Chapter 1 The World Ocean System
Imagine you are a cosmic explorer on a long, interstellar voyage between your solar system and its closest neighbor. Your trusty and comfortable spaceship has carried you billions and billions of miles from home, yet for most of that trip, you’ve seen very little. Sure, that asteroid almost hit you, and your onboard computer developed a split personality half a parsec back, but other than that, your trip through interstellar space has been one of the most boring experiences of your thousand-year life.
Then, out of the corner of your telescopic viewscreen, a solar system with a strange blue dot appears. You do a system check. All systems normal. Suddenly the dot increases to two pixels. And then more. Switching to ultrasupercalifragilistic high definition, you realize that the dot is a real object. It’s real! And it’s BLUE. Could there be something, a water-rich object, in this ghastly stretch of nameless space? Phone home, ET. You just found a water planet!Figure 1.1: "There's life out here after all." (Click to enlarge.)[/caption]
Viewed from the far reaches of space, Earth, our home, looks like a tiny blue speck immersed in a sea of black. We know Earth looks this way because in 1990 a small spacecraft, Voyager 1, going where no manmade object had ever gone before, turned its camera back toward Earth and snapped a picture. In doing so, Voyager 1 captured a moment that has come to define what it means to be human. Deeply moved by this image, Carl Sagan (1934–1996), astronomer, author, and host of the original 1980 TV miniseries Cosmos*, offered these words:
That’s here. That’s home. That’s us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there—on a mote of dust, suspended in a sunbeam.
The pale blue dot, as Sagan called it, is Earth, our home, the only known place in the universe where humans exist. Though small compared to the infinity of space, Earth remains our lone island, our singular port of call, a solitary outpost inhabited by the most fascinating and enigmatic species in the known universe, Homo sapiens. Earth is also the only known planet with liquid water covering most of its surface. Its pale blue color, visible from millions of miles away, comes from that water, the ocean—our world ocean.
1.1 A World Ocean Perspective
The world ocean covers 71 percent of the surface of our planet to an average depth of 2.3 miles (3.7 kilometers). It includes all of the waters contained by the ocean basins—which cover 62 percent of Earth’s surface—and the waters that cover the edges of the continents—about 9 percent of the globe. Myriad terms describe various parts of the ocean (seas and gulfs, straits and passages, bights and bays, harbors and sounds, banks and fjords), but oceanographers, the people who study the ocean, recognize only one ocean, the world ocean. For convenience oceanographers call the three major ocean basins by their geographic names—the Atlantic, Pacific, and Indian Oceans. They also recognize two smaller oceans: the Arctic Ocean, an ocean basin surrounded by continents at the North Pole, and the Southern Ocean, a doughnut-shaped ocean defined by cold waters surrounding the Antarctic landmass. Of course, there are many geographic regions within the oceans: the Mediterranean Sea, the Gulf of Mexico, the Caribbean Sea, the Coral Sea, the Arabian Sea, the Red Sea, the Barents Sea, and numerous others. But these geographic designations disguise an important characteristic of Earth’s waters: they don’t stay in the same place for long. They don’t even stay in the same ocean basin. Water at one geographic location eventually—over timescales of years to centuries—finds itself in another geographic location and even back where it began. The waters of the five major oceans flow between the basins and mix to form one ocean—the world ocean.Figure 1.2: The five major oceans that make up the world ocean.[/caption]
The idea of a world ocean, as opposed to several independent oceans, occurred to oceanographers at least a century ago, and likely much earlier. Scientific publications expressing the idea of a world ocean are difficult to find prior to 1917, but British author Agnes Giberne (1845–1939), who wrote novels and nonfiction, mostly with Christian themes, clearly states in 1902 her understanding of a world ocean:
In these days, we know the Ocean as one vast whole. . . . Minor oceans do exist, certainly. We have the Atlantic, North and South; the Pacific, North and South; the Arctic, the Antarctic, and the Indian. Yet for us there is but one great world-wide Ocean, encircling the Earth, every part being in connection with every other part.
Giberne’s proclamation notwithstanding, various sources give credit for the term “world ocean” to Russian oceanographer Yuly Shokalsky (1856–1940), who used it in his 1917 monograph Oceanography. For English readers, Scottish oceanographer James Johnstone (1870–1932) used “World-Ocean” as the title of the first chapter in An Introduction to Oceanography*, one of the earliest textbooks on the subject. Johnstone mentions “the great Southern Ocean” and the “three Oceanic ‘Gulfs’ open out from the Southern Ocean” (i.e., the Atlantic, Pacific, and Indian basins; 1923). This description mirrors the one given by Shokalsky. The idea of the Southern Ocean at the “center” of the three major basins anticipates a modern view of the world ocean as a kind of “steering wheel” for the global ocean circulation (Alfred Wegener Institute 2018).
Just when the concept of the unity of all oceans originated is not easy to ascertain. As soon as it was recognized that the cold water in the depths of the oceans had come from Polar regions and that the renewal of the supply of water in those regions had come from other latitudes, the idea of a world ocean was born, and research was directed toward both the circulation within and the exchange of water between the different ocean basins.
Because it covers more than two-thirds of the earth’s surface, a map of the world ocean is essentially a world map. On ordinary world maps, the interruption forming the edges of the map are often placed in the oceans to show the continents to best advantage. If, on the other hand, oceanographic conditions as a whole are to be shown, it is desirable to have the map interrupted within the land masses and the world ocean shown as a unit.
In 1967 American author Vernon Pizer (1918–2005) published the first book with “world ocean” in its title, The World Ocean: Man’s Last Frontier*. The first textbook to use the term in its title, The World Ocean: An Introduction to Oceanography* (Anikouchine and Sternberg 1973), was the one I used in my freshman year at the University of Washington in 1974. The authors introduce the interconnectivity of the world ocean’s waters as the principle of unity. And they argue that a focus on memorizing the “names and placements of the continents and ocean . . . suggests that the oceans are separated geographically. From an oceanographer’s point of view, the emphasis should be on a world ocean that is completely intercommunicating.” Of course, once the idea of a single world ocean is firmly embedded in your thinking, it doesn’t hurt to know the names and locations of at least some of the geographic oceans. How will you know where to go when someone invites you to the Caribbean?
1.2 An Interdisciplinary Science
The scientific study of the world ocean, a field of science called oceanography, involves several different scientific disciplines. Generally, oceanographers identify with one of four major subdisciplines:
· geological oceanography, the study of geologic processes in the ocean
· chemical oceanography, the study of chemical processes in the ocean
· physical oceanography, the study of physical processes in the ocean
· biological oceanography, the study of biological processes in the oceanFigure 1.3: The four major subdisciplines of oceanography. (Click to enlarge.)[/caption]
Oceanography also borrows from astronomy, geophysics, meteorology, physiology, ecology, and environmental sciences, to name a few. The integration of many different fields of science into one makes oceanography an interdisciplinary science, one that shares and integrates the tools and knowledge of many sciences. Though oceanographers tend to specialize in one discipline, their work requires them to be conversant in other sciences too. They tend to dabble in multiple subjects, which is why an oceanography course can be so much fun—you learn a little of everything!
Oceanography also involves a host of other professionals, from technicians and programmers to a ship’s crew. Technicians provide an onboard repair shop for finicky instruments, programmers maintain the software that communicates with ocean sensors, and the crew navigate the ship, help deploy gear, and cook your meals. (A good rule to follow on board an oceanographic vessel? Be nice to the cook.) Without these support personnel, oceanography would be next to impossible.
From a practical standpoint, oceanographers seek to understand the ways that the ocean serves humanity, how it provides what are called ecosystem services. Costanza et al. (2011) define ecosystem services as “the ecological characteristics, functions, or processes that directly or indirectly contribute to human well-being.” The ocean, for example, provides food, water, materials, waste purification, and a stable climate, among other things. Oceanographers want to know how human activities interfere with the services the ocean provides—how our actions affect the ocean’s ability to function properly and provide services to humanity. With more global-scale environmental and social challenges facing us than ever before, the stakes for understanding the ocean have never been higher.
1.3 An Earth Systems View
Humans exist in the web of a vast life support system controlled largely by the ocean. Much of the air that we breathe, the water that we drink, the food that we eat, and the climate in which we live originates from processes that operate within the ocean. While geologic forces ultimately contribute to slow changes in Earth’s climate, the ocean—in concert with other systems—dominates processes that affect climate on human timescales (e.g., decades to centuries). Together the various interdependent, interconnected systems that collectively regulate Earth have come to be known as the Earth system.
Loosely defined, a system consists of an assemblage of parts and processes working together. System parts include physical components—things composed of matter—while system processes refer to events or activities that result in some outcome. “Working together” implies interactions among those parts and processes—exchanges of energy and matter—and interdependency, meaning the parts and processes depend on each other. Systems may be simple or complex, artificial or natural, and easy or hard to define. Like molecules, they exhibit emergent properties, characteristics and behaviors that cannot be observed by studying the individual parts separately. The properties of a water molecule differ markedly from the individual properties of hydrogen (a highly flammable gas) and oxygen (necessary for combustion). It can be helpful to remember that for emergent properties, the whole is greater than the sum of its parts.
A great number of systems surround and support you in your daily life. For example, a coffee maker* is a fairly simple manmade system. It has parts (stand, filter, heater, etc.), the parts work together (coffee goes in filter, filter goes in filter holder, water pours through filter), there are regulatory processes for temperature and water flow (adjustable on pricier models), and the system produces a great-tasting end product: a cup of coffee. Yet it would be difficult to describe the taste of a cup of coffee simply by studying the parts of a coffee maker.Figure 1.4: A coffee maker as an example of a system. (Click to enlarge.)[/caption]
Similarly, the human body consists of lots of subsystems: circulatory, nervous, musculoskeletal, urinary, reproductive, and more. But do these individual subsystems really describe you? Of course not. Each of you is like a beautiful pupa with the potential to metamorphose into a unique and special butterfly, right?
1.4 Earth’s Seven Spheres
Though highly complex, the Earth system operates in much the same way as other systems with which we might be familiar. Within the Earth system, we can identify seven major subsystems, sometimes referred to as spheres (a reference to their names as well as the concept of their operation in a volume of Earth):
· the anthroposphere, the human system
· the biosphere, Earth’s living systems
· the atmosphere, the gases surrounding Earth
· the cryosphere, the frozen parts of Earth
· the heliosphere, the Sun and solar system
· the hydrosphere, Earth’s waters
· the geosphere, the solid EarthFigure 1.5: Earth's seven spheres. (Click to enlarge.)[/caption]
The hydrosphere includes the world ocean and all other waters upon or within Earth’s surface, including groundwater. The geosphere shapes the ocean basins and exchanges energy and matter across the crustal-ocean interface. The atmosphere exchanges energy and matter across the atmosphere–ocean, or air–sea interface. In the frozen regions of the ocean, the cryosphere, when present, acts as a lid blocking the exchange of energy and matter between the ocean and the atmosphere. All subsystems interact with the Sun, part of the heliosphere, and obtain energy from it. Life on Earth constitutes what’s known as the biosphere, present from the upper limits of the atmosphere to deep within Earth’s crust. Nevertheless, one part of the biosphere, humans, have so radically changed our planet that scientists now consider human activities as a separate subsystem, the anthroposphere.
This description of the Earth system as a collective of seven spheres or subsystems is a useful model for understanding complex systems. Scientists call this a conceptual model, a sort of mental picture of how we think something works. Conceptual models guide our thinking and promote insights that can be tested by observation or experimentation. Our model of Earth as a system helps us appreciate the interconnectedness of its geological, chemical, physical, biological, and human processes. Perhaps most importantly, it helps us understand our utter dependency on this system for our survival. As so eloquently put in one of my favorite short documentaries, The Living Sea*, “We live because the sea lives” (MacGillivray 1995). Conditions established by interactions among the seven spheres make Earth habitable for all living things.
1.5 Keeping an Eye on Climate Change
Earth’s warming temperatures—global warming—and the consequences of that warming for Earth’s weather—climate change—should concern every one of us. Nearly 100 percent of all climate scientists agree that humans are the cause of global warming. Yes, climate varies naturally. But human activities, especially the burning of fossil fuels and the chopping down of forests (i.e., deforestation), have sent Earth’s climate beyond its natural variations. Well beyond. Because we’re the cause, we have the capacity to be the solution. We’ll talk about the causes, consequences, challenges, and solutions for human-caused climate change in the pages ahead.Figure 1.6: Human activities are making Earth's surface hotter. (Click to enlarge.)[/caption]
As you might expect, the ocean plays an enormous role in regulating the severity of the changes ahead. But before we go much further in our journey, it’s helpful to distinguish what scientists mean when they are talking about weather or climate.
Every day of our lives, we experience the changing conditions of the atmosphere, or what we call weather, the instantaneous state of the atmosphere at a given place and time. Weather is happening right here, right now. Weather includes several different variables, such as temperature, humidity, clouds, precipitation, and wind. The ocean influences these variables.
As we grow older, we notice patterns in the weather; seasons change, and some years seem hotter or colder or wetter or drier. Seasonal, annual, decadal, and even longer timescale patterns in weather define what scientists call climate, the long-term average of weather conditions at a given location or globally. Climate represents the probability of a particular type of weather at a given time and place. For example, in California we normally expect hot, dry summers followed by cool, wet winters. Of course, any given day may be hot or cold in summer or winter. But on average, our climate has followed this pattern—until recently.
A sports analogy can help us differentiate between weather and climate. A baseball player at bat may get a hit or strike out in any given inning, but the probability that they will get a hit or strike out depends on their batting average. Better hitters, on average, hit the ball more times, which is why they have a high batting average. Climate, like a batting average, is what we expect. Weather, like a given at bat, is what we get.
For at least the past 140 years, Earth’s global climate—the average of weather conditions for the entire planet—has been changing rapidly. Scientists refer to this as global climate change. Now, climate has been changing throughout Earth’s history. During the ice ages, much of North America and Europe were covered in glaciers. And at other times, Earth has been so hot that the polar ice caps were completely melted. Sea level was more than two hundred feet higher at that time. But the changes that brought these “icehouse” and “hothouse” conditions to Earth happened slowly, over the course of thousands to millions of years. The pace of change over the past several decades has no natural counterpart in Earth’s past that climate scientists have been able to find. We hold the key to our climate future. And it begins with our appreciation and understanding of the Earth system.
1.6 Ocean Literacy
In 2004, a group of more than 100 scientists, educators, policymakers, and ocean advocates met to discuss the most important ideas about the ocean. Based on those discussions, they published Ocean Literacy: The Essential Principles of Ocean Science (Ocean Literacy Network 2006). This document outlines seven major principles of ocean literacy, defined as “an understanding of the ocean’s influence on people and people’s influence on the ocean.” Though aimed at K–12 students and their teachers, The Essential Principles of Ocean Science provides a road map for understanding our relationship with the ocean. The principles state:
1. The Earth has one big ocean with many features.
2. The ocean and life in the ocean shape the features of the Earth.
3. The ocean is a major influence on weather and climate.
4. The ocean makes Earth habitable.
5. The ocean supports a great diversity of life and ecosystems.
6. The ocean and humans are inextricably interconnected.
7. The ocean is largely unexplored.
This book adopts these principles and aims to develop in you an understanding of them. Like all science education, this effort is part of a global effort to improve science literacy, defined by the National Academy of Sciences as “the knowledge and understanding of scientific concepts and processes required for personal decision making, participation in civic and cultural affairs, and economic productivity” (NAS 1996). Through a study of the ocean, you become not only an ocean-literate person but a science-literate one too. Your ability to “speak science” serves not only your interests but also the interests of the world (e.g., Koutsopoulos and Stel 2021).
1.7 Your Mission
Your mission, ocean explorer, if you decide to accept it, is to develop an understanding of our world ocean, the most important ecosystem on Earth. Through this understanding, I hope that you will dedicate yourself to becoming an ocean-literate person. In traveling these pages, I hope you will see how your life and the world ocean are intimately connected. Ultimately, I hope that what you learn here will inspire you to teach others about the world ocean. Together we can make our planet a more sustainable home for all beings, human and otherwise. As underwater explorer Jacques Cousteau (1910–1997) said, “We cannot protect what we don’t understand.”
I hope you’ll join me. Full speed ahead!