Florida State University researchers are part of the first global study on glacial organic carbon and have found that just like the snowflakes that form them, no two glaciers are identical.

The team, which included Department of Earth, Ocean and Atmospheric Science postdoctoral scholar Amy Holt and Professor Robert Spencer, analyzed the molecular composition of organic carbon from 136 mountain glaciers in 11 regions across six continents. They found that each glacier region has a unique organic carbon composition and that human activity in the area affects the type of organic carbon exported to rivers, which has implications for carbon’s role in the surrounding aquatic environments. These findings were published in Global Biogeochemical Cycles, a journal of the American Geophysical Union.

“This work uncovered that glaciers are really diverse, and they likely have variable roles in the carbon cycle, or the planet’s continuous recycling of carbon,” said Holt. “Glaciers and mountain ecosystems are experiencing some of the most extreme effects of climate change. It motivates me to know that my research contributes to our understanding of how these environments may change into the future.”

Located in alpine areas, mountain glaciers are smaller than the massive expanses of ice that form the world’s two remaining ice sheets in Greenland and Antarctica. By highlighting the role of geographic location on carbon stored in glaciers and exported from them as they melt, this research enhances understanding of glacial meltwater’s role in downstream ecosystems, which is critical for the health of global fisheries.

The researchers logged hours of strenuous, high-altitude hiking in extreme weather to collect glacier meltwater samples at the source. Holt visited roughly 40 glacier sites throughout Alaska in North America, Ecuador in South America, and Kyrgyzstan in Central Asia. The remaining sites were in the European Alps, Chile, Greenland, Nepal, New Zealand, Norway, Russia and Uganda. In addition to FSU, members of the 12-scientist team hail from the Swiss Federal Technology Institute of Lausanne and the University of Alaska Southeast.

“Many people assume glaciers are hostile, inert environments, but surprisingly, their organic carbon pool is really complex and varied,” said Holt, who completed her doctorate in environmental science at FSU in May 2024 under Spencer’s supervision. “These tiny organic carbon compounds help form the base of aquatic food webs as they can be an energy source for microorganisms, which release carbon back into the atmosphere when they respire.”

Glaciers receive organic carbon from a variety of sources, such as microbial activity on the glacier surface, as well as wind-deposited carbon from soils and fossil fuel combustion, which coats the glacier in industrial byproducts. As ice glaciers melt, a process exacerbated by climate change, carbon stored within and on the ice is released to downstream ecosystems.

“There has been huge debate about the source of glacial organic matter globally,” Holt said. “Past studies in different glacier regions have shown glacier organic carbon may be predominantly derived from microbes on the surface, whilst others have suggested it reflects fossil fuel combustion byproducts and recent human activity. This research reconciles these competing perspectives, showing that glacier organic matter is regionally distinct and derived from both sources.”

Areas with a history of industrial activity such as Alaska and Nepal — home to Mount Everest, the world’s highest peak — have higher relative contributions of carbon sourced from fossil fuel combustion as opposed to microbial activity. By contrast, samples from the remote regions of Greenland and New Zealand, for example, where there is less industrial impact, consisted primarily of carbon-containing matter produced by microscopic organisms within the glacial ecosystem.

“In the short term, the material exported in glacier meltwaters may act as a source of biologically available carbon for rapid use by organisms in downstream environments,” Spencer said. “In the long term, many glaciers will decline, shrink and ultimately disappear due to ice loss. There are important ramifications here for receiving waters that include productive fisheries, as changes in the carbon’s sourcing and composition could affect the health and productivity of these ecosystems.”

This research was supported by the National Science Foundation, the Winchester Foundation, the International Associate of Geochemistry, the FSU-headquartered National High Magnetic Field Laboratory, and the NOMIS Foundation, a private Swiss foundation that supports scientific endeavors across disciplines.

To learn more about Holt and Spencer’s work and research conducted in FSU’s Department of Earth, Ocean and Atmospheric Science, visit eoas.fsu.edu.

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The cycling of carbon through the environment is an essential part of life on the planet.

Understanding the various sources and reservoirs of carbon is a major focus of Earth science research. Plants and animals use the element for cellular growth. It can be stored in rocks and minerals or in the ocean. Carbon in the form of carbon dioxide can move into the atmosphere, where it contributes to a warming planet.

A new study led by Florida State University researchers found that plants and small organisms in Arctic rivers could be responsible for more than half the particulate organic matter flowing to the Arctic Ocean. That’s a significantly greater proportion than previously estimated, and it has implications for how much carbon gets sequestered in the ocean and how much moves into the atmosphere.

Scientists have long measured the organic matter in rivers to understand how carbon was cycling through watersheds. But this research, published in Proceedings of the National Academy of Sciences, shows that organisms in the Arctic’s major rivers are a crucial contributor to carbon export, accounting for about 40 to 60 percent of the particulate organic matter — tiny bits of decaying organisms — flowing into the ocean.

“When people thought about these major Arctic rivers and many other rivers globally, they tended to think of them as sewers of the land, exporting the waste materials from primary production and decomposition on land” said Rob Spencer, a professor in the Department of Earth, Ocean and Atmospheric Science. “This study highlights that there’s a lot of life in these rivers themselves and that a lot of the organic material that is exported is coming from production in the rivers.”

Scientists study carbon exported via waterways to better understand how the element cycles through the environment. As organic material on land decomposes, it can move into rivers, which in turn drain into the ocean. Some of that carbon supports marine life, and some sinks to the bottom of the ocean, where it is buried in sediments.

The researchers looked at the six major rivers flowing in the Arctic Ocean: The Yukon and Mackenzie in North America, and the Ob’, Yenisey, Lena and Kolyma in Russia. Using data collected over almost a decade, they built models that used the stable and radioactive isotope signatures of carbon and the carbon-to-nitrogen ratios of the particulate organic matter to determine the contribution of possible sources to each river’s chemistry.

Not all particulate organic matter is created equal Carbon from soils that gets washed downstream is more likely to be buried in the ocean than the carbon produced within a river. That carbon is more likely to stay floating in the ocean, be eaten by organisms there and eventually breathed out as carbon dioxide.

“It’s like the difference between a french fry and a stem of broccoli,” said lead author Megan Behnke, a former FSU doctoral student who is now a researcher at the University of Alaska, Southeast. “That broccoli is going to stay in storage in your freezer, but the french fry is much more likely to get eaten.”

That means a small increase in a river’s biomass could be equivalent to a larger increase in organic material coming from the land. If the carbon in that organic matter moves to the atmosphere, it would affect the rate of carbon cycling and associated climate change in the Arctic.

“I always get excited as a scientist or a researcher when we find new things, and this study found something new in the way that these big Arctic rivers work and how they export carbon to the ocean,” Spencer said. “We have to understand the modern carbon cycle if we’re really going to begin to understand and predict how it’s going to change. This is really relevant for the Arctic at the rate that it’s warming and due to the vast carbon stores that it holds.”

The study was an international endeavor involving researchers from ten different institutions.

“That pan-Arctic view of science is more important than ever,” Behnke said. “The changes that are occurring are far bigger than one institution in one country, and we need these longstanding collaborations. That’s critically important to continue.”

Paper co-authors included Suzanne E. Tank, University of Alberta; James W. McClelland, University of Texas; Robert M. Holmes and Anya Suslova, Woodwell Climate Research Center; Negar Haghipour and Timothy I. Eglinton, ETH Zurich; Peter A. Raymond, Yale University; Alexander V. Zhulidov and Tatiana Gurtovaya, South Russia Centre for Preparation and Implementation of International Projects; Nikita Zimov and Sergey Zimov, Russian Academy of Sciences; Edda A. Mutter, Yukon River Inter-Tribal Watershed Council; and Edwin Amos, Western Arctic Research Centre.

This research was supported by the National Science Foundation through grants for the Arctic Great Rivers Observatory.

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