Variation of dust input into the North Pacific Ocean

点击翻译按钮获取中文摘要

To investigate the impact of dust input on climate and ocean conditions, we studies the relationship between the variation of wind-driven dust input from the Eurasia continent into the North Pacific Ocean and the climate condition in this region. It has been known that many kinds of gases like carbon dioxide are exchanged vigorously between ocean and atmosphere in the North Pacific region, and that the amount of dust input into the ocean affects carbon dioxide content in the atmosphere and would lead to the global climate change. First, we established the age-depth relation for sediment cores collected from the North Pacific Ocean using paleointensity stratigraphy. In the North Pacific high temporal resolution records have been unavailable because existing dating methods such as C14 dating or oxygen isotope stratigraphy are not applicable to siliceous sediments occupying the North Pacific. We used U-channel samplers to cover the whole interval of cored sediments and measured natural re … More manent magnetizations at 2 cm intervals. The stability of natural remanent magnetization was examined using alternating field demagnetization and anhystretic remanent magnetization was used to normalize the intensity of natural remanent magnetization to detemine the paleointensity of geomagnetic field. Comparing the measured paleointesity data with well-dated paleointensity records, we could obtain the high-resolution age models on several sediment cores for the past 800 kyr. Second, dust input was estimated from the content and grain size variations of magnetic minerals. We measured magnetic hysteresis loops, magnetic moments at low temperature and thermomagnetic curves using a newly custom-made Curie balance. Two types of sediments are well distinguished from magnetic hysteresis measurements and they are responsible to variable oxidizing/reducing conditon. Based on the paleointensity stratigraphy we could obtain high-resolution temporal records of many kinds of magnetic properties and found that the variations of dust input and ocean condition in the North Pacific are well correlated to the glacial-interglacial cycle. Less