Dr. Hsun-Ming Hu using clean room instruments at the Department of Geosciences, NTU.
For millions of years, Earth has experienced cycles of ice ages and warm periods. Today, we are in a warm period heavily influenced by human activities. As greenhouse gas levels rise, global warming intensifies, causing ice sheets to melt and sea levels to rise, posing severe threats to ecosystems and human societies. Understanding past extreme warm periods is therefore crucial.
The hottest warm period in the past million years occurred around 400,000 years ago. Surprisingly, during this period, solar radiation was weak and greenhouse gas levels were lower than today. This period, known as the "MIS 11c Paradox (1),," has long puzzled scientists. Dr. Hsun-Ming Hu, a postdoctoral researcher at the Department of Geosciences, National Taiwan University (NTU), and an international team led by Prof. Chuan-Chou Shen have solved the mystery. Using speleothem data from Mediterranean caves and North Atlantic marine records, their research has revealed the causes of this anomalous warmth. Their findings were published in Nature Communications on July 15, 2024 (2).
Solving the “MIS 11c Paradox” requires understanding the interactions between Earth’s ice sheets, oceans, and atmosphere in response to solar radiation. Precise dating has been challenging for decades. In 2014, the NTU team drilled a two-meter-long speleothem core from Bàsura Cave in Italy. Using high-precision uranium-thorium dating to provide accurate and robust age control, the team reconstructed the environmental history of southern Europe from 480,000 to 360,000 years ago. The research shows that around 426,000 years ago, increased summer solar radiation in the Northern Hemisphere caused extreme warming in the mid-to-low latitude Atlantic. This warming, combined with Earth’s increased tilt, prolonged heat transfer to high latitudes, causing long-lasting ice sheet melting. MIS 11c demonstrates that prolonged ocean warming can cause significant ice sheet collapse and sea level rise without extremely high atmospheric temperatures or greenhouse gas concentrations.
This study, supported by NTU and the National Science and Technology Council and involving researchers from 20 institutes worldwide, underscores the crucial role of oceans in driving global warming and ice sheet collapse.
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(2) Hu, H.-M., Marino G., Pérez-Mejías C., Spötl C., Yokoyama Y., Yu J., Rohling E., Kano A., Ludwig P., Pinto J. G., Michel V., Valensi P., Zhang X., Jiang X., Mii H.-S., Chien W.-Y., Tsai H.-C., Sung W.-H., Hsu C.-H., Starnini E., Zunino M., and Shen C.-C. (2024) Sustained North Atlantic warming drove anomalously intense MIS 11c interglacial. Nature Communications 15, 5933.
NTU team members Dr. Hsun-Ming Hu (right), Ms. Wei-Yi Chien (left 2), and Ms. Chun-Yuan Huang (left 1), with European collaborators.
Graduate student Wen-Hui Sung of the Department of Geosciences, National Taiwan University, operating a drilling machine to extract limestone core samples in Bàsura Cave, northern Italy.
Limestone core samples collected from Bàsura Cave, northern Italy. The black-and-white alternating bands represent a scale measured in centimeters. Researchers follow the scale in extracting small subsamples ranging from 0.1 to 100 milligrams for carbon and oxygen isotope analysis, trace element determination, and uranium-thorium dating.
Professor Chuan-Chou (River) Shen (right) and Dr. Hsun-Ming Hu (left) next to multi-collector inductively coupled plasma mass spectrometer housed at the Department of Geosciences, NTU.
