Ocean temperatures surge unprecedentedly with several potential factors

Recently, a graph showing a single red line that charts sea surface temperatures in the North Atlantic Ocean went viral due to its startling display of unprecedented warming. The warming is nearly 2 degrees (1.09 Celsius) above the mean dating back to 1982, the earliest year with comparable data. Researchers are concerned about the huge surge in temperature which is occurring alongside other climate woes including record-shattering wildfires in Canada, rapidly declining sea ice in Antarctica and unusually warm temperatures in many parts of the world.

Eliot Jacobson, a retired mathematics professor, created the graph using data from the National Oceanic and Atmospheric Administration. The ocean temperatures are so anomalously high that he had to “increase the upper bound on the y-axis.” Jacobson said, “I’ve been doing this for a long time, but this one was like, ‘Oh my God, look at this,’ What is going on here?”.

There are several factors that may be contributing to the off-the-charts warming, which is occurring alongside other climate woes including record-shattering wildfires in Canada, rapidly declining sea ice in Antarctica, and unusually warm temperatures in many parts of the world, not including Southern California. Daniel Swain, a climate scientist at UCLA, said underlying everything is human-caused climate change. However, atop that are a handful of other potential factors, including the early arrival of El Niño, the recent eruption of the Hunga Tonga volcano, new regulations around sulfur aerosol emissions, or even a dearth of Saharan dust.

The North Atlantic is experiencing record-shatteringly warm temperatures right now. Gregory Johnson, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory, said nearly all of the Atlantic basin is experiencing anomalous warmth, including the Irminger Sea southeast of Greenland, the western Mediterranean Sea, and the tropics “all the way from Africa to at least the Caribbean.” He also said, “We are definitely in record territory.” Furthermore, global sea surface temperatures are also climbing to new highs, NOAA data show.

Warming events in the ocean can have considerable consequences, including triggering algal blooms, bleaching coral, and negatively affecting fisheries and other ecosystems, Johnson said. Marine heat waves can also provide more energy for tropical cyclones and more moisture for atmospheric rivers and flooding events. A warmer ocean tends to expand, which can lead to sea level rise, along with melting ice sheets.

The recent arrival of El Niño, a climate pattern in the tropical Pacific and a major driver of weather patterns across the world, could be partially to blame, Johnson and others said. While its counterpart, La Niña, brought cooler water to the ocean’s surface, El Niño is generally linked to warmer global temperatures and often results in warmer oceans. The NOAA recently said there is an 84% chance that the developing El Niño will be of moderate strength, and a 56% chance it will become a strong event at its peak later this year.

Meanwhile, the World Meteorological Organization predicts that at least one of the next five years—and the five-year period as a whole—will be the Earth’s warmest on record due to global warming and El Niño. But El Niño doesn’t entirely explain the sudden escalation in ocean temperatures. Another potential factor may be the recent eruption of an undersea volcano in Tonga, said Swain.

The volcano, Hunga Tonga-Hunga Ha’apai, erupted beneath the ocean in January 2022 and shot record-breaking amounts of water vapor all the way up to the stratosphere. And because water vapor acts as a heat-trapping greenhouse gas, researchers said the eruption could result in more planetary warming.

A major change in regulations around the sulfur content of shipping fuels could also be behind the warming spike, according to both Swain and Jacobson. The regulations, ordered by the International Maritime Organization in 2020, reduced the upper limit of sulfur in fuels from 3.5% to 0.5% in an effort to achieve cleaner air in ports and coastal areas.

However, the change may have had an unexpected consequence because sulfate aerosols can reflect sunlight away from the earth, “effectively dimming the planet’s surface,” Jacobson wrote in a post on his website. “By cleaning up shipping fuels, massive regions of the world’s oceans that were protected from heating by shipping sulfate aerosols are now experiencing rapid warming,” he said, including many of the main shipping routes where the warming is happening.

Michael Mann, a professor of earth and environmental science at the University of Pennsylvania, said while sulfate aerosols can influence the North Atlantic, he did not believe that the recent regulatory change is behind the current temperature spike. Instead, he said, a lack of Saharan dust—possibly linked to weakened trade winds from the burgeoning El Niño—could be impacting temperatures on short timescales. The dust normally has a cooling impact on the area, and the lack of dust “probably does help to explain the observed anomaly.”

The conditions aren’t “completely out of left field” based on global warming trends. “The long-term trend is not going to stop, and we are stair-stepping up our way to much warmer oceans and a much warmer climate, and there still hasn’t been a great deal of momentum away from that,” Swain said. “We’re still moving in a pretty alarming direction, overall, when it comes to warming.”