Extreme ocean heating signals alarm for a 3°C warmer world

A new study from the University of Reading has brought to light the alarming risks associated with ocean heating, particularly highlighting the drastic changes observed in 2023. 

The research warns of the consequences if the world enters a climate that is 3.0°C warmer than pre-industrial levels.

Extreme ocean temperatures

The year 2023 witnessed record-high ocean temperatures that were unprecedented in the last four decades. The North Atlantic, in particular, experienced extreme warmth, measuring about 1.4°C above the average temperature between 1982 and 2011. 

This surge in ocean temperatures is not an isolated phenomenon but a potential precursor to what could become the new norm under a global warming scenario of 3°C. 

It’s crucial to note that the current global temperature has already risen by approximately 1.2°C above pre-industrial levels. The researchers set out to explore the causes behind the record-breaking ocean temperatures. 

Uncharted territory 

“The extraordinary heat in the North Atlantic and missing sea ice in the Southern Ocean in 2023 tell us the oceans are sounding an alarm,” said Dr. Till Kuhlbrodt, who led the study. 

“We urgently need to understand exactly why parts of the ocean are warming rapidly so we can prepare for more frequent weather disruption across the planet. How often we get hit by more of these extremes hangs on figuring out what’s driving the Atlantic and Southern Oceans into uncharted territory.”

Earth’s energy imbalance 

A critical aspect of this research is the investigation into Earth’s energy imbalance. Currently, the Earth is absorbing more solar energy than it releases back into space as heat, creating an imbalance of 1.9 watts per square meter. 

Over a year, this excess energy is roughly 300 times greater than the global annual consumption of electric energy. This imbalance, primarily driven by heat-trapping gases from human activities, is a significant factor in the acceleration of ocean heating, with over 90% of the excess energy being absorbed by the oceans.

Rapid warming of the Atlantic

Since 2016, the Atlantic Ocean has been warming at a rate faster than other ocean basins, particularly in the top 100 meters of the ocean. This trend is believed to be linked with record low levels of sea ice in the Southern Ocean. The year 2023 marked a historic low for Antarctic winter sea ice extent, the lowest since satellite monitoring began in the late 1970s.

The study emphasizes the need for a deeper understanding of how the rapid warming of the Atlantic is affecting sea ice cover and stresses the importance of attributing these oceanic and sea ice extremes accurately. Such understanding is crucial for refining climate models, which in turn will guide global mitigation policies and resilience measures.

Dr. Kuhlbrodt highlighted the urgency of gathering more data: “We need more data from the Atlantic to conclusively tie the warming and disappearing ice trends to a shift in the pattern of ocean currents, but the signals point to a hidden climate connections between the poles.”

Dangers of ocean heating 

Ocean warming, a consequence of climate change, has several significant and interrelated effects on the environment, marine life, and human societies.

Coral bleaching

Warmer ocean temperatures can lead to coral bleaching, where corals lose their vibrant colors and essential symbiotic algae. This can devastate coral reefs, crucial to marine biodiversity.

Sea level rise

Warmer temperatures cause the expansion of seawater and the melting of glaciers and ice caps, contributing to sea level rise. This can lead to coastal erosion, flooding, and displacement of coastal communities.

Changes in marine ecosystems

Ocean warming can alter the distribution of marine species, as many species migrate towards cooler waters. This disrupts existing ecosystems and affects fishing patterns and marine biodiversity.

Extreme weather events

Warmer oceans can fuel more intense and frequent hurricanes and typhoons, leading to increased risks for coastal communities.

Ocean acidification

Along with warming, the ocean absorbs more CO2, leading to acidification. This affects shellfish and other marine organisms with calcium carbonate shells or skeletons.

Impact on fisheries

Changing ocean temperatures can affect fish stocks, altering their breeding patterns, growth rates, and migration routes, impacting global fisheries and food security.

Disruption of nutrient cycles

Elevated temperatures can affect ocean currents, which in turn disrupt the upwelling of nutrients from the deep ocean. This can impact the base of the oceanic food web.

Threats to marine mammals

Marine mammals, like polar bears and seals, are affected by the loss of sea ice and changes in prey availability due to warming oceans.

These impacts highlight the importance of addressing climate change and implementing strategies to mitigate ocean heating.

The study is published in the Bulletin of the American Meteorological Society.

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