Late one evening, after the traffic in the radiology lab at Falmouth Hospital has slowed, Mea Cook wheels some unusual patients into an empty X-ray room. Ten mud-filled PVC pipes -- sediment cores from the bottom of the Bering Sea -- lay stacked on Mea's cart. As radiologists in neighboring rooms peer inside human patients for signs of broken bones, Mea scans her cores one by one for different signs. Somewhere in the pale layers of sediment cut by bright slashes of ash, she hopes to find the secrets of 70,000 years of climate change.
In climatic terms, the earth is currently basking in a relatively warm and stable period. But jump back 20,000 years to the last ice age, and the climate data curve gets bumpy. During the ice age and the 40,000-year warm period that preceded it, earth endured a barrage of major climate shifts, including some sudden and drastic changes in the planet's average temperature.
Paleoclimatologists have deduced from marine sediments and from terrestrial ice cores that these climate changes were frequent and fast, but just how they occurred remains a mystery. In particular, they are intrigued by the role played by the Pacific Ocean, Earth's largest water mass. The view into the climate history of that vast ocean has been obscured by a scarcity of adequate sediments. Mea's X-rayed cores might provide an important glimpse.
The Core of the Matter
Getting to the core of the matter
Mea's cores, extracted from the floor of the Bering Sea by WHOI Senior Scientist Lloyd Keigwin and colleagues in June 2002, don't look particularly instructive. In fact, the 20-meter-long plugs of sediment on the refrigerated shelves of the McLean Laboratory's core warehouse look like something you might find in a construction ditch after a storm. But the mud-filled PVC and steel pipes are full of information.