what he calls “modern calibrations of ancient proxies.” Isotopes of an element are atoms with the same number of protons but different number of neutrons, thus a slightly different atomic mass. He will use that data to get a better idea of ancient ventilation patterns, the temperature inside of a cave when the stalagmites were forming, what type of vegetation was growing above the cave, of, and whether the weather was cold, warm or hot during a particular span of time.

“By looking at trace elements we can get an idea of very wet and very dry rainfall patterns and cycles,” Tremaine said. “We’ll better understand severe weather patterns.”

Tremaine, along with a six-member team of scientists, researchers and graduate students, will cut the stalagmites in half and then use a 50-micron laser to vaporize calcite that they will then measure with a spectrometer. The laser will allow them to study monthly weather patterns in the Northern Gulf Region thousands of years ago. By extracting calcite powders with a half-millimeter drill bit, they will examine the region’s wet and dry seasons in five-year increments. Eventually, they hope to create a high-resolution time series, analyzing monthly weather patterns over thousands of years.

“We will be the first to do this in the southeastern United States,” he explained. “The research is very important because we will be able to study our monsoonal weather patterns, which are much like India and China, with very wet and dry seasons. “

Tremaine’s six-member climate research team includes a wide swath of experts, from a retired professor to a Russian mathematician and an undergraduate cave researcher. They are Florida State faculty members Philip “Flip” Froelich, retired FSU Francis Eppes Professor of Oceanography; Bill Burnett, the Carl Henry Oppenheimer Professor of Oceanography; and Doron Nof, Distinguished Nansen Professor of Physical Oceanography. In addition, Guy “Harley” Means, assistant state geologist at the Florida Geological Survey; Brian Kilgore, a Florida State undergraduate majoring in biochemistry; and Karina Khazmutdinova, a mathematician and doctoral student at the FSU Geophysical Fluid Dynamics Institute, served on the team.

Their research work on isotopes was recently published in the journal Geochimica et Cosmochimica Acta. Tremaine and his team’s research on trace elements also will soon be published in the same research journal. They are also in the process of writing an article for the Journal of Hydrology.

“Records of past climates can be found in the ice caps and in the deep sea,” said Jeff Chanton, FSU’s John W. Winchester Professor of Oceanography, who has worked with Tremaine. “The unique aspect of Darrel’s work is that it will give us a record of local climate right here on the Northern Gulf Coast. This is important because a record of past climate in our region would help to predict what’s to come in response to human disturbances of atmospheric greenhouse gas concentrations.”

The 32-year-old Tremaine, who holds a master’s degree in oceanography from Florida State and an undergraduate degree in engineering from the University of Cincinnati, dreams of someday starting his own groundwater research lab, where he would also teach middle and high school students to do research.

“Working with younger kids and teaching them to do research early makes sense, because if we inform them, they will someday inform us,” he said.

But first, Tremaine and his team recently negotiated permission from the state of Florida to move their cave-monitoring equipment into one of the most pristine and highly guarded caves in Florida Caverns State Park, located near the Panhandle town of Marianna. Tremaine has already been in the cave for preliminary investigations, and the team began installing equipment in November.

Not easy work, by any means: “No one,” Tremaine explained one morning while he helped Florida State Master Craftsman artisans put the final touches on the stalagmite molds, “has been in that cave since 2006.”

Tourism does not harm all caves

Despite the high number of tourists, the large size of the cave means the thermal signal disperses very quickly and gently. -  David Domínguez Villar et al.
Despite the high number of tourists, the large size of the cave means the thermal signal disperses very quickly and gently. – David Domínguez Villar et al.

Unlike the situation in other caves, damage caused by tourists at the Águila cave in Ávila, Spain is “imperceptible”, despite it receiving tens of thousands of visitors each year. This is the main conclusion of an international research study headed by the University of Alcalá (UAH), which measured heat variations in the cave.

“Despite the tens of thousands of visitors that the Águila Cave receives each year, the temperature variations in it are related to the weather outside, while the long-term impact of tourism is virtually non-existent”, David Domínguez Villar, researcher at the Department of Geology of the UAH and lead author of the study published in the journal Acta Carsologica, tells SINC

The research was carried out using data gathered by temperature sensors, which have been fitted in the cave since 2008. These devices make it possible to observe heat variations in the cave, and are very sensitive to the impact of visitors.

“We took data from the cave every 10 minutes and used a filter. The impact of visitor arrivals on temperature increase could be observed immediately. For this reason, we chose the maximum and minimum levels, and we filtered certain periods with or without visitors so that we could differentiate between the natural dynamics of the cave and the impact of the visitors”, says Domínguez.

Despite the high number of tourists, the large size of the cave means the thermal signal disperses very quickly and gently. “This is the opposite of what happens in other caves, such as Altamira, which have a gallery shape, meaning that just a few people have an immense impact”, the expert explains.

The average temperature of the cave was 15.6ºC in 2009, and tourist visits caused thermal anomalies of less than 0.15ºC, with the temperature generally returning to normal overnight.

On days with higher numbers of visitors, the effects of the thermal anomalies lasted “from one day to the next”, and caused temperature increases in the cave for longer periods of time. However, this manmade effect disappeared shortly after the number of tourists fell. In most cases the effect lasted for less than a week.

According to the scientists, the biggest problem in caves with wall paintings is corrosion caused by condensation. “The walls of the Águila cave are also corroded, although it does not have paintings. However, this degradation is due to natural effects. In addition, no condensation-related corrosion can be seen on the stalagmites that are currently growing”, Domínguez adds.

Studying a region’s climate on the basis of a cave

The researchers also intend to study the past climate by using the stalagmites in the cave. “We want to look at how the external and internal temperature is recorded, and see the temperature trends and changes inside the cave”, the researcher adds.

Currently, a certain degree of seasonal change can be seen in the cave, but heat dispersion via rock is much slower than in the air. In fact, the experts say that the thermal signal from outside takes around seven years to reach the inside.

“The temperature records of the cave could be related to the climate of the region, and could be used to reconstruct the temperature of this area, aside from the impact of visitors”, he concludes.

Researchers to explore sacred Maya pools of Belize

The cenotes of central Belize vary in size, depth and accessibility. -  Photo by Lisa Lucero, University of Illinois
The cenotes of central Belize vary in size, depth and accessibility. – Photo by Lisa Lucero, University of Illinois

A team of expert divers, a geochemist and an archaeologist will be the first to explore the sacred pools of the southern Maya lowlands in rural Belize. The expedition, made possible with a grant from the National Geographic Society and led by a University of Illinois archaeologist, will investigate the cultural significance and environmental history and condition of three of the 23 pools of Cara Blanca, in central Belize.

Called cenotes (sen-OH-tays), these groundwater-filled sinkholes in the limestone bedrock were treated as sacred sites by the Maya, said University of Illinois archaeologist Lisa Lucero, who will lead the expedition next spring.

“Any openings in the earth were considered portals to the underworld, into which the ancient Maya left offerings,” said Lucero, who is a professor of anthropology at Illinois. “We know from ethnographic accounts that Maya collected sacred water from these sacred places, mostly from caves.”

Studies of shallow lakes and cenotes in Mexico and Guatemala have found that the Maya also left elaborate offerings in the sacred lakes and pools. Items found on the bottom of lakes in these regions include masks, bells, jade, human remains, figurines and ceramic vessels decorated with animals, plants and the gods of fertility and death.

“Diving the sacred pools of Cara Blanca, in central Belize, is necessary to determine if they have similar sacred qualities,” Lucero said.

Patricia Beddows, a lecturer of earth and planetary sciences at Northwestern University and an expert diver who has explored cenotes on the Yucatan Peninsula of Mexico, will also explore the geochemistry and hydrology of the pools of central Belize.

“Once underwater, we will first have to cut out some of the jungle wood so that we can even reach the bottom,” Beddows said. “After mapping for fragile Maya artifacts, we will also take water data and manually drill sediment cores.”

The sediment samples will provide a record of changes in surface and water conditions, Beddows said.

“Were the Maya challenged by droughts in the area? Did the water quality suddenly go bad due to sulfur or other geologic factors? We hope these cenotes will provide a rich story of linked human and environmental conditions,” she said.

The cenotes vary in depth from 5 to more than 50 meters, Lucero said. The extraordinary depth of some of the pools, their sheer walls, the probable presence of underwater caves that may lead to other pools and the potential for encountering wildlife (a crocodile was spotted in one of the cenotes the team will explore) all add to the complexity and danger of the task, she said. But the team will include some of the most accomplished technical divers in the world and will be in radio contact with British special forces, who train in the region, to coordinate a medical evacuation in the event of a health emergency.

The divers will videotape and map the pools and any artifacts they find.

One of the three pools the researchers will explore has a substantial Maya structure on its edge, likely ceremonial. Preliminary investigations of the structure conducted by archaeologist Andrew Kinkella, of Moorpark College, turned up a lot of jars and the fragments of jars. This could indicate that the site was important for collecting sacred water, Lucero said. She plans to conduct a limited analysis of the structure while the divers explore the pools. Kinkella will join Lucero’s team, and will search the sheer walls of the cenotes for niches, like those carved by the Maya in other pools, where artifacts were deposited.

Lucero has spent more than 20 years studying settlements and sacred sites that were important to the Maya in Belize, and works under the auspices of the Institute of Archeology, which is part of the National Institute of Culture and History, Government of Belize.