1. Vertical profiles of elements come in a few flavors Increasing with depth Decreasing with depth Constant These correspond to the removal processes Biological removal Chemical removal Not much removal Summary: Lecture 2

2. The “biological pump” Photosynthesis Depletion of carbon and nutrients Production of oxygen Respiration Depletion of oxygen Regeneration of carbon and nutrients

3. Insights from 2-box model 1) physical supply = biological export (from blackboard) PsPs PdPd

4. Biological export equals Physical supply (or, What goes down must come up) Blood Sweat and Tears Jazz-Rock band 1967 – present Famous for “Spinning Wheel” Terrible The First Law of Chemical Oceanography

5. A Deep Ocean Clock: 14 C n + 14 N 14 C + p 14 C init 14 C  1/2 =5730 yrs Radioactive carbon created in the atmosphere enters the ocean as 14 CO 2. It decays with a half-life of 5730 years, providing a “clock” for the flow of seawater from the surface into the deep ocean. atmosphere ocean “Cosmic Rays” Ocean circulation can be timed with radioactive “tracers”.

6. Insights from 2-box model 2) Deep Ocean residence time (from blackboard) Radioactive Carbon Surface ~ 6% below standard Mean deep ocean ~ 10% below surface (plotted relative to an arbitrary standard)

7. Willard Libby UCLA Professor of Chemistry Inventor of radiocarbon dating Nobel prize in 1960 Married to Leona Woods (also famous scientist, also UCLA professor, developed first nuclear reactor) The Second Law of Chemical Oceanography The deep ocean is ~1000 years “old”.

8. Insights from 2-box model 3) Global Ocean Productivity The elemental composition of Marine plankton μmol/kg 0 5000 1000 depth 1234

9. Alfred Redfield Harvard Professor of Zoology Discovered close relationship between plankton biomass and ocean chemistry (a.k.a. “Redfield ratios”) Pipe smoker, bowtie wearer Result: Carbon is exported to deep ocean at ~5x10 15 g/yr Plankton are built of elements in nearly constant proportions. But what was Redfield made of? The Third Law of Chemical Oceanography

10. Human Stoichiometry “The Proportions of Man” Leonardo Da Vinci How and why are we similar to or different from phytoplankton? Human Proportions A chemical view Human Proportions A geometrical view

11. The “biological pump” Photosynthesis Depletion of carbon and nutrients Production of oxygen Respiration Depletion of oxygen Regeneration of carbon and nutrients

12. A problem with the 2-box ocean The elemental composition of Marine plankton (from blackboard) O 2 μmol/kg 0 4000 1000 depth 100 200300

13. Insights from 2-box model 3) Global Ocean Productivity The elemental composition of Marine plankton μmol/kg 0 5000 1000 depth 1234

14. Introducing Horizontal Variations To understand this, we need to study ocean circulation! Surface Phosphate, PO 4 (mmol/m 3 )

15. rivers sediments ff Reviving Rivers How many times will a P atom see the abyss? PsPs PdPd Insights from 2-box model 4) External inputs vs. Internal recycling