OceanographyChapter 25

Eddie Hughes By

Block 3

• Water in ocean• Mixture of water and more than 70 chemical

elements• Measure of amount of chemical elements

salinity– Ocean 3.5 percent salinity– Mineral salts – sodium, chloride, sulfur, and

magnesium

Seawater

• Circulation of water throughout the ocean• Two main types– First type is wind-driven• Move upper parts of ocean current horizontally• Planetary-scale prevailing winds create current• Gulf stream major wind-driven current• California current moves cold arctic waters southward

Ocean Currents

• Aspects of wind-driven ocean currents– Vertical distribution of heat – Called upwelling– Moves surface waters from equator to continents– Warm water replaces by cooler deeper water– Brings cool, nutrient-rich water up– Linked to changes in global climate patterns

Ocean Currents ( continued )

• Second type is thermohaline circulation– Thermo means heat, haline means salilinty

• Driven by temperature and salinity• Cold waters of North Atlantic Ocean– Create cold, saline-rich water that sinks– Creeps along bottom until reaches upwelling

zones– How nutrients and heat are circulated

Deep Ocean Circulation

• Euphotic – top zone– Enough sunlight for photosynthesis– Extends no deeper than 600 feet

• Disphotic zone– Small amount of sunlight– No photosynthesis– Depth 3,000 feet

Life Zones in the Ocean

• Aphotic zone – No light at all– Strange species of aquatic organisms

• Benthic zone– Subject to extreme pressure – near freezing– Composed of thick mudlike sediments• Can be more than 1 mile thick

Life Zones in the Ocean ( continued )

• Important feature of the ocean– Thermocline • Area where:

– Warm, nutrient-poor mixes with cold, nutrient-rich water

• Area of extreme temperature change• Depths varies from 50 to more than 600 feet• Organisms migrate to thermocline as depth changes

Life Zones in the Ocean ( continued )

• Shallow, sloping area around margins of continents

• Average depth of 400 feet• Most are in the euphotic zone• Support a variety of aquatic life– 90 % of all fish and shellfish

• Stretch out about 45 miles– Can be up to 900 miles

Continental Shelves

• Along edges of shelves deep submarine canyons

• Depths up to 12,000 feet• Associated with world’s largest rivers• Shaped by sediments and currents from rivers• Submerged Canyon from Hudson River– 3,600 feet deep and 5 miles wide

Continental Shelves ( continued )

• Areas along shore– Within reaches of low and high tides

• Harbor abundance of life– Consist of shorelines and tidal pools

• Harsh aquatic environment– Rise/fall of water– Strong currents– Wave action– Periodically exposed to air

Intertidal Zone

• Two basic types:– Rocky intertidal • Composed of large rocks that line the shore

– Sandy intertidal• Made up of mostly sand

– Both have their own unique organism communities

Intertidal Zone( continued )