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Unit 6: Ocean Sustainability and Geoengineering

Michelle Kinzel (San Diego Mesa College/Southwestern College)
Astrid Schnetzer (North Carolina State University)
Cara Thompson (Santa Monica College)

These materials have been reviewed for their alignment with the Next Generation Science Standards as detailed below. Visit InTeGrate and the NGSS to learn more.


In this unit students are introduced to the concept of geoengineering. Through the completion of concept charts and guided whole group discussion, students analyze the pros and cons of iron fertilization and implementing several different proposed interventions for moderating global warming.

Science and Engineering Practices

Constructing Explanations and Designing Solutions: Apply scientific ideas, principles, and/or evidence to construct, revise and/or use an explanation for real- world phenomena, examples, or events. MS-P6.4:

Cross Cutting Concepts

Systems and System Models: Systems can be designed to do specific tasks. HS-C4.1:

Cause and effect: Systems can be designed to cause a desired effect. HS-C2.3:

Disciplinary Core Ideas

Chemical Reactions: Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants. MS-PS1.B1:

Global Climate Change: Though the magnitudes of human impacts are greater than they have ever been, so too are human abilities to model, predict, and manage current and future impacts. HS-ESS3.D1:

Earth Materials and Systems: Earth’s systems, being dynamic and interacting, cause feedback effects that can increase or decrease the original changes. HS-ESS2.A1:

Developing Possible Solutions: When evaluating solutions, it is important to take into account a range of constraints, including cost, safety, reliability, and aesthetics, and to consider social, cultural, and environmental impacts. HS-ETS1.B1:

Performance Expectations

Engineering Design: Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts. HS-ETS1-3:

Earth and Human Activity: Evaluate or refine a technological solution that reduces impacts of human activities on natural systems. HS-ESS3-4:

  1. This material was developed and reviewed through the InTeGrate curricular materials development process. This rigorous, structured process includes:

    • team-based development to ensure materials are appropriate across multiple educational settings.
    • multiple iterative reviews and feedback cycles through the course of material development with input to the authoring team from both project editors and an external assessment team.
    • real in-class testing of materials in at least 3 institutions with external review of student assessment data.
    • multiple reviews to ensure the materials meet the InTeGrate materials rubric which codifies best practices in curricular development, student assessment and pedagogic techniques.
    • review by external experts for accuracy of the science content.

  2. This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

    This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

    • Scientific Accuracy
    • Alignment of Learning Goals, Activities, and Assessments
    • Pedagogic Effectiveness
    • Robustness (usability and dependability of all components)
    • Completeness of the ActivitySheet web page

    For more information about the peer review process itself, please see

This page first made public: Nov 22, 2016


Students are introduced to the concept of geoengineering, "the deliberate large-scale intervention in the Earth's climate system, in order to moderate global warming" (The Royal Society). The goal is for them to leverage their acquired knowledge from previous units in physical oceanography, ocean chemistry, biodiversity, and ecosystem ecology to evaluate the validity and/or the risk of geoengineering (systems thinking). Current and future generations will be required to make informed decisions on whether they support strategies that result in irreversible changes in Earth's carbon cycle.

Learning Goals

By the end of the unit, students will be able to:
  1. Apply knowledge of the carbon cycle and food web dynamics to explain the conceptual approach that geoengineering strategies (i.e. ocean fertilization) are built on.
  2. Analyze the pros and cons of implementing geoengineering solutions to address changes to the global climate system.

This unit directly supports multiple InTeGrate guiding principles and addresses grand challenges by evoking systems thinking based on previously acquired knowledge (Units 1 through 5). They will be able to interpret and discuss media reports related to geoengineering questions and identify bias and/or error in light of political or economical reasoning.

Context for Use

This unit should be used in connection with the previous units of the Ocean Sustainability Module for an introductory marine, environmental, or geoscience course. This unit is designed to be used in a classroom of 10–100 students over the course of one 50-minute class period. Work is completed in class and is followed by homework (accumulative assessment) to design a fact sheet on global climate change impacts on marine communities and discuss mitigation strategies.

Description and Teaching Materials


1. Lecture and classroom discussion (10 min)

Instructor starts with first part that engages the students (open question and answer format) in a review of previous units on the carbon cycle, ocean currents and biological productivity, organismal diversity, and food web dynamics.

Lecture for instructor (with answer slides) —


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Lecture for students (without answer slides) — Unit6_LectureStudents (PowerPoint 2007 (.pptx) 2.8MB Oct27 16)

Notes on Lecture (see details in comment section in PowerPoint):

  • Slides 1 and 2 — Learning goals, definition of geoengineering, lecture content.
  • Slides 3 and 4 — Review of Unit 1 on temperature, ocean currents and productivity. Students provide answers on "direction of water" and patterns of "nutrient availability."
  • Slides 5 and 6 — Review of Unit 2 on the carbon cycle, which was discussed with an emphasis on the solubility cycle previously and now focuses on how biologically-driven processes impact the carbon cycle. Students provide answers on the missing terms.
  • Slide 7 — Concept chart summarized how abiotic factors such as temperature and carbon chemistry interact with biological processes and revisits examples previously discussed. The missing terms are filled in by the students in Activity 6.1 (below).

2. Activity 6.1 (8 min)

Students use the provided list of terms to fill in the missing processes (arrows) and organisms (circles) in the concept map. Allow students to compare and discuss with their neighbors. Continue lecture by showing the filled in concept map and answer any emerging questions. — Slide 8.

3. Activity 6.1 Follow-up (10 min)

Building on the review, the instructor will explain how biological processes within the water column can lead to the sequestration of CO2 and subsequent transport of organic matter to the deep ocean (biological pump), and how this process has become the basis for geoengineering strategies (e.g. ocean fertilization). Students are introduced to several strategies of geoengineering and will be able to exemplify the challenges and risks that arise using the example of ocean fertilization.

  • Slides 9 –13 — Walk students through the carbon cycle by separately discussing processes that drive the conversion and fate of biological carbon in the upper and then the lower water column.
  • Slides 14 and 15 — Introduce students to ocean surface regions that are characterized by high nutrient but low productivity, where micronutrients limit phytoplankton growth, and the idea of ocean fertilization as a means to increase algal growth and subsequent CO2 sequestration and carbon transport to depth. Leads into Activity 6.2.

4. Activity 6.2 and (~8 min) Answer Discussion (15 min total)

Students individually familiarize themselves with the graphic illustration and background information on an iron fertilization experiment off the coast of Alaska. They then answer four related questions that require them to analyze the presented information in context with the lecture material. After the students hand in their filled-in activity sheets, the answers are discussed using the PowerPoint answer slides (14–18 in the instructor version of PowerPoint). There should be time for discussion of potential misconceptions or difficulties in interpreting the data. This activity will lead directly into the rest of the lecture.

5. Lecture Continued: Instructor discusses the answers to Activity 6.2 (5 min)

  • Slides 17 through 19 — A finalized concept chart is shown that incorporates the use of small-scale (MPAs) and large-scale strategies (geoengineering) to preserve ocean ecosystem health and mitigate global warming. The chart also includes strategies of radiation management and carbon removal that can, but do not always, involve biological processes. Varying strategies are further illustrated in Slide 18. Finally, students are informed about how the status of the science (existing studies and reports) has been compiled by the National Research Council and led to general recommendations on climate intervention (Slide 19).

Teaching Notes and Tips

Optional Additional Slides:

Final slide — Brief history of Iron Fertilization Hypothesis and John Martin's legacy, depending on whether instructor does want to go into more depth about the recent history of Iron Fertilization.


Lecture and Included Review: Students have to review previous lecture content on carbon cycling and biological processes to build their understanding of the biological pump and its premise as a geoengineering tool (Learning Goal 1).

Activity 6.1 and Class Discussion: Students will analyze the outcome of an iron fertilization experiment and are challenged to evaluate the success or failure of this experiment. By that they are building their understanding on why there are large uncertainties and risks in implementing geoengineering solutions to address changes to the global climate system (Learning Goal 2).

References and Resources

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These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »