Hon Environmental Science HYDROSPHERE NOTES The Hydrosphere and the Water Cycle: Water cycle: The continuous movement of water into the air, onto land, and then back to water sources. Evaporation: the process by which liquid water is heated by the sun and then rises into the atmosphere as water vapor. Change in state from a liquid to vapor or gas. Evapotranspiration: The sum of evaporation and transpiration (the release of water from plant leaves). Condensation: water vapor forming water droplets on dust particles. Change in state from vapor or gas to a liquid. Precipitation: The process that occurs when condensed water droplets collide, stick together, and create larger, heavier droplets that fall from clouds as rain, snow, sleet, or hail. 1
Earth s Oceans The four major oceans are the Atlantic, Pacific, Arctic, and Indian Oceans, all of which are joined into a single, large, interconnected body of water called the World Ocean. Ocean waters cover 70% of the Earth s surface and plays a major role in regulating temperatures on planet Earth. Considering the four oceans separately, how do their sizes compare? Rank them below from #1-4 (#1 as the largest and #4 as the smallest). 1. Pacific 2. Atlantic 3. Indian 4. Arctic Which ocean has most of its surface covered by floating ice? The Arctic Ocean Ocean Water Ocean water differs from freshwater because it contains more salts, which have dissolved out of rocks on land and been carried through rivers into the ocean over millions of years. The term Salinity refers to the concentration of all of the dissolved salts contained in the ocean. Temperature Zones of the Ocean Water in the ocean can be divided into three zones based on temperature: the surface zone, the thermocline zone, and the deep zone. Let s look at the graph in more detail 2
Global Temperature Regulation One of the most important functions of the world ocean is to absorb and store energy from sunlight, which regulates temperatures in Earth s atmosphere. The world ocean absorbs over half of the solar energy that reaches the Earth s surface. Remember, from chemistry that water has a high specific heat capacity meaning it takes a lot of energy to change the temperature of 1 g by 1⁰C. So, the ocean absorbs and releases that solar energy much more slowly than land. As a result, the temperature of the atmosphere changes more slowly as well. If the oceans did not regulate atmospheric and surface temperatures, the temperatures would be too extreme for life to exist. Local temperatures in different areas of the world are also regulated by the oceans. Currents that circulate warm water cause the land areas they flow past to have more moderate climates. Ocean Currents There are two types of Ocean Currents: 1. Surface Currentsa. Streamlike movements of water at or near the surface. b. Currents are wind driven from global wind patterns c. Include warm and cold water currents that do not readily mix d. Influence land climates that they flow past e. Upper 400m or the ocean 2. Deep Currents a. Streamlike movements of water that flow very slowy along the ocean floor b. Occurs when cold, dense water from the poles sinks below warmer, less dense ovean water and flows toward the equator. c. Antarctic Bottom Water (Antarctica 40⁰ north latitude takes several hundred years) 3
Ocean Currents are influenced by two types of forces: 1. Primary Forces start the water moving The primary forces are: Sun & Solar heating Wind Gravity Coriolis Effect 2. Secondary Forces influence where the currents flow. These forces work together to produce a large current of water called a gyre. Why are the gyres circulation in different directions in the north and south hemisphere? Due to the direction of wind- Winds spiral to the right in the northern hemisphere and to the left in the southern hemisphere due to the Coriolis Effect. The North Atlantic Gyre is separated into four distinct Currents: The North Equatorial Current, the Gulf Stream, the North Atlantic Current, and the Canary Current. *These currents will be very important later in the year when we study global climate change! 4
Global wind patterns influence surface ocean currents. 5
Let s not forget that Earth s land features play a major role in climate regulation as well! Fresh Water Most of the water on Earth is salt water in the ocean (~97%). The remaining water on Earth is fresh water, but of that most of the fresh water is tied up icecaps and glaciers. So, there is very little readily available fresh water on Earth. Where does the readily available fresh water come from? Lakes Rivers Wetlands The soil Rock layers below the surface The atmosphere A river system is a network of streams that drain an area of land. It includes the main river and all of its tributaries. Ground Water Rain or melting snow that trickles down through the ground and collects. Ground water accounts for only 1% of all water on Earth, but fulfills the human need for fresh drinking water and water for agriculture and industry. An aquifer is a rock layer that stores and allows for the flow of ground water. 6