The Ocean Revealed: Part 1
August 11, 2008
Marah Hardt is a research fellow at Blue Ocean Institute where she works to share the message fo cliamte change effects on oceans and potential solutions with people around the globe.
Seen from the shore, the ocean looks the same today as it did centuries ago: a vast shimmering silver-blue mirror of sky. This reflective veneer, however, masks an emptier, more polluted, warmer, and chemically changed sea. The collective weight of humanity presses upon the ocean now as never before, as we pull out too many fish and pour in too much garbage, fertilizer, and other pollutants. Our fishing and mining techniques scrape the bottom of the seafloor, raking up sea fans and crushing corals, destroying productive habitat. And by burning fossil fuels we not only raise the temperature of the water but also make it more acidic.
Why does this matter? Because the ocean supports all creation, in the sea and on land, including us. We are not as disconnected from this watery world as we may think. Tied to the shore, we also remain bound to the sea—by our need for food, oxygen, a stable climate, and the countless other life-sustaining services the ocean provides. We should understand something of how the ocean works, why we depend upon a healthy ocean, and why, despite all the damage that has been done, we can still be hopeful.
The Structure and Support of Oceans
We all know that the moon pulls the tides, rhythmically sliding the sea back and forth across the sand. But below the surface, seawater is traveling an epic journey around the globe, driven by the sun and wind, carrying heat and particles across the planet. It begins in the far north Atlantic, where strong winds cool and cause evaporation of the water. This leaves behind colder, saltier surface waters, which are more dense than the warmer, fresher waters below. The colder waters sink and flow south across the seafloor and into the Indian and Pacific oceans. As they travel, these waters warm, eventually rise upwards and after many centuries, flow back into the Atlantic, completing their lap around the globe. This is the giant ocean conveyor belt. It distributes heat from the tropics to the poles and transports nutrients throughout the ocean. Without it, life on earth would be very different. Southern Europe would not have a mild Mediterranean climate, for instance, which would affect growing seasons and crop production.
Winds also drive ocean circulation patterns. Winds blowing offshore (from land to sea) push warm surface waters away from the coast, causing deeper waters, full of nutrients, to rise up and fill the space—a process known as upwelling. The nutrients feed surfacedwelling single-celled algae called phytoplankton.
Phytoplankton comes from the root phyton for plant and plankton for wanderer. Like plants on land, the phytoplankton use nutrients, carbon dioxide and sunlight to make sugars through photosynthesis, creating oxygen as a “waste product.” These tiny algae, many too small to see without the aid of a microscope, produce half of all the oxygen made by plants on the planet. Without them, we wouldn’t have air to breathe. The oceanic food chain starts with phytoplankton— which are prey for bigger plankton—and moves up through fish and mammals. If you have ever dined upon fresh, wild, West Coast salmon, you have feasted upon the products of upwelling ecosystems.
Most of the seafood we eat comes from habitats near the coast—such as seaweed forests formed by giant algae called kelp, which can grow to be 60 feet tall—or from tropical coral reefs. These habitats provide sea life with food, shelter, places to breed, and hiding places for baby fish to grow.
These coastal ecosystems also protect our homes. Wetlands such as salt marshes and mangrove forests have dense root and plant structures that hold onto the soil, preventing erosion and absorbing the force of waves from storms. But since 1900, people have destroyed over 50% of worldwide wetlands for coastal development, timber, and fuel, or to make space for aquaculture farms. The 2004 Indian Ocean tsunami and 2005 Hurricane Katrina reveal the hidden costs, borne mostly by the poor, of wetland loss. In India, villages located behind healthy mangrove forests survived the tsunami; villages without mangroves were washed away by the waves. In the U.S., the loss of coastalmarshes exacerbated flooding damage done to the entire Gulf coast by Hurricane Katrina. Besides food and shoreline protection, people also benefit from the untold number of chemical compounds, many with disease-fighting qualities, found in the ocean. Many marine species still unknown to science could hold potential cures to illnesses such as arthritis, bacterial infections, and cancer.
Biological systems—the living parts of the ocean—supply all these services. But it is the chemical and physical structure of the water that allows life to thrive. Climate change alters the chemical and physical properties of the ocean, and threatens these life support systems on a global scale. Climate Change and the Sea Carbon dioxide, released mostly by the burning of fossil fuels, traps heat in the atmosphere, raising the temperature of the air and ocean. This increase in temperatures causes sea level to rise as warmer water expands and as glaciers melt and release more water into the ocean.
A higher sea level means higher tides and bigger storm waves—both of which cause beaches and cliffs to erode faster, washing away habitats where turtles and seabirds build their nests and people build their homes. Over half of the world’s population lives within 50 miles of the coast, and many, especially the poor, will be displaced as seawater floods their farms and taints the fresh groundwater supply. For residents of small island nations, such as Palau, these changes are already occurring, and there is no “higher ground” to go to. Warmer temperatures cause sea ice to melt sooner and faster. Marine life, including seals, walrus, polar bears, fish and penguins, depend on sea ice for hunting, birthing, resting, or feeding activities. Less sea ice makes it more difficult to catch a meal or care for their young. The ocean also absorbs carbon dioxide from the air—over one third of that produced since industrialization.
When carbon dioxide dissolves in seawater, it makes the water more acidic (by lowering its pH) and reduces the water’s number of carbonate ions. More carbon dioxide in ocean water leads to more carbon dioxide inside the bodies of marine animals, changing their internal pH. These animals must then spend energy balancing such chemical change, diverting energy away from their normal growth and reproduction. Also, fewer carbonate ions in the ocean water make it harder for corals, mollusks, and shelled plankton to build strong, thick shells and skeletons, which are made from carbonate. If we continue to follow current trends in fossil fuel consumption, scientists predict that oceans will be too acidic for corals and some seaweeds by 2050….
This is Part 1 of a two-part article. Part 2 appears here.
Marah Hardt is a research fellow at Blue Ocean Insitute where she works to share the message of climate change effects on oceans and potential solutions with people around the globe.
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[…] This post originally appeared in Creation Care Magazine. You can find Part 1 here. […]