Arata Kioka

The giant 2011 Tohoku-oki earthquake has been inferred to remobilise fine-grained, young surface sediment enriched in organic matter from the slope into the >7 km deep Japan Trench. Yet, this hypothesis and assessment of its significance for the carbon cycle has been hindered by limited data density and resolution in the hadal zone. Here we combine new high-resolution bathymetry data with sub-bottom profiler images and sediment cores taken during 2012-2016 in order to map for the first time the

Hadal trenches are the deepest places on Earth and are important foci for natural carbon sequestration. Much of the sedimentary sequences that accumulate within hadal trenches have been linked to widespread slope sediment remobilisation events, triggered by subduction zone earthquakes. Therefore, hadal trench deposits may provide valuable insights into the hazards posed by large earthquakes and their implications for the carbon cycle. Despite this strong societal relevance, no studies to date ha

Abstract Recent years of increasing air temperature in the Arctic have led to a significant increase in the rate of retreat of permafrost coast, which has threatened livelihoods and infrastructure in these areas. The Kara Sea hosts more than 25% of the total Arctic coastline. However, little is known about how coastal erosion in the Kara Sea may have changed through time, and the climatic and environmental drivers remain unclear. Here we study coastal dynamics along a 4‐km stretch of permafrost

The role of mud volcanism on subsurface fluid migration and material cycling has long been debated. Here we compile the heights and radii of offshore mud volcanoes and estimate a mean volume of episodic massive mud eruptions based on previous studies into granular flows. The volume is estimated as a function of the ratio of height to basal radius of the mud volcano's body under reasonable assumptions of the sizes of the mud conduit. Nearly all known offshore mud volcanoes are found to be polygen

Flow-accelerated corrosion can be very destructive, leading to rapid loss of component efficiency and eventual failure of the system; however, finding inexpensive, effective, and chemically benign inhibitors is still challenging. This paper studied for the first time the use of nanobubbles/ultrafine bubbles as a “green” functional nanostructured material for inhibiting flow-accelerated corrosion under the impingement of a turbulent liquid jet. We examined the corrosion inhibition of the copper s

Abstract Mud volcanoes are among the largest geological sources releasing methane gas. Numerous studies have revealed their origins and compositions released from submarine mud volcanoes. However, quantification of the amount of gas inside submarine mud volcanoes has been challenging due to the difficulty of in situ measurements, which has hampered better evaluation for their contribution to the global methane budget. Here we provide a coupled geochemical and geophysical model that bridges bulk

The calcium carbonate (CaCO3) scale generated in water pipes and heat exchangers causes serious problems such as pipe blockage and corrosion. This study investigates the effect of the 4-to-10 μm-long and 350-to-700 nm centering-nucleus-wide ZnO tetrapod-like nanomaterials and polydimethylsiloxane composite (t-ZnO/PDMS) on deposition and polymorphism of CaCO3 crystals on the stainless-steel substrate. The results showed that the t-ZnO/PDMS coating inhibited CaCO3 depositions and represented an ex

泥火山は表層下の堆積物循環，流体移動および炭素循環と強く関わっており，表層現象の中で重要な地質現象の一つである．しかしながら，普通のマグマ性火山とは異なり，泥火山に関する知見は乏しい．本論では，海底に発達する泥火山に着目し，海底泥火山の発達分布と山体地形について地質学的に簡単な概説を行った．まず，海底泥火山の分布を見ると，亜極域のプレート沈み込み縁辺を除いたほとんどの沈み込み縁辺で泥火山が発達していることが確認できた．そして，海底泥火山の山体形態に注目すると，山体形態の特徴が沈み込み縁辺の特性で分類できることが示唆された．本論で概観した山体分布や形態といった基礎研究は，今後，泥火山ダイナミクス全体の理解だけでなく，表層下物質循環の包括的理解にもつながることが期待される．