Historic Oden Expedition Reveals Unmapped Seafloor Features Behind Loss of Greenland Ice Tongue

The first scientific findings from the landmark GEOEO North of Greenland 2024 Expedition, conducted aboard Swedish icebreaker Oden, have revealed how previously unmapped seafloor features explain in part why the ice tongue of C.H. Ostenfeld Gletsjer in North Greenland disappeared in the early 2000s while neighbouring glaciers retained theirs. The study, published in Nature Communications Earth and Environment, shows that warm Atlantic water is able to reach the glacier margin through Victoria Fjord because the fjord lacks the shallow protective sill present in adjacent systems that limits warm water intrusion, providing the first evidence-based explanation for a long-standing scientific puzzle.

 

The Expedition and What Was Discovered

 

The Swedish icebreaker Oden became the first vessel ever to reach and collect scientific data in Victoria Fjord, one of the most remote and previously unsurveyed marine areas in the Arctic. The 2024 expedition collected bathymetric and oceanographic data that for the first time mapped the shape of the seafloor beneath this fjord, revealing the absence of a shallow protective sill that functions as a natural barrier in neighbouring Ryder and Petermann fjords. That sill geometry in adjacent systems limits the volume of warm Atlantic water that can reach glacier margins by creating a physical threshold that warmer, denser deep water cannot easily cross. Victoria Fjord has no equivalent barrier, allowing warm water direct access to the glacier front and explaining why C.H. Ostenfeld Gletsjer has followed a different trajectory from its neighbours. Martin Jakobsson, Professor of Marine Geology and Geophysics at Stockholm University and one of the expedition's chief scientists, has described the findings as demonstrating how features hidden beneath the ocean surface can influence what happens at the glacier front.

 

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Significance for Greenland Ice Dynamics and Climate Science

 

The discovery carries significance well beyond a single glacier. North Greenland's major outlet glaciers drain an enormous volume of the Greenland Ice Sheet into the ocean, and the rate at which they lose mass is one of the most consequential variables in projections of global sea level rise. Understanding why individual glaciers respond differently to warming ocean conditions requires knowledge of the specific oceanographic and bathymetric context of each system, and the Victoria Fjord findings illustrate how incomplete seafloor mapping has left critical gaps in this understanding. If similar unmapped sill structures or their absence are found in other Arctic fjords, they could explain divergent glacier behaviour across the ice sheet in ways that current models have not been able to capture. The findings also reinforce the principle that ocean warming and glacier retreat cannot be understood without detailed knowledge of the physical seafloor architecture that mediates how heat is delivered to ice margins.

 

Contribution to Arctic Seafloor Mapping and Seabed 2030

 

The expedition produced the first detailed bathymetric measurements from Victoria Fjord, and the newly acquired data have since been incorporated into updates of the International Bathymetric Chart of the Arctic Ocean. For Seabed 2030, the global initiative aiming to map the entire ocean floor by 2030, the findings provide a compelling demonstration of why Arctic mapping is scientifically essential rather than purely exploratory. The shape of the seafloor directly influences how water circulates through fjord systems, how warm water interacts with glacier margins, and ultimately how rapidly ice is lost to the ocean. Jakobsson has framed the results as a powerful reminder of how much remains to be learned about the ocean and why seafloor mapping matters. With only 27.3 percent of the global seafloor mapped as of 2025, the Victoria Fjord case illustrates the scientific cost of the remaining knowledge gaps and the value of high-priority targeted mapping in remote and previously inaccessible areas.