Geophys. Res. Lett. 35, L01502 (2008)

Credit: GIFFORD H. MILLER

The melting of ancient ice caps on Baffin Island in the Canadian Arctic, one of the North American regions most sensitive to climate change, shows that the twentieth century was the island's warmest since AD 350. Vegetation that died when first covered by ice is now emerging, as are undisturbed rock surfaces.

Gifford Miller of the University of Colorado and colleagues used carbon-14 to date both the vegetation and, in a novel approach, the quartz-rich rock, from which they reconstructed changes in Baffin's ice caps. As cosmic rays hit quartz, they produce carbon-14, but production is greatly reduced or eliminated under ice. By studying quartz at the melting edge of several ice caps, the researchers determined that the last ice age ended on Baffin 6,000 years ago and that local ice caps began re-forming 2,800 years ago.

Carbon-14 in emerging vegetation revealed that some of the ice caps remained intact from AD 350 through the Medieval Warm Period (around 800 to 1300) and beyond, but have shrunk by more than 50 percent since 1958. The researchers conclude that the last century was the warmest on Baffin for at least the past 1,600 years.