Giant blobs along 5,000-mile-wide sargassum belt has killed animals, harmed human health and discouraged tourism

They identified atmospheric pressure changes over the Atlantic beginning around 2009 as the tipping point, with variations in circulation and wind patterns pushing more sargassum into the warmer waters of the tropics, where it grew through photosynthesis into the massive blooms that eventually ended up on the beaches of the Caribbean and the US Gulf coast.