Vietnam Lecture3 CO2

8/14/2019 Vietnam Lecture3 CO2

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Jacek PiskozubInstitute of Oceanology PAS

Sopot, Poland

Ho Chi Minh City, December 2007

Lecture 3:

Ocean as the sink and source of climatically important gases(carbon cycle, CO2, methane, DMS)


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Jacek PiskozubHi Chi Minh City lectures, December 2007

Ecosystem approach to valuation of marine coasts: examples from Baltic

Sea Marine aerosol source function: approaching the consensus

Ocean as the sink and source of climatically important gases

Air sea interaction in the global scale: from multidecadal variability toArctic Oscillation

Climate change threats, Part I: Changes in the climate of the tropic

Climate change threats, Part II: Arctic climate and global sea level


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How do the greenhouse gases work?

A simple application of fundamental laws of physics and geometry results in an

Earth which is on average 33 K cooler if there were no greenhouse gases,namely H2O, CO2, CH4.


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Efekt cieplarniany

Proste uycie podstawowych praw fizyki i geometrii pozwala wyliczy, e Ziemiabyaby 33 stopnie zimniejsza gdyby nie gazy cieplarniane H2O, CO2, CH4.


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Greenhouse effect: co absorption in infrared

Greenhouse gases absorbinfrared (IR) radiation making itmore difficult for Earth to cooldown by radiating heat into the

outer space. Because differentgases have different absorptionbands, together they are able toabsorb in almost all the IRwavelength range. The visible(VIS) range is actually one of the

few windows of transparency forelectromagnetic waves.

oceanworld.tamu.edu


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IPCC report: what we knew in 2007

Dod

IPCC, Climate Change 2007: The Physial Science Basis


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Atmospheric O2 & CO2 history: a wider view

Atmospheric O2 & CO2 concentration in the Phanerozoic (N.Lane Oxygen 2005 after Berner & Canfield 1989, Berner 1994)

Method:Our best guess of

atmospheric O2 (upperpanel) and CO2 (lowerpanel) concentrationfrom sedimentary C13,and long-term carbon

cycle modelling(volcanism, subductionmetabolism, erosionetc.)

Conclusion:CO2 concentrationdecreases gradually inthe geological timescale but with a lot of

oscillations.


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Atmospheric CO2 increase since 1958

Atmospheric CO2 concentration measured on Mauna Loa (Hawaii) 1958-2005

(Keeling & Whorf, http://cdiac.esd.ornl.gov/trends/co2/sio-mlo.htm)

Charles D. Keeling 1928-2005


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Latest five years of the CO2 trend

The increasing trend in atmospheric CO2 does not change. Since the MaunaLoa measurements were started in 1958, every year brings more atmosphericcarbon dioxide.

NOAA, http://www.esrl.noaa.gov/gmd/ccgg/trends/


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How much of the carbon stays in atmosphere?

Houghton 2007 (Annu. Rev. Earth Planet.)

We produce yearly 6 PgC (recently even more!) by burning fossil fuels (coal,oil and natural gas) and possibly 2 PgC more by clearing forests. Roughlyone half stays in the atmosphere. What happens with the rest?

1Pg = 1 Gt = 1 Tkg = 1012 kg

H h k h h f CO i k i h ?


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How to check how much of a CO2 sinks in the ocean?

Keeling, Piper & Heimann 1996 (Nature.)

Changes in the atmospheric O2/N2 ratio make it possible to differentiate landand sea of CO2. It is assumed that the land biosphere gives back 1.1 mole ofO2 for each absorbed CO2 mole, while the ocean does not return any oxygen.

Wh t h t th f il f l b ?


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What happens to the fossil fuel carbon?


Only part of the CO2 we produce stays in the atmosphere. The rest is

absorbed by the ocean or land vegetation (here named: Unidentified sink).


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Quay 2002 (Science)

H h i t th ?


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How much goes into the ocean?


Ocean absorbs about 25% of the CO2 we produce. The terrestrial (land)

vegetation absorbs on aveage a similar amount (the maximum around 1990may be connected to Pinatubo volcano).

Ile do oceanu a ile pochania ycie na ldzie?


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Ile do oceanu a ile pochania ycie na ldzie?

Bousquet et al. 2000 (Science)

Left: variability of CO2 flux on land (A) is greater than for the ocean (B).Right: carbon balance for the tropical Pacific (A) and tropical land (B).

Arrows are the El Nio events (bold ones mean strong events).

Where on land?


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Where on land?

Bousquet et al. 2000 (Science)

Anomalies of CO2 fluxes from horizontal concentration gradients forNorthern Hemisphere, North America. and Eurasia (vertical axis: downfor sink, up for source).

Carbon cycle


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Carbon cycle

Deep ocean is the main reservoir of organic carbon (if one does not count thesediments in Earth crust). Therefore the ocean controls atmospheric CO2concentrations in the time scale of hundreds and thousands of years (for

longer time scales the controlling factor is geology).Sigman & Boyle 2000 (Nature)

Carbon cycle: reservoirs and fluxes in Pg


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Carbon cycle: reservoirs and fluxes in Pg.


What does the future bring?


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What does the future bring?

Land biosphere accepts less CO2 with increasing temperature (soilrespiration) therefore during El Nios, atmospheric CO2 increases fastereves as the ocean absorbs more carbon dioxide (no upwelling of CO2 richwater in the Eastern Pacific). This means that the land biosphere meybecome a net source of carbon in the greenhouse world.

Cox et al. 2000 (Nature)

Gas solubility in water


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Gas solubility in water

Solubility of any gas in water decreases with increasing temperature (the figureleft is oxygen solubility). Partial pressure of a gas in solution in a giventemperature is proportional to its concentration (Henry's law). The partialpressure of a gas in water changes with temperature proportional to exp(-1/T)(Van t'Hoff law).

The gas flux across sea surface if proportional to the difference of partial

pressures of the gas in water and air, multiplied by transfer velocity kand gassolubility .

Aero

What does the transfer velocity k depend on?


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What does the transfer velocity kdepend on?

Similarly as in the case of aerosol fluxes, there are many differentparameterizations of k, most of them basing on wind speed U (see the figureabove). W-92jest przykadem zalenoci od U2a Eq. 4 od U3 in fact both

were proposed by the same author (Wannikhof 1992 & 1999).Wannikhof & McGillis 1999 (Geophysical Res. Letters)

U2or U3?


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U or U?

Wannikhof i McGillis 1999 proposed to parameterize kfor CO2 with U3 instead

of U2. More recent studies tend to prefer the older parameterization (U2). Thefuture lies most probably with parameterizing it more directly with wave slopesmeasured by satellite radars (scatterometers) see Frew et al. 2004, 2007

Wannikhof & McGillis 1999 (Geophysical Res. Letters)

In-water CO2 partial pressure for August.


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p p g

Takahashi et al. 2003 (Deep Sea Research)

CO2 flux across the sea surface depends on the difference of pCO2 between seawater and air. For in-water pCO2 < 380 atm the flux goes from air to sea. Its value isproportional to the difference and to squared wind speed.

CO2: average flux across the sea surface


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g


Global flux: +2.2 Pg C yr-1 (+22%, -19%) for a non-El Nio year. The balancewas made from 940.000 measurements of pCO2 partial pressure assumingthe

U

2parameterization (U

3gives flux values which are 70% greater).

Seasonal changes of in-water pCO2


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g p 2


Positive numbers mean the pCO2 is larger in the warm season (physicsdominates) while negative mean the maximum is in the cold season (biology

dominates).

How does it work?


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An example of seasonal changes ofCO

2partial pressure and concentration

in the Bermuda region:

a) changes in sea surface temperature(SST) and measured CO2 partialpressure.

b) average value of pCO2 corrected totemperatuure using van 't Hoffa law(representing only temperature relatedchanges) and pCO2 recalculated to aconstant (average) SST (representing

CO2 in-water concentration).

CO2 concentration seasonal variability


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y


Seasonal changes of pCO2 after correcting for temperature changes - whichmakes them proportional to actual in-water CO

2concentration changes.

Temperature induced pCO2 seasonal changes


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p g


Seasonal changes of in-water carbon dioxide partial pressure aftersubtracting biology related changes leaving only the temperature relatedeffect.

Biology pump and physically forced fluxes


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gy p p p y y

Chisholm 2000 (Nature)

Summary 1/3


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Summary 1/3

Atmospheric concentration of the mainatmospheric greenhouse gas (except for H2O)

increases every year due to over 6 Gt (Pg)carbon emission from the fossil fuel we burn,from concrete production (and possibly up to2 Gt from forest clearing).

Ocean absorbs about 2 Gt C, land vegetationanother 1 Gt C. The other > 3 Gt C stay in theatmosphere, increasing CO2 concentrationyearly by over 1.5 ppm (atm)

Since the preindustrial era, we increased

atmospheric CO2 from ~ 280 to over 380 ppm.

Instrument setup for direct

measurements of CO2fluxeswith eddy

correlationmethods thefuture of gas flux ocean

measurements.

Interannual variability of CO2 sink is greater for the continents thanfor the oceans. Over the ENSO cycle the variability in land and seahave inverse signs.

CO2 : will we acidify the ocean?


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CO2 : will we acidify the ocean?

K. Caldeira & M.E. Wickett, 2003, Nature 425, 325-325

a) Forecasted emission and concentration of CO2

and ocean pHb) Comparison of change rate in ocean pH in last glacial period

(A), latest 300 M years (B), in historical times (C) andforetasted for this century (D).

CO2 i CH4 how do they influence the climate?


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2 4

Atmospheric concentration of methane is about 220 smaller that of carbondioxide. However it's much greater greenhouse effect means that methane isresponsible for about 20% of anthropogenic greenhouse effect.

NCR report 2006

Methane increase seems to slow down


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As opposed to CO2atmospheric concentration,methane increase seems to

slow down in recent years (thefigure shows concentrationmeasurement series andcalculated yearly increase).Studies of geographicalgradients seem to suggest thatthe slow down in methaneemission increase happensmostly in the NorthernHemisphere.

NOAA, updated with Dlugokencky et al. 2003 (Geophysical Res. Letters)

Methane balance what we knew in early 2006


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Methane fluxes are given in millions of tons per year.Lowe 2006 (Nature)

Methane geography


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Because most of the methane sources are located in the NorthernHemisphere, and its atmospheric lifetime is short (a few years) theconcentration over Northern Hemisphere is always greater than over the

Southern one. The seasonal changes are anti-correlated (obviously). NOAA

Methane geography: a model


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In methane emission (and inits troposphericconcentration) the terrestrialsources are clearlydominating.

In the stratosphere, methanelingers mostly in the tropics.

The figure is a model result.

NOAA

Methane geography: observations


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Methane concentration from SCIAMACHY sensor of the ENVISAT satellite.The surprising fact is the very high concentration over tropical jungles. Recentlaboratory studies (Keppler et al. 2006) confirm that deciduous (leafy) forests

are a methane source (globally 63-243 M t / year !) . Frankenberg et al. 2005 (Science)


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Concentration of climate influencing gases1978 2006


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1978-2006

NOAA

Anthropogenic radiation forcing 1979-2005


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NOAA

Summary 2/3


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Summary 2/3

The next most important greenhousegas is methane. Only about 10% isemitted from the ocean. Most isemitted from the land, especially in theNorthern Hemisphere.

Its atmospheric concentration seemsto stabilize in recent years.

The third most important greenhousegas is nitrous oxide (N2O), producedmainly by agriculture and to a lesser

degree by combustion engines.

CO2 is not the whole story: : atmospheric

concentrations of three other greenhouse

gases (Shine & Sturges 2007)

Climate importance of freons (mainly CFC-12 and CFC-11) ishopefully decreasing as they are not produced anymore.

Freons and nitrous oxide have also a destructive influence on theozone hole.

DMS and climate: the CLAW hypothesis


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CLAW = Charlson, Lovelock, Andreae & Warren 1987 (Nature)

Since 1972 (Lovelock et al.), weknow that one of the main sourcesof atmospheric sulfur is dimethylsulfide (DMS) produced byphytoplankton Sulfur particles are

condensation nuclei of aerosol andcloud droplets, cooling down theplanet. In 1987 CLAW authorsproposed a feedback mechanismby which phytoplankton controls

the climate.

DMS feedback mechanism discovered?


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Bates, Charles & Gammon (1987)discovered a strong correlation betweendaily irradiance dose at the sea surfaceand DMS concentration which could bea confirmation of a crucial part of thepostulated feedback mechanism.

Bates, Charles, Gammon 1987 (Nature)

Shipping: as important as phytoplankton?


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The amount of sulfur emitted inengine exhaust by ocean goingships shows that in many

basins (especially in theNorthern Hemisphere) is largerthan DMS derived sulfur .Global cooling radiative forcing(by cloud cover increase)created by shipping is

estimated at -0.11 W/m2. Capaldo et al. 1999 (Nature)

We and the phytoplankton: who produces how much?


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Biogenic sources of sulfur (of which 90% is DMS) are responsible for 23% ofemitted sulfur and 42% of atmospheric sulfur content. Anthropogenic sourcesare 70% of emission and 37% sulfur content in the atmosphere. Volcanoesare responsible for respectively, 7% and 18%.

Sim 2001 (Trends in Ecology and Evolution)

Problems of the CLAW hypothesis


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The CLAW hypothesis doesnot make sense for theevolutionists: DMS producingspecies help also theircompetitors by cooling theplanet. The competitors by notusing energy for the effortwould be the actual winners.

DMS, and more correctly itsprecursor DMSP - of manybiological uses, among othersan antioxidant) (Sunda et al.2002) is releases by organism

mostly after their death.

Sim 2001 (Trends in Ecology and Evolution)

DMS itself is a product of decomposition of DMSP, mostly by bacteria,which do not gain evolutionarily by cooling the planet.

But still DMS strongly correlates with irradiance...


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DMS concentration in surface waters correlates very strongly with theirradiance dose (left: r2=0.94 for the Mediterranean Sea; right r2=0.95 for theWorld Ocean). It can be explained in part by its antioxidant activity in thecells. However such a high correlation compared to such indirect link throughthe food chain is intriguing. Maybe there is a grain of truth in the CLAW...

Vallina & Sim 2007 (Science)

Summary 3/3


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Over 40% of atmospheric sulfur, (coolingEarth by scattering the Solar radiation back tospace and by increasing cloud albedo andcoverage) is of biological origin, mostly fromdimethyl sulfide (DMS) of oceanic origin.

In the 1980s, a hypothesis of naturaltemperature regulation by DMS producing

phytoplankton has been proposed (CLAWhypothesis).

The hypothesis was criticized as evolutionarynaive (plankton altruism).

Phytoplankton while producing

DMSP, the DMS precursor ?(Fig. by. Mirka Ostrowska, IOPAN)

DMS is not even a direct plankton product but rather of bacteria

decomposition of its precursor (DMSP) released to the sea wateronly after the plankton cells are dead.

However, DMS concentration is so strongly correlated withirradiance that it cannot be fully explained even by thephotoprotective role of DMSP (an antioxidant).

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Vietnam Lecture3 CO2