| 英文摘要: | The seafloor is covered in a thick layer of mud called sediment. Ocean sediment accumulates over time as debris from adjacent continents, atmospheric dust, and the skeletons of microscopic marine organisms settle on the seafloor. As sediment accumulates in the oceans surrounding Antarctica, it records past environmental conditions including ice sheet behavior as the ice retreated following the last Ice Age. Scientists use a variety of chemical analyses to determine how long ago sediments were deposited on the seafloor, and are therefore able to relate ice sheet behavior to specific periods of time in the past. However, it has been challenging to determine the age of sediments around Antarctica, because the sediments often lack material that can be dated by conventional methods. In this project, researchers from the University of South Florida and the University of Washington will test newly developed methods for dating Antarctic continental margin sediments and refine the timing of ice retreat since the last Ice Age. Ultimately, accurately assessing the timing of Antarctic ice retreat from marine sediment cores will enable a better understanding of Earth's response to changing environmental conditions. This project includes training of a Ph.D. student at the University of South Florida, producing videos for educators in the state of Florida, and public outreach at the annual St. Petersburg Science Fest.
Antarctic margin sediments are difficult to accurately date because the calcium carbonate shells of marine organisms that are typically used throughout the world's oceans to date sediments are not often preserved. In this project, researchers from the University of South Florida and the University of Washington focus on two tasks: 1) separating less thermochemically-stable carbon (more likely derived from carbon with an age equal to the depositional age of the sediment) from more stable carbon (more likely eroded from the adjacent continent by glacial erosion); and 2) isolating specific organic compounds from marine diatoms, which are primary producers in the Southern Ocean. The work will use previously collected samples in sediment cores obtained from the Southern Ocean seafloor. At each depth horizon in each sediment core studied, scientists will use established radiocarbon methods to date the carbon derived from each of these new preparation techniques. This work will determine the best practices in radiocarbon dating of carbonate-poor Antarctic sediments, which will ultimately improve understanding of the factors influencing past and future Antarctic ice sheet behavior. |