Impact of climate change on Andean glaciers in sync with polar ice
Glaciers in tropical mountains are experiencing the same impact of climate change drivers as those in the polar regions of Antarctica and the Northern Hemisphere, according to a study published today in Nature.
The paper by an international team of scientists, including Robert Hatfield, assistant professor in the University of Florida’s Department of Geological Sciences, is the first to show that the effects of greenhouse gases and other drivers of Earth’s temperature are impacting glaciers in the South. Hemisphere at the same speed as the northern ice sheet. To derive their findings, the researchers used sediment deposits from Lake Junín, high in the Peruvian Andes, to create a record of glacial changes that stretch back 700,000 years.
Hatfield explains that much of what scientists know about past glacial changes comes from records of ice growth and decay occurring in the Northern Hemisphere.
“As we try to understand how climate works around the world, we need more than a record of being influenced by and biased towards the Northern Hemisphere,” Hatfield said.
The land-based lake records collected by Hatfield and his colleagues match the duration of the ice core record from Antarctica and cover the longest time frame ever collected from the Southern Hemisphere.
“What makes our findings unique is that we were able to obtain a continuous and independent record of tropical Alpine glaciation for the first time,” he said. “The key is that the tropics are following the same rhythm and rhythm as what’s happening in the northern hemisphere.”
Apart from variations in solar radiation between the two hemispheres, research shows changes in glaciers in both regions occur at the same time. This suggests that the increase in greenhouse gas concentrations in the atmosphere associated with changes in ice sheet volume in the north affects the entire planet simultaneously.
When the vast glaciers of the Andes are high, they erode the mountains around them, sending sediment contained in the meltwater into Lake Junín. In warmer times when glaciers are absent, carbonates are deposited in lakes instead.
To collect their data, geologists launched a massive drilling mission in the lake in 2015, funded by the National Science Foundation and the International Continental Scientific Drilling Program. Working around the clock for seven weeks, the group picked up 100 meters of sediment from the lake basin. With the sediments recovered, the researchers spent the next few years developing a solid age model.
Christine Y. Chen, a Lawrence Livermore National Laboratory scientist and co-author of the paper, analyzed the uranium and thorium content of the sediments to determine how much time the sediment core represented.
“Scientists have known for almost a century that rising greenhouse gases will affect the climate in every corner of the globe, but we are less sure about how quickly changes in polar ice volume will spread around the globe.” Chen said. “Highland mountains in the tropics are basically far from the poles. We have now shown that ice in both regions has been growing and decaying simultaneously with each other for nearly a million years, further highlighting the interconnectedness of our planet.”
In 2020, the group published its findings on the age of the sediments and set to work looking at its climate record. Using a combination of mineral magnetism and sedimentary geochemistry, geologists reconstructed the timing and magnitude of glacial changes over a period of 700,000 years.
According to Hatfield, the original plan for the research was formed during a workshop in 2009 and included 27 authors on the final published paper, including lead author, Donald T. Rodbell, of Union College in Schenectady, New York.
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