Eutrophication leads to the formation of a sulfide-rich deep-water layer in Lake Sevan, Armenia

2021 ◽  
Vol 57 (5) ◽  
pp. 535-552
Author(s):  
Khoren Avetisyan ◽  
Natella Mirzoyan ◽  
Rayford B. Payne ◽  
Vardan Hayrapetyan ◽  
Alexey Kamyshny Jr.
Keyword(s):  
Deep Water ◽  
Water Layer ◽  
Lake Sevan ◽  
Deep Water Layer

scholarly journals Oxygen export to the deep ocean following Labrador Sea Water formation

2021 ◽  
Author(s):  
Jannes Koelling ◽  
Dariia Atamanchuk ◽  
Johannes Karstensen ◽  
Patricia Handmann ◽  
Douglas W. R. Wallace
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
Sea Water ◽  
Deep Ocean ◽  
Water Layer ◽  
Labrador Sea ◽  
Boundary Current ◽  
The North ◽  
Deep Water Layer

Abstract. The Labrador Sea in the North Atlantic Ocean is one of the few regions globally where oxygen from the atmosphere can reach the deep ocean directly. This is the result of wintertime convection, which homogenizes the water column to a depth of up to 2000 m, and brings deep water undersaturated in oxygen into contact with the atmosphere. In this study, we analyze how the intense oxygen uptake during Labrador Sea Water (LSW) formation affects the properties of the outflowing deep western boundary current, which ultimately feeds the upper part of the North Atlantic Deep Water layer in much of the Atlantic Ocean. Seasonal cycles of oxygen concentration, temperature, and salinity from a two-year time series collected by sensors moored at 600 m nominal depth in the outflowing boundary current at 53° N show that LSW is primarily exported in the months following the onset of convection, from March to August. During the rest of the year, properties of the outflow resemble those of Irminger Water, which enters the basin with the boundary current from the Irminger Sea. The input of newly ventilated LSW increases the oxygen concentration from 298 μmol L−1 in January to a maximum of 306 μmol L−1 in April. As a result of this LSW input, 1.57 × 1012 mol year−1 of oxygen are added to the outflowing boundary current, mostly during summer, equivalent to 49 % of the wintertime uptake from the atmosphere in the interior of the basin. The export of oxygen from the subpolar gyre associated with this direct southward pathway of LSW is estimated to supply about 71 % of the oxygen consumed annually in the upper North Atlantic Deep Water layer in the Atlantic Ocean between the equator and 50° N. Our results show that the formation of LSW is important for replenishing oxygen to the deep oceans, meaning that possible changes in its formation rate and ventilation due to climate change could have wide-reaching impacts on marine life.

Film spreading from a miscible drop on a deep liquid layer

2017 ◽  
Vol 829 ◽  
pp. 304-327 ◽  
Author(s):  
Raj Dandekar ◽  
Anurag Pant ◽  
Baburaj A. Puthenveettil
Keyword(s):  
Surface Tension ◽  
Water Layer ◽  
Reynolds Numbers ◽  
Capillary Waves ◽  
Water Mixture ◽  
Inertial Forces ◽  
Viscous Forces ◽  
Dimensionless Velocity ◽  
Deep Water Layer ◽  
Film Spreading

We study the spreading of a film from ethanol–water droplets of radii $0.9~\text{mm}<r_{d}<1.1~\text{mm}$ on the surface of a deep water layer for various concentrations of ethanol in the drop. Since the drop is lighter ($\unicode[STIX]{x1D709}=\unicode[STIX]{x1D70C}_{l}/\unicode[STIX]{x1D70C}_{d}>1.03$), it stays at the surface of the water layer during the spreading of the film from the drop; the film is more viscous than the underlying water layer since $\unicode[STIX]{x1D712}=\unicode[STIX]{x1D707}_{l}/\unicode[STIX]{x1D707}_{d}>0.38$. Inertial forces are not dominant in the spreading since the Reynolds numbers based on the film thickness $h_{f}$ are in the range $0.02<Re_{f}<1.4$. The spreading is surface-tension-driven since the film capillary numbers are in the range $0.0005<Ca_{f}<0.0069$ and the drop Bond numbers are in the range $0.19<Bo_{d}<0.56$. We observe that, when the drop is brought in contact with the water surface, capillary waves propagate from the point of contact, followed by a radially expanding, thin circular film of ethanol–water mixture. The film develops instabilities at some radius to form outward-moving fingers at its periphery while it is still expanding, till the expansion stops at a larger radius. The film then retracts, during which time the remaining major part of the drop, which stays at the centre of the expanding film, thins and develops holes and eventually mixes completely with water. The radius of the expanding front of the film scales as $r_{f}\sim t^{1/4}$ and shows a dependence on the concentration of ethanol in the drop as well as on $r_{d}$, and is independent of the layer height $h_{l}$. Using a balance of surface tension and viscous forces within the film, along with a model for the fraction of the drop that forms the thin film, we obtain an expression for the dimensionless film radius $r_{f}^{\ast }=r_{f}/r_{d}$, in the form $fr_{f}^{\ast }={t_{\unicode[STIX]{x1D707}d}^{\ast }}^{1/4}$, where $t_{\unicode[STIX]{x1D707}d}^{\ast }=t/t_{\unicode[STIX]{x1D707}d}$, with the time scale $t_{\unicode[STIX]{x1D707}d}=\unicode[STIX]{x1D707}_{d}r_{d}/\unicode[STIX]{x0394}\unicode[STIX]{x1D70E}$ and $f$ is a function of $Bo_{d}$. Similarly, we show that the dimensionless velocity of film spreading, $Ca_{d}=u_{f}\unicode[STIX]{x1D707}_{d}/\unicode[STIX]{x0394}\unicode[STIX]{x1D70E}$, scales as $4f^{4}Ca_{d}={r_{f}^{\ast }}^{-3}$.

Dynamics of Deep Recirculation Cells Offshore of the Deep Western Boundary Current in the Subtropical North Atlantic (15°–30°N)

2021 ◽  
Vol 51 (1) ◽  
pp. 131-145
Author(s):  
Tiago Carrilho Biló ◽  
William E Johns ◽  
Jian Zhao
Keyword(s):  
North Atlantic ◽  
Primary Source ◽  
Water Layer ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Study Region ◽  
Deep Western Boundary Current ◽  
Deep Water Layer ◽  
Circulation Patterns

AbstractThe dynamics of the deep recirculation offshore of the deep western boundary current (DWBC) between 15° and 30°N within the upper North Atlantic Deep Water layer (1000 ≤ z ≤ 3000 m) is investigated with two different eddy-resolving numerical simulations. Despite some differences in the recirculation cells, our assessment of the modeled deep isopycnal circulation patterns (36.77 ≤ σ2 ≤ 37.06 kg m−3) shows that both simulations predict the DWBC flowing southward along the continental slope, while the so-called Abaco Gyre and two additional cyclonic cells recirculate waters northward in the interior. These cells are a few degrees wide, located along the DWBC path, and characterized by potential vorticity (PV) changes occurring along their mean streamlines. The analysis of the mean PV budget reveals that these changes result from the action of eddy forcing that tends to erode the PV horizontal gradients. The lack of a major upper-ocean boundary current within the study region, and the fact that the strongest eddy forcing is constrained within a few hundreds of kilometers of the western boundary, suggest that the DWBC is the primary source of eddy forcing. Finally, the eddies responsible for forcing the recirculation have dominant time scales between 100 and 300 days, which correspond to the primary observed variability scales of the DWBC transport at 26.5°N.

Weak quadratic interactions of two-dimensional waves

1971 ◽  
Vol 50 (1) ◽  
pp. 107-132 ◽  
Author(s):  
Young Yuel Kim ◽  
Thomas J. Hanratty
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Wave Train ◽  
Water Layer ◽  
Rate Of Change ◽  
Two Dimensional ◽  
Low Frequencies ◽  
Resonant Interactions ◽  
Water Layers ◽  
Phase Angles

This paper reports on weak quadratic interactions which can occur with two-dimensional waves on shallow water layers and in the capillary-gravity range on deep water layers. It supplies experimental support of theoretical predictions for resonant interactions, but, perhaps of more significance, it explores in detail interactions which occur under conditions near resonance.Waves of approximately sinusoidal form are introduced on the surface of water in a long rectangular tank. For deep water a rapid distortion in the sinusoidal wave and sometimes additional crests are observed because of energy exchange among the first, second and third harmonics at frequencies where both surface tension and gravity are important (7·5–13 c/s). An even greater exchange of energy can be observed on shallow water layers at low frequencies. For example, a wave train with seven secondary crests can be observed when the wave maker is operated at 3·04 c/s in a water layer of 0·65 cm.Measured amplitudes and phase angles of the Fourier components of the wave train are described by a system of equations using only quadratic interactions among participating harmonics. The exchange of energy among Fourier components under certain conditions is explained in terms of the rate of change of relative phase angles of the different harmonics.

scholarly journals Preconditioning and Formation of Maud Rise Polynyas in a High-Resolution Earth System Model

2018 ◽  
Vol 31 (23) ◽  
pp. 9659-9678 ◽  
Author(s):  
Prajvala Kurtakoti ◽  
Milena Veneziani ◽  
Achim Stössel ◽  
Wilbert Weijer
Keyword(s):  
High Resolution ◽  
Deep Convection ◽  
Water Layer ◽  
Earth System Model ◽  
Weddell Sea ◽  
System Model ◽  
Earth System ◽  
Deep Water Layer ◽  
Crucial Difference ◽  
Maud Rise

Open-ocean polynyas (OOPs) in the Southern Ocean are ice-free areas within the winter ice pack that are associated with deep convection, potentially contributing to the formation of Antarctic Bottom Water. To enhance the credibility of Earth system models (ESMs), their ability to simulate OOPs realistically is thus crucial. Here we investigate OOPs that emerge intermittently in a high-resolution (HR) preindustrial simulation with the Energy Exascale Earth System Model, version 0.1 (E3SMv0), an offspring of the Community Earth System Model (CESM). While low-resolution (LR) simulations with E3SMv0 show no signs of OOP formation, the preindustrial E3SMv0-HR simulation produces both large Weddell Sea polynyas (WSPs) as well as small Maud Rise polynyas (MRPs). The latter are associated with a prominent seamount in the eastern Weddell Sea, and their preconditioning and formation is the focus of this study. The steep flanks of the rugged topography in this region are in E3SMv0-HR sufficiently well resolved for the impinging flow to produce pronounced Taylor caps that precondition the region for convection. Aided by an accumulation of heat in the Weddell Deep Water layer, the ultimate trigger of convection that leads to MRPs is the advection of anomalously high upper-ocean-layer salinity. The crucial difference to WSP-producing LR ESM simulations is that in E3SMv0-HR, WSPs are realistically preceded by MRPs, which in turn are a result of the flow around bathymetry being represented with unprecedented detail.

Oceanic hypervelocity impact events: a viable mechanism for successful panspermia?

2006 ◽  
Vol 5 (3) ◽  
pp. 261-267 ◽  
Author(s):  
D.J. Milner ◽  
M.J. Burchell ◽  
J.A. Creighton ◽  
J. Parnell
Keyword(s):  
Water Layer ◽  
Solid Material ◽  
Hypervelocity Impact ◽  
Common Belief ◽  
Gas Gun ◽  
Deep Water Layer ◽  
Significant Survival ◽  
Mechanism Of Impact ◽  
The University ◽  
Impact Events

The idea that life migrates naturally between planetary bodies has grown in strength in recent years. This idea (panspermia) is believed to be possible via the mechanism of impact events. Previous research on this topic has concentrated on small meteoroids (micrometres to centimetres in diameter), with giant objects (metres to kilometres in diameter) being relatively ignored. This is due to the common belief that the larger objects vaporize on impact with the Earth's surface, which in most studies is taken as rock. Here we examine experimentally whether hypervelocity impacts into water result in significant survival of the impactors. For this study the University of Kent's two-stage light gas gun was used to accelerate millimetre-sized shale projectiles obliquely into a relatively deep water layer, at approximately 5 km s−1. Two shots have been made with surviving fragments being recovered from each. The surviving fragments appear highly shocked and display clear signs of cracking. The fragments that have been isolated contribute to a significant percentage (~10%) of the original unfired projectile mass and are as large as ~20% of the original projectile diameter. This indicates that oceanic hypervelocity impact events of large asteroids may deliver significant volumes of solid material to the Earth and thus provide a possible mechanism for successful panspermia.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths &gt;1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths &lt;300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths &lt;300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

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