Two Iowa State University graduate students are just back from the Gulf of Maine with another big catch of clam shells.
Shelly Griffin and Madelyn Mette recently boarded a lobster boat, dropped a scallop dredge into 30 meters of ocean water and pulled up load after load of Arctica islandica.
"These are the clams that end up in clam chowder," said Alan Wanamaker, an assistant professor of geological and atmospheric sciences in the College of Liberal Arts and Sciences. Wanamaker studies paleoclimatology, the variations and trends of past climates and environments, with the goal of better understanding future climate changes.
The Iowa State researchers only need a few live, meaty clams for their studies. They're really after the old, dead shells. Off the coast of Maine, clams can live up to 240 years, year after year adding another band to their shells, just like a tree adds another growth ring. In the colder waters of the North Atlantic near Iceland, the clams can live up to 500 years, recording even more information in what scientists call annual shell increments.
Wanamaker and his research team bring those shells back to Iowa State's Stable Isotope Laboratory where they're cleaned, sorted, measured, cut, polished, drilled and otherwise prepared for careful microscopic imaging, geochemical testing and radiocarbon analysis.
It turns out those shell increments are a lot like sensors at the bottom of the ocean – they record long records of information about the ocean, including growing conditions, temperatures and circulation patterns.
A paper published by Nature Communications in June 2012 reported how Wanamaker (the lead author) and an international team of researchers used radiocarbon data from shells to determine when clams collected north of Iceland were living in "young" or "old" water. Young water had been at the surface more recently and probably came from the Atlantic. Old water had been removed from the surface much longer and probably came from the Arctic Ocean.
The paper reports warmer, younger water from the Gulf Stream during the warmer Medieval Climate Anomaly from about A.D. 950 to 1250. The paper also reports that shell data showed older, colder water during Europe's Little Ice Age from about A.D. 1550 to 1850.
The researchers' interpretation of the data says the Gulf Stream carrying warm water from the subtropical Atlantic was strong in the medieval era, weakened during the Little Ice Age and strengthened again after A.D. 1940. Those fluctuations amplified the relative warmth and coolness of the times.
Wanamaker said a better understanding of the ocean's past can help researchers understand today's climate trends and changes.
"Is the natural variability only that, or is it influenced by burning fossil fuels?" he said. "Maybe we can understand what will happen in the next 100 years if we understand oceans over the past 1,000 years."
And so Wanamaker – a former high school science teacher in Maine whose fascination with climate change sent him back to graduate school – works with students to carefully collect, process and study clam shells.
The research is painstaking – the shell increments are measured in millionths of a meter and microscopes are required at the most important steps. And the tools are sophisticated – two mass spectrometers measure shell fragments for different isotopes of carbon and oxygen. (Isotopes are elements with varying numbers of neutrons. Heavier isotopes of oxygen in the shell material generally correspond to colder ocean temperatures.)
"Isotopes are just wonderful tracers in nature," Wanamaker said, noting he also takes isotope measurements for research projects across campus and beyond.
When it comes to Wanamaker's own work with clam shells, "In the broadest sense, we're trying to add to our understanding of oceans over the last several thousand years," he said. "We have a terrestrial record – we can get an excellent chronology from tree rings and there is a climate signal there. But that's missing 70 percent of the planet."
Iowa State University: http://www.iastate.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Popular myth has long credited New York's soft water for the city's irresistibly crusty, chewy bagels. But the chemistry behind a superior bagel is more complicated.
A powerful earthquake in Italy killed hundreds of people—and set in motion a legal battle and scientific debate that has kept seismologists on edge
The Large Hadron Collider is smashing protons at the highest energy ever attempted - but they are only test collisions, as the LHC continues to gear up its second run.
Separate sections of one of New Zealand's biggest faults appear to have ruptured simultaneously in the past, suggesting a huge quake there is possible in the future
In a central London pub, a young bearded physicist is demonstrating how to build a model of the universe from plastic Lego bricks. Clue: you need a lot of them.
Kim Jong-un's nuclear ambitions aren't the only reason a nuke-free world is looking more like a pipe dream. All nuclear states are currently upgrading their arsenals
A new study shows many animals can make their own sunscreen, which could help humans down the line
The more scientists examine H2O, the stranger it starts to seem. Water bends all the rules – but if it didn’t, ice would sink and firefighters’ hoses would be useless
CERN’s huge particle accelerator is working its way toward full operation and a new phase of exploration. But it is not only the accelerator that has been upgraded – the particle detectors have some new tricks too
A magnitude 7.3 earthquake strikes eastern Nepal, two weeks after a devastating quake that killed more than 8,000 people.