Tracing organic matter across Greenlandic fjords
What is our motivation?
The project aims to better understand the role that glaciers and glacial fjord systems play in the Arctic carbon cycle. This question is becoming increasingly important as the Greenland Ice Sheet is losing mass at an accelerating rate due to rapid Arctic warming.
© Lisa Bröder
Why does it matter?
Melting glaciers release organic matter that has been stored in the ice for long periods. If this material breaks down into CO₂ and escapes into the atmosphere, it could worsen human-driven climate change. On the other hand, glacier meltwater also delivers fresh nutrients to coastal waters, boosting phytoplankton growth that takes up CO₂. Because these processes act in opposite directions, understanding what controls the fate of organic matter is crucial for evaluating its impact on climate—but the mechanisms involved are still poorly understood.
Project Focus
The project investigates how much different sources of organic matter contribute to fjord waters (such as newly produced phytoplankton versus older material from soils or glaciers). It characterizes the chemical composition of this material and evaluates how easily various types of organic matter decompose into CO₂, as well as their potential storage timescales—whether dissolved in water or attached to particles. These properties ultimately determine whether organic matter is buried for long periods or broken down and returned to the atmosphere, shaping the role of fjords in ongoing climate change.
How will it be done?
Samples will be collected along land-to-sea transects within several fjords that differ in meltwater input, freshwater influence, and local climate. Carbon isotopes will be used to distinguish between sources of organic matter. Its chemical composition will be analysed at the molecular level using mass spectrometry. Susceptibility to decomposition will be assessed through serial thermal oxidation, a technique that separates organic matter based on the temperature at which it breaks down.
What will be collected?
At each site, sampling depths will be selected based on temperature and salinity profiles from the surface to the seafloor. Approximately 5 litres of water will be collected per depth using the ship’s sampling system. On board, samples will be filtered to separate particulate material from dissolved organic matter.
Members and partners
- Principal Investigator:
- Lisa Bröder – Department of Earth and Planetary Sciences, ETH Zurich, Zurich, Switzerland
- Other participants:
- Margot White – Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada