Centuries-Long Climate Record Reconstructed from Coral

Scientists at the Woods Hole Oceanographic Institution have reconstructed a 218-year temperature record of the North Atlantic by analyzing brain coral.

A wide-ranging pressure phenomenon known as the North Atlantic Oscillation (NAO) affects the climate of North America, Europe and North Africa as well as the ocean between. Precise NAO data has always been difficult to obtain, as land-based measurements do not always capture its greater oceanic behavior. However, corals are slow-growing and have long life spans, and contain annual growth layers much like rings in a tree that depend upon seawater temperature. By sampling these oceanic corals, a month-by-month record of the NAO was recalculated for the previous 218 years.

Knowledge of the NAO has an impact on industries such as shipping, fishing, coastal management and hydroelectric power generation. The researchers did confirm that the variability of the NAO decade-to-decade during the late twentieth century was larger and with greater swings of temperature than previous centuries, suggesting that human industrialization is impacting the stability of the NAO.

Whether the NAO swings positive (warmer) or negative (cooler) over the decades has not been affected by human activity. Instead, the variability within those periods has increased, leading to stronger storms during positive cycles and weaker weather during negative cycles.

These results were published in the December issue of Nature Geoscience.

Photo: ScienceDaily