Intermediate and deep ocean circulation Flashcards
Average depth of the ocean
3.5-3.8km
Low latitudes vs high latitudes
Net warmingin low latitudes and net cooling in high latitudes
Mid- latitiude waters
Warmer and more saline than interior waters
Weak thermocline
High intrinsic density= cooled waters sink
–> Common in high northern latitudes
Halocline
Vertical zone in water where there is a rapid change in salinity
Ocean surface waters mixing
Wind-driven waves and Ekman spiral cause mixing meaning T and S change little with depth
Flow in surface waters
Dominated by wind stress
Equatorial upper water- equatorial winds
Trade winds blow west in the tropics–> warm surface water piles up on W of ocean basins–. creates strong eastward currents –> Coriolis deflects moving water
Thermocline- equatorial regions
DEEP thermocline - WESTERN side
SHALLOW thermocline- EASTERN side
Central Open waters
While surface water sinks in subtropical gyre centers, Ekman transport driven by the gyre’s wind system piles up saltier water in mid-latitudes due to convergence.
Seasonal effects on mixing
In mid-latitudes, warming produces a warm and saline layer of surface water which is thickened and mixed but remains buoyant. In winter, water cools and sinks–> causes vigorous mixing
Central Ocean Water (COW) boundaries
COW= warmer and saltier therefore stays distinct from surrounding water masses down to 1,000 meters. Can be separated by underwater features like island chains. The Coriolis effect and wind patterns create separate bodies of COW in the N and S Hemispheres.
Western NACW
–> Forms by sinking and mixing of surface water in the Sargasso Sea gyre; salinity 35.5-36.5 PSU; temp 7-20C
–> SACW; 5-18C, 34.3-35.8 PSU
Arctic and Antarctic Upper Water
Direct wind drag causes convergence and piling up surface waters around polar front
Temperature contrast between surface and deep water
= small in high latitudes so the distinction between Surface, Upper and Intermediate
–> Arctic and Antarctic Upper Waters = surface occurrence of the corresponding Intermediate Waters
Intermediate water masses
Denser than Upper and Surface Water but less dense than Deep Water
–> Intermediate density due to reduced salinity or high temp
Antarctic Intermediate Water (AAIW)- formation
Dilution of cool deep water by icebergs just to the north of the south polar front
Features of AAIW
Low temperature 3-5C makes water contract ad sink but low salinity (34.3%) makes it float above dense saline water