Recent Marine Heat Waves Caused by Undersea Volcanic Eruptions, Not Human CO2

In a previous post, I showed how submarine volcanic eruptions don’t contribute to global warming, despite the release of enormous amounts of explosive energy. But they do contribute to regional climate change in the oceans, such as marine heat waves and shrinkage of polar sea ice, explained a retired geologist in a recent lecture.

Wyss Yim, who holds positions at several universities in Hong Kong, says that undersea volcanic eruptions – rather than CO₂ – are an important driver of regional climate variability. The release of geothermal heat from these eruptions can explain oceanic heat waves, polar sea-ice changes and stronger-than-normal cycles of ENSO (the El Niño – Southern Oscillation), which causes temperature fluctuations and other climatic effects in the Pacific.

Submarine eruptions can eject basaltic lava at temperatures as high as 1,200 degrees Celsius (2,200 degrees Fahrenheit), often from multiple vents over a large area. Even though the hot lava is quickly quenched by the surrounding seawater, the heat absorbed by the ocean can have local, regional impacts that last for years.

The Pacific Ocean in particular is a major source of active terrestrial and submarine volcanoes, especially around the Ring of Fire bounding the Pacific tectonic plate, as illustrated in the figure below. Yim has identified eight underwater eruptions in the Pacific from 2011 to 2022 that had long-lasting effects on the climate, six of which emanated from the Ring of Fire.

One of these eruptions was from the Nishino-shima volcano south of Tokyo, which underwent a massive blow-out, initially undersea, that persisted from March 2013 to August 2015. Yim says the event was the principal cause of the so-called North Pacific Blob, a massive pool of warm seawater that formed in the northeast Pacific from 2013 to 2015, extending all the way from Alaska to the Baja Peninsula in Mexico and up to 400 meters (1,300 feet) deep. Climate scientists at the time, however, attributed the Blob to global warming.

The Nishino-shima eruption, together with other submarine eruptions in the Pacific during 2014 and 2015, was a major factor in prolonging and strengthening the massive 2014-2017 El Niño. A map depicting sea surface temperatures in January 2014, at the onset of El Niño and almost a year after the emergence of the Blob, is shown in the next figure. At that time, surface temperatures across the Blob were about 2.5 degrees Celsius (4.5 degrees Fahrenheit) above normal.

By mid-2014, the Blob covered an area approximately 1,600 km (1,000 miles) square. Its vast extent, states Yim, contributed to the gradual decline of Arctic sea ice between 2014 and 2016, especially in the vicinity of the Bering Strait. The Blob also led to two successive years without winter along the northeast Pacific coast.

Biodiversity in the region suffered too, with sustained toxic algal blooms. Yet none of this was caused by climate change.

The 2014-2017 El Niño was further exacerbated by the eruption from May to June 2015 of the Wolf volcano on the Galapagos Islands in the eastern Pacific. Although the Wolf volcano is on land, its lava flows entered the ocean. The figure below shows the location of the Wolf eruption, along with submarine eruptions of both the Axial Seamount close to the Blob and the Hunga volcano in Tonga in the South Pacific.

According to Yim, the most significant drivers of the global climate are changes in the earth’s orbit and the sun, followed by geothermal heat, and – only in third place – human-induced changes such as increased greenhouse gases. Geothermal heat from submarine volcanic eruptions causes not only marine heat waves and contraction of polar sea ice, but also local changes in ocean currents, sea levels and surface winds.

Detailed measurements of oceanic variables such as temperature, pressure, salinity and chemistry are made today by the worldwide network of 3,900 Argo profiling floats. The floats are battery-powered robotic buoys that patrol the oceans, sinking 1-2 km (0.6-1.2 miles) deep once every 10 days and then bobbing up to the surface, recording the properties of the water as they ascend. When the floats eventually reach the surface, the data is transmitted to a satellite.

Yim says his studies show that the role played by submarine volcanoes in governing the planet’s climate has been underrated. Eruptions of any of the several thousand active underwater volcanoes can have substantial regional effects on climate, as just discussed.

He suggests that the influence of volcanic eruptions on atmospheric and oceanic circulation should be included in climate models. The only volcanic effect in current models is the atmospheric cooling produced by eruption plumes.

Next: Climate Heresy: To Avoid Extinction We Need More, Not Less CO2

Ample Evidence Debunks Gloomy Prognosis for World’s Coral Reefs

According to a just-published research paper, dangers to the world’s coral reefs due to climate change and other stressors have been underestimated and by 2035, the average reef will face environmental conditions unsuitable for survival. This is scientific nonsense, however, as there is an abundance of recent evidence that corals are much more resilient than previously thought and recover quickly from stressful events.

The paper, by a trio of environmental scientists at the University of Hawai‘i, attempts to estimate the year after which various anthropogenic (human-caused) disturbances acting simultaneously will make it impossible for coral reefs to adapt and survive. The disturbances examined are marine heat waves, ocean acidification, storms, land use changes, and pressures from population density such as overfishing, farming runoff and coastal development.

Of these disturbances, the two expected to have the greatest future effect on coral reefs are marine heat waves and ocean acidification, supposedly exacerbated by rising greenhouse gas emissions. The figure to the left shows the scientists’ projected dates of environmental unsuitability for continued existence of the world’s coral reefs, assuming an intermediate CO2 emissions scenario (SSP2). The yellow curve is for marine heat waves, the green curve for ocean acidification.

You can see that the projected unsuitability rises to an incredible 75% by the end of the century for both perturbations, and even surpasses 50% for marine heat waves by 2050. The red arrow indicates the time difference at 75% unsuitability between heat waves considered alone and all disturbances combined (solid black curve).

But these gloomy prognostications are refuted by several recent field studies, two of which I discussed in an earlier blog post. The latest paper, published in May this year, reports on a 10-year study of coral-reef stability on Palmyra Atoll in the remote central Pacific Ocean. The scuba-diving researchers, from California’s Scripps Institution of Oceanography and Saudi Arabia’s King Abdullah University, discovered – by analyzing more than 1,500 digital images – that Palmyra reefs made a remarkable recovery from two major bleaching events in 2009 and 2015.

Bleaching occurs when the multitude of polyps that constitute a coral eject the microscopic algae that normally live inside the polyps and give coral its striking colors. Hotter than normal seawater causes the algae to poison the coral that then expels them, turning the polyps white. The bleaching events studied by the Palmyra researchers were a result of prolonged El Niños in the Pacific.

However, the researchers found that, at all eight Palmyra sites investigated, the corals returned to pre-bleaching levels within two years. This was true for corals on both a wave-exposed fore reef and a sheltered reef terrace. Stated Jennifer Smith, one of the paper’s coauthors,  “During the warming event of 2015, we saw that up to 90% of the corals on Palmyra bleached but in the year following we saw less than 10% mortality.”

The rapid coral recovery can be seen in the figure on the left below, showing the percentage of coral cover from 2009 to 2019 at all sites combined; FR denotes fore reef, RT reef terrace, and the dashed vertical lines indicate the 2009 and 2015 bleaching events. It’s clear there was only a small change in the reef’s coral and algae populations after a decade, despite the violent disruption of two bleaching episodes. A typical healthy reefscape is shown on the right.

Another 2022 study, discussed in my earlier post, came to much the same conclusions for a massive reef of giant rose-shaped corals hidden off the coast of Tahiti, the largest island in French Polynesia in the South Pacific. The giant corals measure more than 2 meters (6.5 feet) in diameter. Again, the reef survived a mass 2019 bleaching event almost unscathed.

Both these studies were conducted on relatively pristine coral reefs, free from local human stressors such as fishing, pollution, coastal development and tourism. But the same ability of corals to recover from bleaching events has been demonstrated in research on Australia’s famed Great Barrier Reef, many parts of which are subject to such stressors.

Studies in 2021 and 2020 (see here and here) found that both the Great Barrier Reef and coral colonies on reefs around Christmas Island in the Pacific were able to recover quickly from bleaching caused by the 2015-17 El Niño, even while seawater temperatures were still higher than normal. Recovery of the Great Barrier Reef is illustrated in the figure below, showing that the amount of coral on the reef in 2021 and 2022 was at record high levels, in spite of extensive bleaching a few years before.

Apart from making a number of arbitrary and questionable assumptions, the new University of Hawai‘i research is fundamentally flawed because it fails to take into account the ability of corals to rebound from potentially devastating events.

Next: Recent Marine Heat Waves Caused by Undersea Volcanic Eruptions, Not Human CO2