This research provides the first Pliocene paleo-oceanographic observations from the Bering Sea and supports the objectives of IODP expedition 323 for understanding the associated factors influencing climate change during the Pliocene and Pleistocene, including a warm period of the early Pliocene, when pCO2 levels were similar to today¡¦s levels. The flow of water masses between the Bering Sea and the Arctic and Pacific oceans, changes in Arctic ice volume, and whether dense intermediate waters formed in the Pacific during this time will be investigated as some of the possible triggers of past climate change. The high resolution sediment records obtained from this cruise, with relatively large-amplitude signals, provide a unique opportunity to understand how insulation changes in the upper atmosphere propagate through the climate system and to further test if the orbital cycles of climate change primarily operate on 23ky versus 40 ky timescales. This study utilizes K % logging data from the cruise with paleomagnetic, sedimentological (eg., grain size analysis) and paleontological (eg., analysis of microfossil assemblages; d18O and d13C measurements of benthic and planktonic forams) measurements from the drill cores. The information expected from this study is critical for understanding the fundamental drivers and feedbacks between ice sheets, oceanic and atmospheric circulation and the global carbon cycle.
Broader Impacts: This project significantly advances large investments previously made in an important IODP expedition. The data derived from this investigation can provide important information for paleoclimate/ocean models, and is relevant towards projections of future climate under IPCC AR4 scenarios. The project includes a team of early and mid-career scientists, and includes international collaborations with other scientists of the IODP community. Support is also provided for undergraduate and graduate education, and for public outreach and education.
," were to examine the mechanisms and processes responsible for climate change through the last million years by analyzing deep sea sediments from Bering Sea collected during the IODP Expedition 323. Key questions include: (1) What is the response of the Bering Sea to the changes in Earth's orbit and the resulting changes in the distribution and intensity of solar insolation? (2) What is the expression of rapid climate changes on thousand-year timescales in the Bering Sea? With a team of 20 undergraduate students at Williams College over the 3 years of the project, we made measurements of oxygen isotopes in benthic foraminifera, protists that live on the seafloor and record the chemistry of seawater in their shells. We matched the pattern in oxygen isotope changes down the sediment core U1345 and U1339 with a global average record in order to determine the age of the sediments from two of the seven sites drilled during Exp 323. U1345 covers 500,000 y of sediment deposition, and U1339 covers 1,000,000 y. These age models will be used by all the other investigators working at these sites. We used the same oxygen isotope data to study the vertical structure of the water column for the last 500,000 years and found that it appears that the ocean circulation in the Bering Sea was systematically different during ice ages than during interglacials, the warm periods between ice ages. These new record show that the ocean circulation pattern observed for the last ice age seems to be a feature of all the glaciations of the last half million years. We also did preliminary studies on rapid climate variability during several interesting time periods from the past: (1) the last glacial period, when there are millennial-scale climate and ocean circulation changes that are well-documents in the Atlantic, but poorly understood in the Pacific, (2) the penultimate glacial period, where there are also millennail-scale climate changes that appear to have a different character than the events during the last glaciation and whose origin and global impact is little understood, (3) the end of the last ice age, when there were large and rapid swings between warm and cold climate states, and (4) a glacial termination 424,000 y ago, where the configuration of earth's orbit was the most similar to the last deglaciation. The results of these investigations will be the basis of future research on these sediment cores. The undergraduate students who participated in this project included 16 women and 9 underrepesented minorities. One student completed a senior honors thesis, and two others completed independent research projects. One student has since completed an MS in Environment Science, and two are enrolled in PhD programs in Geology. The research assistants got exposure to the methods and scientific problems in Quaternary Pacific paleoceanography. The research students designed projects, prepared samples, and traveled to the co-PI’s research labs to collect data, interact with the collaborators and their research groups. This gave the students a strong foundation in the nature of scientific inquiry on past climate change. We hope these experiences will inspire the students to consider pursuing careers in scientific research.
