Created with special thanks to Profs.YAO Tandong and Lonnie Thompson for their groundbreaking research and generous help. The author also thanks Dr. YOU Chao and LIU Yingying for helping with early research for the piece as well as Laura Arenschield for sharing her inspiring report on relevant studies

 

It is shocking to think that up until 34 years ago, we knew little about the past of the high mountain region centered on the Tibetan Plateau, also known as the Third Pole. It is as astonishing to realize how much we have learned about it over the last 34 years. And a large amount of that knowledge can be traced back to ice cores drilled in the region.

 

Ice cores record histories dating back to 10,000 years ago

 

Lonnie G. Thompson and YAO Tandong were the first to provide this missing information. In 1986, they drilled the first ice cores in Third Pole glaciers. The three ice cores they obtained from the northeastern edge of the Third Pole cover a period as far back as about 10,000 years ago, when the area abruptly become warmer, drier and less dusty [1]. The ice cores also revealed that the 17th century was the coldest period for the area over the past 500 years, indicating that the Third Pole also was part of the Little Ice Age [2, 3]. The 60 years before the cores were drilled represented the warmest period over the last 10,000 years, according to ice core data. [1].

 

Drilling camp at Dunde Ice Cap (1986) Credit: Byrd Polar and Climate Research Center 

 

In 1992, the two scientists and their team drilled another ice core in the Guliya Ice Cap at a towering height of 6710 m above sea level. This core recorded how the temperature has changed in the western Third Pole over the past 2,000 years. These trends generally echo those recorded by Greenland ice cores, although they show faster speed and larger amplitudes [4, 5]. Taking a deeper look, the story told by the Guliya ice core is quite similar to those told by polar ice cores and ice cores from Quelccaya, Peru. These cores connect the Third Pole to the Arctic, the Antarctic as well as the equatorial region [6, 7]. Inspired by this finding and eager to know more, Thompson and Yao revisited the Guliya Ice Cap in 2015. This time they drilled a total of five ice cores. The ice cores are now being stored and studied at the Institute of Tibetan Plateau Research, the Chinese Academy of Sciences and the Byrd Polar and Climate Research Center, Ohio State University. Stay tuned for the next episode of the Guliya Ice Cores.

 

 

Guliya Ice Cap (1992), Credit: Byrd Polar and Climate Research Center

 

In 1997, Thompson and Yao went a bit higher, to the Dasuopu Glacier in the Southern Third Pole, and returned with three ice cores, making Dasuopu the world’s highest drilling site ever (7200 m above sea level). Temperature-wise, the Dasuopu ice cores corroborate the story of the Dunde ice cores [8]. Like the other ice cores, they point to a large-scale 20th-century warming trend in the Third Pole, which appears to be amplified at higher elevations [9]. But one thing stands out: methane. A dramatic increase in methane concentration beginning in the 18th century was detected in the Dasuopu ice cores, about 15%-20% higher than in the Antarctica and Greenland ice cores. This suggests human activity, as the methane concentration dropped during the periods of World Wars I and II [8, 10]. A closer examination also found higher-than-natural levels of toxic metals, which are byproducts of coal burning, in the ice starting around the beginning of the Industrial Revolution in the United Kingdom [11]. Apparently, wind was several steps ahead of humankind in leaving human footprints at the Third Pole. Growing human activity in India and Nepal, both upwind from the ice core site, is manifested in the ice cores as chloride concentrations doubled and dust quadrupled during the 20th century [9].

 

Drilling project logo 1997

 

 

 

Dasuopu Glaciers (1997)    Credit: Byrd Polar and Climate Research Center

 

The cycle of ice core studies can be lengthy. In fact, the most recent study of the 1997 ice cores was just published in 2020 and there are more ice cores waiting to be analyzed. In 2000, Yao led a team into the unpopulated zone in the central Third Pole, where they drilled three ice cores in the Puruogangri Ice Cap. Around the same time, other scientists did similar research. Three ice cores were obtained from East Ronbuk in the southern Third Pole in 2000-2001 and one from the Grigoriev Ice Cap in the northern edge in 2007.

  

How temperatures have changed over the last 2000 years  

Reconstructed from records of the Dunde, Guliya,Dasuopu and Puruogangri ice cores 

(pink for warm and purple for cold) [12]

 

What we know now is that warming at the Third Pole since the beginning of the 20th century is the greatest ever recorded, or at least the greatest for all periods shown in the ice cores [12]. TPE Scientists are now racing against time, as glaciers, and thus ice cores, are melting fast around the world, not least the Third Pole. Scientists need information recorded in these ancient ice cores to help better understand the Third Pole’s past and thus better prepare for the future of this key region, which along with its surroundings is home to 1.4 billion people.

 

 

 

 

References:

 

1. Thompson, L.G., et al., Holocene—late Pleistocene climatic ice core records from Qinghai-Tibetan Plateau. Science, 1989. 246(4929): p. 474-477.

 

2. Tandong, Y. and L.G. Thompson, Trends and features of climatic changes in the past 5000 years recorded by the Dunde ice core. Annals of Glaciology, 1992. 16: p. 21-24.

 

3. Yao, T., Y. Shi, and L. Thompson, High resolution record of paleoclimate since the Little Ice Age from the Tibetan ice cores. Quaternary International, 1997. 37: p. 19-23.

 

4. Yao, T., et al., Climate variation since the last interglaciation recorded in the Guliya ice core. SCIENCE IN CHINA (Series D) 1997. 40(6): p. 662-668.

 

5. Yao, T., Abrupt climatic changes on the Tibetan Plateau during the Last Ice Age——Comparative study of the Guliya ice core with the Greenland GRIP ice core 中国科学, 1999. 4.

 

6. Thompson, L., et al., Tropical climate instability: The last glacial cycle from a Qinghai-Tibetan ice core. science, 1997. 276(5320): p. 1821-1825.

 

7. Thompson, L.G., et al., A 1000 year climate ice-core record from the Guliya ice cap, China: its relationship to global climate variability. Annals of Glaciology, 1995. 21: p. 175-181.

 

8. Yao, T., et al., Temperature and methane records over the last 2 ka in Dasuopu ice core. Science in China Series D: Earth Sciences, 2002. 45(12): p. 1068-1074.

 

9. Thompson, L.G., et al., A high-resolution millennial record of the South Asian monsoon from Himalayan ice cores. Science, 2000. 289(5486): p. 1916-1919.

 

10. Yao, T., et al., Temperature and methane changes over the past 1000 years recorded in Dasuopu glacier (central Himalaya) ice core. Annals of Glaciology, 2002. 35: p. 379-383.

 

11. Gabrielli, P., et al., Early atmospheric contamination on the top of the Himalayas since the onset of the European Industrial Revolution. Proceedings of the National Academy of Sciences, 2020. 117(8): p. 3967-3973.

 

12. Thompson, L.G., et al., Abrupt tropical climate change: Past and present. Proceedings of the National Academy of Sciences, 2006. 103(28): p. 10536-10543.