ocean circulation and currents I

forces involved in maintaining wind driven currents

wind drag, skin drag, form drag

define the 3 different types of drag

wind drag - as wind moves across water, air molecules collide with water molecules, transferring energy to water

skin drag - drag that would be felt if air-ocean interface was flat

form drag - additional dra caused by rough air-ocean interface

main 3 types of circulation gyre

subtropical, subolar, antarctic circumpolar gyre

characterises gyre circulation

sense of flow, elevation of water

direction of flow of subtropical gyres

in the northern hemisphere flow clockwise, in the southern hemisphere flow anticlockwise

direction of flow in subpolar gyres

in the northern hemisphere flow anticlockwise, in the southern hemisphere flow clockwise

difference in elevation between subpolar and subtropic gyres

subtropic gyres are higher than the average, regardless of hemisphere, subpolar gyres are the opposite

define Sverdrup and give the unit

a flow of one million cubic meters per second (Sv)

what environmental impact does gyre circulation have

leads to accumulation of plastic debris called garbage patches

what do elevations and depressions in the sea surface cause

development of pressure gradients in the ocean

the type of current causing depressions

diverging currents

the type of current causing elevations

converging currents

define cyclonic circulation

circulation around negative anomalies of sea surface elevation or negative pressure anomalies

define anticyclonic circulation

circulation around positive anomalies of sea surface elevation or positive pressure anomalies

explain how an ekman spiral forms

uniform wind blowing over the ocean without the interferene of land masses

forces causing an ekman spiral

viscous friction between wind and surface waters, viscous friction between successive layers of water from the surface down the water column, coriolis force

define convergence

downwelling or sinking of water

define divergence

upwelling or rising of water

define geostrophic flow

flow in which the pressure gradient force and coriolis force are in balance

where are currents stronger

stronger on the western side than the eastern side

what causes western boundary intensification

variation of the strength of the coriolis effect with latitude