Ciclo global del carbono

+65 -125

1.7 Land use change

+18

21.9 20

1.9 Land sink

1.6

+100

5.4

-220

+161

y su perturbación antropogénica

DEFINITION: within a given reservoir (ocean, land or atmosphere), the excess is the increase in carbon compared to it’s the stock during preindustrial times. WHERE IS IT: everywhere, land, ocean and atmosphere

WHERE can you MEASURE IT: atmosphere, and ocean (can be inferred), land is too heterogeneous.

DISTRIBUTION:

Anthropogenic CO2 Budget 1800 to 1994CO2 Sources [Pg C]

(1) Emissions from fossil fuel and cement productiona 244

(2) Net emissions from changes in land-useb 110

(3) Total anthropogenic emissions = (1) + (2) 354

Partitioning among reservoirs [Pg C]

(4) Storage in the atmospherec 159

(5) Storage in the oceand 112

(6) Terrestrial sinks = [(1)+(2)]-[(4)+(5)] 83

a: From Marland and Boden [1997] (updated 2002)b: From Houghton [1997]c: Calculated from change in atmospheric pCO2 (1800: 284ppm; 1994: 359 ppm)d: Based on estimates of Sabine et al. [1999], Sabine et al. [2002] and Lee et al. (submitted)

The ocean uptake a great part of CANT and they storage it. Thanks to them global warming is mitigatedUptake: across the air-sea interfaceStorage: accumulation in the water columnTransport: contrary to trees, oceans move!!, CANT is redistributed within the oceans

- once in the ocean the CO2 uptaken does not affect the radiactive balance of the Earth

- to predict the magnitude of climate change in the future

- within the carbon market (Kyoto) is important to know where is stored, important for policy makers

- we need to know the magnitude of the sinks and sources, and their variability and factors controlling them

- predict the future behavior of the ocean as a sink of CANT within a given emission scenario

- to control the effectiveness of the mitigation and control mechanisms as emission policies and sequestering mechanisms

Method Carbon Uptake Reference (Pg C yr-1)

Measurements of sea-air 2.1 ± 0.5 Takahashi et al. [2002] pCO2 Diff erence I nversion of atmospheric 1.8 ± 1.0 Gurney et al. [2002] CO2 observations I nversions of ocean transport models and observed DI C 2.0 ± 0.4 Gloor et al. [2003] Model simulations evaluated with CFC’s and pre-bomb C-14 2.2 ± 0.4 Matsumoto et al. [2004] OCMI P-2 Model simulations 2.38 ± 0.28 Orr et a.l [2004] Based on measured atm. O2 and CO2 inventories corrected f or ocean warming and strat. 2.2 ± 0.5

Keeling & Manning [submitted]

GCM Model of Ocean Carbon 1.93 Wetzel et al. (2005) CFC ages 2.0 ± 0.4 McNeil et al. (2003) Fluxes are normalized to 1990-1999 (except Keeling & Manning which is f or 1993-2004) and corrected f or pre-industrial degassing flux of ~0.6 Pg C yr–1.

Globally integrated flux: 2.2 PgC yr-1

Preindustrial Flux

Anthropogenic Flux

WOCE/JGOFS/OACES Global COWOCE/JGOFS/OACES Global CO22 Survey 1991-1997 Survey 1991-1997

OBJECTIVES:

+ quantify the CO2 storage in the oceans

+ provide a global description of the CO2 variables distribution in the ocean to help the development of global carbon cycle models

+ characterize the transport of heat, salt and carbon in the ocean and the air-sea CO2 exchange.

+ CANT is estimated or inferred, not measured

+ there are several methods, the most popular is Gruber et al. (1996), back-calculation technique (more during S1).

+ the CANT signal over TIC is very low 60/2100 = 3%

GSS’96 defined the semiconservative parameter C*(), it depends on the anthropogenic input, thus, the water mass age (), and its include the air-sea desequilibrium constant with time:

C*() = CANT + CTdis

To separate the anthropogenic CO2 signal from the natural variability in

DIC. This requires the removal of

i) the change in DIC that incurred since the water left the surface

ocean due to remineralization of organic matter and dissolution of

CaCO3 (DICbio), and

ii) a concentration, DICsfc-pi , that reflects the DIC content a water parcel

had at the outcrop in pre-industrial times, the equilibrium

concentration plus any disequilibrium

Thus,Cant = DIC - DICbio - DICsfc-pi = DIC – DICbio – DIC280 - DICdis

Assumptions:•natural carbon cycle has remained in steady-state

44.5 5 Pg

44.8 6 Pg 20.3 3 Pg

Indian Ocean

Pacific Ocean Atlantic Ocean

(Sabine et al, Science 2004)

Inventory of CInventory of CANTANT for year 1994 = 110 ± 13 Pg C for year 1994 = 110 ± 13 Pg C

15% area

25% inventorio

SO, south of 50ºS 9% inventory, equal area as NA

Kuhlbrodt et al, 2006

Atlantica

Inventory[Pg C]

Pacificb

Inventory[Pg C]

Indianc

Inventory[Pg C]

GlobalInventory

[Pg C]

Southern hemisphere 19 28 17 62

Northern hemisphere 28 17 3 48

Global 47 (42%) 45 (40%) 20 (18%) 112

a) Lee et al. (submitted)b) Sabine et al. (2002)c) Sabine et al. (1999)

Kuhlbrodt et al, 2006

¿How is CAN T uptaken ?

+ areas of cooling.

+ areas where old waters get to the surface

¿ Where is CANT stored ?

where surface waters sink to intermediate and deep --- deep waters formation areas.

F air-sea = – (Storage + TS + TN) + other terms

- F air-sea is the air-sea CO2 flux in the region (positive into the region),

- TS and TN respectively refer to the net transport of carbon across the southern and northern boundaries of the area (positive into the region).

- The storage term (always negative) stands for the accumulation of anthropogenic CO2,

- Other terms: river discharge, biological activity, etc...

4x 24.5ºNBering St.

F air-sea = – (Storage + TS + TN)

F air-sea = no se puede medir

Storage = se puede estimar, dos maneras

Transportes = se pueden calcular

Farewell

Vigo

0

HPT,S,Prop dzdxPropρvT

TProp is the property transport from Vigo to Cape Farewell over the entire water column

Prop the property concentration

v velocity orthogonal to the section, ESENCIAL

S,T,P in-situ density

Storage can be mathematically defined as:

dt

dzCdStorage

ANTz

where t is time and CANTz dz is the water column inventory of CANT.

The Mean Penetration Depth (MPD) of CANT using the formula by Broecker et al. (1979) is:

ml ANT

z ANT

C

dzCMPD

where CANTz and CANTml are the CANT concentrations at any depth (z) and at the mixed layer (ml),

ml ANT z ANT C · MPDdzC

dtdC · MPDC ·

dtdMPD

dt

dzCdml ANT

ml ANT z ANT

dtdC · MPD

dt

dzCdStorage ml ANT z ANT

Assuming that CANT is a conservative tracer (not affected by biology) that has reached its

“transient steady state” (profile with a

constant shape)

dtdC · MPD

dt

dzCdStorage ml ANT z ANT

Calculated from:

- the temporal change of CANT in the mixed layer.

- the MPD can be derived from current TIC observations

approximated assuming a fully CO2 equilibrated mixed layer keeping pace with the CO2 atmospheric increase.

Northward Latitude

253035404550556065

CA

NT

MPD

(m)

0

500

1000

1500

2000

2500

4x data

OacesNAtl-93 data

WOCE A20

Table 5.2. Mean Penetration Depth (MPD in meters, according to equation 5.9) of anthropogenic carbon

(CANT, meanstandard deviation), CANT increasing rates (mol·m-2·y-1), areas and final CANT storage rates by

latitude band and basin. The storage rates for the Arctic ocean (*) and the GIN (Greenland-Iceland-

Norwegian) seas (+) are also shown. The final storage rates for the Arctic-Subpolar (north of the 4x section)

and Temperate (between the 4x and the 24.5ºN sections) regions are shown at the bottom.

Latitude Band Basin MPD (m) CANT

Increasing rate (mol·m-2·y-1)

Area (1012 m2)

Storage rate

(kmol·s-1) East 1070137 0.930.12 2.4 729

24.5º-30N West 1466166 1.280.14 2.4 9911

East 1277168 1.110.15 1.4 497 30º-35ºN

West 1871240 1.630.21 2.1 10914

East 1473187 1.280.16 1.2 506 35º-40ºN

West 2029262 1.770.23 2.3 12817

East 1410168 1.230.15 1.0 405 40º-45ºN

West 2104166 1.830.14 1.9 1109

East 1520168 1.320.15 0.8 354 45º-50ºN

West 1921152 1.670.13 1.6 827

East 1462321 1.270.28 1.3 5312 50º-55ºN

West 1921152 1.670.13 1.3 706

East 1302432 1.130.38 1.2 4214 55º-60ºN

West 1739381 1.510.33 1.0 4811

67.4+

68.7* Arctic-Subpolar

15250

28850 Final Storage rate (kmol·s-1)

Temperate 835100

4x 24.5ºNBering St.172111 321258

-28850 -835100

116104 630200

CANT kmol/s

Álvarez et al. (2003).

Stoll et al. (1996).

Rosón et al. (2003).

McDonald et al (2003)

Holfort et al. (1998).

Ocean Inversion method• The ocean is divided into n regions

The inversion finds the combination of air-sea fluxes from a discrete number of ocean regions that optimally fit the observations:

• Cj = Carbon signal due to gas exchange calculated from observations at site j

• s i = Magnitude of the flux from region i

• H i,j = The modeled response of a unit flux from region i at station j, called the basis functions

• E = Error associated with the method

nregi

ijij EsHC,1

,

Mikaloff Fletcher et al. (GBC, 2006)

Mikaloff Fletcher et al. (GBC, 2006)

Mikaloff Fletcher et al. (GBC, 2006)

Figure 4. Global map of the time integrated (1765–1995) transport (shown above or below arrows) of anthropogenic CO2 based on the inverse flux estimates (italics) and their implied storage (bold) in Pg C. Shown are the weighted mean estimates and their weighted standard deviation.

Figure 5. Uptake, storage, and transport of anthropogenic CO2 in the Atlantic Ocean (Pg C yr−1) based on (a) this study (weighted mean and standard deviation scaled to 1995), (b) the estimates of [Álvarez et al., 2003], where the transport across 24°N was taken from Rosón et al. [2003], (c) Wallace [2001], where the transport across 20°S was taken from Holfort et al. [1998], and (d) Macdonald et al. [2003], where the transports across 10°S and 30°S were taken from Holfort et al. [1998], and the transport across 78°N was taken from Lundberg and Haugan [1996].

- Difficult to compare: OGCMs=>mean values, data=> no seasonal or temporal integration

- agreements and discrepancies

- OGCMs trp at 76ºN not robust, but Trp at more southern latitudes are quite robust and in agreement with data.

Air-Sea CANT uptake:

• total uptake 2.20.25 PgC/yr referred to 1995

• greatest uptake in SO, 23% of the total flux, but high variability from models

• considerable uptake in the tropics

• reduced uptake at mid latitudes, but here is the greatest storage

• high uptake in regions where low CANT waters get to surface

CANT transport:

• calculated from divergence of the fluxes

• SO: large uptake with low storage, drives a high northward flux towards the equator, half the uptake is stored, rest transported

• SO: transport with SAMW and AAIW, 50% total transport from SO goes into Atlantic oc., stored in subtropics

• high storage at midlatitudes in SH due to transport from SO not from air-sea uptake

• NA: high uptake in mid and high latitudes, divergence in transports, high storage (NADW formation)

• By taking up about a third of the total emissions, the ocean has been the largest sink for anthropogenic CO2 during the anthropocene.

• The Southern Ocean south of 36°S constitutes one of the most important sink regions, but much of this anthropogenic CO2 is not

stored there, but transported northward with Sub- Antarctic Mode Water.

• Models show a similar pattern, but they differ widely in the magnitude of their Southern Ocean uptake. This has large implications for the future uptake of anthropogenic CO2 and thus for the evolution of

climate.