Predicting Future Oceans: Sustainability of Ocean and Human Systems Amidst Global Environmental Change

By William Cheung

Predicting Future Oceans: Sustainability of Ocean and Human Systems Amidst Global Environmental Change provides a synthesis of our knowledge of the future state of the oceans. The editors undertake the challenge of integrating diverse perspectives—from oceanography to anthropology—to exhibit the changes in ecological conditions and their socioeconomic implications. Each contributing author provides a novel perspective, with the book as a whole collating scholarly understandings of future oceans and coastal communities across the world. The diverse perspectives, syntheses and state-of-the-art natural and social sciences contributions are led by past and current research fellows and principal investigators of the Nereus Program network.

This includes members at 17 leading research institutes, addressing themes such as oceanography, biodiversity, fisheries, mariculture production, economics, pollution, public health and marine policy.

This book is a comprehensive resource for senior undergraduate and postgraduate readers studying social and natural science, as well as practitioners working in the field of natural resources management and marine conservation.

• Provides a synthesis of our knowledge on the future state of the oceans
• Includes recommendations on how to move forwards
• Highlights key social aspects linked to ocean ecosystems, including health, equity and sovereignty

• Language: English
• Publisher: Elsevier Science
• Release date: Aug 17, 2019
• ISBN: 9780128179468

Book preview

sustainability.

Section 1

Predicting future oceans

Outline

Chapter 1 Predicting the future ocean: pathways to global ocean sustainability

Chapter 1

Predicting the future ocean: pathways to global ocean sustainability

William W.L. Cheung,    Institute for the Oceans and Fisheries, The University of British Columbia, Vancouver, British Columbia, Canada

Abstract

The ocean and its biodiversity provide ecosystem services that are important for the well-being of human societies. However, environmental impacts from human activities such as overfishing, climate change, and pollution are reducing the capacity of the ocean to support these services. We are now at the crossroads of deciding the relationship between the ocean and people. Understanding such relationships and predicting (or projecting) its future provide important knowledge to inform decisions and actions that shape ocean sustainability. This chapter explains the key theoretical and analytical frameworks developed by the Nippon Foundation Nereus Program that contributes to the goal of Predicting the future ocean. Particular focuses are put on four components: (1) characterizing the coupled human–natural marine system, (2) exploring the confidence and uncertainty in future ocean projections, (3) examining adaptation to the changing ocean, and (4) elucidating the linkages between the ocean and sustainable development. These frameworks synthesize the understanding of the functioning of marine systems and use models and scenarios to generate projections of the future ocean to inform policies and decision-making. It also helps understand the responses of human communities to the changing ocean and develop new perspectives of viewing the ocean in the context of human society.

Keywords

Coupled human-natural system; future ocean; models and scenarios; uncertainties; climate change; sustainable development; adaptation

Chapter Outline

1.1 The coupled human–natural marine system 6

1.2 Confidence and uncertainty in predicting the future ocean 9

1.3 Adaptation to the changing ocean 11

1.4 The linkages between the ocean, sustainable development, and policies 12

References 13

The Earth should be more accurately called the Ocean. Carl Sagan famously described our planet as the pale blue dot [1]. This view considers that the Earth is small relative to the size of the solar system while, more notably, the majority of our planet’s surface is covered by the ocean. The ocean is key to the maintenance of the climatic condition of our planet, such as regulation of temperature and maintenance of water cycle, and makes it suitable for the vast diversity of life on Earth to survive, including humans [2,3]. The ocean and its biodiversity also provide many other services to people such as transportation, food, recreation, and culture. The importance of the ocean to us humans is largely undervalued historically [4], partly because of the remoteness of much of the ocean relative to what most people can see and experience every day. However, the tide is turning; in recent decades advancements in ocean natural and social sciences have helped us recognize the vital role of the ocean to the Earth system and humankind [3], along with a sense of the vast scale of our impacts on it.

Our awareness of the human impacts on the ocean and the knowledge about the ocean system is rapidly increasing (Fig. 1.1). Human activities have altered the biophysical properties of the ocean and the impacts on marine ecosystems are detectable by science and visible by the public at large [5] (Fig. 1.1). Such impacts have reduced the capacity of the ocean to support essential ecosystem services and the consequences have started to affect human wellbeing. Clear examples are overfishing and climate change driven by emission of massive amounts of greenhouse gas into the atmosphere that impacts marine ecosystems, biodiversity, and coastal communities such as those in coral reefs [6–9]. Concurrently, over the last century, we have been rapidly generating and accumulating knowledge about the fundamental functioning of the ocean and its coupled natural and human systems. The advancement of technology and increasing international research collaborations have allowed us to go further, deeper, and spend more time observing the ocean. Moreover, new theories and models in oceanography, ecology, and the interrelationships between and within the ocean and human societies have helped us understand the role of the ocean to support human societies and the consequences of human activities on the ocean.

Figure 1.1 Time-series of indicators of ocean observation effort, consequences of human activities on marine environment, fish stocks, and fisheries, and key international marine policies: (A) number of ocean station data casts in the World Ocean Database (×10³) and deployed from Argo ¹ (including biogeochemical Argo) (10⁶)—floats with automated instruments deployed to collect real-time ocean conditions data [10]; (B) number of records of occurrence of marine organisms in the Nererus-CORU marine biodiversity database (see Chapter 9: Current and future biogeography of exploited marine groups under climate change); (C) global ocean heat content [11]; (D) global annual fisheries catch [12] (see Chapter 15: The Sea Around Us as provider of global fisheries catch and related marine biodiversity data to the Nereus Program and civil society); (E) mean temperature of global catches, computed from the mean of the temperature preference of species represented in the global fisheries weighted by their annual catch [13]; (F) number of fish stocks classified as overexploited or collapsed using the stock–status plot method (Sea Around Us: www.seaaroundus.org); and (G) year of signing or ratification of major international marine policies in relation to biodiversity, ecosystems, and ecosystem services. Redrawn from J.-P. Gattuso, A.K. Magnan, L. Bopp, W.W.L. Cheung, C.M. Duarte, J. Hinkel, et al., Ocean solutions to address climate change and its effects on marine ecosystems, Front. Mar. Sci. 5 (2018) 337 [14].

We are now at the crossroads of deciding what relationship between the ocean and people we would like to have; this will depend largely on the way we use, value, and govern the ocean in response to climate change and other anthropogenic stressors. Since the 1950s there have been major developments in the governance of the global ocean and regional seas (Fig. 1.1G). Examples of major ocean-related international agreements and governance approaches include the United Nations Convention on the Law of the Seas, Convention on Biological Diversity, the ecosystem approach to fisheries, the Paris Agreement (with specific mention of the ocean), and the United Nations Sustainable Development Goals (SDGs) (with a specific Goal for the ocean). International, regional, and local policy actions play an important role in determining the future of ocean(s). To make wise decisions, it is important to understand the consequences of actions and inactions, and identify available options for future ocean sustainability and their benefits, costs, and trade-offs.

The use of scenarios and models is an important tool to integrate knowledge (including scientific, local, and traditional knowledge) and values to inform decisions and actions for the future ocean [15,16]. Scenarios are representations of possible futures for one or more components of a system under its drivers of changes, including alternative policy or management options. Models help describe the system qualitatively or quantitatively and can be used in association with scenarios to provide projections of plausible futures that are consistent with our current knowledge about the system. The use of scenarios and models requires a deep understanding of the functioning of coupled human–natural ocean systems, their past changes, current status, and future options—this encapsulates the essence of Predicting the future ocean²—an aspirational goal of the Nippon Foundation Nereus Program (hereafter called the Nereus Program). We set the time frame of the prediction [or more accurately projection¹] to the mid-21st century (the 2050s). The contrast in outcomes of alternative decisions on actions and policies (e.g., climate mitigation) now may only start to become detectable robustly at that time frame, and yet a few decades into the future is a close enough time frame that people care about given that changes will be experienced by most of the current generation and their children.

This introduction chapter explains the key theoretical and analytical frameworks developed by the Nereus Program that contribute to the goal of Predicting the future ocean and thus provides the context and foundation for this interdisciplinary book. I also hope that the frameworks described in this chapter could inspire new ideas and be used or adapted by future studies. We chose to focus on four key components of Predicting the future ocean: (1) characterizing the coupled human–natural marine system, (2) exploring the confidence and uncertainty in future ocean projections, (3) examining adaptation to the changing ocean, and (4) elucidating the linkages between the ocean and sustainable development. These four elements provide the framework to synthesize the understanding of the functioning of marine systems, using models and scenarios to generate projections of the future ocean to inform policies and decision-making, understanding the responses of human communities to the changing ocean, and viewing the ocean in the context of human society.

1.1 The coupled human–natural marine system

A first step that the Nereus Program took toward predicting the future ocean was the development of a framework for constructing scenarios and models for a coupled human–natural marine system [17]. Many previous efforts had been devoted to frameworks for models and scenarios for the biophysical components of marine systems. However, linkages of the biophysical system to parallel frameworks for the human dimension were less well-developed, except for the economic components of the human system. Given the strong and dynamic linkages and feedbacks between biophysical and human systems, it is important to consider the ocean as a coupled human–natural system. Frameworks that facilitate linkages and harmonization of scenarios and models across subsystems and scales are needed to fully understand the dynamics of marine systems and to generate knowledge to inform policy [18]. Such frameworks are relevant to the wide spectrum of knowledge generation approaches (e.g., from quantitative to qualitative).

Capitalizing on the wide range of expertise from natural to social sciences within the Nereus Program, an end-to-end framework for scenarios and models of the coupled human–natural marine system was developed (Fig. 1.2). The natural system component of the framework represents a typical conceptual model of marine ecosystems that includes the biogeochemical components of the environment, the marine food web, and human drivers that interact with these biophysical components, for example, greenhouse gas emissions, fishing, non-CO2 pollution. Natural drivers are linked to the human system through human activities that directly interact with a natural system such as fishing and aquaculture. The human system includes a societal component with economic, knowledge, political, and institutional systems. A governance subsystem is specified to help represent policy decision-making and its implications for marine systems.

Figure 1.2 A schematic diagram depicting the coupled human–natural marine system developed at the beginning of the Nippon Foundation–Nereus Program. Adapted from H. Österblom, A. Merrie, M. Metian, W.J. Boonstra, T. Blenckner, J.R. Watson, et al., Modeling social—ecological scenarios in marine systems, Bioscience 63 (9) (2013) 735–744.

Much of the research in science and social sciences undertaken in the Nereus Program contributes to the improved understanding of the linkages and interrelationship between two or more components of this framework (Table 1.1). These research efforts contributed to answering overarching questions about the status, trends, and functioning of coupled human–natural marine systems, such as how are ocean conditions changing? What factors determine the capacity of the ocean to produce fish? How are people dependent on the ocean and fisheries? What principles and approaches are required to effectively govern the changing oceans? The new knowledge generated from answering these questions helped improve the characterization of the coupled human–natural marine system and lay the foundation for credible projection of the future ocean.

Table 1.1

1.2 Confidence and uncertainty in predicting the future ocean

Notwithstanding the usefulness of scenarios and models to inform and support decision-making for marine policies, projecting the complex coupled human–natural marine system decades into the future is associated with many uncertainties that must also be addressed and understood. The Nereus Program has extended a framework that is commonly used in assessing climate projection uncertainties [31,32] (Fig. 1.3, Chapter 7: Building confidence in projections of future ocean capacity). The framework categorizes uncertainties into three classes: scenario uncertainty, model uncertainty, and internal variability (Fig. 1.3). Scenario uncertainty consists of our uncertainties about the future trajectory of human and (or) biophysical drivers that are outside the bounds of the model being used to generate the projections, such as population growth, technology, and greenhouse gas emissions. Model uncertainty is associated with gaps in knowledge about the human–natural system being modeled, or the consequences of the choice of particular ways that the marine system is described in the model. Model uncertainty can be more specifically divided into parameter uncertainty and structural uncertainty, which involves choices about the way the human–natural system is being modeled (e.g., a size-structured fisheries model). Finally, internal variabilities are natural fluctuations generated from inherent processes of complex systems such as climate (e.g., El Niño Southern Oscillation), ecological, and social–economic systems. The three classes of uncertainties may be interrelated, and together form the envelope of projection uncertainties (Fig. 1.3).

Figure 1.3 Framework that subdivides uncertainties about the future ocean into three classes based on their sources: scenario uncertainty, model uncertainty, and internal variability. Redrawn from W.W.L. Cheung, T.L. Frölicher, R.G. Asch, M.C. Jones, M.L. Pinsky, G. Reygondeau, et al., Building confidence in projections of the responses of living marine resources to climate change, ICES J. Mar. Sci.73 (5) (2016) 1283–1296.

Guided by the uncertainty framework, the scenarios and modeling work of the Nereus Program for marine systems, as described in various chapters in this book, includes three main components: (1) development of scenarios for future projections; (2) improvement of marine system understanding and systematic exploration of model uncertainties arising from the improvements in marine ecosystem understanding described in the previous section; and (3) exploration of the significance of system variability in addition to long-term mean changes.

The scenario works took a range of different forms, from qualitative [33] (see Chapter 48: Beyond prediction—radical ocean futures—a science fiction prototyping approach to imagining the future oceans) to quantitative [34], and for both the human and biophysical dimensions. Much of these explorations are based on archetypes of established scenarios used in global environmental assessments, such as the Shared Socioeconomic Pathways and the Representative Concentration Pathways [35]. The representation of the scenarios also took different forms, including futuristic visual descriptions of alternative futures and numerical projections of changes in biodiversity, fisheries and benefits to the society.

The Nereus Program applied existing approaches and frameworks to explore different aspects of model uncertainties, particularly through the use of multimodel approaches [36]. For example, we projected climate change effects on global marine ecosystems and fisheries using a wide variety of approaches such as species distribution modeling (including mechanistic, correlative and machine-learning) (Chapter 9: Current and future biogeography of exploited marine groups under climate change), size-based modeling (Chapter 16: Life history of marine fishes and their implications for the future oceans), trophic spectrum-based modeling (Chapter 12: Changing biomass flows in marine ecosystems: from the past to the future), functional guild-based modeling [37], and empirical relationship-based modeling [22]. Uncertainties associated with the choice of parameters were then addressed during the development of each type of model. We also participated in community-based initiatives to compare global and regional scale marine ecosystem models, such as the Fisheries and Marine Ecosystem Impact Models Intercomparison Project (FISH-MIP) (Chapter 7: Building confidence in projections of future ocean capacity).

For the exploration of internal variability of marine ecosystems and fisheries, the Nereus Program focused on evaluating the implications of the variability of the climatic and oceanic system for marine ecosystems, biodiversity, and fisheries. Internal variability is characterized using projections from different ensemble members of one of the Earth system models (the NOAA–Geophysical Fluid Dynamics Laboratory Earth System Model 2M). These ensemble projections were initialized using different sets of model parameters that generated different interannual variations of the climatic and oceanic system. Thus using these projections we were able to characterize, for example, the relative contribution of internal variability relative to other sources of uncertainties in projecting future changes in key ocean variables that are important to marine ecosystems [19]. The results of such analysis highlight the time frame for the emergence (i.e., long-term changes beyond historical variability) of changes in the key ecosystem stress. These changes, including warming, deoxygenation, acidification, and the occurrences of extreme events, such as heat waves, vary with these ocean variables and ocean basin [38]. These findings help inform the time frame and prioritize actions to address different types of impacts from the changing ocean.

1.3 Adaptation to the changing ocean

In the framework for the coupled human–natural marine system, we recognized the adaptiveness of the system, as it is dynamic and changing continuously in response to natural and human drivers [17]. One important aspect of the adaptive marine system that the Nereus Program focused on is adaptation to climate risks and impacts on marine biodiversity and fisheries at multiple levels (organization) and scales. We developed a framework to facilitate the organization of available studies and knowledge on climate adaptation in marine systems (Fig. 1.4) [39]. The framework recognizes that adaptation responses and actions are dependent on the contexts of specific levels and scales. For example, biological adaptation of fishes at an individual level to changing ocean conditions may ultimately relate to improving fitness (number of viable offspring) while adaptation actions at the individual human level may aim to maintain/improve livelihood or security (Fig. 1.4). The interplays of these different responses emerge into complex adaptation at the level of the coupled human–natural system [40].

Figure 1.4 Adaptive responses to changing ocean (coupled human–natural system) at different levels of organization. Blue, natural system; orange, human system. Adapted from D.D. Miller, Y. Ota, U.R. Sumaila, A.M. Cisneros-Montemayor, W.W.L. Cheung, Adaptation strategies to climate change in marine systems, Global Change Biol. 2017.

Research of the Nereus Program contributed to the understanding of adaptive responses at different levels and scales of the coupled human–natural system. We synthesized knowledge about the adaptation of marine systems in published literature and found that there is a bias of knowledge toward natural systems and that information about responses that encapsulate both human and natural systems is limited [39]. Such knowledge gaps pose a barrier to future projections of the oceans that explicitly incorporate adaptation. This has thus informed the development of research projects that address these gaps using diverse approaches including laboratory studies to understand thermal adaptation of marine organisms (Chapter 8: Marine biodiversity and ecosystem services: the large gloomy shadow of climate change), participatory research to understand stakeholder responses to changes (Chapter 17: Fisheries and seafood security under the changing oceans), modeling of adaptive behavior of fish stocks and fisheries (Chapter 25: Synthesis: changing social world of oceans), and how fisheries and international policies are adapting to changing oceans (Chapter 33: Synthesis: the opportunities of changing ocean governance for sustainability; Chapter 40: Synthesis: oceans governance beyond boundaries: origins, trends, and current challenges).

1.4 The linkages between the ocean, sustainable development, and policies

A main aspiration of Nereus’ predicting the future ocean is to inform policies and pathways for the sustainable development of human society. Our research is rooted in an understanding of the human and natural components of the ocean systems as being closely linked. Thus changes in marine environments and our subsequent responses will have direct and indirect consequences on biodiversity, ecosystems, ecosystem services, and all dimensions of human wellbeing. The Nereus Program undertook a rapid appraisal of the potential linkages between ocean and sustainable development (as specified under the United Nations’ SDGs) using expert knowledge and published literature to highlight these synergies and trade-offs within complex systems [41]. The resulting framework that links the ocean and SDGs provides a powerful way to identify opportunities and gaps in achieving sustainable development at both global and national scales (Chapter 32: Can aspirations lead us to the oceans we want?).

Overall the outputs of efforts to predict the future ocean are being used to inform international policies for ocean governance that ultimately contribute to securing sustainable development. Of particular focus in the Nereus Program is the governance of the high seas or areas beyond national jurisdiction (see Chapter 40: Synthesis: oceans governance beyond boundaries: origins, trends, and current challenges), which cover most of the global ocean. Although much of these areas are remote from us, they contribute substantially to the wellbeing of people (see Chapter 33: Synthesis: the opportunities of changing ocean governance for sustainability) and the Nereus Program has identified important policy gaps and ways in which these could be addressed (see Chapter 49: In conclusion: sustainable and equitable relationships between ocean and society).

The Nereus Program has aimed to spearhead innovative research, develop new knowledge, and offer new insights about the possible futures of the global ocean and its governance, as reflected partly in this book. In doing so, we also attempted to inform the development of future pathways for sustainable ocean development. The urgency of various current and emerging human pressures and threats on the ocean systems and the knowledge gaps that we identified highlight a continuing need for natural and social science research, but also existing opportunities and key strategies for adapting to ongoing change. In addition, one of the main goals of the Nereus Program is to develop human capacity for predicting the future ocean; the outcome of this is demonstrated in this book, in which most of the chapters are contributed by past and current postgraduate and postdoctoral fellows of the Nereus Program. In the final chapter (Chapter 49: In conclusion: sustainable and equitable relationships between ocean and society) we synthesize key findings from the interdisciplinary work of the Nereus Program and provide an outlook to secure the sustainability of our future ocean.

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¹Calculated based on an annual average casts per Argo float of 875,000 (https://oceanbites.org/oceantech-profiling-the-sub-surface-via-argo-floats/).

²Scientific literature generally distinguishes the use of the term projection and prediction. Projection tells us what could happen given a set of plausible, but not necessarily probable, circumstances. Prediction tells us what will happen, and thus implies more certainty than projection. However, the Nippon Foundation Nereus Program chose prediction in the phasing of its goal because it is more understandable by the general public.

Section 2

Changing Ocean Systems

Outline

Chapter 2 Changing ocean systems: A short synthesis

Chapter 3 Drivers of fisheries production in complex socioecological systems

Chapter 4 Changing seasonality of the sea: past, present, and future

Chapter 5 Extreme climatic events in the ocean

Chapter 6 Seafood methylmercury in a changing ocean

Chapter 7 Building confidence in projections of future ocean capacity

Chapter 2

Changing ocean systems: A short synthesis

Charles A. Stock¹, William W.L. Cheung², Jorge L. Sarmiento³ and Elsie M. Sunderland⁴,    ¹NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States,    ²Institute for the Oceans and Fisheries, The University of British Columbia, Vancouver, BC, Canada,    ³Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, United States,    ⁴Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, United States

Abstract

Variations in weather and climate create and interact with ocean fluctuations occurring over days to decades. In some cases these fluctuations are local. In others they stretch across ocean basins. Marine organisms respond to environmental changes in diverse and sometimes dramatic ways. Over the past century natural ocean fluctuations have been augmented by a variety of anthropogenic drivers. The ocean has absorbed vast amounts of carbon dioxide, excess heat arising from the accumulation of greenhouse gases, nutrients from fertilizers, and other pollutants. While this has moderated climate change and pollution impacts on terrestrial systems, it has had diverse consequences for the ocean. This chapter provides a brief overview of ocean changes of particular relevance for marine life, including ocean acidification, warming, melting ice, shifting ocean productivity baselines, deoxygenation, coastal development, and pollution. We highlight contributions from the Nereus Program, and attempt to provide a broad context for the more detailed discussion of select topics in other chapters in this section. Anthropogenic ocean changes pose a considerable challenge to sustaining marine resources. Continued advances in understanding and predicting ocean changes, such as those described herein, are essential for meeting this challenge.

Keywords

Oceans; climate change; ocean ecosystems; marine resources; acidification; marine pollution

Chapter Outline

2.1 Burning fossil fuels and ocean acidification 21

2.2 Warming oceans, melting ice, and changing ocean circulation 22

2.3 Changing ocean productivity baselines 23

2.4 Ocean deoxygenation 25

2.5 Changing coastlines and ocean pollution 27

2.6 Prospects for understanding and predicting changing oceans 28

References 28

The ocean is often depicted as vast and unchanging. The first characterization is certainly true. Oceans cover over 70% of the Earth’s surface with depths exceeding 10 km in some places. The second characterization is understandable to anyone who has stood on a beach and scanned the seascape as it stretches to the horizon, peered down on the ocean’s expanse from an airplane, or listened to the unyielding rumble of waves breaking on the shore. The impression that the ocean is unchanging, however, is incorrect, or at least incomplete. While constant and unyielding in some respects, the ocean is in fact perpetually changing. This change can manifest dramatically in the passing of volatile storms or in rapid seasonal transitions. It can also be seen in more subtle ocean fluctuations and trends occurring over days to centuries that impact areas as small as local inlets and as large as ocean basins.

Fisheries and other marine resources exhibit profound responses to natural variations in climate and weather [1]. Such responses were evident even before the onset of industrial-scale fishing. Fish scales preserved in oxygen-deprived sediment layers off California, for example, reveal striking multidecadal shifts in dominance between Pacific sardine and northern anchovy that are correlated with climate-driven temperature fluctuations over the past 1600 years [2,3]. In the Bohuslän region of Southern Sweden, catch records and archeological evidence dating back 1000 years reveal periods of abundant herring during multidecadal cold periods and collapses of the local fishery during multidecadal warm events [4]. Similar changes can be seen in fluctuations in availability of species in the commercial seafood market today [5]. Striking examples arise during El Niño events, when anomalously weak easterly trade winds in the equatorial Pacific reduce upwelling and trigger an eastward propagation of warm, nutrient-poor western Pacific waters. This can lead to severe reductions in ocean productivity, reduced fisheries yields, and starvation of fish-reliant marine life in the central and eastern equatorial Pacific [6]. In 1972 a severe El Niño and subsequent overfishing contributed to the collapse of the world’s largest fishery, the Peruvian anchoveta [7,8].

In today’s ocean, the effect of ubiquitous modes of natural variability and fishing pressure has been compounded by other human-derived changes. The ocean’s absorption of increasing atmospheric carbon dioxide (CO2) associated with the burning of fossil fuels has acidified its waters [9]. Global warming arising from the accumulation of CO2 and other greenhouse gases has warmed ocean waters and melted significant amounts of sea and land ice [10,11]. These ocean changes have been implicated in changes in seasonal ocean cycles, ocean productivity baselines, and ocean oxygen declines [12]. Effects associated with the accumulation of greenhouse gases are compounded by other anthropogenic stressors in the marine environment. Rapid development of coastal regions has led to enhanced nutrient inputs, eutrophication, and an increased frequency of harmful algal blooms in many coastal ecosystems [13,14]. Human activities release thousands of persistent organic pollutants and heavy metals to the atmosphere. Many of these chemicals biomagnify in food webs (i.e., are concentrated by a large degree with each increase in trophic level), and also pose risks to wildlife and seafood consumers [15,16].

Predicting the future ocean depends on understanding the response of ocean life to these myriad drivers and predicting future ocean changes. This chapter provides an overview of the ocean changes summarized above—ocean acidification, ocean warming and ice melt, changing ocean productivity baselines, ocean deoxygenation, changing coastlines, and ocean pollution. Contributions from the Nippon Foundation Nereus Program researchers and collaborators are highlighted. The chapters that follow in this Section provide deeper perspectives on a subset of these topics: ocean heatwaves and extremes (see Chapter 5, Extreme climatic events in the oceans), changes in oceans seasons (see Chapter 4, Changing seasonality of the sea), mercury pollution (see Chapter 6, Pathways of methylmercury accumulation), threatened vegetated coastal habitats (see Chapter 3, Drivers of ecosystem production in complex social-ecological systems), and efforts to project the impacts of changing oceans on fish populations (see Chapter 7, Building confidence in projections of future ocean capacity). Finally, this chapter concludes with a brief assessment of prospects for improved understanding of future ocean changes, and improved capacity to predict and adapt to them.

2.1 Burning fossil fuels and ocean acidification

The extraction and subsequent burning of fossil fuels has released vast amounts of carbon dioxide into the atmosphere. This signal was first observed at the National Oceanic and Atmospheric Administration’s Mauna Loa CO2 observatory in Hawaii by David Keeling and colleagues ) ions that do not exchange with the atmosphere. Absorption of CO2 by the ocean is assisted further by the biological pump, whereby photosynthesis at the ocean’s surface converts CO2 to organic matter, some of which sinks before it can be respired back to CO2. This creates a CO2 deficit near the ocean surface relative to depth. If this biologically-driven surface CO2 drawdown was removed, outgassing from the ocean would increase atmospheric CO2 levels by ~140 ppm [22].

Figure 2.1 (A) The time-series of CO2 observations observed at NOAA’s Mauna Loa CO2 observatory in Hawaii. Data are monthly averages of continuous surface flask measurements since 1976 described in Dlugokencky et al. [18]. (B) Ocean pH calculated from dissolved inorganic carbon, alkalinity, and other ocean measurements at station ALOHA [19]. NOAA, National Oceanic and Atmospheric