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Overview
It has often been said that we know more about the moon than we do about our own oceans. In fact, we know a great deal more about the oceans than many people realize. Scientists know that our actions today are shaping the oceans and climate of tomorrow—and that if we continue to act recklessly, the consequences will be dire. Eelco Rohling traces the 4.4-billion-year history of Earth's oceans while also shedding light on the critical role they play in our planet's climate system. This timely and accessible book explores the close interrelationships of the oceans, climate, solid Earth processes, and life, using the context of Earth and ocean history to provide perspective on humankind's impacts on the health and habitability of our planet.
Product Details
| ISBN-13: | 9780691202648 |
|---|---|
| Publisher: | Princeton University Press |
| Publication date: | 07/14/2020 |
| Pages: | 272 |
| Sales rank: | 740,875 |
| Product dimensions: | 5.60(w) x 8.80(h) x 0.70(d) |
About the Author
Read an Excerpt
CHAPTER 1
INTRODUCTION
You may have been told that we know more about the Moon than about the oceans. It is a claim that I often hear from public relations staff, teachers, schoolchildren, and many others in casual chat at parties or receptions. But I work on ocean science for a living, and I am not convinced that it's true. Instead, it strikes me as evidence that most people have no real idea of how much we actually do know about the oceans.
I have been researching and teaching about the oceans for 30 years in the field of paleoceanography. In plain words, paleoceanography studies the ancient oceans and their changes through geologic time, before historical records. In practice it is interpreted to include the associated climate changes because there is a close interaction between the oceans and climate — you cannot research one and not the other. Well over 1000 researchers are currently active in this field worldwide. The number is several times larger if we include the wider ocean sciences, and especially if we include naval research as well. Although this still may not make it a large community, it has been remarkably productive in deciphering the natural, underlying rhythms and processes of ocean and climate change, against which humanity's impacts can be assessed.
A sound general awareness of this knowledge is essential to a well-rounded understanding of the Earth. As such, it is necessary to any meaningful discussion about matters of conservation and policy definition, and — indeed — to underpin election of knowledgeable government representatives. The apparent lack of such awareness can only mean that my colleagues and I have fallen short; that we have insufficiently communicated our findings beyond the narrow circle of specialists. With this book, I hope to change that.
I venture here outside my scientific comfort zone, aiming to share our understanding of how the oceans have come to be the way they are today. Thus, I aim to offer a foundation upon which you, the reader, can build your own informed opinions about the challenges resulting from humanity's relentless drive to exploit the world ocean and its resources. To achieve this, we will travel through time from the first development of oceans more than four billion (or 4000 million) years ago, to the present. Along the way, we will stop at some of the most remarkable events and developments of life in ocean and Earth history.
We will see that life on Earth, including humanity, is closely intertwined with changes in the oceans and climate, no matter whether these result from natural variability or human impacts. These intricate connections between the oceans, climate, and life have been shaped and refined over four billion years. But we will also see that abrupt and dramatic adjustments which have taken place within this complex network, and may take place again, and that highly developed organisms seem to suffer the consequences most intensely. The explosive growth of humanity and our ever-increasing resource dependence make us especially vulnerable.
To gauge the potential consequences, we need to understand the natural variability that underlies human impacts. To learn about natural variability, all we can do is study the past before humans became important. To appreciate the scale and rapidity of human impacts, we need to compare and contrast them with a sound understanding of the underlying natural processes. Without the background knowledge, all else is conjecture. With the background, we stand prepared to make knowledgeable decisions for sustainable actions that will both give us what we need and preserve the system for posterity.
It won't surprise anyone who regularly watches the news that humanity's impacts on the oceans are multifaceted and profound. We pollute the oceans with medium- to long-lasting materials such as plastics, netting, radioactive waste, and dumps or wreckage laden with petroleum or chemicals. We disturb their food webs by overfishing, and by harmful fishing practices such as bottom-disturbing trawling and fishing with explosives. We overfeed (eutrophicate) them by pumping unnaturally large amounts of nutrients into their ecosystems by way of agricultural runoff, effluents, and detergents. We acidify them with our massive fossil-fuel-based carbon injection. And we cause unprecedentedly fast warming with our greenhouse-gas emissions, mainly in the form of carbon dioxide (CO2) and methane (CH4).
We have allowed all this to happen because of a deep-seated, historical notion that the world ocean and its resources are limitless, despite frequent warnings from modern scientific assessments that this is a serious mistake. Probably the worst part of it is the rapid acceleration of the problems. Some 500 years ago, the oceans still were pretty much pristine. By and large, they suffered only moderate change until the early 1800s, by which time the world's human population had reached one billion. Then things changed: large-scale whaling developed from about 1820, and global fish capture started to rise (today, it is well over 10 times higher than in the early 1800s). In the last two centuries, overfishing, pollution, eutrophication, acidification, and warming have risen sharply, on the back of fast human population rise, industrialization, globalization, and consumerism.
Some issues are more visible, like pollution, which gives rise to stronger public support for measures to address them. Other issues are all but invisible, like acidification, and their existence is hardly acknowledged outside scientific circles. But each issue has an element of finality if ignored — all require urgent attention. And because the seas know no borders, this requires globally concerted efforts. Even if a few nations won't join in, action by a majority will still alleviate much of the problem. Waiting for unanimity is nothing but a waste of time doing nothing.
Although they are serious issues, pollution and food-web disturbances fall outside the scope of this book which is concerned with the oceans through Earth history. Focus lies firmly on the other three key issues. We will encounter several events in ocean history that emphasize the urgency of curtailing eutrophication, to halt the spread and intensification of anoxic dead zones — zones in which decomposition of organic remains consumes all oxygen (anoxic means without oxygen). Past oceanic anoxic events reveal a devastating impact on ecosystems, while recoveries typically take thousands of years. The book also deals extensively with the nearly invisible "silent killer" issues of acidification and rapid warming. We will see along our journey through Earth history that such events had particularly devastating consequences.
Toward the end, I will draw on the book's geologic perspective to illustrate that the time for political debate and maneuvering is well and truly over — that a sustainable future requires immediate action. All signs indicate that without such action we are likely to rush headlong over a cliff into one of Earth's largest extinction events. Here, it is critical to emphasize that all documented past events measurably played out in the real world — not just in our minds, in a computer model, or on another planet. It is therefore impossible to dismiss or politicize them as fictitious, impossible, irrelevant, alarmist, or scare-mongering. The way I like to look at it is that Mother Nature has left us this beautiful record, which shows that — when given time — she knows full well how to process our legacy, but that we are not likely to enjoy the way she resolves these problems. We can either heed the warning, or not. But we cannot play ignorant and pretend that no clear warning was issued.
*
Human interest in the seas and oceans goes back to our very roots. Archaeological studies of the earliest modern humans, almost 200,000 years ago in South Africa, have revealed that we as a species have long been attracted to the sea and its seemingly limitless supply of food and shells. Along many of the world's coastlines, archaeologists have found large heaps of discarded shells that often show signs of cooking or breaking for consumption of the soft parts. Shells are also among the earliest items used in decorative art. So it's confirmed: we have always liked to collect shells on the beach.
There is good evidence that humans mastered the skills of rafting or boating at least as early as 50,000 years ago. The peopling of Australia involved the crossing of a few deep-ocean passages through the Indonesian archipelago, which never fell dry during even the greatest ice-age drops of sea level. Arguably, though, the rafting or boating skills may be even older. There are strong indications for an out-of-Africa migration of modern humans 60,000–70,000 years ago, across the southern Red Sea connection with the Indian Ocean, which again did not fall dry.
The enduring success of early humans in navigating the sea and exploiting its resources indicates that these people were carefully observing and studying the movements of the sea and the rhythms of life within it. We can safely presume that such enduring success could not be had just by chance. As any mariner will tell you, the sea is far too hostile and unforgiving for that. Over time, many civilizations and nations became heavily invested in seafaring, and trade, exploration, and research developed hand in hand. Ocean studies eventually became organized into oceanography, which spans the study of physics, chemistry, and biology of the ocean, and marine geology and geophysics, which focus on the geology and physics of the surface and subsurface of the seafloor.
Research in oceanography, marine geology, and geophysics has especially accelerated during the last century, triggered by wartime and cold-wartime needs for better ocean surveying and seafloor mapping. Consider the following examples from a very long list. First, much attention was given to understanding the impact of temperature and salinity (salt-content) contrasts in the oceans on the way sound waves travel, and on documenting these patterns in the oceans, with obvious implications for playing hide-and-seek with submarines. Arrays of underwater microphones, or hydrophones, were deployed to monitor enemy navigation, and after the end of the cold war many of these were retasked for research purposes. Second, there was a general push toward creating detailed maps of the seafloor, to support all manner of military and civilian purposes. Third, submarines beneath the Arctic sea ice routinely monitored ice-thickness variations above them to ensure that they could safely punch through the ice for communications or other operations. The ice-thickness records have since become available and now are invaluable in studies of Arctic sea-ice reduction over the past five or six decades. These initially military and increasingly science-driven research efforts have continued ever since, broadening out to include all aspects of relevance to the oceans and the ocean floor. Today, both fields of oceanography and marine geology/geophysics are thriving on a global scale.
Paleoceanography arose from marine geology, when researchers began to unravel past ocean changes by studying sediments sampled from the seabed. The HMS Challenger expeditions between 1872 and 1876 are commonly credited with the first systematic study of deep-ocean sediments. They are arguably paleoceanography's touchstone. At the time, however, only simple scoops of surface sediment were taken and studied. Systematic recovery of continuous sediment cores that penetrated one to two meters into the seabed started with the German South Polar Expedition of 1901 to 1903. Longer cores were obtained and studied by the US Geological Survey in the late 1930s. Routine recovery of relatively undisturbed sediment cores up to 10 meters' length became possible with the invention and first application of the Kullenberg piston corer, during the Swedish Deep Sea Expedition of 1947 to 1949 aboard the research vessel Albatross.
These developments in coring paved the way for the real emergence of paleoceanography as a separate research discipline in the early 1950s. The fathers of the discipline were the Swede Gustaf Arrhenius and Italian Cesare Emiliani (who did almost all his work in the United States). They were the first to apply sediment geochemical and microfossil stable oxygen isotope data in sediment cores to investigate circulation and temperature changes through time. An intense international research effort ensued that consolidated the discipline, with particular leadership in biogeochemistry by the American Wallace Broecker, and in the field of physical ocean-climate interactions by Sir Nicholas Shackleton in England.
As the discipline grew rapidly, it began to drive the development of new coring techniques. Core lengths of up to 70 meters became possible from the 1990s with the Calypso corer, designed and perfected by the French marine engineer Yvon Balut. Even longer cores were obtained using specialist drilling vessels. Scientific deep-sea drilling has been conducted since 1968 by a large international collaborative consortium that started out as the Deep-Sea Drilling Project (DSDP), then became the Ocean Drilling Program (ODP), and currently goes by the name of International Ocean Discovery Program (IODP). IODP remains the only research organization that is able to routinely undertake deep-sea drilling for science.
Despite these advances in scientific exploration, humanity's ever-increasing interest in the oceans was never just for research purposes. People's greatest interest is in exploiting their vast array of biological, mineral, and energy resources. The evolution of this interest has kept close pace with humanity's own development; arguably, the two are so tightly intertwined that one cannot be conceived of without the other. This relationship essentially stems from the vast — seemingly infinite — scale of the world ocean.
Ours truly is a blue planet, with more than 70% of its surface area covered by oceans. The world ocean is also very deep, reaching an average depth of about 3700 meters, and a greatest depth of about 11,000 meters in the Challenger Deep of the Mariana Trench between Japan and Papua New Guinea. The message is clear: the world ocean is enormous. This has given humanity the mistaken impression that the oceans are limitless, which underlies a range of our behaviors, from large-scale overfishing without heeding careful assessments of what can be sustained, to enthusiastic and unceremonious dumping of vast quantities of unwanted by-products of civilization. These by-products include short- and long-lived refuse, radioactive waste, outwash of chemical pollutants and nutrients, wreckages, heat (cooling water), concentrated salt from desalination plants, and so on.
Through it all, the world ocean has remained our loyal friend. Quietly and unassumingly, it has done us what may turn out to be the greatest favor of all: into its vastness, it has absorbed more than a third of humanity's total carbon dioxide emissions since the start of the industrial revolution. This has limited the rise of atmospheric carbon dioxide levels to the current value of 400 parts per million (ppm), rather than almost 500 ppm if the oceans had not done so. But we can't see it, for the outward appearance of the oceans has remained the same. It is only through specialist measurements that we have learned about the consequences of the carbon dioxide absorption. It has acidified the ocean waters, and ocean acidification has important implications for marine life. There are many examples of this in ocean history — we will discuss several in this book.
(Continues…)
Excerpted from "The Oceans"
by .
Copyright © 2017 Princeton University Press.
Excerpted by permission of PRINCETON UNIVERSITY PRESS.
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Table of Contents
1 Introduction 1
2 Origins 15
Building a Planet, Shaping the Oceans 16
Water, Salt, and Circulation 31
Life, Oxygen, and Carbon 45
3 Controls On Change 56
Orbital and Solar Changes 62
Greenhouse Gases 69
Plate Tectonics 79
Impacts 80
4 Snowball Earth And The Explosions Of Life 82
Into the Freezer 83
Out of the Freezer, Into a Greenhouse 93
A Tale of Two Explosions 95
Reverberations 99
5 Oceans On Acid 109
About Acidification 111
Acidification in Action 118
6 The Age Of Reptiles 126
Choking Oceans 134
Salty Giants 153
7 Winter Is Coming 162
Reconstructing Sea-Level Change 168
The Great Northern Ice Ages 174
Ocean Controls on CO2 178
A Seesaw in the Ocean 185
8 Future Oceans And Climate 192
Our Carbon Emissions 192
Consequences 199
Epilogue 215
Acknowledgments 219
Bibliography 221
Index 251
What People are Saying About This
"Oceans are the vehicle of climate change—on land and sea. Rohling's presentation of the ocean's history—and thus our climate's history—is erudite yet accessible to a broad audience interested in the future of our planet."—James E. Hansen, Earth Institute, Columbia University"In this compelling book, prominent paleoceanographer Eelco Rohling provides the perspective needed to understand the current and future health of our oceans and their role in our rapidly evolving new world."—Paul Andrew Mayewski, director of the Climate Change Institute, University of Maine"In relating the long history of the oceans in the context of climate, Rohling brings together the important idea that climate control on long timescales is a mix of tectonics, ocean circulation, and carbon storage—with carbon storage being a euphemism for ‘How much CO2 is in the atmosphere?'"—Elisabeth L. Sikes, Rutgers University