“The Blob” is the nickname for a massive marine heatwave that dominated the North Pacific Ocean from 2013 to 2016, pushing sea surface temperatures as much as 7°F above average across a stretch of water from Alaska to Mexico. It killed marine life on a staggering scale, triggered toxic algal blooms, and shut down fisheries along the entire West Coast. The term has also been used more loosely to describe other ocean phenomena, including a continent-spanning belt of seaweed in the Atlantic and strange gelatinous creatures spotted in deep water.
How the Blob Formed
In the fall of 2013, an unusually strong ridge of high atmospheric pressure parked itself over the northeastern Pacific and refused to move. Meteorologists called it the “Ridiculously Resilient Ridge” because it persisted for months, far longer than typical weather patterns. That ridge suppressed the winter winds that normally churn the ocean surface and pull cold, nutrient-rich water up from the deep, a process called upwelling.
Without that wind-driven mixing, the sun heated the surface water with nothing to cool it back down. A massive lens of warm water formed and kept expanding. By the summer of 2014, it stretched from the Gulf of Alaska to Baja California. The atmospheric ridge finally weakened in 2015, but the warm water lingered into early 2016, and NOAA noted that conditions in the northeast Pacific never entirely returned to normal.
What the Blob Did to Marine Life
The effects cascaded through the food web from the bottom up. Warmer water favored smaller, less nutritious species of zooplankton (the tiny animals that form the base of ocean food chains) over the large, fat-rich species that salmon, seabirds, and forage fish depend on. Warm-water copepods that normally belong hundreds of miles south in the California Current system appeared earlier in the season and stuck around longer. Subtropical species like ocean sunfish and skipjack tuna showed up in Alaskan waters where they had rarely, if ever, been seen.
The consequences for larger animals were devastating. Sea lion pups stranded along the California coast in record numbers, likely because their mothers couldn’t find enough prey close to shore. Massive seabird die-offs occurred in the Gulf of Alaska. Forage fish populations declined sharply, and commonly fished species across the region took heavy losses.
Toxic Algal Blooms
The warm, nutrient-altered water also fueled a massive bloom of toxic algae along the entire West Coast in 2015 and 2016. These algae produce a neurotoxin called domoic acid, which accumulates in shellfish and can cause serious neurological damage in humans. The last confirmed outbreak of human poisoning from this toxin occurred in eastern Canada in 1987, and the reason it hasn’t happened since is active monitoring programs, not the absence of dangerous blooms. The Blob-linked bloom was one of the largest ever recorded and led to prolonged closures of crab, clam, and other shellfish fisheries from Washington to California.
Is the Blob Coming Back?
Marine heatwaves like the Blob are not one-time events. Several have occurred since 2016, including significant heatwaves in the Gulf of Alaska and Bering Sea in 2016 and the California Current in the same year. Scientific consensus is building that human-driven climate change has significantly increased the likelihood of each of these events.
Climate projections paint a concerning picture. Under a high-emissions scenario, marine heatwave intensity is expected to exceed the normal range of natural variability globally by 2033. Parts of the tropical Atlantic and Pacific may enter what researchers describe as a “permanent marine heatwave state,” where historically abnormal temperatures become the new baseline, as early as the 2020s to 2040s. Under a scenario with strong greenhouse gas reductions, these timelines stretch out, but marine heatwave days still increase nearly everywhere by mid-century.
The Other “Blob”: Atlantic Sargassum
If you’ve seen headlines about a blob of seaweed heading toward beaches, that’s a different phenomenon. The Great Atlantic Sargassum Belt is a massive floating aggregation of brown seaweed that first appeared in an unusual pattern in 2011 in the tropical Atlantic, outside the seaweed’s traditional home in the Sargasso Sea. It has recurred most years since, growing larger over time.
By 2018, the belt stretched over 5,500 miles from the coast of West Africa to the Caribbean and Gulf of Mexico, with an estimated biomass of more than 20 million tons. In 2022, it was even larger at 22 million tons. When this seaweed washes ashore in large quantities, it creates serious problems: bays in the Caribbean have been filled with tens to hundreds of thousands of metric tons in a matter of hours, smothering beaches from French Guiana to Florida. The rotting seaweed releases hydrogen sulfide gas, which smells like rotten eggs and can cause respiratory irritation. There is currently no reliable way to predict how large or frequent these events will become.
Mysterious Blobs in the Deep Sea
Some people searching for “the blob in the ocean” may be thinking of the strange, gelatinous creatures that occasionally go viral after being captured on deep-sea cameras. The ocean is full of soft-bodied animals that look genuinely alien.
Pyrosomes, sometimes called “sea pickles,” are hollow, tube-shaped colonies of tiny organisms that can grow several feet long and drift through open water in enormous blooms. They’re translucent, bioluminescent, and surprisingly carbon-rich, making them an important food source when they wash onto shallow reefs. Blooms have been documented from the Pacific Northwest to Timor-Leste, with densities reaching 1,500 individuals per square meter in some areas.
Then there are the truly deep discoveries. NOAA Ocean Exploration has documented ghost-like creatures at extreme depths, including a never-before-seen octopod spotted at 14,075 feet near Hawaii in 2016 that social media dubbed “Casper” for its pale, translucent body. In 2015, an unfamiliar species of comb jelly was observed nearly 13,000 feet deep off Puerto Rico and was later formally described as a new species. Deep-sea jellyfish like Deepstaria, which resemble undulating trash bags, have also startled viewers when footage surfaces online. These animals are reminders that vast portions of the ocean remain unexplored, and what lives down there can look very much like a blob.