A new study led by Brown University researchers provides insights into ancient temperatures and rainfall patterns in the tropical Andes of South America. Over the past 16,000 years, climate history in this region has been influenced by carbon dioxide levels and ocean currents from global climate events.
The study offers the first high-resolution temperature record for the tropical Andes and has the potential to aid in predicting and addressing future climate impacts in tropical regions.
“Usually when we study climate change in the past, we emphasize the Northern Hemisphere or Southern Hemisphere because of the outsized role they play in affecting climates all over the globe,” said Boyang Zhao, a scientist in Brown’s Department of Earth, Environmental and Planetary Sciences and the study’s first author. “One of the biggest questions we are getting at is what the driving factors behind temperature history are in this part of the tropics so that we can begin to potentially apply that data and knowledge to other tropical regions.”
The recent study not only sheds light on future implications but also offers a unique perspective on how remote regions can impact global temperature and weather patterns. It highlights the interconnectedness of regional climates and global climate changes.
“Our evidence here suggests that temperatures in this region of the world are more influenced by the Southern Hemisphere — so places like Antarctica,” Zhao said.
The study’s focal point was an analysis of sediment samples from Laguna Llaviucu, a lake in Ecuador’s Cajas National Park. The measurements from the sediment samples revealed that temperature fluctuations in the tropical Andes closely corresponded with climate events that affected global temperatures over the past 16,000 years.
The temperature fluctuations were predominantly driven by CO2 concentration according to the evidence. Researchers found a correlation between tropical Andean temperatures and Antarctic temperatures, which are primarily influenced by CO2 levels.
The study indicated that around 17,000 to 14,000 years ago, an increase in carbon dioxide led to rising tropical Andean temperatures, while stability in carbon dioxide levels about 12,000 years ago resulted in relatively stable temperatures. These findings support previous research that identifies carbon dioxide as a major driver of global temperature changes since the last Ice Age.
The study also emphasized the impact of ocean currents that transport warm water from the tropics to the North Atlantic. During the Antarctic Cold Reversal 14,500 years ago, the northward current intensified, leading to increased heat transport northward and cooling of sea surface temperatures in the south. The researchers observed that this cooling effect extended to the tropical Andes.
To reconstruct historical climate conditions, the scientists examined lipid biomarkers and hydrogen isotopes obtained from Laguna Llaviucu in 2009 by researcher Mark Bush from the Florida Institute of Technology. Lipid biomarkers are chemical compounds that offer insights into past temperatures and precipitation patterns. The team was able to create a detailed timeline of climate changes over the past 16,000 years by utilizing high-resolution data and precise dating methods.
This marks the first instance of organic biomarkers being used to construct a quantitative climate history for tropical South America, an area where it is traditionally challenging to reconstruct temperatures.
The study also identifies various regional variations in temperature trends, such as the cooling of the tropical Andes and Southeast Asia during specific historical periods compared to regions like Africa. Furthermore, the research indicates how local factors might offset the global impacts of increasing CO2 levels by comparing historical temperature models to sediment data.
Researchers from Brown University intend to investigate past temperature patterns in this region further, which has historically lacked comprehensive climate records.
“Mountain environments are some of the most sensitive regions on Earth to climate change,” said James Russell, a professor of Earth, environmental, and planetary sciences at Brown who oversaw the new research. “In fact, in the near future, high tropical mountains, such as the Andes, are predicted to experience a rate of warming second only to the Arctic, which is the fastest warming part of the planet.”
Journal reference:
- Boyang Zhao, James M. Russell, Ansis Blaus, Majoi de Novaes Nascimento, Aaron Freeman, and Mark B. Bush. Tropical Andean climate variations since the last deglaciation. Proceedings of the National Academy of Science, 2024; DOI: 10.1073/pnas.2320143121