Researchers have identified that carbon dioxide levels and ocean currents play crucial roles in the temperature changes observed in the tropical Andes over the last 16,000 years.
A recent study focusing on ancient temperature and rainfall trends in the tropical Andes of South America has shed light on how climate conditions in this region have been influenced by carbon dioxide and global ocean currents over a span of 16,000 years.
Conducted by researchers from Brown University, this marks the first detailed temperature record for the tropical Andes spanning the past 16,000 years. This research could assist scientists in predicting and addressing future climate challenges in tropical areas around the world. The study is featured in the Proceedings of the National Academy of Science.
According to Boyang Zhao, a researcher from Brown’s Department of Earth, Environmental and Planetary Sciences and the lead author of the study, “Typically, when examining climate changes from the past, we focus on the Northern or Southern Hemispheres because of their significant influence on the global climate.” He added, “One of the primary objectives of our research is to uncover the factors that have shaped temperature history in this tropical region to apply our findings to other tropical areas.”
Besides looking ahead, the study also offers valuable insights into how different regions around the world impact each other’s temperature and weather patterns, highlighting the interconnectedness of regional climates and global climate changes.
“Our findings indicate that temperatures in this region are significantly impacted by the Southern Hemisphere, particularly areas like Antarctica,” Zhao explained.
The research involved a detailed analysis of sediment samples from Laguna Llaviucu, a lake situated in Cajas National Park, Ecuador. The data collected from these sediment samples reveal that temperature changes in the tropical Andes closely corresponded with global climatic events that caused temperatures to fluctuate over the past 16,000 years.
The evidence suggests that carbon dioxide concentrations were the primary factor influencing these temperature shifts. Researchers observed a strong correlation between the temperatures in the tropical Andes and those in Antarctica, which are largely influenced by carbon dioxide levels. The results demonstrated that between 17,000 and 14,000 years ago, as carbon dioxide increased, temperatures in the tropical Andes also rose, while stable carbon dioxide levels around 12,000 years ago kept temperatures relatively constant.
Zhao stated that this research reaffirms earlier studies that identify carbon dioxide as a significant driver of global temperature changes since the end of the Ice Age.
The study also underscored the importance of ocean currents in transporting warm water from the tropics to the North Atlantic. During a cooling phase known as the Antarctic Cold Reversal around 14,500 years ago, these northward currents were intensified, resulting in more heat being transported north and leading to cooler sea surface temperatures in the south. This cooling trend was found to have impacted the tropical Andes as well.
To reconstruct the climate conditions of the past, researchers analyzed lipid biomarkers and hydrogen isotopes that were collected in 2009 from Laguna Llaviucu by Mark Bush from the Florida Institute of Technology. Lipid biomarkers are chemical substances that provide insight into historical temperatures and rainfall patterns. The high-resolution data, along with precise dating techniques, enabled the team to develop a comprehensive timeline of climatic changes over the last 16,000 years.
The researchers noted that this is the first instance of using organic biomarkers to create a quantitative climate history for tropical South America, which is often challenging due to the difficulty of reconstructing temperatures in tropical regions.
The findings also reveal various regional differences in temperature trends, showing, for example, that while the tropical Andes and Southeast Asia experienced cooling during certain periods, Africa did not. The study highlights how local conditions may mitigate the global impacts of rising carbon dioxide levels by contrasting past temperature models with their sediment data.
Moving forward, the researchers from Brown University intend to further investigate historical temperature trends in this area, which has traditionally been underserved in terms of complete climate records.
James Russell, a professor of Earth, Environmental, and Planetary Sciences at Brown, who supervised the research, stated, “Mountain environments are among the most vulnerable areas on the planet when it comes to climate change. In the coming years, we expect regions like the Andes, especially high tropical mountains, to experience a warming rate that is second only to the Arctic, which is currently the fastest-warming part of the Earth.”
In addition to Zhao and Russell, undergraduate student Aaron Freeman from Brown contributed to this study, which received support from the U.S. National Science Foundation.
