The Silence of the Clams

When it comes to asking why, exactly, something spelled g-e-o-d-u-c-k is pronounced "gooey duck," these test subjects simply clam up. But these bivalves have plenty to tell us on the matter of reconstructing past climactic conditions.

The spacing and sizing of concentric ridges that form on the geoduck's shell as it grows vary according to changes in year-to-year temperature much like tree rings. In fact, climate researchers are cross-referencing records captured in geoduck shells with tree ring records to better refine their understanding of climatic variations in the Pacific Northwest.

This matching of growth rings between clam and tree is no mere fun curiosity, but points a way toward improving our understanding of global climate change and constructing better models that predict future change.

Our record of climate goes back about one thousand years thanks to atmospheric clues left in ice cores. These, however, typically provide insight into global average conditions and tell little to nothing about the local variabilities that occurred around the world that may be masked by changing overall global averages.

By its own admission, the exceedingly complex climate models constructed by the Intergovernmental Panel on Climate Change (IPCC) are founded on best-available information and include gaps in the historical record.

But this multispecies cross-referencing technique will allow the construction of more detailed local climatic records than those currently available. As a result, improved modeling and prediction of future conditions will follow.

Bryan Black of Oregon State University and his team present their findings in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, and he explains the significance to Scientific American:

"Geoducks and trees each capture climate variability from their own unique perspective. We can take those different perspectives — each explaining a different part of the story — and put them together to get a full view of what the climate was like in the past, and a more robust forecast for the future."

And while the team at work in the northwest sets their sights to gathering even older shells for analysis to improve climate record refinement further back in time, they also underscore the potential for researchers in other parts of the world to use the same approach based on locally available flora and fauna.

Photo courtesy of Caterina, via Flickr