Tibetan Glacier Reveals History of Pollution

Puruogangri Ice Core Study

A team of scientists led by Emilie Beaudon and Paolo Gabrielli et al. from the Byrd Polar and Climate Center of Ohio State University conducted a study published in Science of the Total Environment presenting a 500-year atmospheric contamination history through the analysis of 28 trace elements from an ice core collected from the Puruogangri glacier in the central Tibetan Plateau. The purpose of the study was, as the authors indicated, “to assess different atmospheric contributions to the ice and provide a temporal perspective on the diverse atmospheric influences over the central Tibetan Plateau.”

The researchers found an overall increasing trend in the levels of trace elements within the ice core from 1497-1992. But what explains the increase of these trace elements in Tibetan glaciers? Was it due to natural or anthropogenic causes?

Atmospheric Dynamics and Tibet

The researchers indicate that the trace element contaminations in the ice core come from two main sources. Prior to 1900, natural causes (such as volcanic fallout) were the primary contributor present in the findings. But with global development of industrial processes in the 19th and 20th century, it became evident to the scientists that post-1900, the main contributors are from anthropogenic sources. The authors argue that the dominant source for the Cd, Zn, Pb, and Ag enrichment increase in the 20th century originates from the metallurgy emission products of former republics within the Soviet Union, particularly Kyrgyzstan and Kazakhstan.

Figure 1. A visual representation of global atmospheric circulation (Source: Creative Commons).

But how would pollutants from Soviet plants reach Tibet? Atmospheric circulation is the key. As Puruograngri lies on the 34th parallel, its position is along the path of the strong mid-latitude westerlies that blow from west to east across the Asian continent as seen on Figure 1 and a NASA GEOS-5 simulation demonstrating the movement of aerosols in atmospheric circulation. As a result, these winds deposit dust and any other particulates in the air on the tall, vast barrier of the Tibetan Plateau.

In addition to Soviet steel production, the authors mention a second proximal source. An increase of Chinese steel production during the Great Leap Forward (1958-1962) corresponds well to the increases in Sb and Pb enrichment in the ice core. But instead of the subtropical westerlies carrying the pollutants, the inconsistent summer monsoonal circulation patterns brought them from the east (China) and south (India and Southeast Asia). As Puruogangri straddles the summer monsoon-dominated south and the year-round dry, westerly-dominated north regions of the Asian continent, it receives influences from both atmospheric patterns depending on the time of year.

But in order to fully understand the significance of the Puruogangri ice core study, a historical perspective is also necessary. With increases in Soviet Union and Chinese steel production identified, it is important to understand the underlying dynamics of steel production in these two countries.

Historical Perspective of the Soviet Union and China

Central Asia was the crossroads of the continent that connected Europe and all parts of Asia with the Silk Road. After the Russian Revolution in 1917, the newly established Soviet Union fully incorporated Central Asia into its domain. As a means of building legitimacy in a new world order post-WWI, the Soviet government sought to transform the previously agricultural country to, as American historian Stephen Kotkin describes, a “country of metal.” A detailed account of the social history surrounding the Soviet industrialization may be found in Kotkin’s book Magnetic Mountain.

China’s Great Leap Forward (1958-1962)(Source: Orient’Adicta/Flickr).

Under the advisement of the Soviet Union, China underwent a similar economic transformation with the rise of the Chinese Communist Party and Mao Zedong in 1949. The study pinpoints the decadal events like the Great Leap Forward (1958-1962) and the Cultural Revolution (1966-1976) as significant periods of industrialization, corresponding to the anthropogenic Sb, Cd, Zn, and Pb levels peaking in 1965. Modern Chinese historian Gina Tam from Trinity University gave GlacierHub a deep-dive into why industrialization was particularly heavy in the 1960s in China.

After falling short of economic goals in the 1950s, Mao instigated a campaign called the Great Leap Forward in hopes to invigorate the economy. “The Great Leap Forward was, above all else, an emphasis on ‘leaping’ forward in terms of economic output. The key targets were steel and grain–the former to make China into a more industrialized country to compete with the West, and the latter to feed all those workers. Given that this was an ‘all hands on deck’ sort of situation, industrialization increased heavily during this time,” Tam told GlacierHub. Devastation followed in terms of mass starvations as well as widespread environmental degradation. Relating this history back to Puruogangri, today’s scientists were able to observe the magnitude of the emission production in both China and the Soviet Union.

What the Records Tells Us

While both of these countries hungrily pursued economic prosperity through metallurgical means, the policies in place put heavy pressure on natural resources and the local environment. The recent Puruogangri study reveals how atmospheric circulation serves as a conveyor belt for anthropogenic pollutants to reach remote glaciers like those in central Tibet.

As the authors noted, “the extraction of multi-century atmospheric pollution records from central Tibet is essential to assess the magnitude of the recent contamination of this remote region and to provide a long-term perspective for the changes observed.” What is particularly noteworthy about this statement is the purpose of scale. While the study assesses patterns across multiple centuries, the authors identify specific decadal events within the 20th century to emphasize a potential shift in the trace element enrichment prior to 1900. Heavy industrialization like during the Great Leap Forward stands out compared to other decades, but based on the results of this study, the researchers ultimately emphasize how the 20th century emission production stands out in comparison to previous centuries.

While scientists like Beaudon and Gabrielli analyze the glacial records for atmospheric contamination input, historians like Koji Hirata from Stanford University are analyzing the written records to trace the levels of steel production output. Despite the tumultuous political atmosphere in both countries throughout the 20th century, historical accounts correspond well with the glacial records. Bridging the understandings between the two disciplines, as well as others, may lead to more informed decision-making on emission controls, ultimately helping to mitigate our changing climate in the uncertain future.