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GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) Christoph Heinze University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research Prof. in Global Carbon Cycle Modelling Allegaten 70, N-5007 Bergen, Norway Phone: +47 55 58 98 44 Fax: +47 55 58 98 83

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GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012)

ChristophHeinze

University of Bergen, Geophysical Institute and

Bjerknes Centre for Climate Research

Prof. in Global Carbon Cycle Modelling

Allegaten 70, N-5007 Bergen, Norway

Phone: +47 55 58 98 44 Fax: +47 55 58 98 83

Mobile phone: +47 975 57 119

Email: [email protected]

DEAR STUDENT AND COLLEAGUE:

”This presentation is for teaching/learning purposes only. Do not useany material ofthispresentation for any purpose outsidecourse GEOF236, ”Chemical Oceanography”, autumn 2012, Universityof Bergen. Thankyou for yourattention.”


Sarmiento&Gruber 2006 Chapter 2:

Tracer conservation and ocean transport, part 2


  • The tracer conservation equation expresses that changes of ocean water column tracer concentrations depend on the

  • 3-dimensional ocean velocity field

  • Biogeochemical sources and sinks

  • The 3-d velocity field includes a multitude of processes. In general, a quantification of the velocity field is based on a balance of forces and resulting momentum induced on water “parcels”. Advection – convection – mixing – turbulence – wave motion.

  • The velocity field includes:

  • Friction forces (windstress, internal friction, bottom and side wall friction)

  • Pressure gradient forces

  • Coriolis force (rotating coordinate frame)

  • Gravity force, buoyancy force

  • Forcings, drivers:

  • Wind, evaporation-precipitation, sea ice melt / freezing cooling-warming, tidal force, sea level pressure exerted by atmosphere

  • Equations/models:

  • Navier Stokes equations of motion, these are nonlinear and extremely complex

  • Solutions are provided numerically in ocean general circulation models OGCMs


The wind driven circulation – qualitative findings: ocean water column tracer concentrations depend on the

Gyres

Upwelling/downwelling regions


Surface winds, January: ocean water column tracer concentrations depend on the

COADS data set

Sarmiento & Gruber (2006)


Surface winds, July: ocean water column tracer concentrations depend on the

COADS data set

Sarmiento & Gruber (2006)


Surface winds, schematic pattern of latitudinal variation: ocean water column tracer concentrations depend on the

Original source: Book of Pond & Pickard, 1983.

Sarmiento & Gruber (2006)


Streamlines (isolines of equal velocity) in the upper 50 m of the ocean, “surface currents”:

ECCO project, Stammer et al. 2002, dark shades correspond to high velocity

Sarmiento & Gruber (2006)


Sea surface height (top) and thermocline currents (0-500m)(bottom):

ECCO project, Stammer et al. 2002

Sarmiento & Gruber (2006)


Coastal up and downwelling, southern hemisphere case: (0-500m)(bottom):

Where would you find a typical coastal upwelling in the northern hemisphere?

Original: Thurman, 1990

Sarmiento & Gruber (2006)


Open ocean upwelling/downwelling at divergences/convergences:

Original: Thurman, 1990

Sarmiento & Gruber (2006)


Large-scale gyre structure of the ocean seen from top, left side shows schematic windstress pattern with latitude variations:

Note the westward intensification of ocean currents. Can you give examples for current systems in these west-side currents?

Original: Munk & Carrier, 1950

Sarmiento & Gruber (2006)


Sea surface phosphate (annual mean): left side shows schematic windstress pattern with latitude variations:

Original: World Ocean Atlas 2001, Conkright et al 2002


Sea surface nitrate (annual mean): left side shows schematic windstress pattern with latitude variations:

Original: World Ocean Atlas 2001, Conkright et al 2002


SOME THOUGHTS ABOUT THE MAJOR CATEGORIES OF OCEAN CORCULATION:

Wind driven circulation

Thermohaline circulation – does it exist as such?

(think also about continuity equation, conservation of volume)

Meridional overturning circulation (MOC)


Sea surface temperatures (annual mean): CORCULATION:

Original: World Ocean Atlas 2001, Conkright et al 2002

Sarmiento & Gruber (2006)


Sea surface salinities (annual mean): CORCULATION:

Original: World Ocean Atlas 2001, Conkright et al 2002

Sarmiento & Gruber (2006)


T-S diagram: CORCULATION:The isolines indicate equal densities. What dominates density variations at high and low temperatures?

Sarmiento & Gruber (2006)


Definitions – thermocline and mixed layer depth: CORCULATION:

Original: Knauss, 1997, Pickard & Emery 1990

Sarmiento & Gruber (2006)


Potential temperature – global section: CORCULATION:

Why is the potential temperature shown and not the in situ temperature?

Original: WOCE data

Sarmiento & Gruber (2006)


Salinity – global section: CORCULATION:

Original: WOCE data

Sarmiento & Gruber (2006)


Source functions of “transient tracers”: CORCULATION:

Sarmiento & Gruber (2006)



Thermocline ventilation – formal ages through the “ CORCULATION:3H/3He tracer clock”:

Sarmiento & Gruber (2006)


Strong density variation across the Gulf stream (zonal section):

Original: WOCE data

Sarmiento & Gruber (2006)



Radiocarbon age – global meridional cross section: the full set of equations of motion:

COLOURED VERSION AVAILABLE?

Original: GLODAP compilation, Key et al., 2004

Sarmiento & Gruber (2006)


Radiocarbon age – map at 3500 m depth: the full set of equations of motion:

Original: GLODAP compilation, Key et al., 2004

Sarmiento & Gruber (2006)


Schematic figure of cluster of 8 water molecules the full set of equations of motion:

Fraction of molecule aggergates as compared to single H2O molecule

Sea water T

From Dietrich&Kalle, ”Allgemeine Meereskunde”, 1965


Sea water temperature the full set of equations of motion:

Density maximum

From Dietrich&Kalle, ”Allgemeine Meereskunde”, 1965

Freezing point

Salinity



What happens to the salt at formation of sea ice ? 1992

From Eide, L.I., and S. Martin, The formation of brine drainage features in young sea ice,

J. Glaciology, 14(79), 137-154, 1975


From Eide, L.I., and S. Martin, The formation of brine drainage features in young sea ice,

J. Glaciology, 14(79), 137-154, 1975


From Eide, L.I., and S. Martin, The formation of brine drainage features in young sea ice, J. Glaciology, 14(79), 137-154, 1975


How to simulate convective overturning or drainage features in young sea ice, J. Glaciology, 14(79), 137-154, 1975

deep water production in models?

Non-hydrostatic models (often impractical, require high resolution).

Convective adjustment:

If shallower layer A gets heavier than layer B.

Alternatives:

- Homogenisation

- Swap vertical position of layers


Schlitzer, drainage features in young sea ice, J. Glaciology, 14(79), 137-154, 1975 JPO (2007)


Schlitzer, drainage features in young sea ice, J. Glaciology, 14(79), 137-154, 1975 JPO (2007)


Model intercomparison for CFC drainage features in young sea ice, J. Glaciology, 14(79), 137-154, 1975

GOSAC report

Orr et al., 2002


Model intercomparison for radiocarbon drainage features in young sea ice, J. Glaciology, 14(79), 137-154, 1975

GOSAC report

Orr et al., 2002


Meridional global water transport stream function [Sv] from an ocean model (PA2 OGCM, GFDL Princeton):

Sarmiento & Gruber (2006)


Meridional Atlantic water transport stream function [Sv] from an ocean model (PA2 OGCM, GFDL Princeton):

Sarmiento & Gruber (2006)


Meridional Indo-Pacific water transport stream function [Sv] from an ocean model (PA2 OGCM, GFDL Princeton):

Sarmiento & Gruber (2006)


Schematic of the meridional overturning circulation: from an ocean model (PA2 OGCM, GFDL Princeton):

Original: Toggweiler & Samuals 1993

Sarmiento & Gruber (2006)


Schematic of the global ocean conveyor belt circulation: from an ocean model (PA2 OGCM, GFDL Princeton):

Original following: Broecker, 1991 and Gnanadesikan&Hallberg, 2002

Sarmiento & Gruber (2006)


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