A prolonged period of anomalously warm sea surface temperature in a specific ocean region.A marine heatwave is a period of unusually warm ocean water in a specific region, lasting from days to months. Unlike a single warm day, it's a sustained event that can disrupt marine ecosystems, shift fish populations, and affect weather patterns. These events are the ocean's equivalent of atmospheric heatwaves, but because water has a much higher heat capacity, they store and release enormous amounts of energy, making them significant for both marine life and coastal climates.
The term gained prominence in the early 2000s, but the phenomenon was recognized earlier; the 2011 Western Australia event and the 2013–2016 'Blob' in the Northeast Pacific brought it to wide scientific and public attention.
Marine heatwaves typically form when persistent high-pressure weather systems reduce cloud cover and wind, allowing more sunlight to heat the ocean surface and limiting mixing with cooler, deeper water. They can also be driven by ocean currents that advect warm water into a region. The event is defined statistically: when sea surface temperatures exceed a local threshold (often the 90th percentile) for at least five consecutive days, it qualifies as a marine heatwave.
Marine heatwave forecasts help fisheries managers, aquaculture operators, and conservation agencies prepare for ecosystem stress, such as coral bleaching or shifts in commercial fish stocks.
The 2013–2016 Northeast Pacific marine heatwave, nicknamed 'The Blob,' covered an area roughly the size of the continental United States and persisted for over two years.



















