DOCSLIB.ORG

Ocean Salinity

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ocean Salinity “The highest form of human intelligence is the ability to observe without judging” Oceanography Krishnamurti Lecture 15 “The intuitive mind is a sacred gift and the a. Seawater Chemistry: rational mind is a faithful servant. We have Sources of Sea salts – Constancy rule created a society that honors the servant c. Residence time: Steady-state and has forgotten the gift” d. Dissolved gases Albert Einstein e. The carbonate system and Carbon cycle “The mind is everything, what you think you become” Buddha Vertical Temperature & Salinity Density Structure of the Oceans: Depth Temperature vs Depth Salinity vs Depth Salinity (‰) Temperature (°C) 34 34.5 35 35.5 36 0 5 10 15 20 0 0 1000 1000 Thermocline Halocline 2000 2000 (m) (m) Depth 3000 Halocline 3000 Depth 4000 4000 5000 5000 The Ocean can be divided into three structures: Surface layer; Pycnocline; Deep-layer. Pycnocline: Amounts to ~18% of the Oceans volume) Salinity • By weight, 96.5% of the Ocean are water, whereas the remainder 3.5% are composed of dissolved substances (salts). So, What is salinity? • Oceans: 1,370.103 km3. • Total weight of salts: 1,370.106 km3 ! 1.1015 cm3/km3 ! 1.03 g/cm3 ! 0.035 4.94! 1022 g of salts ~50 000 Trillion Tons!!!!! ! Could cover the entire planet with an even layer > 50 m in thickness! Salinity: Composition Major Elements Only 7 elements belong to this class > 100 ppm Common Concentration Percent Constituent form (ppm) by weight Chloride Cl- 18,980 50.08% Sodium Na+ 10,556 30.63% - Sulfate SO4 2,649 7.69% Magnesium Mg2+ 1,272 3.69% Calcium Ca2+ 400 1.16% + Only 12 elements make up 99.9% of the dissolved Potassium K 380 1.10% Carbon HCO - 140 0.41% constituents of seawater! 3 Total 34.377 99.76% Minor Elements Trace Elements Only 5 elements belong to this Important trace elements: class 1 ppm > x > 100 ppm Concentration < 1 ppm Common Concentration Percent Common Concentration Percent Constituent Constituent form (ppm) by weight form (ppb) by weight Nitrogen N 280 <0.001 Bromide - Br 65 0.19% Lithium Li 125 Strontium Sr2- 8 0.02% Iodine I 60 Boron B3+ 4.4 0.01% Phosphorus P 30 Zinc Zn 10 Silicon Si(OH)4 4.9 0.01% Iron Fe 6 Fluorine F- 1.4 0.004% Aluminum Al 2 Manganese Mn 2 Total 83.7 0.234% Etc… … Salinity distribution Uniformity? Uniformity? Sea water chemistry Uniformity of Ocean Water Principle of constant proportions 75% of the total Ocean volume • In 1865, the chemist George Forchammer noted that, have a although the total amount of dissolved solids (salinity) • Temperature: 0-5°C might vary among samples, the ratio of major salts in • Salinity: 34-35‰ samples of seawater from many locations was Oceans’ depths are filled with constant! cold water (colder than the ~17.5°C average T of the Na/Cl = 0.56; S/Cl = 0.14; Mg/Cl = 0.07 Oceans’ surface waters). ! Most of this water must have Regardless of changes in salinity (total amount of salts)! originated in polar latitudes, where it was chilled by losing The way salinity changes throughout the Oceans heat to the frigid air. depends almost entirely on: ! Uniformity of T and salinity - evaporation/precipitation balance, and of subsurface seawater from Ocean to Ocean suggests that - extent of mixing between surface and deep waters. Ocean basins are open systems! Departure: Departure: Ø Extensive areas of warm, shallow waters (i.e. Ø Utilization of carbon, calcium and magnesium by Bahamas), characterized by very active chemical biological activities (hard skeletons) and/or biological precipitation of calcium carbonate leading to changes in Ca2+ and HCO - to Ø Enclosed seas: estuaries and other regions can 3 total salinity. receive substantial inflow of river water which may contain less salts in different proportions Ø Areas of sea-floor where interstitial (pore) waters in sediments react with sediments ! Ø Basins, Fjords, etc., where bottom circulation is leading to large changes in ionic ratios. severely restricted (i.e. Black Sea). Complete - Ø Regions of sea-floor spreading and active utilization of O2 followed by SO4 . Ø Regions of sea-floor spreading and active submarine volcanism where heated seawater circulates through cracks of the oceanic crust. Ionic ratio in hydrothermal solutions are very different from those of normal seawater Example: Water on Earth Sources of Sea Salts? ! Water is a great solvent: a great many substances can dissolve within its matrix. ! Rain and river dissolve continental crustal rocks due to the formation of acids (H2CO3; H2SO4, HCl) and the solvent properties of water. ! H2O + CO2 " H2CO3 (acid) ! SO2 + OH + H2O # # H2SO4 (acid) !These dissolved species then reach the Oceans !So, does that mean that Oceans: through surface flow in rivers (rivers provide most of the dissolved elements to the Oceans!). • Have a diluted but similar composition as crustal rocks? • Are concentrated versions of river water? Sources of Sea Salts? Sources of Sea Salts? !So, does that mean that Oceans: !So, does that mean that Oceans are: • Have a diluted but similar composition as crustal rocks? • Concentrated versions of rivers? The three most abundant Rain Element % by weight elements in the crust (Si, Al, Fe) Si 28.2 do not appear at all in the Al 8.2 major-minor dissolved elements Fe 5.6 of the Oceans. Why? Ca 4.2 River Na 2.4 ! K 2.4 Solubility and reactivity of Mg 2.0 different elements. Ti 0.6 ! Si, Fe, Al (very common) not Mn 0.1 very soluble. Remain as particles P 0.1 ! Na, Ca, K, are relatively Seawater soluble and remain in solution Average percentages by weight of the ten most abundant elements (other than oxygen) in the Earth’s crust Sources of Sea Salts? Sources of Sea Salts? ! So, what is it? Origin of Chloride: It’s a matter of how fast the “clock ticks”… Negligible proportions of chloride in river water comes from weathering. • As water moves through the hydrological cycle on Chlorine comes from volcanism ! Continents, it picks up salts (dissolved constituents) (excess volatile) Weathering. So does sulfur! • Salts can then be maintained in solution for a long time But, if input is so small how can (rates!). the total mass be so high? Simplified Examples: H2O + CO2 " H2CO3 (acid) 2+ - • CaCO3 (calcite - sed) + H2CO3 (acid) " Ca + 2 HCO3 (bicarbonate) • 2NaAlSi3O8 (albite - metam/ign) + 5H2CO3 " Al2Si2O5(OH)4 + (kaolinite) + 2Na + H2CO3 + 4 SiO2 (partly sol) Ocean Salinity Sources of Sea Salts? Residence time! • Paradox: Oceans contain, in high concentrations, Total mass of dissolved compounds in the Ocean elements that are rare in Earth Crust; and, in low Rate of supply (or removal) concentrations, elements that are abundant in the Earth’s crust. Chloride: 261 1014 t/2.54 108 t/yr – Selective weathering – Residence time 1.03 108 yrs 103 Million Years! (Corrected ! ) Iron: 1.4 109 t/0.22 108 t/yr 64 yrs! Changes in residence time = Changes in reactivity Residence time – reactivity – mixing rate Steady State ! It seems so for several 100’s of My! And how do these elements leave? Ø Biological uptake/Chemical precipitation Ø Precipitation/Adsorption Ø Reverse weathering Ø Hydrothermal fluids Major elements Minor elements Biolimiting elements Steady State ! It seems so for several 100’s of My! Dissolved gases in water And how do these elements leave? Take a break, Grab a soda… • Biological uptake/chemical precipitation: Let’s assume we have a clear bottle of soda… Ca2+ + CO 2- " CaCO 3 3 You pop the lid ! gas escapes! (pressure) • Precipitation/Adsorption ! Fe + particles ! Iron-rich Clay particles You shake it more gas escapes! (mixing) Sediment diagenesis (Fe, Mn, S, metals) You warm it up ! even more gas escapes! • Reverse Weathering (temperature) Does it stop? ! 5Al Si O (OH) + 2K+ + 2HCO - + 4SiO " 2 2 5 4 3 2 ! 2KAl5Si7O20(OH)4 (Illite)+ 7H2O + 2 CO2 When final gas content of soda is at equilibrium + - with temperature and pressure ! Aluminosilicate + Na + HCO3 + SiO2 " Na0.33Al2.33Si3.67O10(OH)2 (Montmorillonite)+ H2O + CO2 • Hydrothermal fluids (1979) Sink for Mg. But source of Ca, K, Si, Fe… (?) Dissolved gases in water Take a break, Grab a soda… Density structure of the Ocean The total amount of gas that can be dissolved eventually reaches an equilibrium concentration which is proportional to: - Atmospheric concentration of gas in atmosphere - Temperature, - Pressure, - Salinity of water. The amount of gas usually $ as: P $ T % S % Dissolved gases in the Ocean Oxygen in the Ocean CO2(gas) + H2O + Energy " H12C6O6 (sugar) + O2 (gas) Photosynthesis possible only in photic zone (0-200 m) CO2(gas) + H2O + Energy " H12C6O6 (sugar) + O2 (gas) Oxygen minimum (utilization) at pycnocline – O2 Minimum Photosynthesis only in possible in photic zone (0-200 m) Oxygen limitation (utilization) at pycnocline – O2 Minimum Dissolved gases in the Ocean Temperature is the most important controlling factor! Dissolved gases in the Ocean The most abundant gases in the atmosphere: - N (78%) Argon and the other noble gases (He, Ne, Kr, and Ra) and 2 Nitrogen are essentially unreactive in the Oceans: - O2 (21%) - Argon (0.9%) Conservative gases - CO (0.03%) 2 In contrast, CO2 and O2 concentrations are altered by many The most abundant gases in the Oceans: biological and chemical processes in the sea. Non-conservative gases - CO2 (94.3%). Much more soluble! - N (3.4%) 2 Photosynthesis/Respiration: - O2 (2%) - Argon (0.3%) CO2(gas) + H2O + Energy # H12C6O6 (sugar) + O2 (gas) Difference due to the reactivity of CO2 is seawater leading to the various carbonate and bicarbonate equilibria H12C6O6 (sugar) + O2 (gas) # CO2(gas) + H2O + Energy + - + 2- CO2(gas) + H2O " H2CO3 " H + HCO3 " H + CO3 Dissolved gases/nutrients in the Ocean Dissolved gases in the Ocean CO2(gas) + H2O + Energy " H12C6O6 (sugar) + O2 (gas) Photosynthesis only possible in photic zone (0-200 m) CO2(gas) + H2O + Nutrients (N,P) + Energy " OM + O2 (gas) Oxygen limitation (utilization) at pycnocline – O2 Minimum.
Load more

Recommended publications
  • MIMOC: a Global Monthly Isopycnal Upper-Ocean Climatology with Mixed Layers*
    1 * 1 MIMOC: A Global Monthly Isopycnal Upper-Ocean Climatology with Mixed Layers 2 3 Sunke Schmidtko1,2, Gregory C. Johnson1, and John M. Lyman1,3 4 5 1National Oceanic and Atmospheric Administration, Pacific Marine Environmental 6 Laboratory, Seattle, Washington 7 2University of East Anglia, School of Environmental Sciences, Norwich, United 8 Kingdom 9 3Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, 10 Honolulu, Hawaii 11 12 Accepted for publication in 13 Journal of Geophysical Research - Oceans. 14 Copyright 2013 American Geophysical Union. Further reproduction or electronic 15 distribution is not permitted. 16 17 8 February 2013 18 19 ______________________________________ 20 *Pacific Marine Environmental Laboratory Contribution Number 3805 21 22 Corresponding Author: Sunke Schmidtko, School of Environmental Sciences, University 23 of East Anglia, Norwich, NR4 7TJ, UK. Email: [email protected] 2 24 Abstract 25 26 A Monthly, Isopycnal/Mixed-layer Ocean Climatology (MIMOC), global from 0–1950 27 dbar, is compared with other monthly ocean climatologies. All available quality- 28 controlled profiles of temperature (T) and salinity (S) versus pressure (P) collected by 29 conductivity-temperature-depth (CTD) instruments from the Argo Program, Ice-Tethered 30 Profilers, and archived in the World Ocean Database are used. MIMOC provides maps 31 of mixed layer properties (conservative temperature, Θ, Absolute Salinity, SA, and 32 maximum P) as well as maps of interior ocean properties (Θ, SA, and P) to 1950 dbar on 33 isopycnal surfaces. A third product merges the two onto a pressure grid spanning the 34 upper 1950 dbar, adding more familiar potential temperature (θ) and practical salinity (S) 35 maps.
    [Show full text]
  • Trophic Diversity of Plankton in the Epipelagic and Mesopelagic Layers of the Tropical and Equatorial Atlantic Determined with Stable Isotopes
    diversity Article Trophic Diversity of Plankton in the Epipelagic and Mesopelagic Layers of the Tropical and Equatorial Atlantic Determined with Stable Isotopes Antonio Bode 1,* ID and Santiago Hernández-León 2 1 Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, Apdo 130, 15080 A Coruña, Spain 2 Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de las Palmas de Gran Canaria, Campus de Taliarte, Telde, Gran Canaria, 35214 Islas Canarias, Spain; [email protected] * Correspondence: [email protected]; Tel.: +34-981205362 Received: 30 April 2018; Accepted: 12 June 2018; Published: 13 June 2018 Abstract: Plankton living in the deep ocean either migrate to the surface to feed or feed in situ on other organisms and detritus. Planktonic communities in the upper 800 m of the tropical and equatorial Atlantic were studied using the natural abundance of stable carbon and nitrogen isotopes to identify their food sources and trophic diversity. Seston and zooplankton (>200 µm) samples were collected with Niskin bottles and MOCNESS nets, respectively, in the epipelagic (0–200 m), upper mesopelagic (200–500 m), and lower mesopelagic layers (500–800 m) at 11 stations. Food sources for plankton in the productive zone influenced by the NW African upwelling and the Canary Current were different from those in the oligotrophic tropical and equatorial zones. In the latter, zooplankton collected during the night in the mesopelagic layers was enriched in heavy nitrogen isotopes relative to day samples, supporting the active migration of organisms from deep layers. Isotopic niches showed also zonal differences in size (largest in the north), mean trophic diversity (largest in the tropical zone), food sources, and the number of trophic levels (largest in the equatorial zone).
    [Show full text]
  • Impact of the Pycnocline Layer on Bacterioplankton
    MARINE ECOLOGY - PROGRESS SERIES Vol. 38: 295403, 1987 Published July 13 Mar. Ecol. Prog. Ser. l Impact of the pycnocline layer on bacterioplankton: diel and spatial variations in microbial parameters in the stratified water column of the Gulf of Trieste (Northern Adriatic Sea) Gerhard J. ~erndl'& Vlado ~alaCiC~ ' Institute for Zoology. University of Vienna. Althanstr. 14, A-1090 Vienna, Austria Marine Biology Station Piran, Cesta JLA 65, YU-66330 Piran. Yugoslavia ABSTRACT: Die1 variations in bacterial density, frequency of bvidlng cells (FDC) and bssolved organic carbon (DOC) in the stratified water column of the Gulf of Trieste were investigated at various depths. In the surface layers morning and afternoon DOC peaks (up to 10 mg I-') were observed in 3 out of 4 diel cycles. Bacterial abundance remained fairly constant over the diel cycles; however, bacterial activity as measured by FDC showed pronounced peaks in late afternoon and dawn coinciding with the DOC maximum concentrations. The pycnocline layer exhibited DOC concentrations similar to those of the overlying waters. The frequency of dividing cells (FDC), however, remained high throughout the entire diel cycle. The observed pronounced diel variations in bacterial production were therefore largely restricted to the layers well above the pycnocline; bacterial production contributed less than 20 % to the overall diel production (500 to 1000 pg C 1-' d-') in the uppermost 5 m water body. Highest diel production was found in the pycnocline layer at the end of the phytoplankton bloom (June and July) probably reflecting the formation of nutrient-enriched microzones around decaying phytoplankton cells due to reduced sinking velocities in the pycnocline layer.
    [Show full text]
  • Dispersion in the Open Ocean Seasonal Pycnocline at Scales of 1–10Km and 1–6 Days
    FEBRUARY 2020 S U N D E R M E Y E R E T A L . 415 Dispersion in the Open Ocean Seasonal Pycnocline at Scales of 1–10km and 1–6 days a MILES A. SUNDERMEYER AND DANIEL A. BIRCH University of Massachusetts Dartmouth, North Dartmouth, Massachusetts JAMES R. LEDWELL Woods Hole Oceanographic Institution, Woods Hole, Massachusetts b MURRAY D. LEVINE, STEPHEN D. PIERCE, AND BRANDY T. KUEBEL CERVANTES Oregon State University, Corvallis, Oregon (Manuscript received 23 January 2019, in final form 14 November 2019) ABSTRACT Results are presented from two dye release experiments conducted in the seasonal thermocline of the 2 2 Sargasso Sea, one in a region of low horizontal strain rate (;10 6 s 1), the second in a region of intermediate 2 2 horizontal strain rate (;10 5 s 1). Both experiments lasted ;6 days, covering spatial scales of 1–10 and 1–50 km for the low and intermediate strain rate regimes, respectively. Diapycnal diffusivities estimated from 26 2 21 2 21 the two experiments were kz 5 (2–5) 3 10 m s , while isopycnal diffusivities were kH 5 (0.2–3) m s , with the range in kH being less a reflection of site-to-site variability, and more due to uncertainties in the background strain rate acting on the patch combined with uncertain time dependence. The Site I (low strain) experiment exhibited minimal stretching, elongating to approximately 10 km over 6 days while maintaining a width of ;5 km, and with a notable vertical tilt in the meridional direction. By contrast, the Site II (inter- mediate strain) experiment exhibited significant stretching, elongating to more than 50 km in length and advecting more than 150 km while still maintaining a width of order 3–5 km.
    [Show full text]
  • Chapter 5 Lecture
    ChapterChapter 1 5 Clickers Lecture Essentials of Oceanography Eleventh Edition Water and Seawater Alan P. Trujillo Harold V. Thurman © 2014 Pearson Education, Inc. Chapter Overview • Water has many unique thermal and dissolving properties. • Seawater is mostly water molecules but has dissolved substances. • Ocean water salinity, temperature, and density vary with depth. © 2014 Pearson Education, Inc. Water on Earth • Presence of water on Earth makes life possible. • Organisms are mostly water. © 2014 Pearson Education, Inc. Atomic Structure • Atoms – building blocks of all matter • Subatomic particles – Protons – Neutrons – Electrons • Number of protons distinguishes chemical elements © 2014 Pearson Education, Inc. Molecules • Molecule – Two or more atoms held together by shared electrons – Smallest form of a substance © 2014 Pearson Education, Inc. Water molecule • Strong covalent bonds between one hydrogen (H) and two oxygen (O) atoms • Both H atoms on same side of O atom – Bent molecule shape gives water its unique properties • Dipolar © 2014 Pearson Education, Inc. Hydrogen Bonding • Polarity means small negative charge at O end • Small positive charge at H end • Attraction between positive and negative ends of water molecules to each other or other ions © 2014 Pearson Education, Inc. Hydrogen Bonding • Hydrogen bonds are weaker than covalent bonds but still strong enough to contribute to – Cohesion – molecules sticking together – High water surface tension – High solubility of chemical compounds in water – Unusual thermal properties of water – Unusual density of water © 2014 Pearson Education, Inc. Water as Solvent • Water molecules stick to other polar molecules. • Electrostatic attraction produces ionic bond . • Water can dissolve almost anything – universal solvent © 2014 Pearson Education, Inc. Water’s Thermal Properties • Water is solid, liquid, and gas at Earth’s surface.
    [Show full text]
  • Mix It Up, Mix It Down , Volume 1, a Quarterly 22, Number the O Journal of Intriguing Implications of Ocean Layering
    or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The approval portionthe ofwith any articlepermitted only photocopy by is of machine, reposting, this means or collective or other redistirbution This article has This been published in HANDS-ON OCEANOGRAPHY Oceanography Mix it Up, Mix it Down journal of The 22, Number 1, a quarterly , Volume Intriguing Implications of Ocean Layering BY PETER J.S. FRANKS AND SHARON E.R. FRANKS O ceanography ceanography PURPOSE OF ACTIVITY The density increase between the surface waters and the S Using a physical simulation, we explore the vertical density deep waters is often confined to a few relatively thin layers ociety. structure within the ocean and how layering (density stratifica- known as pycnoclines. Most ocean basins have a permanent © 2009 by The 2009 by tion) controls water motion, impedes nutrient transport, and pycnocline between about 500 and 1000-m depth, and a sea- regulates biological productivity. Our demonstration enables sonal pycnocline that forms during the summer between about O students to visualize the formation of horizontal layers in the 20 and 100-m depth. ceanography ocean’s interior and the slow undulation of large-amplitude Small density differences between ocean layers reduce the O ceanography ceanography internal waves. We show that stratification limits the vertical gravitational force acting on a layer. The reduced gravity allows S ociety. ociety. transport of energy and nutrients. The region of strong vertical waves inside the ocean—internal waves—to achieve amplitudes A density gradient—the pycnocline—is a barrier to the downward of tens of meters.
    [Show full text]
  • Variation in the Position of the Upwelling Front on the Oregon Shelf Jay A
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. C11, 3180, doi:10.1029/2001JC000858, 2002 Variation in the position of the upwelling front on the Oregon shelf Jay A. Austin Center for Coastal Physical Oceanography, Old Dominion University, Norfolk, Virginia, USA John A. Barth College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA Received 5 March 2001; revised 6 March 2002; accepted 18 June 2002; published 2 November 2002. [1] As part of an experiment to study wind-driven coastal circulation, 17 hydrographic surveys of the middle to inner shelf region off the coast of Newport, OR (44.65°N, from roughly the 90 m isobath to the 10 m isobath) were performed during Summer 1999 with a small, towed, undulating vehicle. The cross-shelf survey data were combined with data from several other surveys at the same latitude to study the relationship between upwelling intensity and wind stress field. A measure of upwelling intensity based on the position of the permanent pycnocline is developed. This measure is designed so as to be insensitive to density-modifying surface processes such as heating, cooling, buoyancy plumes, and wind mixing. It is highly correlated with an upwelling index formed by taking an exponentially weighted running mean of the alongshore wind stress. This analysis suggests that the front relaxes to a dynamic (geostrophic) equilibrium on a timescale of roughly 8 days, consistent with a similar analysis of moored hydrographic observations. This relationship allows the amount of time the pycnocline is outcropped to be estimated and could be used with historical wind records to better quantify interannual cycles in upwelling.
    [Show full text]
  • Geophysical Fluid Dynamics: Whence, Whither and Why? Rspa.Royalsocietypublishing.Org Geoffrey K
    Geophysical Fluid Dynamics: Whence, Whither and Why? rspa.royalsocietypublishing.org Geoffrey K. Vallis Research University of Exeter, UK _is arTicle discusses The role of Geophysical Fluid Article submitted to journal Dynamics ($­) in undersTanding The naTural environmenT, and in parTicular The dynamics of aTmospheres and oceans on EarTh and elsewhere. Keywords: $­, as usually undersTood, is a branch of The GFD geosciences ThaT deals wiTh uid dynamics and ThaT, by TradiTion, seeks To exTracTThe bare essence of a phenomenon, omiTTing deTail where possible. Author for correspondence: _e geosciences in general deal wiTh complex Geoffrey K. Vallis, University of inTeracTing sysTems and in some ways resemble Exeter, [email protected] condensed maTTer physics or aspects of biology, where we seek explanaTions of phenomena aT a higher level Than simply direcTly calculaTing The inTeracTions of all The consTiTuenT parts. _aT is, we Try To develop Theories or make simple models of The behaviour of The sysTem as a whole. However, These days in many geophysical sysTems of inTeresT, we can also obTain informaTion for how The sysTem behaves by almosT direcT numerical simulaTion from The governing equaTions. _e numerical model itself Then expliciTly predicts The emergenT phenomena – The Gulf STream for example – someThing ThaT is sTill usually impossible in biology or condensed maTTer physics. Such simulaTions, as manifesTed for example in complicaTed General CirculaTion Models, have in some ways been exTremely successful and one may reasonably now ask wheTher undersTanding a complex geophysical sysTem is necessary for predicTing iT. In whaT follows we discuss such issues and The roles ThaT $­ has played in The pasT and will play in The fuTure.
    [Show full text]
  • Vertical Stratification and the Pycnocline
    MD1 appendixD Vertical Stratification and the Pycnocline The pycnocline has a functional role in defining designated use boundaries. The defi- nitions of the designated use boundaries take into account the types and needs of the living resources that inhabit different parts of the Chesapeake Bay, as well as the bathymetry, hydrology, physical features, and natural stratification of the Chesa- peake Bay waters as described in Chapter IV. STRATIFICATION Vertical stratification is foremost among the physical factors affecting dissolved oxygen concentrations in some parts of Chesapeake Bay and its tidal tributaries. Stratification arises from differences in water density within the water column due to vertical differences in the salinity and temperature of the source waters feeding into Chesapeake Bay tidal waters. The water coming into Chesapeake Bay and its tidal tributaries from the land via the tributaries is fresh while water from the ocean is saline. In the summer period, the water coming from the land is also warmer than ocean water. Colder water is more dense than warmer water, and saline water is more dense than fresh. The simple model is that the less dense freshwater moves seaward over the layer of more dense seawater moving from the mouth of Chesapeake Bay northward. An idealized example is shown in Figure D-1. To the extent that the two (or more) layers remain self-contained and poorly mixed, the waters are stratified. If the density discontinuity is great enough to prevent mixing of the layers and con- stitutes a vertical barrier to diffusion of dissolved oxygen, then a pycnocline is said to exist.
    [Show full text]
  • Predicting the Physical Effects of Relocating Boston's Sewage Outfall
    Estuarine, Coastal and Shelf Science (2000) 50, 59–72 Article No. ecss.1999.0532, available online at http://www.idealibrary.com on Predicting the Physical Effects of Relocating Boston’s Sewage Outfall R. P. Signella,d, H. L. Jenterb and A. F. Blumbergc aU.S. Geological Survey, 384 Woods Hole Road, Quissett Campus, Woods Hole, MA 02543-1598, U.S.A. bU.S. Geological Survey, National Center, Reston, VA 22092, U.S.A. cHydroQual, Inc., 1 Lethbridge Place, Mahwah, NJ 07450, U.S.A. Received 31 December 1998 and accepted in revised form 22 February 1999 Boston is scheduled to cease discharge of sewage effluent in Boston Harbor in Spring 2000 and begin discharge at a site 14 km offshore in Massachusetts Bay in a water depth of about 30 m. The effects of this outfall relocation on effluent dilution, salinity and circulation are predicted with a three-dimensional hydrodynamic model. The simulations predict that the new bay outfall will greatly decrease effluent concentrations in Boston Harbor (relative to the harbour outfall) and will not significantly change mean effluent concentrations over most of Massachusetts Bay. With the harbour outfall, previous observations and these simulations show that effluent concentrations exceed 0·5% throughout the harbour, with a harbour wide average of 1–2%. With the bay outfall, effluent concentrations exceed 0·5% only within a few km of the new outfall, and harbour concentrations drop to 0·1–0·2%, a 10-fold reduction. During unstratified winter conditions, the local increase in effluent concentration at the bay outfall site is predicted to exist throughout the water column.
    [Show full text]
  • Density and Stratification Density of Water Ocean Surface Temperature
    Density of water density = mass/volume units: g/cm 3 (= g/ml = kg/L) Effect of Temperature on Density density of water - @ 4 oC and 1 atm pressure fresh:1.000 g/cm 3 (by definition!) Density and Stratification sea: 1.027 g/cm 3 (on average) what determines water density? temperature – inverse relationship the major players of the ocean’s layers lower temp = higher density higher temp = lower density salinity – direct relationship lower sal = lower density higher sal = higher density pressure water is essentially (but not exactly) incompressible but at very high pressures (deep depths) – pressure increases density sea level would be ~30-50 m higher without pressure effect Ocean surface temperature often called sea surface temperature or SST strongly correlates with latitude because insolation (amount of sunlight striking Earth’s surface) is high at low latitudes & low at high latitudes surface ocean isotherms (lines of equal temperature) generally trend east-west except where deflected toward poles or equator by currents warm water carried poleward on western side of ocean basins Gulf Stream, Kuroshio Current – Northern Hemisphere Brazil Current, East Australia Current – Southern Hemisphere cooler water carried equatorward on eastern side of ocean basins Canary Current, California Current – Northern Hemisphere Benguela Current, Peru Current – Southern Hemisphere SST overall pattern highest in the tropics (~25-29 oC) where insolation is highest decreases poleward with decreasing insolation negative temperatures
    [Show full text]
  • Physical Oceanography
    Physical Oceanography 1. Ocean, Origin, Geology 2. Geography, Topography 3. Temperature, Salinity, Density and Oxygen – Horizontal/Vertical 4. Mixed Layer 5. Water Masses 6. General Circulation of the Oceans - Thermohaline Circulation - Wind driven circulation 7. Upper ocean processes, heat fluxes MSc Atmospheric Sciences 2016 IITM-University of Pune Roxy Mathew Koll :: CCCR/IITM The Ocean Areas of Earth’s surface above and below sea level as a percentage of the total area of Earth (in 100m intervals). Data from Becker et al. (2009). 1. The ocean covers 71% of Earth’s surface 2. The ocean contains 97% of the water on Earth 3. The ocean is Earth’s most important feature 4. They are only temporary features of a single world ocean 5. Average ocean depth is about 4½ times greater than the average height of the continents above sea level Origin of the Ocean 1. Source: The major trapped volatile during the formation of Earth was water (H2O). Others included nitrogen (N2), the most abundant gas in the atmosphere, carbon dioxide (CO2), and hydrochloric acid (HCl), which was the source of the chloride in sea salt (mostly NaCl). 2. Outgassing: Ocean had its origin from the prolonged escape of water vapor and other gases from the molten igneous rocks of the Earth to the clouds surrounding the cooling Earth. 3. Cooling and Rains: After the Earth's surface had cooled to a temperature below the boiling point of water, rain began to fall and continued to fall for centuries. 4. Present state: As the water drained into the great hollows in the Earth's surface, the primeval ocean came into existence, about 4billion years ago.
    [Show full text]