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Fossil foraminifer in marine sediment reveals sea surface water temperature 800,000 years ago

January 30, 2020

The climate change record could reveal future climate changes. Scientists gather information about the past environment from proxies such as deep-sea sediments and Antarctic ice cores. These samples are scarce in number because of the limited sampling locations and the high financial and temporal costs. Therefore, paleoenvironmental data have been obtained for a restricted number of places and periods. A collaborative research team from the National Institute of Polar Research (NIPR) and Ibaraki University focused on the usefulness of fossil foraminifers obtained from marine sediment uplifted on to land instead of sediment on the seafloor.

"Current global warming is considered to be anthropogenic, so we need to evaluate its effectiveness," said Dr. Yuki Haneda, NIPR scientist and the first author of a report in Earth and Planetary Science Letters published online on November 18.

"To assess anthropogenic effects, it is necessary to compare the current climate with that of the past, which has comparable parameters regarding the Earth's orbital path and axis tilt--the factors of climate change--but no anthropogenic effects. The current interglacial period, which began 10,000 years ago, is similar to the warm period "MIS19", which lasted from approximately 790,000 to 760,000 years ago. We suggested analyzing marine foraminifers to elucidate changes in the marine environment during this period''

The researchers collected four species of fossil foraminifers with different habitat depths from the Chiba composite section containing the MIS19 layer and conducted oxygen isotope analyses. Former studies have shown that low oxygen isotope values in fossil foraminifers correspond with higher water temperatures and vice versa. The analysis reveals that, in addition to the glacial-interglacial cycle that recurs on a tens of thousands of year time scale, extreme changes in water temperature--equivalent to approximately 7 ° C--are repeated every few thousand years.

A close comparison of the results of research on the North Atlantic deep-sea sediment reveals that this temperature change is likely to have occurred due to iceberg runoff and the resulting decline of deep-water circulation.

"Surprisingly, changes in the North Atlantic caused dramatic water temperature fluctuations in the remote Northwest Pacific" said Dr. Haneda. "We believe that the fossils collected from the ground outcrop are a tracer that complements the data reported from deep-sea sediments. The Chiba composite section is the Global Boundary Stratotype Section and Point (GSSP) of the Lower-Middle Pleistocene boundary, and offers considerable understanding of global environmental change during that period.

We want to improve our understanding of climate change during MIS19 to predict future climate change more precisely. "
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About National Institute of Polar Research (NIPR)

The NIPR engages in comprehensive research via observation stations in Arctic and Antarctica. As a member of the Research Organization of Information and Systems (ROIS), the NIPR provides researchers throughout Japan with infrastructure support for Arctic and Antarctic observations, plans and implements Japan's Antarctic observation projects, and conducts Arctic researches of various scientific fields such as the atmosphere, ice sheets, the ecosystem, the upper atmosphere, the aurora and the Earth's magnetic field. In addition to the research projects, the NIPR also organizes the Japanese Antarctic Research Expedition and manages samples and data obtained during such expeditions and projects. As a core institution in researches of the polar regions, the NIPR also offers graduate students with a global perspective on originality through its doctoral program. For more information about the NIPR, please visit: https://www.nipr.ac.jp/english/

Research Organization of Information and Systems

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