Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Odani, Sachika*; Uchiyama, Yusuke*; Kashima, Motohiko*; Kamidaira, Yuki; Mitarai, Satoshi*
no journal, ,
We conduct a double nested high-resolution synoptic ocean modeling using ROMS with grid spacing down to 1 km coupled with an offline Lagrangian particle tracking model. The modeled dispersal of coral spawn and larvae released from about 20 major islands and lagoons are examined to quantify connectivity using Lagrangian probability density functions (PDFs) of the Lagrangian particles among Ryukyu Islands. We introduce 145 patches with a diameter of 1km around Sekisei Lagoon between Yaeyama and Ishigaki Islands close to Taiwan to compare with an in-situ surface drifter measurement. Lagragian particles are released from the patches in spring for 2012-2015 and are tracked for the advection time of 3 weeks suitable to representing active spawning and lifespan of coral spawn and larvae. The PDF analyses suggest that the particles mostly remain near the released areas, while about 10% of the particles are entrained by the Kuroshio to travel long distance, leading to inter-island connectivity. Some of these particles are further transported northeastward, and then partially trapped by the Kuroshio Counter Current formed between the Kuroshio and Main Island to approach Okinawa Main Island. We reveal that eastward current in the south the lagoon occurred shortly after the releases suppresses the entrainment and the resultant long-distance transport.
Kamidaira, Yuki; Kawamura, Hideyuki; Kobayashi, Takuya; Uchiyama, Yusuke*; Furuno, Akiko
no journal, ,
no abstracts in English
Asami, Keishiro*; Hirano, Naoto*; Takahashi, Naoya; Watanabe, Takahiro
no journal, ,
Ferromanganese (Fe-Mn) crusts covering hard-rocks on seafloor and Fe-Mn nodules enwrapping rock fragment unclear on sediments are known as chemical sedimentary rocks mainly composed of Fe and Mn (ohydro)oxides in submarine environment. Origins of those are classified into three types based on chemical composition which are hydrogenetic origin from ambient seawater, diagenetic origin from sedimentary pore water in early diagenesis, and hydrothermal origin. It is rare to show diagenetic signal in case of hydrogenetic Fe-Mn crusts because they do not occur on sediments, but hard-rocks. However, diagenetic signal was reported about high Ni, Cu and Li contents layers in hydrogenetic Fe-Mn crusts due to elemental addition by dissolution of organic matter and biogenic silica in seawater (Hein et al. 2012). Here, we report the diagenetic signal into hydrogenetic Fe-Mn crusts on peperite from petit-spot volcanoes which are monogenetic volcanoes erupted on bending oceanic plate. Their occurrence likely shows the origin from debris of Fe-Mn nodules (generally implicated in diagenetic origin) before eruption of petit-spot volcanoes.