ESS200A
Prof. Jin-Yi Yu
Characteristics of
the Gyres
qCurrents are in geostropic
balance
qEach gyre includes 4 current
components:
two boundary currents: western and eastern
two transverse currents: easteward and westward
Western
boundary current (jet stream of ocean)
the fast, deep, and narrow current moves warm water polarward (transport ~50 Sv or greater)
Eastern
boundary current
the slow, shallow, and broad current moves cold water equatorward (transport ~
10-15 Sv)
Trade
wind-driven current
the moderately shallow and broad westward current (transport ~ 30 Sv)
Westerly-driven
current
the wider and slower (than the trade wind-driven current) eastward current
(Figure from Oceanography by Tom Garrison)
Volume transport unit:
1 sv = 1 Sverdrup = 1 million m3/sec
(the Amazon river has a
transport of ~0.17 Sv)