ENVIRONMENTAL SCIENCE Chapter 3 The Dynamic Earth 3.3 The Hydrosphere and Biosphere

3.3 The Hydrosphere and Biosphere Objectives Name the three major processes in the water cycle. Describe the properties of ocean water. Describe the two types of ocean currents. Explain how the ocean regulates Earth’s temperature. Discuss the factors that confine life to the biosphere. Explain the difference between open and closed systems.

The Hydrosphere and Water Cycle The hydrosphere includes all of the water on or near Earth’s surface including clouds, groundwater, rivers, polar ice caps, and oceans. The water cycle is a conceptual model that illustrates the continuous movement of water into the air, onto land, and back to water sources such as oceans. The three major processes involved in the water cycle are evaporation, condensation, and precipitation.

The Hydrosphere and Water Cycle Evaporation is the process by which liquid water is heated by the sun and absorbs enough energy that molecules break away and rise into the atmosphere. Condensation is the process in which water vapor condenses to form water droplets on dust particles in clouds and the water droplets collide and stick together creating heavier droplets. Precipitation is the process when the water droplets formed in clouds fall back to the earth in the form of rain, snow, sleet, or hail.

Earth’s Oceans The Atlantic, Pacific, Indian, Arctic, and other oceans actually combine to form one “world ocean” which covers a little over 70% of Earth’s surface. The Pacific Ocean, the largest part of the world ocean, covers 165,640,000 km2 with an average depth of 4,280 m. The deepest place in the world ocean, Challenger Deep, is located east of the Philippine Islands at the bottom of the Mariana Trench at a depth of 11,033 m. Challenger Deep is deeper than Mt. Everest is tall. Surface currents in the Pacific generally move in a clockwise direction north of the equator and counterclockwise south of the equator.

Earth’s Oceans The Atlantic Ocean covers 81,630,000 km2 of Earth. The current flow in the Atlantic is similar to that in the Pacific. The Indian Ocean covers a surface area of 73,420,000 km2 and has an average depth of 3,890 m. The Arctic Ocean covers about 14,350,000 km2 and is mostly covered with pack ice.

Earth’s Oceans Ocean water contains dissolved solids (salts) that accumulate as water is constantly input from streams and rivers and volcanic eruptions. Most of the salt in the ocean is sodium chloride. Full strength sea water is about 3.5% (or 35 parts per thousand) salt by weight.

Earth’s Oceans The salinity of ocean water is lower in areas where there is much rainwater or freshwater input and higher in areas with little rainwater input and much evaporation. Ocean water can be divided into three temperature zones. Surface zone is the top 100 meters which is heated by the sun and mixes with lower zones because of surface currents Thermocline is a zone in which the temperature drops very rapidly Deep zone extends from just below the thermocline to the bottom of the ocean with an average temperature of 2°C.

Earth’s Oceans One of the most important functions of the world ocean is to absorb and store solar energy. The temperature regulation of Earth’s atmosphere is dependent on the ocean’s ability to absorb and store solar energy. Over half the solar energy that reaches Earth’s surface is absorbed by the ocean. The ocean both absorbs and releases heat more slowly than land.

Earth’s Oceans The ocean’s ability to slowly absorb and release heat has a moderating effect on Earth’s atmosphere and provides a stable range of physical parameters that are necessary for life to exist on Earth. Ocean currents also carry heat to other places that would otherwise be much cooler. For example, the Gulf Stream carries warmer water north in the Atlantic Ocean which provides enough heat energy that there are palm trees on the coast of Ireland

Earth’s Ocean Surface currents, stream-like movements of water at or near the surface of the ocean, are driven by the wind of global wind patterns. Surface currents may be warm water or cold water currents. Currents of different temperature do not readily mix with one another resulting in currents being able to flow for some distance and maintain their heat.

Earth’s Ocean Stream-like movements that flow very slowly on the ocean floor are deep currents. Cool, dense water from the poles sink below warmer, less dense water and flows toward the equator. The Antarctic Bottom Current is fed by the coldest and densest ocean water as it flows slowly north. This water takes several hundred years to flow from the Antarctic up to about 40° latitude.

Fresh Water Fresh water makes up only about 3% of the water on Earth. Much (about 2/3) of the fresh water on Earth is tied up in glaciers. For example, the ice sheet that covers Antarctica is about the size of the United States and can be up to about 3 km thick. A river system is a network of streams that drains an area of land.

Fresh Water Tributaries are smaller streams that flow into larger ones. The Mobile Bay watershed is the fourth largest estuary in the country.

Groundwater Rain and melted snow and ice sink into the ground and runoff the land. Water that trickles down into the land becomes part of the groundwater. We are very dependent on groundwater for agricultural, industrial, and domestic purposes, though it makes up less than 1% of the water on Earth. An aquifer is a porous layer of rock that allows for the storage and flow of groundwater. The recharge zone is the point on land where water enters the aquifer.

Water Characteristics Water is often called a “universal solvent” – a substance in which materials dissolve easily. Water has a high boiling point and a high freezing point when compared with similar chemical compounds. Water is denser in the liquid form (at about 4°C) than in solid form. Water also provides a medium for most chemical reactions that are important to life.

Water Characteristics A water molecule is made of two atoms of hydrogen and one atom of oxygen. Water molecules are polar because the sides have different electrical charges. Other polar substances dissolve readily in water.

The Biosphere The biosphere includes all life on Earth, which has a very narrow range of about 11 km below sea level (deepest parts of the ocean) to about 9 km above sea level (where insects, pollen, and bacteria spores have been collected). Several important factors contribute to the existence of life on Earth. Liquid water Temperatures between 10°C and 40°C Source of energy (solar) Continual recycling of the elements Gravity (maintains the atmosphere)

The Biosphere Plants on land and in the ocean depend on solar energy for conversion to chemical energy. Ecosystems, in turn, are concentrated in areas where the capture of this solar energy takes place.

Energy Flow in the Biosphere The Earth is an open system with respect to energy as it is constantly input into the biosphere through solar energy being converted to thermal and chemical energy. Earth is a closed system with respect to matter because no significant amount of matter is input into the Earth system or leaves the Earth system. The cycling of elements in the Earth system is necessary for life to exist in a closed system with respect to matter.

References The Water Cycle - http://watercycle.gsfc.nasa.gov/ Sea Salts - http://earth.usc.edu/~geol150/variability/deepocean.html Salinity Graph - http://www.coastal.edu/science/marine/msci302/mb3_files/v3_document.htm Ocean Temperature Zones - http://www.bigelow.org/collaboratory/tempback.html

References Gulf Stream Thermal Image - http://nsm1.nsm.iup.edu/hovan/classes/GEOS103_801/GEOS103_801_outline.html Palm Tree in Ireland - http://mywebspace.quinnipiac.edu/bwhite/Ireland/MorePictures.htm Ocean Surface Currents - http://ic.ucsc.edu/~wxcheng/envs23/lecture6/lect6_prnt.htm Water Masses in the Atlantic Ocean - http://www.jochemnet.de/fiu/OCB3043_18.html

References Mobile Bay Watershed – Poster in back of room with multiple sponsors listed on bottom. Principal United States Aquifers - http://www.classzone.com/books/earth_science/terc/content/investigations/es1406/es1406page10.cfm Biosphere Concentration - http://oceancolor.gsfc.nasa.gov/SeaWiFS/TEACHERS/sanctuary_7.html Water Molecule - http://fig.cox.miami.edu/~cmallery/150/chemistry/chem.htm