Glaciers in tropical mountain ranges are experiencing climate change similar to those in the polar regions of Antarctica and the Northern Hemisphere. An international team of scientists is the first to show that the effects of greenhouse gases are impacting tropical glaciers in the Southern Hemisphere at the same pace as ice sheets in the north.
Much of what scientists have known about glacial changes came from records of ice growth and decay that occurred in the Northern Hemisphere. For the current study, the researchers analyzed sediments from Lake Junín – located high in the Peruvian Andes – to create a record of glacial changes stretching back 700,000 years.
“As we try to understand how climate works across the globe, we need more than just records that are influenced by and biased toward the Northern Hemisphere,” said Professor Robert Hatfield of the University of Florida.
The land-based lake record collected by the team matches the duration of ice core records from Antarctica. It also represents the longest time frame ever collected from the Southern Hemisphere.
“What makes our findings unique is that we were able to get a continuous and independently dated record of tropical Alpine glaciation for the first time,” said Professor Hatfield. “The key takeaway was that the tropics follow the same beat and same rhythm to what’s going on in the Northern Hemisphere.”
Glacier changes in both regions occurred simultaneously, despite variations in solar radiation. This suggests that the rise in atmospheric greenhouse gasses associated with changes in the volume of the ice sheets of the north is impacting the entire planet.
To collect the data, geologists launched a massive drilling mission at the lake in 2015, funded by the National Science Foundation and International Continental Scientific Drilling Program. 100 meters of sediment from the lake’s basin was collected. With the sediment recovered, researchers spent the next few years developing a solid age model.
Study co-author Christine Y. Chen of the Lawrence Livermore National Laboratory analyzed the uranium and thorium content of the sediments to determine how much time was represented by the sediment core.
“Scientists have known for nearly a century that rising greenhouse gases will affect the climate in every corner of the world, but we’ve been less certain about how rapidly changes in ice volume at the poles will propagate to the rest of the world.” Chen said.
“The high-altitude mountains in the tropics are essentially as far away from the poles one can get. We’ve now shown that ice in both regions have been growing and decaying synchronously with one another for nearly a million years, which further highlights the interconnectedness of our planet.”