Arabian Sea sediments reveal summer and winter monsoons shifted differently after last ice age

by Ulrike Prange, MARUM - Center for Marine Environmental Sciences

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High-resolution sediment analyses from the Arabian Sea reveal, for the first time, that summer and winter monsoons respond differently to global climate change. The study enhances understanding of past precipitation patterns and could help refine climate models for regions influenced by monsoons.

Researchers from MARUM—Center for Marine Environmental Sciences and the Faculty of Geosciences at the University of Bremen collaborated closely with colleagues at Johannes Gutenberg University Mainz and the University of Bern on the study. Their paper is published in the journal Nature Geoscience.

The South Asian monsoon is one of the most important climate systems on Earth. The annual shift between dry and rainy seasons affects the lives of more than 2 billion people. Despite its enormous significance, the factors driving its intensity, variability and response to ongoing climate change are still not fully understood. Current observational data span only a few decades, and climate models have so far provided only a limited picture of tropical precipitation dynamics.

To better predict future monsoon trends, researchers are turning to natural climate archives, such as ocean floor sediments, which store information about past environmental and climate conditions. Until now, most methods could reconstruct only long-term climate changes. Short-term fluctuations on a yearly or seasonal basis often remained hidden.

At the University of Bremen's MARUM—Center for Marine Environmental Sciences, a multinational, interdisciplinary team led by Dr. Igor Obreht analyzed sediment samples from the Arabian Sea. The team combined micrometer-scale imaging with conventional isotope methods. Their goal was to reconstruct past climate fluctuations with a resolution comparable to current climate trends, but under the fundamentally different conditions of the last deglaciation phase, when abrupt climate shifts occurred. Obreht was a postdoctoral researcher at MARUM before joining Johannes Gutenberg University Mainz as a junior professor.

The team carefully selected the sediment core because its various proxy signals respond sensitively to different components and seasons of the monsoon system, enabling a more comprehensive evaluation of monsoon dynamics. The study marks a successful collaboration between MARUM and the University of Bern