Volcanic eruptions linked to temporarily stronger marine cold spells

Volcanic winters are periods of colder temperatures caused by the blasting of sulfur-containing compounds into the atmosphere during volcanic eruptions. The resulting sulfate aerosols create a thin veil around the Earth, reflecting a portion of the sun’s rays and cooling the Earth’s surface.

Researchers recognize that several volcanic winters have occurred throughout recorded history. One example was  “The Year Without a Summer” in 1816, which followed the major 1815 eruption of Mount Tambora in Indonesia. More recently, the eruption of Mount Pinatubo in 1991 dropped global temperatures approximately 0.5C (0.9F). By lowering warmth worldwide, volcanic winters can also cause crop failure and resulting food shortages as well as changes in weather patterns.

While the effects of volcanic eruptions can be described on a global scale, the local disturbances observed during volcanic winters can vary greatly and can differ between air and water temperatures. One aspect of volcanic winters that has not been thoroughly investigated is the effect of volcanic eruptions on marine cold spells (MCSs), which are periods when sea surface temperatures (SSTs) remain unusually cold for at least five consecutive days relative to seasonally varying local conditions.

The factors influencing MCS intensity and frequency are local seasonal climatology and variability, spell persistence, regional water circulation and SST distribution. A team of researchers from Germany reasoned that volcanic winters could also play a role in MCSs and designed a study to assess their effects worldwide.

The researchers published the results of their investigation on November 06, 2026 in the paper “Uneven imprints of major volcanic winters on weakening global marine cold spells since 1850” in the journal Ocean-Land-Atmosphere Research (OLAR).

“We noticed that while the cooling effects of major volcanic eruptions have been widely studied, relatively little attention has been given to how these volcanic winters affect extreme cold events in the ocean. We therefore wanted to explore whether major eruptions left detectable signals in MCSs and whether these responses were similar or different across the world’s oceans,” said Raven Quilestino-Olario, doctoral researcher from the Institute of Geology and Mineralogy’s Quaternary Geology working group at the University of Cologne in Cologne, Germany and co-author of the research study.

The research team used a newly available dataset, Centennial in situ Observation-Based SST Estimates version 3 (COBE-SST3), to analyze reconstructed daily global upper ocean temperatures from 1850 to 2024. Armed with this information, the team could not only assess regional MCSs but also examine changes in MCS cumulative intensities following six large-scale, climate-changing volcanic eruptions (Krakatau 1883, Santa Maria 1902, Novarupta 1912, Agung 1963, El Chichón 1982 and Pinatubo 1991) to those that happened at other times.

“Our study shows that although cold extremes in the ocean have generally become less frequent and less intense over the past 175 years, major volcanic eruptions may temporarily interrupt this long-term pattern. We found that all six eruptions we examined were followed by signs of stronger marine cold spells after accounting for selected natural climate variations and long-term temperature trends,” added Jan Kempert, researcher at South Westphalia University of Applied Sciences in Hagen, Germany and first author of the research paper.

One of the more interesting findings the team reported was that oceans do not respond uniformly to volcanic winters. While some regions of the ocean will experience strong cold extremes, another area will have weaker or even opposite responses. Despite the average effects of a volcanic eruption on climate overall, regional ocean disturbances can and do differ.

The team’s use of the COBE-SST3 dataset was instrumental in their study, and the researchers plan to use the data to investigate another common phenomenon: marine heatwaves. “We hope to use the same long-term ocean temperature dataset to explore how marine heatwaves have changed over the past 175 years, this time placing greater emphasis on the uncertainties associated with historical observations,” said Quilestino-Olario.

Ultimately, this work is designed to help scientists better understand extreme ocean temperatures, whether they are warm or cold. “We also hope our research can provide useful reference information for other scientists, particularly when choosing ocean temperature datasets and understanding their strengths, limitations and uncertainties,” said Kempert.

This research was supported by the Deutscher Akademischer Austauschdienst (DAAD; Funding Program No. 57698564), the University of Cologne Graduate School of Geosciences (GSGS; Grant No. GSGS-2026A-T07) and Deutsche Forschungsgemeinschaft (DFG) Priority Program 1158.