Woods Hole Oceanographic Institution researchers recently used a Bahamas brain coral to reconstruct a 218-year-long temperature record showing the long-term behavior of the North Atlantic Oscillation (NAO), a large-scale atmospheric pressure variation. The scientists believe that the resulting knowledge of the past behavior of the NAO in response to global temperature changes can help predict the future impact of the NAO on weather and climate from the East Coast of the United States all the way to Western Europe. WHOI described the work of Goodkin and her colleagues in a recent statement.
In the past, scientists have had land-based records to correlate with the behavior of the NAO, but the reconstruction of a marine-based historical record, using the long-lived brain coral, is a first.
“By analyzing the coral, we were able to look at changes in the ocean relative to changes on land,” said Nathalie Goodkin, lead author of the study published in the December issue of the journal Nature Geoscience.
As they grow, corals accrete seasonal and annual growth layers, similar to tree rings. The proportions of trace elements versus the major element (calcium) found in the layers of the skeleton largely depend on the temperature of the seawater in which it was formed. By analyzing the strontium to calcium ratio in the Bermuda brain coral, Goodkin and colleagues — WHOI scientists Konrad Hughen, Scott Doney and William Curry — were able to reconstruct monthly changes in ocean temperatures and evaluate variability of the NAO during both cold and warm periods from the Little Ice Age (1800–1850) to modern day.
The research team found the variability of the NAO decade-to-decade (multi-decadal scale) has been larger, swinging more wildly, during the late twentieth century than in the early 1800s, suggesting that variability is linked to the mean temperature of the Northern Hemisphere. This confirms variability previously reported in past terrestrial reconstructions.
“When the Industrial Revolution begins and atmospheric temperature becomes warmer, the NAO takes on a much stronger pattern in longer-term behavior,” said Goodkin. “That was suspected before in the instrumental records, but this is the first time it has been documented in records from both the ocean and the atmosphere.”
You can read more about how the NAO works and how this research can help scientists understand its influence on stormy weather acrosss the Atlantic at the WHOI website.
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