University of Innsbruck scientists discover climate change clues in pollen from hundreds of thousands of years ago

“It’s really important to understand what the climate’s doing, what it has done, what it’s going to do,” said polar explorer and caver Gina Moseley. “It affects all of us.”

By Louise Kim and Jessica Savage  

Medill Reports, Dec. 15, 2023  


Gina Moseley scales mountains and explores remote lands all in the name of understanding how the climate has been changing across hundreds of thousands of years and how that impacts current accelerating change.

“It’s really important to understand what the climate’s doing, what it has done, what it’s going to do,” said Moseley.  “It affects all of us.”

Moseley is an assistant professor of paleoclimatology at the University of Innsbruck in Austria and an accomplished polar explorer and caver. She’s part of the Innsbruck Quaternary Research Group and has led multiple expeditions to Greenland with the Greenland Caves Project.

Moseley primarily studies changes in the climate and environment in the Quaternary, the Earth’s geological period that spans from the ice ages from 2.5 million years into the present. It is known for its many cycles of glacial growth and retreat. Her work centers around finding insights from the past that can help predict how climate will change in the future – and at an accelerating pace due to human activity. 

In a 2019 expedition to Greenland, Moseley and a team of researchers from the University of Innsbruck found, in pollen, clues to the environments that existed across a time machine of past environments. The expedition was led by her Ph.D. student, Anika Donner.

In 2019, a team of researchers from the University of Innsbruck traveled to Greenland for clues to how climate has changed for the past hundreds of thousands of years.(Robbie Shone/GREENLAND CAVES PROJECT)

Studying pollen is an especially powerful way to understand what the natural world looked like hundreds of thousands of years ago. Scientists can identify many more details from pollen records, including narrowing in on specific plant species and when climate conditions in an area allowed them to grow.

Moseley’s team also discovered a special type of mineral deposits made of calcite on cave floors during their expedition. These mineral deposits are called speleothems, which simply means that the mineral deposits in caves were formed by water. They are not part of the bedrock of the cave – they’re layered, instead, over time by dripping water on top of the original stone.

The most common speleothems are stalactites and stalagmites, but Moseley’s team was looking for a special kind of speleothem that would unlock a completely new understanding of Greenland’s landscape from half a million years ago.

Speleothems are of such interest to scientists because they hold a key to map the past. 

Water travels through the entire water cycle: it evaporates from the ocean, enters the atmosphere, and falls as rain or snow. The water molecules are picking up information about the chemical makeup of their surroundings all along the way. 

These particular molecules, which created the speleothems, could have entered the cave site through multiple pathways, but scientists don’t yet know which pathway they took. Pollen often travels by air, which means the trees they came from could have been growing above the cave, or from somewhere else in Greenland.

Regardless of where the pollen came from, scientists generally understand how the speleothems formed. Once the water carrying the pollen through the water cycle combined with soil, it became a weak acid. It was just acidic enough to dissolve the rock underneath the soil and slowly make its way into the cave.

“So you end up with big sheets of calcite carpets, and they’ve still got layers like tree rings,” Moseley said. “But they go back much further than tree rings.”

She shared her findings at the annual Comer Climate Conference, an annual  gathering of top scientists in southern Wisconsin each fall. 

Once Moseley and her team collected samples and brought them back to the lab, the first thing they had to do was date them. They used dating methods that allowed them to place the pollen samples back more than 400,000 years ago.

The time machine had an incredible story to tell – “400,000 years ago is very similar to today in terms of how the Earth is settled relative to the sun,” Moseley said. “That gives us information about what should be natural today, if people hadn’t messed with the climate.”

They found pollen in their samples, which allowed them to identify which types of species were present in the area during that time period and how abundantly they grew. But pollen from evergreens hints at cooler weather while pollen from grasses, wild flowers or deciduous trees suggest warm spells. Little or no pollen ominously sketches a different kind of world.   

Moseley’s discovery allows her team to zero in on a particular species, which opens up a whole world of understanding what Greenland was truly like almost half a million years ago.

What they found in their samples was pollen from spruce, fir, and pine species. These species indicate that the landscape above the cave may have been a mixed boreal forest.

In the present day, 400,000 years later, there are absolutely no trees, likely due to growing seasons that are too cool. It’s a rocky, barren landscape with a thin layer of soil.

This discovery is so important because it tells us that in the short time scale – relative to other paleoclimate studies – Greenland changed incredibly fast for thousands of years. This offers an opportunity to understand how the global climate might have impacted Greenland, and how it can affect similar areas now.

Scientists from the University of Innsbruck search for samples to bring back to the lab. It was through these samples that Moseley and the research team were able to discover pollen from thousands of years ago. (Robbie Shone/GREENLAND CAVES PROJECT)

Moseley’s first brush with caving was when she was 12 during a family vacation. Her mother took her along for a lesson, and she’s been hooked ever since.

“Later at university, I found out you could do climate research in caves,” she said. “I just thought, ‘Wow, that’s amazing. That sounds like a cool job.’”

Her love for adventure soon turned into a desire to take on one of the world’s most pressing issues: climate change. 

The  period between ice ages 400,000 years ago was atypically long, lasting for around 30,000 years rather than 10,000 years. 

“That was long enough that most of the Greenland Ice Sheet melted anyway, just because it was long. and then forests developed.” Moseley said. “And this is really cool. And the question is, would that be the natural future for us anyway, regardless of humans messing with the atmosphere?”

Messing with the atmosphere means accelerating the climate impacts such as global warming due to fossil fuel emissions and  compressing what natural forces take thousands of years to do. Greenland is very sensitive to climate change – it’s ice sheet is melting at five times the rate it was melting just 20 years ago. Plus, caving offers scientists access to an even older history, compared to the well-researched ice sheet. 

Moseley’s latest expedition involved a trip to an unexplored cave far north of Greenland. She hoped that this untouched land would give her new insights into the warming and cooling periods of the past and their effects on the Arctic, which is heating up at an alarming rate. 

Moseley took her daughter Madeline caving for the first time when she was a few months old – not counting the trip Moseley took while she was still pregnant. These climate-focused explorations have a deeper meaning for her now – she hopes Madeline  will grow up in a better world.

“It became even more important to me to be able to understand what the climate’s doing because I’m concerned about [Moseley’s daughter’s] future world,” Moseley said.

Photo at top: Gina Moseley exploring caves for clues to climate past that help reveal the accelerating rate of climate change now. 

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