The ocean is constantly changing in response to climate change, with shifts in temperature, circulation, oxygen levels, nutrient availability, and carbon cycling affecting marine ecosystems worldwide. Understanding how these changes will develop over the coming decades requires models that can capture the complexity of ocean processes, from large-scale circulation patterns to the smaller-scale features that drive ecosystem functioning.

High-resolution ocean modelling provides a powerful way to explore how climate change may alter the physical and biological processes that support ocean food webs. The AWI-CM3 Earth System Model provides high-resolution climate projections, while the FESOM2-REcoM3 physical-biogeochemical ocean model simulates changes in ocean circulation, temperature, nutrients, oxygen, and carbon cycling at an eddy-resolving scale. Unlike traditional climate models, which often operate at scales too broad to represent many important ocean features, these advanced models can capture the movement and interaction of smaller-scale processes that strongly influence marine ecosystems.

A key focus is the role of ocean eddies — large rotating features that form within ocean currents. Similar to weather systems in the atmosphere, eddies transport heat, carbon, oxygen, and nutrients across the ocean. They influence where biological productivity occurs, shape the movement of marine organisms, and help connect different parts of the ocean system. Because many ocean regions are dominated by strong eddy activity, accurately representing these features within the FESOM2-REcoM3 model is essential for predicting how marine ecosystems may respond to future climate change.

Climate change also affects the biological and chemical processes that regulate ocean productivity. These biogeochemical (BGC) processes describe how essential elements, including carbon and nutrients, move through the ocean and are transformed by marine life. The REcoM3 biogeochemical component of the model simulates these processes, helping researchers understand how climate change may influence marine productivity, the biological carbon pump, and the transfer of energy through ocean food webs.

Using the coupled AWI-CM3 and FESOM2-REcoM3 modelling framework, OceanSOS will simulate both historical and future ocean conditions from 1950 to 2100. These simulations provide projections of how physical and biogeochemical conditions may change over short-, medium-, and long-term timescales, helping identify where climate-driven changes could increase risks to ecosystem functioning across the OceanSOS study regions.

To better understand the connections between the deep ocean and surface waters, OceanSOS combines these large-scale simulations with the fine-scale regional ocean model CROCO (Coastal and Regional Ocean COmmunity model). CROCO resolves ocean processes at much finer spatial scales, allowing researchers to investigate how currents interact with complex underwater landscapes, such as seamounts and ridges, to influence bentho-pelagic coupling—the exchange of energy, nutrients, organisms, and carbon between the seafloor and the open ocean.

Outputs from CROCO are then used to drive a reactive-transport model that simulates the movement and transformation of suspended particulate organic carbon (POC). Together, these models improve estimates of how carbon moves through the ocean, how efficiently it is transferred to the deep sea, and how climate change may alter these pathways over time.

By combining global climate projections from AWI-CM3, basin-scale ocean simulations from FESOM2-REcoM3, and fine-scale regional modelling with CROCO and reactive-transport models, OceanSOS will provide a detailed picture of how climate change interacts with other emerging pressures on ocean ecosystems. These modelling tools will underpin assessments of future ecosystem risks, improve projections of ocean food webs, and provide the scientific evidence needed to support more resilient ocean management.

OceanSOS’ work on physical oceanography and climate change is led by Dr. Qiang Wang at the Climate Dynamics section at the Alfred-Wegener-Institut, supported by Dr. Christian Mohn at Aarhus Universitet.