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Study Reveals Impact of Earth’s Orbital Changes on Hydroclimate in South-East Pacific

A research team from the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has conducted an extensive study analyzing 50,000 years of hydroclimate data from the South-East Pacific, utilizing moisture indicators found in marine sediment cores. Their findings indicate that variations in the Earth’s orbital parameters play a significant role in influencing precipitation patterns and humidity levels.

Comprehending the factors that affect historical hydration and precipitation is essential for predicting future hydroclimatic changes. Researchers are increasingly focusing on hydroclimate—encompassing all long-term weather patterns that determine precipitation and humidity levels. According to the Intergovernmental Panel on Climate Change (IPCC), as global climate shifts continue, the likelihood of hydroclimatic extremes, including severe droughts and intense rainfall, is set to rise.

Jérôme Kaiser from the IOW highlights the challenges of understanding hydroclimates and forecasting future scenarios due to the complex interplay of various influencing factors. He states, “Examining historical climate changes allows us to identify patterns and essential factors that affect climate trends.” His findings are detailed in a recent study published in Nature Communications, in collaboration with researchers from several institutions, including the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research and two universities in Chile—the University of Magallanes and the University of Chile.

The research involved analyzing sediment cores retrieved from depths ranging from 850 to 3,300 meters off the northern and southern coasts of Chile. These marine sediments, layered over millennia, serve as invaluable archives for reconstructing past environmental conditions through specific indicators known as environmental proxies.

The focus of this study was primarily on the presence of deuterium, a naturally occurring isotope of hydrogen found in the leaf wax of terrestrial plants, which ultimately ends up in marine sediments. Kaiser elaborates on the significance of deuterium levels, stating, “Different concentrations of deuterium indicate crucial information regarding precipitation conditions, such as volume and intensity, as well as the origins of the moisture that leads to precipitation.”

The results revealed distinct patterns in humidity sources and precipitation volumes in Chile’s mid-latitude hydroclimate: in southern Chile, predominant rainfall originates from sub-Antarctic westerly winds, while central Chile also sees contributions from subtropical sources. However, both regions experience significant fluctuations in these patterns over thousands of years.

Interestingly, the study found that fluctuations in precipitation volume and intensity adhere to specific time cycles, discernible only through the extensive historical record provided by sediment cores. These cycles are approximately 23,000 years in central Chile and 41,000 years in southern Chile. Such cycles correlate strongly with natural variations in Earth’s orbit around the sun, particularly phenomena such as precession, which affects the length of precipitation cycles by altering the Earth’s axial position relative to the sun.

This research illustrates how changes in the Earth’s axial tilt also influence climatic conditions. The adjustments in tilt result in varying solar radiation intensity across regions, which subsequently affects wind patterns that transport moisture and precipitation. While previous models have considered Earth’s orbital variability in broader climate contexts, this study provides concrete evidence linking these orbital influences to the hydroclimate patterns observed in Chile.

Kaiser notes that while natural variations in Earth’s tilt cannot solely account for extreme hydroclimatic events, recognizing the interplay of natural and anthropogenic factors is crucial. This understanding is essential for accurately assessing the impacts of human-induced climate changes, especially in regions like northern and central Europe, where similar orbital phenomena occur.

More information: Jérôme Kaiser et al, “Orbital modulation of subtropical versus subantarctic moisture sources in the southeast Pacific mid-latitudes,” Nature Communications (2024). DOI: 10.1038/s41467-024-51985-4

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phys.org