The Northeast Pacific Ocean has experienced episodes of intense and persistent abnormally warm conditions, also known as marine heatwaves, that have devastating ecological and economic impacts. One notable marine heatwave, nicknamed The Blob, began in the Winter of 2013/2014. The Northeast Pacific experienced extreme sea surface temperatures (SSTs), first developing in the center of the Gulf of Alaska. These abnormally warm SSTs extended along the US West Coast. While the marine heatwave underwent substantial variation in its intensity and spatial pattern, the entire event lasted over 2 years, ending in mid-2016.This event caused ecological and economic disasters such as geographical shifts in marine species, massive die-offs of mammals and sea birds, unusual whale entanglements and mortality, and prolonged harmful algal blooms. Being able to predict these extreme events a few seasons in advance is very important, but has proven difficult.
“Marine heatwaves have been shown to have devastating ecological consequences, and some of their impacts could be mitigated if they were skillfully predicted. But this has proven challenging. While the intensity of these events is likely related to local atmospheric forcing, which is difficult to predict at lead times longer than 1-2 weeks, the likelihood for a marine heatwave to occur may be anticipated a few seasons in advance if we can relate these events to large-scale climate conditions,” says Antonietta Capotondi, a Physical Oceanographer for NOAA’s Physical Science Laboratory and lead author for this study.
In a new Geophysical Research Letters article, authors A. Capotondi, M. Newman, T. Xu, and E. Di Lorenzo use an empirical method to construct a model capturing how such climate conditions may change over time, and therefore whether a marine heatwave could be anticipated.
The study reveals that specific ocean surface conditions appear to lead to the development of the Northeast Pacific marine heatwaves 6–12 months later, which may offer a source of predictability. These conditions are related to a unique pattern of sea surface anomalies spanning the North Pacific and the central tropical Pacific, which also links extra-tropical marine heatwaves with subsequent tropical central Pacific warming.
“Our motivation was to identify these basin-wide conditions that are conducive to marine heatwave development in the Northeast Pacific, and we were indeed able to relate these events to a dynamical climate model that connects variability in the North Pacific with Central Pacific El Niño events in the tropics. These results open new areas of research on climate variations that can impact marine extremes, and provide a framework for assessing climate models’ fidelity in simulating those extremes,” says Capotondi.
Funding for this project was provided in part by the NOAA Climate Program Office, MAPP program.
Read the full study here.