Paleoclimate study finds cooling glaciers have changed patterns in the tropical Pacific Ocean

A research team led by National Taiwan University uses geochemical indicators from deep-sea sediments to reconstruct the upper ocean zonal gradient of the tropical Pacific Ocean during the last Ice Age, providing valuable constraints for future climate projections. did. Their findings are published in the journal Communications Earth & Environmental.

The tropical Pacific Ocean plays an important role in the Earth’s climate system. The El Niño phenomenon causes extreme weather and drought, causing havoc around the world.

To adequately prepare for future changes in the region, it is important that climate models are able to accurately simulate changes in mean conditions in the tropical Pacific Ocean. Unfortunately, most state-of-the-art climate models are unable to reproduce the pattern of sea surface temperature increases observed in the tropical Pacific Ocean over the past century.

To further evaluate the performance of these models under different atmospheric CO2 levels, postdoctoral researcher Alicia Hou (University of Bordeaux) and Associate Professor Sze Ling Ho of the National Taiwan University Oceanographic Institute, and the University of Bremen and Queen Mary University collaborators conducted the study. The University of London collated paleotemperature estimates from past climates characterized by contrasting atmospheric CO2 levels to compare with model simulations.

These paleotemperature estimates are inferred from geochemical indicators analyzed on microfossils extracted from deep-sea sediments. Microfossils are also known as paleoclimate proxies.

Before performing the proxy model comparisons, the team first used the algo data to find out how some temperature metrics commonly used in paleoclimate reconstructions were observed in the upper tropical Pacific Ocean during El Niño and La Niña events. We have confirmed that it is actually possible to capture changes in the ocean’s thermal state.

We then generated a multi-model ensemble using simulations from seven state-of-the-art models based at institutions in North America, Europe, and Asia under the auspices of the Paleoclimate Modeling Intercomparison Project (PMIP).

Comparison results of proxy models show that these models were unable to reproduce the cooling pattern in the tropical Pacific when atmospheric CO2 levels were about half of today’s levels, similar to the warming observed in the last century. It shows that.

The discrepancy between the proxy and the model may be due to the fact that the model overestimates sea surface temperature changes in the eastern tropical Pacific. This proxy result also suggests that if greenhouse gas emissions continue unabated into the future, the western Pacific Ocean could warm even more than the eastern Pacific Ocean.

In summary, this study demonstrates the utility of paleoclimate proxies in improving climate models and informing future climate projections.