air-sea co 2 exchange in the northern south china sea c.-m.tseng thanks to: w.c. chou; c.t.a. chen;...
TRANSCRIPT
Air-Sea CO2 Exchange
in the Northern South China Sea
C.-M.TsengThanks to:
W.C. Chou; C.T.A. Chen; C.C. Chen; S.W. Chung; K.T. Jiann; B.S. Lee; Y.H. Li; I.I. Lin;
K.K. Liu; D.D. Sheu; F.K. Shiah; G.T.F. Wong; L.S. Wen; Y. Yang……
Introduction & OverviewIntroduction & Overview Annual & inter-annual variability of Annual & inter-annual variability of
Ocean COOcean CO22
Physical and biogeochemical Physical and biogeochemical processes affecting variabilityprocesses affecting variability
Magnitude and variability of Air-sea Magnitude and variability of Air-sea exchange COexchange CO2 2 flux relative to global flux relative to global
scalesscales
Increasing magnitudes of TCOIncreasing magnitudes of TCO22 and and
ffCOCO22
Future studyFuture study (e.g., El-Niño, Typhoon)
Talk outline
1. Atmo. CO2,2. Temp.,3. Sea ice. 4. Sea level
key indicators of
global changeAtmo. CO2
Temp.
Sea ice.
Sea level
NOAA 2007; Canadell et al. 2007, PNAS
Atmospheric CO2 Concentration 0
1
2
3
4
5
6
7
8
9
1850 1870 1890 1910 1930 1950 1970 1990 2010
280
300
320
340
360
380
400
1850 1870 1890 1910 1930 1950 1970 1990 2010
Atm
oap
her
ic [
CO
2]
(pp
mv)
[CO2]
2 ppm/year
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1850 1870 1890 1910 1930 1950 1970 1990 2010
1850 1870 1890 1910 1930 1950 1970 1990 2010
[CO2]Year 2008
Atmospheric CO2 concentration:
385 ppm38% above pre-industrial
1970 – 1979: 1.3 ppm y-1
1980 – 1989: 1.6 ppm y1
1990 – 1999: 1.5 ppm y-1
2000 - 2008: 2.0 ppm y-1
2008: 2.3 ppm y-1
year ppm y-1
2000 1.242001 1.852002 2.392003 2.212004 1.612005 2.412006 1.792007 2.172008 2.28
Fate of Anthropogenic CO2 Emissions (2000-2007)
Canadell et al. 2007, PNAS; Global Carbon Project 2008, update
1.5 Pg C y-1
+7.5 Pg C y-1
Atmosphere46%
4.2 Pg y-1
Land29%
2.6 Pg y-1
Oceans26%
2.3 Pg y-1
C
RR
H
J
PRR
P
TS
KS
PS
MS
A1LS
Environmental ForcingPhysical• Seasonal circulation• Kuroshio intrusion• Coastal diluted waters • Internal tides/waves• Upwelling
Atmospheric• Winter and summer
monsoons • Typhoons• Asian dusts• ENSO events• Climate variability(Shaw & Chao, 1994; Shaw et al.,
1996)
Distinctives of the South China Sea
• Most of the sea is oligotrophic• Mixed-layer T is high (>22 oC) year round • Well stratified over the year (i.e., Effect of
convective overturn is small)• Shallow thermocline (<40 m) • Higher atmospheric dust inputs and Fe
fluxes• Seasonally alternative monsoons • Frequent occurrence of typhoons and
tropical depressions (over 10 events/year)
Tseng et. al 2005; 2007; 2009
• Seasonal variations in wind speed – Higher in Winter; Lower in Summer (Monsoon)
• Variations in T – never drops below 22oC.
• Seasonal variations in mixed layer depth - <40 m in most of the year; approach 100 m in Winter.
• Variations in nutrients – higher SRP, N+N in Winter
• Higher wind speed correlates with lower T and higher Chl-a
• Higher biomass and primary production in the Winter accompanies the higher nutrient concentrations.
1997 1998 1999 2000 2001 2002 2003 2004
I-ch
l (m
g/m
2 )
10
15
20
25
30
IPP
(m
gC
/m2 /d
)
0
200
400
WS
, f-
WS
(m
/s)
0
5
10
15
20
N+
N (
M)
0.0
0.1
0.2
0.3
0.4
0.00
0.02
0.04
0.06
SS
T,
f-S
ST
(o C)
24
26
28
30
32
De
pth
(m
)
0
20
40
60
80
100
S-c
hl (
mg/m
3)
0.0
0.2
0.4
(b)
(d)
(f)
(a)
(c)
(e)
SR
P (
M)
Win
dS
ST
MLD
S-c
hl
EPZ
TND
N+N
IPP
SRP
I-ch
l
Factors affect the oceanic CO2
variability in the MLD
ΔC = (ΔD +ΔE) + ΔF +ΔB +ΔT
Surface
MLD
Δ C fCO2 Δ
-+
Photosyn.
Remineral.
-+
-+
Photosyn.Δ B
Remineral.
- +
Air/sea gas exchange
- +- +
Air/sea gas exchange
ΔF
Mixed-Layer
++
ΔD ΔE
Mixing/upwelling
++
Δ Δ
Mixing/upwelling
-
+
-
+
-
+
Temp. effect ΔT
F = K fCO2 = k s (fCO2sw- fCO2air) Uncertainty: k- affected by wind, air bubble entrainment, sea surface conditions etc.
Estimating Air-Sea Exchange Fluxes of CO2
Wind
k pCO2
Air-Sea CO2Flux
SST
Transport
BiologyWindWaves
BubblesSurfaceFilm
Near SurfaceTurbulence
Bock et al. (1999)
Wind
k pCO2
Air-Sea CO2Flux
SST
Transport
BiologyWindWaves
BubblesSurfaceFilm
Near SurfaceTurbulence
Bock et al. (1999)
Factors influencing CO2 flux estimates
(Chen et al., 2006)
OR-I 508OR-I 508
Nov 15-24 1997Nov 15-24 1997
OR-I 546OR-I 546
April 7-20 1999April 7-20 1999
15~28 stations15~28 stations
fCO2 in northern SCS
Wet season (sea-to-air): ~0.006 Gt C per yr
Dry season (air-to-sea): ~0.004 Gt C per yr
SEATS: Mixed-layer fCO2
• Water fCO2 varies directly with T and inversely with chl-a – Low fCO2 in Winter (Solubility+Biological pump).
• fCO2 water < fCO2 air in Winter -> invasion ; fCO2 water > fCO2 air in Summer -> evasion
Wat
er
fCO
2 (
atm
)
340
350
360
370
380
390
400
Air fC
O2 (
atm)
CalculatedUnderway
1999 2000 2001 2002 2003 2004
fC
O2
(at
m)
-30
-20
-10
0
10
20
30
40
fCO2=8.8 x T + 123.0;(or fCO2=184.9 x e0.025)
r2= 0.81
Temperature Effect
Temp.
fCO 2
Temperature (oC)
22 24 26 28 30 32
fCO
2 ( a
tm)
340
360
380
400
Mar
May
Jun July
Aug
OctSept
Nov
Nov-DecDecJan
Feb-Mar
Year fCO2 change (μatm) per oC during
Spring-Summer Summer-Fall Winter
2000
2003
+8.8 (2.4%) -16.4 (4.4%) -2.7 (0.8%)
y = 8.78x + 125.56,
r2 = 0.98
y = 16.42x - 100.48,
r2 = 0.94
y = 2.73x + 275.44,
r2 = 0.41
Conceptual diagram of the contributing processes to the changes in salinity, temperature and the carbonate system in the mixed layer
Tseng et al., 2007
Location andOceanic regime
Temperature effect /Biological effect
Temperature effect -Biological effect
References
SEATS
HOT
BATS
KNOT
OSP
18º15’N , 115º35’ESouth China Sea,the largest
subtropical marginal sea
22º45’N, 158ºWNorth Pacific subtropical gyre
31º50’N, 64º10’WWestern North Atlantic
subtropical gyre
44ºN, 155ºENorthwestern subarctic Pacific
Ocean
50ºN, 145ºWNortheastern subarctic Pacific
Ocean
2.0 (80/40 atm)
2.6 (59/23 atm)
2.7 (150/55 atm)
0.8 (174/228 atm)
0.9 (100/115 atm)
+40 tam
+36 tam
+95 tam
-54 tam
-10 tam
This study
Calculated based onWinn et al. (1994)
Bates et al. (2001)Takahashi et al. (2002)
Calculated based onTsurushima et al. (2002)
Wong and Chan (1991)Takahashi et al. (2002)
Comparison with Other Time-series StationsThe relative importance of temp. & biological effect on seasonal fCO2 variability
(Takahashi et al., 2002, DSRII)
SEATS CO2 Flux (1999~2004)
“+” denotes evasion to the atmosphere“-” denotes invasion to the ocean
Net ≈ -0.02(Tseng et al., 2007)
Spring 0.04±0.34
Summer 1.02±0.02
Autumn 0.10±0.66
Winter -1.21±0.43
Seasons Fluxes (mol C m-2 y-1)
Months
SEATS CO2 Flux (1999~2007)
Net evasion flux: + 0.1 ± 0.7
• Normally CO2 invasion in Winter ; CO2
evasion in Summer
• CO2 flux varies inter-annually marked in red dashed circle
• Interannual anomaly may be linked to large-scale climate variability (e.g, ENSO, Pacific Decadal Oscillation etc.)
Comparison with other time-series stations
SEATS(1999-2004)
HOT
BATS
ReferencesAnnual sea-to-air flux
(molC m-2 year-1)
This study
Winn et al., 1994
Bates et al., 1996, 1998
+ 0.1 ± 0.7
-0.7
-0.3 to –0.8
SEATS(2002-2003)
Chou et al. 2004-0.1 to –0.2
Whole SCS Chai et al., 2009+0.33SEATS
(1990-2004) Chai et al., 2009- 0.04
-0.02 ± 1.06 Tseng et al., 2007
An increase of M-L fCO2 &NTCO2
NTCO2=(2.0 ± 1.4)X+ 1886.1; r2= 0.11, p=0.17
1999 2000 2001 2002 2003 2004
1999 2000 2001 2002 2003 2004
NfCO2=(2.6 ± 0.9)X+ 358.3; r2= 0.05, p<0.01
r2= 0.84
Interannual Trends of CO2 at SEATS
Mixed Layer
NTCO2(µmoles kg-1
yr-1)
fCO2(µatm yr-1)
HOT +1.0 (0.72~1.37)
(1988-1996)(Winn et al.,
1994)
BATS +1.7 (1988-1993)
(Bats et al,1996)
+1.6 ± 5.8 (1988-1998)
(Bats et al,2001)
+1.2 ± 0.3 (r2= 0.37, 1988-
2001)(Bats et al,2002)
+1.4 ± 10.7 (1988-1998)
(Bats et al,2001)
SEATS 2.0 ± 1.4(1999-2004)
2.6 ± 0.9(1999-2004)Tseng et al.,
2007
Feb.
Aug. Nov.
May
Chai et al., 2009
Modeled Surface fCO2 Distributionsaveraged +0.33 moles C m-2 year-1
References1. Tseng C.-M., George T.F. Wong, I. I. Lin, Chou-Long Wu, KK liu (2005) A
unique seasonal pattern in phytoplankton biomass in low-latitude waters in the South China Sea, Geophysical Research Letters, 32, L08608, doi:10.1029/2004GL022111.
2. Wen-Chen Chou, David D., Sheu, C.T. Arthur Chen, S. L. Wang and C.-M. Tseng (2005) Seasonal variability of carbon chemistry at the SEATS time-series site, northern South China Sea between 2002 and 2003. Terrestrial, Atmospheric and Oceanic Sciences, 16, 445-465.
3. Tseng C.-M., G.T.F. Wong, W.-C. Chou, B.-S. Lee, D.D. Sheu, K.-K. Liu (2007) Temporal Variations in the carbonate system in the upper layer at the SEATS station. Deep-Sea Research II, 54/14-15: 1448-1468.
4. Chai F., G. Liu1, H. Xue, L. Shi, Y. Chao, C.-M. Tseng, W.-C. Chou, K.-K. Liu (2009) Seasonal and Interannual Variability of Carbon Cycle in South China Sea: a Three- Dimensional Physical-Biogeochemical Modeling Study, Journal of Oceanography, 65, 703-720.
5. Liu, k.K., C.-M. Tseng, T.Y. Yeh, L.W. Wang, (2009) Elevated phytoplankton biomass in marginal seas in the low latitude ocean: A case study of the South China Sea, Advances in Geosciences (in press).
6. Tseng, C.-M., G.-C. Gong, L.-W. Wang, K.-K. Liu, and Y. Yang (2009), Anomalous biogeochemical conditions in the northern South China Sea during the El-Niño events between 1997 and 2003, Geophysical Research Letters, 36, L14611, doi:10.1029/ 2009GL038252.
7. Tseng, C.-M., K.-K. Liu, L.-W. Wang, and G.-C. Gong (2009), Anomalous hydrographic and biological conditions in the northern South China Sea during the 1997–1998 El Niño and comparisons with the equatorial Pacific. Deep-Sea Research I, doi:10.1016/ j.dsr.2009.09.004.
8. Liu, K.-K., C.-M. Tseng, C.-R. Wu, I-I Lin (2009) Biogeochemical fluxes of the South China Sea. In: Liu, K.-K., Atkinson, L., Quiñones, R., Talaue-McManus, L. (Eds.) Carbon and Nutrient Fluxes in Continental Margins: a Global Synthesis. IGBP Book Series, Springer, Berlin. Pp. 464-482.