Glacial geologist maps clues to climate change in the Andes Mountains

By Zach Boblitt  Medill Reports, Jan. 18, 2024

There’s one question glacial geologist Gordon Bromley doesn’t think he gets asked enough: “Do you enjoy your work?”.

Bromley, a lecturer in physical geography and climate lecturer at the University of Galway in Ireland, has been studying glacial moraines in the Andes Mountains in South America to see if they tell a similar story to the moraines in Ireland and Scotland.

The moraines in the Andes also run through Peru and most of western South America.

A moraine is a ridge of boulders, rocks, sand and gravel that are thrown aside like so many pebbles by the glaciers as they retreat.   When it comes to the study of moraines in the tropics, “there aren’t a lot of records.,” Bromley said. He would like to change that. Glaciers high in the mountains above the tropics left behind moraines in past retreats and glaciers disappearing now will leave more.

Bromley wants to find out whether the rate of deglaciation, the disappearance of ice from a previously glaciated region, at the close of the last Ice Age was similar in the tropics to the northeast North Atlantic. The retreat gives clues to the pace of deglaciation with climate changes now.

Bromley’s presentation at the annual Comer Climate Conference in southwestern Wisconsin this fall related glacial records and atmospheric temperature downwind of the North Atlantic Ocean. He looked for data to show whether or not there are atmospheric similarities in periods of deglaciation. The end goal of his ongoing Andes research is to find out how the atmosphere and other factors are driving climate variability in the tropics. Although not scientifically proven, Bromley has an idea what is driving the change. 

“In all likelihood, I think the changes in the production and export of latent heat and water vapor from the tropics by the tropical troposphere is probably setting the stage for a lot of the climate variability that we see in our glacial records from all over the world,” Bromley said at his Comer presentation. When it comes to whether or not Bromley enjoys his work he said, “I certainly do. I think this is the best job in the world.”

Below is an audio report about Bromley’s research.

Glacial geologist Gordon Bromley is a self-described glacier “detective” trying to reconstruct what happened thousands of years ago in the Colombian Andes Mountains based on evidence such as samples drilled from the boulders that date when a moraine became ice-free. Bromley does this so he can gain a better understanding  how the climate system works and how human activities such as fossil fuel emissions are forcing rapid climate change now. Bromley says his work starts with the mapping he’s doing in the Colombian Andes and elsewhere in the mountain range. “Mapping is always the first step, because it’s what gives you the lie of the land. It gives you the shape of your record.”  10 seconds The glacial moraines that Bromley is attempting to map tell the story of climate. He, along with a team of scientists and students, gets information from the glaciers by reconstructing “the crime scene” as Bromley describes it. In this case, it’s the rate of retreat of he ice that threw aside the boulders, rocks and soil that create the moraines Bromley says that the glaciers give him a historical temperature gauge. “From the mapping, where these glaciers were, where they came from if you’re using them as a thermometer which we are. A paleo thermometer, a big sort of landscape scale thermometer. Where did they come from? Where were they? How big were they? When did it go from this big to this big which would make it colder.” The detective work that’s done includes the normal geological tools. The most common tools geologists use include a hammer, a chisel and lab equipment for rock samples. These tools help, but two of the most important tools for a scientific sleuth is the mind and prior experience. Bromley previously worked in Peru. He studied the Peruvian Andes trying to find out when they reached their last glacial maximum, or ice age. So, he had the experience working the Andes Mountains. Bromley used his mind to find out about prior research in the region. He says that Dutch geologist and botanist Thomas van Der Hammen’s group did a good job of laying the foundation for someone to build on his work. “They (van Der Hammen’s group) had gone to various places in Colombia and done preliminary mapping and reported on the deposits basically. Saying, “hey this is really good stuff here and this is our interpretation of it.” Now, it didn’t really have any dating control, but that’s the kind of thing you need. We’re always building off of other people’s work. So, that was the information that was vital to say hey this stuff is here. These records are here, and not only that but they look incredibly well preserved.”  Van Der Hammen’s research gave Bromley and his team a clue. A road map of where to look in the Colombian Andes. This road map will help continue Bromley’s glacial detective work. As he discovers information about the tropics, or as he calls it the quote, “The heating engine of the world.” Bromley hopes to learn whether the glacial moraine record is the same in the tropics as it is in Ireland and Scotland, and IF it is, then why is it similar? The last pieces of the geological puzzle Bromley is searching for is when the warming happened in the Colombian Andes glaciers, and what triggered that warming. When those questions are answered detective Bromley will have to take on another case.