marine science exam 3

most major currents are dynamically balanced between ___ and the ____.

Coriolis Effect and the pressure gradient (geostrophic balance)

surface currents are intensified along which boundaries? east or west?

western boundary of the ocean basin —> it is much stronger

true or false: la nina is an exception to normal wind and current flow

false, it is el nino.

global conveyor belt

water masses that retain their distinct properties as they sink and sort into identifiable layers and spread around the worlds oceans

where do water masses form?

at the ocean surface

define currents

mass flow of water (particles)

what are the features of thermocline currents?

• slow and deep currents driven by the pycnocline.

• depends on density differences caused by temperature and salinity

what does circulation/current system refer to?

a large and coherent flow, which is a collection of currents associated with numerous various particles

what are currents used to describe?

movement of water particles

an example of a current system

gul stream

whats the equation to calculate the current at a particular location with 2 particles?

what is ADCP?

Acoustic Doppler Current Profile

• can map location for a period of time

• sensor sends acoustic beam upward or downward

• water backscatters send acoustic signals back to the sensor

what can currents change? what is it used to calculate?

change the acoustic frequency. used to calculate currents.

list some measurements for surface currents

what does satellite altimetry measure? explain it. what else is it used to ?

measuring sea-surface height. measures the time taken by a radar pulse to travel from the satellite antennae to surface to satellite receiver. it is then used to compute surface currents.

true or false: surface currents flow around the periphery of ocean basins

true

explain the ekman spiral/transport

• wind-driven currents vary with depth due to friction

• top layer flows 45degrees to the right (N. hemisphere)

• vectors form a spiral looking down from above

• net transport is 90degrees to the right (clockwise in N. hemisphere)

• friction from top layer moving on top of second layer starts to get weaker and move

the movement of surface water is governed by ___ and ____.

geostrophic balance and wind forcing

• Ekman transport drives a horizontal sea level gradient, and a pressure gradient

• Pressure gradient balanced by Coriolis force (cross-wind direction)

hills made in the middle of the ocean are built up by what? what is their maximum height?

ekman transport

~2m

true or false: currents can go around hills

true

Be familiar with the Current systems in the Atlantic (4 systems that form a large gyre)

• Trade winds drive North Equatorial Current

• North Equatorial Current continues to become Gulf Stream

• Westerlies drive North Atlantic Current

• NAC continues to become Canary Current

Explain what WBC (western boundary currents) is.

• much stronger in speed and total volume

• westward intensification

• Coriolis and boundary effects

  • low near the equator

• they are concentrated and deep

• currents don’t turn until they hit the boundary

• narrow, strong, and deep

Explain how the EBC is different from the WBC.

• they turn quickly and spread out

  • because of strong Coriolis effects

  • weak, broad and shallow currents

why do we have westward intensification?

• in the equator there is no Coriolis so now current keeps going east down to west basin until they hit the bottom

• when they hit the bottom, there is no where else to go, so they turn

  • jammed into narrow area of the western boundary

are WBC’s warm? what coast do they flow off of?

yes! they flow off the east coast.

*values means volume of transport following the arrows —> defining how strong the current is

** the larger the number, the stronger it is

examples of WBC

gulf stream (2m/sec) (1000m, ~100km wide), brazilian current, east australian current, etc..

are EBC’s cold, sluggish, and where do they flow off of?

yes! they flow off the west coast.

examples of EBC’s

canary current, california current, peru current, etc…

define transverse currents

currents that cross the basins and link western and eastern boundary currents

what are transverse currents driven by?

trade winds

• N. and S. equatorial currents

• pacific, atlantic, indian oceans

westerlies

• N. pacific and N. atlantic current - extension of kuroshio and gulf stream

• Antarctic circumpolar current - strongest ocean current on earth (>150 sv)

  • no land blocking flow so currents go round and round

what are the six oceanic gyres? what IS a gyre?

w

what is the calm center of a gyre?

• Low winds and weak currents

• Weak mixing & high evaporation

• Low nutrients

• Receivers of biota and abiota - Trash vortex

• However, can be rich with eddies

true or false: warm water transfers heat to lower latitudes while cold water cools higher latitudes.

false, warm water transfers heat to higher latitudes while cold water cools lower latitudes.

how many currents form a gyre?

4!

in what sea does most sargassum end up in?

Sargasso sea