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How climate change could flip marine fluxes in the Arctic: reshaping entire ecosystems
15 September 2025
The Arctic is warming faster than almost anywhere else on Earth, with the Barents Sea experiencing the most dramatic loss of seasonal sea ice. As the ice retreats and the Polar Front shifts northwards, ecosystems are already being reshaped. Newly published PML research shows for the first time that these changes could fundamentally alter benthic–pelagic exchange – the flow of carbon and nutrients between the seafloor and open ocean waters vital for marine life and carbon cycling.
Image: A polar bear pictured during fieldwork for this project: Changing Arctic Ocean Seafloor (ChAOS). Image credit: Dr Johan Faust
Both the Polar Front* and the southern boundary of seasonal sea ice have shifted northwards over time, by about 150km (93 miles) since 1960.
* The Polar Front is the boundary between the cold, dense air of the polar regions and the warmer, moist air of the Ferrell Cell in the mid-latitudes.
Following this trend, the Barents Sea has been characterised as being ‘Atlantified’ because of its status as an Arctic warming hot spot, although it is part of the Arctic. Climate-driven reduction in seasonal sea ice cover is faster and more extreme in the Barents Sea than in any other Arctic regions, with some models predicting it to be completely free of ice year-round by 2080.
Image: The Barents Sea is a rather shallow shelf sea in the Arctic Ocean, located off the northern coasts of Norway and Russia, with an average depth of 230 metres (750 ft). Image credit: Wikimedia maps.
As Arctic sea ice declines, considerable changes are expected in the way the seafloor (benthic) and open waters (pelagic) interact. Normally, life on the seafloor relies on a steady supply of organic matter sinking down from above. But with less ice, the amount, timing, and quality of that food supply is likely to shift, affecting the benthic ecosystem. Areas once protected by ice could also become more exposed to human impacts like trawling.
These changes will disrupt the natural movement of matter between the seabed and the water column – a key process for cycling carbon and nutrients. This movement, referred to as benthic–pelagic exchange, depends on physical mixing, animal activity, and other drivers, and it can work in two directions: particles and dissolved matter moving down – or being stirred back up.
This study is part of the Changing Arctic Ocean Seafloor project (ChAOS), which focused on the Barents Sea – a shallow shelf sea in the Artic Ocean – sampling a North-South transect across the Barents Sea for over two years with differing sea ice cover conditions, recording biological, biogeochemical, hydrographic, geophysical, and oceanographic data. The work carried out by PML’s Dr Saskia Rühl reveals that as the Polar Front retreats and ice cover diminishes, the direction of key benthic-pelagic fluxes is likely to reverse.
Image: PML’s Dr Saskia Rühl retrieving a sub-core to use for her resuspension experiments in the on-board lab.
Through in-situ sampling and experiments, they examined how matter moves between the seabed and water under different ice conditions. The study found that in the southern Barents Sea (which has more of an Atlantic influence), dissolved substances mostly move down into the seafloor while particles move up into the water. But in the northern Barents Sea (more of an Arctic influence), the opposite happens: dissolved substances tend to move up and particles down. This makes the northern area more of a ‘depositional zone’, where material settles and supports productivity near the sediment surface.
Images below: a selection of pictures from the CHAOS (Changing Arctic Ocean Seafloor) cruises onboard the RRS James Clark Ross (JCR) which the data for this study were collected.
Image: Saskia’s lab set-up in the controlled-temperature room on the JCR
Image: Deploying the box corer to get sediment samples up from the seafloor
Their results give insight into how a warming Arctic could reshape these vital processes in the future. As the Polar Front is pushed further North, the Northern regions are likely to become more similar to today’s Southern conditions, leading to a larger area in which particles are not deposited as reliably, and seafloors are more prone to disturbances.
Lead author Dr Saskia Rühl said: “Our findings highlight the need for broad, multidisciplinary monitoring of the Arctic’s changing ecosystems. Understanding how particulate and dissolved fluxes respond to climate and human pressures is critical for predicting impacts on biodiversity, fisheries, and the Arctic’s role in storing carbon. This research provides a vital foundation for future studies and for refining ecosystem models in one of the world’s most climate-sensitive seas.”
