Marine Geology and Paleontology
The development of a fundamental understanding of Earth’s history and its future evolution is among the major concerns of present day society as human influence on the climate system expands. One of the major research activities of our section is to reconstruct and understand the mechanisms and impacts of past global environmental variability related to natural driving forces of climate change. We attempt to achieve this by interpreting chemical signatures of biologic, oceanographic and climatic processes that are preserved in the marine sediment record.
The marine sediments accumulated on the ocean floor over millions of years are a memory map of changes in oceanic and atmospheric circulation, biogeochemical cycles as well as climate variability, and provide the most complete and continuous archive for paleoclimate research. The use of research vessels equipped with echosounding systems and advanced coring technologies allows the marine geologists to compile data about the composition, shape and structure of sediment archives and the processes that have been at work throughout the sediment’s depositional history. The analysis of particular marine sediment properties (“proxies”) offers the potential to reconstruct an array of parameters that responded to or modulated changes in the climate system. These include oceanic changes in temperature, biogenic productivity, chemistry, circulation and sea level, variations in global ice volume, latitudinal and regional shifts of climate zones as well as volcanic eruptions and other disastrous events like submarine landslides and asteroid impacts. The sediment sequences recovered from the ocean floor allow geologists to study the climate mechanisms and processes that operated on different but compatible timescales, ranging from tectonic (millions of years) over orbital (tens to hundreds of thousands of years) to millennial and decadal.
The benthic oxygen isotope curve reflects the global climate evolution of the last 5 million years, as it is a measure of changes in global ice volume and deep-water temperature. The Pliocene warm period from ∼5 to ∼3 million years ago is believed to hold clues for assessing future climate change. This time interval, with atmospheric CO2-concentrations close to modern ones, was significantly warmer than today. High-latitude sea surface temperatures were up to 7°C higher, the modern Northern Hemisphere ice cap over Greenland was absent, and the sea level was about 30 m higher than today. Hence, it represents a possible future climate scenario predicted by numerical models. The long-term increase in oxygen isotope values from ∼3–2.5 million years ago marks the development of a permanent Northern Hemisphere ice cap with varying size. The last 3 million years are characterized by alternating glacial and interglacial climate stages, while glacial ice sheets reached their largest size during the last 700.000 years.
