Earth Science: Oceanography and Water Science

Introduction

Water is a fundamental substance on Earth, covering approximately two-thirds of the surface of the planet. In addition, water has unique chemical properties that make it crucial to numerous reactions that contribute to a significant portion of the biological, geological, and physical processes on Earth. The study of water and its role in the processes on Earth is called water science.

Water science is an applied scientific field encompassing the study of the behavior of all forms of water. This includes both fresh and saline waters as well as gaseous, liquid, and solid forms of water. Some of the larger areas of water science research include hydrology, the study of the movement of water; limnology, the study of lakes and rivers; and oceanography, the study of oceans. Within each of these fields, the biological, physical, and chemical processes of water are further subdivided into areas of research.

Oceanography is one of the larger subjects within the field of water science. Approximately 97% of all water on Earth is marine (related to the oceans). The oceans control weather and climate throughout the planet, drive numerous economies via fisheries, trade, and recreation, and act as a major reservoir for nearly every biogeochemical cycle as well as economically important minerals and petrochemicals. As in all fields of water science, oceanographers specialize in understanding the chemical, physical, geological, ecological, and biological processes that influence and are influenced by the ocean.

Historical Background and Scientific Foundations

Although it was not a formalized subject, the concepts involved in water science probably originated with the advent of permanent human settlements and the development of agriculture. As early as 4000 BC, Egyptian farmers studied the flow of water in order to divert the Nile River to water crops. They began to understand how to build dams and levies to curtail flooding. The building of dams was also practiced in ancient Assyria, Mesopotamia, and China, and the use of these water-controlling structures contributed greatly to the growth of these civilizations.

The study of the oceans originated with the great mariners of the ancient world. The Polynesians may have begun sailing the Pacific more than 20,000 years ago. Phoenicians likely sailed throughout the Mediterranean Ocean by 2000 BC. Much of this early exploration was associated with trade and the discovery of new resources. However while sailing the oceans, ancient sailors accumulated knowledge of currents, tides, geography, and the distribution of fish and other marine organisms.

By 750 BC aqueducts, human-made structures built specifically to carry water from natural sources to cities for public use, were constructed in ancient India, Persia, Assyria, and Egypt, as well as Italy, where the Romans showed themselves to be masters of hydrology.

Greek philosopher Aristotle (384–322 BC) is credited with the first organized study of marine biology. Using his philosophy based in observation, induction, and reason, he identified nearly 200 species of marine invertebrates and fish. He also accurately identified whales and dolphins as mammals. Aristotle and other Greek naturalists also correctly established many of the processes involved in the hydrologic cycle.

In the fifteenth century AD, Europeans began a great exploration of the world's oceans. The Portuguese, Dutch, English, and Spanish launched large naval fleets and made numerous advancements in understanding the oceans. Much of the development involved solving practical problems associated with building boats that could sail faster, producing tools that could navigate more accurately, and creating maps of the oceans.

In the 1600s and 1700s, significant work on the hydrologic cycle was accomplished in Europe. French scientists established that rainfall could account for stream flow. Additional work by English naturalists showed that the quantity of water that evaporated from the Mediterranean was related to the amount of rainfall that occurred in the surrounding lands.

English chemist and mathematician John Dalton (1766–1844) completely described the hydrologic cycle in the 1800s. Throughout the rest of the century, European mathematicians continued to apply physical laws to the behavior of water and established some of the fundamental principles of water science: Bernoulli's law, Darcy's law, and Poiseulle's capillary flow formula.

Between 1872 and 1876, the Royal Society of London funded the first major scientific exploration of the oceans. The society outfitted a war ship called the HMS Challenger to accommodate scientific research. The ship sailed more than 68,000 mi (109,435 km) collecting data on the biology and physics of every ocean except the Indian. The collections from the expeditions fill 50 volumes and required nearly two decades to analyze.

In the early 1800s, the U.S. government recognized the need for an increased understanding of the oceans to defend its coastlines and improve the safety of fishermen and sailors. They established the Naval Depot of Charts and Instruments in 1830 and the Fish Commission in 1871. Soon after, the first oceanographic institutions were established in Woods Hole on Cape Cod in Massachusetts: the Marine Biological Laboratory and Woods Hole Oceanographic Institute. Both of these facilities still play extremely active roles in the fields of oceanography and water science today.

One of the major fields of water science, hydrology, became well-established as a research entity in the early part of the twentieth century. In 1922, the International Union of Geodesy and Geophysics established the Section of Scientific Hydrology, and in 1930 the American Geophysical Union added the Hydrology Section, creating formal forums for the exchange of ideas concerning hydrological research. Both of these associations continue to advance communication between scientists working in hydrology today.

A second major field in water science, limnology, which is the study of lakes, also became formalized in the early part of the twentieth century. The Limnology Society of America (LSA) was established in 1936 to facilitate the exchange of information on aquaculture. LSA merged with the Oceanographic Society of the Pacific to form the American Society of Limnology and Oceanography (ASLO) in 1948. ASLO, and its journal Limnology and Oceanography, continue to provide a forum for the exchange of ideas between all fields of water science.

In the twentieth century, universities and governments became major drivers in water science research, and oceanography in particular. Primary researchers at universities and government institutions compete for domestic and international grants and fellowships to fund research. The governments of many industrialized countries support fleets of research vessels, ocean-viewing satellites, and other sophisticated equipment used to study the way that water behaves on Earth.

Scientific and Cultural Preconceptions

Water science and oceanography both have their roots in day-today activities. Because water is fundamental to life, some of the first priorities of any civilization are

providing freshwater to the public and removing sewage from areas of dense population. Fishing is a basic method for providing a high-protein food source to a population. Farmers channel the flow of water to irrigate their crops. Trade and travel both rely on water-ways. Rivers have long been used as a way to move products and people. Ancient people explored the ocean as a means of discovering new resources and used aquatic vessels to defend their coastlines. Although knowledge of the processes involved with the behavior of water and the oceans has been gathered since the beginning of civilization, water science and oceanography were not truly formal academic subjects prior to the twentieth century.

As populations grew during the industrial revolution, the need for water management brought about some formalization to water science. During this time significant effort was put into building structures to prevent flooding and to aid in irrigation. For example, more than 200 dams were built in England at the end of the nineteenth century. In conjunction with the Works Progress Administration (WPA) in the 1930s, numerous dams were built throughout the United States, blocking entire rivers. Hydrology and water science emerged along with the technology that supported these water management projects.

The onset of World War II in 1939 brought about research into technologies to support naval and marine soldiers. In particular, amphibious assaults on Europe and the Pacific Islands by the United States drove increased ability to predict wave and tidal conditions. With the development of submarine warfare, the necessity to map the seafloor and features of ocean basins such as magnetic fields were developed. This served as the germination of the academic field of oceanography.

Water science became an academic research field in the second half of the twentieth century, however public knowledge of this field was rather limited for many more decades. The efforts of environmental activists in the 1970s led to the passage of numerous laws that brought water science and oceanographic research into the public eye. These laws include the Marine Mammal Protection Act of 1972, the Endangered Species Act of 1973, and the Clean Water Act of 1977.

At the end of the millennium, water science and oceanography were pulled even more firmly into the public sphere. With the advent of interest in climate change, the entertainment industry turned toward the environment, and in particular the romantic notions associated with oceans and waterways for source material. Numerous films like Jaws (1975), Whale Rider (2002), Finding Nemo (2003), and Happy Feet (2006) depict water-related themes. Of major significance to water science, the documentary, An Inconvenient Truth, incorporates conclusions from water science as evidence for climate change. Discussing the career and climate change work of former Vice President Al Gore, who wrote a book by the same title, the film won an Academy Award. Gore went on to share the Nobel Peace Prize with the Inter-governmental Panel on Climate Change in 2007.

The Science

Both water science and the sub-discipline oceanography are large, applied fields of scientific study. Some of the fields of scientific research in water science include hydrology, hydrogeology, and limnology. Aquaculture is an area of research that straddles water science and oceanography because farming of aquatic crops occurs in both fresh and marine waters. Biological oceanography, chemical oceanography, physical oceanography, marine geology, and remote sensing all fall within the discipline of oceanography. This list of sub-disciplines is by no means comprehensive, but rather represents a significant cross-section of the more active fields of research. Each of these more specialized fields of research are, in and of themselves, extremely complex fields of study. Many of these fields borrow tools from other fields of water science, making water science extremely interdisciplinary and interactive.

Hydrology is a branch of engineering focusing on the study of the physical properties of freshwater and how it moves through lakes, rivers, and aquifers. Hydrologists often use computer models to study the flow of water and then use these models to predict the ways that changes to the environment will affect water supplies and water flows. Hydrogeology is a branch of hydrology concerned with the distribution of freshwater on Earth. Hydrogeologists study the ways that geological features affect groundwater flow and storage. Both hydrologists and hydrogeologists are concerned with pollution and the ways that contaminants can affect freshwater supplies.

Limnology is the study of the chemical, physical, geological, and biological processes that affect freshwater lakes, rivers, aquifers, and wetlands. In addition, the study of saline lakes falls under the domain of limnology. Limnologists, like hydrologists, are also concerned with pollution of natural waters. They study the ways in which humans impact the interactions between the living and non-living elements of aquatic environments.

Aquaculture is the farming of animals and plants under controlled conditions in marine or freshwater environments. Research into aquaculture revolves around managing environmental factors to ensure that crops grow quickly and in good health. A major area of research involves developing methods to reduce the pollution generated by aquatic farms. Some of the more economically valuable aquaculture crops include catfish, salmon, oysters, shrimp, crawfish, and kelp.

One of the major goals of biological oceanography is to understand the distribution of marine organisms in the ocean. Numerous factors influence why certain organisms are located in one location and not another. These factors include ocean temperature, dissolved chemicals called nutrients found in the water, ocean currents, and available sunlight. In turn, marine organisms influence the oceans themselves by consuming nutrients and releasing waste products. Research into global warming has focused on marine phytoplankton, which absorb carbon dioxide from the environment in quantities equal to that of all terrestrial plants.

Chemical oceanographers study the chemicals that are dissolved in ocean waters. Variations in the chemical composition of ocean waters result from the influence of weather patterns and atmospheric interactions, runoff from coastlines, dissolution of minerals from the seafloor, and the metabolic processes of biological organisms.

Physical characteristics in the ocean include temperature, salinity, density, and the ability to transmit light and sound. These fundamental properties control ocean currents, wave forces, and the amount of energy absorbed and released by the ocean. These processes, which are studied by physical oceanographers, further affect weather patterns and climate change throughout Earth.

IN CONTEXT: POLYNESIANS, AN ANCIENT SEAFARING PEOPLE

The Polynesians were probably the earliest, and certainly the most ambitious, civilization to navigate the oceans. The area over which the ancient Polynesians sailed covered 26 million mi (66 million km) of open ocean in the western Pacific. Although estimates vary, anthropologists generally agree that these ancient seafaring people settled many of the islands in the Pacific 30,000 years ago. By 20,000 years ago, they had colonized what is today the Philippines and by 2,500 years ago, the Polynesian culture was firmly established on the islands of Tonga, Samoa, the Marquesas, and Tahiti.

The Polynesians developed sophisticated technologies in order to sail the immense distances between islands. They built large boats with dual-hulls that could carry up to 100 people. They developed methods of storing food, water, and seeds for their great voyages. They accumulated a knowledge of the flight patterns of birds and an understanding of changes in the temperature, salinity, and color of ocean water to help find land. There is evidence that Polynesians also created stick charts to map the locations of islands. Bamboo sticks were tied together to represent the motion of water. Straight sticks indicated currents and curved pieces of bamboo showed the way that waves bend around islands. Knots and shells tied to junctions of the sticks indicated the locations of islands.

The Polynesian seafarers are responsible for colonizing Hawaii between AD 450 and 600. This accomplishment required sailing more than 2,000 mi (5,080 km) across the Pacific, from the southern hemisphere to the northern hemisphere, where the navigational stars are completely different. In addition, Hawaii lies to the north of the doldrums, a part of the ocean where the wind often ceases and where Polynesian travelers must have had to paddle with oars. This feat likely qualifies the ancient Polynesians as some of the greatest oceanographers of all time.

Marine geologists study the geological features of the ocean. One of the major focuses of marine geologists is the regions where tectonic plates meet at spreading centers in the deep ocean. In these places clues to the composition of the inner Earth can be found. Understanding how the movements of these plates occur aids in earthquake prediction. A second major focus of marine geology is the study of the chemical and physical properties of sediments on the sea floor. Understanding these properties provides insight into Earth's climactic record and the location of economically important resources such as minerals and fossil fuels.

Remote sensing is a technique in which measurements of an object or process are recorded from a distance

using an electronic instrument. Often electromagnetic energy is directed at objects, such as the surface of the ocean or a lake. The energy interacts with the object and an instrument collects the resulting electromagnetic signal. Researchers analyze these signals to determine the characteristics of the surface. In water science, remote sensing is used to map geological formations surrounding and within bodies of water, to locate objects at the bottom of the ocean, to detect the distribution of microscopic organisms found in high densities, and to track the flow of various water bodies. Special radio tags can be attached to sharks and fish and are used to track migrations using satellites. Because aquatic environments are often difficult to access, the field of remote sensing has played an important role in furthering understanding of the oceans and freshwater bodies.

Influences on Science and Society

Water science and oceanography influence other fields of science greatly. Because water influences so many different processes on Earth, the study of water affects the study of nearly every other environmental science field. In particular, the connections between ocean circulation and climate have greatly influenced the pattern of scientific research in the 1990s and the early part of the twenty-first century.

Growing concern about changes in the global climate has compounded the impact of water science on environmental science in general. The Intergovernmental Panel on Climate Change estimates that the increase in carbon dioxide in the atmosphere between 1905 and 2005 is responsible for a rise in temperature on both land and in the ocean of approximately 1.5F (0.87C). The effects of this increase in temperature on the ocean

are intimately tied to the circulation patterns in the ocean and thus to weather patterns.

An example of the influence of global climate and ocean circulation illustrates this connection. Ocean circulation follows what has been called the great ocean conveyor belt. Under this paradigm, salty cold water in the North Atlantic, called North Atlantic Deep Water, sinks to the bottom of the ocean and moves into the southern hemisphere. It eventually wells up to the surface on the eastern borders of oceans and near the equator. As the water sinks, it gives up heat to the atmosphere. In regions where the water rises to the surface, heat is lost from the atmosphere as it warms the deep, cold water. These, and other, connections between ocean circulation and atmospheric temperature patterns greatly influence weather and climate.

Nearly all climate models predict that changes in atmospheric temperature will increase the rate of ice melt from the ice sheets in Greenland, which are located in the North Atlantic Ocean. If these ice sheets melt, the formation of North Atlantic Deep Water, which drives the great ocean conveyor belt, will cease. This will effectively halt the current pattern of circulation in the world's oceans. Understanding the effects of such a massive paradigm shift to the oceans and links to hydrologic patterns throughout the planet influence the research being done by numerous oceanographers.

Understanding connections between changes to global weather patterns and climate are being studied by water science researchers as well as meteorologists, ecologists, and economists. Scientists are trying to assess the effects of climate change, not only on water processes, but on how these processes may be linked to processes in other parts of the environment as well.

Because water is so fundamental to basic human needs, water science impacts nearly every aspect of society. Changes to the environment often refer to changes to the flow or quality of water in a certain region. Pollution by industry, especially because of the burning of fossil fuels, has affected numerous water processes. Researchers in the field of water science continue to follow these changes and predict their effects. Some examples spanning the spectrum of water issues, from rainwater, to coastal erosion, to water pollution, follow.

Acid rain results when airborne pollutants change the chemistry of rain, making it more acidic. Acid rain was a serious problem in the eastern United States and in the Black Forest in Germany, destroying large swaths of old growth forests in the 1970s and 1980s. In 1990, as part of the Clean Air Act, the U.S. Environmental Protection Agency introduced a program to reduce the emissions of the pollutants that cause acid rain. This program has been generally successful.

IN CONTEXT: REMOTE SENSING

Remote sensing is being used by researchers at the University of Stanford to understand the swimming patterns of one of the oceans top predators: the great white shark. A type of tag called a pop-up tag is attached to the animals dorsal fin. This tag remains attached to the shark for several months and then it detaches from the shark, pops to the surface of the ocean, and sends a signal to a satellite. Researchers then download the tags signal at their lab in California and analyze the results.

The tags that researchers attach to the sharks record the depth of the shark in the ocean, the temperature of the water, and the light intensity. Using these three measurements along with satellite maps of the surface temperature in the ocean, scientists can reconstruct the path that the shark follows.

Results from the tags indicate that the sharks remain near the shore of California in the fall, where they can easily prey on young seals living in rookeries. During this time they rarely dive deeper than 90 feet (27 m). In the winter the sharks leave the islands and migrate out into the Pacific Ocean. Some of them travel as far as the Hawaiian Islands, a distance of more than 2,000 mi (5,080 km). Others travel out into the Pacific Ocean south of Baja California far from any land and they remain there for several months. The reason for this migration is unknown.

The tags also showed that the sharks prefer to swim at two different depths during their migrations. They were most often within 15 ft (4.6 m) of the surface or at a depth of about 1,000 ft (305 m). They could occasionally dive as deep as 2,000 ft (610 m) below the surface. The temperature range over which the sharks swim varies greatly from as high as 75F (24C) to as cold as 45F (7C). Remote sensing has made research in extreme environments, like the open ocean, and on extreme creatures, like the oceans top predator, much more feasible.

More people live near coastlines than anywhere else on land. Urban development impedes natural patterns of erosion and deposition. Rainwater, which is the fundamental driver of coastal processes, is unable to slowly soak through impervious cover like concrete and cement. Instead it collects into rivulets and rushes into the ocean through small areas where the ground is uncovered. This causes erosion of the beachfront, destroying not only native ecosystems but often beach houses and other development. In 1972, the U.S. government enacted the Coastal Zone Management Act to more effectively regulate development in coastal regions.

The threat to coastlines is further intensified with the prediction of sea level rising because of climate change. Increased global temperatures are predicted to cause a sea level increase of up to 3.5 ft (1.07 m) in the next century. This sea level rise threatens the people living in places built below the current sea level, such as the Netherlands, Bangladesh, and Florida in the United States.

In some parts of the world, the supply of water itself does not meet the demands of the people in the area. In the western United States, the water systems are failing under the enormous growth in population in California and Nevada. The Colorado River, which is the major water source in the region, no longer flows out at the Sea of Cortez as all the water is consumed for agriculture to supply populations before it reaches the ocean. In the Middle East, one of the significant issues for debate in the peace process involves water rights to the Jordan River.

The food harvested from aquatic environments makes up a significant portion of people's diets through-out the world. In particular, many people enjoy eating top predators such as tuna, swordfish, shark, and filefish. Industrial waste, sewage, and rainwater runoff often contain high quantities of heavy metals, such as lead and mercury. These metals enter the marine food chain when microorganisms absorb the metals from seawater. Large, predatory fish eat many smaller prey and therefore ingest great quantities of heavy metals. The resulting bioaccumulation of heavy metals has contaminated most top marine predators in the oceans. In particular, the U.S. Food and Drug Administration advises that people in sensitive categories—women of child-bearing age and small children—avoid eating several species of marine fish.

Modern Cultural Connections

The growing concern about the effects of climate change on Earth and its impacts on the processes that affect Earth's systems have had a strong impact on society. Following the documentary, An Inconvenient Truth, the public became more aware of the ways in which water is intimately tied to all aspects of the planets climate. The Intergovernmental Panel on Climate Change (IPCC) issued its Fourth Assessment Report in 2007, which details probable effects of climate change on the planet. A significant number of these effects are related to oceanic processes and other water issues.

As a result of increased temperatures, glaciers are expected to retreat in most high altitudes and at the poles. This will cause a rise in sea-level, threatening people living in low-lying areas. This type of ocean intrusion would be devastating, both socially and economically. In particular, the large-scale displacement of populations has the potential to result in regional conflict.

The pattern of precipitation is expected to change as the climate warms. Such changes will result in drought in some places. For example, the Amazon Basin is already experiencing its worst drought in 100 years. This threatens not only the ecosystem, but also the source of food for the people in the region. In other places, like Europe, flooding is expected to occur because of excessive rain.

Most climate predictions indicate that an increased frequency of tropical cyclones in the North Atlantic may result from increases in ocean surface temperature. The intensity of cyclones is also expected to increase. These events can be disastrous, not only for the people affected by the cyclones, but also for insurers, reinsurers, and banks who help those affected recover in the wake of intense weather events.

Some economists have attempted to estimate the costs associated with climate change. The Stern Review, published in 2006, estimated that even under the most conservative of scenarios, the costs to the United States were a loss of 1% of the gross domestic product (GDP) initially, followed by large declines when the temperature increases by 5°F (2.8°C). An increase in wind speed of just 5–10% results in hurricane damage increases costing 0.13% of the U.S. GDP. In the United Kingdom, costs associated with flooding are expected to increase between 0.1 to 0.3% of the GDP.

The complexities of the interaction of water processes and climate change are significant and multifaceted, and are greatly enhanced by the impact of global climate change. The effects on society are yet to be seen, but it is certain that continued study in water science and oceanography are crucial to understanding, and perhaps mitigating, these impacts.

See Also Earth Science: Atmospheric Science; Earth Science: Climate Change; Earth Science: Exploration; Earth Science: Geography; Earth Science: Navigation; Earth Science: Plate Tectonics: The Unifying Theory of Geology.

bibliography

Books

Garrison, Tom. Oceanography: An Invitation to Marine Science. 5th ed. Stamford, CT: Thompson/Brooks Cole, 2004.

Prager, Ellen, and Sylvia A. Earle. The Oceans. New York: McGraw-Hill, 2000.

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Woods Hole Oceanographic Institution. http://www.whoi.edu/ (accessed March 2, 2007).

Julie Berwald