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New publication on the reconstruction of the intertropical convergence zone

Jun 27, 2024
Where the trade winds from the northern and southern hemispheres meet, there is heavy cloud formation and heavy precipitation. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; M. Mohtadi
Where the trade winds from the northern and southern hemispheres meet, there is heavy cloud formation and heavy precipitation. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen; M. Mohtadi

Statements about the climate of past times are often based on reconstructions using various parameters. The validity of these reconstructions depends largely on the data available. In their latest publication in the journal PNAS (Proceedings of the National Academy of Sciences), PD Dr. Mahyar Mohtadi from MARUM – Center for Marine Environmental Sciences and colleagues argue that the application of the right analytical methods is crucial.

 

The study focuses on the so-called Intertropical Convergence Zone (ITCZ), a low-pressure trough near the equator whose position and intensity changes seasonally with the position of the sun. Trade winds from the northern and southern hemispheres meet here. This results in heavy cloud formation and heavy rainfall. To analyze how the ITCZ has changed over the past 30,000 years, researchers use the stable oxygen isotope Delta-O-18 in calcareous deposits in cave systems on land and deposits of calcareous organisms on the ocean floor.

By releasing enormous amounts of water vapor and latent heat into the atmosphere, the position and strength of the ITCZ over the Indo-Pacific Warm Pool (IPWP) is of particular importance for global climate regulation.

While recent studies of the ITCZ have already fundamentally improved our understanding of the mechanism over the past millennia, Mohtadi and his colleagues used empirical orthogonal functional (EOF) analysis to examine the data in relation to precipitation in this and other regions.

The team was able to identify the main components for the size, strength and position of the ITCZ. They came to the conclusion that the inclination of the Earth's axis and the eccentricity of the Earth's orbit around the Sun have significantly influenced the size of the ITCZ in the past.

"It is important to understand whether the rain belt shifts, intensifies or relocates under different environmental conditions, also with regard to the current global warming," explains Mahyar Mohtadi. "Our study shows how this information can be filtered out of the data, at least in this region."

Contact:

PD Dr. Mahyar Mohtadi
MARUM - Center for Marine and Environmental Sciences, University of Bremen
Low-Latitude Climate Variability
Phone: +49 (0)421 - 218 65660
E-mail: [Bitte aktivieren Sie Javascript]

More information:

Original publication:

Fuzhi Lu, Francesco S. R. Pausata, and Mahyar Mohtadi: Reconstruct the intertropical convergence zone over the Indo-Pacific Warm Pool with extended records and empirical orthogonal function. PNAS 2024. DOI: https://doi.org/10.1073/pnas.2408502121

MARUM produces fundamental scientific knowledge about the role of the ocean and the seafloor in the total Earth system. The dynamics of the oceans and the seabed significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These influence both the climate and the global carbon cycle, resulting in the creation of unique biological systems. MARUM is committed to fundamental and unbiased research in the interests of society, the marine environment, and in accordance with the sustainability goals of the United Nations. It publishes its quality-assured scientific data to make it publicly available. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through its dialogue with society. MARUM cooperation with companies and industrial partners is carried out in accordance with its goal of protecting the marine environment.