Tonga volcano erupts, but the spewing of hot magma could cause global temperatures to drop?

Recently, the Hunga Tonga volcano (20.5°S, 175.4°W) in the Tonga Sea erupted and triggered a large-scale tsunami.

Tonga volcano eruption on H8 satellite image

(Image source: JMA)

According to Xinhua News Agency, the volcano on Hongahaapai Island, about 65 kilometers north of Nuku'alofa, the capital of Tonga, began to erupt on the morning of January 14, 2022 (Beijing time), and erupted again in the afternoon of January 15. The eruption of the volcano caused a large amount of volcanic ash, gas and water vapor to enter the high altitude to form a huge cloud, which erupted to an altitude of 20 kilometers.

Volcanic eruption on H8 satellite image

(Image source: tropicaltidibits)

After the volcanic eruption on the 14th, the Tonga National Tsunami Warning Center issued a national tsunami warning. The Meteorological Bureau said that the entire Tonga was facing the threat of tsunamis, heavy rains, floods and strong winds. The volcanic eruption on the 15th caused seawater to flow back, and the main streets of the capital Nuku'alofa were flooded, and many buildings were flooded.

Satellite photo of the Tonga volcano eruption

(Photo source: Kankan News)

The tremendous power of the volcanic eruption caused abnormal sea water movement in parts of many countries. Fiji, Samoa, Vanuatu, New Zealand, Australia, Japan, the United States and Chile also issued tsunami warnings.

Part 1

The Year Without a Summer: What is the Connection Between Volcanic Eruptions and Climate?

If you think that volcanic eruptions only cause lava to burn the earth or tsunamis to occur in coastal areas, you are wrong.

In addition to causing huge losses of life and property to local people, volcanic eruptions can also have a lasting impact on climate change, such as lower summer temperatures and abnormal rainfall, and their intensity is very high.

Historically, volcanic eruptions have led to "years without summer". In 1815, the eruption of Tambora in Indonesia caused severe abnormal climate in the northern hemisphere, with rare low temperatures and blizzards in the summer, affecting Europe, America and Asia. The eruption of Tambora also caused widespread low temperatures and crop failures in my country, which was the direct cause of the three-year famine in Yunnan.

In the climate fluctuations of the last thousand years, volcanic activity has been an important factor affecting temperature changes.

Schematic diagram of the impact of volcanic activity on temperature fluctuations over the past thousand years in the IPCC AR4 report

(Image source: Reference 2)

The Volcanic Explosivity Index (VEI) was proposed by Professor Newhall of the United States Geological Survey and Stephen Self of the University of Hawaii at Manoa. It measures the intensity of a volcanic eruption through qualitative observations of the volume of ejecta and volcanic clouds. The larger the value, the greater the range of energy release and the degree of damage to the surrounding area.

Volcanic Explosivity Index and Its Characteristics

(Table source: Reference 7)

The VEI of the Tambora volcano in Indonesia, which caused the "year without a summer", was 7, and there are signs that the VEI of the Tonga volcano eruption may reach 6. The last time a VEI of 6 was reached was the 1991 eruption of the Pinatubo volcano in the Philippines, which caused global temperatures to fall 0.3-0.5 degrees below normal.

Part 2

It is obviously hot magma, why does it cause the climate to cool down?

So why are volcanic eruptions related to climate? Studies have shown that the impact of volcanic activity on the climate system mainly includes the following:

First, volcanic ash particles block solar radiation. Volcanic activity can release a large amount of hot volcanic ash and gas. The volcanic ash that enters the atmosphere can effectively block solar radiation, causing the temperature to drop. In addition, volcanic ash particles are large in size and weight, and stay in the atmosphere for a long time, generally between 6-12 months.

For example, when Mount St. Helens in Washington State erupted in 1980, researchers found based on ground meteorological data recorded at observation points that the daytime temperature on the day of the eruption dropped by as much as 8°C due to the influence of volcanic ash.

Second, sulfuric acid aerosols scatter and reflect solar radiation. Strong volcanic eruptions inject large amounts of sulfur-containing gases into the atmosphere, which undergo a series of chemical reactions to form sulfide aerosols in the lower stratosphere. At the same time, they also change the balance of SO2, CO2, H2S, CH4 and tiny solid particles in the entire atmosphere, causing abnormal photochemical processes in the atmosphere.

Aerosols mix with water vapor to form volcanic clouds, which significantly reduce direct solar radiation reaching the surface and increase scattered solar radiation, thus reducing total surface radiation and causing cooling. In addition, stratospheric sulfide aerosol particles also absorb short-wave radiation in the near-infrared band and long-wave radiation emitted by the surface and lower atmosphere, causing the stratosphere to warm.

Volcanic clouds spread rapidly around the world within 2-3 weeks due to atmospheric circulation, and can even affect the global climate. A large volcanic eruption can cause global temperatures to drop by 0.2-0.5°C. There is no precipitation in the stratosphere to cleanse the air, so volcanic aerosols can remain for up to 2-3 years.

For example, when Mount Pinatubo in the Philippines erupted in 1991, real-time monitoring results from instruments equipped on satellites to measure global ozone concentrations showed that more than 20×10^12g (Tg) of gaseous sulfur dioxide and volcanic ash were transported into the stratosphere. After a series of reactions, these volcanic materials eventually produced about 30×10^12g of H2SO4/H2O aerosols. In the two years after the eruption, aerosols continued to have an impact on the climate.

Third, aerosols produced by volcanic eruptions affect the chemical reaction of ozone in the stratosphere. The generation and reduction of stratospheric ozone will affect the flux of stratospheric ultraviolet radiation. Volcanic eruption aerosols can not only affect the stratospheric temperature, but also provide more aerosol surfaces as reaction sites for ozone, thereby changing the rate of chemical reactions, reducing stratospheric ozone concentrations, reducing ultraviolet radiation absorption, and reducing radiation heating at the bottom of the stratosphere. However, due to the absorption of other bands and ground long-wave radiation by volcanic eruption aerosols, the overall stratospheric temperature will still rise.

Fourth, volcanic eruptions also affect the climate by affecting the local atmospheric circulation system. After learning about a few real events, you may have discovered that strong volcanic events usually lead to cooling in summer. But in winter, the temperature rises and falls in most parts of North America and Eurasia, and the extent of the change depends on the location of the eruption point.

Two volcanic events in the tropics in recent decades have caused warmer winter temperatures in parts of North America and Europe in the years of the eruptions. In this scenario, low-pressure systems and cold air are trapped in high latitudes for a long time, resulting in stronger westerly circulations that carry more warm and humid ocean air to the land, leading to warmer winter temperatures in the affected areas.

Schematic diagram of the impact of volcanic eruptions on climate

(Image source: Reference 2)

my country's climate is also significantly affected by strong volcanic eruptions, and many inter-annual climate anomalies are closely related to strong volcanic eruptions. For example, after the eruption of Mount Pinatubo in the Philippines in 1991, China experienced low temperatures in summer and autumn in 1992, and cold damage of varying degrees occurred in the Northeast to Inner Mongolia and the lower reaches of the Yangtze River.

Regarding the trend of temperature changes in my country after a strong volcanic eruption, relevant studies have shown that in the 1-2 years after a strong volcanic eruption, my country's temperature is basically falling, but there are significant regional and seasonal differences in the intensity of the temperature drop. The areas with obvious temperature changes in my country in the winter half of the year are mainly concentrated in the Qinghai-Tibet and eastern and central regions, followed by the southeast region, and finally the northwest and northeast regions.

The impact of strong volcanic eruptions at different latitudes and seasons on regional temperature differences in my country during the winter half of the year

(Image source: Reference 3)

In my country, the areas affected by volcanic eruptions in the summer half of the year are smaller than those in the winter half of the year. They are mainly concentrated in the Qinghai-Tibet and Northeast China regions, and there are obvious differences in temperature increases and decreases in each region.

The impact of strong volcanic eruptions at different latitudes and seasons on regional temperature differences in my country during the summer half year

(Image source: Reference 3)

Part 3

Tree rings and ice cores: Sima Qian from nature

In addition to satellite monitoring, what other ways can humans learn about volcanic activity? In fact, nature knows everything. The impact of volcanic activity on temperature, precipitation, etc. will be recorded by tree rings, corals, stalagmites and other media, providing reference materials for scientists to study the impact of volcanic eruptions on climate.

Tree rings, with their high resolution, large number of copies, accurate dating and wide distribution, provide important support for determining the time of historical strong volcanic eruptions and studying their impact on climate change. As early as the 1930s, American researchers began to use tree ring data to date volcanic events. By comparing the relationship between frost rings of trees in the western United States over the past 5,000 years and meteorological events and major volcanic activities, the researchers believed that strong volcanic eruptions were one of the factors for the appearance of frost rings.

Growth rings on a cross section of a tree trunk

(Image source: Wikipedia)

Other studies have shown that low summer temperatures after volcanic eruptions are an important factor in the formation of shallow tree rings. For example, from 1398 to 1982, 66% of shallow tree rings in northern Quebec, Canada, coincided with volcanic eruptions. In summary, under certain conditions, characteristic tree rings can be used as direct evidence to determine the time of volcanic eruptions.

In addition to trees, ice is also an excellent recorder. Volcanic eruption materials or secondary aerosols can be transported to polar ice caps and mountain glacier areas through atmospheric circulation and preserved in ice. Compared with other media, ice cores have advantages in volcanic activity research that are unmatched by other media, such as high resolution, long time series, and the ability to truly record volcanic eruption materials.

Ice core sample taken from the drill

(Image source: Wikipedia)

In the 1970s, Danish glaciologists first realized that abnormal changes in the concentration of acidic substances (mainly sulfuric acid) in ice cores could reflect volcanic activity, and successfully used three Greenland ice cores to reconstruct the volcanic history of the past 200 years. Since then, many Antarctic and Greenland ice sheets and mountain ice cores have been used to reconstruct and study the history of volcanic deposition. Researchers can measure some important volcanic eruption parameters by measuring the chemical composition, particle content and other factors of each fault layer in the ice core.

Although the eruption of the Tonga volcano has not yet caused a disastrous impact on the Chinese coast, and there have been no reports of Chinese casualties so far, how this volcanic eruption will affect China and even the global climate still requires more data and further research by relevant experts.

References:

1. Xinhua News Agency, Beijing, January 16, Summary: Tonga's submarine volcano erupted and many countries issued tsunami warnings

2. Li Chuanjin, Ren Jiawen, Qin Dahe, Xiao Cunde, Hou Shugui, Ding Minghu. Research progress on climate impact of volcanic activity and its ice core records[J]. Journal of Glaciology and Geocryology, 2012, 34(04): 863-876.

3. Hao Zhixin, Sun Di, Zhang Xuezhen, Zheng Jingyun. Impact of strong volcanic eruptions on regional differences in temperature changes in China since the 20th century[J]. Progress in Geography, 2016, 35(03): 331-338.

4. Li Mingqi, Shao Xuemei. Preliminary study on the relationship between strong volcanic eruptions and temperature changes in the eastern Qinghai-Tibet Plateau in the past thousand years based on tree ring data[J]. Advances in Earth Science, 2016, 31(06): 634-642.

5. Chen Youping, Chen Feng, Zhang Heli, Hu Mao, Wang Shijie, Hadad Martín ARIEL, Roig Ju?ent Fidel ALEJANDRO. Association of strong volcanic eruptions since 1200 AD recorded in tree rings with climate and hydrological changes in the source regions of southern high Asia rivers[J]. Quaternary Sciences, 2021, 41(02): 323-333.

6. Chen Xin. Reconstruction of Northern Hemisphere Surface Temperature in the Last Millennium: Study on Multi-Scale Fusion Method[D]. Tsinghua University, 2017.

7. Huang Ting. Study on Holocene volcanic eruption events and paleoclimate responses recorded in Northeast China peat[D]. China University of Geosciences, 2013.

8. Daily Economic News, January 16: Tonga's submarine volcano erupted, and tsunami waves were detected in the coastal waters of China in the early morning of the 16th

Cover image from: Haike News

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