What is Oceanography?

Marine science is the study of the natural phenomena, properties and changing laws of the ocean, as well as the knowledge system related to the development and utilization of the ocean. Its research objects are the oceans that account for 71% of the earth's surface, including seawater, dissolved and suspended matter in the sea, living organisms in the ocean, seafloor sediments and lithosphere, as well as the atmospheric boundary layer and estuary coasts on the sea. Marine science has a wide range of research fields, and its main contents include basic research on marine physical, chemical, biological and geological processes, development and utilization of marine resources, and applied research on military activities at sea.

The global oceans account for about 71% of the total surface area, and the volume of the global oceans is about 1.37 billion cubic kilometers, accounting for more than 97% of the total water of the earth. If the earth's crust is a flat and smooth sphere, then it will be a "water ball" whose surface is covered by seawater more than 2600 meters deep.

Because of the integrity of the ocean itself, the complexity of the interaction of various natural processes in the ocean, and the commonality of the main research methods and means, marine science has become a very comprehensive science.

The history of mankind's understanding of the oceans began when people engaged in productive activities in coastal areas and at sea. Ancient humans already had some geographic knowledge about the ocean. But until the 1870s,

Marine science has obvious regional characteristics. Even in the same area, marine, hydrological, chemical elements, and biological distribution are different and multi-layered. Therefore, it is difficult to conduct detailed experiments on various marine phenomena and processes and their interactions in the laboratory.

Marine scientific research and scientific theory are showing an increasingly integrated trend. With the development of marine science, more and more marine phenomena have been revealed, so the division of disciplines has become more and more detailed, and the research fields have become wider and wider. In-depth research on marine phenomena and processes in recent decades has found that the branches of science are interdependent, intersecting, and infiltrating. Each branch of science can achieve significant development only in the interconnection of the entire marine science system.

The research system of modern marine science can be roughly divided into two parts: basic subject research and applied technology research. Fundamental disciplines are directly studying the natural phenomena and processes of the ocean as their research objects and exploring their development laws. Applied technology disciplines study how to use these laws of nature to serve humanity.

Natural processes that occur in the ocean can be broadly divided into four types: physical processes, chemical processes, geological processes, and biological processes according to their intrinsic properties. Each type is a system composed of many individual processes. The study of these four types of processes has accordingly formed four relatively independent branch disciplines in marine science: marine physics, marine chemistry, marine geology, and marine biology.

Ocean physics is a discipline that studies the various physical phenomena and their changing laws that occur in the ocean by the theory, technology, and methods of physics. It mainly includes physical oceanography, marine meteorology, marine acoustics, marine optics, marine electromagnetics, and estuarine and coastal zone dynamics.

Physical oceanography mainly studies various types of seawater movements (such as currents, tides, waves, planetary waves, turbulence, and the microstructure of seawater layers, etc.), the interaction between the ocean and the atmosphere and the lithosphere, and sound, light, and electricity in the ocean Phenomena and processes, and various physical methods related to ocean observations.

Marine chemistry is a discipline that studies the chemical composition, material distribution, chemical properties, and chemical processes of various parts of the ocean. The main research contents are the chemical composition, material distribution and transformation in the oceanic water layer and seafloor sedimentation, and the ocean-atmosphere boundary layer, and oceanic water bodies. Chemical problems in the development and utilization of chemical resources in marine organisms and seabed sediments. Marine chemistry includes branches of chemical oceanography and marine resource chemistry.

Marine geology is a discipline that studies the characteristics and changes of the submerged part of the earth. The main research contents are: coastal and submarine topography, the composition and formation process of marine sediments, oceanic stratigraphy, lithology, minerals, and geochemistry of ocean floor rocks, submarine crustal structure and ocean geological history, heat flux, gravity anomalies, Geophysical characteristics such as anomalies and seismic wave propagation speed. The major research topics in marine geology are the distribution and mineralization of submarine mineral resources, plate tectonics based on continental margins (including island arcs and trenches) and mid-ocean ridges, and paleoceanography.

Marine biology is a discipline that studies all life phenomena and processes and their laws in the ocean. It mainly studies the origin and evolution of life in the ocean, the classification and distribution of marine life, morphology and life history, growth and development, physiology and biochemistry, inheritance, In particular, the study of ecology, in order to clarify the relationship between the habits and characteristics of marine life and the marine environment, reveal various biological phenomena and their laws that occur in the ocean, and serve the development, utilization and development of marine biological resources. Marine biology includes branch disciplines such as biological oceanography and marine ecology.

Like other disciplines in the natural sciences, the basic branch disciplines of marine science are not only interconnected and interdependent, but also penetrate into each other, and many new branch disciplines such as marine geochemistry, marine biochemistry, marine biogeography, Paleooceanology, etc.

On the other hand, marine science research, especially in its early days, has a clear direction in natural geography, focusing on the study of regional combinations and interconnections of marine phenomena from the zonal and regional perspectives of natural geography to reveal regional characteristics, Regional environmental quality, regional differences and relationships have formed regional oceanography.

Due to the rapid development of modern science and technology and the ever-increasing development technology of marine resources, special research is required on how to apply the results of basic theoretical research to practice and solve production technology problems. In this way, a series of highly technical applied disciplines and professional technical research fields have gradually differentiated in marine scientific research.

Like marine engineering, it begins with coastal engineering that serves coastal zone development. In the second half of the 20th century, the world's population and economy grew rapidly, and human demand for protein and energy also increased sharply. Therefore, marine engineering has increased deep-sea mining, economic and biological growth, desalination and comprehensive utilization, and development of marine energy. Utilization, marine underwater engineering, marine space development, etc.

The application of marine scientific research results, due to different service objects, has also formed some relatively independent applied disciplines, such as marine hydro-meteorological forecasting, marine oceanography, fishery oceanography, military oceanography, and so on.

However, like other natural science research, any subject classification and system is not the final closed system. With the deepening and expansion of marine research, the subject classification and system of marine science will be continuously updated and developed.

Distinction between sea and ocean

The ocean is the central part of the ocean and the main body of the ocean. The total area of the world's oceans accounts for about 89% of the ocean area. The water depth of the ocean is generally over 3,000 meters, and the deepest point can reach more than 10,000 meters. The ocean is far from land and is not affected by land. Its water temperature and salinity do not change much. Each ocean has its own unique ocean current and tidal system. Ocean waters are blue and highly transparent, with few impurities in the water. There are four in the world, namely the Pacific Ocean, the Indian Ocean, the Atlantic Ocean and the Arctic Ocean.

The sea, at the edge of the ocean, is an accessory part of the ocean. The area of the sea accounts for about 11% of the ocean. The depth of the sea is relatively shallow, with an average depth ranging from a few meters to two to three kilometers. The sea is close to the continent, and the temperature, salinity, color, and transparency of the sea are affected by the land, and there are obvious changes due to the influence of the continent, rivers, climate and seasons. In summer, the sea water is warming, and the water temperature is lowering in winter; in some sea areas, the sea water is frozen. Where the river enters the sea, or in rainy seasons, the seawater will become thin. Due to the influence of land, rivers carry sediment into the sea, the coastal waters are turbid and the transparency of the seawater is poor. The sea does not have its own independent tides and currents. The sea can be divided into marginal seas, inland seas and the Mediterranean Sea. The marginal sea is not only the edge of the ocean, but also the frontier of the continent; this type of sea has extensive connections with the ocean, and is generally separated from the ocean by a group of islands. The East China Sea and South China Sea are the marginal seas of the Pacific Ocean. The inland sea, that is, the sea located inside the continent, such as the Baltic Sea in Europe. The Mediterranean Sea is a sea between several continents, and the water depth is generally deeper than the inland sea. There are nearly 50 major seas in the world. The Pacific Ocean has the most, followed by the Atlantic Ocean, and the Indian Ocean is almost the same as the Arctic Ocean.

Formation of the ocean

How is the ocean formed? Where does the seawater come from?

There is currently no final answer to this question in science, because they are linked to another universal and equally incomplete problem of the origin of the solar system.

Current research proves that some large and small nebula clusters were separated from the solar nebula about 5 billion years ago. They rotate around the sun. During the movement, they collided with each other, and some clumps combined with each other, from small to large, and gradually became the original earth. During the collision of nebula clusters, the sharp contraction under the influence of gravity, coupled with the internal radioactive element transformation, constantly heated the original earth to warm it; when the internal temperature reached a sufficiently high temperature, the ground's materials including iron and nickel began to melt. Under the action of gravity, the heavy sinks and concentrates towards the center of the earth, forming the core of the earth; the light rises, forming the crust and mantle. At high temperatures, the internal water vapor erupts with the gas and soars into the air. However, due to the gravity of the earth's center, they will not run away, only around the earth, and become a circle of gas-hydration unity.

A layer of the earth's crust located on the surface of the earth, during the process of cooling and condensing, is constantly impacted and squeezed by the violent movement inside the earth, so it becomes rugged and sometimes crushed, forming earthquakes and volcanic eruptions, lava and hot gas . At first, this happened frequently, but it gradually decreased and gradually stabilized. This process of material differentiation, which caused great turbulence and major reorganization, was completed about 4.5 billion years ago.

After the earth's crust has cooled and shaped, the earth is like a long-dried and air-dried apple, with its surface wrinkled and uneven. Mountains, plains, riverbeds, ocean basins, and various terrains are readily available.

For a long period of time, water and air coexisted with the atmosphere in the sky; dense clouds. The sky was dark, and as the earth's crust gradually cooled, the temperature of the atmosphere gradually decreased. Water and dust became condensed nodules with dust and volcanic ash, and became more water droplets. Due to uneven cooling, the air convection is violent, and thunderstorms and turbulent currents are formed. The rain is getting heavier and it has been raining for a long time. The torrential flood, through thousands of rivers and rivers, has gathered into a huge body of water, which is the primitive ocean.

Primitive ocean waters are not salty, but acidic and hypoxic. The water continuously evaporates, and the terrain repeatedly causes clouds to rain, and then falls back to the ground again, dissolving the salt in the land and seabed rocks, and constantly gathering in the seawater. After hundreds of millions of years of accumulation and integration, it has become roughly salty water. At the same time, because there was no oxygen and no ozone layer in the atmosphere, ultraviolet rays could reach the ground directly. Depending on the protection of seawater, organisms were first born in the ocean. About 3.8 billion years ago, organic matter was produced in the ocean, with low-level single-celled organisms first. In the Paleozoic, 600 million years ago, there were seaweeds, which carried out photosynthesis in the sun, produced oxygen, and slowly accumulated as a result, forming an ozone layer. At this point, the creature began to land.

In short, after the gradual increase in water and salinity, and the vicissitudes in geological history, the primitive ocean gradually evolved into today's ocean. ^[2]