Ocean Circulation and Climate Dynamics

Past Ocean circulation

Cretaceous marls from Pueblo State Park, Colorado, USA. These layers of rock are between 94.5 to 95.5 million years old. (Photo: Sascha Flögel)

The global thermohaline ocean circulation is responsible for the distribution of warmth and oxygen between the atmosphere, the surface ocean and the deep ocean. The ocean currents are also responsible for the dispersal of nutrients and are consequently an essential driver of biogeochemical cycles. An exact understanding of the circulation in the past is therefore a basic prerequisite to understanding the entire ocean-atmosphere-climate system.

Changes in ocean circulation and water mass mixing in the geological past are recorded by proxies in ocean sediments and in the calcitic skeletons of marine organisms. These archives show that changes in the ocean have affected climate and living conditions on land for millions of years.

The climate of the earth was considerably warmer than today for long periods of the geological past. The configuration of the continents was different, ocean currents followed other pathways and deep water formed in different regions from today. A global cooling began around 50 million years ago, continuing into the pronounced glacial-interglacial cycles during the Quaternary that were also accompanied by large changes in ocean circulation. Although the past is not a direct analogue for future changes in climate, time-series that reach back far into the geological past are important for understanding the natural variability in the oceans.

Sediment core consisting of clay-rich calcareous ooze from the Florida Straits, near the Bahamas. The sediments in the core go back to 80,000 years before present. (Photo: Joachim Schönfeld)

Instrumental measurements only go back approximately 100 years and describe short-term seasonal to decadal fluctuations that were already influenced by the early stages of man-made global warming. For this reason, we investigate paleoceanographic time-series with a time-resolution from thousands of years to a few months and use these, together with published climate scenarios, to capture the complete spectrum of natural interconnections.

 

MOW Reconstruction
Arctic-Atlantic Exchange
Hf-Nd Isotopes in the Arctic Ocean
Pliocene Circulation in the Atlantic
Circulation in the Cretaceous
Bering See
Water mass mixing in the South Pacific (SOPATRA)
Indonesian Throughflow
OPOKA – Surface in intermediate water hydrography, planktonic and benthic biota in the Caribbean – climatic, biological and geological coupling
ECHO - Intermediate water mass history at a cold-water coral habitat in the North Atlantic
The closure of the Central American Seaway
Hf-Nd Isotopes in the Atlantic Sector of the Southern Ocean