Water is recycled continually between the ocean and the land The reservoirs of water include: –Oceans: cover 60% of the northern hemisphere cover 80% of the southern hemisphere contain 97% of Earth’s water –Rivers, lakes and glaciers –Groundwater contains a larger volume of water than all of the combined water in lakes and rivers
The hydrologic cycle describes the exchange of water between ocean, land and atmosphere. –On land precipitation exceeds evaporation. –In the ocean evaporation exceeds precipitation.
Heat vs Temperature Heat –energy produced by the random vibration of atoms or molecules Temperature –an objects response to the input or removal of heat energy
Heat Capacity the heat required to raise the temperature of 1 gram of a substance by 1 o C Heat capacity of water = 1 calorie –the highest of all known substances water resists changing temperature when heat is added or removed
Density and Temperature density of water increases as water is cooled until a maximum of 1 g/cm 3 is reached at 4 o C the density decreases as freezing takes place ice is less dense than water
Fig 6-3, p.110 Why does ice float – ice is less dense than (liquid) water
Seawater vs. Pure Water Seawater has a –lower heat capacity –lower freezing point density increases until freezing point is reached –ice is pure water & cold, salty water left behind sinks
Density of Water Depends on temperature and salinity density increases as temperature decreases density increases as salinity increases
Fig 6-8, p.114 Temp., Salinity and Density have a complex relationship – you can have the SAME density at different concentrations of Temp. and salinity.
Density Zones in the Ocean 1. surface zone or mixed layer –temperature and salinity are constant with depth 2. a middle layer where density changes rapidly with depth (because of extreme env. changes) = pycnocline –Thermocline: temp. changes rapidly w/ depth –Halocline: salinity changes rapidly w/ depth –NOTE: These 3 zones can ALL coincide together! 3. The DEEP ZONE (80% of all ocean water) is the layer below the pycnocline (but little change occurs here).
The Surface Layer About 100m thick Comprises about 2% of the ocean volume Is the most variable part of the ocean because it is in contact with the atmosphere. Is less dense than the layers below because of its lower salinity or higher temperature.
The Pycnocline Is transitional between the surface and deep layers. Comprises 18% of the ocean basin. In the low latitudes, the pycnocline coincides with the thermocline. In the mid-latitudes it coincides with the halocline.
The Deep Layer Represents 80% of the ocean volume. Water in the deep layer originates at the surface in high latitudes, where it: –cools –becomes dense –sinks to the sea floor –flows equatorward across the ocean basin
The water column in the ocean can be divided into the: –surface layer –pycnocline –deep layer
Sea Surface Temperatures Insolation and ocean-surface water temperature vary with the season. Ocean temperature is highest in the tropics (25 o C) and decreases poleward.
Tropical and subtropical oceans are permanently layered with warm, less dense surface water separated from cold, dense deep water by a thermocline. –The thermocline is a layer in which water temperature and density change rapidly. Temperate regions have a seasonal thermocline and polar regions have none.
Density Zones in the Ocean 3. the deep zone –a cold (1 to 3 o C), dense layer on the bottom –most of the ocean (80%)
Refraction, Light and Sound Refraction: The “bending” of waves. Light and Sound are a direct result/reaction of these waves. Light and Sound waves travel at DIFFERENT speeds depending upon the medium that they are in.
Light in the Ocean Sunlight does NOT penetrate (always) to the “bottom.” This is because of many factors such as turbidity (sediments in the water), depth and the scattering/absorption of light through a water medium. Scattering determines how light is absorbed. Water thus absorbs (and scatters) the light PHOTIC vs. APHOTIC zones
Slide 50Fig 6-12b, p.117 Different wavelengths of light produce different colors. As they are “absorbed/scattered” in the water the colors reach different depths. Why buy a RED wetsuit?
Slide 51 Fig. 6-12c, p. 117 “regular” ocean light penetration – blue dominates
Slide 52 Fig. 6-12d, p. 117 strobe light penetration – blue HUES (+ other colors) dominate
SOUND Similar to light – sound “waves” travel differently through water. Speed of sound in average seawater (w/ average salinity) is 1500 m/sec.
Fig 6-13, p.118 Relationship between water depth and sound velocity.
Fig. 6-14, p. 119 sofar layer, in which sound waves travel at minimum speed
Fig. 6-16c, p. 120 A side-scan sonar image of the SS Nailsea Meadow resting on the seabed at a depth of 113 meters (367 feet).
What does this mean to MARINE LIFE? Light effects WHERE plants and animals can live. Temperature effects WHERE plants and animals can live. Salinity effects WHERE plants and animals can live. Dissolved gases are an important factor too.
Fig 12-8, p.243 Open ocean (clear) vs. coastal (sedimented) waters
In turbid coastal waters light rarely penetrates deeper than 20m. –The water appears yellow to green because particles reflect these wavelengths. Fnft: Yangtze River
Fig 12-9, p.244 Photic vs. aphotic zones – light penetration @ diff. depths.
Fig 12-10, p.245 Temperature relationships in different ocean environments