Transcript CANT budgets in the ocean

Ciclo global del carbono
y su perturbación antropogénica
+161
1.9 Land sink
5.4
1.7 Land use
change
21.9 20
-220
+65 -125
+18
1.6
+100
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 1994
CO2 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
The ocean uptake a great part of CANT and they storage it. Thanks to
global sinks
warming
is mitigated
(6) them
Terrestrial
= [(1)+(2)]-[(4)+(5)]
83
Uptake: across the air-sea interface
Storage: accumulation in the water column
a: From
Marland andcontrary
Boden [1997]
Transport:
to(updated
trees,2002)
oceans move!!,
b: From Houghton [1997]
CANT is
redistributed
within
the 1994:
oceans
c: Calculated from change
in atmospheric
pCO2 (1800:
284ppm;
359 ppm)
d: Based on estimates of Sabine et al. [1999], Sabine et al. [2002] and Lee et al. (submitted)
- 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
(Pg C yr-1)
Reference
Measurements of sea-air
pCO2 Difference
2.1 ± 0.5
Takahashi et al. [2002]
Inversion of atmospheric
CO2 observations
1.8 ± 1.0
Gurney et al. [2002]
Inversions of ocean transport models
and observed DIC
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]
2.38 ± 0.28
Orr et a.l [2004]
OCMIP-2 Model simulations
Based on measured atm. O2 and CO2
inventories corrected for ocean warming
and strat.
GCM Model of Ocean Carbon
CFC ages
Keeling & Manning [submitted]
2.2 ± 0.5
1.93
Wetzel et al. (2005)
2.0 ± 0.4
McNeil et al. (2003)
Fluxes are normalized to 1990-1999 (except Keeling & Manning which is for 1993-2004)
and corrected for 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 CO2 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 DC*(t), it
depends on the anthropogenic input, thus, the water mass age
(t), and its include the air-sea desequilibrium constant with
time:
DC*(t) = CANT + DCTdis
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 (DDICbio), 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,
DCant = DIC - DDICbio - DICsfc-pi = DIC – DDICbio – DIC280 - DDICdis
Assumptions:
•natural carbon cycle has remained in steady-state
Kuhlbrodt et al, 2006
Inventory of CANT for year 1994 = 110 ± 13 Pg C
15% area
25% inventorio
Indian Ocean
SO, south of 50ºS 9% inventory,
equal area as NA
Pacific Ocean
20.3  3 Pg
44.5  5 Pg
Atlantic Ocean
44.8  6 Pg
(Sabine et al, Science 2004)
Atlantica
Inventory
[Pg C]
Pacificb
Inventory
[Pg C]
Indianc
Inventory
[Pg C]
Global
Inventory
[Pg C]
Southern hemisphere
19
28
17
62
Northern hemisphere
28
17
3
48
47 (42%)
45 (40%)
20 (18%)
112
Global
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...
F air-sea = – (Storage + TS + TN)
Bering St.
F air-sea = no se puede medir
Storage = se puede estimar, dos maneras
Transportes = se pueden calcular
4x
24.5ºN
Farewell 0
TProp 
  vρ
S, T, P
 Prop  dx  dz
Vigo  H
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
rS,T,P  in-situ density
Storage can be mathematically defined as:
Storage 

d C ANTz dz
dt
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:
C

MPD 
ANT z
dz
C ANT ml
Assuming that CANT is a
where
and· C
CANT
are the
CANT concentrations
at any
depthby
conservative
tracer (not
affected
 MPD
ANTml
ml
 CANT zCdzANTz
(z) and at the mixed layer (ml),
biology) that has reached its
d  C ANT z dz dMPD
dC ANT ml “transient steady state”

· C ANT ml  MPD ·
(profile with a
dt
dt
dt
constant shape)
Storage 

d C ANT z dz
dt
 MPD ·
dC ANT ml
dt
Storage 

d C ANT z dz
dt
 MPD ·
dC ANT ml
dt
Calculated from:
- the temporal change of CANT in the mixed layer.
approximated assuming a fully CO2 equilibrated
mixed layer keeping pace with the CO2
atmospheric increase.
- the MPD can be derived from current TIC observations
2500
4x data
WOCE A20
CANT MPD (m)
2000
1500
1000
OacesNAtl-93 data
500
0
65
60
55
50
45
40
Northward Latitude
35
30
25
Table 5.2. Mean Penetration Depth (MPD in meters, according to equation 5.9) of anthropogenic carbon
(CANT, meanstandard 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-IcelandNorwegian) 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
CANT
Area
Increasing rate
(1012 m2)
-2 -1
(mol·m ·y )
MPD (m)
East
1070137
0.930.12
2.4
729
West
1466166
1.280.14
2.4
9911
East
1277168
1.110.15
1.4
497
West
1871240
1.630.21
2.1
10914
East
1473187
1.280.16
1.2
506
West
2029262
1.770.23
2.3
12817
East
1410168
1.230.15
1.0
405
West
2104166
1.830.14
1.9
1109
East
1520168
1.320.15
0.8
354
West
1921152
1.670.13
1.6
827
East
1462321
1.270.28
1.3
5312
West
1921152
1.670.13
1.3
706
East
1302432
1.130.38
1.2
4214
West
1739381
1.510.33
1.0
4811
24.5º-30N
30º-35ºN
35º-40ºN
40º-45ºN
45º-50ºN
50º-55ºN
55º-60ºN
67.4+
Final Storage
rate (kmol·s-1)
Storage
rate
(kmol·s-1)
Basin
ArcticSubpolar
68.7*
28850
15250
Temperate
835100
CANT kmol/s
172±111
Bering St.
321±258
4x
24.5ºN
116 ±104
-288±50
630±200
-835±100
Stoll et al. (1996).
Álvarez et al. (2003).
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 
H
i , j si
E
i 1, nreg
• 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
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.
- 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.
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].
Air-Sea CANT uptake:
• total uptake 2.20.25 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.