Millions of dead jellyfish are washing up around the world. 'The blob' could be to blame.

Like a tourist on a cruise ship, the by-the-wind sailor jellyfish (Velella velella) spends its days drifting aimlessly through the open sea, gorging itself on an endless buffet of complementary morsels.

The jelly straddles the ocean's surface with a rigid sail poking just above the water and an array of purple tentacles dangling just underneath. As the sail catches wind, the jelly floats from place to place, capturing tiny fish and plankton wherever it roams. Thriving Velella colonies can include millions of individuals, all just partying and chowing down together in the open water. Life is good.

Until, that is, the wind blows a colony of sailor jellies onto shore.

Every year, on beaches around the world, colonies of sailor jellies become stranded by the thousands. There, they dry up and die, becoming a "crunchy carPet" of dehydrated corpses covering the sand, Julia Parrish, a University of Washington professor and co-author of a new study on mass Velella strandings, said in a statement.

Related: Image gallery: Jellyfish rule!

Sailor jelly strandings are common when seasonal winds change course, but some — like a 2006 event on the west coast of New Zealand — are on another level entirely, with the jellyfish corpses numbering not in the thousands, but in the millions. Why? What force of nature makes some Velella strandings so much larger than others? 

Parrish and her colleagues wanted to find out. So, in their new study (published March 18 in the journal Marine Ecology Progress Series) they delved into 20 years of Velella observations reported along the west coast of the United States.