2023 Marine Heat Waves
The year 2023 witnessed marine heat waves (MHWs) of unprecedented scale and intensity. Covering 96 per cent of the global ocean surface, these events lasted four times longer than historical averages. Scientists warn that such extreme ocean warming may indicate a climate tipping point. This could lead to irreversible damage to marine ecosystems and threaten global marine industries.
About Marine Heat Waves
Marine heat waves are prolonged periods of unusually high ocean temperatures. They occur in various ocean regions and have become more frequent and intense over recent decades. These events disrupt marine ecosystems, affect fisheries, and impact human livelihoods dependent on the sea.
2023 MHWs
In 2023, MHWs reached new extremes in intensity, duration, and geographic extent. The total marine heat wave activity amounted to 53.6 billion °C days square kilometre. This figure exceeds the historical norm by more than three standard deviations since 1982. MHWs lasted four times longer than the average duration recorded over the past 40 years.
Regional Hotspots and Drivers
The North Atlantic, Tropical Eastern Pacific, North Pacific, and Southwest Pacific accounted for 90 per cent of oceanic heating anomalies. The North Atlantic experienced the longest marine heat wave on record, lasting 525 days since mid-2022. The Southwest Pacific event broke records for size and duration. In the Tropical Eastern Pacific, temperature anomalies peaked at 1.63°C during the onset of El Niño. Drivers include increased solar radiation due to reduced cloud cover, weakened winds, and ocean current changes.
Ecological and Economic Impacts
MHWs cause coral bleaching, mass migration of marine species, and disruption of food webs. These effects reduce biodiversity and increase mortality rates. Key fisheries, such as the Pacific cod fishery, have declined due to species redistribution. Economic losses have been reported in fisheries and marine industries worldwide. Reduced seafood availability threatens food security and livelihoods in coastal communities.
Emerging Climate Tipping Points
Scientists warn that the intensity and persistence of MHWs may signal an approaching climate tipping point. This could trigger irreversible ecosystem collapse. Coral reefs are particularly vulnerable, with bleaching events pushing them beyond recovery thresholds. The loss of marine biodiversity would have far-reaching consequences for global ecology and human well-being.
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