OCEANOGRAPHY – AN OUTLINE BY PROF.A.BALASUBRAMANIAN Oceanography – an outline Table of Contents 1.0 Introduction 2.0 Scientific Curiosity 3.0 Oceanography -An inter-disciplinary subject 4.0 Geological Oceanography 5.0 Physical Oceanography 6.0 Biological Oceanography 7.0 Chemical Oceanography 8.0 Oceans and Climate change 9.0 Conclusion OBJECTIVES After attending this lesson, the user would be able to understand, basics of oceanography and the wide spectrum of studies carried out in the subject of oceanography. In addition, the concepts, methods, and developments of oceanography and its branches will also be understood. The role of oceanographers and the trends of research activities in the subject of oceanography will be known to progress further in this subject. 1.0 Introduction Oceanography is a science concerned with the physico-chemical characteristics of oceanic water, its depth, temperature, salinity, movements like tides, waves and currents, flora and fauna found at various zones of seas and oceans. As it deals with the distribution and processes of these water bodies, it comes under earth sciences in general. The subject deals with the physical, chemical and biological conditions of oceans. It is an inter-disciplinary subject and an emerging area for marine engineering. It is the science of seas and oceans. Ever since people started sailing the oceans, attempts have been made to map them. Ptolemy’s oldest map is an example. Ocean exploration began around 5000 B.C. with the first ocean diving and the first sailing vessels. Many advances that were made in the subject of oceanography, were all through the great ocean expeditions and explorations. 2.0 Scientific Curiosity Oceanographic exploration is a part of the subject of oceanography. Explorations helped in several ways to understand the ocean surfaces. Scientific investigations began with early scientists as James Cook, Charles Darwin and Edmund Halley provided a lot of information. Ocean exploration itself coincided with the developments in shipbuilding, diving, navigation, depth measurement, exploration and cartography. Ancient explorations refer to the period when people explored the ocean boundaries. Notable explorations include, the Greeks, the Egyptians, the Polynesians, the Phoenicians, Phytheas, Herodotus, the Vikings, and 1 the Portuguese. During the period between 15th and 16th centuries, deep diving became possible with the development of new diving suits and helmets. Ocean expeditions continued to sail with scientific curiosity and the first submarine was also invented. The scientific understanding of oceans increased over a period of time and people started studying the oceans with great interest and involvement. 2.1 The Marine Explorations The modern knowledge of the ocean began with voyages of discovery of Christopher Columbus (1492- 1494), Vasco da Gama (1497-1499), Ferdinand Magellan (1519-1522), and many others. They laid the foundation for global trade routes stretching from Spain to the Philippines in the early 16th century. The routes were based on a good working knowledge of trade-winds, the westerlies, and western boundary currents in the Atlantic and Pacific. The early European explorers were followed by scientific voyages of discovery led by (among many others), James Cook (1728-1779), Charles Darwin (1809-1882), Sir James Clark Ross and Sir John Ross. All of them surveyed the Arctic and Antarctic regions from the Victory, the Isabella, and the Erebus. Edward Forbes (1815-1854) studied the vertical distribution of life in the oceans. 2.2 Bathymetric mapping The beginnings of modern seafloor mapping coincided with the advent of systematic oceanographic observations. Some of the first recorded measurements of bathymetry were made by the British explorer Sir James Clark Ross in 1840, by the U.S. Coast Survey beginning in 1845 with systematic studies of the Gulf Stream, and by the U.S. Navy under the guidance of Matthew Fontaine Maury beginning in 1849. In 1872, the HMS Challenger expedition was the first to use fully the methods of Bathymetry. The Challenger was the first vessel used to systematically record information about all the oceans except the Arctic, including their depths, circulations, temperatures, and organic life. In 1925, the Meteor, one of the oldest South Atlantic Ocean expedition, used echo-sounder, for depth measurements using sound waves. In 1950s, the sophisticated Precision Depth Recorders were invented and used. 2.3 Remote sensing Space Oceanography encompasses a detailed oceanographic research and technological development resulting from manned and unmanned systems in the Earth’s orbit. These systems observe and measure the oceanographic parameters such as seas surface winds, sea surface temperature, waves, ocean currents and frontal regions and provide real-time data for analysis. Remote sensing data obtained from satellites represents an indispensable source of information for oceanographers and fishery scientists. It enables researchers to monitor and study the marine environment as a fundamental basis to create a balance between sustainable environmental management and economic interests. 2.4 Satellite Oceanography Satellite Oceanography is a major milestone in the ocean analysis. The launching in 1978 of Seasat, the first oceanographic satellite, revolutionized measurements of physical properties of the ocean. Within a few years, the sea-surface temperature, wave height, variations in sea surface contours, ice cover, chlorophyll content, and other parameters were measured and reported almost instantly from satellites. The sea surface properties that can be measured to useful accuracy from a satellite are the Ocean Colour, Sea Surface Temperature (SST), Roughness, Upwelling and Sea Surface Height (SSH). 3.0 Oceanography -An inter-disciplinary subject 2 Oceanography is an interdisciplinary science. It uses the principles and insights from biology, chemistry, geology, meteorology, and physics to analyze ocean currents, marine ecosystems, ocean storms, waves, ocean plate tectonics, and features of the ocean floor, including exotic biomes such as cold seeps and hydrothermal vents. Oceanography is a part of the subjects like Physical Geography, Marine biology, Marine geology, Fishery biology, Marine Engineering and Marine Geophysics. Subjects like historical geology, palaeontology and palaeo-climatology are all inter-related subjects to oceanography. It is an inter-disciplinary subject. 3.1 Branches of oceanography Oceanography is a very vast subject. It has several branches. The major branches of oceanography are, Physical Oceanography, Chemical Oceanography, Biological Oceanography, Geological Oceanography, Marine Biology, Applied Oceanography, Marine Meteorology, and Palaeo-oceanography. Although oceanography is the scientific study of the ocean, the sub-discipline of physical oceanography is principally concerned with the study of the structure and movement of water in the oceans. Study of Physical setting of Oceans: Physical oceanographic studies utilize a number of scientific specialties, and studies can encompass a diversity of technologies—from echo-sounding determinations of seafloor structure and seismic studies of movements in oceanic crust to satellite estimations of current flow based on radar reflections and thermal imaging. Physical oceanography studies the many factors that influence the movement of ocean waters. Wind can push surface water, and the gravity fields of the Sun and Moon continually exert gravitational tugs that push and pull massive amounts of water in tidal cycles. Earth's rotation also contributes to the physical movement of water, as do density and temperature differences between oceans or between layers of water within the same ocean. 3.2 Five Major Oceans The planet Earth is covered with 70% of water. All the oceans of the world cover about 361.1 Million square kilometers and occupy a volume of 1,370 Million cubic kilometres. The average depth of an ocean is 3,730 meters. All the oceans of the world are fully interlinked. They are the Pacific, the Atlantic, Indian, Southern Ocean and the icy Arctic oceans. The largest ocean among the oceans of the world, is the Pacific Ocean. This ocean covers about one-third of the earth’s surface. The Atlantic Ocean is the second-largest ocean of the world. It is the youngest of all the oceans and occupies 20% of the Earth’s surface. The third largest ocean of the oceans of the world is the Indian Ocean. The waters around the Antarctica region are known as the Southern Ocean. It is the fourth largest ocean. Arctic Ocean is the smallest of the five oceans. All marine sciences deal with the study of all these oceans, their marine species, their ocean waves and the other ocean life. 3.3 Seas of the World The Seas of the World are almost hundreds in number. The notable seas are, the Mediterranean Sea, the Caribbean Sea, the South China Sea, the Bering Sea, the Gulf of Mexico, the Okhotsk Sea, the East China Sea, the Hudson Bay, the Japan Sea, the Andaman Sea, the North Sea, the Red Sea and the Baltic Sea. The Mediterranean Sea has an area of 2.9658 Million Sq.km and an average depth of 1,429 m. The Caribbean Sea has an area of 2.718 Million Sq.km and a mean depth of 2,647 m. The South China Sea has an area of 2.319 Million Sq.km and a mean depth of 1,652 m. The Bering Sea has an area of 2.2919 Million Sq.km and a depth of 1,547m. 4.0 Geological Oceanography 3 Geological Oceanography is a division of oceanography. It is mainly dealing with the basic