Oceans and the Carbon Cycle

Introduction

Many people have never seen an ocean, yet no matter where each of us lives on Planet Earth, we depend on the health of the oceans in so many ways—for food, recreation, jobs, shipping of goods, medicine, and simply for the wonder of ocean exploration and the discoveries yet to be made. But, we also depend on the oceans to absorb approximately 92 gigatons of carbon dioxide from the atmosphere each year. As humans have added more and more carbon dioxide to the atmosphere by burning fossil fuels, oceans have responded by absorbing more carbon dioxide. Indeed, the oceans have absorbed about half of all the extra carbon dioxide people have put into the air over the last 150 years!

How do oceans absorb carbon dioxide? Where does the absorbed carbon go? If fossil fuel emissions continue to increase, can oceans continue to absorb greater and greater amounts of carbon dioxide from the atmosphere? Or will carbon uptake by oceans slow down? These are all important questions that climate scientists and oceanographers are working to answer.

In Part A, you will learn how the oceans "absorb" carbon by considering three ocean processes that draw down carbon dioxide into the oceans: the physical carbon pump, the biological carbon pump and the carbonate pump. Using videos and interactives, you will explore the role of marine food webs- including plankton and microbes- in moving carbon from the atmosphere down into the deep ocean. In Part B, you will explore the role of phytoplankton in ocean uptake of carbon in greater depth by analyzing conditions and locations for its growth. You will also learn about the interdependence of the nitrogen cycle and the carbon cycle and how this interdependence can influence climate.

After completing this Lab, you should be able to:

• Describe the biological, physical and chemical oceanic processes that absorb, transport and store carbon in the oceans.
• Describe the role of phytoplankton and the microbial loop in maintaining the oceanic biological pump.
• Describe how the oceanic carbon cycle and the oceanic nitrogen cycle are interdependent.
• Describe how the ocean biosphere can influence climate.

Keeping Track of What You Learn

Throughout these labs, you will find three kinds of questions.

• Checking In questions are intended to keep you engaged and focused on key concepts and to allow you to periodically check if the material is making sense. These questions are often accompanied by hints or answers to let you know if you are on the right track.
• Stop and Think questions are intended to help your teacher assess your understanding of the key concepts and skills you should be learning from the lab activities and readings.
• Discuss questions are intended to get you talking with your neighbor. These questions require you to pull some concepts together or apply your knowledge in a new situation.

Your teacher will let you know which answers you should record and turn in.