The El Niño event has officially begun. The climatic event, which originates in the tropical Pacific and occurs at intervals of several years, will shape the weather of the entire planet for the next year or more and result in various climate extremes. El Niño-like conditions can also occur on longer time scales of decades or centuries.
This was demonstrated recently by an international research team led by Ana Prohaska of the University of Copenhagen and Dirk Sachse of the German Research Center for Geosciences (GFZ). Their analysis of biomarkers—organic molecules or molecular fossils from vascular plants—in the sediments of a lake in the Philippines showed an unusually dry phase in the region during the Little Ice Age between 1600 and 1900 AD.
The results have now been published in the journal Earth and Environment Communication. They show how important it is to understand the past dynamics of tropical climate in the Pacific Ocean for the improvement of climate models and the prediction of future climate change.
The El Niño phenomenon
A unique feature of the equatorial Pacific climate is its east-west asymmetry, with warmer waters in the west and cooler waters in the east. Easterly winds push surface water to the west, allowing equatorial upwelling to bring cooler water to the east. This asymmetry breaks down in today’s climate, leading to El Niño conditions that occur at irregular intervals every few years and last for 9-12 months.
During an El Niño event, sea surface temperatures along the equator rise from the Peruvian coast to the central Pacific. Southeast trade winds will weaken significantly, and light westerly winds may develop. In the western equatorial Pacific, which is otherwise characterized by abundant rain, an unusual dryness will occur, while the dry eastern edges of the Pacific may experience heavy rain.
Against the backdrop of global warming, El Niño is expected to bring record-breaking high temperatures and various extreme climate events around the world such as droughts, floods and wildfires, which will greatly affect life and benefit of millions of people.
Like the El Niño event on longer time scales
While El Niño is an interannual climate phenomenon, the tropical Pacific climate system can also exhibit El Niño-like behavior on longer time scales of decades and centuries, linked to the east -westward temperature gradient over the Pacific ocean.
Such behavior has been shown to occur in the recent past by a team led by Ana Prohaska, assistant professor at the University of Copenhagen and previously a visiting scientist at GFZ, and Dirk Sachse, group leader working at GFZ Section 4.6 “Geomorphology” and director of Topic 5 “Landscapes of the Future” of the Helmholtz research program “Changing Earth—Sustaining our Future.”
The team described such a pronounced transition to El Niño-like conditions during the second half of the Little Ice Age, which lasted from about 1630 to 1900 AD. generation where conditions have changed over a period of more than 200 years.
Insights into past climate through studies of sediment cores
The research team analyzed sediment cores collected in 2013 from Lake Bulusan in the northern Philippines. The sediment sequence provides insights into climate evolution over the past 1,400 years in a region that is now heavily affected by El Niño events.
In particular, the researchers analyzed the composition of stable hydrogen isotopes of leaf wax biomarkers (δDwax). These are molecular fossils that come from the protective surface layer of leaves from vascular plants. The analysis provides insights into the water supply in their lives.
The study showed a sudden and significant increase in δDwax values between 1600 and 1650 AD, indicating a shift to drier conditions in the western tropical Pacific during the second half of the Little Ice Age. The researchers attributed this change to a shift in the average state of the tropical Pacific Ocean related to zonal gradients, ie, east-west differences in sea surface temperature.
The importance of the current study for climate predictions
Ana Prohaska, lead author of the study, emphasized the importance of this research: “Our study provides compelling evidence for the intricate relationship between zonal gradients in sea surface temperature and hydrological patterns in the tropical Pacific. tropical climate system in the Pacific is critical for predicting future climate change and its potential impact on the vulnerable region.”
Dirk Sachse from the GFZ added, “Although there is increasing evidence that abrupt climate change has occurred in the past, current climate models are unable to capture such an abrupt change in the average state of the tropical Pacific . This emphasizes that the understanding of the underlying mechanisms is In the context of anthropogenic climate change, a better understanding of the drivers and consequences of the complex dynamics of the typical situation in the tropical Pacific is very important . an important role.”
More information:
Ana Prohaska et al, Abrupt change in tropical Pacific climate mean state during the Little Ice Age, Earth and Environment Communication (2023). DOI: 10.1038/s43247-023-00882-7
Provided by the Helmholtz Association of German Research Centers
Citation: New study reveals abrupt climate change in tropical Pacific during Little Ice Age (2023, July 3) retrieved on July 4, 2023 from https://phys.org/news/2023-07 -reveals-abrupt-shift-tropical-pacific.html
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