In the past few years, ocean scientists have been excited by the appearance of an entirely new subdiscipline: the study of marine heatwaves (MHWs), discrete periods of unusually warm temperatures in the ocean. Several such events have captured the attention of both scientists and the public, most notably an MHW known as the Blob1 that occurred in the northeastern Pacific Ocean during 2013–15. High-profile impacts22 of MHWs include the closure of fisheries, large-scale die-offs of seabirds and unusual sightings of species thousands of kilometres out of their natural range (Fig. 1). Such effects make these heating events one of the most visible signs of an ocean under stress. Writing in Nature, Jacox et al.3 report a metric that puts MHWs into their spatial context with surrounding cooler waters, and thereby casts light on the distance by which ocean organisms might be displaced.

Progress in science is typically incremental: research papers usually ‘stand on the shoulders of giants’ that have preceded them. For scientists studying MHWs, however, there are no giants’ shoulders to stand on. The field is therefore inventing itself from scratch, creating a dynamism and excitement that is as rare as it is fascinating to follow.
— Read on www.nature.com/articles/d41586-020-02172-0