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Everything you wanted to knowEverything you wanted to know
but was too afraid to askabout “oceanoligists”
Alena MalyarenkoNABOS Summer School 2013
but was too afraid to askabout “oceanoligists”
Alena MalyarenkoNABOS Summer School 2013
OutlineOutline
Oceano.. wait for it.. logy ideas
Water masses
Definition
Classification
Formation
World WM
Arctic Ocean WM
My background special featuresMy background special features
Oceanology (we try to “study” rather than “observe”, or so they say)
Zubov, 1953: Department of Oceanology
We don’t use complicated math & physics (except for ready models)
Department specialization - water masses (you definitely need your imagination)
IMAGINE!IMAGINE!
Water Masses Water Masses
Classic DefinitionClassic DefinitionBodies of water that have a particular combination of properties that makes identifiable are referred to as WATER MASSES.
Defant (1929), analog of air masses in troposphere: “homogeneous limited or unlimited water object that can be characterized with certain physical and chemical properties”
Dobrovolskiy (1961): “some comparatively large water volume formed in a certain region of the World Ocean (the center, the source of the mass) that has over a long period of time almost constant and continuous distribution of physical, chemical and biological characteristics that form a unite complex and propagate as an integrated whole”
One more time!One more time!“some comparatively large water volume
formed in a certain region of the World Ocean (the center, the source of the mass)
that has over a long period of time almost constant and
continuous distribution of physical, chemical and biological characteristics
that form a unite complex
and propagate as an integrated whole”
Traditionally: 1929 - Defant, then Defant and Wust
“Wasswekorpers” - water bodies, homogeneous objects
Dynamic interaction between water bodies
First MentionFirst Mention
Real First MentionReal First MentionNansen, «THE NORWEGIAN SEA / ITS PHYSICAL OCEANOGRAPHY /BASED UPON THE NORWEGIAN RESEARCHES 1900-1904», 1909.
Introduction: By the two last expeditions the existence of the Wyville Thomson Ridge, was finally settled, and its configuration and physical conditions traced out. Thus it was finally proved that Europe (Scotland) is connected with Greenland by a continuous suboceanic ridge extending from Scotland to the Faeroe Bank (see fig. 8), from the Faeroes to Iceland, thence across Denmark Strait to Greenland. The saddle-depths of the ridge hardly exceed 550 metres (300 fathoms). By this ridge, the deeper parts of the Norwegian Sea Basin are entirely shut off from those of the Atlantic, and the cold bottom-water of the former is prevented from running
into the latter. The existence of this ridge is a feature of vital importance for the entire circulation of the Norwegian Sea. It forms a barrier to the movements of the water-masses, even those of the surface, as will be mentioned later; and its depths regulate the depths of the few currents coming in and running out from this basin.
Chapter V. General Description of the Water-Masses of the Norwegian Sea.
Genetic (convection, subduction, advection, subsurface mixing)
Structural (troposphere/intermediate/abyssal or surface/subsurface/intermediate/deep/bottom)
Geographical (center of formation)
Characteristic (high/low salinity/temperature)
Water Masses ClassificationWater Masses Classification
Antarctic Intermediate Low Salinity WM
WM Life Cycle (Genetic classification)
WM Life Cycle (Genetic classification)
3 basic phases:
1) formation,
2) transformation (evolution)
3)disappearance
3 basic phases:
1) formation,
2) transformation (evolution)
3)disappearance
FormationFormation
• 1) convective mixing - vertically unstable because of heat loss (autumn-winter cooling) or salinity increase (evaporation or ice formation)
5 types of thermohaline convection (Zubov, 1947):
1. polar (ice formation)
2. arctic (ice formation and winter cooling)
3. subarctic (winter cooling)
4. subtropic (winter cooling and evaporation)
5. tropical (evaporation)
Convection goes down until stratification is stable (100-4000 m) in several stages
low vertical gradient
modal water mass (McCartney and Talley, 1982)
Formation: SubductionFormation: Subduction
• 2) subduction (diving under) – sinkage cause by both wind and cooling
negative vorticity of wind field
Ekman pumping
slow sinkage of water
underlayers are more dense so sinking water has to move along isopycnic lines
SubductionSubduction1 winter:
•-convection goes down to a dense layer
•-creates a uniform layer
Summer heating:
•insulate water from atmosphere, creates stratification
2 winter:
•winter convection can’t reach this water
Subduction and obductionSubduction and obduction
SubductionSubduction
• Stommel, 1979
• formation of central WM in the main thermocline
• Wind convergence is typical for wide ocean areas with lost of T,S indexes (i.e., subtropical cycles).
• Sinking water has a wide variety of T,S indexes
surface
central
deep
bottom
intermediate
salinity
tem
pera
ture
Formation: mixingFormation: mixing
3) mixing of 2 or more WM under the surface
You get a new WM!
Formation: 4th type?Formation: 4th type?
Advection from the other place
Here: it’s not formed with any of 3 types!
BUT it was formed somewhere else
Transformation Transformation Start: 1) consolidation (Tomczak, 1999) – mixing inside the formed water volume
2) part mixing
If you know T1,S1 and T2,S2 you can calculate Tout and Sout (Mamaev, 1970)
TransformationTransformation• 3) modification and aging - changes non-conservative variables
because of biochemical processes ( decrease of O2, increase of nitrates and phosphates under the surface), decay (decrease 14C, tritium, 3He)
Aging of bottom Indian water
WM Age (Classic)WM Age (Classic)14C decay
O2 decrease
increase of nitrates and phosphates under the surface
GOC:GlobalOcean
Conveyer
WM Age (New)WM Age (New)Freons: unstable, biologically inactive, sea-atmosphere interaction (since 1975)
Sen Gupta, 2006
¼ degree model of freon distribution
1980
Net freon concentration <2km
2000
2020
2040
Transformation Transformation
4) different forming
intensive inter annual variability (heat and freshwater flux, bioproduction)
OUTSIDE OF FORMATION REGION, STAYING IN ONE POINT(YOU HAVE TO STOP MOVING WITH THE SAME WATER)
Elimination (disappearance) Elimination (disappearance)
1.WM is a part of creation of the new one, so that the new WM is “re-birthed”
2. WM is a part of mixing, you can’t identify it anymore, so it was “adsorbed”
WM Life circleWM Life circle
FormingTransformatio
nElimination
(disappearing)
Convection
Subduction
Mixing
Part-mixing
Aging (modification)
Different forming
Поглощение
Перерождение (Слияние)
Absorption
Re-birth(merging)
WM Formation WM Formation
Structural WMStructural WMtroposphere/intermediate/abyssal
or surface/subsurface/intermediate/deep/
bottom
troposphere/intermediate/abyssal or
surface/subsurface/intermediate/deep/bottom
Troposphere WMTroposphere WM
Surface (zonal)
Modal (subtropical modal waters, subpolar, modal high salinity waters)
Central
Very relative
z: max mixed layer
Latitude zoning:
•polar - subpolar: summer ice extension
•subpolar – mid latitudes : polar front
•mid latitudes - subtropical : subtropical front
•subtropical-tropical - change in wind direction in anticyclonic gyres
• tropical-equatorial - countercurrent between trade winds and
Surface WaterSurface Water
Surface WM (Lebedev, 1998)Surface WM (Lebedev, 1998)
• Minimum vertical gradient (T,S, density, O2) between seasonal and permanent thermocline
• Forming of modal WM is due to convection near permanent hydrological fronts from the side where density is less
• From subduction and advection from the center of forming modal WM spread on extensive territories
Modal WMModal WM
•Subtropical modal WM: on the sides of subtropical gyres
•Subpolar (subarctic, subantarctic): convection to the south from North Atlantic and North Pacific current and to the north from Antarctic Сircumpolar current
•High Salinity WM: subduction during higher evaporation from regions with salinity maximums inside subtropical gyres
3 types of modal WM
3 types of modal WM
Subpolar and Subtropical Modal WMSubpolar and Subtropical Modal WM
• Strait line on TS-diagram
• Subduction in subtropical gyres
Central Modal WMCentral Modal WM
Antarctic Intermediate WM
Antarctic Intermediate WM1/8 World Ocean volume
more that 50% of water area
low salinity + high biogenic elements
main freshwater flux from south polar front to the North
Formation: trans frontal change (the Pacific), convection (the Atlantic), advection (the Indian)
November 2004
World OceanWorld Ocean
Pacific Atlantic
North NorthSouth South
Т Т
S S
O2 O2
Pacific Atlantic
Silicate, mmole /kg
Phosphate, mmole/kg
NorthSouth NorthSouth
How much WM do we need?
How much WM do we need?
Mamaev, 1987: 23 WM
Emery, Meinke, 1986: 36 WM
Google: “Do you want more?”
Van Aken: “There is a real danger of transition from a very useful method of water mass analysis to a somewhat like a collection of post stamps”
Arctic OceanArctic Ocean
The Barents SeaThe Barents SeaAtlantic water , Arctic water (low S, T below 0, surface water), Coastal water (river run-off and Norway coastal current, low S and different T during the year)
Barents water (mixed all above: low T, high S)
Winter: no arctic water, North: Barents waters, South: Atlantic water
Summer (very stable, little amount of mixing):
North: Arctic on the surface, then Barents
Center: Atlantic water
South: Coastal, then Atlantic
The Cara SeaThe Cara SeaSurface Arctic water (up to 200 m, freezing T, 29-33,5‰)
3 layers:
upper layer is mixed during winter circulation (up to 50 m)
50-100 m: steep rise of S up to 34‰
100-200 m: intermediate characteristic between subsurface and deep waters
+ extra stratification in spring-summer because of heating and freshening
Warm Atlantic water in a trough (0 - +1°C, 35‰)
The Laptev SeaThe Laptev Sea
Surface Arctic water (5-7m)
Warm Atlantic water in a trough
Cold bottom waters (-0,4 - -0,9°C; 34,9‰)
The East-Siberian Sea
The East-Siberian Sea
Shallow
There’s no deep troughs
Low river run-off
Surface Arctic water, Coastal water (small areas near river mouths, less saline, warmer)
General PictureGeneral Picture
Nikiforov, Shpayher 1980
-1 to -1.8°C, 29‰
0 to +2°C, 33‰
-1 to -1.8°C, 29‰
-1.5 to 0°C, 34‰