Properties of Water

WATER MOLECULES ARE MADE OF 2 HYDROGEN ATOMS AND 1 OXYGEN ATOM. THE HYDROGEN ATOM OF 1 MOLECULE IS ATTRACTED TO THE OXYGEN ATOM OF ANOTHER MOLECULE – HYDROGEN BONDING The Structure of Water

Specific Heat of Water Because of the hydrogen bonding of water, it has a high specific heat  This means that it can hold a lot of heat  It heats and cools slowly

Specific Heat The amount of heat required to change the temperature of 1g of a substance by 1 degree celcius. In other words, the amount of heat required to change the temperature of a substance Higher specific heat means it’s harder to warm something up.

Water Density & Temperature Water is most dense at 4 o C (39 o F) when atoms are closest to each other Atoms spread out when forming ice and vapor The Structure of Ice The Structure of Water (Liquid) The Structure of Water Vapor

Water Density in the Ocean Ocean water temperatures range from - 2 o C to 30 o C (28 o F-86 o F) In the ocean, the densest water is at the bottom and the least dense is at the top Lowest Density Highest Density Mixed Layer

Surface Zone:  2% of ocean water is found in the surface zone  Lowest density, lowest salinity and highest water temperatures Transition Zone:  18% of ocean water is found in the transition zone  The layer is in between the warmer surface zone and the colder deep zone  The thermocline and pycnocline are located in the transition zone Deep Zone:  80% of ocean water found in the deep zone  Sunlight never reaches the deep zone  Water temperature is only a few degrees above freezing  Highest density, highest salinity, lowest temperatures Three Ocean Layers:

Deep Currents: Water Density and Salinity 3-5% of ocean water is salt – known as salinity The greater the salt content, the denser the water is The ocean water is layered with the greatest amount of salinity at the bottom – halocline Most ocean salt comes from weathered rocks on the land

Changes in Salinity The salinity of ocean water can be increased by removing surface water  Evaporation  Ice/Glacier Formation The salinity of ocean water can be decreased by adding surface water  Precipitation  Melting of Ice/Glaciers  Water Runoff from Land

Thermohaline Current Changes in the density of water results in a worldwide circulation of water Density differences are created by changes in temperatures and salinity levels

Water is heated at the Equator by the Sun and spreads outward towards the Polar Regions by the wind Water is cooled in the Polar Regions, increasing the density, then sinking to the bottom of the ocean – Downwelling Water spreads outward (towards the Equator) on the bottom of the ocean floor Water is cooled in the Polar Regions, increasing the density, then sinking to the bottom of the ocean – Downwelling Water spreads outward (towards the Equator) on the bottom of the ocean floor Creation of the Thermohaline Current Thermal Expansion - objects expand when heated

Continuation of Water Movement Surface winds push the coastal water outwards to the ocean, pulling water up from the ocean floor - upwelling

Heat Exchange from the Thermohaline Current The Polar Regions are warmed by the warm currents Releases heat into the atmosphere as the water cools Helps increase the temperature as much as 41 o F The Equator is cooled by the cool currents The cold currents absorb heat from the atmosphere Helps cool the Equator by as much as 30 o F

CIRCULAR MOVEMENT OCEAN CURRENTS CREATED BY WIND AND EARTH’S ROTATION SPINNING RESULTS FROM THE CORIOLIS EFFECT Ocean Surface Currents What is an Ocean Gyre?

Coriolis Effect The spinning of Earth causes objects to move in a curved line across Earth’s surface This movement causes the gyres to move clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere vgeaI

North Atlantic Gyre Each gyre is made up of several smaller surface currents North Atlantic Gyre:  Gulf Stream Current  North Atlantic Current  Canary Current  North Equatorial Current Characteristics:  Western Stream (Gulf Stream Current) – warm, narrow, deep, fast-moving  Eastern Stream (Canary Current) – cold, wide, shallow, slow-moving Gulf Stream Current N. Atlantic Current Canary Current N. Equatorial Current

Influence of the Wind The currents that form the gyres following the direction of the wind  Easterlies – move the Gulf Stream Current northeast towards Northern Europe  Westerlies – move the Canary Current southwest towards South America and Mexico

Effects of Global Warming Surface warming of the water and increased freshwater (melting glaciers) Reduces downwelling No surface cooling Reduction of water circulation (loss of 20-50% of the water movement)

Impacts of Weakening Thermohaline Current Europe will experience a cooling trend (“The Big Freeze” last happened 12,800 and 11,500 years ago) Glacial tundra in Scandinavia Increased glaciation in mountain ranges worldwide More dust in the atmosphere from deserts in Asia Drought worldwide Cooling of Western North America and South America Extinction of many species

Weakening of the North Atlantic Currents The ocean circulation of the Gulf Stream Current has been reduced by 30% in 2005 The North Atlantic Current & Norway Current has basically stopped in 2010 These currents work to:  keep Ireland and the United Kingdom mostly ice free  the Scandinavia countries from being too cold  the entire world from entering into another Ice Age Normal Current Movement Current Movement – August 2010

Coastal vs. inland climate Because water has a high specific heat, its temperature will undergo very little changes. Thus, coastal areas close to the ocean tend to have moderate temperatures with a low variation in temperature. Areas further inland will be farther from the ocean and will thus experience larger variations in temperature.

Surface Currents vs. Density Currents Surface Currents: Movement in ocean caused by wind Moves horizontally Is on ocean surface Density Currents: Movement in ocean caused by differential salinity and temperatures of water Moves vertically, relative to the surface currents Involves upwelling and downwelling

Horizontal movement: Surface currents Density differences, sunlight, and wind cause currents Ocean currents play a major role in maintaining Earth’s heat balance: Heat is transferred from the tropics (near the equator) where there is excess heat, to the polar region where there is less heat

Vertical movement: Density currents Upwelling – water rich in nutrients from the bottom rises (excellent for fisheries!) Downwelling – water rich in dissolved gases sinks (brings O 2 to deep-water life!)