Ocean Production and CO2 uptake

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Ocean Production and CO2 uptake
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Announcements

• MT results Will be passed out in section, or
  wed in class for those with Monday sections.
• MT curve will be discussed in lecture on Wed.

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Recall from box models active carbon pools
ATM CO2
Dissolved CO2 in ocean
Not to scale..
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Fig. 6.6
Recall Current ocean is gaining Carbon..
OCEAN Reservoir size 38000 Flux in 90 Flux
out 880.288.2 90 - 88.2 1.8 Pg/yr OCEAN is
gaining 1.8 Pg/yr
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Sum of the Sources Sinks of Anthropogenic carbon
BIOTA SOILS Flux in 120 Flux out 46055
119 Net SINK 1 Pg/yr
OCEAN Flux in 90 Flux out 880.2 88.2 Net
SINK 1.8 Pg/yr
Human SOURCES 7.4 1.0 Pg/yr Measured
Atmospheric increase 4.0 Pg/yr CALCULTED Carbon
SINKS 3.4 1.0 Pg/yr Measured carbon
SINKS 2.8 Pg/yr Calculated and Measured SINKS
are equal within error
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Bottom line
A very large amount of carbon cycling through
the atmosphere goes into the ocean.. But how does
it do it?
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Outline

• Chemistry. How does ocean absorb CO2, and what
  happens?
• Biology what does it take for plankton to grow?
  
• 3. The two pumps for putting C in the deep
  ocean
• a) Abiotic (CO2)pump-
• b) Biological pump

Just Face it Brett. No one cares about the
Carbon Cycle. (overheard)
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1. Chemistry
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Focus on Atm and Ocean CO2 boxes
ATM CO2
Dissolved CO2
CO2 dissolved in ocean water Is gt 50 x all CO2
in atmosphere!
Why? Because chemistry of ocean water can hold so
much..
Not to scale..
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Questions 1) why can ocean hold so much CO2?
2) what does putting more CO2 into ocean do to
water chemistry?
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Question what is PH of water?
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What is the Ph of natural water?

• Natural water (rain included) is slightly acidic
  (Ph 5-6)
• CO2 H2O gt H2CO3 (carbonic acid)
• Aside Acid rain is much stronger acid, due to
  SO2 emissions from coal burning- but reaction is
  exactly the same! SO2 H2O gt
  H2SO4?(sulfuric acid)

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But then there is more chemistry

• 1) CO2 dissolves in sea water forming carbonic
  acid
• CO2 H2O gt H2CO3
• 2) Carbonic acids yields bicarbonate and hydrogen
  ions
• H2CO3 gt H HCO3-
• 3) Bicarbonate dissociates to another Hydrogen
  react and Carbonate ion
• HCO3- gtH CO32-

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Together this is called theCarbonate Buffer
system

• H2O CO2 H2CO3 H HCO3- 2 H CO3-2

• Note each carbon in CO2 that goes into the ocean
  as one thing, can turn into three separate forms
• Each form has its own chemical solubility
• Carbonate buffer system is central to maintaining
  the Oceans PH- AND regulating CO2 storage!

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Overall The Ocean is major Sink of CO2

• Because increasing levels of Atm CO2 have
  increased the air-sea gradients.

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Passive (chemical) absorption mechanism
CO2

• H2O CO2 H2CO3 H HCO3- 2 H CO3-2

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2. Biology
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Global Ocean Productivity
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Recall

• Life (biosphere) transforms and recycles carbon
  from inorganic to organic forms

Inorganic matter (oxidized carbon) CO2
Organic matter (reduced carbon) CHO
When ocean plankton grow- the surface ocean is
taking up carbon from the atmosphere!
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Photosynthesis
PLANKTON PHOTOSYNTHESIS
light
CO2 H2O
PO4 , NO3 , (Biolimiting salts nutrients)
CH2O O2
organic tissue oxygen
NOTE 1 Biolimiting SALTS are used UP, Oxygen
is PRODUCED
NOTE 2 can only happen in the SURFACE !
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Piece 2 PARTICLE SINKING to depth
FEEDING by ANIMALS-
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Piece 3 Respiration at depth
( Animals bacteria)
CH2O O2
organic tissue oxygen
NOTE 1 Oxygen is USED UP, Biolimiting SALTS
(and CO2) are PRODUCED
This PROCESS is called REMINERALIZATION -
because mineral nutrients Salts are replaced
into the deeper sea
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Result Nutrient Profiles

• Recall major nutrients are USED UP in surface by
  photosynthesis (eg Phosphate (PO4), Nitrate
  (NO3), Silicate)
• BUT replaced in deep ocean by remineralization
  of sinking particles!

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The Planktons Catch-22 Where are the nutrients?
Where is the Light?
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Recall StratificationOcean is layered by
density
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MIXED LAYER is upper layer of water totally
mixed up by the wind.. the deeper the mixed layer
is, more of those deep- nutrients can reach the
surface!
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Result

• MOST OF SURFACE OCEAN PRODUCTION IS
• NUTRIENT LIMITED

This means, that the main thing which controls
overall plankton production is AVAILABLE
NUTRIENTS in surface water (and therefore the
amount of CO2 that can be turned into plankton
biomass)
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Recall upwelling ?
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Coastal upwelling photo
Effect of Coastal UPWELLING
This explains why upwelling areas are so
intensely productive for fisheries- but also
entire food chains..
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At Most Mid-Latitude areas global upwelling
patterns production patterns
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Higher latitudes Highly productive during spring
and summer- (when enough light)
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Mid-Lower latitudes More Constant,Central areas
(no upwelling) are deserts
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Biological Ocean C-fixation Summary

• Plankton draw down atm. CO2, fix it into
  biomass
• This is called plankton production
• Plankton production is limited mostly by
  available nutrients

ATM CO2
? Available surface nutrients are main limit on
amount of CO2 that can be removed from Atm.
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3. The Oceans two pumps for CO2
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Question Why do you need a pump
where is the ocean pumping it to
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Recall those Ocean Layers
SURFACE OCEAN
THERMOCLINE
DEEP OCEAN
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• Surface mixed layer 100 meters deep (out of
  4500m!!) IS ONLY PART WHERE CO2 FROM ATM CAN
  PENETRATE by mixing..
• Same depth (100m) is where all the ocean
  production can happen!

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So Why do you need a pump
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The physical pump (passive CO2 uptake, no
biology involved)
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Sources/ sinks co2
Oceanic Sources and Sinks of Atmospheric Carbon
Dioxide
Oceanic concentration of CO2 depends on
temperature, salinity and biological productivity.
CO2 flux into/out of ocean depends on air-sea
CO2 difference.
CO2 from A to O
CO2 from O to A
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How do you get surface water down to the deep?
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Recalltotal turnover time of ocean 1000 years
Surface Ocean residence time 100 years
Deep Cold Ocean residence time 1000 years
Recall Residence time is the average amount of
time a substance (in this case water) spends in
a reservoir
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Recall Global Ocean Conveyor Belt circulation
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So, if ocean is taking up CO2 at surface, how
long would it take to fill up? (reach its
capacity)
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Relative reserv. sizes
Ultimately- way more C in fossil fuels vs. what
ocean can absorb..
The passive (physical) CO2 pump is effective-
but its slow.
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b) The biological pump (active pump, due to
biological production and remineralization)
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Biological uptake Much, Much faster than
1000yrs!
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• Recall the 2nd piece of basic C cycling
• 1) Autotrophs Fixation of C into organic
  matter
• 2) Heterotrophs oxidize C - returns to
  geosphere via breakdown of organic matter

Inorganic matter (oxidized carbon) CO2
Organic matter (reduced carbon) CHO
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Biological Pump
CO2
Plankton
SURFACE OCEAN
Sinking Organic matter (reduced carbon) CHO
Heterotrophic bacteria
CO2
DEEP OCEAN
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Ocean Biological Pump

• 1) Surface Plankton fix carbon
• 2) Wastes SINK
• 3) Deep bacteria remineralize OM

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POM Particulate Organic Matter Particle
Formation Mechanisms
Secondary Formation Formed from aggregation of
primary particles, colloids, or even DOM
Primary formation Arise directly from biological
or inorganic sources
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Particle Paths

• Primary POM living organisms and their
  particulate remains
• Aslo detrital minerals carried to the ocean by
  rivers or winds.
• Secondary POM biologically formed aggregates
  such as fecal pellets, colloids, and mucus blobs.
• Also products of spontaneous assembly of organic
  polymers and ions.

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SINKING POM
Collected via SEDIMENT TRAPS Expressed in Flux
(eg. mg/m2/day) Looks like 1) Fresh plankton
and/or 2) zooplankton fecal pellets
Bio-pump Responsible for most VERTICLE
transport OC / nutrients / inorganics
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Sediment traps
Simple pit traps
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Sediment traps
Cone and baffel time series traps
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The Biological Pump

• C removed on time scale of plankton bloom
  (weeks)
• How long does the C stay down there?
• Depends on how deep it can get..

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The Martin curve

• Attenuation of sinking Particles (plankton
  remains ) is approximately exponential with
  depth
• Most organic tissue is converted back into CO2 by
  500m
• Almost all (gt90) by 1000m

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So what controls the effectiveness of
Biological Pump ?

• 1) Amount of Plankton production
• Nutrients available (NO3, PO4, Fe, Si)
• 2) Ecosystem structure ( Plankton types)
• All plankton production is NOT equal.. (more on
  this later)

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Overall, the biological pump

• Is much faster than abiotic pump- can move Carbon
  into mid-ocean in matter of WEEKS.
• Is limited by nutrient availability in open sea
• Ultimately- still cannot mostly reach the true
  deep ocean-
• ? Might be a short term fix- ie, sequester
  carbon on hundred year time-scales (not full
  1000 yrs..)

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Overall, the biological pump

• ? If enough nutrients.. Then might be a short
  term fix- ie, sequester carbon on hundred year
  time-scales (not full 1000 yrs..)
• Long term still limited by oceans ability to
  absorb CO2

Basis for lots of Geo-engineering schemes.. How
to put more nutrients into the ocean?
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Relative reserv. sizes
Ultimately- cannot escape the relative reservoir
sizes..
The passive (physical) CO2 pump OR the
biological pump can only be effective fairly
short (geologically speaking..)time frames..
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Quiz Put TA name and section day/ time on piece
of paper then

• Draw a diagram of the biological pump in one
  sentence, describe how it moves Carbon from
  atmosphere to deep ocean
• 2. Draw the carbonate buffer system equation-
  and explain in one sentence how it tells us why
  the ocean hold so much dissolved CO2?