The Global Conveyor Belt
Things float better in seawater than in freshwater. This is because saltwater has a higher density than freshwater. The salinity and temperature of water affects its density. Water becomes less dense when it freezes, which allows the solid form, or ice, to float on the liquid form, or water. These masses of solid ice help regulate heat and energy from the sun. Without these icebergs, ocean temperatures will rise destroying life in marine ecosystems.
Thermohaline circulation creates w world wide current system called the "global conveyor belt." The global conveyor belt begins with sinking of cold, dense water near the North Pole in the North Atlantic. Then, water moves south and circulates around Antarctica, where cold salty conditions "recharge" it. The water then moves northward to the Indian, Pacific, and Atlantic Ocean basins. It can take around 1,000 years for water to complete one cycle of the global conveyor belt.
These currents are important to marine life. They influence world climate and weather, ocean navigation and transportation, and transport materials and energy to different regions and depths of the ocean.
Marine species affected by climate change include plankton, which forms the basis of marine food chains, coral, fish, polar bears, walruses, seals, sea lions, penguins, and seabirds. One of the most visually dramatic effects of climate change is coral bleaching, a stress response caused by high water temperatures that can lead to coral death. Most scientists believe that global warming will herald a new era of unpredictable weather. Tropical storms and heavy rainfall may increase and so to would the physical damage of coral reefs,coastal ecosystems, and coastal communities. As the oceans warm, the location of the ideal water temperature may shift for many species.
Changing climate affects ecosystems in many ways. Warming may force species to migrate to higher latitudes or higher elevations which temperatures are more suited to their survival. As sea level rises, saltwater intrusion into a freshwater system may force some key species to relocate or die, thus removing predators or prey that are critical in the existing food chain
Upwelling occurs in open ocean and along coastlines. Winds blowing across the ocean surface push water away. Water then rises up from beneath the surface to replace the water that was pushed away. Water that rises to the surface as a result of upwelling is typically colder and richer in nutrients. These nutrients "fertilize" surface waters, meaning that these surface waters often have high biological productivity.
Some examples of phytoplankton are diatoms and dinoflagellates, which are responsible for seasonal algae blooms. Zooplankton are consumers that eat other plankton. Examples include copepods, krill, daphnia, and jelleyfish. Nekton are organisms that spend most of their time in the water column and can swim freely and faster than currents.
One unique property of water is high heat capacity. Water is a liquid rather than a gas at room temperature because of the strong hydrogen bond between the molecules of water. This means that it takes more energy or heat to increase water's temperature than it does for most other substances. The high heat capacity of water also explains why the temperatures of land near a body of water are more moderate. Large bodies of water tend to moderate the temperature of nearby land due to the high heat capacity of water. This high heat capacity results from both the higher specific heat of water and the mixing of heat throughout a greater depth over oceans.
The ocean is great at sucking up C02 from the air. It absorbs about one quarter of the C02 that we humans create when we burn fossil fuels. However, when the ocean absorbs C02 it becomes more acidic. The alkalinity of the ocean is very important in maintaining a delicate balance needed for animals. Because C02 is soluble in water, there are natural exchanges of C02 between the atmosphere and waters at the ocean surface. If the atmospheric concentration of C02 increases, the ocean gradually takes in more C02. Living things in the ocean move carbon from the atmosphere into surface waters then down into the deeper ocean and eventually into rocks.
According to NASA, the polar ice caps are melting at an alarming rate of 9% per decade. The thickness of the Arctic Ice has decreased by 40% since the 1960s.