Ocean in a changing climate

Earth’s climate is undergoing rapid transformation, with the ocean playing a central role in this process. More than 90% of the excess heat generated by rising greenhouse gas concentrations is absorbed by the ocean, making it a key regulator of the global climate system. As a result, fundamental ocean properties—such as stratification, circulation patterns, and sea-ice extent—are already changing, interacting with natural modes of climate variability like El Niño–Southern Oscillation and the North Atlantic Oscillation.

Climate projections indicate continued warming, reduced ice cover, and shifts in major current systems, including the Gulf Stream. At the same time, small- to mesoscale ocean processes are increasingly recognized as critical drivers of climate dynamics. Understanding these complex interactions requires not only advanced modeling but also comprehensive observational data.

Insights into past climate conditions provide an essential context for interpreting current and future changes. Marine archives, such as sediment cores, corals, and bivalves, preserve valuable proxy data that extend far beyond instrumental records. These reconstructions reveal how ocean circulation, carbon cycling, and biogeochemical processes have shaped Earth’s climate over geological timescales. They also help identify thresholds, feedback mechanisms, and tipping points within the climate system—offering important lessons for today’s rapidly changing environment.

Despite major scientific advances, significant knowledge gaps remain. Addressing these challenges depends on sustained access to research vessels, which enable in situ observations, sample collection, and the deployment of ocean monitoring systems such as floats, drifters, and moorings. German research vessels, in particular, have contributed substantially to interdisciplinary marine research, supporting collaborations across geology, biology, biogeochemistry, and physical oceanography.

Key research priorities include:

• Advancing Climate Proxies
  Continued development and refinement of proxy methods will improve reconstructions of past ocean conditions. Expanding calibration datasets and testing new proxies—such as isotopic and microstructural indicators—are essential for accurately quantifying environmental variables like temperature, oxygen, and nutrient levels.
• Understanding Abrupt Climate Change and Ocean Circulation
  High-resolution sediment records from key ocean regions will help unravel the mechanisms behind rapid climate shifts and changes in ocean circulation. Integrating geological archives with modern observational and modeling approaches will enhance our understanding of climate variability on societally relevant timescales.
• Exploring Land–Ocean Linkages
  Marine sediments provide critical insights into how terrestrial climate processes—such as hydrological changes, vegetation shifts, and sediment transport—interact with the ocean. These linkages are particularly important for understanding large-scale climate systems that affect millions of people worldwide.
• Assessing Climate Impacts on Marine Biodiversity
  Fossil and modern biological records reveal how marine ecosystems respond to environmental change. Investigating ecosystem resilience, adaptation, and recovery under past and present climate conditions is essential for predicting the impacts of ongoing warming, acidification, and deoxygenation.
• Monitoring Changing Ocean Properties
  The ocean is becoming warmer, more acidic, and less oxygenated. Emerging phenomena such as marine heatwaves—many of which remain undetected at the surface—highlight the need for improved observational capabilities. Enhanced monitoring of ocean temperature, chemistry, and circulation is crucial for refining climate models and projections.

Overall, advancing our understanding of the ocean’s role in climate change requires sustained investment in observational infrastructure, technological innovation, and interdisciplinary research. The proposed Infrastructure Priority Program will provide a vital framework for addressing these challenges and strengthening the scientific foundation for future climate research.