September 26, 2025 — In 2013, scientists noticed a block of unusually warm water detected in the Pacific Ocean between the Gulf of Alaska and the Coast of Southern California. This was recognized by meteorologists as a basin-scale marine heatwave (MHW), often referred to as “the blob”. This water mass hung around from 2013-2016 before re-emerging again in July of 2019 (known as Blob 2.0) and lasting 20 months.
In May 2025, the blob reappeared.
Rachel Hager, a spokesperson for NOAA Fisheries, said this new MHW has grown “approximately the same size as the contiguous U.S.” She added it now ranks among the top three largest MHWs ever recorded in the northeast Pacific Ocean since monitoring began in 1982.