Environment & Energy

"Varying oxygen isotopes show changes in seawater linked to temperature and the influence of different water masses, which helps show the changes in ocean circulation, she said. The width of the growth rings tells scientists about temperature, the supply of food to the seabed and circulation dynamics that bring nutrients, she added. The changes in the rings are clear once a tipping point has been crossed, she said, explaining that during a transition to a colder climate period in the Northern Hemisphere a few hundred years ago, the shift of oxygen isotope values reflected colder conditions and a stronger influence of Arctic waters. And the growth bands became narrower, indicating both lower temperatures and reduced food availability."

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