2023 started with unprecedented marine heat waves instantly reshaping ocean conditions around the globe. Scientists and environmentalists are deeply alarmed by such intense heat waves. They are large, long-lived, and have recently accelerated dramatically. That shift came during a year of unprecedented marine heat waves, which blighted an astounding 96% of the global ocean surfaces. This figure is a steep increase from the long-term average of 73.7%, which has held from 1982 to 2022.
On average, these regional heat waves lasted 120 days. That’s four times longer than what we’ve seen on average in history! The North Atlantic Ocean, in particular, was affected this summer by a stunning marine heat wave. It lasted 525 days, sending average temperatures 3 degrees Celsius above normal levels. Such extreme conditions have underscored the urgent need for comprehensive studies to understand the implications of these changes on marine ecosystems and climate patterns.
Record-Breaking Durations and Extents
The marine heat waves of 2023 were historic, both in terms of duration and spatial extent. During these heat waves, the average duration was 120 days. This period is four times longer than what is typically observed in history, notifying us of a significant change in oceanic climate norms. The scale is just shocking. Temperatures increased across almost every single ocean surface, throwing many marine organisms and ecosystems out of whack.
The North Atlantic Ocean’s heat wave, which lasted an unprecedented 525 days, demonstrated just how serious this phenomenon can be. This event was the last straw, sending temperatures soaring to 3°C above normal. It acted as a troubling harbinger for what the future holds in climate cases. Scientists are now exploring how these prolonged heat waves can impact marine biodiversity, fish populations, and coastal communities that rely on these ecosystems for their livelihoods.
As of 2023, the anomaly in mean marine temperature was 1.3°C over baseline averages. This is a huge jump from past years wherein the annual mean temperature was only 0.98°C over normal. The long-term increase in ocean heat is having dire impacts on many marine species and risking even greater ecological disruptions.
Contributing Factors to Ocean Warming
A combination of climate change, El Niño and a warming Pacific Ocean led to the unprecedented ocean warming seen in 2023. The continuing Niño phase was a huge factor behind this reversal. It made the effect on warming of surface waters in the Tropical Eastern Pacific even worse. Together with weakening trade winds, this phase suppressed the upwelling of colder waters, amplifying temperature rises even more.
Conditions in the Southwest Pacific were key in driving this year’s heat waves. The reduction in cloud cover and subsequent increase in advection allowed heat to penetrate close to 1,000 meters deeper into the ocean. These alterations wreaked havoc on marine environments all over the nation. Their merger helped fuel the development of Cyclone Gabrielle, devastating much of New Zealand earlier this year.
Additionally, shifts in atmospheric circulation resulted in higher incoming shortwave radiation and lower latent heat loss from the North Pacific. These rapid alterations were instrumental in making possible the health waves that we have seen in this area. NOAA scientists are watching these developments in an effort to better understand how they are affecting such things as extreme weather patterns and climate resilience.
Implications for Global Climate
The repercussions of these prolonged marine heat waves are far-reaching, reaching past direct environmental impacts. This unprecedented rise in ocean temperatures is shifting global weather patterns and increasing the likelihood of extreme weather events. Coastal communities may face heightened risks from flooding and storms, while marine ecosystems struggle to adapt to rapidly changing conditions.
Extended heat waves across large regions are causing alarm. These increasingly acute conditions endanger the long-term sustainability of economic and ecological marine species and fisheries. The ongoing loss of biodiversity increases the risk of catastrophic threats to our food supply. It threatens the long-term economic health of communities that depend on fishing jobs.