The world’s ocean are like planet-sized batteries. It absorbs a large amount of heat and then slowly releases it again. To date, due to increasing greenhouse gas emissions. The oceans are absorbing more than 90% of the heat stored in the Earth’s atmosphere. However, the recent rate of warming has been dramatic.

Since the end of March 2023, global sea surface temperatures have broken records every day. Making that day the hottest day ever recorded. Temperatures on 47 of those days exceeded previous record highs by the widest range since the satellite era. According to data from the European Union’s Copernicus Climate Change Service. (Read the BBC News Climate Science team’s data analysis for this article.) 

In February 2024, the world exceeded one year’s worth of surface temperature rise by 1.5°C. However, ocean temperatures in some areas last year were similar to what would be expected. If global warming caused overall surface temperatures to rise 3 degrees Celsius above pre-industrial levels, leading to predicted ocean warming. This suggests that it is progressing at a faster rate.

What is Causing the Record Warming of the Oceans?

Michael McFayden, an oceanographer with the National Oceanic and Atmospheric Administration (NOAA). Said two main factors were responsible for last year’s record ocean temperatures. First, the concentration of greenhouse gases in the atmosphere continues to increase.

Second, he said, was the massive El Niño event of 2023, in which the surface waters of the tropical Pacific Ocean were warmer than average, leading to increased evaporation and enormous heat transfer into the atmosphere.

Other, much weaker influences may also have played a role, McFayden says. In early 2022, the Pacific volcano Tonga Hunga Hunga Ha’apai erupted, releasing an “unprecedented” amount of water vapor that trapped heat in the atmosphere. In 2020, an International Maritime Organization directive also required commercial tankers to switch to lower sulfur fuel sources. This has reduced sulfur dioxide emissions from global shipping. Sulfur dioxide is a precursor to sulfates in the atmosphere and is responsible for the bright cloud trail behind the ship that reflects sunlight and heat back into space. A decrease in these bright trajectories could lead to a slight increase in global warming.

Hurricanes Ahead

One of the most notable effects involves precipitation and storm formation. As sea surface temperatures rise, more water evaporates, Fowler explained. Global warming also warms the atmosphere, and warm air can hold more moisture. So when it rains, it rains more. And the effects are even greater: For each degree of warming, precipitation and humidity could increase by an additional 7%, Fowler said.

The speed with which the storm intensified in 2023 also surprised meteorologists. For example, a “bomb cyclone” led to the rapid strengthening of a mid-latitude cyclone. Tropical-bound Hurricane Otis will hit Mexico’s Pacific coast in October 2023 after strengthening from a weak storm to a Category 5 hurricane overnight, similar to Hurricane Lee, which devastated the Caribbean the month before. Attacked Acapulco.

“We think this is the result of warmer ocean temperatures rapidly intensifying small storms into very large systems,” Fowler said. “But the jury is still out on the exact mechanism.

Of particular concern in 2024 is the possibility of more hurricane activity. The recent El Niño event may soon transition to a La Niña phase. La Niña promotes the development of intense and frequent storms in the North Atlantic off the coast of Africa by reducing wind shear. The resulting hurricane season is expected to be one of the most active on record, as sea surface temperatures are record high and more energy is transferred to storms that then pass overhead.  

Suffocating Oceans 

Even below the surface, the effects of global warming can be severe. From Australia to Tanzania, coral bleaching events are becoming more frequent and widespread, said Ana Queiroz, a marine and climate change ecologist at Britain’s Plymouth Marine Research Institute.

Unlike fish and other marine life, corals become immobilized when the ocean around them is exposed to heat waves, Queiroz explains. Many areas of the ocean are currently exposed to undersea heatwaves, and the effects can be “severe.

More generally,  warming oceans deprive marine life of vital oxygen and nutrients. Oxygen becomes less soluble in warmer oceans, and if the surface water warms before the ocean gets deeper, the density of oxygen decreases, making it difficult for the water above and below the ocean to mix. Without this mixing, nutrients deposited on or near the ocean floor have difficulty returning to surface waters, where they are needed by microorganisms such as phytoplankton that form the basis of food webs. Oxygen from surface water cannot reach the deeper layers of the ocean.

As a result, hypoxia (oxygen depletion) events occur more frequently on the ocean floor, leading to die-offs on the ocean floor, Queiroz said. The same is true for the expansion of “oxygen minimum zones,” where parts of the ocean floor are deprived of oxygen for long periods of time.

Sea Level Rise 

Even coasts cannot escape the effects of ocean warming. As ocean water warms and becomes less dense, it takes up more space and contributes to rising sea levels. Rising ocean temperatures are also melting sea ice in Antarctica and Greenland. Over the past 140 years, global sea levels have risen an estimated 21 to 24 centimeters.

Sea Levels Are Hot and Rising – William Sweet According to NOAA oceanographer William Sweet, sea levels will rise an average of 6 to 7 inches (15 to 18 centimeters) more by 2050. “Low-lying, densely populated areas are experiencing flooding more frequently than before, making the situation even worse,” he says.

In the Gulf of Mexico and along the U.S. East Coast, sea levels are rising even faster than average. “The rate of rise is currently outpacing all models. Sea levels are hot and rising,” Sweet said.

Amoc Slow Down?

Another tipping point risk associated with global warming is the slowing and eventual collapse of the ocean current system known as the Atlantic Meridional Overturning Circulation (Amoc).

The Amoc circulation system connects the South and North Atlantic Oceans and transports warm water from the tropics to the cooler north. During the journey, water evaporates, cools, and becomes salty. This cold, salty water becomes denser and eventually sinks to the ocean floor and returns south. Lucarini points out that slowing this circulation means less warm water can be pumped from mid- to high-latitude regions of the Atlantic Ocean. This leads to regional cooling effects in central-western Europe.

Lucarini said this system is related to how ocean warming changes precipitation and ice melting. Fresh rainwater does not sink as much as dense seawater. Increased precipitation in the North Atlantic and increased melting of Greenland’s ice mean less ice is sinking back south. As a result, Amoc will be weakened overall.

According to Lucarini, the weakening of the northward circulation of warm water means that, despite overall ocean warming, “cold spots” currently exist in certain regions of the North Atlantic. It is said that this helps explain the fact that But while there are signs that the current Amoc state is becoming unstable, it remains unclear how and how quickly it will change. A recent study by Lucarini et al. has shown that there may be several complex stages between the strength and weakness of blood flow.