Motion in the Ocean Ocean Currents • Warm currents flow AWAY from the equator and towards the poles • Cold currents flow TOWARDS the equator from the poles Why is Ocean Circulation Important? It transports heat from the equator to the poles It transports nutrients and organisms – it returns oxygen to the system and stirs up food from bottom It influences weather and climate It influences commerce What are Currents? Ocean currents are rivers of circulating waters found in the ocean There are two types: Surface Currents- the upper 400m of the ocean (10%) Deep Water Currents- Thermal/Salinity currents (90%) Surface Ocean Currents Make up 10% of the oceans’ waters Up to a maximum depth of 400 meters Broad, slow drifts that NEVER cross the equator Mostly wind generated Create gyres- enormous circular currents Importance of Surface Currents Migration Navigation Weather Deep Ocean Currents Makes up about 90% of the oceans’ water Differences in density are related to salinity and temperature which causes the waters to move up or down beneath the ocean Thermohaline Circulation Global ocean circulation that is driven by differences in densities of the sea water which is controlled by: Temperature Salinity (salt) Importance of Deep Ocean Currents Upwelling Movement of deep water to surface Hoists cold, nutrientrich water to surface Produces high productivities and abundant marine life Factors Influencing Currents The Wind Just as wind moves from high pressure to low pressure, so do our waters Winds blow across the surface creating friction and motion The water piles up because the water currents flow slower than the winds Factors Influencing Currents The Sun heats the water making it less dense and creating a convection current in the ocean Factor also referred to as water density Factors Influencing Currents Water’s Salinity Salinity means salt content Saltwater is more dense, so it sinks lower than fresh water Factors Influencing Currents The Coriolis Effect Causes water to move right in the Northern Hemisphere (clockwise) Causes water to move left in the Southern Hemisphere (counter-clockwise) Reflective Questions? 1. How are ocean currents produced? 2. Where do cold currents come from? Where do warm currents come from? 3. How do ocean’s impact climate?