Properties of Ocean Water

Salinity Where is the saltiest body of water in the world? Salinity in the ocean is between 34 and 37 ppt. That would be about 35 grams per liter. Near the surface, rain, snow, and ice melting add more fresh water. Rivers dumping into the ocean create lower levels of saline. Areas high in evaporation and closer to the poles (below 1 km) are the highest in salt. Bowling Ball clip

Did you guess…? Don Juan Pond isn’t just an awesome name for a little pool of water; it’s also the name of one of the most interesting ponds out there for astrobiologists. At 40 percent salinity, the pond is the saltiest body of water on the planet. It’s 18 times saltier than the ocean. Even though it’s in Antarctica, it’s so salty that it never freezes in conditions that get to 40 degrees below zero. But how does it get all that salt? New research from Brown University seems to have uncovered the answer, and it could mean that ponds like Don Juan Pond are possible on Mars.

The substance that you know as table salt, sodium chloride, is the most abundant salt in ocean water. When sodium chloride dissolves in water, it separates into sodium and chloride particles called ions. Other salts such as magnesium chloride, form ions in the water the same way. Together sodium and chloride make up almost 86% of the ions in dissolved ocean water. These minerals in the water make it more dense than fresh water.

Gases in Ocean Water Three gases found in the ocean are nitrogen, oxygen, and carbon dioxide. Oxygen and carbon dioxide are necessary for living things found there. Oxygen and nitrogen come from the atmosphere and from algae in the ocean. Algae uses sunlight to carry out photosynthesis, releasing oxygen into the water. Oxygen is more scarce in ocean water than it is in air and is most plentiful near the surface. Carbon dioxide on the other hand, is about 60 times more plentiful in the oceans as in the atmosphere. Algae need CO2 for photosynthesis. Animals such as corals also use CO2 , which provides the carbon to build their hard skeletons.

Temperatures in Ocean Water Ocean temperatures vary; closer to the equator are warmer temperatures, while closer to the poles temperatures are colder. Temperatures decrease with depth. Temperatures are important because they determine how much dissolved oxygen is available for living organisms.

Changes with Depth Temperature Decreases Ocean Zones There are 3 different temperature zones in the water column. The 1st zone called the surface (sunlight) zone extends from the surface to about 100-500 meters. Next is the transition (twilight) zone which extends from the bottom of the surface zone to about 1 km down. Temperatures can drop quickly here to as low as 4◦C . Finally, is the deep (midnight) zone where temperatures are about 3.5◦C or colder.

Pressure Increases Water Pressure Experiment Pressure and Density Demo Pressure is a force exerted by the weight of water above pressing down. Pressure increases continuously from the surface to the deepest part of the ocean. The average depth of the ocean floor is 3.8 kms. There the pressure is about 400 times greater than air pressure on the Earth’s surface.

Summarize what you have learned! G:\water\ocean\oceanography\information\four factors affect sea water key.doc