scholarly journals Deep-sea water displacement from a turbidity current induced by the Super Typhoon Hagibis

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10429
Author(s):  
Shinsuke Kawagucci ◽  
Tetsuya Miwa ◽  
Dhugal J. Lindsay ◽  
Eri Ogura ◽  
Hiroyuki Yamamoto ◽  
...  
Keyword(s):  
Deep Sea ◽  
Sea Water ◽  
Deep Ocean ◽  
Vertical Displacement ◽  
Video Camera ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Water Displacement ◽  
Suruga Bay ◽  
Super Typhoon

Turbidity currents are the main drivers behind the transportation of terrestrial sediments to the deep sea, and turbidite deposits from such currents have been widely used in geological studies. Nevertheless, the contribution of turbidity currents to vertical displacement of seawater has rarely been discussed. This is partly because until recently, deep-sea turbidity currents have rarely been observed due to their unpredictable nature, being usually triggered by meteorological or geological events such as typhoons and earthquakes. Here, we report a direct observation of a deep-sea turbidity current using the recently developed Edokko Mark 1 monitoring system deployed in 2019 at a depth of 1,370 m in Suruga Bay, central Japan. A turbidity current occurred two days after its probable cause, the Super Typhoon Hagibis (2019), passed through Suruga Bay causing devastating damage. Over aperiod of 40 hours, we observed increased turbidity with turbulent conditions confirmed by a video camera. The turbidity exhibited two sharp peaks around 3:00 and 11:00 on October 14 (Japan Standard Time). The temperature and salinity characteristics during these high turbidity events agreed with independent measurements for shallow water layers in Suruga Bay at the same time, strongly suggesting that the turbidity current caused vertical displacement in the bay’s water column by transporting warmer and shallower waters downslope of the canyon. Our results add to the previous few examples that show meteorological and geological events may have significant contributions in the transportation of shallower seawater to the deep sea. Recent technological developments pertaining to the Edokko Mark 1 and similar devices enable straightforward, long-term monitoring of the deep-seafloor and will contribute to the understanding of similar spontaneous events in the deep ocean.

scholarly journals Application of the adjoint approach to optimise the initial conditions of a turbidity current

2016 ◽  
Author(s):  
Samuel D. Parkinson ◽  
Simon W. Funke ◽  
Jon Hill ◽  
Matthew D. Piggott ◽  
Peter A. Allison
Keyword(s):  
Initial Conditions ◽  
Current Model ◽  
Deep Ocean ◽  
Turbidity Current ◽  
Significant Advance ◽  
Turbidity Currents ◽  
General Behaviour ◽  
Depositional Processes ◽  
Sediment Deposits ◽  
Adjoint Approach

Abstract. Turbidity currents are one of the main drivers for sediment transport from the continental shelf to the deep ocean. The resulting sediment deposits can reach hundreds of kilometres into the ocean. Computer models that simulate turbidity currents and the resulting sediment deposit can help to understand their general behaviour. However, in order to recreate real-world scenarios, the challenge is to find the turbidity current parameters that reproduce the observations of sediment deposits. This paper demonstrates a solution to the inverse sediment transportation problem: for a known sedimentary deposit, the developed model reconstructs details about the turbidity current that produced these deposits. The reconstruction is constrained here by a shallow water sediment-laden density current model, which is discretised by the finite element method and an adaptive time-stepping scheme. The model is differentiated using the adjoint approach and an efficient gradient-based optimisation method is applied to identify turbidity parameters which minimise the misfit between modelled and observed field sediment deposits. The capabilities of this approach are demonstrated using measurements taken in the Miocene-age Marnoso Arenacea Formation (Italy). We find that whilst the model cannot match the deposit exactly due to limitations in the physical processes simulated, it provides valuable insights into the depositional processes and represents a significant advance in our toolset for interpreting turbidity current deposits.

Disposal in the deep sea: analogue of nature or faux ami?

2003 ◽  
Vol 30 (1) ◽  
pp. 26-39 ◽  
Author(s):  
Paul A. Tyler
Keyword(s):  
Carbon Dioxide ◽  
Radioactive Waste ◽  
Deep Sea ◽  
Hydrothermal Vents ◽  
Natural Radionuclides ◽  
Deep Ocean ◽  
Turbidity Currents ◽  
Chemical Contamination ◽  
Seabed Sediment ◽  
Dredge Spoil

The deep sea is the world's largest ecosystem by volume and is assumed to have a high assimilative capacity. Natural events, such as the sinking of surface plant and animal material to the seabed, sediment slides, benthic storms and hydrothermal vents can contribute vast amounts of material, both organic and inorganic, to the deep ocean. In the past the deep sea has been used as a repository for sewage, dredge spoil and radioactive waste. In addition, there has been interest in the disposal of large man-made objects and, more recently, the disposal of industrially-produced carbon dioxide. Some of the materials disposed of in the deep sea may have natural analogues. This review examines natural processes in the deep sea including the vertical flux of organic material, turbidity currents and benthic storms, natural gas emissions, hydrothermal vents, natural radionuclides and rocky substrata, and compares them with anthropogenic input including sewage disposal, dredge spoil, carbon dioxide disposal, chemical contamination and the disposal of radioactive waste, wrecks and rigs. The comparison shows what are true analogues and what are false friends. Knowledge of the deep sea is fragmentary and much more needs to be known about this large, biologically-diverse system before any further consideration is given to its use in the disposal of waste.

scholarly journals Biodegradation of several fibers submerged in deep sea water and isolation of biodegradable plastic degrading bacteria from deep ocean water

2009 ◽  
Vol 75 (6) ◽  
pp. 1011-1018 ◽  
Author(s):  
TAKAYOSHI SEKIGUCHI ◽  
AKIRA EBISUI ◽  
KOJI NOMURA ◽  
TOSHIHIRO WATANABE ◽  
MAKIKO ENOKI ◽  
...  
Keyword(s):  
Deep Sea ◽  
Sea Water ◽  
Deep Ocean ◽  
Biodegradable Plastic ◽  
Ocean Water ◽  
Deep Sea Water ◽  
Deep Ocean Water ◽  
Degrading Bacteria

scholarly journals HYDRODYNAMIC MECHANISM OF TURBIDITY CURRENTS IN ESTUARY STRATIFICATIONS

2018 ◽  
pp. 80
Author(s):  
Zhiguo He ◽  
Liang Zhao ◽  
Ching-Hao Yu
Keyword(s):  
Internal Waves ◽  
Sea Water ◽  
Initial Period ◽  
Gravity Current ◽  
Turbidity Current ◽  
Numerical Results ◽  
Front Velocity ◽  
Evolution Process ◽  
Turbidity Currents ◽  
Entrainment Ratio

Water stratification commonly exists in nature, such as thermocline in lakes and oceans and halocline in estuaries and oceans (He et al. 2017). Turbidity currents in estuary often encounter stratified sea water, which may significantly influence their propagation and deposition. This study presents high-resolution numerical simulations of lock-exchange gravity and turbidity currents in linear stratifications on a flat bed. Laboratory experiments are conducted to validate the numerical model and good agreements between numerical results and measurements are found. The evolution process, front velocity, internal wave, and entrainment ratio are analyzed based on the numerical results. For a gravity current in a strong stratification, its front velocity can be maintained as a near constant state for a long time after an initial acceleration period because of interactions between the current and internal waves. However, sedimentation of suspended particles due to the damping effect of ambient stratification on turbulence makes a turbidity current quickly lose its structure so the maintaining effect of the internal waves on its front velocity is quite weak. During the evolution process of a turbidity current, the ambient stratification is found to damp the turbulent structures, and front velocity. Stratification can also decrease the entrainment ratios between a gravity current and ambient water after the initial period, but it has an insignificant influence on the entrainment ratios of a turbidity current. This study provides a better understanding of gravity and turbidity currents in estuary stratifications.

scholarly journals Near-Field Analysis of Turbidity Flows Generated by Polymetallic Nodule Mining Tools

Mining ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 251-278
Author(s):  
Mohamed Elerian ◽  
Said Alhaddad ◽  
Rudy Helmons ◽  
Cees van Rhee
Keyword(s):  
Deep Sea ◽  
Raw Materials ◽  
Near Field ◽  
Turbidity Current ◽  
Sediment Flux ◽  
Field Analysis ◽  
Turbidity Currents ◽  
Water Mixture ◽  
Polymetallic Nodule ◽  
Nodule Mining

The interest in polymetallic nodule mining has considerably increased in the last few decades. This has been largely driven by population growth and the need to move towards a green future, which requires strategic raw materials. Deep-Sea Mining (DSM) is a potential source of such key materials. While harvesting the ore from the deep sea by a Polymetallic Nodule Mining Tool (PNMT), some bed sediment is unavoidably collected. Within the PNMT, the ore is separated from the sediment, and the remaining sediment–water mixture is discharged behind the PNMT, forming an environmental concern. This paper begins with surveying the state-of-the-art knowledge of the evolution of the discharge from a PNMT, in which the discharge characteristics and generation of turbidity currents are discussed. Moreover, the existing water entrainment theories and coefficients are analyzed. It is shown how plumes and jets can be classified using the flux balance approach. Following that, the models of Lee et al. (2013) and Parker et al. (1986) are combined and utilized to study the evolution of both the generated sediment plume and the subsequent turbidity current. The results showed that a smaller sediment flux at the impingement point, where the plume is transformed into a turbidity current, results in a shorter run-out distance of the turbidity current, consequently being more favorable from an environmental point of view.

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