Ocean Currents “There are rivers in the oceans” -- Matthew Maury, Father of Oceanography

The Earth is not evenly Heated! At the poles: incoming radiation travels through more atmosphere, is spread across more surface area, and is reflected by ice. The Earth is not evenly Heated! Net radiative heat gain in the tropics Net radiative heat loss at the poles

The equator gets more concentrated solar energy.

Seasons: because of the tilt, NOT getting closer/farther to the sun

Earth’s Rotation and Wind Earth rotates west to east – surface at the equator moves faster than at poles Atmosphere also rotates at the same speed as surface Wind gets deflected – coriolis effect Coriolis effect – due to earth’s rotation, objects in northern hemi deflect right, objects in the southern hemi deflect left.

Coriolis effect on moving things An object moving across a rotating surface keeps the same direction and speed, but it appears to curve if you are on the rotating surface. In the fixed frame of reference, the black ball moves in a straight line. However, the observer (red dot) standing in the rotating frame of reference sees the object as following a curved path.

Deflection

Earth is consistently warmer at the equator; convection causes air at the equator to rise, air at the poles to sink, forming large planetary winds.

Convection + Coriolis cause winds blowing at these angles across the planet these are “planetary winds” that blow nearly all the time!

Planetary winds are disrupted and modified over land on a daily basis but are nearly constant over the oceans since they are “flat” and uniform.

“Westerlies” “Trade winds” brought the Europeans over to the Americas, sent them back

If the winds are blowing like this, what direction do you predict the ocean surface currents will be moving at the equator?

Basic Wind-Driven Currents

Western vs. Eastern boundary vocabulary to know

Try the Pacific

Which Currents Are Western Boundary Currents?

Why Are Some Red and Some Blue?

Which Side of all the continents have warm currents Which Side of all the continents have warm currents? What direction do all of the warm currents flow?

Which Side of all the continents have cold currents Which Side of all the continents have cold currents? What direction do all of the cold currents flow?

Western vs. Eastern currents WESTERN BOUNDARY: EASTERN BOUNDARY: HOT and FLOWS TOWARD POLE COLD and FLOWS TOWARD EQUATOR

The Primary Sources of Water Movement 1. Solar Heating 2. Winds 3. Gravity 4. Coriolis

Two types of Currents: Surface Currents: These waters make up about 10% of all the water in the ocean. These waters are the upper 400 meters of the ocean. Deep Water Currents: Thermohaline Currents These waters make up the other 90% of the ocean These waters move around the ocean basins by density driven forces and gravity. The density difference is a function of different temperatures and salinity These deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.

Surface Ocean Currents Broad, slow drifts; never cross equator Wind generated; circular gyres

IMPORTANCE OF SURF. CURRENTS NAVIGATION MIGRATION WEATHER

Localized Surface Currents Longshore Current. Flows parallel to shore; move sediment

RIP CURRENT - Caused by converging longshore currents - Very dangerous ; Red Flag - DO NOT fight rip current; swim parallel to shore to get out of channel

Deep Ocean Currents Flow beneath surface; cross equator Separated from surface currents by boundary called a “Thermohaline” (diff in densities) Move North to South

Upwelling brings cold water from deeper regions to surface Cold, nutrient-rich water rises to replace the surface water (good for fishing- Peru) process is dominant when winds are parallel to coastline

Currents to know by name California Current North Equatorial current Gulf Stream North Atlantic drift Canary Current And in general be able to use these terms: “Western boundary current” “Eastern boundary current”

Do you see any patterns? The Gulf Stream is a good example of a Western Boundary Current

Gulf Stream

What direction do north oceans spin What direction do north oceans spin? What direction do south oceans spin? Clockwise or counter clockwise?

These spins are called Gyres there are 5 major gyres

Big Picture Things To Know About Unequal heating of the Earth, convection and Coriolis work together to set up predictable planetary wind patterns These constant winds in turn set up constant ocean currents – know the currents mentioned by name and location The ocean currents bring warm water to the west side of all the oceans, cold water to the east side of all the oceans – know which side and what temperature a “western boundary current” would be on in an ocean Currents account for about 40% of global heat transport