At the end of the last ice age, about 18,000 years ago, the Atlantic overturning circulation weakened significantly for several thousand years. Researchers from Bremen and Brazil have now analyzed a high-temporal-resolution sediment core that allows for a more precise reconstruction of this so-called Heinrich event at a temporal resolution of centuries. The study, published in Nature Communications, shows that during this prolonged period of weakness, short-term intensifications of the circulation lasting several centuries occurred.

People rarely think about culverts until they are gone. These plain pipes and boxes carry roads over streams and span less than 20 feet -- the federal cutoff for what counts as a bridge. That means road-stream crossings stay out of the National Bridge Inventory and therefore, off the inspection schedule. Yet, when Tropical Storm Irene tore through New England in 2011, it destroyed more than 960 of them in Vermont's Green Mountains alone and left 13 communities entirely cut off for days.