MEA 200: OCEAN CICRULATION

ITCZ

Intertropical Convergence Zone

On what sides of the Gulf stream are cold-core and warm-core eddies each found after their formation?

-COLD-CORE EDDY→ cool shelf water is trapped within a CCW flowing meander when it "pinches off," will be on the OCEAN-SIDE of the gulf stream.-WARM-CORE EDDY→ warm Sargasso Sea water is trapped within a CW flowing meander when it "pinches off," will be on the LAND-SIDE of the gulf stream.

How are eddies formed from meanders in the Gulf Stream?

-Eddies form because the Gulf Stream can move laterally at a rapid pace.-Partly as a result of its contact with the edge of the continental shelf and slope, the current may meander.-Usually, these meanders intensify so much that they break off, creating a rotating ring of what was very warm Gulf Stream water around a stationary core of cool or warm water.

How long do each of these eddies last before they lose their identity - what causes them to disappear?

-They eventually disappear because of internal friction from the water. -Warm-Core Eddies are quick to spin down and are quickly dispersed into the ocean. -Cold-Core Eddies last longer because they are in deep ocean water and don't spin down as fast

What is the depth of frictional influence, how deep does it normally extend, and how is the Ekman Transport related to it?

-depth at which motion ceases -100-150m -Ekman transport includes all movement up to depth of frictional influence

How does the Ekman Transport cause coastal upwelling (the vertical upper-ward movement of water)? and what are the favorable wind directions (relative to the coastline) for upwelling to occur? What about coastal downwelling?

-upwelled water comes from below the surface exchanging water upward across thermocline

Why does the Gulf Stream in the North Atlantic have a much larger volume transport than the comparable Brazil Current in the South Atlantic?

Balance of Vortices?Increased Coriolis Effect?

The water inside the core of each of these eddies comes from what two locations?

COLD-CORE EDDY and WARM-CORE EDDY

geostrophic current

Coriolis effect balances down-slope component of gravity

What are gulf stream eddies?

Eddies are rotating rings of very warm water with warm- or cold-water cores, found on both sides of a western boundary current such as the Gulf Stream.

How does the Ekman Transport cause equatorial upwelling?

NE and SE trade winds converge at the equator (ITCZ) -ET set up causes a horizontal divergence of surface water away from the equator

In what direction do their rings rotate when they break off?

The DIRECTION OF ROTATION of the rings around these eddies is the same as that of the meanders just before it breaks off.

In addition to the Gulf Stream, which of the following currents also are intensified: Kuroshio, Brazil, Canary or California?

The Kuroshio Current

Ekman transport

The net motion of the water including average velocity of all lamina in spiral

Would the intensification occur if the earth did not rotate around its axis?

The only way to achieve the balance of these 3 vorticity's is to intensify the current in the western side of the ocean basin. This imbalance of CE results in a stronger northward flow of water on the western side of the subtropical gyre and a broad equator-ward flow over most of the eastern side of the ocean basin.

Why must the GC always have a 90 deg angle relative to the cross-section between the two stations?

This current will always be running perpendicular to that cross-section.

What winds are the primary driving force of the Atlantic Ocean currents?

Trade winds and prevailing westerlies

How can ocean temperature and salinity (both conservative properties) be used in the tracing of water masses under the ocean surface using a T-S Diagram?

We actually trace these water masses using a plot of temperature and salinity called a T-S Diagram -water masses have 'characteristic' features that identify them visually on the T-S Diagram and make them easy to recognize.

What three rotational (vorticity) forces, when balanced, cause this intensification?

Wind stress, frictional stress, Coriolis effect

How can Newton's first law of motion be used to explain and understand the formation and maintenance of the Geostrophic current that results from this balance?

a mass in motion will have a curved path or will a/deccelerate, if the forces acting on it are not balanced

Newton's first law of motion

an object in motion will remain in motion unless acted upon by another force

conservative and non-conservative properties of a fluid

conservative: changed by advection

If the sea surface slope has already been determined, why do you need to know which hemisphere you are in before the direction of the geostrophic current can be determined?

if in N hemisphere, GE flows to right (out of screen) S. Hemisphere, GE flows left (in screen)

wind drift currents

the ocean currents driven by the wind

In what direction does the sea surface slope if you know that one station has a lower average density than the other?

the one with the lowest density will be higher and sloping downward

According to Ekman, when the wind blows on the ocean surface, in what direction and angle, relative to the wind, does the top most layer ("lamina") of the surface water move? Why?

the top most layer moved 45 degrees to the right of the surface wind direction -because of CE

How is the Ekman Spiral created and what does it represent?

think of it as a spiral staircase -layers set into motion by wind and top most layer moves to R at 45d. -surface layer sets layer beneath it into motion etc. -each layer is deflected more to the right than the previous (lower velocity) -represents wind drift currents

Wind stress

trade winds moving toward west and prevailing westerlies moving east create a strong clockwise frictional vorticity

How can you determine sea surface height at, and sea surface slope between, two hydrographic stations in the ocean using a knowledge of the average water density at each station?

use given conditions to determine which has higher density. The one with the lowest density is the taller one

what is the difference between currents on the western side of an ocean basin and eastern side currents?

west: fast narrow extend to greater depths east: slow wide, shallow

downwelling

winds blow from the south parallel to western coastline ET moves towards the coast

what are the favorable wind directions for upwelling to occur

winds must be blowing parallel with the coastline, ET moves away from coast North Hemisphere: north wind parallel with a western coastline