vertical profiles of elements come in a few flavors increasing with depth decreasing with depth...
TRANSCRIPT
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
The “biological pump”
Photosynthesis• Depletion of carbon and nutrients• Production of oxygen
Respiration• Depletion of oxygen• Regeneration of carbon and nutrients
Insights from 2-box model
1) physical supply = biological export(from blackboard)
Ps
Pd
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 Lawof Chemical Oceanography
A Deep Ocean Clock: 14C
n + 14N 14C + p
14Cinit
14C1/2=5730 yrs
Radioactive carbon created in the atmosphere enters the ocean as 14CO2.
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”.
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)
€
Δ14C =14C
14C std
−1 ⎛
⎝ ⎜
⎞
⎠ ⎟* 1000
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 Lawof Chemical Oceanography
The deep ocean is ~1000 years “old”.
Insights from 2-box model
3) Global Ocean Productivity
The elemental composition of Marine plankton
μmol/kg
0
5000
1000
dep
th
1 2 3 4
€
106CO2 +16 HNO3 +H 3PO4 + 78 H 2O
€
C106H175O42N16P +150O2
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 ~5x1015 g/yr
Plankton are built of elements in nearly constant proportions.
But what was Redfield made of?
The Third Lawof Chemical Oceanography
Human Stoichiometry
€
106 : H 375O132C 85.7N 6.4Ca1.5P1
103 :S206Na183K177Cl127Mg40Si38.6Fe2.7Zn 2.1
100 :Cu 76I14Mn13F13Cr7Se4Mo3Co1
“The Proportions of Man”Leonardo Da Vinci
How and why are we similar to or different from phytoplankton?
Human ProportionsA chemical view
Human ProportionsA geometrical view
The “biological pump”
Photosynthesis• Depletion of carbon and nutrients• Production of oxygen
Respiration• Depletion of oxygen• Regeneration of carbon and nutrients
A problem with the 2-box ocean
The elemental composition of Marine plankton
(from blackboard)
O2μmol/kg
0
4000
1000
dep
th
100 200 300
Insights from 2-box model
3) Global Ocean Productivity
The elemental composition of Marine plankton
μmol/kg
0
5000
1000
dep
th
1 2 3 4
€
106CO2 +16 HNO3 +H 3PO4 + 78 H 2O
€
C106H175O42N16P +150O2
Introducing Horizontal Variations
To understand this, we need to study ocean circulation!
Surface Phosphate, PO4 (mmol/m3)
rivers
sedimentsf
Reviving Rivers
How many times will a P atom see the abyss?
Ps
Pd
Insights from 2-box model
4) External inputs vs. Internal recycling