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Visualizing the ocean’s chemistry

The underlying building blocks to an ecosystem. Visualizing the ocean’s chemistry. Chemistry (dissolved substances=salts)  density circulation  nutrients. Sources of nutrients to the surface mixed layer of the ocean. Chemical component of density in the mixed layer of the ocean.

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Visualizing the ocean’s chemistry

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  1. The underlying building blocks to an ecosystem Visualizing the ocean’s chemistry Chemistry (dissolved substances=salts)  density circulation nutrients

  2. Sources of nutrients to the surface mixed layer of the ocean Chemical component of density in the mixed layer of the ocean But first… what determines the density of ocean water?

  3. Surface salinity of the ocean

  4. Latitudinal cross section of salinity in the Atlantic Ocean

  5. Physical components that determine density:temperature and salinity

  6. Salinity affects density…. • Salt constituents are heavier than H2O • Temperature also affects density • Colder water is heavier • Saltier water is heavier • … Lets have a look at this… • …. So colder saltier water sinks and this affects……. To see how important it is …. circulation

  7. Wind drives the surface currents, but density drives the deep currents The Gulf stream delivers warm salty water to the North Atlantic…. Where Arctic winds chill them…. …. What happens to the density?

  8. The waters that sink in the N. Atlantic drive the global thermohaline circulation

  9. Lets come back to “salt”

  10. What is “dissolved” in the ocean anyway? • There are several different categories of solids dissolved in ocean water. • The 3 main constituents in sea water… • Conservative • Bio-intermediate • Bio-limiting (nutrients)

  11. The major constituents of seawater…. …are salt! The composition of these major salts in the ocean are invariant. Na+ 55% Cl- 30% Mg+2 4% SO4-27% Ca+ 1% Other 3% These are the conservative constituents of seawater

  12. The major constituents of seawater These are the elements that are measured in “salinity” Na+ Cl- Mg+2 SO4-2 The only way to affect their concentrations is via evaporation, precipitation , or sea ice formation. These are the conservative constituents of seawater

  13. The conservative constituents of seawater…. What about these lesser constituents of “salinity”? Na+ 55% Cl- 30% Mg+2 4% SO4-2 7% Ca+ 1% Other 3%

  14. What are nutrients anyway? • They are the non-conservative constituents in sea water… • Conservative • Bio-intermediate • Bio-limiting = nutrients

  15. Bio-intermediate constituents Elements: Ca= Calcium, about ½ % less abundant than in deep water C= carbon, 15% less than in deep water Sr= strontium, Cu= copper, Se= selenium, Ba= barium, about 70% less abundant than in deep water Ra= radium (probably not needed but incorporated by accident…) Compounds: Carbonate (carbon as carbonate) = CO3 Bio-intermediate components have variable distributions but rarely do their concentrations go to zero

  16. Biolimiting constituents (a.k.a. nutrients) Nitrate (NO3-) Does not limit growth of bluegreen algae (cyanobacteria) they fix nitrogen. Phosphate (HPO4=) the ultimate limiting nutrient for plant growth Silicate (H2SiO4) Limits the growth of diatoms Zinc (Zn++) Cadimum (Cd++) Iron (Fe++) Germanium (H4GeO4) These are almost totally depleted in surface water where most of the biology goes on: so much so their availability (or lack of it) controls growth.

  17. Vertical distributions of chemical constituents in seawater Libes, 1992 The terms conservative and non conservative reflect the extent to which the concentration of a constituent is affected by chemical or biological processes in seawater in relation to it’s overall concentration in seawater. .

  18. Sources of nutrients to the surface mixed layer of the ocean • What are nutrients to a chemist? • Where do they come from? • Preformed (recycled, delivered from elsewhere) • Biosynthesized • Nutrient distributions in the ocean and water column.

  19. Vertical distribution of nutrients Phosphate 10-6 mol/liter nitrate 10-6 mol/liter silicate 10-6 mol/liter Libes, 1992 Note the slightly different shapes –this has both to do with use and formation of the different nutrients

  20. The biological pump and nutrients The biological pump moves nutrients from the surface ocean to the deep water masses

  21. The balance between light and nutrients • … controls growth and is governed by the physics (light, mixing, stratification)

  22. Physical and chemical vertical profiles

  23. The biological pump and nutrients The biological pump moves nutrients from the surface ocean to the deep water masses: The chemists’ version These nutrients are returned to the surface mixed layer with winter mixing and upwelling

  24. The biological pump and nutrients The vertical distribution of nutrients from the is controlled by this delivery of nutrient from the surface ocean to the deep waters Nutrients and organic matter aren’t lost they are “remineralized”

  25. Vertical distributions relative to physical properties Vertical distributions of physical properties and nutrients in the ocean over the full depth of the ocean. They are very similar from place to place…. Libes, 1992

  26. Two perspectives on the bio-pump concept • The horizontal component (the circulation) • The time component = seasonality.

  27. Differences between the oceans in vertical profiles of nutrients a.k.a. horizontal differences in nutrient profiles…. The deep Pacific has more nutrients than the Atlantic Libes, 1992

  28. The “conveyor” belt circulation

  29. Water downwells: Low nutrients High O2 Control on global distribution of nutrients N,P N,P N,P N,P N,P Nutrients in deep water become enriched with increasing age N,P N,P N,P N,P N,P N,P Sediments have extensive remineralization N,P N,P N,P N,P N,P N,P

  30. The conveyor belt circulation

  31. Differences between the oceans in vertical profiles of nutrients The deep Pacific has more nutrients than the Atlantic because the waters there have accumulated more nutrients through time Libes, 1992

  32. Distribution of nutrients in the deep ocean Broecker and Peng, 1982

  33. Nutrients return to the surface... HOW???

  34. Coastal Upwelling zones in the world ocean Mann and Lazire These areas are the most productive because nutrients are readily available—but there is primary productivity everywhere in the surface ocean

  35. Annual Stratification sequence Recycling of nutrients at it’s peak…

  36. New versus regenerated production Lalli and Parsons Note: the biggest arrow is upwelled NO3 delivering “preformed nutrients”

  37. The biological pump and burial Some of the nutrients and organic matter are buried and “removed” from the system.

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