Impact of water mass mixing and dust deposition on Nd concentration and ε Nd of the Arabian Sea water column

2014 ◽  
Vol 145 ◽  
pp. 30-49 ◽  
Author(s):  
Vineet Goswami ◽  
Sunil K. Singh ◽  
Ravi Bhushan
Keyword(s):  
Water Column ◽  
Arabian Sea ◽  
Water Mass ◽  
Sea Water ◽  
Dust Deposition

scholarly journals Equatorward Pathways of Solomon Sea Water Masses and Their Modifications

2011 ◽  
Vol 41 (4) ◽  
pp. 810-826 ◽  
Author(s):  
Angélique Melet ◽  
Jacques Verron ◽  
Lionel Gourdeau ◽  
Ariane Koch-Larrouy
Keyword(s):  
Water Column ◽  
Water Mass ◽  
Sea Water ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
Water Masses ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Western Boundary ◽  
Potential Influence

Abstract The Solomon Sea is a key region of the southwest Pacific Ocean, connecting the thermocline subtropics to the equator via western boundary currents (WBCs). Modifications to water masses are thought to occur in this region because of the significant mixing induced by internal tides, eddies, and the WBCs. Despite their potential influence on the equatorial Pacific thermocline temperature and salinity and their related impact on the low-frequency modulation of El Niño–Southern Oscillation, modifications to water masses in the Solomon Sea have never been analyzed to our knowledge. A high-resolution model incorporating a tidal mixing parameterization was implemented to depict and analyze water mass modifications and the Solomon Sea pathways to the equator in a Lagrangian quantitative framework. The main routes from the Solomon Sea to the equatorial Pacific occur through the Vitiaz and Solomon straits, in the thermocline and intermediate layers, and mainly originate from the Solomon Sea south inflow and from the Solomon Strait itself. Water mass modifications in the model are characterized by a reduction of the vertical temperature and salinity gradients over the water column: the high salinity of upper thermocline water [Subtropical Mode Water (STMW)] is eroded and exported toward surface and deeper layers, whereas a downward heat transfer occurs over the water column. Consequently, the thermocline water temperature is cooled by 0.15°–0.3°C from the Solomon Sea inflows to the equatorward outflows. This temperature modification could weaken the STMW anomalies advected by the subtropical cell and thereby diminish the potential influence of these anomalies on the tropical climate. The Solomon Sea water mass modifications can be partially explained (≈60%) by strong diapycnal mixing in the Solomon Sea. As for STMW, about a third of this mixing is due to tidal mixing.

scholarly journals Phosphorus and silicon in sea water off Plymouth during 1955

1957 ◽  
Vol 36 (2) ◽  
pp. 317-321 ◽  
Author(s):  
F. A. J. Armstrong
Keyword(s):  
Seasonal Variation ◽  
Water Column ◽  
Total Phosphorus ◽  
Water Mass ◽  
Sea Water ◽  
Whole Water

Temperatures and salinity, phosphate, total phosphorus and silicate analyses of water from the International Hydrographic Station E1 during 1955 are discussed. The seasonal variation is shown, and it appears that consumption of nutrients by plants in the spring was: phosphate 0·42 μg atom P/L, ‘total phosphorus’ 0·40 μg atom P/l., silicate 2·43 μg atom Si/1., these being means for the whole water column. Some irregularities are pointed out; they are probably attributable to changes in the water mass.

scholarly journals Causes of uncertainties in the representation of the Arabian Sea oxygen minimum zone in CMIP5 models

2021 ◽  
Author(s):  
Henrike Schmidt ◽  
Julia Getzlaff ◽  
Ulrike Löptien ◽  
Andreas Oschlies
Keyword(s):  
Southern Ocean ◽  
Arabian Sea ◽  
Climate Models ◽  
Water Mass ◽  
Sea Water ◽  
Coupled Model ◽  
Detailed Comparison ◽  
Cmip5 Models ◽  
Marine Habitats ◽  
Oxygen Minimum

Abstract. Open ocean oxygen minimum zones (OMZs) occur in regions with high biological productivity and weak ventilation. They restrict marine habitats and alter biogeochemical cycles. Global models show generally a large model-data misfit with regard to oxygen. Reliable statements about their future development and the quantification of their interaction with climate change are currently not possible. One of the most intense OMZs is located in the Arabian Sea (AS). We give an overview of the main model deficiencies with a detailed comparison of the historical state of ten climate models from the 5th coupled model intercomparison project (CMIP5) that present our present-day understanding of physical and biogeochemical processes. Considering a threshold of 60 μmol l−1, we find a general underestimation of the OMZ volume in the AS compared to observations, that is caused by a too shallow layer of oxygen-poor water in the models. The deviation of oxygen values in the deep AS is the result of subduction of higher oxygenated waters in the Southern Ocean in the models compared to observations. In addition, model deficiencies related to the coarse resolution of the abyssal ocean, are identified in the deep water mass transport from the Southern Ocean northward into the AS. Differences in simulated water mass properties and ventilation rates of Red Sea Water and Persian Gulf Water cause different mixing in the AS and thus influence the intensity of the OMZ. These differences also point towards variations in the parametrisations of the overflow from the marginal seas among the models. The results of this study are intended to foster future model improvements regarding the OMZ in the AS.

scholarly journals Mesoscale variability of water masses in the Arabian Sea as revealed by ARGO floats

2011 ◽  
Vol 8 (3) ◽  
pp. 1369-1402
Author(s):  
X. Carton ◽  
P. L'Hegaret
Keyword(s):  
Red Sea ◽  
Arabian Sea ◽  
Water Mass ◽  
Sea Water ◽  
Regional Scale ◽  
Water Masses ◽  
Northern Coast ◽  
Gulf Of Aden ◽  
Mesoscale Variability ◽  
Water Outflow

Abstract. By analysing ARGO float data over the last four years, some aspects of the mesoscale variability of water masses in the Arabian Sea are described. The Red Sea Water outflow is strong in the Southwestern Gulf of Aden, in particular when a cyclonic gyre predominates in this region. Salinities of 36.5 and temperatures of 16 °C are found there between 600 and 1000 m depths. The Red Sea Water is more dilute in the eastern part of the Gulf, and fragments of this water mass can be advected offshore across the gulf or towards its northern coast by the regional gyres. The Red Sea Water outflow is also detected along the northeastern coast of Socotra, and fragments of RSW are found between one and three degrees of latitude north of this island. In the whole Gulf of Aden, the correlation between the deep motions of the floats and the SSH measured by altimetry is strong, at regional scale. The finer scale details of the float trajectories are more often related to the anomalous water masses that they encounter. The Persian Gulf Water (PGW) is found in the float profiles near Ras ash Sharbatat (near 57° E, 18° N), again with 36.5 in salinity and about 18–19 °C in temperature. These observations were achieved in winter when the southwestward monsoon currents can advect PGW along the South Arabian coast. Fragments of PGW are found in the Arabian Sea between 18 and 20° N and 63 and 65° E, showing that this water mass can escape the Gulf of Oman southeastward, in particular during summer.

scholarly journals Phosphorus and silicon in sea water off Plymouth during 1954

1955 ◽  
Vol 34 (2) ◽  
pp. 223-228 ◽  
Author(s):  
F. A. J. Armstrong
Keyword(s):  
Seasonal Variation ◽  
Water Column ◽  
Total Phosphorus ◽  
Water Mass ◽  
Sea Water ◽  
Whole Water

SUMMARYThe results of analyses of water from the International Hydrographic Station EI during 1954 are discussed. The seasonal variation is shown, in which it appears that consumption of nutrients in the spring outburst of plants was: phosphate 0.37μg atom P/l., total phosphorus 0.26μg atom P/l., silicate 2.49μg atom Si/1., these figures being means for the whole water column. Unusual changes in silicate concentrations between January and February,and between August and September, are ascribed to changes in the water mass at the station. This conclusion is supported by the temperature, salinity and phosphate.observations.

MEASURES FOR ENVIRONMENT CONSERVATION IN ENCLOSED COASTAL SEAS

2017 ◽  
Author(s):  
Keizo Negi ◽  
Keizo Negi ◽  
Takuya Ishikawa ◽  
Takuya Ishikawa ◽  
Kenichiro Iba ◽  
...  
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
Water Mass ◽  
Sea Water ◽  
Red Tide ◽  
Water Environment ◽  
Quality Standard ◽  
Tokyo Bay ◽  
View Point ◽  
High Concentration

Japan experienced serious water pollution during the period of high economic growth in 1960s. It was also the period that we had such damages to human health, fishery and living conditions due to red tide as much of chemicals, organic materials and the like flowing into the seas along the growing population and industries in the coastal areas. Notable in those days was the issues of environment conservation in the enclosed coastal seas where pollutants were prone to accumulate inside due to low level of water circulation, resulting in the issues including red tide and oxygen-deficient water mass. In responding to these issues, we implemented countermeasures like effluent control with the Water Pollution Control Law and improvement/expansion of sewage facilities. In the extensive enclosed coastal seas of Tokyo Bay, Ise Bay and the Seto Inland Sea, the three areas of high concentration of population, we implemented water quality total reduction in seven terms from 1979, reducing the total quantities of pollutant load of COD, TN and TP. Sea water quality hence has been on an improvement trend as a whole along the steady reduction of pollutants from the land. We however recognize that there are differences in improvement by sea area such as red tide and oxygen-deficient water mass continue to occur in some areas. Meanwhile, it has been pointed out that bio-diversity and bio-productivity should be secured through conservation/creation of tidal flats and seaweed beds in the view point of “Bountiful Sea” To work at these challenges, through the studies depending on the circumstances of the water environment in the enclosed coastal seas, we composed “The Policy of Desirable State of 8th TPLCS” in 2015. We have also added the sediment DO into the water quality standard related to the life-environmental items in view of the preservation of aquatic creatures in the enclosed water areas. Important from now on, along the Policy, is to proceed with necessary measures to improve water quality with good considerations of differences by area in the view point of “Beautiful and bountiful Sea”.

scholarly journals Impact of the Kuroshio intrusion on the nutrient inventory in the upper northern South China Sea: insights from an isopycnal mixing model

2013 ◽  
Vol 10 (10) ◽  
pp. 6419-6432 ◽  
Author(s):  
C. Du ◽  
Z. Liu ◽  
M. Dai ◽  
S.-J. Kao ◽  
Z. Cao ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Column ◽  
South China ◽  
Water Mass ◽  
Northern South China Sea ◽  
Mixing Model ◽  
Nutrient Concentrations ◽  
Kuroshio Intrusion ◽  
China Sea ◽  
The Kuroshio

Abstract. Based on four cruises covering a seasonal cycle in 2009–2011, we examined the impact of the Kuroshio intrusion, featured by extremely oligotrophic waters, on the nutrient inventory in the central northern South China Sea (NSCS). The nutrient inventory in the upper 100 m of the water column in the study area ranged from ∼200 to ∼290 mmol m−2 for N + N (nitrate plus nitrite), from ∼13 to ∼24 mmol m−2 for soluble reactive phosphate and from ∼210 to ∼430 mmol m−2 for silicic acid. The nutrient inventory showed a clear seasonal pattern with the highest value appearing in summer, while the N + N inventory in spring and winter had a reduction of ∼13 and ∼30%, respectively, relative to that in summer. To quantify the extent of the Kuroshio intrusion, an isopycnal mixing model was adopted to derive the proportional contribution of water masses from the SCS proper and the Kuroshio along individual isopycnal surfaces. The derived mixing ratio along the isopycnal plane was then employed to predict the genuine gradients of nutrients under the assumption of no biogeochemical alteration. These predicted nutrient concentrations, denoted as Nm, are solely determined by water mass mixing. Results showed that the nutrient inventory in the upper 100 m of the NSCS was overall negatively correlated to the Kuroshio water fraction, suggesting that the Kuroshio intrusion significantly influenced the nutrient distribution in the SCS and its seasonal variation. The difference between the observed nutrient concentrations and their corresponding Nm allowed us to further quantify the nutrient removal/addition associated with the biogeochemical processes on top of the water mass mixing. We revealed that the nutrients in the upper 100 m of the water column had a net consumption in both winter and spring but a net addition in fall.

scholarly journals Occurrence and distribution of ladderane oxidation products in different oceanic regimes

2012 ◽  
Vol 9 (7) ◽  
pp. 2407-2418 ◽  
Author(s):  
D. Rush ◽  
E. C. Hopmans ◽  
S. G. Wakeham ◽  
S. Schouten ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Fatty Acids ◽  
Water Column ◽  
Arabian Sea ◽  
Degradation Products ◽  
Oxidation Products ◽  
Short Chain ◽  
Sediment Surface ◽  
Ammonium Oxidation ◽  
Anammox Activity ◽  
Sediment Matrix

Abstract. Ladderane fatty acids are commonly used as biomarkers for bacteria involved in anaerobic ammonium oxidation (anammox). These lipids have been experimentally shown to undergo aerobic microbial degradation to form short chain ladderane fatty acids. However, nothing is known of the production or the distribution of these oxic biodegradation products in the natural environment. In this study, we analysed marine water column particulate matter and sediment from three different oceanic regimes for the presence of ladderane oxidation products (C14 ladderane fatty acids) and of original ladderane fatty acids (C18 and C20 ladderane fatty acids). We found that ladderane oxidation products, i.e. C14 ladderane fatty acids, are already produced within the water column of the Arabian Sea oxygen minimum zone (OMZ) and thus only low amounts of oxygen (< 3 μM) are needed for the β-oxidation of original ladderane fatty acids to proceed. However, no short chain ladderane fatty acids were detected in the Cariaco Basin water column, where oxygen concentrations were below detection limit, suggesting that the β-oxidation pathway is inhibited by the absence of molecular oxygen, or that the microbes performing the degradation are not proliferating under these conditions. Comparison of distributions of ladderane fatty acids indicates that short chain ladderane fatty acids are mostly produced in the water column and at the sediment surface, before being preserved deeper in the sediments. Short chain ladderane fatty acids were abundant in Arabian Sea and Peru Margin sediments (ODP Leg 201), often in higher concentrations than the original ladderane fatty acids. In a sediment core taken from within the Arabian Sea OMZ, short chain ladderanes made up more than 90% of the total ladderanes at depths greater than 5 cm below sea floor. We also found short chain ladderanes in higher concentrations in hydrolysed sediment residues compared to those freely occurring in lipid extracts, suggesting that they had become bound to the sediment matrix. Furthermore, these matrix-bound short chain ladderanes were found at greater sediment depths than short chain ladderanes in the lipid extract, suggesting that binding to the sediment matrix aids the preservation of these lipids. Though sedimentary degradation of short chain ladderane fatty acids did occur, it appeared to be at a slower rate than that of the original ladderane fatty acids, and short chain ladderane fatty acids were found in sediments from the Late Pleistocene (~ 100 kyr). Together these results suggest that the oxic degradation products of ladderane fatty acids may be suitable biomarkers for past anammox activity in OMZs.

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