Use of Marine Micropaleontology in Climate Science
This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Climate Science. Please check back later for the full article.
The understanding of past changes in climate and ocean circulation is based to a large extent on information from marine sediments. Marine deposits contain a variety of microfossils, which archive (paleo)-environmental information in their floral and faunal assemblages and geochemical compositions. Sampling campaigns in the late 19th and early 20th centuries were dedicated to the inventory of sediment types and microfossil taxa. With the initiation of various national and international programs in the second half of the 20th century, sediment cores were systematically drilled from all ocean basins; these sediment cores have since shaped our knowledge of the ocean and climate history. The stable oxygen isotope composition of foraminiferal tests from the recovered sediment cores has delivered a continuous record of the Cenozoic glaciation history. This record, impressively, has proved the effects of changes in the orbit of the Earth, described as Milankovitch cycles, on climate over tens to hundreds of thousands of years. Based on the origination and extinction patterns of marine microfossil groups, biostratigraphic schemes that are readily used for the dating of sediment successions have been established. The species composition of planktonic microfossil groups, such as planktonic foraminifera, coccolithophorids, and diatoms, is mainly related to sea-surface temperature and salinity but also to the distribution of nutrients and sea ice. Benthic microfossil groups, in particular benthic foraminifera, respond to changes in water depth, oxygen, and food availability at the sea floor and provide information on sea-level changes and bentho-pelagic coupling in the ocean. The establishment and application of transfer functions delivers quantitative environmental data, which are used for the validation of results from ocean and climate modeling experiments. The progress in analytical facilities and procedures allows for the development of new proxies based on the stable isotope and on trace element composition of calcareous and siliceous microfossils. Knowledge of the response of marine microorganisms to past climate changes at various amplitudes and pacing serves as a basis for assessing the future resilience of marine ecosystems to the anticipated global warming.