SUPPLEMENTARY INFORMATION
Acceleration of modern acidification in the South China Sea driven
by anthropogenic CO2
Yi Liu1,2*, Zicheng Peng1, Renjun Zhou1,3, Shaohua Song2, Weiguo Liu2, Chen-Feng
You4*, Yen-Po Lin4, Kefu Yu5, Chung-Che Wu6, Gangjian Wei7, Luhua Xie7, George
S. Burr6 & Chuan-Chou Shen6*
1.
CAS Key Laboratory of Crust-Mantle Material and Environment, School of Earth and Space
Science, University of Science and Technology of China, Hefei 230026, China
2.
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese
Academy of Sciences, Xi’an 710075, China
3.
CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University
of Science and Technology of China, Hefei 230026, China
4.
Earth Dynamic System Research Center (EDSRC), National Cheng Kung University, Tainan 701,
Taiwan
5.
South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301,
China
6.
High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department
of Geosciences, National Taiwan University, Taipei 10617, Taiwan
7.
State Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of
Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
*Correspondence and requests for materials should be addressed to Y.L. (gee@ustc.edu.cn), C-F. Y.
(cfy20@mail.ncku.edu.tw) or C-C. S. (river@ntu.edu.tw).
Local setting
The South China Sea (SCS) covers an area of 3.5 × 106 km2, which is the largest
marginal sea in the world. This region is strongly dominated by a seasonal Asian
Monsoon1. Abundant coral reefs are distributed all over the SCS, which cover a
latitudinal range of 16o, providing excellent material for coral-based climate
research2-6. Our modern and fossil corals were drilled from Xiaodonghai Reef, off
south Hainan located in the northern SCS. At our sample site, for the period
2002-2011, the monthly chlorophyll a concentration (Chl), varies from 0.02 mg/m3 to
2 mg/m3 with prominent peaks occurring in winter (Supplementary Fig. 1d),
reflecting a Chl annual cycle in the South China Sea7. In parallel, the monthly mean
wind speed (Supplementary Fig. 1c), varying between 0.4 m/s and 11 m/s, also shows
strong winter peaks. Contrary to the pattern of annual cycles of Chl and wind speed,
most precipitation falls in in the summer (Supplementary Fig. 1b). Like the
precipitation, the sea surface temperature (SST) shows a maximum value (~30 °C) in
the summer and a minimum value (~22 °C) in the winter (Supplementary Fig. 1a).
Supplementary Figures
32
SST (oC)
(a)
28
24
precipitation (mm)
20
800
600
(b)
400
200
0
12
wind (m/s)
(c)
9
6
3
0
Chl (mg/m3)
2.5
2.0
(d)
1.5
1.0
0.5
0.0
1994
1996
1998
2000
2002
2004
2006
2008
2010
Supplementary Figure 1. Variations of monthly mean values of environmental
variables within the study area. (a) Sea surface temperature (SST). (b) Precipitation.
(c) Surface wind speed. (d) Sea surface chlorophyll a concentration (Chl). Monthly
SST data (17-19°N, 115-117°E) with 1° resolution from 1994 to 2011 were from the
Optimum Interpolation Sea Surface Temperature, Version 2, provided by NOAA:
(http://www.esrl.noaa.gov/psd/data/gridded/data.noaa.oisst.v2.html).
Wind
data
(17-19°N, 115-117°E) with a 0.25° resolution were from the Blended Sea Winds
provided
by
the
National
Climate
Data
Center
of
NOAA:
http://www.ncdc.noaa.gov/oa/rsad/air-sea/seawinds.html. Precipitation data (17-19°N,
115-117°E) were from the Global Precipitation Climatology Centre (GPCC) with a 1°
resolution (http://www.esrl.noaa.gov/psd/data/gridded/data.gpcc.html). Sea surface
Chl data (17.9-18.3°N, 109.3-109.7°E) from 2002 to 2011 were from MODIS
(Moderate Resolution Imaging Spectroradiometer) Level 3 with a spatial resolution of
4 km.
2.5
a
R2 = 0.38, n =105, p < 0.0001
Chl (mg/m3)
2.0
1.5
1.0
0.5
0.0
0
2
4
6
8
10
12
wind (m/s)
2.5
b
R2 = 0.0042, n = 105, p = 0.514
Chl (mg/m3)
2.0
1.5
1.0
0.5
0.0
0
200
400
600
800
1000
precipitation (mm)
Supplementary Figure 2. Correlations (Pearson) between (a) Chl and wind speed
and (b) Chl and precipitation from AD 2002-2011.
B ( o/oo )
23
a
d
δ
24
11
25
22
1050
1100
1850
1900
1950
2000
1850
1900
1950
2000
1850
1900
1950
2000
8.6
b
pHcf
e
8.4
1050
pHsw
8.2
1100
f
c
8.0
7.8
1050
1100
Year (A.D.)
Supplementary Figure 3. Time series of measured δ11B and reconstructed pHcf
and pHsw. a-c, Data for fossil Porites coral Dong-5 from AD 1048-1079. d-f, Data
for modern Porites coral Song-5 during AD 1839-2001. Vertical red bars denote the
2σ uncertainty.
8.4
a. Flinders Reef
pHsw
8.2
8.0
b. Arlington Reef
7.8
8.4
7.6
c. St. ALOHA (Hawaii)
8.2
-0.0018 pH year-1
pHsw
8.2
8.0
8.0
d. Xiaodonghai Reef
7.8
-0.0015 pH year-1
7.8
7.6
1750
7.6
1800
1850
1900
1950
2000
Year (A.D.)
Supplementary Figure 4. Time series of modern observational and reconstructed
pHsw. Reconstructed pHsw of (a) Frinders Reef13 (cyan) and (b) Arlington Reef14
(blue) from the Great Barrier Reef (GBR). (c) Observational pHsw at Station ALOHA,
Hawaii15 (pink). (d) Reconstructed Xiaodonghai Reef pHsw in the South China Sea
(SCS) (this study, red). Solid black lines show the decreasing trends of pHsw in
Hawaii and the SCS.
pHsw
8.4
pHsw
8.2
a
8.0
7.8
-2.0
-2.8
δ
13
C ( o/oo )
b
-2.4
-3.2
-3.6
-5.0
c Col 1 vs Col 2
-5.2
δ
18
O ( o/oo )
-4.8
-5.4
1850
1900
1950
2000
Year (A.D.)
Supplementary Figure 5. Time series of (a) reconstructed pHsw, (b) measured
δ13C, and (c) measured δ18O of the modern Porites coral Song-5 during AD
1839-2001.
2000
pHsw
8.2
1600
Col 35 vs Col 36
8.0
R2 = 0.011, p = 0.613
1200
precipiataion (mm)
8.4
7.8
1850
1900
1950
2000
Year (A.D.)
Supplementary Figure 6. Comparison between pHsw and precipitation. Green line
denotes precipitation variation and red line coral-inferred pHsw in Xiaodonghai Reef.
Precipitation data are from the GPCC as in Supplementary Fig. 2b.
Supplementary Figure 7. Local instrumental seawater pH in AD 2009 and 2010.
This pH record is characterized with higher pH in winter and lower in summer. pH
was measured with an Orion pH glass electrode (ROSS Combination pH/model
81-02)and a Corning pH meter (Model pH/ion analyzer 350) with a precision of 0.005
pH units16. SST is also shown.
Supplementary Tables
Supplementary Table 1. U-Th isotopic compositions and 230Th date of the first
annual banding of the 32 yr-section coral Porites fossil Dong-5
Sample
No.
Dong-5-4
2σ
238
232
Th
ppt
δ234U
measureda
2543
± 7.1
817.8
± 3.7
144.3
± 3.6
U
ppb
230
Th/238U
activityc
0.010137
±0.000051
230
Th/232Th
ppmd
520.6
± 3.2
Age (y)
uncorrected
Age (y)
correctedc,e
δ234U
correctedb
971.4
± 5.7
964.0
± 6.8
144.7
± 3.6
Chemistry8 and instrumental analysis9 was performed in 2012. Analytical errors are
2σ of the mean.
a 234
δ U = ([234U/238U]activity - 1) x 1000.
b 234
δ Uinitial corrected was calculated based on 230Th age (T), i.e., δ234Uinitial =
δ234Umeasured X eλ234*T, and T is corrected age.
c 230
Th/238Uactivity = 1 - e-λ234*T + (δ234Umeasured/1000)[λ230/(λ230-λ234)](1 - e-(λ230 -λ234) T ),
where T is the age. Decay constants are 9.1705 x 10-6 yr-1 for 230Th, 2.8221 x 10-6
yr-1 for 234U (ref.10), and 1.55125 x 10-10 yr-1 for 238U (ref.11).
d
The degree of detrital 230Th contamination is indicated by the 230Th/232Th atomic
ratio instead of the activity ratio.
e
Age corrections were calculated using an estimated atomic 230Th/232Th ratio of 4 (±2)
ppm (ref. 12).
Supplementary Table 2. The dataset of the modern coral Song-5 from AD
1838-2001
Years (A.D.)
δ11B
pHcf
pHsw
δ13C
δ18O
1998-2001
1994-1997
1990-1993
1986-1989
1982-1985
1978-1981
1974-1977
1970-1973
1966-1969
1962-1965
1958-1961
1954-1957
1950-1953
1946-1949
1942-1945
1938-1941
1934-1937
1930-1933
1926-1929
1922-1925
1918-1921
1914-1917
1910-1913
1906-1909
1902-1905
1898-1901
1894-1897
1890-1893
1886-1889
1882-1885
1878-1881
1874-1877
1870-1873
1866-1869
1862-1865
1858-1861
1854-1857
1850-1853
1846-1849
1842-1845
1838-1841
23.03
23.28
22.16
22.39
23.27
23.47
23.54
23.13
23.41
22.75
23.10
23.96
24.18
24.10
24.23
23.67
23.53
24.11
23.86
23.66
23.50
24.14
24.37
23.80
24.23
23.77
23.57
24.79
24.49
23.90
23.66
24.56
24.42
24.91
24.69
24.88
24.68
24.43
24.32
24.67
24.21
8.43
8.45
8.37
8.39
8.45
8.46
8.46
8.44
8.46
8.41
8.43
8.49
8.51
8.50
8.51
8.47
8.46
8.50
8.48
8.47
8.46
8.50
8.52
8.48
8.51
8.48
8.47
8.54
8.52
8.49
8.47
8.53
8.52
8.55
8.54
8.55
8.54
8.52
8.51
8.54
8.51
7.95
7.98
7.82
7.86
7.98
8.01
8.02
7.96
8.00
7.91
7.96
8.08
8.11
8.09
8.11
8.04
8.02
8.10
8.06
8.03
8.01
8.10
8.13
8.05
8.11
8.05
8.02
8.19
8.15
8.07
8.03
8.16
8.14
8.21
8.18
8.20
8.17
8.14
8.13
8.17
8.11
-3.12
-3.29
-3.33
-3.14
-3.25
-3.43
-2.87
-3.18
-3.22
-2.82
-2.64
-2.84
-2.34
-2.65
-2.64
-2.69
-3.06
-3.26
-3.07
-2.58
-2.89
-2.80
-2.32
-2.51
-3.15
-2.73
-2.33
-2.36
-3.11
-2.70
-2.25
-2.40
-2.10
-2.38
-2.45
-2.96
-3.25
-2.67
-2.50
-2.74
-2.88
-5.22
-5.11
-5.10
-5.14
-5.38
-5.09
-5.10
-4.95
-5.29
-5.00
-4.92
-5.28
-5.11
-5.08
-5.02
-5.20
-5.19
-5.19
-5.31
-5.18
-5.20
-5.19
-5.14
-5.16
-5.20
-5.04
-5.16
-4.96
-5.12
-5.01
-4.92
-5.12
-5.08
-5.07
-4.87
-5.14
-4.86
-5.00
-4.96
-5.03
-5.01
Supplementary Table 3. Biweekly geochemistry dataset of the modern coral Song-5
in AD 2000
Sample No.
Song-2000-1
Song-2000-2
Song-2000-3
Song-2000-4
Song-2000-5
Song-2000-6
Song-2000-7
Song-2000-8
Song-2000-9
Song-2000-10
Song-2000-11
Song-2000-12
Song-2000-13
Song-2000-14
Song-2000-15
Song-2000-16
Song-2000-17
Song-2000-18
Song-2000-19
Song-2000-20
Song-2000-21
Song-2000-22
Song-2000-23
Song-2000-24
Song-2000-25
Song-2000-26
Song-2000-27
Song-2000-28
Song-2000-29
Song-2000-30
δ11B
23.21
22.71
22.67
22.69
22.31
21.70
22.34
22.18
22.84
22.77
21.93
22.68
22.50
22.10
22.06
22.19
22.47
22.60
23.12
23.34
23.11
23.09
23.30
pHcf
pHsw
8.46
8.01
8.39
7.87
8.37
7.83
8.37
7.82
8.34
7.75
8.27
7.60
8.33
7.74
8.35
7.78
8.42
7.93
8.38
7.85
8.34
7.75
8.40
7.89
8.39
7.85
8.37
7.83
8.34
7.75
8.36
7.81
8.36
7.80
8.38
7.84
8.41
7.90
8.43
7.94
8.43
7.94
8.46
8.01
8.49
8.08
δ13C
δ18O
-3.16
-3.17
-3.67
-3.32
-3.74
-3.75
-3.54
-3.57
-3.21
-3.16
-3.47
-3.48
-3.17
-2.75
-3.01
-3.25
-3.72
-3.49
-3.42
-3.30
-2.79
-2.75
-2.88
-3.01
-3.14
-3.07
-3.46
-3.21
-3.58
-3.39
-5.07
-4.84
-5.21
-5.04
-5.43
-5.65
-5.68
-5.79
-6.12
-5.87
-5.51
-5.21
-5.61
-5.45
-5.30
-5.38
-5.18
-5.57
-5.38
-5.62
-5.50
-5.60
-5.57
-5.35
-4.95
-4.73
-4.97
-4.68
-4.86
-4.97
Supplementary Table 4. The dataset of the fossil coral Dong-5
4-year
intervals
δ11B
pHcf
pHsw
1
2
3
4
5
6
7
8
24.56
24.40
24.63
24.89
24.71
24.55
25.24
24.22
8.53
8.52
8.53
8.55
8.54
8.53
8.57
8.51
8.16
8.14
8.17
8.20
8.18
8.16
8.25
8.12
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3.
4.
5.
6.
7.
8.
9.
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