DOCSLIB.ORG

Deep Convective Plumes in the Ocean

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Deep Convective Plumes in the Ocean FEATURE DEEP CONVECTIVE PLUMES IN THE OCEAN By Terri Paluszkiewicz, Roland W. Garwood and Donald W. Denbo DEEP CONVECTION is a process in which recent advances in the study of deep open-ocean the mesoscale ocean circulation and atmospheric convective plumes. forcing work together to weaken the ambient Deep convection occurs primarily in the Green- This process plays stratification and to cause surface waters to sink land, Labrador, Weddell, and Mediterranean Seas, to great depths with large vertical velocities. and the water masses formed in these locations an important role in This process plays an important role in bottom contribute to the deep circulation. Estimates of the bottom and and intermediate water formation and ultimately amount of deep water formed by open-ocean deep in the large-scale thermohaline circulation, convection range from 5 × 106 to 10 × 106 m 3 intermediate water which in turn plays a central part in determining s-~; this is of the same order of magnitude as the global climate. Until now, our understanding of estimates of deep water produced near ocean formation and deep convection was based on observations and boundaries (7 × 106 to 10 × 106 m 3 s -~) (Sankey, ultimately in the models of the mesoscale effects of deep convec- 1973; Killworth, 1979, 1983; Carmack, 1990). tion. With recent advances in numerical model- During the preconditioning phase of deep convec- large-scale ing techniques and instrumentation, we have tion, a background of low static stability is cre- thermohaline begun to study the role of the mixing elements: ated. This is followed by a mixing phase that oc- the deep, penetrative convective plumes shown curs where preconditioning has been active and is circulation . in Figure I. These plumes are turbulent, have a characterized by intense and rapid cooling, evapo- large vertical scale and have attributes that are ration and/or freezing. Surface waters then become unique for turbulent plumes: they are affected denser than deeper waters; as a consequence, by the nonlinear relationship between tempera- parcels of water descend with entrainment and ture and pressure in the density of sea water and vigorous mixing at vertical velocities of 2-10 cm by rotation. Numerical model results, such as s -~. In the sinking and spreading phase, the newly those shown here, clearly demonstrate that tur- formed dense water equilibrates with the surround- bulent mixing affects climate-related processes; ings and spreads horizontally. that is, deep convective plumes are evidence Deep convective plumes (Fig. 1) transport and that small-scale features affect the large-scale mix water over many hundreds of meters during a circulation. time period of hours to days (Aagaard and Car- Two types of convection have been linked with mack, 1989). Where deep convection occurs, the deep water formation: near-boundary sinking and across-isopycnal advection produces intermediate deep penetrative sinking in the open ocean and bottom water and controls the vertical struc- (Solomon, 1974; Carmack, 1990). The proper rep- ture of deep water masses. Ultimately, these water resentation of these processes in numerical models masses influence the deep circulation patterns that becomes important in simulating the thermohaline in turn affect the meridional heat transport within circulation. In coarse resolution models, open- the ocean. Manabe and Stouffer's (1993) climate ocean deep convection is not resolved, and re- simulations have shown that the thermal and dy- search is underway to understand the process and namical structure of the oceans could change in re- to develop a parameterization of this process for sponse to model climates with increased CO2. In ocean circulation models. The near-boundary sink- their simulations, the addition of low-salinity sur- ing is also of interest, but here we focus on some face water at high latitudes prevents the ventilation of the deep ocean, thus reducing, or in some cases nearly extinguishing, the thermohaline circulation. T. Paluszkiewicz, D.W. Denbo, Pacific Northwest Labora- The dynamics of the oceanic uptake of CO~ and tory, Battelle/Marine Sciences Laboratory, 1529 W. Sequim tracers is therefore strongly determined by the rate Bay Rd., Sequim, WA 98382, USA. R.W. Garwood, Naval Postgraduate School, Monterey, CA 93940, USA. of downward transport of surface waters to depth. OCEANOGRAPHY°VoI.7, NO. 2"1994 37 Active convective elements with horizontal scales of <1 km have been observed in the Green- land Sea (Schott et al., 1993a) and Mediterranean Sea (Schott et al., 1993b; The THETIS Group, 500 1994). Surface evidence of convective plumes was T found in synthetic aperture radar (SAR) imagery by Carsey and Garwood (1993) (Fig. 2a). The SAR imagery was able to distinguish plumes be- i000 cause they appeared to be ice covered and the con- vective return areas were open water. The sizes of the plumes (200-400 m in diameter) agreed with model experiments and with the scaling arguments 1500 of Jones and Marshall (1993). The surface expres- sion of plumes and the association with ice indi- cate that the brine from ice growth might act as a trigger of convection. The compensating upwelling flow and consequent heat flux may retard ice 500~" growth. Scott and Killworth (1991) found evi- dence of vertical plumes that were not the result of surface instabilities. These vertically well-mixed If . ;. areas may have been 3 km wide and extended lOOO downward from the base of the mixed layer (Fig. 3a.). These observations indicate that there may be , L two different modes of instability, parcel instabili- ties and layer instabilities. 1500 T Theories and Hypotheses for Deep Convective 2000 2500 2000 2500 2000 2500 2000 Plumes east (rn) 2500 e~t (m) east, (ra) Gravity-driven oceanic convection is both •" 0.04 m/s nonlinear and nonhydrostatic, with three-dimen- -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 sional interactions among turbulent eddies result- ('~ ing in a cascade of turbulent kinetic energy Fig. l: The simulated potential temperature evolution from an LES experi- (TKE) from the largest plume scale to the mi- ment of open-ocean deep convective plume formation (Courtesy D. Denbo). croscale. The following two processes, normally negligible in turbulent boundary-layer dynamics, become important in the deep convective plumes: Observations of Deep Convective Plumes (i) thermobaricity, a consequence of the nonlinear There are several scales of organization that are relationship between temperature and pressure in believed to be important in deep convection in the density of sea water and (ii) the Coriolis which plumes represent the smallest-scale process. force. Gascard (1991) notes that on the mesoscale, chim- Gill (1973) first showed that sinking cold and neys and eddies play an important role in the saline Weddell Sea shelf water formed by freez- water mass formation process. ing conditions would experience additional down- Plumes are convectively driven vertical mo- ward acceleration with increased pressure as the tions. Whereas shallow convection, or mixed-layer dense water flowed down the sloping bottom. Mc- deepening, has scales of hundreds of meters (Kill- Dougall (1984) called this nonlinear effect in the Plumesare convec- worth, 1983; Guest and Davidson, 1991), deep equation of state thermobaricio,. Thermobaricity convective plumes have vertical scales of 1 to 2 influences deep convection significantly when sea tively driven vertical km (Gascard and Clarke, 1983), horizontal scales water is colder than 0°C. In an analysis of the motions. on the order of 1 km and associated vertical veloc- TKE budget, thermobaricity has been shown to ities of 2-10 cm s ~ (Rudels et al., 1989; Schott enhance the buoyant production of mixed-layer and Leaman, 1991; Carsey and Garwood, 1993; turbulence, resulting in a probable increase in en- Jones and Marshall, 1993; Roach et al., 1993; trainment and a possible mid-depth maximum in Schott et al., 1993a: Denbo and Skyllingstad, TKE for the deepest turbulent mixing layers in 1994; Garwood et al., 1994). Time scales associ- the polar seas (Garwood, 1991). The use of the ated with convective plumes are reported to be full nonlinear equation of state for sea water is several hours to several days (Rudels et al., 1989; necessary in order to retain the thermobaric ef- Roach et al., 1993). The convective plumes appear fect on the energetics of deep convection (Mc- as isolated regions of vertically coherent, down- Dougall, 1987; Aagaard and Carmack, 1989; ward vertical velocity when measured by acoustic Denbo and Skyllingstad, 1992; Garwood et al., doppler current profilers (ADCPs). 1994; Paluszkiewicz and Romea, 1994). 38 OCEANOGRAPHY'VoI. 7. No. 2o1994 ERS-1 SAR BLOWUP has been stored seasonally. Both of these instabili- FROM: 3016-2133 73.6°N, 11.1°W ties are dependent on the likelihood that a water FEBRUARY 12, 1992 parcel or water column that was hydrostatically stable near the surface could become hydrostati- cally unstable if displaced downward with com- mensurate pressure increase. A parcel instability occurs when a mixed layer .!. ~ X parcel penetrates below a critical depth and, having become more dense than the ambient water, contin- ues to sink, thereby escaping the well-mixed surface } :-. i) layer and penetrating the pycnocline. This process is analogous to the similarly named process in the atmospheric boundary layer that is associated with cumulus formation (Garwood, 1992a). Penetrative convection is when a plume overshoots the depth of static stability due to the momentum in the plume. When penetrative convection occurs, it causes addi- tional mixing at the mixed-layer base beyond that predicted by hydrostatic adjustment. Additional penetration or super-penetration may be possible 6.4 km when the thermobaric instability provides additional COPYRIGHT ESA 1992 (a) downward momentum to the parcel. A related layer instability may occur if the whole mixed layer is downwelled in response to large-scale convergence associated with wind forc- ing (Ekman pumping) or by preconditioning asso- ciated with larger-scale dynamics.
Load more

Recommended publications
  • Respiration in the Mesopelagic and Bathypelagic Zones of the Oceans
    CHAPTER 10 Respiration in the mesopelagic and bathypelagic zones of the oceans Javier Arístegui1, Susana Agustí2, Jack J. Middelburg3, and Carlos M. Duarte2 1 Facultad de Ciencias del Mar, Universidad de las Palmas de Gran Canaria, Spain 2 IMEDEA (CSIC–UIB), Spain 3 Netherlands Institute of Ecology, The Netherlands Outline In this chapter the mechanisms of transport and remineralization of organic matter in the dark water-column and sediments of the oceans are reviewed. We compare the different approaches to estimate respiration rates, and discuss the discrepancies obtained by the different methodologies. Finally, a respiratory carbon budget is produced for the dark ocean, which includes vertical and lateral fluxes of organic matter. In spite of the uncertainties inherent in the different approaches to estimate carbon fluxes and oxygen consumption in the dark ocean, estimates vary only by a factor of 1.5. Overall, direct measurements of respiration, as well as − indirect approaches, converge to suggest a total dark ocean respiration of 1.5–1.7 Pmol C a 1. Carbon mass − balances in the dark ocean suggest that the dark ocean receives 1.5–1.6 Pmol C a 1, similar to the estimated respiration, of which >70% is in the form of sinking particles. Almost all the organic matter (∼92%) is remineralized in the water column, the burial in sediments accounts for <1%. Mesopelagic (150–1000 m) − − respiration accounts for ∼70% of dark ocean respiration, with average integrated rates of 3–4 mol C m 2 a 1, − − 6–8 times greater than in the bathypelagic zone (∼0.5 mol C m 2 a 1).
    [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]
  • Article Is Available Gen Availability
    Hydrol. Earth Syst. Sci., 23, 1763–1777, 2019 https://doi.org/10.5194/hess-23-1763-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. Oxycline oscillations induced by internal waves in deep Lake Iseo Giulia Valerio1, Marco Pilotti1,4, Maximilian Peter Lau2,3, and Michael Hupfer2 1DICATAM, Università degli Studi di Brescia, via Branze 43, 25123 Brescia, Italy 2Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany 3Université du Quebec à Montréal (UQAM), Department of Biological Sciences, Montréal, QC H2X 3Y7, Canada 4Civil & Environmental Engineering Department, Tufts University, Medford, MA 02155, USA Correspondence: Giulia Valerio ([email protected]) Received: 22 October 2018 – Discussion started: 23 October 2018 Revised: 20 February 2019 – Accepted: 12 March 2019 – Published: 2 April 2019 Abstract. Lake Iseo is undergoing a dramatic deoxygena- 1 Introduction tion of the hypolimnion, representing an emblematic exam- ple among the deep lakes of the pre-alpine area that are, to a different extent, undergoing reduced deep-water mixing. In Physical processes occurring at the sediment–water inter- the anoxic deep waters, the release and accumulation of re- face of lakes crucially control the fluxes of chemical com- duced substances and phosphorus from the sediments are a pounds across this boundary (Imboden and Wuest, 1995) major concern. Because the hydrodynamics of this lake was with severe implications for water quality. In stratified shown to be dominated by internal waves, in this study we in- lakes, the boundary-layer turbulence is primarily caused by vestigated, for the first time, the role of these oscillatory mo- wind-driven internal wave motions (Imberger, 1998).
    [Show full text]
  • Direct Observations of Along-Isopycnal Upwelling and Diapycnal Velocity at a Shelfbreak Front John A
    University of Rhode Island DigitalCommons@URI Graduate School of Oceanography Faculty Graduate School of Oceanography Publications 2004 Direct Observations of Along-Isopycnal Upwelling and Diapycnal Velocity at a Shelfbreak Front John A. Barth Dave Hebert University of Rhode Island See next page for additional authors Follow this and additional works at: https://digitalcommons.uri.edu/gsofacpubs Citation/Publisher Attribution Barth, J.A., D. Hebert, A.C. Dale, and D.S. Ullman, 2004: Direct Observations of Along-Isopycnal Upwelling and Diapycnal Velocity at a Shelfbreak Front. J. Phys. Oceanogr., 34, 543–565. doi: 10.1175/2514.1 Available at: https://doi.org/10.1175/2514.1 This Article is brought to you for free and open access by the Graduate School of Oceanography at DigitalCommons@URI. It has been accepted for inclusion in Graduate School of Oceanography Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. Authors John A. Barth, Dave Hebert, Andrew C. Dale, and David S. Ullman This article is available at DigitalCommons@URI: https://digitalcommons.uri.edu/gsofacpubs/337 MARCH 2004 BARTH ET AL. 543 Direct Observations of Along-Isopycnal Upwelling and Diapycnal Velocity at a Shelfbreak Front* JOHN A. BARTH College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon DAVE HEBERT Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island ANDREW C. DALE College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon DAVID S. ULLMAN Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island (Manuscript received 18 November 2002, in ®nal form 2 September 2003) ABSTRACT By mapping the three-dimensional density ®eld while simultaneously tracking a subsurface, isopycnal ¯oat, direct observations of upwelling along a shelfbreak front were made on the southern ¯ank of Georges Bank.
    [Show full text]
  • Gyre-Scale Deep Convection in the Subpolar North Atlantic Ocean During Winter 2014–2015
    PUBLICATIONS Geophysical Research Letters RESEARCH LETTER Gyre-scale deep convection in the subpolar North 10.1002/2016GL071895 Atlantic Ocean during winter 2014–2015 Key Points: A. Piron1 , V. Thierry1 , H. Mercier2 , and G. Caniaux3 • Exceptional heat loss caused exceptional convection at subpolar 1Ifremer, Laboratoire d’Océanographie Physique et Spatiale, UMR 6523 CNRS-IFREMER-IRD-UBO, Plouzané, France, 2CNRS, – gyre scale during winter 2014 2015 ’ 3 • Exceptionally deep mixed layers Laboratoire d Océanographie Physique et Spatiale, UMR 6523 CNRS-IFREMER-IRD-UBO, Plouzané, France, Centre National directly observed south of Cape de Recherches Météorologiques, UMR 3589 Météo-France-CNRS, Toulouse, France Farewell (1700 m) and in the Irminger Sea (1400 m) • This exceptional convection was Abstract Using Argo floats, we show that a major deep convective activity occurred simultaneously in the favored by and enhanced the cold Labrador Sea (LAB), south of Cape Farewell (SCF), and the Irminger Sea (IRM) during winter 2014–2015. anomaly that developed recently in the North Atlantic Ocean Convection was driven by exceptional heat loss to the atmosphere (up to 50% higher than the climatological mean). This is the first observation of deep convection over such a widespread area. Mixed layer depths Supporting Information: exceptionally reached 1700 m in SCF and 1400 m in IRM. The deep thermocline density gradient limited the • Supporting Information S1 mixed layer deepening in the Labrador Sea to 1800 m. Potential densities of deep waters were similar in the À three basins (27.73–27.74 kg m 3) but warmer by 0.3°C and saltier by 0.04 in IRM than in LAB and SCF, Correspondence to: meaning that each basin formed locally its own deep water.
    [Show full text]
  • OCEAN SUBDUCTION Show That Hardly Any Commercial Enhancement Finney B, Gregory-Eaves I, Sweetman J, Douglas MSV Program Can Be Regarded As Clearly Successful
    1982 OCEAN SUBDUCTION show that hardly any commercial enhancement Finney B, Gregory-Eaves I, Sweetman J, Douglas MSV program can be regarded as clearly successful. and Smol JP (2000) Impacts of climatic change and Model simulations suggest, however, that stock- Rshing on PaciRc salmon over the past 300 years. enhancement may be possible if releases can be Science 290: 795}799. made that match closely the current ecological Giske J and Salvanes AGV (1999) A model for enhance- and environmental conditions. However, this ment potentials in open ecosystems. In: Howell BR, Moksness E and Svasand T (eds) Stock Enhancement requires improvements of assessment methods of and Sea Ranching. Blackwell Fishing, News Books. these factors beyond present knowledge. Marine Howell BR, Moksness E and Svasand T (1999) Stock systems tend to have strong nonlinear dynamics, Enhancement and Sea Ranching. Blackwell Fishing, and unless one is able to predict these dynamics News Books. over a relevant time horizon, release efforts are Kareiva P, Marvier M and McClure M (2000) Recovery not likely to increase the abundance of the target and management options for spring/summer chinnook population. salmon in the Columbia River basin. Science 290: 977}979. Mills D (1989) Ecology and Management of Atlantic See also Salmon. London: Chapman & Hall. Ricker WE (1981) Changes in the average size and Mariculture, Environmental, Economic and Social average age of PaciRc salmon. Canadian Journal of Impacts of. Salmonid Farming. Salmon Fisheries: Fisheries and Aquatic Science 38: 1636}1656. Atlantic; Paci\c. Salmonids. Salvanes AGV, Aksnes DL, FossaJH and Giske J (1995) Simulated carrying capacities of Rsh in Norwegian Further Reading fjords.
    [Show full text]
  • Experimental Investigation of Theory for Stratified Ocean Convection
    Experimental investigation of theory for stratified ocean convection Chris Sonekan 1 Introduction The ocean forms over seventy percent of the surface area of the earth. It is endowed with rich marine life of immense biological diversity and other interesting phenomena. Just as the atmosphere is inextricably linked to the oceans, so also man and his activities are connected with the oceans in a sort of symbiotic relationship. The teeming biological diversity and water have supplied some of the resources needed for the survival of man. On the other hand, the activities of man produce nutrients and minerals required by marine organisms lower on the food chain. Oceans also have a kind of thermostatic control on climate as they absorb and release water and carbon dioxide, as well as other gases. However, not all characteristic features of the ocean are well understood. Between the warm well-mixed surface layer and the cold waters of the main body of the ocean is the thermocline, the zone within which temperature decreases markedly with depth [1]. The density of the oceans is dependent mainly on pressure, temperature, and salinity. The ocean has a unique density structure. The density field varies significantly in all three spatial directions, with the largest variations occurring in the upper two kilometers. This suggests stratification of density and other properties. A complete dynamical theory should explain and predict the three-dimensional variation of the density and velocity field. “This is the problem of the thermocline. It is non-linear and difficult" [2]. In addition to this, “the three-dimensional structure of the oceans is complex and very poorly understood" [1].
    [Show full text]
  • Variability of Circulation Features in the Gulf of Lion NW Mediterranean Sea
    Oceanologica Acta 26 (2003) 323–338 www.elsevier.com/locate/oceact Original article Variability of circulation features in the Gulf of Lion NW Mediterranean Sea. Importance of inertial currents Variabilité de la circulation dans le golfe du Lion (Méditerranée nord-occidentale). Importance des courants d’inertie Anne A. Petrenko * Centre d’Océanologie de Marseille, LOB-UMR 6535, Faculté des Sciences de Luminy, 13288 Marseille cedex 09, France Received 9 October 2001; revised 5 July 2002; accepted 18 July 2002 Abstract ADCP data from two cruises, Moogli 2 (June 1998) and Moogli 3 (January 1999), show the variability of the circulation features in the Gulf of Lion, NW Mediterranean Sea. The objective of the present study is to determine whether the hydrodynamic features are due to local forcings or seasonal ones. During both cruises, the Mediterranean Northern Current (NC) is clearly detected along the continental slope and intrudes on the eastern side of the shelf. East of the gulf, its flux is ~2 Sv both in June and January in opposition to previous literature results. Otherwise, the NC characteristics exhibit usual seasonal differences. During the summer, the NC is wider (35 km), shallower (~200 m), and weaker (maximum currents of 40–50 cm s–1) than during the winter (respectively, 28 km, 250–300 m, 70 cm s–1). Moreover the NC is tilted vertically during the winter, following the more pronounced cyclonic dome structure of that season. Its meanders are interpreted as due to baroclinic instabilities propagating along the shelf break. Other circulation features are also season-specific. The summer stratification allows the development, after strong wind variations, of inertial currents with their characteristic two-layer baroclinic structure.
    [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]
  • The Dynamics of Nutrient Enrichment and Primary Production Related to the Recent Changes in the Ecosystem of the Black Sea
    IAEA-SM-354/29 XA9951900 THE DYNAMICS OF NUTRIENT ENRICHMENT AND PRIMARY PRODUCTION RELATED TO THE RECENT CHANGES IN THE ECOSYSTEM OF THE BLACK SEA YILMAZ A., YAYLA M., and SALlHOGLU I., Middle East Technical University, Institute of Marine Sciences, P.CBox 28, 33731, Erdemli-icel, Turkey E. MORKOg, Turkish Scientific and Technological Research Council (TUBITAK), Marmara Research Center, P.O.Box 21, 41470, Gebze-Kocaeli, Turkey Abstract During the spring period of 1998, light penetrated into the upper 25-35m, with an attenuation coefficient varying between 0.1 and 0.5 m"1. The chlorophyll-a (Chl-a) concentrations for the euphotic zone ranged from 0.2 to 1.4 ug I"1. Coherent sub-surface Chl-a maxima were formed near the base of the euphotic zone and a secondary one was located at very low level of light in the Rim Current region. Production rates varied between 450 and 690 mgC/m2/d in this period. The chemocline boundaries and the distinct chemical features of the oxic/anoxic transition layer (the so-called suboxic zone) are all located at specific density surfaces; however, they exhibited remarkable spatial variations both in their position and in their magnitude. Bioassay experiments (using extra NO3, NH4, PO4 and Si) performed during Spring 1998 cruise showed that under optimum light conditions the phytoplankton population is nitrate limited in the open waters. Phosphate seems to control the growth in the Rim Current regions of the southern Black Sea. Si concentration also influenced the phytoplankton growth since the majority of the population was determined as diatom.
    [Show full text]
  • The in Uence of the Ambient Ow on the Spreading of Convected Water
    Journalof MarineResearch, 56, 107–139, 1998 The inuence ofthe ambient ow onthe spreading ofconvected water masses bySonya Legg 1,2 andJohn Marshall 3 ABSTRACT Weinvestigatethe in uence of a cyclonicvortical owonthelateral spreading of newlymixed uidgenerated through localized deep convection. Localized open ocean deep convection often occurswithin such a cyclonicgyre circulation, since the associated upwardly domed isopycnals and weakerstrati cation locally precondition the ocean for deeper convection. In theabsence of ambient ow,localizedconvection has been shown to result in stronglateral uxesof buoyancygenerated by baroclinicinstability, sufficient to offset the local surface buoyancy loss and limit the density anomalyof theconvectively generated water mass. Herewe examine the consequences of acyclonicambient owonthisbaroclinic instability and lateralmixing. T oisolatethe in uence of thecirculation on this later stage of localized convection, weparameterize the convective mixing by the introduction of baroclinic point vortices (‘ ‘hetons’’) in atwo-layerquasi-geostrophic model, and prescribe the initial owbyapatchof constantpotential vorticity.Linear stability analysis of the combined system of pre-existing cyclonic vortex and convectivelygenerated baroclinic vortex indicates scenarios in which the pre-existing cyclonic circulationcan modify the baroclinic instability. Numerical experiments with the two-layer QG modelshow that the effectiveness of the lateral heat uxescan be stronglydiminished by the action ofthepre-existing circulation, thereby increasing the density anomaly of theconvected water mass. 1.Introduction Inseveral recent studies of localized open ocean deep convection (Legg and Marshall, 1993;Send and Marshall, 1995; Visbeck et al., 1996; Ivey et al., 1995;Coates et al., 1995; Brickman,1995; Legg et al., 1996)it has become clear that baroclinic instability of the localizedconvection site leads to signi cant lateral uxesof buoyancy as uidis transportedaway from andinto the convectingsite by niteamplitude eddies.
    [Show full text]
  • Large Halocline Variations in the Northern Baltic Proper And
    Large halocline variations OCEANOLOGIA, 48 (S), 2006. pp. 91–117. in the Northern Baltic C 2006, by Institute of Proper and associated Oceanology PAS. meso- and basin-scale KEYWORDS processes* Baltic Sea Gulf of Finland Halocline Currents Mesoscale eddies Juri¨ Elken1 Pentti Malkki¨ 2 Pekka Alenius2 Tapani Stipa2 1 Marine Systems Institute, Tallinn University of Technology, Akadeemia tee 21, EE–12618 Tallinn, Estonia; e-mail: [email protected] 2 Finnish Institute of Marine Research, Dynamicum, Erik Palm´enin aukio 1, PO Box 2, FIN–00561 Helsinki, Finland Received 5 December 2005, revised 12 May 2006, accepted 15 May 2006. Abstract The Northern Baltic Proper is a splitting area of the Baltic Sea saline water route towards the two terminal basins – the Gulf of Finland and the Western Gotland Basin. Large halocline variations (vertical isopycnal displacements of more than 20 m, intra-halocline current speeds above 20 cm s−1) appear during and following SW wind events, which rapidly increase the water storage in the Gulf of Finland and reverse the standard estuarine transport, causing an outflow in the lower layers. In the channel of variable topography, basin-scale barotropic flow pulses are converted into baroclinic mesoscale motions such as jet currents, sub-surface eddies and low- frequency waves. The associated dynamics is analysed by the results from a special mesoscale experiment, routine observations and numerical modelling. * This study has been partly supported by grants Nos 2194 and 5868 from the Estonian Science Foundation. The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 92 J.
    [Show full text]