It was late 2013 when those keeping an eye on the North Pacific Ocean first realised that something strange was happening within its waters. From the coast of Alaska all the way down to Baja California, a marine heatwave was swelling, impacting the marine life and fisheries of the region for years to come.
Researchers found that many marine animals responded to the warmer waters by extending their range northward. Creatures typically only seen in warmer Mexican waters, including jellyfish, crabs, nudibranchs, fish, as well as larger animals such as dolphins and sea turtles, were found on, or off, beaches in California.
Nicknamed the 'Blob’ by University of Washington climatologist Nick Bond – a name that fast caught on – the phenomenon saw sea temperatures in some places rise seven degrees Fahrenheit higher than average, with some patches of ocean hotter than ever recorded. At its peak, the warm water covered about 3.5 million square miles, an area larger than the United States.
The Summer of 2019 also saw a renewed marine heatwave off the US west coast. Dubbed Blob 2.0, the wave of heat saw waters reach 4.5F (2.5C) higher than normal. New research released this week suggests that lighter winds, in turn caused by the weakest North Pacific atmospheric circulation patterns in at least the last 40 years, spurred the event. Less wind blowing over the ocean’s surface means there’s less evaporation and less cooling. The researchers explain the process as being similar to wind cooling off human skin by evaporating sweat. ‘In 2019, it was as if the ocean was stuck outside on a hot summer day with no wind to cool it down,’ reads the text accompanying the study.
Oceanologists and climatologists are now warning that we should expect to see more ‘blobs’ in the future as global warming progresses. ‘It’s the same argument that can be made for heat waves on land,’ said Dillon Amaya, a postdoctoral visiting fellow at the Cooperative Institute for Research in Environmental Sciences. ‘Global warming shifts the entire range of possibilities towards warmer events. The Blob 2.0 is just the beginning. In fact, events like this may not even be considered “extreme” in the future.’
In another study, also released this week, researchers combined the latest climate, ocean and fish modelling approaches to try and quantify the future impacts of marine heatwaves like the Blob on fish stocks along the west coast of Canada and the USA. The resulting models reveal that future blobs would exacerbate existing climate change impacts, causing fisheries to decrease in biomass and generating shifts in their distribution.
‘Previous studies have largely under-estimated climate change impacts on our marine life as they focused on changes in the average conditions,’ said William Cheung, a professor at the UBC Institute for the Oceans and Fisheries. ‘The actual impacts in the next few decades are likely to be doubled when marine heatwaves occur. For example, in the year when a marine heatwave occurs, the average biomass of sockeye salmon in the ocean off Alaska and British Columbia is projected to reduce by more than 10 per cent. This is in addition to a biomass decrease of 10-20 per cent that is expected under long-term climate change.’
While each blob may be caused by the unique combination of climatic factors at the time, it is greenhouse gas emissions and global heating that drives ocean warming as a whole and therefore makes such events more damaging. ‘Our results underscore the need for a reduction of anthropogenic greenhouse gas emissions – the fundamental driver of ocean warming, to limit challenges from marine heatwaves on fish stocks and fisheries,’ said Thomas Frölicher, co-author of the recent study.