Updated: Aug 6, 2021
What are marine heatwaves?
Heatwaves are characterized by short periods of abnormally high temperatures and just as we experience them on land, heatwaves also occur in the oceans. Marine heatwaves can happen during the summer or winter and actually have a variety of possible causes.
One of the most common causes are ocean currents. Ocean currents build up warm waters in certain regions and as the currents travel, they spread these warm water regions to other areas. Another cause is air-sea heat flux, which is when the ocean's surface becomes warmer as a result of warmer temperatures in the atmosphere.
It is estimated that the ocean has absorbed nearly 90% of the heat trapped by greenhouse gases, since midcentury. Furthermore, as the use of fossil fuels is continued, weather conditions become increasingly more extreme in the future and marine heatwaves will only become more prevalent.
What are its impacts?
Just has atmospheric heatwaves can lead to many negative effects on humans, like stroke and dehydration, marine heatwaves have devastating effects on the ocean's biodiversity.
In early July of 2021, extraordinary heat and drought hit the Western United States and Canada, and "killed hundreds of millions of marine animals and continues to threaten untold species in freshwater, according to a preliminary estimate and interviews with scientists."
There are many implications to the mass loss of populations of marine species like these mussels (left). Firstly, mussels are vital to aquatic ecosystems because they regulate their habitats and make it suitable for other species. Furthermore, they are important prey for sea ducks, which feed on mussels during their migration to summer breeding regions. Thus, it is evident that aquatic food chains and habitats are heavily disrupted.
What is important to note is that species like mussels, which live in intertidal zones are generally more resilient to fluctuations in temperature. However, the more frequent the heatwaves are, the less time they have to recuperate; as aforementioned, it is likely that the duration, frequency, and effects of marine heatwaves will worsen.
Marine heatwaves also cause great economic losses in fisheries, aquaculture, and ecotourism industries.
What can we do?
"By raising general awareness of these phenomena, and by improving our scientific understanding of their physical properties and ecological impacts, we can better predict future conditions and protect vulnerable marine habitats and resources."