NOAA – “Thermal displacement” reflects how far species must go to follow preferred temperatures. Marine heat waves across the world’s oceans can displace habitat for sea turtles, whales, and other marine life by 10s to thousands of kilometers. They dramatically shift these animals’ preferred temperatures in a fraction of the time that climate change is expected to do the same, new research shows. To measure that temporary dislocation of ocean surface temperatures, which can in turn drive ecological changes, NOAA scientists have now introduced a new metric called “thermal displacement.” A research paper describing the changes and the means of measuring them was published in the journal Nature this week. Research scientist Michael Jacox of NOAA Fisheries’ Southwest Fisheries Science Center called it a powerful new way of looking at marine heatwaves. “When the environment changes, many species move,” Jacox said. “This research helps us understand and measure the degree of change they may be responding to.” Scientists have typically characterized marine heatwaves based on how much they increase sea surface temperatures, and for how long. Such local warming particularly affects stationary organisms such as corals. In contrast, thermal displacement measures how far mobile species must move to track ocean surface temperatures. The extent of thermal displacement caused by marine heatwaves may not necessarily correspond to their intensity. Thermal displacement depends on the sea surface temperature gradient, the rate at which temperature changes across the ocean. If a heatwave warms an area of ocean, fish, turtles, whales, and other species may have to travel great distances if the temperature gradient is weak, but not if the gradient is strong. “It may give us an idea how the ecosystem may change in the future,” said Michael Alexander, research meteorologist at NOAA’s Physical Sciences Laboratory and a coauthor of the new research. The changes may have implications for coastal communities if commercial fish species shift. Fishermen would have to travel hundreds of miles farther to reach them, he said…”