Traces of Mt. Halla from 4,200 years ago predict climate change

It has been confirmed that the southward movement of the westerly jet is related to the increase in precipitation on Jeju Island. [Photo = Korea Institute of Geoscience and Mineral Resources]



Diatoms, phytoplankton with siliceous shells, are very sensitive and change depending on the environment. They are widely used as an important indicator for understanding past environments and climate change. Evidence of



abnormal climate that historically caused the decline of the Mesopotamian and Indus civilizations, as well as droughts in northern China and floods in the south, and extreme changes in precipitation patterns by region has recently been discovered through diatom analysis.



The research team of Dr. Jo A-ra of the Climate Change Response Research Center of the Korea Institute of Geoscience and Mineral Resources (KIGAM, President Lee Pyeong-gu) succeeded in restoring climate change during the Holocene by analyzing diatoms in sediment samples collected from Sara Oreum on Mt. Halla.



This study is expected to bring about a new turning point in future climate prediction by revealing the similarity between the global abnormal climate event (4.2 ka event) that occurred 4,200 years ago and the current extreme climate phenomenon.



The research team extracted samples of unconsolidated sediments and volcanic debris from the Saraoreum wetland at a depth of 0 to 10 m. They conducted radiocarbon dating and diatom community analysis. As a result, they confirmed that sand particle sediments and floating diatoms increased rapidly in Jeju Island 4,200 years ago. This



means that heavy rain and precipitation increased in Jeju Island amid extreme climate change. This result overturns the existing hypothesis that Jeju Island was very dry. This study is meaningful in that it suggests the possibility that Jeju Island wetland research can be used as an important indicator of climate change in the future.



The research team of the Korea Institute of Geoscience and Mineral Resources is monitoring at Saraoreum, Jeju Island. [Photo = Korea Institute of Geoscience and Mineral Resources]



The research team confirmed that the southward movement of the westerly jet, a strong wind blowing from west to east in the upper troposphere in the mid-latitude region, is related to the increase in precipitation on Jeju Island. The team analyzed



that the westerly jet moved south from high latitudes to low latitudes due to a decrease in solar radiation induced by orbital forcing, causing the precipitation belt to stay in Jeju Island and southern China, resulting in record-breaking heavy rain in certain regions including Jeju Island, while other regions experienced extreme droughts.



Since current climate change is also closely related to the movement of the westerly jet, this study provides very important clues for understanding today's abnormal climate problems and predicting and preparing for the future.



Based on the climate and environmental changes at the time of the abnormal climate event 4,200 years ago revealed through this study, the research team plans to study long-term climate pattern changes in Jeju Island and East Asia in the future.



Dr. Jo Ara said, "We expect this study to play an important role in finding answers to the climate crisis we face by serving as a bridge connecting the past and the present," and "We will make a practical contribution to dramatically increasing the accuracy of future climate predictions by improving climate change prediction models and strengthening global research cooperation."



The results of the study (title of the paper: Hydroclimatic variation on Jeju Island, Korea during the Holocene and its linkage to the westerly jet: A focus on the 4.2 ka event) were published in the March 2025 issue of 'Palaeogeography, Palaeoclimatology, Palaeoecology,' an international academic journal in the field of earth science.





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