‘In the Petri Dish’

Features, Top Stories — By on May 7, 2012 10:54 am
The Antarctic ice shelf. Photo by Tony Rathburn

“Icebergs are everywhere, making it difficult to go where we want to … The wind was HOWLING outside,” Tony Rathburn blogged during a research expedition off the coast of Antarctica. “The ice scraping by the ship sounds like a freight train going by. Occasionally, we bump a piece of ice that resounds through the ship with a bang.”

Rathburn’s journey aboard the research vessel Nathaniel B. Palmer was anything but routine – even for the veteran oceanographer.

Icebergs up to 25 miles long blocked an area where Rathburn, associate professor of geology at Indiana State University, planned to take core samples of the seafloor. He and his students conduct ongoing research on the impact of climate change by studying benthic foraminifera, tiny shelled creatures that are among the most plentiful life forms in the deep sea.

Rathburn’s research focuses on changes during the course of hundreds – even thousands – of years, but there before him, behind him and beside him during much of his April 2006 trek fell striking evidence of climate change in his time. Ice chunks, some more than 10 feet tall, came crashing down on the 60-foot wide deck of the more than 300-foot long ship.

Just four years earlier the ice had been firmly attached to the Antarctic mainland as part of the Larsen B ice shelf. In 2002, more than 1,200 square miles of ice – an area larger than four average Indiana counties combined – broke off and began drifting toward the Weddell Sea.

“Global warming is right there staring you in the face,” Rathburn said. “I hadn’t seen it anywhere else as dramatically evident as in this sector of the Antarctic. Areas that were completely covered with ice, and had been covered with ice for thousands of years, were now open with large sections of the shelf ice system just breaking off.”

One especially large chunk of ice broke off from a nearby glacier, “creating a gigantic wave in the small bay that we were in,” Rathburn said. Unfortunately, some aspects of the research plan had to be altered because the wave caused the Nathanial B. Palmer to rock violently, snapping a 9/16-inch cable supporting core sampling equipment had been lowered into the water. Equipment was lost along with some samples. Although Rathburn returned to Indiana with fewer samples than he planned from that trip, he had pictures and videos that graphically illustrate for students the effects of global warming. 

Tony Rathburn

He has returned to the Antarctic with students twice since that cruise, each time noting the paucity of sea ice even in the coldest month of the Antarctic winter, and documenting seasonal changes in marine ecosystems and environments.

Through long-term studies of foraminifera, Rathburn said his research and that of others in the field of paleoceanography has turned up other, less dramatic, evidence of climate change.

“We can see acidification of the ocean, which is a direct result of carbon dioxide in the atmosphere,” he said. “We see changes in the ocean temperature globally and what that means for sea level change, and the consequences for organisms and their distribution.”

The world’s oceans are in crisis, Rathburn said. Humans have long used open water as a trash dump and have inadvertently turned the deep sea into a dumping ground for carbon dioxide, “severely affecting creatures we depend on for our livelihood,” he said. “If we don’t do something very soon we’re going to lose a lot of the resources that we now enjoy from the sea.”

Iron dust busted

Jennifer Latimer

Jennifer Latimer first became interested in climate change while in high school and grew especially curious after watching a television news report around 1990 that said, “Scientists have found the cure for global warming.”

The idea was that dumping iron in certain parts of the ocean would control carbon dioxide levels in the atmosphere by promoting the growth of algae. It is an idea that some people still promote but Latimer, now an assistant professor of geology and also a paleoceanographer at Indiana State, has found the cure is not that simple.  

The iron fertilization idea has its roots in the long-held scientific thought that as arid and semi-arid regions expanded when glaciers advanced, iron dust blew off continents and fertilized the South Atlantic. Based on her research since a university graduate student in the mid-1990s, Latimer thinks rivers simply dumped general material into the ocean and productivity variations developed as ocean currents distributed that material.

“I don’t know that it was enough to significantly change the amount of carbon dioxide in the atmosphere. So there’s got to be some other kind of mechanism that is contributing to carbon dioxide,” she said.

Ice core samples have shown that, during the past one million years, carbon dioxide levels in the ocean have ranged from 180 parts per million to 280 parts per million, but beginning around 1980, the level shot up to about 380 parts per million,” Latimer said.

“By burning fossil fuels and deforestation, we have fundamentally changed the carbon cycle as it has worked, at least over the last million years.”

Latimer was surprised to discover that iron dust was not responsible for varied productivity in the oceans. While all of the reasons behind climate change – let alone solutions – are not fully understood, continuing research is bringing scientists closer to finding answers.

“Technology is constantly improving,” she said. “When I first started, you could look at a peak in the ice core records and a peak in sediment records and say, ‘Oh yeah, they kind of match up.’ Now we’re able to decipher those wiggles a little more carefully. Sometimes carbon dioxide rises first and sometimes it rises second, so it’s not straightforward. Every day I think we learn something new but it’s a complicated problem. To understand the past, you can better understand the future. It just takes a while and I don’t think we’ve done that yet.” 

Trees tell drought history

Kristen de Graauw examines a core sample from a ponderosa pine tree.

Trees record their own history. Counting the rings on a stump reveals the age of a fallen tree.

But those tree rings can also show the impact of environmental factors on the tree. Wider rings mean the tree enjoyed healthy growth while narrower rings mean the tree suffered under some sort of stress.

Jim Speer, professor of geography and geology at Indiana State, is the author of a textbook on dendrochronology (the study of tree rings) and a past president of the Tree Ring Society. While he and his students generally study tree rings for evidence of insect outbreaks, they also look at whether trees are responding to climate change, such as variations in temperature and/or precipitation.

“Climate will often be the noise in our sample. We frequently will remove the climate signal and look at what remains in the trees to look at other factors,” he said.

Tree ring records from Siberia and northern North America going back about 2,000 years show something happened to that “noise” starting around 1980. The size of tree growth rings, which had been consistent with temperatures, started getting smaller or stayed the same.

“The trees are no longer limited by temperature but are limited by rainfall,” Speer said. “This is called the divergence issue.”

This switching of limiting factors is suggested as part of the basic principles of dendrochronology, but it is an unusual case because temperatures are so high in the arctic compared to past temperatures in the area, he explained. 

Those who deny that climate change is real argue against the ability of trees to record temperature back through time and use the divergence issue as one reason. Speer, while president of the Tree Ring Society, co-wrote a letter defending research by climatologists Michael Mann of Pennsylvania State University, Raymond Bradley of the University of Massachusetts Amherst, and Malcolm Hughes of the University of Arizona, who found temperature changes so dramatic they resembled a hockey stick when plotted on a graph. Other external reviews have since shown that the science was sound.

Jim Speer

Speer’s own research into the impact of insects on ponderosa pine trees in the western United States, with ISU students as collaborators, led to another interesting discovery.

Using 600 years of records for various tree species, Kristen de Graauw, a second-year master’s student in earth and quaternary sciences, found that some periods of slow growth in ponderosa pine, which she and Speer suspected may have been due to Pandora moth outbreaks, were actually due to drought.

“A lot of these pine trees were showing significant suppression in the 1930s and our computer programs were attributing that to insect outbreaks,” de Graauw said. “But anyone who knows anything about the history of the western U.S. knows that in the 1930s we started seeing what’s known as the Dust Bowl.”

Comparing ponderosa pine records against Douglas fir, juniper and oak trees not susceptible to the Pandora moth, de Graauw found the same type of “signal” in the tree records.

“We can only assume then that it was the Dust Bowl that was being recorded,” she said. “The opposite is true, too, so that things that might have been seen as drought events, we were actually showing as insect outbreak events. We have found many sites that are sensitive to Pandora moth outbreaks where suppressions may be due to the insect rather than drought.”     

De Graauw also noted fewer insect outbreaks in the ponderosa pine samples in the past 200 years. Her experience underscores the complexity of research where both droughts and insect outbreaks are recorded, she said.

Weather grows more varied

A thunderstorm rolls across the plains.

Greg Bierly has been known to chase severe weather. The associate professor of geography has piled weather monitoring equipment, students, food and drink into a van and criss-crossed the Midwest and Great Plains in search of thunderstorms.

While he’s put his storm chasing days on hold in recent years after being named director of the University Honors program, Bierly continues to research atmospheric disturbances in his role as director of the ISU Climate Lab. A native of southeastern Indiana, he recently inspected tornado damage at Henryville when he traveled there with other ISU faculty, staff and students to help with storm clean-up.

Bierly’s research has confirmed a period of unusual weather in the eastern United States.

“There is a warming and moistening of the atmosphere, an increase in the frequency of large-scale, low-pressure systems and convective thunderstorms and some increased variability in the weather,” he said of climate data for the eastern United States. “As with the national trend, we’ve had some high-end temperature seasons both winter and summer in the past decade and a half.”

While the severity of tornadoes hasn’t necessarily increased, there is evidence the nation’s so-called “tornado alley” has expanded to the east and south to include states such as Pennsylvania, Virginia and the Carolinas, Bierly said.

Greg Bierly talks with students to plot a course in following storms.

“For the Gulf States, tornadoes have always been a winter phenomenon, but the occurrence there has been more frequent and those states have also become tornado ready a little bit earlier in the season,” he added.

Bierly recently partnered with biology professors Elaina Tuttle and Rusty Gonser to lend a climate change aspect to their long running research into the mating and reproduction of white-throated sparrows in upstate New York.

Tan and white sparrows tend to mate with one another rather than with sparrows of their own color, and Bierly’s research found that the combination of tan males, which are less aggressive, and white females, which are more aggressive, is best suited to produce healthy, viable offspring through all weather extremes – heat, cold, drought or excessive precipitation.

“Thee tan male, white female pairs are more productive in the face of adversity,” he said, citing such variables as nest success, the number of chicks, survivorship. 

“When the female is the more aggressive, robust one that’s fine,” Bierly said. “Even in the winter before they may be foraging a little better and holding their own before the pairing starts. Once they are paired they are best matched with a tan male, a stay-at-home dad, so to speak.”

In contrast, tan females are more susceptible to weather extremes across the spectrum, Bierly said.

Learning from the past

Russ Stafford takes a sherd to examine during an archeology dig.

Humans have had to deal with climate change before. Students in anthropology Professor Russ Stafford’s course on pre-history and climate change learn how pre-humans and early humans adapted through various climate cycles.

When modern humans evolved and migrated out of Africa between 100,000 and 200,000 years ago during an early ice age, “they basically replaced all the earlier species like the Neanderthals because they were better adapted to colder environments, particularly in Europe,” Stafford said.

Humans hunted wooly mammoths, mastodons and wild cats only to have them become extinct when the ice age ended.

“Humans had to adjust their way of life significantly in the warmer, modern period when they shifted more toward plant resources and culture and social organization changed in response to that,” Stafford said. “The rise of civilization and the fall of civilization are tied into climate change.”

History offers examples of what has happened in the past when humans have failed to adapt to climate change. Stafford cited, as an example, Vikings who settled Greenland during the medieval warm period and failed to adapt to the “little ice age” that began about 800 years ago.

Eskimos in Greenland were able to adapt better than the Vikings, Stafford explained, because they were hunters, lived in smaller groups, had a smaller population and had a history in the Arctic going back thousands of years. The Vikings, however, had an agricultural society that was dependent on raising livestock.

“Once the climate got cold, their hayfields weren’t as productive so their livestock died off, and because of cultural constraints of a complex society they were unable to adapt,” he said.

Stafford’s own research focuses on the impact of climate change on prehistoric hunter gatherers who populated what is now the American Midwest between 3,000 and 10,000 years ago.

“There were some dramatic changes in their way of life over that 7,000 years,” he said. “They became more sedentary, for instance. I’ve been looking at whether that can be explained by climate change and, in my opinion, it can be.”

“The rise of civilization and the fall of civilization are tied into climate change.” – Russ Stafford

While the early hunter gatherers were highly mobile, stayed in temporary camps and hunted and gathered a wide range of animals and plants,  becoming more sedentary as forest resources (nuts and deer) became more abundant. Later agricultural people became more dependent on a single food, corn. Their health suffered as a result, Stafford said, and because their populations were larger, they were unable to hunt as much.

From the Vikings of Greenland to the early hunter gatherers of the American heartland, adapting to change has proven essential to survival – or not.

Ocean circulation patterns are nearing the point of severely affecting climate change, making some places colder and other places much warmer, said Tony Rathburn, for whom six years have now come and gone since he first experienced the dramatic impact of climate change off the Antarctic Peninsula.

“Once we’ve passed those thresholds you can’t easily get back to the previous situation,” he said. “We’re not exactly sure where those thresholds are but we’re approaching them, no doubt. We’re basically in the petri dish. We’re the experiment and we really don’t know it’s all going to turn out.”

 Dave Taylor is the director of media relations for Indiana State University.

 

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