Introduction: The Ocean System By Dr. Adriana Aquino and Dr. Rondi Davies All life on Earth depends on the ocean. It provides the atmosphere with oxygen and drives the world's climate. Beneath its waves lies an amazing diversity of habitats, each supporting an astonishing array of life, and for every recognized species there may be hundreds more yet to be discovered. Though we learn more about the ocean every year, less than 5% of it has been explored, and we are only beginning to understand how this enormous system works. The Big Idea: Earth is a System As a system, all the planet's physical features (clouds, oceans, mountains, volcanoes) and living organisms (plants, bacteria, and animals) are interconnected. The Earth system is dynamic, open (exchanging matter and energy), and evolving. (The word "system" is applied to any object or process that is made up of different kinds of parts that have some influence on one another.) Why Think in Terms of a System? Systems surround us. Their components organize into levels, or subsystems, each of which has its own properties. For example, the human body, which is a system, is made up of subsystems such as the digestive system or the nervous system. The digestive system is made up of organs, which are made of tissues, which are made of cells, which are made of molecules, which are made of atoms — all of which are systems. The properties of a system extend beyond the physical limits of its individual components: the whole is greater than the sum of its parts. This is more than a truism. We can’t fully understand how any system works without taking into account this web of relationships, nor how any component works without considering the whole to which it belongs. Spheres and Cycles The components of Earth’s system are called spheres, each of which is a system in itself. They are the: • geosphere - the solid earth; • hydrosphere - rivers, lakes, oceans, and ice; • biosphere - all living things; and the • atmosphere - the envelope of air that surrounds the planet. Our planet is dynamic. Matter and energy move constantly through a set of recurring changes called cycles. It is the movement and exchange of energy and material among these cycles and spheres that make life on Earth possible. Energy flows between Earth’s spheres and throughout the different components of the ocean system. This energy cycle involves an amazing chain of transformations. For example, plants transform solar energy into chemical energy (sugar) through photosynthesis, a process that is critical for life on the planet. (Forty percent of this transformation is carried out by phytoplankton in the ocean.) The ocean is such a massive solar energy collector that just a small portion of the heat it traps could power the world. As we’ll learn, it’s this solar radiation that drives large-scale processes such as ocean currents, weather, and climate. In addition to this thermal energy, the ocean also generates mechanical energy through tides and waves. The “Water Planet” Why single out the ocean system? As far as we know, Earth is the only planet with so much liquid water, and the ocean contains 97.5% of it. How does the ocean maintain its volume? What happens when it rains? What happens to the water when it evaporates? The water cycle is the transformation of water into its different states and its movement between the different Earth spheres. The water cycle includes four main processes: evaporation, condensation, precipitation, and collection. It’s not only important for the hydrosphere but also for circulating the planet’s energy, and in particular for the survival of the biosphere. Vast but Fragile Though immense and powerful to human eyes, the ocean system is extremely vulnerable. For example, pollution from toxic waste can move quickly through the food web and end up in our seafood. Rain can be affected by pollution, turning into acid rain, which kills fish along coastlines. Global warming is affecting not only the chemistry and biology of the ocean but also the dynamics of the oceanic currents, the size of ice caps, and the sea level, which could devastate populations living by the shore. Article Discussion Questions 1. Provide evidence from the reading to support why we consider the entire Earth a system. 2. Explain how the quote “the whole is greater than the sum of its parts” relates to systems. 3. Provide evidence that the spheres of the Earth’s system are interconnected. 4. Why is the ocean system so important, but also very fragile?