Tracking Westerly Wind Directions Over the Past 6,500 Years

The Mediterranean region is well-known for its abundant biodiversity, facilitated by its mid-latitude location and influenced by warm, moist westerly winds. This region has nurtured and given rise to many of the most prominent, impactful, and shining examples of ancient civilizations over the past thousands of years. However, in recent years, due to the effects of climate change, weather disasters such as heatwaves and cold waves have intensified across the Mediterranean region, seriously threatening the livelihoods of local residents, regional food production, and has led to a modern ecological crisis. Without a deep understanding of this important westerly winds belt in the past, it is difficult to assess the future trends and the potential enhanced environmental threats for this region and beyond.

Dr. Hsun-Ming Hu of the Department of Geosciences, National Taiwan University (NTU), Dr. Shih-Yu Lee of the Research Center for Environmental Changes, Academia Sinica, and Professor Chuan-Chou Shen of the Department of Geosciences, NTU, led this international team by using cave stalagmite records combined with previous data and climate simulations, to reveal the detailed history of the westerly winds belt over the past 6,500 years. The research was published in the top journal Nature Communications on December 21 (1).

Similar to the previous research on the westerly winds during the Little Ice Age published in Nature Communications in August of this year (2022) (2), the team again used stalagmites from Bàsura cave in northern Italy to develop their current publication. Precise uranium-thorium dating and trace element analyses were conducted in the High-precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, NTU. Combined with carbonate oxygen isotope data provided by collaborative teams and additional published geological records from the Alps, Italy, and Spain, the precipitation patterns in southern Europe from 6,500 years ago were reconstructed. Dr. Hsun-Ming Hu further integrated the Bàsura cave data with terrestrial and marine records from Europe, the Mediterranean, and the North Atlantic. The results of climate simulations by Dr. Shih-Yu Lee revealed detailed processes and causes for the observed westerly wind drift.

Earth scientists have wanted to better understand the driving mechanisms controlling changes in the westerly winds belt in the Mediterranean region for a long time; however, research into these controls has been hampered previously due to a lack of effective methods for tracking shifting wind directions. In this study, Dr. Hu and the team overcame this difficulty by analyzing rain distributions caused by the drift of the North Atlantic high-pressure center, located around 30–40˚N, allowing the team to successfully track the westerly wind directions over the past thousands of years.

Geological records and simulation results show that when the high-pressure center is closer to the European continent, the westerly winds belt tends to blow more towards the northeast. On the contrary, when the high-pressure center is farther from the European continent, the westerly winds belt tends to blow more eastwards. The research also found that the drifting westerly winds can cause decadal rain fluctuations in the Mediterranean region and may have even affected the development of ancient civilizations in the Mediterranean and Mesopotamia, such as the Roman Empire (3), the ancient Egyptian dynasties, and the Akkadian Empire (1).

This major breakthrough represents the first time tracking westerly wind directions over the European continent for thousands of years is possible. These insights may provide a reference for predicting the future hydrological and climatic trends in Europe. This exceptional research was made possible through the combined efforts of twenty-seven domestic/international parties from Europe, America, and Asia, who were involved in various aspects of this project.

Publications:

1. Hu, H.-M. et al. (2022) Tracking westerly wind directions over Europe since the middle Holocene Nature Communications 13, 7866.
2. Hu, H.-M. et al. (2022) Split westerlies over Europe in the early Little Ice Age. Nature Communications 13, 4898.
3. Hu, H.-M. et al. (2022). Stalagmite-Inferred Climate in the Western Mediterranean during the Roman Warm Period. Climate,10, 93.

This research was published in Nature Communications on Dec 21, 2022.

Click the link to read this article: https://www.nature.com/articles/%20s41467-022-34952-9