Marine cold spells are cold versions of heat waves: periods of exceptionally cold water, able to hurt or help the ecosystems they hit. Today, the oceans experience just 25% of the number of cold spell days they did in the 1980s, and cold spells are about 15% less intense, researchers found. Weaker cold spells could mean they're less likely to cause mass die-off events, but having fewer cold spells also means refuges and recovery periods from marine heat waves are disappearing.
