DO NOW• From what you learned and observed in the density investigation,

hypothesize what you think happens in the red areas on the map shown, and why you think this (think about density of water and temperature!)

Objectives

• To understand role of density and movement of water in ocean circulation

• To apply this knowledge to your island

OCEAN CURRENTS

current •mass of water moving from

one place to another•like a river within the ocean

importance:

•moves drifting organisms from place to place – plankton, disperses young

•carries eggs and larvae of organisms that have external fertilization

•brings food, oxygen•carries away waste,pollutants

three types of currents

• surface currents

• thermohaline circulation (currents)

• wind-driven vertical currents (upwelling)

surface currents•wind driven currents•occur at surface•horizontal currents•caused by friction between wind

and water - wind pushes water

surface currentsCoriolis effect•causes moving objectsin northern hemisphereto veer clockwise•causes moving objectsin southern hemisphereto move counter-clockwise

surface currentsCoriolis effect

surface currentsgyre•massive circular system of wind-driven

surface currents•cover whole oceans•clockwise inNorthern hemisphere•counter-clockwisein Southernhemisphere

Surface currents

Which current(s) directly affect the island?Where do you predict oil would travel if a spill occurred?

thermohaline circulation (currents)•causes deep ocean circulation•vertical currents•Temperature (thermo) and salinity

(haline) cause water density differences•due to density differences, water

masses rise and fall

thermohaline circulation (currents) REMEMBER THE DENSITY LAB?

↑ salinity = ↑ density = water mass sinks↑ temp. = ↓ density = water mass floats

thermohaline circulation (currents)

•when combined with surface currents, results in conveyor belt movement of water around globe

•Wind blows surface currents to colder areas-> Water cools -> becomes dense and sinks -> Thermohaline circ. moves water to equator-> water warms and rises

wind driven vertical currents = upwelling•wind blows, moves water

away, causes new water to rise up to replace it

Areas of Upwelling= Increased productivity

• Colder, denser water from deep ocean is more nutrient rich than warmer water at surface.

• Areas of upwelling usually indicate higher primary production

• Higher primary production= more primary consumers, more secondary consumers, etc.

• 25% of global fish catch come from 5 areas of upwelling that equal 5% of ocean area!

Global Wind Patterns

Based on the location of the island ( ), where on the island would upwelling occur?How would this affect marine ecosystems around the island?