A new scientific analysis shows that the marine heat waves (MHWs) that will hit the world in 2023 will be unprecedented in intensity, duration and scale. Researchers have identified regional factors behind these unusual events and linked them to broader changes in Earth's climate system. Their research also raises concerns that the planet may be heading towards a climate tipping point. MHW refers to a sustained period when ocean temperatures are well above normal.
Such events can cause serious harm to marine life, triggering widespread coral bleaching and mass mortality. They also disrupt fisheries and aquaculture, threatening economies. Experts generally agree that climate change due to human activities is causing a sharp increase in the frequency and severity of major tsunamis (MHWs).
In 2023, vast areas of the North Atlantic, tropical Pacific, South Pacific, and North Pacific were hit by extreme megastorms (MHWs). While their impact is clear, the precise reasons for the timing, duration, and intensity of these widespread events are not yet fully understood.
To investigate, the researchers conducted a detailed global study combining satellite data and ocean reanalysis data, including high-resolution information from the ECCO2 (Estimating Ocean Circulation and Climate Phase 2) project.
In a warming ocean, record-breaking marine heatwaves in 2023 highlight the growing vulnerability of ecosystems and human livelihoods. These events exacerbate fishery losses and reveal region-specific drivers, including enhanced shortwave radiation, ocean advection, and changes in upper ocean stratification. Together, these mechanisms illustrate the increasing impact of climate change on extreme heat events in the ocean.
The team found that the 2023 MHW exceeded all previous records in terms of intensity, duration and coverage. These events lasted four times longer than the historical average and affected 96% of the world's oceans. The most extreme warming occurs in the North Atlantic, tropical eastern Pacific, North Pacific, and Southwest Pacific, which together account for 90% of the total ocean thermal anomalies on record.
A notable example is the North Atlantic heat wave, which began in mid-2022 and lasted an unusual 525 days. In the Southwest Pacific, the affected area was larger and lasted longer than any previously observed event. In the tropical eastern Pacific, water temperatures rise by 1.63 degrees Celsius during the early stages of El Niño.
By applying mixed-layer heat budget analysis, the scientists identified several contributing factors that vary from region to region. These factors include more sunlight reaching the ocean due to fewer clouds, weaker winds and unusual changes in ocean currents. The researchers believe that the size and nature of the MHW in 2023 may reflect significant changes in the way the ocean interacts with the atmosphere, which could be an early signal that a climate tipping point is coming.
Compiled from /scitechdaily