Lecture Notes in Oceanography

lecture notes on physical oceanography and what is oceanography and why is it important. what is oceanography worksheet answers pdf free download
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Lecture Notes in Oceanography by Matthias Tomczak Flinders University, Adelaide, Australia School of Chemistry, Physics & Earth Sciences http://www.es.flinders.edu.au/mattom/IntroOc/index.html 1996-2000 Contents Introduction: an opening lecture General aims and objectives Specific syllabus objectives Convection Eddies Waves Qualitative description and quantitative science The concept of cycles and budgets The Water Cycle The Water Budget The Water Flux Budget The Salt Cycle Elements of the Salt Flux Budget The Nutrient Cycle The Carbon Cycle Lecture 1. The place of physical oceanography in science; tools and prerequisites: projections, ocean topography The place of physical oceanography in science The study object of physical oceanography Tools and prerequisites for physical oceanography Projections Topographic features of the oceans Scales of graphs Lecture 2. Objects of study in Physical Oceanography The geographical and atmospheric framework Lecture 3. Properties of seawater The Concept of Salinity Electrical Conductivity Density Lecture 4. The Global Oceanic Heat Budget Heat Budget Inputs Solar radiation Heat Budget Outputs Back Radiation Direct (Sensible) Heat Transfer Between Ocean and Atmosphere Evaporative Heat Transfer The Oceanic Mass Budget Lecture 5. Distribution of temperature and salinity with depth; the density stratification Acoustic Properties Sound propagation Nutrients, oxygen and growth-limiting trace metals in the ocean Lecture 6. Aspects of Geophysical Fluid Dynamics Classification of forces for oceanography Newton's Second Law in oceanography ("Equation of Motion") Inertial motion Geostrophic flow The Ekman Layer Lecture Notes in Oceanography by Matthias Tomczak 2 Upwelling Lecture 7. Thermohaline processes; water mass formation; the seasonal thermocline Circulation in Mediterranean Seas Lecture 8. The ocean and climate El Niño and the Southern Oscillation (ENSO) Lecture 9. Waves Wave Classification Description of Waves Normal dispersion Nondispersive waves Anomalous dispersion Waves of finite amplitude Short waves (deep water waves) Statistical description of waves Lecture 10. Long Waves (shallow water waves) Tsunamis Seiches Internal Waves Lecture 11. Tides Description of tides The Tide-Generating Forces Main tidal periods Tidal Classification Shape of the Tidal Wave Co-oscillation tides Lecture 12. Estuaries Salt wedge estuary Highly stratified estuary Slightly stratified estuary Vertically mixed estuary Inverse estuaries Intermittent estuaries Lecture 13. Oceanographic instrumentation Platforms Research vessels Moorings Satellites Submersibles Towed vehicles Floats and drifters Measurements of hydrographic properties Reversing thermometers Nansen and Niskin bottles CTDs Multiple water sample devices Thermosalinographs Remote sensors Measurements of dynamic properties Current meters Lecture Notes in Oceanography by Matthias Tomczak 3 Wave measurements Tide gauges Remote sensors Shear probes Lecture Notes in Oceanography by Matthias Tomczak 4 Introduction: an opening lecture For many years the Flinders University of South Australia has offered a first year topic Earth Sciences in two parts. The first semester topic, Earth Sciences 1A, covered the place of the Earth in the universe, aspects of geology, and an introduction into geophysics and hydrology. Meteorology and oceanography were covered in the second semester topic Earth Sciences 1B. Beginning in 2000 the two topics are delivered as Earth Sciences 1, which continues as the first semester topic with identical content, and Marine Sciences 1 as the second semester topic. Marine Sciences 1 still contains extensive material on meteorology and physical oceanography but also contains an elementary introduction to aspects of marine biology. These notes represent the topic content for physical oceanography. In addition, two introductory lectures place the atmospheric and oceanographic aspects of the topic in the context of the exact sciences; they are an abbreviated version of the first two lectures given at the beginning of the semester. General aims and objectives  To give students practical experience in general scientific methodology including laboratory and field-based experimentation and scientific report writing.  To help students develop an understanding of the unifying principles and processes which are critical in understanding both the evolution and behaviour of the planet Earth, with a particular focus on aspects relating to the atmosphere and the ocean.  To encourage critical thinking and assist in the development of both quantitative and qualitative problem solving skills.  To assist in the development of communication and team work skills in a technical environment. Specific syllabus objectives  To provide an overview of the processes which determine the state of the atmosphere and the ocean and their dynamics.  To describe our planetary environment and the governing cycles and processes which control its behaviour.  To describe the processes and phenomena which directly affect the nature and behaviour of the "fluid" Earth, namely, the composition of the atmosphere and of seawater, the balance of forces which controls winds, ocean currents and waves in both media, and their role in climate.  To describe the natural atmospheric and oceanic processes which impact on use of the Earth's resources including industrial, commercial and recreational use and conservation.  To let students appreciate the importance of scientific understanding of physical processes in ocean and atmosphere and the forces behind them for environmental pollution and management problems. What will we learn today? 1. The environment Earth is shaped by the presence of life. 2. Understanding the environment means understanding the interaction between biosphere, geosphere, hydrosphere and atmosphere. Lecture Notes in Oceanography by Matthias Tomczak 5 3. Earth sciences study the three non-living components of this interactive system. 4. Geosphere, hydrosphere and atmosphere are fluids in motion; their main difference is their viscosity. 5. As fluids in motion they exhibit some common features. Examples are convection, eddies, and energy transport through wave propagation. The sciences of meteorology and oceanography study the results of these processes in the atmosphere and in the ocean. The living and non-living components of the interactive system Earth are shaped through interaction - even the structure of its non-living components is determined by the presence of life. This is most pronounced for the atmosphere; its composition is determined by the presence of life. In the absence of life the most important gas in the atmosphere is carbon dioxyde (CO ) which makes the 2 atmosphere toxic for higher life forms. Life on Earth evolved through the activity of bacteria which reduced CO 2 levels to tolerable concentrations and produced oxygen (O ) in the process. 2 Examples for this planetary state are Venus and Mars; both have an atmosphere with a CO content of 95%. 2 The present make-up of Earth's atmosphere is maintained by continuous interplay between reduction of CO and 2 production of O by plants and reduction of O and production of CO by animals and humans. 2 2 2 Without the presence of life the atmosphere would not maintain its composition. The earth's atmosphere is therefore said to be in "dynamic equilibrium", while in the absence of life atmospheres are said to be in "dead equilibrium". In the 1960s the British chemist James Lovelock was engaged by the space agency NASA of the USA in its search for extra-terrestrial life, particularly on Mars and Venus. Noticing the large difference in atmospheric composition between Earth and the other two planets - and in particular the fact that the atmospheres of Venus and Mars are in a dead equilibrium while the atmosphere of Earth is in a dynamic equilibrium, which without life would immediately revert to the dead equilibrium - he and Lynn Margulis, a microbiologist from the USA, developed the gaea concept or hypothesis. They point out that the presence of life has far reaching consequences for the planet as a whole. The development of forest, for example, reduces the Lecture Notes in Oceanography by Matthias Tomczak 6 albedo (the reflectivity of the Earth's surface) considerably. As a result the Earth is several degrees warmer than it would be without the presence of life. The gaea hypothesis therefore states that the planet Earth is a living organism itself, and oceans, land, air and all lifeforms are different organs of a living body. Whether one accepts the gaea hypothesis in its extreme formulation or not, it is beyond doubt that the gaea hypothesis is a scientific hypothesis and can withstand the many attempts to turn it into a "new age religion". The fact remains that Earth as it is today is determined in its physical state (the distribution of water and ice, the composition of the atmosphere, the weathering processes of rocks, and much more) by the presence of life. Modern science has been extremely successful in explaining the Earth by dividing it into compartments which can be studied separately. Modern science divides the Earth into living and non-living compartments. In reality Earth is an interactive system in which all elements are related and influence each other. Not all cultures see the Earth that way; but the success of modern science shows that dividing the Earth into independent compartments can be one way of understanding many aspects of it. This topic will follow the tradition of modern science; but students should keep in mind that the system Earth is more than the sum of independent parts. It is not well equipped to approach Earth as an interrelated organism. This "western" way of analyzing and understanding the world is also reflected in the structure of western languages, which compose sentences through subject-object relationships wich always establish a clear master-servant hierarchy. A sentence such as: "The engineer improves the environment" says that there is an environment, of which the engineer is not a part; he is the master of the environment. Other cultures do not divide the world into compartments, and their languages describe the world in totally different ways. There are many examples of American Indian languages which do not know the concept of subject and object; and if the Australian Aborigines say: "We are the land, and the land is us." they express their view that dividing the world into compartments can make you loose sight of important interactions between the various "spheres." Keep in mind that meteorology and oceanography are just two compartments of a system with many living and non-living interactive components and that studying processes through meteorology and oceanography is only one way of studying the world. Nevertheless, the success of western science in explaining how the physical world works should not be dismissed lightly, and we shall follow its methods. Lecture Notes in Oceanography by Matthias Tomczak 7 With this proviso, let us proceed to the study of physical processes in nature and look at three examples: convection, eddies and waves. Convection A fluid can be stratified, which means that its density can vary. For a fluid to be in a stable state, its density has to decrease from the bottom upwards to the top. Convection occurs when this condition is not satisfied. Instability occurs when the density of the fluid is higher at the top than at the bottom. The lighter fluid then rises to the top, the denser fluid sinks to the bottom until stability is achieved. The resulting movement is called convection. Convection represents a balance of forces between gravity and friction. A third force is required to establish the initial instability. The space and time scales of convection depend on the viscosity of the fluid. The examples given in the figures show convection in the "solid" earth, atmosphere and ocean. Heating from the Earth's core drives convection in the upper mantle. This convection is extremely slow; the speed with which material in the Earth's crust spreads from the mid-ocean ridges is of the order of several cm per year. Nevertheless, it is evident that the same forces which drive convection in the atmosphere and in the ocean are present in the "solid" earth as well. Lecture Notes in Oceanography by Matthias Tomczak 8 Convection in the atmosphere, observed through cloud formation and rain development in the equatorial Indian Ocean. In the atmosphere convection is driven by the ocean or the land surface, which receive heat from the sun during the day and in return heat the air from below. This lowers the air density near the ground and forces the air to rise. When a convection cell develops, the air rises in a region of about 10 kilometres. Cooling of the rising air causes condensation, so the vertical extent of the convection cell becomes visible as a tall cumulonimbus cloud. Sinking of air occurs around the cloud, so the outer region of the convection cell remains cloud free. As the air rises higher and higher (to 10 km height or more) the condensation turns into rain, which falls out as a heavy downpour from the centre of the convection cell. Convective rain accounts for most of the rainfall in the tropics. It is very intense when it falls but very patchy in space and not long lasting in time. In the ocean convection occurs when the water at the sea surface is cooled. This causes an increase in water density at the surface and forces the water to sink. Because intense cooling is required to generate oceanic convection, the process occurs mainly in polar regions and is not as easily observed as atmospheric convection in the tropics. The photo shows a synthetic aperture radar image from the ERS-1 satellite over the Greenland Sea during February 1992. The image is about 6.4 km wide in both directions. Ice-covered water is grey/white, ice-free water is black. A noticeable feature is the patchiness of the ice. Ice-covered regions are about 500 m in diameter and surrounded by ice-free regions of similar size. This is interpreted as a result of convection: When a convection cell develops, water sinks with great speed. Water is drawn in to fill the void and accumulates ice floes over the regions of sinking water. Rising water motion occurs at the perimeter of the convection cells. This water is warmer than the cooled surface Lecture Notes in Oceanography by Matthias Tomczak 9 water and melts the ice where it comes to the surface. This produces a patchwork of ice-covered and ice-free regions. Eddies Eddies are the results of instabilities in fluid motion. They involve a somewhat more complicated balance of forces than what we intend to study here, but they are such common features that it is instructive to look at some examples and compare again the "solid" earth, the atmosphere and the ocean. The similarity of eddies in the atmosphere and in the ocean will be discussed in more detail in Lecture 1 later in this course. In this context it is worth noting that the "solid" earth undergoes very similar processes, although on much longer time scales. In the atmosphere and in the ocean eddies can be generated from wind shear or current shear, ie when the fluid moves in the same direction but with different speed. The high viscosity of the "solid" earth often prevents eddy formation even when there is shear in the movement of the mantle or crust. Folding is observed instead. A composite satellite image of cloud coverage over the earth. Several large eddies are clearly visible, among them a tropical cyclone (A) and a tropical depression (B) which may develop into a cyclone. An example of a vortex street in water, produced in a laboratory experiment. The eddies develop as a current passes an obstacle. Similar eddies are observed in the ocean behind islands and in the atmosphere behind high mountains. Lecture Notes in Oceanography by Matthias Tomczak 10 An example of strong bending of originally horizontal layers in the Canadian Rocky Mountains. If the forcing continues long enough the layers will eventually fold over and attain a shape resembling the water swirls in eddies. Waves Waves are a balance of forces where the forces vary periodically in strength and produce periodic fluid motion as a result. They are an efficient means to transport energy over large distances. There will be ample opportunity later in this topic to study the interaction of forces in wave motion in detail. At this point we use waves as another example which demonstrates again that the "solid" earth, the atmosphere and the ocean are three different types of fluid in motion. Movement of the earth during the 1906 earthquake of San Francisco. The instrument shows wave motion produced by the earthquake. The waves traversed the earth's mantle and core to arrive at Göttingen, Germany, where this record was taken. Earthquakes also produce waves that travel along the earth's surface. These take much longer and did not arrive in Göttingen until after this record was obtained. When they arrived, the instrument went off-scale. Lecture Notes in Oceanography by Matthias Tomczak 11 Cloud patterns in which clouds are organised in bands are not an unusual sight. The photo shows a cloud pattern produced by an internal wave. The air rises with the crest of the wave, cooling in the process, which produces condensation (cloud formation). It sinks in the troughs, causing warming and evaporation of the cloud moisture. The wave crests then become visible as cloud bands. The photo was taken near Mount Lawson (30 km west of Brisbane, Australia) and the wave was travelling towards Brisbane city, while it was a fine still day on the ground. Surface waves are among the most elementary and most easily observed features of ocean dynamics, so not much comment is needed here. Later lectures in this topic will explore other types of waves that are not as easily appreciated as the ocean's surf. There are many ways in which waves can be generated. The examples shown in the figures represent different force balances. What they have in common is that their properties can be understood and their behaviour predicted on the basis of the Laws of Physics. What did we learn today? 1. The environment Earth is shaped by the presence of life. 2. Understanding the environment means understanding the interaction between biosphere, geosphere, hydrosphere and atmosphere. Lecture Notes in Oceanography by Matthias Tomczak 12 3. Earth sciences study the three non-living components of this interactive system. 4. Geosphere, hydrosphere and atmosphere are fluids in motion; their main difference is their viscosity. 5. As fluids in motion they exhibit some common features: convection, eddies, energy transport through wave propagation (among others). What will follow in this topic? In today's world human activity - be it industrial, commercial or recreational - will shape our environment more than ever before. Active environmental management on a global scale has become a necessity. Human activity cannot override the Laws of Nature. Active environmental management has to be based on these laws, it cannot succeed if it attempts to oppose them. The sciences of meteorology and oceanography investigate and explain how the Laws of Physics determine processes in the atmosphere and oceans. They form the basis for any environmental management. Responsible environmental management takes into account many factors, such as economical, social and historical considerations; but it cannot ignore the Laws of Physics. Lecture Notes in Oceanography by Matthias Tomczak 13 Qualitative description and quantitative science For many years the Flinders University of South Australia has offered a first year topic Earth Sciences in two parts. The first semester topic, Earth Sciences 1A, covered the place of the Earth in the universe, aspects of geology, and an introduction into geophysics and hydrology. Meteorology and oceanography were covered in the second semester topic Earth Sciences 1B. Beginning in 2000 the two topics are delivered as Earth Sciences 1, which continues as the first semester topic with identical content, and Marine Sciences 1 as the second semester topic. Marine Sciences 1 still contains extensive material on meteorology and physical oceanography but also contains an elementary introduction to aspects of marine biology. These notes represent the topic content for physical oceanography. In addition, two introductory lectures place the atmospheric and oceanographic aspects of the topic in the context of the exact sciences; they are an abbreviated version of the first two lectures given at the beginning of the semester. The topic for today: The concept of cycles and budgets Meteorology and oceanography are physical sciences which aim to understand processes in the environment and describe, analyze and predict them in a quantitative manner. A common way of expressing processes quantitatively is through the concept of cycles and budgets. On time scales of geological history, all processes on earth are based on a constant reservoir of materials. The forms in which the materials are present change constantly. In a state of equilibrium this change has to be cyclic. The concept of cycles expresses this principle of equilibrium in a qualitative manner. The concept of budgets makes it quantitative by giving rates of change between different states in the cycle. This lecture discusses four examples. The Water Cycle The earth is the only planet in the solar system where liquid water is found on the surface. Water is the only substance which, under the ranges of pressure and temperature experienced on earth, is present in solid, liquid and gaseous phase. The water cycle is therefore of fundamental importance to many processes unique to earth. In comparison, the outer planets of our solar system (Saturn, Jupiter, Uranus, Neptune and Pluto) and their moons are too cold to contain water in any form other than ice, the inner planets (Mercury and Venus) are too hot to hold water in any form other than water vapour, and Mars is presently too cold but may have had liquid Lecture Notes in Oceanography by Matthias Tomczak 14 water on its surface at some point in its history. In the current stage of development of the solar system Earth is the only planet that contains water in all its phases. Like many other cycles, the water cycle links processes acting in the living and non-living world: Precipitation and oceanic evaporation link ocean and atmosphere; evaporation from land and transpiration from vegetation link the atmosphere with the biosphere. A sketch of the water cycle. Water cycles from the ocean to the atmosphere through evaporation, is transported in condensed form as clouds with the winds and returns to land and water as precipitation. The biosphere plays an important role in the water cycle. Evapo-transpiration from plants is the major component of the water cycle's pathway from the land to the atmosphere; direct evaporation from land is comparatively small. Evaporation from the sea, however, is quite significant. The link between land and ocean is represented by run-off from rivers. This closes the water cycle. In the context of meteorology and oceanography the effect of the biosphere is quantitatively expressed as a single process, evapo-transpiration. The water cycle then describes a basic component of the combined system ocean-atmosphere. Associated with every cycle is a budget. Cycles represent a qualitative description of processes, budgets turn them into quantitative statements. We distinguish between static budgets, which summarize how much of a particular material is available and how it is distributed between the different compartments, and dynamic budgets, which quantify how rapidly the material is moved between compartments. Cycles define the process; budgets allow answers to questions such as; "How is the water cycle affected if a given percentage of the existing bushland in Western Australia is cleared and replaced by wheat farming?" The Water Budget The distribution of water on earth (the static budget); this budget shows where the water is found: 3 3 region volume (10 km ) % of total oceans 1,350,000 94.12 groundwater 60,000 4.18 ice 24,000 1.67 lakes 230 0.016 soil moisture 82 0.006 atmosphere 14 0.001 rivers 1 - Based on M. J. Lvovich: World water balance; in: Symposium on world water balance, UNESCO/IASH publication 93, Paris 1971. Lecture Notes in Oceanography by Matthias Tomczak 15 The static budget demonstrates the importance of the ice sheets to the global water cycle: Any change in the atmospheric or oceanic conditions that releases a significant part of the water that is presently stored in the ice, will produce a major shift in the water cycle. The atmosphere seems insignificant in comparison. However, the important role of the atmosphere becomes clear when the dynamic budget is considered. The Water Flux Budget The branches of the water cycle on earth (the dynamic budget); this budget shows how water moves between atmosphere and hydrosphere: 3 process amount (m per year) . 14 precipitation on ocean 3.24 10 . 14 evaporation from ocean -3.60 10 . 14 precipitation on land 0.98 10 . 14 evaporation from land -0.62 10 . 14 net gain on land = river run-off 0.36 10 The flux budget demonstrates that most of the water exchange between the compartments is between the ocean and atmosphere, so the atmosphere is an extremely dynamic element in the system despite of its small water content at any one time. The turnover of water between ocean and atmosphere over a few decades is equivalent to the total amount of water stored in the ice sheets. The Salt Cycle The salt cycle involves the ocean, the geosphere and to a very minor extent the atmosphere. Minerals are leached from rocks through flowing groundwater and surface erosion. They enter the rivers and from there the ocean where they accumulate, making sea water salty. They are removed from the water and enter the sediment by chemical action. The sediment is used to form new rock which brings the minerals back into the geosphere. Salt gets into the atmosphere as spray from wind waves. This may be carried on to land, constituting a minute pathway from sea to land in the global salt cycle. Because the salt cycle operates on such large time scales, establishing a static salt budget is of no relevance to oceanography. Elements of the Salt Flux Budget The salt cycle operates on such long scales that establishing a salt flux budget is not an important task for oceanography. The following table gives an idea of the time scales involved: element crustal abundance (%) residence time (years) some major constituents of sea salt: sodium (Na) 2.4 60,000,000 chlorine (Cl) 0.013 80,000,000 magnesium (Mg) 2.3 10,000,000 some trace constituents of sea salt: lead (Pb) 0.001 400 iron (Fe) 2.4 100 aluminium (Al) 6.0 100 Lecture Notes in Oceanography by Matthias Tomczak 16 The concept of salinity is the topic of lecture 3. The Nutrient Cycle Nutrients are essential for plant and animal life. They undergo a terrestrial and an oceanic cycle. On land nutrients are taken up from the soil by plants and return to the soil by decomposition of dead organic matter. This is a closed cycle on a relatively short time scale, determined by the process of decomposition and life spans of plants, animals and humans. In developed human societies it is only broken by the uptake of nutrients by populations of large cities, which do not return the nutrients to the land but dispose of them in sewage systems. The resulting nutrient loss in agriculture is compensated by the importation of mineral fertiliser from the reservoir of minerals in the geosphere. A sketch of the nutrient cycle. The natural cycle consists of the recycling of decaying organic matter into landbased lifeforms on land and nutrient supply for marine from upwelling in the ocean. The development of human civilisation introduces the additional elements of sewage disposal and fertiliser application. This human influence introduces a link with a nutrient cycle of a much longer time scale, determined by the formation of mineral deposits. The situation is similar to the situation discussed with the carbon cycle below but does not have the same immediate consequences; the increase of nutrients available for the fast nutrient cycle on which life processes and agriculture depend is very gradual, and much of the mineral input is removed from the rapid nutrient cycle through the oceanic component. In the ocean nutrient uptake by plants occurs in the surface layer reached by sunlight where photosynthesis takes place. Most nutrients are removed from the euphotic zone and transferred to the deeper ocean as dead organisms sink to the ocean floor, where they leave the rapid nutrient cycle. In the deeper layers organic matter is remineralized, i.e. nutrients are brought back into solution. Thus, the ocean cannot support highly productive ecosystems except where nutrients are returned to the euphotic zone from below in so called upwelling regions. The nutrient cycle is discussed in more detail in lecture 5, upwelling in lecture 6. The Carbon Cycle The carbon cycle operates naturally on two vastly different time scales. It involves the ocean, the atmosphere, the geosphere and the biosphere. Lecture Notes in Oceanography by Matthias Tomczak 17 A sketch of the carbon cycle. A static budget would show that the largest amount of carbon is contained in the deepr layers of the geosphere (fossil fuels and carbonate sediment). The dynamic budget would show that it is stored there, while all day to day exchange of carbon between the compartments is active between the biosphere, the atmosphere and the upper ocean and continental layer. The uptake and burning of fossil fuels in power stations and cars establishes a link between the slow and fast cycles and leads to an increase of carbon dioxide in the atmosphere and in the ocean and a reduction in the geosphere. On the geological time scale carbon is released into the atmosphere and ocean through the weathering of carbonate rocks such as limestones. It returns to this vast storage reservoir as new rocks are formed through sediment deposition. On the much shorter climate timescale carbon is exchanged between the atmosphere, the ocean and living and dead organisms. The carbon cycle includes both timescales, but for most practical purposes the carbon budget and the carbon flux budget usually exclude the geological timescale. This separation between the timescales has been significantly disturbed through the burning of fossil fuel. This adds carbon dioxide to the atmosphere and increases its ability to retain heat energy received from the sun (the greenhouse effect). The following tables give some current estimates for the carbon budget and the carbon flux budget. The carbon budget 15 amount (Gt carbon; 1 Gt = 10 g) region before anthropogenic change after anthropogenic change land plants 610 550 soil and humus 1,500 no change atmosphere 600 750 (+3.4 per annum) uper ocean 1,000 1,020 (+0.4 per annum) marine life 3 no change dissolved organic carbon 700 no change mid-depth and deep ocean 38,000 38,100 (+1.6 per annum) Lecture Notes in Oceanography by Matthias Tomczak 18 The carbon flux budget Balancing sub-budgets are identified by (a) - (d). 15 amount (Gt carbon per year; 1 Gt = 10 g) from to natural anthropogenic atmosphere land plants 100 (a) ocean 74 (d) 18 land plants atmosphere 50 (a) soil and humus 50 (a) soil and humus atmosphere 50 (a) deforestation atmosphere about 1.9 fossil fuel atmosphere about 5.4 ocean sink upper ocean 0.4 mid-depth and deep 1.6 ocean rivers ocean 0.8 upper ocean atmosphere 74 (d) 16 marine life about 40 (b) mid-depth and deep 90 (c) 5.6 ocean marine life upper ocean about 30 (b) mid-depth and deep 4 (b) ocean dissolved organic carbon 6 (b) mid-depth and deep dissolved organic carbon 6 (c) ocean mid-depth and deep upper ocean 100 (c) ocean sediment 0.13 What did we learn today? 1. The state of the environment is determined by a balance of forces. Defining several cycles, such as the water cycle, the salt cycle, the nutrient cycle and the carbon cycle, is a useful way of describing the equilibrium which results from the balance of forces. 2. The concept of cycles helps to understand the world; but to manage the environment and avoid mistakes the concept has to be turned into quantitative measurement. Budgets and flux budgets turn the concept of cycles into quantitative statements. Lecture Notes in Oceanography by Matthias Tomczak 19 Lecture 1 The place of physical oceanography in science; tools and prerequisites: projections, ocean topography The atmosphere and the ocean are both fluids in turbulent motion and follow the same physical laws. The Flinders University of South Australia recognises this by presenting meteorology and oceanography in the topic Marine Sciences 1 as a unit. The following notes correspond roughly to the oceanography content of Marine Sciences 1. A variety of textbooks offers coverage of physical oceanography at an introductory level. Most of these include a description of all aspects of marine sciences (i.e. including marine biology, geology and chemistry). Most are useful reference texts for physical oceanography. Textbooks which cover only physical oceanography are usually much more detailed in their coverage than what is needed in an introductory course, but students with particular interest in physical oceanography aspects of earth sciences are encouraged to consult them as additional reference books. The classification number for physical oceanography in the Dewy classification system is 551.46; the easiest way to find what the library has to offer in this field is to walk up to the shelves labelled 551.46 and browse through the books. The place of physical oceanography in science Physical oceanography occupies a unique place amongst all science disciplines because it has strong interactions with a large number of other sciences of very different characteristics. Universities usually follow one of two models in teaching physical oceanography. The first model emphasises the relationship between physical oceanography and other earth sciences disciplines: Lecture Notes in Oceanography by Matthias Tomczak 20

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