atlantic water masses
DESCRIPTION
ATLANTIC WATER MASSES. NADW AABW AAIW Itay Halevy. OVERVIEW. Definition of water masses. Motivation. Classification of water masses. Atlantic water masses and their properties. WATER MASSES. Water mass mixing is a way of explaining T and S profiles in the ocean. - PowerPoint PPT PresentationTRANSCRIPT
ATLANTIC WATER MASSESATLANTIC WATER MASSES
NADW
AABW
AAIW
Itay Halevy
NADW
AABW
AAIW
Itay Halevy
OVERVIEWOVERVIEW
Definition of water masses. Motivation. Classification of water masses. Atlantic water masses and their
properties.
Definition of water masses. Motivation. Classification of water masses. Atlantic water masses and their
properties.
WATER MASSESWATER MASSES
Water mass mixing is a way of explaining T and S profiles in the ocean.
Any T-S profile displays properties that are a result of a mixture of discrete end member waters.
Assumption - T and S are conservative properties - i.e. there is no diffusive exchange with the surroundings and change in water properties is through mixing alone.
Water masses have a “core depth” where their typical characteristics are located.
Vertical mixing creates a range of depths, above and below the core, influenced by the water mass.
Water mass mixing is a way of explaining T and S profiles in the ocean.
Any T-S profile displays properties that are a result of a mixture of discrete end member waters.
Assumption - T and S are conservative properties - i.e. there is no diffusive exchange with the surroundings and change in water properties is through mixing alone.
Water masses have a “core depth” where their typical characteristics are located.
Vertical mixing creates a range of depths, above and below the core, influenced by the water mass.
WATER MASSES CONT.WATER MASSES CONT.
Low velocities:– Typically < 1 cm/sec– Up to as much as 15 cm/sec
Replenishment of
nutrients to surface.
Low velocities:– Typically < 1 cm/sec– Up to as much as 15 cm/sec
Replenishment of
nutrients to surface.
WATER MASSES CONT.WATER MASSES CONT.
Waters classified by their DEPTH their DENSITY their TEMPERATURE & SALINITY
Note: Density has higher dependence on T
than on S.
Waters classified by their DEPTH their DENSITY their TEMPERATURE & SALINITY
Note: Density has higher dependence on T
than on S.
SO WHY DO WE CARE?SO WHY DO WE CARE?
Differential solar influx
Pole-Equator temperature gradientDifferential evaporation and precipitation
Requires meridional heat and salinity transport
Facilitated by Atmosphere & Ocean
Circulation characteristics influence climate
Differential solar influx
Pole-Equator temperature gradientDifferential evaporation and precipitation
Requires meridional heat and salinity transport
Facilitated by Atmosphere & Ocean
Circulation characteristics influence climate
WHY THE ATLANTIC?WHY THE ATLANTIC?
Major role in T and S transport:
Other oceans form much less deep water. Pacific less saline due to lower SSTs. Pacific also doesn’t reach as far north. Indian too warm.
North Atlantic is high-lat and saline enough.
Major role in T and S transport:
Other oceans form much less deep water. Pacific less saline due to lower SSTs. Pacific also doesn’t reach as far north. Indian too warm.
North Atlantic is high-lat and saline enough.
CLASSIFICATION OF WATER MASSES
CLASSIFICATION OF WATER MASSES
Divided into SURFACE, INTERMEDIATE, DEEP.
Surface water Warm and saline. Lower density - dependence of on T, S. Nutrient depletion - biotic productivity. Oxygen abundance - mixing.
Divided into SURFACE, INTERMEDIATE, DEEP.
Surface water Warm and saline. Lower density - dependence of on T, S. Nutrient depletion - biotic productivity. Oxygen abundance - mixing.
CLASSIFICATION OF WATER MASSES
CLASSIFICATION OF WATER MASSES
Intermediate water T & S vary greatly. Combination gives relatively high , typically
1027 to 1027.6 kg/m3.
Intermediate water T & S vary greatly. Combination gives relatively high , typically
1027 to 1027.6 kg/m3.
CLASSIFICATION OF WATER MASSES
CLASSIFICATION OF WATER MASSES
Antarctic Intermediate Water - AAIW T = 3°C S = 34.25 = 1027.30 kg/m3
Core depth ~ 1000 m Source region: Southern Pacific, Indian and
Atlantic Oceans near the Polar Front. Spreads as far as 20°N in all ocean basins.
Antarctic Intermediate Water - AAIW T = 3°C S = 34.25 = 1027.30 kg/m3
Core depth ~ 1000 m Source region: Southern Pacific, Indian and
Atlantic Oceans near the Polar Front. Spreads as far as 20°N in all ocean basins.
CLASSIFICATION OF WATER MASSES
CLASSIFICATION OF WATER MASSES
Deep water T = -1 to 3°C S = 34.5 to 35.0 = 1027.7 to 1028.0 kg/m3
Nutrient enrichment. Relative oxygen depletion.
Deep water T = -1 to 3°C S = 34.5 to 35.0 = 1027.7 to 1028.0 kg/m3
Nutrient enrichment. Relative oxygen depletion.
CLASSIFICATION OF WATER MASSES
CLASSIFICATION OF WATER MASSES
Antarctic Bottom Water (AABW) T = -1°C S = 34.65 = 1027.87 kg/m3
Core depth ~ 4000 m Source region: Wendell Sea, Ross Sea. Mean production rate: 20 Sv/yr
Antarctic Bottom Water (AABW) T = -1°C S = 34.65 = 1027.87 kg/m3
Core depth ~ 4000 m Source region: Wendell Sea, Ross Sea. Mean production rate: 20 Sv/yr
CLASSIFICATION OF WATER MASSES
CLASSIFICATION OF WATER MASSES
North Atlantic Deep Water (NADW) T = 3°C S = 34.93 = 1027.83 kg/m3
Core depth ~ 2500 m Source region: Imringer Sea, Nordic Sea,
Labrador Sea. Mean production rate: 15 Sv/yr
North Atlantic Deep Water (NADW) T = 3°C S = 34.93 = 1027.83 kg/m3
Core depth ~ 2500 m Source region: Imringer Sea, Nordic Sea,
Labrador Sea. Mean production rate: 15 Sv/yr
SUMMARYSUMMARY
Warm saline water cools and sinks in the Northern Atlantic Ocean (NADW).
Some of this water upwells near the ACC. Some then flows south is cooled further and
sinks to the ocean bottom (AABW). Some flows north and sinks beneath warm,
low latitude water (AAIW).
Warm saline water cools and sinks in the Northern Atlantic Ocean (NADW).
Some of this water upwells near the ACC. Some then flows south is cooled further and
sinks to the ocean bottom (AABW). Some flows north and sinks beneath warm,
low latitude water (AAIW).
REFERENCESREFERENCES
www.ocean.washington.edu/ courses/oc513/ www.iku.sintef.no faculty.washington.edu/pdquay/OC210/ www.ldeo.columbia.edu/dees/ ees/climate/lectures/o_atm.html www.ldeo.columbia.edu/edu/dees/ees/climate/slides www.deas.harvard.edu/climate/eli/Courses/2005fall_a/
www.ocean.washington.edu/ courses/oc513/ www.iku.sintef.no faculty.washington.edu/pdquay/OC210/ www.ldeo.columbia.edu/dees/ ees/climate/lectures/o_atm.html www.ldeo.columbia.edu/edu/dees/ees/climate/slides www.deas.harvard.edu/climate/eli/Courses/2005fall_a/
QUESTIONS ???QUESTIONS ???
THANKSTHANKS