dynamics of the intertropical convergence zone supplementary … · 2016-12-01 · 47. the...

Supplementary Information for 1

Dynamics of the intertropical convergence zone over the western 2

Pacific during the Little Ice Age 3

Hong Yan, Wei Wei, Willie Soon, Zhisheng An, Weijian Zhou, Zhonghui Liu, Yuhong 4

Wang, Robert M. Carter 5

6

7

This file includes: 8

Supplementary discussion 9

Supplementary Figure s1 to s10 10

Supplementary Table s1 11

References 12

13

14

15

16

17

18

19

20

21

Dynamics of the intertropical convergence zone over the western Pacific during the Little Ice Age

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NGEO2375

NATURE GEOSCIENCE | www.nature.com/naturegeoscience 1

© 2015 Macmillan Publishers Limited. All rights reserved

http://dx.doi.org/10.1038/ngeo2375

Supplementary discussion: 22

Supporting evidence from decadal-multidecadal-centennial scale oscillations 23

In addition to the MCA-LIA-recent 150 years transition, other multidecadal-scale 24

oscillations in solar output have also occurred over the last millennium1,2

. If solar 25

output is a significant factor for tropical hydrologic variation over the last millennium, 26

then the paleo-hydrology records should have recorded the signals of these 27

oscillations. Although most proxy-hydrology records are low resolution, and not 28

accurately dated enough to capture decadal-centennial-scale variations, such 29

oscillations have been detected in several high resolution precipitation records from 30

the Asian-Australian monsoon area. These multi-decadal hydrologic variations are 31

consistent with our proposal of a contracted monsoon/ITCZ during solar irradiance 32

minimum. For example, some decadal changes in a speleothem record from north 33

China3 and a coral record from northeast Australia

4 are correlated with decadal 34

variations of the solar irradiance, with increased rainfall during the peaks of the solar 35

activity (D4 and D8 records in Fig. s10). Meanwhile, and conversely, hydrological 36

records from the western Pacific region5 reveal increased rainfall during the troughs 37

of the solar output (W2 record in Fig. s10). An increased rainfall in the tropical 38

western Pacific during the solar minimum was also supported by a recent study which 39

found that the precipitation in Indonesia increased abruptly at the time of the solar 40

minimum around 2800 yr BP6. 41

On the other hand, power spectrum analysis indicates that the periodicities of the 42

speleothem δ18

O series from monsoonal China3,7-9

are similar to and consistent with 43

the presence of solar cycles - such as the well known 80-120 yr and ~20 yr 44

periodicities. 45

It is important to note, however, that not all the variations in rainfall records from 46


the Asian-Australian monsoon area exhibit good correspondence with solar output. 47

For example, no multi-decadal oscillations were observed in fluvial sedimentary 48

records from the Magela Creek Flood Plain10

. However, good reasons exist that could 49

explain disagreements between decadal variation in a proxy record and the solar 50

activity record. Those reasons include time delays for hydrologic changes in response 51

to solar activity forcing, spatial differences of the local and regional rainfalls in 52

response to the solar forcing (e.g., wet, dry and no changes in different regions in 53

response to the same solar minima) and a lack of quality in particular proxy 54

records (e.g. time resolution, error of age model). 55

Finally, it is noteworthy that the impacts of decadal to centennial scale cycles in 56

solar activity on tropical hydrology have long been known to occur in speleothem, 57

lake and marine sediment records from tropical Latin America, central Africa and 58

elsewhere11-17

. 59

60

The contraction of ITCZ and the strengthening of Pacific Walker Circulation 61

during LIA 62

The extended clear dry conditions that obtained in mid-northern part of the mainland 63

China and northern Australia during the LIA are consistent with the disappearance or 64

weakening of the ITCZ/monsoonal rainfall in these regions, and point to a contraction 65

of the ITCZ’s sphere of influence (see the summary presented in Fig. s6 and s7). At 66

the same time, the precipitation zones converged more narrowly within the tropics and 67

resulted in more rainfall in the Indo-Pacific warm-fresh pool region. However, the 68

contracted ITCZ/monsoon was probably not the only cause of dilution of the warm 69

pool. As well, concurrent changes of ENSO/Walker circulation, which today has a big 70

impact on modern western Pacific hydrology, probably contributed to the changes in 71


multi-decadal to centennial- scale precipitation in this region5,18,19

. 72

Indeed, a number of papers have addressed the ENSO/Walker circulation 73

variations in the tropical Pacific during the past millennium. Overall, the results 74

remain unclear, controversy stemming from a perceived contradiction between the 75

reduced east-west tropical Pacific SST gradient (El Niño-like) and the enhanced 76

Pacific Walker circulation (La Niña-like)20

. The best available SST reconstructions in 77

the western19,21

, eastern22,23

and mid24

tropical Pacific suggest25,26

an LIA marked by 78

relative warming in the eastern and central tropical Pacific, accompanied by 79

substantial cooling in the western equatorial ocean and a more El Niño-like state 80

(when compared and contrasted with conditions during the MCA). In contrast, nearly 81

all hydrological reconstructions from the tropical Pacific suggested a more La 82

Niña-like mean state during the LIA than during the MCA. These include records 83

from the Indo-Pacific5,18,19,21,27

, the central tropical Pacific 28

and the eastern 84

equatorial Pacific29,30

that indicate wetter, drier and drier conditions, respectively, 85

during the LIA than during the MCA. Meanwhile, theoretical models and computer 86

simulations also project contradictory results for the mean climatic state during the 87

LIA and the MCA. For example, the “ocean dynamical thermostat” mechanism31-33

88

predicts a more El Niño-like state in the LIA than in the MCA, while the coupled 89

general circulation models (CGCM) project a possible strengthening of the Walker 90

circulation (La Niña-like state) during the LIA34,35

(see ref20

for detailed discussion). 91

Several co-working factors could contribute to explain the conflict between the SST 92

records and the hydrological records, such as the inappropriate interpretation of the 93

current SST/hydrological records (e.g. the primary mode of the SST or hydrological 94

records in tropical Pacific on centennial scale perhaps might not be ENSO variation, 95

but instead represent the meridional temperature gradient or ITCZ changes). A 96

decoupling between the atmospheric and oceanic response to forcing on centennial 97


timescales is another possibility. More high-resolution proxy records and climate 98

models are thus needed in the future research that seeks to clarify this unresolved 99

puzzle. 100

In summary, although the temperature-based reconstructions indicate an El 101

Nino-like SST pattern existed in the tropical Pacific during the LIA24,25

, the 102

hydrological studies, based upon either proxy records5,18,19,29

or model simulations34

, 103

present a clear strengthening of the Pacific Walker circulation during the LIA, which 104

in turn would cause increased precipitation in the Indo-Pacific warm-fresh pool region. 105

Moreover, the model results in this study also implied an increased zonal precipitation 106

contrast between east and west tropical Pacific during the LIA (Fig. s9 and ref36

), 107

which would probably also manifest itself as an enhanced Pacific Walker circulation. 108

That is to say, the contracted western Pacific monsoon/ITCZ and enhanced Pacific 109

Walker circulation probably co-existed during the LIA interval, with both mechanisms 110

contributing extra precipitation to the wet and warm pool region of the western 111

Pacific. 112

This co-existence of a contracted ITCZ/monsoon and strengthened Pacific 113

Walker circulation during the LIA raises some issues that need to be addressed in 114

future studies. For example, both ITCZ contraction and Walker circulation 115

strengthening could increase convection in the western Pacific warm pool, but which 116

factor is the dominant cause? Also, what interaction, if any, occurs between ITCZ 117

behavior and Walker circulation on multi-decadal to centennial scales (e.g., the 118

contraction of the western Pacific marine-continental ITCZ could increase convection 119

activity in the western Pacific, and therefore enhance Pacific Walker Circulation)? 120

121

122


A brief description of the ECHO-G and MPI-ESM models: Ability to simulate 123

global monsoon and monsoon-related climate variations 124

ECHO-G model: the ECHO-G model has very reasonable performance on simulating 125

the monsoonal precipitation. In Liu et al. (2009)36

, the authors have compared the 126

simulated annual mean precipitation and global monsoon mode with those from the 127

observation and reanalysis data (Figure 1 in their paper). They show quite consistent 128

patterns and confirm the reliability of the model performance. In this paper, the 129

authors have conducted two ECHO-G experiments, one with fixed external forcing 130

used as a control experiment and the other with three external forcings, i.e. solar 131

variability, greenhouse gas concentration and volcanic forcing36

. 132

MPI-ESM model: the basic model simulation and capability of MPI-ESM for the last 133

millennium has been described by Jungclaus et al. (2010)37

. Although there is no 134

special focus on the performance of the model on monsoonal precipitation in that 135

paper, a follow-up paper by Man et al. (2012)38

studied theEast Asian summer 136

monsoon during the last millennium. Man et al. (2012) compared the simulated 137

summer precipitation over the East Asian monsoon region with that observed, using 138

reanalysis data. Figure 2 in their paper reports good agreement among datasets 139

regarding the precipitation and the 850-hpa wind patterns. After the validation of the 140

simulation results, the authors also demonstrated that the model can capture the East 141

Asian summer monsoon change during the MCA and LIA periods via model-data 142

comparison. Hence, the works by Man et al. (2012) add confidence to our use of 143

MPI-ESM model for studying the TSI-induced ITCZ contraction hypothesis around 144

the Indo-Pacific warm-fresh pool region during the Little Ice Age interval. 145

146

147


Supplementary Figures 148

149

Figure s1: Hydrologic proxy records D139

, D240

, D38, D4

3 and D5

7 from the EASM 150

area showing dry condition during the LIA relative to MCA/recent 150 years. The 151

locations of these records are shown in Fig.1. Please see the Methods section for the 152

definitions of the Relative Wet Index (RWI) and the wet/dry condition during the LIA 153

relative to the MCA/recent 150 years. 154

155

80

85

90

-8.5

-8

-7.5

-0.6

-0.3

0

0.3

0.6

-0.5

0

0.5

1

-9.5

-9

-8.5

-8

-7.5

1000 1200 1400 1600 1800 2000

AD

LIA

Hes

han

g c

ave

(30

.5°N

)

δ1

8O

(‰,V

PD

B)

Go

ngh

ai lak

e (3

8.9

°N)

S-3

00

mT

(%

)

MCA

RWI= -85%Wet

Wan

xia

ng

cav

e (3

3.3

°N)

δ1

8O

(‰,V

PD

B)

Hu

ang

ye

cav

e (3

3.5

°N)

δ1

8O

(‰,V

PD

B)

Lo

ngx

i (3

5°N

)

Dro

ugh

t/F

loo

d in

dex

Dry

D1

D2

D3

D4

D5

RWI= -153%

RWI= -110%

RWI= -74%

RWI= -112% RWI= -102%

RWI= -145% RWI= -144%

RWI= -96% RWI= -90%

Dry LIA

Dry LIA

Dry LIA

Dry LIA

Dry LIA


156

Figure s2: Hydrologic proxy records N19, N2

41, W1

42,43 and W2

5,27 from the EASM 157

area indicate no apparent change of rainfall and wet conditions during the LIA relative 158

to the MCA. The locations of these records are shown in Fig.1. Please see the 159

Methods section for the definitions of the Relative Wet Index (RWI) and the wet/dry 160

condition during the LIA relative to the MCA/recent 150 years. 161

162

163

164

-8.0

-7.5

-7.0

Wet

Dry

20

30

40

50

60

-2

-1

0

1

2

1000 1200 1400 1600 1800 2000AD

-9.0

-8.0

-7.0

Do

ngg

e ca

ve

(25

.3°N

)

δ1

8O

(‰,V

PD

B)

Lo

ngq

uan

cav

e (2

5.5

°N)

δ1

8O

(‰,V

PD

B)

Do

ngd

ao,

SC

S (

16

.7°N

)

MG

S (

µm

)

Hu

guan

g M

arr

(21

.9°N

)

No

n-r

esid

ual

Sr

(µg

/g)

LIAMCAN1

N2

W1

W2

RWI= -24%

RWI= -153%

RWI= 29%RWI=-24%

RWI= 121%

RWI= 189%

RWI= 156% RWI= 163%

No apparent change

No apparent change

LIA relative to MCA

Wet LIA

Wet LIA


165

Figure s3: Hydrologic proxy records D1044,45

, D1210

, D1346

from the northern 166

Australia monsoon area showing dry condition during the LIA relative to the 167

MCA/recent 150 years. The locations of these records are shown in Fig. 2. Please see 168

the Method section for the definitions of the Relative Wet Index (RWI) and the 169

wet/dry condition during the LIA relative to the MCA/recent 150 years. 170

171

0

2

4

6

8

10

12

14

16

-8.5

-8.0

-7.5

-7.0

-6.5

-6.0

-5.5

-5.0

-2.5

-1.5

-0.5

0.5

1.5

1000 1200 1400 1600 1800 2000

AD

Mag

ela

Cre

ek P

lain

(12°S

)

Sed

imen

t fl

ux (

10-3

*g/c

m2/y

ear)

RWI= -155%

LIAMCAD12

D10

Bro

mfi

eld S

wam

p (

17.3

°S)

Hum

ific

atio

n r

esid

ual

s

Wet

Dry

KN

I-51 c

ave

(15.3

°S)

δ1

8O

(‰,V

PD

B)

D13

RWI= -178%

RWI= -105%RWI= -142%

RWI= -92%RWI= -80%

Dry LIA

Dry LIA

Dry LIA


172

Figure s4: Coral records D647-49

, D750

, D84 and D9

51 from northeast Australia showing 173

dry conditions during the LIA relative to the last 150 years (i.e., D6, D7 and D8: 174

seawater δ18

O record calculated from the coral δ18

O and Sr/Ca; D9: rainfall 175

reconstruction in Great Barrier Reef derived from coral luminescence). The locations 176

of these records are shown in Fig. 2. Please see the Methods section for the definitions 177

of the Relative Wet Index (RWI) and the wet/dry condition during the LIA relative to 178

the most recent 150 years. 179

180

181

Wet

Dry

-100

0

100

200

-0.4

-0.2

0

0.2

0.4

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

AD

LIAN

ew C

aled

onia

(2

2°S

)

Sea

wat

er δ

18O

(‰

,VP

DB

)

Dry LIA

Recent

150 years

RWI= -71%

Tro

pic

al Q

uee

nsl

and

(~

17

°N)

Rai

nfa

ll (

mm

)Gre

at B

arri

er R

eef

(~1

8.5

°S)

Sea

wat

er δ

18O

(‰,V

PD

B)

D6

D8

D9

1400

Dry LIARWI= -143%

Dry LIARWI= -92%

1500 1600 1700 1800 1900 2000

-0.4

-0.2

0

0.2

0.4

D7

Dry LIARWI= -62%

Flin

der

s R

eef

(1

7.5

°S)

Sea

wat

er δ

18O

(‰

,VP

DB

)


182

Figure s5: Proxy hydrology records N352

, N453

, W354

, W418

and W519,21

from the ASM 183

area indicate no apparent change of rainfall and wet conditions during the LIA relative 184

to the MCA. The locations of these records are shown in Fig. 2. Please see the Method 185

section for the definitions of the Relative Wet Index (RWI) and the wet/dry condition 186

during the LIA relative to the MCA/recent 150 years. 187

188

-160

-140

-120

-31

-29

-27

-25

-23

-0.7

-0.5

-0.3

-0.1

1000 1200 1400 1600 1800 2000

-2

-1

0

1

2

3

AD

-6.9

-6.7

-6.5

-6.3

-6.1

-5.9

-5.7

Lak

e L

adin

g (

8°S

)

Lea

f w

ax δ

D (

‰,V

PD

B)

Lia

ng

Lu

ar c

ave

(8.5

°S)

δ1

8O

(‰,V

PD

B)

Lo

gun

g L

ake

(8°S

)

δ1

3C

(‰,V

PD

B)

LIAMCA

N4

N3

W3

W5

W4

Mak

assa

r S

trai

t (5

°S)

δ1

8O

(‰,V

PD

B)

Mak

assa

r S

trai

t (4

°S)

Lea

f w

ax δ

D (

‰,V

PD

B)

Wet

Dry

RWI= 87%RWI= 41%

RWI= 124%RWI= 176%

RWI= 152% RWI= 142%

RWI= 152%

RWI= 86%

RWI= 78%

RWI= -138%

No apparent change

Wet LIA

Wet LIA

Wet LIA

Wet LIA relative to

MCA


189

Figure s6: Near synchronous retreat of the EASM and the ASM during the LIA. 190

Hydrological records from the front areas of the EASM (top panel) and the ASM 191

(middle panel). The composite hydrological changes (30 years smoothing) of the 192

EASM (the average of records D1, D2, D3 and D4) and the ASM (the average of 193

records D10, D12 and D13) are shown in the bottom panel. All proxy records are 194

normalized to standard Z-scores. Standard Z-scores are calculated according to 195

Z=(X-V)/SD; where X is original value, V is the averaged of each time series, and SD 196

is the standard deviation of each time series. 197

198

-3

-2

-1

0

1

2

3

4

1000 1200 1400 1600 1800 2000

D1

D2

D3

D4

-3

-2

-1

0

1

2

3

D12

D13

D10

Year (AD)

Z-s

core

s

Z-s

core

s

Z-s

core

s

-2

-1

0

1

2

1000 1200 1400 1600 1800 2000

EASM

ASMLIA

Wet

Dry

EASM

ASM


199

Figure s7: Schematic map depicting the current extent of the monsoon/ITCZ in the 200

East Asia-Australia area, and the hypothesized contraction of the monsoon/ITCZ zone 201

during the LIA. The hydrologic records in Figure 1 and 2 are also marked here. The 202

pink lines indicate the northern and southern limits of modern EASM and ASM. The 203

red shaded areas indicate the areas with possibly lower precipitation during the LIA 204

than during the MCA. The blue shaded area indicates the area with possibly more 205

precipitation during the LIA than occurred during the MCA. The monsoon/ITCZ 206

rainbelt would spend more time in the blue shaded area during the LIA than it did 207

during the previous MCA, while the rainbelt would spend less time in, or even 208

disappear from, the red shaded areas during the LIA. 209

210

D1D2D3

D4 D5

N1N2

W1

W2

60E 80E 100E 120E 140E 160E

45N

30N

15N

EQ

15S

30S

D6D7

D8

D9D12 D10

N3

W3

W4W5

D13

Dry LIA area?

Modern southern monsoon limit

Modern northern monsoon limit

Dry LIA area?

Wet LIA area?

D11N4


-1

-0.5

0

0.5

1

1000 1200 1400 1600 1800 2000

-1

-0.5

0

0.5

1

1000 1200 1400 1600 1800 2000

AD

W/M

2W

/M2

-2.5

-1.5

-0.5

0.5

1.5

2.5

1000 1200 1400 1600 1800 2000

-2.5

-1.5

-0.5

0.5

1.5

2.5

1000 1200 1400 1600 1800 2000

AD

W/M

2

W/M

2

TSI (%MM decrease: -0.25%) TSI (%MM decrease: -0.65%)

TSI (%MM decrease: -0.25%) TSI (%MM decrease: -0.65%)

-0.5

-0.25

0

0.25

0.5

1000 1200 1400 1600 1800 2000

-0.6

-0.3

0.0

0.3

0.6

1000 1200 1400 1600 1800 2000

AD

W/M

2W

/M2

TSI (%MM decrease: -0.1%)

TSI (%MM decrease: -0.1%)

LIA LIA LIA

LIA LIA LIA

211

Figure s8: Top panels show the solar forcing variations over the last millennium 212

caused by the changes of the total solar irradiance (TSI, red line)1 and orbital 213

parameters (green is the July insolation at 23.5ºN and blue is the January insolation at 214

23.5ºS)55

. The TSI curve in the left, middle and right panel has been calculated by 215

assuming a TSI reduction by -0.1%, -0.25 % and -0.65% during the Maunder 216

Minimum1,56,57

. Please note the drastically different amplitude of solar forcing as 217

indicated by the changing vertical scales for each TSI scenario and that the January 218

and July dates may have been be shifted by about 17 days from AD 1000 to 2000 219

owing to apsidal precession58

of the Earth-Sun orbits. The bottom panel shows the 220

total solar forcing of the Northern Hemisphere at 23.5ºN (green) and the Southern 221

Hemisphere at 23.5ºS (blue), calculated by adding up the solar forcing that results 222

from changes in the intrinsic solar output and orbital parameters. The total solar 223

forcing for the last 1000 years shows the dominance of the symmetric solar forcing 224

rooted in the intrinsic solar magnetic activity variations rather than the anti-symmetric 225

solar insolation forcing caused by the Sun-Earth orbital precession parameters. 226

It should be noted that the range of the TSI amplitude change of about 0.2% to 227

0.6% shown in Bard et al (2000)1 is fully consistent with the empirical results shown 228

in Zhang et al. (1994)59

, and that the independent estimates for TSI variations from 229


the study of solar-type stars by Zhang et al. (1994) has not yet been objectively ruled 230

out. We also wish to emphasize that our adopted choice of TSI amplitude of variations 231

follow empirically constrained results based on observations rather than theoretical 232

modeling works. That fact explains why the TSI in our climate simulation 233

experiments (-0.25%) and Liu et al (2009) (-0.3%) are still relatively larger than the 234

-0.1% recommended by Schmidt et al. (2011) for TSI change between the Maunder 235

Minimum and present57

. The 0.1% value is roughly rooted in the measured TSI 236

peak-to-peak amplitude for the 11-yr solar cycle variations (see e.g., Willson and 237

Hudson 1991)60

, whereas a drastically smaller TSI amplitude value of 0.04% listed in 238

Schmidt et al (2011) is specifically related to the theoretical assumption of no (or only 239

very small) TSI change in the published work of Wang et al. (2005)61

. Because the 240

small TSI amplitude variation is largely a theoretical assumption rather than any 241

confirmed, measured reality, we have chosen to adopt -0.25% as the optimal TSI 242

amplitude value for our climate simulation experiments shown in Figure 3d and 243

Figure s9. 244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259


260

-0.1

5-0

.05

00

.05

0.1

5

13

63

13

65

13

67

800 1000 1200 1400 1600 1800

Year (AD)

GM

I a

no

ma

lie

s [m

m/d

ay]

TS

I [w

/m^2

]

(c)(b)

(d)

(a)

261

Figure s9: (a) Low-pass (> 90-year timescales) filtered global monsoon index (GMI; 262

black) based on MIP-ESM last millennium simulation with only TSI (red) as external 263

forcing37

. In this simulation, 0.25% TSI change from the Maunder Minimum to 264

present has been applied (see Fig. s8 for our choice of the TSI data and amplitude). 265

Here the GMI is defined as the sum of local summer precipitation over the monsoon 266

domains in both hemispheres, where the annual range (MJJAS precipitation minus 267

NDJFM precipitation in the NH and NDJFM minus MJJAS precipitation in the SH) 268

of precipitation exceeds 2 mm/day and the local summer precipitation exceeds 55% of 269

annual rainfall36

. (b) Summer precipitation pattern under low solar activity conditions 270


over the last millennium. The anomalies have been calculated by regression analysis 271

of the GMI with the local summer (June to August in the Northern Hemisphere and 272

December to February in the Southern Hemisphere) precipitation during AD 273

850-1850. A low-pass filter has been applied to both the GMI and precipitation filed 274

prior to the analysis in order to concentrate on precipitation pattern associated with the 275

solar variability on multidecadal-to-centennial timescales. The high correlation 276

(r=0.45 when GMI lags TSI by 10 years) between the two indices suggests that the 277

centennial precipitation pattern here is primarily forced by the solar variability. The 278

zonal mean precipitation pattern, which revealed decreased monsoon precipitation in 279

both northern and southern tropical-subtropical monsoon area, and increased rainfall 280

in equatorial area, is also given (c). (d) The simulated annual mean precipitation 281

anomaly during the late Maunder minimum62

of the LIA (AD 1690-1740) with 282

reference to the long-term (AD 1000-1800) mean (i.e., similar to Fig. 3d, but Fig. 3d 283

focuses on western Pacific region while here a circum-global view over the tropics is 284

presented). Here the interval for LIA has been chosen according to the simulated GMI 285

in (a), when the model has better performance on simulating the monsoonal 286

precipitation associated with the solar irradiance during the Maunder Minimum. 287

288


289

Figure s10: Comparison between solar irradiance2 (in the original net radiative 290

forcing units defined in Ref. 2) and hydrological records D43, D8

4 and W2

5 from the 291

Asian-Australian monsoon area. The vertical shaded bars indicate time intervals of 292

decadal-scale solar irradiance minima. Significant correlations were observed between 293

solar irradiance and hydrological records D8 (r = 0.54, p<0.05) and W2 (r = 0.68, 294

p<0.05). We adopted the composite solar irradiance record from Ref. 2, which is the 295

splice of the 0.25% TSI series from Ref. 1 for 1000-1610 AD (hence similar to results 296

shown in the top panels of Fig. s8); another higher temporal resolution TSI taken from 297

Ref. 2 was used for the 1610-1998 AD interval. It is worth noting that the calculated 298

- 0. 3

- 0. 2

- 0. 1

0

0. 1

0. 2

0. 3

- 3

- 2. 5

- 2

- 1. 5

- 1

- 0. 5

0

0. 5

1

1. 5

2

1000 1500 2000

- 0. 6

- 0. 4

- 0. 2

0

0. 2

0. 4

0. 6

- 8. 8

- 8. 6

- 8. 4

- 8. 2

- 8

- 7. 8

- 7. 6

- 7. 4

- 2

- 1. 5

- 1

- 0. 5

0

0. 5

1

1. 5

2

- 0. 70

- 0. 60

- 0. 50

- 0. 40

- 0. 30

- 0. 20

- 0. 10

0. 00

-8.8

-8.6

-8.4

-8.2

-8

-7.8

-7.6-0.3

-0.2

-0.1

0

0.1

0.2

0.3-2

-1

0

1

2

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

1000 1200 1400 1600 1800 2000

Gre

at B

arri

er R

eef

(~18

.5°S

)

Sea

wat

er δ

18O

(‰,V

PD

B)

Wan

xia

ng

cav

e (3

3.3

°N)

δ1

8O

(‰,V

PD

B)

D4

Do

ngd

ao,

SC

S (

16

.7°N

)

MG

S (

µm

)

W2

D8

So

lar

irra

dia

nce

(W/m

2)

Wet

Dry

Wet

Dry

Wet

Dry

AD


correlations between proxy records and solar activity record are dominated by the 299

low-frequency (i.e., centennial and bicentennial) variability, not the decadal variability. 300

Moreover, only parts of (not all) decadal variability in proxy records are correlated 301

with the solar activity record. Some reasons exist that could explain the disagreement 302

between the decadal variation of proxy records and solar activity records, including 303

time delays for hydrologic changes in response to solar activity forcing, spatial 304

differences of the local and regional rainfalls in response to solar variations (e.g., wet, 305

dry and no changes in different regions in response to the same solar minima) and the 306

quality of the proxy records (e.g., time resolution, error of age model). 307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328


Supplementary Table 329

Table s1: RWI values and t-test statistics calculated for the difference of two means 330

(LIA vs. MCA or Recent 150 years) for the EASM-ASM hydrologic records in Fig. 1 331

and Fig.2. In addition, we have also performed sensitivity tests to confirm the robustness of our 332

adopted RWI results but choosing slightly different start and end intervals for MCA, LIA and 333

current warm period (e.g., LIA covering AD 1400-1850 instead of the main choice of AD 334

1400-1700 adopted or MCA to be from AD 1000-1400 compared to the chosen MCA interval of 335

AD 1000-1300). We did not find any drastic change to our RWI and t-test results under such 336

perturbations. Only some slight changes were observed in the records from transition area, such as 337

N1, N3 et al. 338

339

Region Record

Number Reference

RWI, p value of the t-test (two tails), Hydrological condition

Hydrological condition between LIA

and MCA

Hydrological condition between

LIA and recent 150 years

EASM D1 39 -85%, p<0.01, Dry -153%, p<0.01, Dry

EASM D2 40 -110%, p<0.01, Dry -74%, p<0.01, Dry

EASM D3 8 -112%, p<0.01, Dry -102%, p<0.01, Dry

EASM D4 3 -145%, p<0.01, Dry -144%, p<0.01, Dry

EASM D5 7 -96%, p<0.01, Dry -90%, p<0.01, Dry

EASM N1 9 -24%, p>0.05, No apparent change -153%, p<0.01, Dry

EASM N2 41 29%, p>0.05, No apparent change 24%, p>0.05*, No apparent

change

EASM W1 42,43 121%, p<0.01, Wet 189%, p<0.01, Wet

EASM W2 5,27 156%, p<0.01, Wet 163%, p<0.01, Wet

ASM D6 47-49 -71%, p<0.01, Dry

ASM D7 50 -62%, p<0.05 (0.021), Dry

ASM D8 4 -143%, p<0.01, Dry

ASM D9 51 -92%, p<0.01, Dry

ASM D10 44,45 -92%, p<0.01, Dry -80%, p<0.01, Dry

ASM D12 10 -155%, p<0.01, Dry -178%, p<0.01, Dry

ASM D13 46 -105%, p<0.01, Dry -142%, p<0.01, Dry

ASM N3 52 87%, p>0.05, No apparent change 41%, p>0.05, No apparent

change

ASM N4 53 78%, p<0.01, Wet -138%, p<0.01, Dry

ASM W3 54 124%, p<0.01, Wet 176%, p<0.01, Wet

ASM W4 18 152%, p<0.01, Wet 142%, p<0.05 (=0.023), Wet

ASM W5 19,21 173%, p<0.01, Wet 86%, p<0.01, Wet

340

341


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