Amekawa et al. Progress in Earth and Planetary Science
https://doi.org/10.1186/s40645-021-00409-8(2021) 8:18

Progress in Earth andPlanetary Science

RESEARCH ARTICLE

Open Access

Stalagmite evidence for East Asian wintermonsoon variability and 18O-depleted
surface water in the Japan Sea during thelast glacial period
Shota Amekawa1, Kenji Kashiwagi2, Masako Hori3, Tomomi Sone4, Hirokazu Kato1, Tomoyo Okumura5,
Tsai-Luen Yu6, Chuan-Chou Shen6,7,8 and Akihiro Kano1*

Abstract
In the East Asian monsoon area, stalagmites generally record lower and higher oxygen isotope (δ18O) levels during
warm humid interglacial and cold dry glacial periods, respectively. Here, we report unusually low stalagmite δ18O
from the last glacial period (ca. 32.2–22.3 ka) in Fukugaguchi Cave, Niigata Prefecture, Japan, where a major
moisture source is the East Asian winter monsoon (EAWM) that carries vapor from the warm surface of the Japan
Sea. The δ18O profile of this stalagmite may imply millennial-scale changes, and high δ18O intervals that are related
to Dansgaard–Oeschger (D–O) interstadials. More importantly, the stalagmite exhibits low overall δ18O values; themean δ18O (− 8.87‰) is distinctly lower than the mid-Holocene mean of another stalagmite from the same cave
(4.2–8.2 ka, − 7.64‰). An interpretation assuming a more intense EAWM and greater vapor transportation during
the last glacial period, compared with the mid-Holocene, contradicts the limited inflow of the Tsushima Warm
Current into the Japan Sea because of lowered sea level. Additionally, our model calculation using δ18O data frommeteoric water indicated that the amount effect of winter meteoric water was insignificant (1.2‰/1000 mm). Low
stalagmite δ18O for the last glacial period in Fukugaguchi Cave most likely resulted from 18O-depleted surface
water, which developed in the isolated Japan Sea. The estimated amplitude of the δ18O decrease in surface water
was ~ 3‰ at most, consistent with the abnormally low values for foraminifera (by ~ 2.5‰) in sediment during thelast glacial period, shown by samples collected from the Japan Sea. This is the first terrestrial evidence of 18O
depletion in Japan Sea surface water during the last glacial period.
Keywords: Stalagmite paleoclimatelogy, East Asian winter monsoon, Last glacial period, Japan Sea, Oxygen isotope ratio

1 Introduction
High-resolution isotopic records of well-dated stalagmites have been used as paleoclimatic archives in aterrestrial setting (e.g., Cheng et al. 2016). More specifically, the oxygen isotope (δ18O) records of stalagmites
can provide important insight into the precipitation
dynamics of the Late Pleistocene and Holocene epochs* Correspondence: akano@eps.s.u-tokyo.ac.jp
1
Department of Earth and Planetary Sciences, Faculty of Science, The
University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8654, Japan
Full list of author information is available at the end of the article

and have become a standard proxy for terrestrial climatic changes at the global scale. As a prominent example, Chinese cave records demonstrate that changes
in stalagmite calcite δ18O (δ18OC) are strongly correlatedwith δ18O records from Greenland ice cores (Wanget al. 2001) and shifts in Northern Hemisphere summer
insolation on orbital timescales (Cheng et al. 2016;
Wang et al. 2008).
The link between climate and δ18OC has been mostly
attributed to variability in the δ18O values of local meteoric water. A popular interpretation is that this results© The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give
appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in this article are included in the article's Creative Commonslicence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commonslicence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

(2021) 8:18

Page 2 of 15

from the amount effect on meteoric water δ18O (δ18OW)
from the intensified East Asian summer monsoon(EASM), which controls the climate in Asia (Cheng et al.
2009; Wang et al. 2001, 2008). Furthermore, δ18OC isseemingly synchronized with climatic changes in the
North Atlantic Ocean during the late Quaternary(Cheng et al. 2016; Sun et al. 2012; Wang et al. 2001,
2008; Zhao et al. 2018). Regarding the warming transition associated with deglaciation from the last glacial
period to the mid-Holocene, the stalagmites generally
exhibit distinct reductions in δ18OC values, again ascribed to the intensification of the EASM.
The East Asian winter monsoon (EAWM) is anothermeteorological system in East Asia (Fig. 1a). The EAWM
is driven by the thermal contrast between the Asian continent and the North Pacific during winter, which blows
dry and cold northerly winds from the Siberian High
(Tada et al. 2016). The EAWM affects the climate of

East Asia (Porter and An 1995) and transports heat fromthe Northern Hemisphere to the Southern Hemisphereas it crosses the equator (Chu et al. 2017; Yamamoto
et al. 2013). EAWM variability during the late Quaternary has been reconstructed using marine sedimentcores from the Sulu Sea (de Garidel-Thoron et al. 2001),
South China Sea (Huang et al. 2011; Steinke et al. 2010,2011; Yamamoto et al. 2013), Northwestern Pacific
Ocean (Sagawa et al. 2011), and Japan Sea (Nagashima
et al. 2007, 2011), as well as from terrestrial archives(e.g., aeolian sediments from the northwestern Chinese
Loess Plateau (Sun et al. 2012) and lake sediments insouth China (Chu et al. 2017; Yancheva et al. 2007). The
δ18OC rarely reflects the intensity of the EAWM because
meteoric water from a dry EAWM makes only a small
contribution to total precipitation in East Asia (e.g., An
2000). Exceptional findings were reported in Fukugaguchi
Cave at Itoigawa in central Japan, on the coast of the Japan

120ºE

140ºE

B

130ºE

140ºE
Soya Strait

urrWarm current
Cold current
40ºN

an

n
pa

Lim

Itoigawa

Ja

40ºN

shio
ido
Oya rrentkka
Cu
HoTsugaru
Strait
40ºN

Co

Se

a

Siberian
High

ld C

100ºE

A

ent

Amekawa et al. Progress in Earth and Planetary Science

40ºN

Japan Sea
Pacific

Sanbao
Hulu

f

it o

u
Ts

a

im

sh

WM
EA

Temperature (ºC)
Monthly rainfall (mm)

25

hio

s
uro

nt

rre

Cu

30ºN

K
30ºN

120ºE

C

ns

Ho

20ºN

th

u
So

hu

Tsushima Strait

im

L
ern

20ºN

100ºE

Itoigawa

nt

re

r
Cu

130ºE

140ºE

D

20
Itoigawa(Fukugaguchi C.)

15
10

TakadaToyama5
U1427/PC3

400

L. Suigetsu

300

Ohtaki C.
L. Biwa

200

Maboroshi C.
Kiriana C.

100
0

J F M A M J J A S O N D

Fig. 1 Geographic and climatological setting of the study site, Itoigawa. a Map showing the general wind directions in the winter, the southern
limit of the EAWM, and the locations of the Itoigawa and Chinese caves. b Warm and cold currents around Japan. The Tsushima Warm Current
enters the Japan Sea through the Tsushima strait and outflows to the Northwestern Pacific Ocean through the Tsugaru and Soya straits. c
Monthly mean temperature (°C) at Itoigawa (upper) and rainfall (mm) at the Hiraiwa Precipitation Observatory (lower) during the period 1990–
2009. d Locations of caves (Maboroshi, Ohtaki, and Kiriana), lakes (Suigetsu and Biwa), a coring site (U1427/PC3), and observatory sites (Toyama
and Takada) discussed in this study

(2021) 8:18

Page 3 of 15

Sea (Sone et al. 2013, 2015), where water vapor from theJapan Sea warmed by the Tsushima Warm Current iscarried by a northwesterly of the EAWM from Siberia(Fig. 1b; Hirose and Fukudome 2006). This area is wet inwinter, and the snow/rainfall of the winter months(December–February) constitutes ~ 40% of annual
rainfall (Fig. 1c). Considering that the EAWM usually
starts in November and ends in March, the EAWM
snow/rainfall contributes a larger proportion (it falls
57% of annual rainfall during five months from November to March). Sone et al. (2013) analyzed a
Holocene stalagmite (i.e., FG01) from Fukugaguchi
Cave (Fig. 1d) and found that δ18OC variability at the
top of FG01 was strongly correlated with that of winter precipitation observed from 1924 to 2010 at
Takada (Fig. 1d). On the other hand, the δ18OC variability did not show relevance to precipitation ofother seasons (Sone et al. 2013 in their Fig. 5). The
amount effect apparent in δ18O values of winter precipitation (collected from Toyama, Fig. 1d) also implied that the δ18OC reflected winter precipitation
variability. In addition, the δ18OC profile of the entire
FG01, covering the past 10 kyr, demonstrated a trend
similar to that of EAWM variability reported by otherstudies on loess and lake sediments (Sone et al.
2013). However, the variability of the EAWM beyond
the pre-Holocene period has never been demonstrated
based on a stalagmite record. Such data may provide
insight regarding the hydroclimate during glacial
periods.
Here, we present a new δ18OC profile spanning the lastglacial period from 32.2 to 22.3 ka, obtained from another stalagmite (FG02) in Fukugaguchi Cave. A drastic
shift in oceanographic conditions occurred during thelast glacial period in the Japan Sea, the major moisturesource in the study area. The Japan Sea is currently
connected to the open ocean via four shallow straits(Fig. 1b). However, during glacial periods, the lowered
sea level largely restricted entry of the Tsushima Warm
Current. Freshwater influx from the surrounding landarea reduced surface water salinity in the Japan Sea, as
indicated by unusually low δ18O in foraminifers (Obaet al. 1991; Sagawa et al. 2018). Closing and opening of
the Japan Sea led to glacial–interglacial contrast in thecompositions and structures of core sediments recoveredfrom the Japan Sea, which are generally laminatedduring glacial and bioturbated during interglacials (e.g.,
Irino et al. 2018; Tada et al. 2018; Seki et al. 2019). The
closure of the Japan Sea may also have affected thehydrodynamics of vapor generation during glacial periods. Such changes, as well as the intensity of the
EAWM and the EASM, may lead to differences in the
δ18OC in FG02 from other cave records in Japan(Maboroshi, Ohtaki, and Kiriana; Fig. 1d), where

precipitation from the EAWM is minor. Moreover, theδ18OC profile of FG02 exhibits millennial-scale changes
that might correspond to climatic changes in the North
Pacific Ocean. In this paper, the δ18OC records from
Fukugaguchi Cave are discussed as new stalagmite evidence for the development of 18O-depleted surface waterin the Japan Sea during the last glacial period.

Amekawa et al. Progress in Earth and Planetary Science

2 Materials and methods
2.1 Study site and stalagmite sample

Fukugaguchi Cave (36° 96.5′ N, 137° 80.0′ E) is locatedin Itoigawa City, Niigata Prefecture, on the coasts ofJapanese islands along the Japan Sea (Fig. 1). Itoigawa
currently experiences some of the heaviest snowfall inJapan because of its geographic and altitudinal position,i.e., on a steep slope behind high mountains (e.g., Mt.
Asahidake, 2418 m asl). A northwesterly of the EAWM
reaches this location across the widest breadth of theJapan Sea, where the Tsushima Warm Current supplies
water vapor to the initially dry northwesterly (Fig. 1a, b).
The wet air mass then interacts with the mountainslope, causing heavy snowfalls. Therefore, the 5-month
period (November–March) under the influence of the
EAWM is generally wet in this area, accounting for 59%
of the annual precipitation in Itoigawa (Sone et al. 2013).
Our sample analyzed in this study was a 22-cm-longstalagmite (FG02; Fig. 2a) collected from Fukugaguchi
Cave in 2010. The sampling point was approximately
700 m from the cave entrance and near the location of
the Holocene sample (FG01; Sone et al. 2013, 2015),
where relative humidity (RH) is nearly 100%. FG02 has
two discontinuous surfaces at 13.0 and 198.0 mm fromthe top (hiatus in Fig. 2a). The stalagmite lacks the regular laminae (Fig. 2b–e) that may constitute annual bands.
It mainly consists of transparent calcite mass (Fig. 2b, d),although some distal parts of the stalagmite exhibit mmscale layering (Fig. 2c, e).
2.2 U–Th age measurement

The ages of FG02 were determined by U–Th dating carried out at the National Taiwan University. The methods
were described in detail by Shen et al. (2002, 2003,2012). The stalagmite was cut along its growth axis forpolishing and then drilled at nine horizons along the
growth lines. Nine 0.2–0.3-g subsamples were obtainedfor each analysis. Because of the low uranium concentration in FG02, the amount of each sample was more than
twofold greater than the amount used in ordinary U–Th
dating (approximately 0.1 g; Shen et al. 2012). These
powdered samples were dissolved with 5% nitric acidand spiked with an artificial radiometric tracer(229Th–233U–236U). An Fe3+ solution was added to thissolution to remove Ca2+ by iron co-precipitation. U and
Th were purified by anion exchange chromatography.

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

Page 4 of 15

Fig. 2 Textures and age model of FG02. a The half-cut specimen of FG-02 showing sampling transect of isotopic analysis and positions of thinsection image. Two hiatus horizons are indicated by dotted lines. b Transparent calcite at 3.5 cm from the top. c Millimeter-scale layering at 6.5
cm from the top. d Transparent calcite at 9.7 cm from the top. e Vague-layered structure at 13.5 cm from the top. f Age model: the length of thestalagmite, starting from the top, is plotted against age. Measured ages are presented with error bars of 2σ. The black line represents thesmoothed age data, while the gray-shaded region represents the error range calculated using StalAge (Scholz and Hoffmann 2011)

The isotopic signature of each purified fraction was measured with a multicollector inductively coupled plasma
mass spectrometer (Neptune; Thermo). An age–depth
model was constructed using StalAge software, by meansof a statistical algorithm based on Bayesian Monte Carlosimulation (Scholz and Hoffmann 2011).

Belemnite standard. The reproducibility of the measurements of in-house standard (N = 190) was ±0.14‰ (2SD). A typical measuring error is ±0.2‰ (2 σ). Additional details of δ18O measurement were described by
Hori et al. (2009).

2.3 Stable isotope analysis

2.4 Evaluation of the amount effect of winterprecipitation

Stable isotope analysis was performed with an isotope
ratio mass spectrometer (DeltaPlus; Thermo Finnigan)connected to an online gas separation and introduction
system (GasBench II) at Kyushu University. Subsampling
was conducted down the middle of the growth band
along the growth axis with a dental microdrill (Tas35LX; Shofu) at 0.2-mm intervals. In addition, a Hendy
test to examine the stability of δ18O values along specificgrowth bands (Hendy 1971) was performed for 8–10
subsamples at three horizons. Each ~ 0.15-mg sample
was enclosed in a 12-mL vial. Following replacementwith He gas, these subsamples were reacted with phosphoric acid for > 5 h in a 50 °C thermostat chamber.
Generated CO2 was introduced to the analysis system.
δ18O values were normalized by using an in-housestandard, which corresponded to the Vienna Pee Dee

For the Holocene stalagmite (FG01), Sone et al. (2013)concluded that the variability of δ18OC largely reflected
the intensity of winter precipitation, consistent with thenegative correlation between δ18OW and the amount ofrain containing meteoric water during winter. We quantified this amount effect by using a bootstrap methodand δ18OW data collected at Toyama, approximately 60
km southwest of the cave (Fig. 1d). The δ18OW data included 78 meteoric rain/snow events in winter months(December–February) from 2010 to 2012, which werecollected by Sone et al. (2013). A virtual set of winterprecipitation data consisted of a given number (N) of
rainfall events, which were randomly selected fromamong the 78 events. First, the range of N was set at
24–30, which reproduced the distribution of total winterprecipitation for the last 50 years at Toyama. Then, the(2021) 8:18

Page 5 of 15

total amount and weighted mean of δ18OW were calculated for each virtual set. For each of seven cases of N
(24–30), the selection of virtual sets was repeated 100
times, such that the total number in the virtual set was
700.

covariance between δ18OC and δ13C was not confirmed (R = 0.04; Fig. 4b), presumably supporting theabsence of significant isotopic non-equilibrium.

Amekawa et al. Progress in Earth and Planetary Science

3 Results
3.1 Dating result and age–depth model

U–Th dating for FG02 yielded suitable ages from nine horizons, which ranged from ca. 13 to ca. 29 ka (Table 1).
Although each age from the nine horizons exhibited relatively large uncertainty, due to the low uranium concentration (typically 6.0 ppb) and relatively high 232Th (e.g.,
3820 ppt at 9.5 mm horizon), they were generally in thecorrect stratigraphic order (Table 1). A distinctly youngerage (ca. 13 ka) was obtained from the uppermost dated
horizon (10 mm from the top; Table 1, and above theupper hiatus; Fig. 2a). An approximately 10-kyr age difference between this horizon and the next dated horizon (ca.
23 ka) at 30 mm likely signified a hiatus at an upper discontinuous surface (13.0 mm). Another hiatus was suspected at a lower discontinuous surface (198.0 mm),
although no reliable age was obtained below this surface.
The age model generated with StalAge (Scholz and
Hoffmann 2011) indicated that the middle section between the two hiatuses was formed between ca. 32.2
ka and ca. 22.3 ka. The age–depth relation shown in
Fig. 2 implies that the growth rate was fast above
130 mm (approximately 45 mm/kyr for 22–24 ka) andslow below 130 mm (approximately 7 mm/kyr for 24–
32 ka).
3.2 Stable isotope analysis

The δ18OC values of the middle section of FG02 ranged
from − 7.48‰ to − 10.68‰, with a mean value of −8.87‰. This was clearly lower than the range observedin Holocene FG01 (mainly − 8.5‰ to − 7.0‰; Sone et al.
2013, 2015). The δ18OC values of FG02 indicatedmillennial-scale changes resembling the changes in the
paleoclimatic records of the last glacial period. From
32.2 ka (i.e., the bottom) to ca. 26 ka, the δ18OC variability showed sawtooth-shaped fluctuation on a millennial
scale (Fig. 3). The fluctuation amplitude was 0.5‰–
1.0‰, clearly greater than the δ18OC measurement deviation (± 0.14‰). The upper δ18OC profile in the intervalfrom 26 to 24 ka was nearly flat around − 9‰; this wasfollowed by a positive shift to − 8‰ at 23.1 ka, which
rapidly recovered at ca. 22.8 ka (Fig. 3).
The results of Hendy tests conducted at 26-, 60-, and120-mm horizons are shown in Fig. 4a. The mean value
was − 8.43‰ at 26 mm, − 8.79‰ at 60 mm, and − 9.28‰
at 120 mm. The three horizons exhibited perturbation
within ±0.25‰, which was slightly larger than the measurement error of δ18OC (2σ < ± 0.2‰; Fig. 4a). The

3.3 Relationship between δ18O and winter precipitation at
ToyamaA weak negative correlation between the total winterprecipitation and weighted mean of δ18O was observed
upon analysis of 78 meteoric water samples during winter months (December–February) at Toyama (Fig. 5)(Sone et al. 2013). In the past 50 years (1969–2018),
395.5–994.5 mm of rain and snow (mean, 696.4 ± 135mm) fell each winter (Fig. 5a). First, we reproduced thisobserved distribution of total winter precipitation byrandom selection of a range of N (number of rain/snow
events) from among the 78 actual events. The closest
distribution was obtained with the range of N from 24
to 30 (mean, 687.9 ± 132 mm) (Fig. 5a). The calculation
was repeated 100 times for each case of N (24–30; 7cases), and the 700 virtual sets of winter precipitation
data yielded weighted δ18OC values ranging from −10.74‰ to − 7.81‰ (mean, − 9.34‰ ± 0.49‰). The precipitation amount and weighted mean (Fig. 5b) indicateda weak but significant negative correlation (R = − 0.33, p= 6 × 10–19), with a slope of − 1.2‰/1,000 mm. We use
this slope as the amount effect of modern winter precipitation in the following section.

4 Discussion
4.1 Millennial-scale changes in FG02

The FG02 stalagmite recorded millennial-scale changes according to the characteristic features in the paleoclimaticrecords during the last glacial period. Figure 6 compares
the FG02 δ18OC with the δ18O and Ca2+ concentration of aGreenland ice core (Rasmussen et al. 2014; Seierstad et al.
2014), as well as a reconstructed EAWM derived fromgrain size variation in the Chinese Loess Plateau (Sun et al.
2012), and a reconstructed EASM derived from stalagmites
in Sanbao and Hulu Caves in China (Wang et al. 2001) andstalagmites in Kiriana Cave on the Pacific Ocean side ofJapan (Mori et al. 2018). The FG02 stalagmite shows
millennial-scale changes in δ18OC. Because the low uranium content of FG02 yields U–Th ages with relatively large
uncertainty (Table 1), two possible relationships exist between the δ18OC and Dansgaard–Oeschger (D–O) events(cases 1 and 2; Fig. 6). In order to determine which case istrue, stalagmite samples with small uncertainty of U-Th
ages are needed.
In case 1, the δ18OC values of FG02 are presumed tobe heavier during the D–O interstadials. Three positive
δ18OC excursions, at 23.1, 27.3, and 28.7 ka, are correlated with D–O events 2, 3, and 4, respectively (Fig. 6c).
Another positive excursion around 30.8 ka is also recognized in the Greenland ice core and Chinese loess0.28800.29440.33470.28480.27490.2364

80.7

93.2

120.7

148.5

159.5

178.7

5.80 ± 0.04 669

6.32 ± 0.04 233

6.07 ± 0.03 431

6.08 ± 0.03 754

6.32 ± 0.03 293

7.78 ± 0.02 446

8.21 ± 0.01 543

± 4.1

± 2.6

± 2.8

± 4.2

± 2.4

± 2.6

± 2.9

484.4

494.0

483.1

430.8

443.8

436.7

407.2

± 10.9± 11.4

± 8.9

± 8.1

± 7.1

± 3.9

± 3.1

± 2.2

± 2.4

0.37330.33490.31590.29930.29480.27780.28890.29570.2987± 0.0064± 0.0032± 0.0048± 0.0053± 0.0027± 0.0030± 0.0039± 0.0056± 0.0129

53.5

149.9

73.4

39.8

105.1

80.0

72.1

36.5

7.8

± 0.9

± 2.0

± 1.2

± 0.7

± 1.2

± 1.0

± 1.0

± 0.7

± 0.3

31127

27329

25812

25323

24642

23213

24810

25126

26165

± 660

± 381

± 472

± 524

± 282

± 283

± 377

± 530

± 1265

29111

26691

24567

23053

23809

22173

23585

22665

13537

± 1202

± 492

± 779

± 1255

± 501

± 593

± 720

± 1349± 6838

525.9

532.8

517.8

459.8

474.7

465.0

435.2

452.0

402.8

± 12.0± 12.4

± 9.6

± 8.8

± 7.6

± 4.2

± 3.4

± 2.9

± 8.0

b

234U = ([234 U/238 U] activity−1) × 1000.
234Uinitial corrected was calculated based on 230Th age (T), i.e., 234Uinitial = 234Umeasured × e 234*T, and T is corrected age
c[230Th/238 U]activity = 1 − e−230 T + (234Umeasured/1000)[230/(230–234)](1 − e − (230–234) T), where T is the age. Decay constants are 9.1577 × 10−6 year-1 for 230Th, 2.8263 × 10–6 year-1 for 234 U (Cheng et al.
2013), and 1.55125 × 10–10 year-1 for 238 U (Jaffey et al. 1971)d
The degree of detrital 230Th contamination is indicated by the [230Th/232Th] atomic ratio instead of the activity ratioe
Age corrections were calculated using an estimated atomic 230Th/232Th ratio of 4 ± 2 ppm

a0.2635

61.0

423.9

0.241629.0

9.33 ± 0.01 1247 ± 4.2

6.01 ± 0.00 3818 ± 13.4 387.7

0.2257

δ234U (measured)a [230Th/238U] (activity)c [230Th/232Th] (ppm)d Age (uncorrected) Age (corrected)c,e δ234Uinitial (corrected)b

9.5

Th (ppt)

232

238

Horizon (mm) Weight (g)U (ppb)Table 1 Uranium and thorium isotopic compositions and 230Th ages (before 1950 AD) for subsamples of stalagmite FG02 by MC-ICP-MS

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18
Page 6 of 15

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

Page 7 of 15

Fig. 3 δ18OC age profile of FG02. Note the inverted vertical axis. Dating results are shown at the top; open circles for the corrected 230Th ages
(Table 1), solid circles, and bars for the smoothed ages and the error ranges (Fig. 2), respectively

Fig. 4 Isotopic behaviors of FG02. a Hendy test results for δ18OC atthree growth lines, 26 mm (red), 60 mm (black), and 120 mm (blue)
from the top. Subsamples were collected at 1-mm intervals from thecentral growth axis. b Covariance between δ18O and δ13C

(Fig. 6) and could correspond to the Greenland Interstadial 5.1 (at 30.84 ka) described by Rasmussen et al.
(2014). Furthermore, Sone et al. (2013, 2015) concluded that the variability of δ18OC in Holocene FG01
reflects the amount of winter precipitation. According
to this interpretation, the millennial-scale positive excursions of δ18OC in FG02 (with an amplitude of
0.5‰–1‰) should have been associated with less winter precipitation and the EAWM during short-term
interstadials in Greenland and the North Atlantic
Ocean. There might be a linkage between the D–O
events and the weakened EAWM, which enriched 18Oof meteoric water and FG02.
The δ18OC values of FG02 are presumed to be lighter
during the D–O interstadials in case 2. In this scenario,
four low-δ18OC intervals at 22.4, 27.6, 29.0, and 31.4 ka
correspond to D–O events 2, 3, 4, and 5.1, respectively(Fig. 6c). This scenario fully accords with the stalagmites
from China (e.g., Wang et al. 2008), whereby the amounteffect due to the intensified EASM reduced δ18OC values
during D–O interstadials. However, this is inconsistent
with the findings of Sone et al. (2013), suggesting thatthe variability of the EASM did not strongly affect thestalagmite δ18OC. In addition, the δ18OC reduction during these D–O interstadials is unclear even in Kiriana
Cave on the Pacific Ocean side of the Japanese islands(Fig. 6f; Mori et al. 2018), where the majority of meteoric
water originated from the EASM.
The relationship in case 1 is likely to be more plausible
than the relationship in case 2; the δ18OC values of FG02
increased during the D–O events, which contrasts withthe findings in Chinese caves. Stalagmite FG02 exhibits
an overall decreasing trend of δ18OC (Fig. 6c), which also
contrasts with the Chinese stalagmites (Fig. 6e) and findings in Kiriana Cave (Fig. 6f). The case 1 scenario is consistent with the overall trend of δ18OC, as well as theAmekawa et al. Progress in Earth and Planetary Science(2021) 8:18

Page 8 of 15

Fig. 5 Model calculation of the amount effect of winterprecipitation based on the δ18OW data of 78 meteoric water samples
collected during winter months (December to February) at Toyama(Sone et al. 2013). a Comparison of the frequency of winterprecipitation based on 50 years of data from the Toyama weather
observatory (1969 to 2018; blue bar) and 700 virtual model
calculation sets (red plots). Resampling 24–30 rain/snow events best
reproduced the observed frequency (mean and standard deviation)of cumulative winter precipitation. b Cross plot of winterprecipitation and δ18OW in meteoric water. A weak but clear
correlation is evident between these two variances

conclusions of Sone et al. (2013, 2015), whereby the variability of δ18OC reflects the amount of winter precipitation. However, considering the calculated amount effectof the modern meteoric water (− 1.2‰/1000 mm; Fig. 5),
a 0.5‰ to 1‰ enrichment of 18OC was only partly compensated by the weakened winter precipitation. A morerobust amount effect during the glacial period could be
the cause of high δ18OC in FG02 during the D–O events.
Alternatively, high δ18OC values during the D–O events

Fig. 6 Comparison of FG02 δ18O data and climate interpretation
with other paleoclimatic studies in the period 20–25 ka. a Greenland
ice core δ18O (Seierstad et al. 2014) and b Ca2+ (Rasmussen et al.
2014). c FG02 δ18O data (this study). Climate interpretation isaccording to case 1. d Grain size variation of quartz in loesssediments from the Chinese Loess Plateau (Sun et al. 2012). e δ18O
variability in Hulu Cave (south China; Wang et al. 2001). f δ18O
variability in Kiriana Cave (Mie Prefecture, Japan; Mori et al. 2018)

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

Page 9 of 15

were also associated with other factors, such as theevaporation of water in the soil or cave, which increases both δ18OW and δ18OC. Our data do not ruleout an evaporation effect during water infiltrationfrom the soil. However, any such evaporation effectin the cave was presumably unimportant at the sampling site deep in the cave (700 m from the entrance),
because it only appears to be robust where RH is unstable (Deininger et al. 2012).
4.2 Factors responsible for low δ18OC in glacial FG02

Figure 7 compares the δ18OC records of the last glacial
period (FG02) and the Holocene (FG01) (Sone et al.
2013) with those from three other Japanese stalagmites
in Maboroshi Cave in Hiroshima Prefecture (Hiro-1;
Hori et al. 2014; Shen et al. 2010; Kato et al. 2021), andKiriana and Ohtaki Caves in Mie and Gifu Prefectures, respectively (KA03 and OT02; Mori et al. 2018) (see Fig. 1dfor locations). The stalagmite records from Fukugaguchi
Cave indicate lower δ18OC values during the last glacial
period (FG02) compared with Holocene values (FG01;
Sone et al. 2013). This is a unique feature of Fukugaguchi
Cave; such variability is not seen in other Japanese andChinese caves where the EASM is the major source of meteoric water. The Hiro-1, KA03, and OT02 stalagmites exhibit similar δ18OC variability, with higher values during
the last glacial period and lower values in the Holocene,consistent with the Chinese records (e.g., Sanbao and
Hulu Caves; Wang et al. 2001, 2008). Comparing our results from Fukugaguchi Cave with the KA03 records from
Kiriana Cave that span the entire FG02, a substantial difference (> 3‰) was apparent in the mid-Holocene value
minus the glacial period value (Δ18OH-G; + 1.23‰ in
Fukugaguchi and − 1.81‰ in Kiriana Cave; Table 2). The
negative Δ18OH-G was used to explain the weakened
EASM during the glacial period in Chinese records (e.g.,
Wang et al. 2001). Mori et al. (2018) challenged the notionof an effect of EASM intensity on δ18OC, suggesting thatthe variability of δ18OC was largely controlled by air
temperature and δ18O in seawater, which constituted the
major moisture source on the Pacific Ocean side of theJapanese islands. Thus, the Δ18OH-G value of − 1.81‰ at
Kiriana Cave can be explained by the lower glacial periodtemperature that caused an increase in fractionation δ18O
and by 18O-enriched glacial period seawater that caused
an increase in moisture δ18O. The importance of thetemperature effect on the stalagmite δ18OC was also
demonstrated for Hiro-1 in Maboroshi Cave by covariation of δ18OC and carbonate clumped isotope(Δ47; Kato et al. 2021).
The EASM intensity, air temperature, and seawater
δ18O from the Pacific Ocean are important factors controlling δ18OC in East Asia. However, none of these factors are considered responsible for the positive (+Fig. 7 δ18O variability in Japanese caves during the Holocene andlast glacial period. a Fukugaguchi Cave in Niigata Prefecture. The
Holocene profile is based on FG01 data (Sone et al. 2013). b
Maboroshi Cave in Hiroshima Prefecture (Hori et al. 2014; Shen et al.
2010). c Ohtaki Cave in Gifu Prefecture (Mori et al. 2018). d Kiriana
Cave in Mie Prefecture (Mori et al. 2018)1.23‰) Δ18OH-G observed at Fukugaguchi Cave. The
EASM is a secondary moisture source for Fukugaguchi
Cave (Sone et al. 2013, 2015), and EASM weakening islikely to cause negative Δ18OH-G. Alkenone-based reconstruction studies for nearshore sediments from the Japan
Sea suggested that the sea surface temperature during
17–32 ka was 1–2 °C higher than in the mid-Holocene(Fujine et al. 2006, 2009; Ishiwatari et al. 2001; Xinget al. 2011). Ishiwatari et al. (2001) ascribed these enigmatic results in the Japan Sea to the retention of solar
energy on the surface water layer that was stratified with

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

Page 10 of 15

Table 2 Mean δ18O (vs VPDB) during mid-Holocene and the last glacial period recorded in Japanese and Chinese caves
Middle Holocene

Last glacialδ Oavr (‰)

Interval (ka)

δ Oavr (‰)

Interval (ka)− 7.64

4.2–8.2− 8.87

22–33

18

Fukugaguchi

18

Δ18OH-G(‰)

Reference+ 1.23This study, Sone et al. (2013)

Maboroshi− 7.29

4.5–8.2− 6.16

16.0–18.2− 1.13

Hori et al. (2013)

Kiriana− 5.94

4.3–8.2− 4.1322–33− 1.81Mori et al. (2018)

Ohtaki− 7.37

4.2–8.2− 6.72

34.8–36− 0.65Mori et al. (2018)

Sambo/Hulua− 10.43

4.2–8.2− 8.1822–33− 2.25

Wang et al. (2001, 2008)

Collected more positive (+ 1.9 ‰) Hulu value against Sambo value (Wang et al. 2008)aheavier, deeper layers. Other studies have suggested thatdiminished salinity during the last glacial period might
have led to a change in alkenone production, resulting
in a higher reconstructed temperature (Fujine et al.
2006, 2009). Although this interpretation cannot be
ruled out, the air temperature on the land was generally
lower during the glacial period than the interglacial
period, as indicated by pollen assemblages from Lakes
Suigetsu and Biwa (Nakagawa et al. 2006, 2008). Similar
to other Japanese cave sites, the lower air temperatureduring the last glacial period would increase δ18OC, thus
making Δ18OH-G negative.
With respect to the Holocene δ18OC variability at
Fukugaguchi Cave (FG01), Sone et al. (2013, 2015) considered the intensity of the EAWM and winter precipitation to be dominant factors. The correlation between
δ18OC and winter (December–February) precipitation at
Takada (Fig. 1d) is evident in high-resolution δ18OC analysis of the uppermost FG01, with a 1‰ difference between the dry (1000 mm/3 months) winters in the late
2000s and wet (1500 mm/3 months) winters in the early
1940s at Itoigawa (Sone et al. 2013). Additionally, ouranalysis of data from Toyama, which is a drier area, revealed a negative correlation of δ18OW with the amountof precipitation (slope of − 1.2‰/1,000 mm (Fig. 5b)). In
this scenario, a stronger EAWM during the last glacial
period (Huang et al. 2011; Steinke et al. 2010; Tian et al.
2010) substantially increased winter precipitation (thusdecreasing δ18OW) and generated an approximately 3‰
difference in Δ18OH-G between the Japan Sea side (+1.23‰ at Fukugaguchi Cave) and the Pacific Ocean sideof the islands (− 1.81‰ at Kiriana Cave; Table 2). Whenthe slope of − 1.2‰/1000 mm is regarded as the amounteffect of the winter precipitation, the ~ 3‰ difference requires 2500 mm of winter precipitation during the glacial period, which is more than fourfold greater than thepresent amount of winter precipitation at Toyama.
However, such a large amount of winter precipitationis considered unrealistic because the pollen records
from Lakes Suigetsu (Nakagawa et al. 2006) and Biwa
(Hayashi et al. 2010) suggest drier winter conditions
during the same period. Furthermore, Schlolaut et al.
(2014) suggested that the winter monsoon on theJapan Sea coast had less moisture during the glacial
period because of the limited inflow of the Tsushima
Warm Current.
If conditions on the sea surface were drier, the enhanced
fractionation from water to vapor could generate lower
δ18O in both water vapor and stalagmites (Lachniet 2009).
The effect of RH on the δ18O in water vapor has been estimated in several studies; a 10% reduction in RH was posited to decrease the vapor δ18O by 1.3‰ (Gonfiantini1986) and, in another study, by 0.6‰ (Merlivat and Jouzel1979). Considering these contrasting estimates, the ~ 3‰
difference corresponds to a 25–50% decrease in RH on
the Japan Sea side, whereas the RH has remained stableon the Pacific Ocean side. However, this scenario might
reduce winter precipitation, causing the meteoric water at
Itoigawa to be dominated by summer precipitation that ismore 18O-rich than winter precipitation (Sone et al. 2013).
Therefore, the RH effect is unlikely to be equivalent to an
approximately 3‰ difference.
A factor likely to be important in the positive Δ18OH-G
at Fukugaguchi Cave is the change in δ18Osw on the surface of the Japan Sea (i.e., the dominant vapor source forthe cave) (Sone et al. 2013). Currently, δ18OSW is comparable between the Japan Sea and the Pacific Ocean.
The Japan Sea is a landlocked marginal sea that connectswith the East China Sea and the Pacific Ocean throughfour narrow straits (Fig. 1b). Because all four straits areshallow, water exchange (e.g., inflow of the Tsushima
Warm Current) was largely limited during the last glacial maximum when sea level was reduced by ~ 130 m(Matsui et al. 1998). Under this restricted condition, thesurface seawater may have been diluted by riverine waterfrom the Russian mainland and Japanese islands. Sediment cores from the Japan Sea indicate strong stratification during the last glacial period (Oba et al. 1991;
Sagawa et al. 2018), which consisted of oxygen-deficient
deep water and low-salinity surface water (Tada et al.
1992, 1999). 18O depletion of the Japan Sea surface was
first proposed because of the unusually low δ18O in
planktonic foraminifera during the last glacial period, recorded in sediment cores recovered from a depth of 935
m at Oki Ridge (Oba et al. 1991) and 800–750 m offshore of Akita (Okumura et al. 1996). By using δ18O

(2021) 8:18

Page 11 of 15

records of planktonic foraminifera (Globigerina umbilicate; Oba et al. 1995) and assuming δ18OW in the modern freshwater inflow to the Japan Sea (–7.6‰), Matsui
et al. (1998) estimated that the δ18OW in the Japan Sea
surface water fell to 20‰ during the last glacial maximum. This drastic decrease in salinity is conceivable if
the significant sea-level fall during the last glacial maximum led to reduced seawater inflow through the Tsushima Strait (Matsui et al. 1998). The development of
the 18O-depleted water mass during the last glacial
period was recently confirmed by higher-resolution dataof foraminifera δ18O obtained from marine sediments
drilled at a shallower depth (330 m at IODP site U1427/
PC3; Sagawa et al. 2018). At this site, both benthic(Uvigerina spp. and Cassidulina spp.) and planktonic
foraminifera (Globigerina bulloides) began to exhibit
decreasing δ18O from ca. 32 ka to the last glacial
maximum, then showed increasing δ18O at ca. 12 ka(Fig. 8; Sagawa et al. 2018). The amplitude of thisnegative anomaly, compared with the Pacific Ocean
standard (Lisiecki and Stern 2016), is approximately

2.5‰ and has been attributed to decreased δ18OSW
on the surface of the Japan Sea (Sagawa et al. 2018).
Because the surface water of the Japan Sea is the
major moisture source for the Fukugaguchi Cave, theanomalous 18O depletion could have reduced theδ18O in meteoric water and stalagmites. Considering
the 2.5‰ depletion of δ18OSW at the coring site (330m depth), greater depletion was suspected at the sea
surface. This might be the dominant factor driving
the 3‰ difference of Δ18OH-G. The δ18OC record
from FG02 represents the first terrestrial data supporting seawater stratification and 18O depletion during the glacial period in the Japan Sea. Furthermore,
it implies stronger stratification in an earlier stage ofthe last glacial period compared with previous findings. The FG02 δ18OC values were significantly lower
at 32.2 ka, indicating that the 18O-depleted surface
water mass had existed prior to 32.2 ka.
The magnitude of the salinity reduction at the sea surface can be estimated using the δ18OW in freshwater entering the Japan Sea from the surrounding land area.

Amekawa et al. Progress in Earth and Planetary ScienceFig. 8 Isotopic evidence of 18O depletion in the Japan Sea during the last glacial period. a δ18O in stalagmites from Fukugaguchi Cave (FG01,
Sone et al. 2013; FG02, this study). b Benthic foraminifera δ18O from a coring site at 330 m depth in the Japan Sea (Sagawa et al. 2018) andNorthwestern Pacific Ocean (Lisiecki and Stern 2016). Both sets of isotopic data incorporate variability in water δ18OW and temperature(2021) 8:18

Page 12 of 15

There are only two Global Networks of Isotopes inPrecipitation sites in coastal areas of the Japan Sea:
Pohang in South Korea and Terney in Russia. Thesesites recorded weighted mean meteoric water δ18O
(δ18OMW) values of − 7.78‰ in the period 1961–1976
and − 9.09‰ in the period 1996–2000, respectively(http://www-naweb.iaea.org/napc/ih/IHS_resources_
gnip.html). Considering these data and the weighted
mean δ18OMW at Toyama (− 9.71‰; Sone et al. 2013),
the modern mean δ18OMW entering the Japan Sea isestimated to be approximately − 9‰. Here, we define
the proportion of freshwater (fMW) in the Japan Sea
surface water mass during the glacial period, as well
as isotopic values in freshwater (δ18OMW), seawater(δ18OSW), and the Japan Sea surface (δ18OJS), as
shown below.

Both marine and stalagmite δ18O showed minimum
values during sapropel events (i.e., humid intervals ininterglacial period marine isotope stages 5 and 7), whichdeveloped under enhanced low-latitude hydrological activity. Currently, the δ18OSW in the eastern Mediterranean is+ 1.6‰ (Pierre 1999), although this has been reduced byadditional meteoric water during humid periods (Kallel
et al. 1997). While Bar-Matthews et al. (2003) partly ascribed the low δ18OC values of the stalagmites to theamount effect observed in the area, the reduction of
δ18OSW was also an essential factor involved in the low
δ18OC. Moisture source δ18OW is an essential factor governing stalagmite δ18OC.

Amekawa et al. Progress in Earth and Planetary Scienceδ 18 OJS ¼ f MW δ 18 OMW þ ð1 − f MW Þδ 18 OSW
Assuming that δ18OSW and δ18OMW were + 1‰
(Schrag et al. 2002) and − 9‰, respectively, a 2.5–3.0‰
reduction in the Japan Sea surface water (δ18OJS = − 1.5
to − 2.0‰) indicates fMW of 0.25–0.3. Assuming glacial
period ocean water salinity of 35, the Japan Sea surface
salinity ranged from 24.5 to 26.3. This is in the lower
part of the salinity range (24.0–32.5) estimated for 22–
32 ka by Matsui et al. (1998); their estimate was basedon δ18O in planktic foraminifers (Globigerina umbilicata), while ours was based on δ18O in the stalagmite. In
the closed Japan Sea during the glacial period, the salinity at the sea surface, where vapor is generated, wasprobably lower than the salinity at the foraminifer habitat depth. In addition to freshwater inflow, sea ice production in the Northern Japan Sea may have contributed
to 18O-depletion of the surface water, because frozen
water becomes relatively enriched with 18O. Based on
the occurrence of dropstones and ice-rafted debris in
sediment cores, Ikehara (2003) reconstructed that thesea ice in the northern Japan Sea approached the southern end of Hokkaido during the last glacial maximum.
However, ice melting during summer releases 18Oenriched water, and the effect of sea ice development on
δ18OSW is not sustainable. Thus, seasonal waxing andwaning of sea ice were unlikely to cause a marked reduction in δ18OSW. In addition, oxygen isotopic enrichmentfrom water to ice is only ~ 3‰ (O’Neil 1968). Sustainable freshwater influx of − 9‰ was presumably a major
factor in 18O depletion in the Japan Sea surface water.
A similar linkage between marine and δ18OC records
was reported in the eastern Mediterranean (Bar-Matthews
et al. 2003), where δ18OSW is sensitive to climatic conditions. Two stalagmite records in Israel extending to 250 ka
are consistent with the δ18OC in Globigerinoides ruber inthe eastern Mediterranean (Fontugne and Calvert 1992).

5 Conclusions
Stalagmite FG02 during the last glacial period (32.3–
22.3 ka) in Fukugaguchi Cave on the Japan Sea side of
the Japanese islands shows unique δ18OC trends,
which have not been previously described in othercaves in East Asia. Due to the relatively large uncertainty of U–Th ages, we examined two possible relationships (Fig. 6). The scenario in case 2 contrasts
with the findings of a previous Japanese cave study,
suggesting that EASM variability did not generate
clear δ18OC peaks during D–O interstadials. According to the scenario in case 1, four positive excursionsof the δ18OC profile probably correspond to three D–
O events and one interval of high δ18O in theGreenland ice sheet (Fig. 6). We considered that case
1 correlation was more likely. An important finding of
this study was that the glacial FG02 had distinctively
lower δ18OC than the Holocene stalagmite from thesame cave (FG01). Its mean value (− 8.87‰) is 1.23‰
lower than the mid-Holocene mean value (4.2–8.2 ka,− 7.64‰; Sone et al. 2013). This feature is unique tothe Fukugaguchi Cave, i.e., is inconsistent with the
δ18OC records from other Japanese and Chinese caves(Fig. 7). The factor making the largest contribution to
reduced δ18OC in FG02 was presumably the development of low-salinity water in the semi-isolated Japan
Sea, consistent with foraminifera δ18O findings (Obaet al. 1991; Sagawa et al. 2018). The amount effect of
the intensified EAWM was a potential factor in the seduction in δ18OC in FG02. However, our model calculation based on δ18OW at Toyama indicated that theamount effect of winter precipitation (1.2‰/1000 mm;
Fig. 5) was insufficient to explain the observed 2.5–
3.0‰ depletion. In addition, the generation of water
vapor and winter precipitation likely decreased during thelast glacial period due to the blocking of the Tsushima
Warm Current. Our stalagmite record provides insight regarding 18O depletion and salinity in the Japan Sea surface
water during the last glacial period.

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

6 Supplementary Information
The online version contains supplementary material available at https://doi.
org/10.1186/s40645-021-00409-8.
Additional file 1.
Abbreviations
D–O: Dansgaard–Oeschger; EASM: East Asian summer monsoon; EAWM: East
Asian winter monsoon
Acknowledgements
We are grateful to Norio Iyota and Yoichi Kamikawa of the Taiheiyo Cement
Co. for kindly accepting our project and allowing our research in the
Fukugaguchi Cave in the limestone mine. We obtained weather data fromthe website of the Japan Meteorological Agency (http://www.jma.go.jp/) andδ18Ow data from Global Network of Isotopes in Precipitation (http://wwwnaweb.iaea.org/napc/ih/IHS_resources_gnip.html). We would like to thankEnago and Textcheck for the English language review.
Authors’ contributions
AK proposed the topic, conceived and designed the study, and supervised
SA. KK, TO, and AK obtained the material. SA, MH, TS, HK, TLY, and CCS
carried out the experimental work. SA 440 and AK analyzed the data andhelped in their interpretation. SA and AK wrote the manuscript of this study
with contributions from KK, MH, TLY, and CCS. The authors read andapproved the final manuscript.
Funding
This study was financially supported by the JSPS KAKENHI Grant Number
JP18J13186 to SA, JP16H02235, and 20H00191 to AK. We are also thankful forthe financial support provided by grants from the Science Vanguard
Research Program of the Ministry of Science and Technology (MOST) (1072119-M-002-051, 108-2119-M-002-012), the National Taiwan University (109L8926), and the Higher Education Sprout Project of the Ministry of Education,
Taiwan ROC (108 L901001) to CCS.
Availability of data and materials
The dataset supporting the conclusions of this article is included within thearticle and its additional file.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Earth and Planetary Sciences, Faculty of Science, The
University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8654, Japan.
2
Department of Environmental Biology and Chemistry, Faculty of Science,
University of Toyama, 3109 Gofuku, Toyama 930-8555, Japan. 3Division of
Natural Sciences, Osaka Kyoiku University, 4-698-1, Asahigaoka, Kasiwara City,
Osaka 582-8582, Japan. 4Marine Works Japan LTD., 3-54-1, Oppamahigashi,
Yokosuka 237-0063, Japan. 5Center for Advanced Marine Core Research,
Kochi University, 200 Monobe Otsu, Nankoku, Kochi 783-8502, Japan. 6Centerfor High-precision Mass Spectrometry and Environment Change Laboratory(HISPEC), Department of Geosciences, National Taiwan University, No. 1,
Section 4, Roosevelt Rd, Taipei 10617, Taiwan, ROC. 7Global Change ResearchCenter, National Taiwan University, No. 1, Section 4, Roosevelt Rd, Taipei
10617, Taiwan, ROC. 8Research Center for Future Earth, National Taiwan
University, No. 1, Section 4, Roosevelt Rd, Taipei 10617, Taiwan, ROC.
Received: 28 October 2020 Accepted: 21 January 2021

References
An Z (2000) The history and variability of the East Asian paleomonsoon climate.
Quat Sci Rev 19:171–187
Bar-Matthews M, Ayalon A, Gilmour M, Matthews A, Hawkesworth CJ (2003) Sea–land
oxygen isotopic relationships from planktonic foraminifera and speleothems in the
Eastern Mediterranean region and their implication for paleorainfall during
interglacial intervals. Geochim Cosmochim Acta 67:3181–3199

Page 13 of 15

Cheng H, Edwards RL, Broecker WS, Denton GH, Kong X, Wang Y, Zhang R, Wang
X (2009) Ice age terminations. Science 326:248–252
Cheng H, Edwards RL, Shen CC, Polyak VJ, Asmerom Y, Woodhead J, Hellstrom J,
Wang Y, Kong X, Spötl C, Wang X, Alexander EC (2013) Improvements in
230
Th dating, 230Th and 234U half-life values, and U-Th isotopic measurements
by multi-collector inductively coupled plasma mass spectrometry. Earth
Planet Sci Lett 371:82–91
Cheng H, Edwards RL, Sinha A, Spötl C, Yi L, Chen S, Kelly M, Kathayat G, Wang X,
Li X, Kong X, Wang Y, Ning Y, Zhang H (2016) The Asian monsoon over the
past 640,000 years and ice age terminations. Nature 534:640–646
Chu G, Sun Q, Zhu Q, Shan Y, Shang W, Ling Y, Su Y, Xie M, Wang X, Liu J (2017)
The role of the Asian winter monsoon in the rapid propagation of abrupt
climate changes during the last deglaciation. Quat Sci Rev 177:120–129
de Garidel-Thoron T, Beaufort L, Linsley BK, Dannenmann S (2001) Millennial-scale
dynamics of the East Asian winter monsoon during the last 200,000 years.
Paleoceanogr 16:491–502
Deininger M, Fohlmeister J, Scholz D, Mangini A (2012) Isotope disequilibrium
effects: the influence of evaporation and ventilation effects on the carbon
and oxygen isotope composition of speleothems–A model approach.
Geochim Cosmochim Acta 96:57–79
Fontugne MR, Calvert SE (1992) Late Pleistocene variability of the carbon isotopic
composition of organic matter in the eastern mediterranean: monitor of changes
in carbon sources and atmospheric CO2 concentrations. Paleoceanogr 7:1–20
Fujine K, Yamamoto M, Tada R, Kido Y (2006) A salinity-related occurrence of anovel alkenone and alkenoate in Late Pleistocene sediments from the Japan
Sea. Org Geochem 37:1074–1084
Fujine K, Tada R, Yamamoto M (2009) Paleotemperature response to monsoon
activity in the Japan Sea during the last 160 kyr. Palaeogeogr Palaeoclimatol
Palaeoecol 280:350–360
Gonfiantini R (1986) Environmental isotopes in lake studies. In: Fritz P, Fontes JC(eds) Handbook of Environmental Geochemistry, vol 2. Elsevier, Amsterdam,
pp 113–168
Hayashi R, Takahara H, Hayashida A, Takemura K (2010) Millennial-scale
vegetation changes during the last 40,000 yr based on a pollen record from
Lake Biwa, Japan. Quat Res 74:91–99
Hendy CH (1971) The isotopic geochemistry of speleothems-I. The calculation of
the effects of different modes of formation on the isotopic composition of
speleothems and their applicability as palaeoclimatic indicators. Geochim
Cosmochim Acta 35:801–824
Hirose N, Fukudome K-I (2006) Monitoring the Tsushima warm current improves
seasonal prediction of the regional snowfall. Sci Online Lett Atmos 2:61–63
Hori M, Kawai T, Matsuoka J, Kano A (2009) Intra-annual perturbation of stable
isotopes in tufas: effects of hydrological processes. Geochim Cosmochim
Acta 73:1684–1695
Hori M, Ishikawa T, Nagaishi K, Lin K, Wang BS, You CF, Shen CC, Kano A (2013)
Prior calcite precipitation and source mixing process influence Sr/Ca, Ba/Caand 87Sr/86Sr of a stalagmite developed in southwestern Japan during 18.0-4.
5 ka. Chem Geol 347:190–198
Hori M, Ishikawa T, Nagaishi K, You CF, Huang KF, Shen CC, Kano A (2014) Rare
earth elements in a stalagmite from southwestern Japan: a potential proxyfor chemical weathering. Geochem J 48:73–84
Huang E, Tian J, Steinke S (2011) Millennial-scale dynamics of the winter cold
tongue in the southern South China Sea over the past 26 ka and the East
Asian winter monsoon. Quat Res 75:196–204
Ikehara K (2003) Late Quaternary seasonal sea-ice history of the northeasternJapan Sea. J Oceanogr 59:585–593
Irino T, Tada R, Ikehara K, Sagawa T, Karasuda A, Kurokawa S, Seki A, Lu S (2018)
Construction of perfectly continuous records of physical properties for darklight sediment sequences collected from the Japan Sea during Integrated
Ocean Drilling Program Expedition 346 and their potential utilities as
paleoceanographic studies. Prog Earth Planet Sci 5:23
Ishiwatari R, Houtatsu M, Okada H (2001) Alkenone-sea surface temperatures in
the Japan Sea over the past 36 kyr: Warm temperatures at the last glacial
maximum. Org Geochem 32:57–67
Jaffey AH, Flynn KF, Glendenin LE, Bentley WC, Essling AM (1971) Precision measurementof half-lives and specific activities of 235U and 238U. Phys Rev C 4:1889
Kallel N, Paterne M, Duplessy JC, Vergnaud-Grazzini C, Pujol C, Labeyrie L, Arnold
M, Fontugne M, Pierre C (1997) Enhanced rainfall in the Mediterranean
region during the last Sapropel Event. Oceanolica Acta 20:697–712
Kato H, Amekawa S, Hori M, Shen CC, Kuwahara Y, Senda R, Kano A (2021)
Influences of temperature and the meteoric water δ18O value on a

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

stalagmite record in the last deglacial to middle Holocene period fromsouthwestern Japan. Quat Sci Rev 53:166746
Lachniet MS (2009) Climatic and environmental controls on speleothem oxygenisotope values. Quat Sci Rev 28:412–432
Lisiecki LE, Stern JV (2016) Regional and global benthic δ18O stacks for the lastglacial cycle. Paleoceanography 31:1368–1394
Matsui H, Tafa R, Oba T (1998) Low-salinity isolation event in the Japan Sea inresoponse to eustatic sea-level drop during LGM: reconstruction based on
salinity-balance model. Quat Res (Daiyonkikenkyu) 37:221–233
Merlivat L, Jouzel J (1979) Global climatic interpretation of the deuterium-oxygen
16 relationship for precipitation. J Geophys Res: Ocea 84:5029–5033
Mori T, Kashiwagi K, Amekawa S, Kato H, Okumura T, Takashima C, Wu CC,
Shen CC, Quade J, Kano A (2018) Temperature and seawater isotopic
controls on two stalagmite records since 83 ka from maritime Japan.
Quat Sci Rev 192:47–58
Nagashima K, Tada R, Matsui H, Irino T, Tani A, Toyoda S (2007) Orbital- andmillennial-scale variations in Asian dust transport path to the Japan Sea.
Palaeogeogr Palaeoclimatol Palaeoecol 247:144–161
Nagashima K, Tada R, Tani A, Sun Y, Isozaki Y, Toyoda S, Hasegawa H (2011)
Millennial-scale oscillations of the westerly jet path during the last glacial
period. J Asian Earth Sci 40:1214–1220
Nakagawa T, Tarasov PE, Kitagawa H, Yasuda Y, Gotanda K (2006) Seasonallyspecific responses of the East Asian monsoon to deglacial climate changes.
Geology 34:521–524
Nakagawa T, Okuda M, Yonenobu H, Miyoshi N, Fujiki T, Gotanda K, Tarasov
PE, Morita Y, Takemura K, Horie S (2008) Regulation of the monsoon
climate by two different orbital rhythms and forcing mechanisms.
Geology 36:491–494
Oba T, Kato M, Kitazato H, Koizumi I, Omura A, Sakai T, Takayama T (1991)
Paleoenvironmental changes in the Japan Sea during the last 85,000 years.
Paleoceanography 6:499–518
Oba T, Murayama M, Matsumoto E, Nakamura T (1995) AMS-14C ages ofJapan Sea cores from the Oki Ridge. Quat Res (Daiyonkikenkyu) 34:
289–296
Okumura S, Minagawa M, Oba T, Ikehara K (1996) Paleoenvironmental analysis of
two sediment cores off Akita City in the Japan Sea based on oxygen, carbon
and nitrogen isotope. Quat Res (Daiyonkikenkyu) 35:349–358
O’Neil JR (1968) Hydrogen and oxygen isotope fractionation between ice andwater. J Phys Chem 72:3683–3684
Pierre C (1999) The oxygen and carbon isotope distribution in the Mediterraneanwater masses. Mar Geol 153:41–55
Porter SC, An Z (1995) Correlation between climate events in the North Atlantic
and China during the last glaciation. Nature 375:305–308
Rasmussen SO, Bigler M, Blockley SP, Blunier T, Buchardt SL, Clausen HB,
Cvijanovic I, Dahl-Jensen D, Johnsen SJ, Fischer H, Gkinis V, Guillevic M,
Hoek WZ, Lowe JJ, Pedro JB, Popp T, Seierstad IK, Steffensen JP,
Svensson AM, Vallelonga P, Vinther BM, Walker MJC, Wheatley JJ,
Winstrup M (2014) A stratigraphic framework for abrupt climatic changes
during the Last Glacial period based on three synchronized Greenland
ice-core records: Refining and extending the INTIMATE event
stratigraphy. Quat Sci Rev 106:14–28
Sagawa T, Yokoyama Y, Ikehara M, Kuwae M (2011) Vertical thermal structure
history in the western subtropical North Pacific since the Last Glacial
Maximum. Geophys Res Lett 38:3–7
Sagawa T, Nagahashi Y, Satoguchi Y, Holbourn A, Itaki T, Gallagher SJ, SaavedraPellitero M, Ikehara K, Irino T, Tada R (2018) Integrated tephrostratigraphy
and stable isotope stratigraphy in the Japan Sea and East China Sea using
IODP Sites U1426, U1427, and U1429, Expedition 346 Asian Monsoon. Prog
Earth Planet Sci 5:18
Schlolaut G, Brauer A, Marshall MH, Nakagawa T, Staff RA, Ramsey CB, Lamb
HF, Bryant CL, Naumann R, Dulski P, Brock F, Yokoyama Y, Tada R,
Haraguchi T (2014) Event layers in the Japanese Lake Suigetsu “SG06”
sediment core: description, interpretation and climatic implications. Quat
Sci Rev 83:157–170
Scholz D, Hoffmann DL (2011) StalAge - an algorithm designed for constructionof speleothem age models. Quat Geochronol 6:369–382
Schrag DP, Adkins JF, McIntyre K, Alexander JL, Hodell DA, Charles CD, McManusJF (2002) The oxygen isotopic composition of seawater during the Last
Glacial Maximum. Quat Sci Rev 21:331–342
Seierstad IK, Abbott PM, Bigler M, Blunier T, Bourne AJ, Brook E, Buchardt SL,
Buizert C, Clausen HB, Cook E, Dahl-Jensen D, Davies SM, Guillevic M,

Page 14 of 15

Johnsen SJ, Pedersen DS, Popp TJ, Rasmussen SO, Severinghaus JP,
Svensson A, Vinther BM (2014) Consistently dated records from theGreenland GRIP, GISP2 and NGRIP ice cores for the past 104 ka reveal
regional millennial-scale δ18O gradients with possible Heinrich event
imprint. Quat Sci Rev 106:29–46
Seki A, Tada R, Kurokawa S, Murayama M (2019) High-resolution Quaternary
record of marine organic carbon content in the hemipelagic sediments of
the Japan Sea from bromine counts measured by XRF core scanner. Prog
Earth Planet Sci 6:1
Shen CC, Edwards RL, Cheng H, Dorale JA, Thomas RB, Moran SB, Weinstein SE,
Edmonds HN (2002) Uranium and thorium isotopic and concentration
measurements by magnetic sector inductively coupled plasma mass
spectrometry. Chem Geol 185:165–178
Shen CC, Cheng H, Edwards RL, Moran SB, Edmonds HN, Hoff JA, Thomas RB(2003) Measurement of attogram quantities of 231 Pa in dissolved andparticulate fractions of seawater by isotope dilution thermal ionization mass
spectroscopy. Anal Chem 75:1075–1079
Shen CC, Kano A, Hori M, Lin K, Chiu TC, Burr GS (2010) East Asian monsoon
evolution and reconciliation of climate records from Japan and Greenland
during the last deglaciation. Quat Sci Rev 29:3327–3335
Shen CC, Wu CC, Cheng H, Edwards RL, Hsieh YT, Gallet S, Chang CC, Li TY, Lam
DD, Kano A, Hori M, Spötl C (2012) High-precision and high-resolution
carbonate 230Th dating by MC-ICP-MS with SEM protocols. Geochim
Cosmochim Acta 99:71–86
Sone T, Kano A, Okumura T, Kashiwagi K, Hori M, Jiang X, Shen CC (2013)
Holocene stalagmite oxygen isotopic record from the Japan Sea side of theJapanese Islands, as a new proxy of the East Asian winter monsoon. Quat Sci
Rev 75:150–160
Sone T, Kano A, Kashiwagi K, Mori T, Okumura T, Shen CC, Hori M (2015) Twomodes of climatic control in the Holocene stalagmite record from the Japan
Sea side of the Japanese islands. Isl Arc 24:342–358
Steinke S, Mohtadi M, Groeneveld J, Lin LC, Löwemark L, Chen MT, RendleBühring R (2010) Reconstructing the southern South China Sea upper watercolumn structure since the Last Glacial Maximum: implications for the East
Asian winter monsoon development. Paleoceanography 25:1–15
Steinke S, Glatz C, Mohtadi M, Groeneveld J, Li Q, Jian Z (2011) Past dynamics ofthe East Asian monsoon: no inverse behaviour between the summer andwinter monsoon during the Holocene. Glob Planet Change 78:170–177
Sun Y, Clemens SC, Morrill C, Lin X, Wang X, An Z (2012) Influence of Atlantic
meridional overturning circulation on the East Asian winter monsoon. Nat
Geosci 5:46–49
Tada R, Koizumi I, Cramp A, Rahman A (1992) Correlation of dark and light layers,
and the origin of their cyclcity in the Quaternary sediments from the Japan
Sea. Proc ODP Sci Results 127/128(1):577–601
Tada R, Irino T, Koizumi I (1999) Land-ocean linkages over orbital and millennial
timescales recorded in late Quaternary sediments of the Japan Sea.
Paleoceanography 14:236–247
Tada R, Zheng H, Clift PD (2016) Evolution and variability of the Asian monsoon
and its potential linkage with uplift of the Himalaya and Tibetan Plateau.
Prog Earth Planet Sci 3:4
Tada R, Irino T, Ikehara K, Karasuda A, Sugisaki S, Xuan C, Sagawa T, Itaki T,
Kubota Y, Lu S, Seki A, Murray RW, Alvarez-Zarikian C, Anderson WT Jr,
Bassetti M-A, Brace BJ, Clemens SC, da Costa Gurgel MH, Dickens GR,
Dunlea AG, Gallagher SJ, Giosan L, Henderson ACG, Holbourn AE, Kinsley
CW, Lee GS, Lee KE, Lofi J, Lopes CICD, Pellitero MS, Peterson LC, Singh
RK, Toucanne S, Wan S, Zheng H, Ziegler M (2018) High-resolution andhigh-precision correlation of dark and light layers in the Quaternary
hemipelagic sediments of the Japan Sea recovered during IODP
Expedition 346. Prog Earth Planet Sci 5:19
Tian J, Huang E, Pak DK (2010) East Asian winter monsoon variability over the lastglacial cycle: Insights from a latitudinal sea-surface temperature gradient acrossthe South China Sea. Palaeogeogr Palaeoclimatol Palaeoecol 292:319–324
Wang YJ, Cheng H, Edwards RL, An ZS, Wu JY, Shen CC, Dorale JA (2001) A highresolution absolute-dated Late Pleistocene monsoon record from Hulu Cave,
China. Science 294:2345–2348
Wang Y, Cheng H, Edwards RL, Kong X, Shao X, Chen S, Wu J, Jiang X, Wang X,
An Z (2008) Millennial- and orbital-scale changes in the East Asian monsoon
over the past 224,000 years. Nature 451:1090–1093
Xing L, Zhang R, Liu Y, Zhao X, Liu S, Shi X, Zhao M (2011) Biomarker records ofphytoplankton productivity and community structure changes in the Japan
Sea over the last 166 kyr. Quat Sci Rev 30:2666–2675

Amekawa et al. Progress in Earth and Planetary Science(2021) 8:18

Yamamoto M, Sai H, Chen MT, Zhao M (2013) The east Asian winter monsoon
variability in response to precession during the past 150 000 yr. Clim Past 9:2777–2788
Yancheva G, Nowaczyk NR, Mingram J, Dulski P, Schettler G, Negendank JFW, Liu
J, Sigman DM, Peterson LC, Haug GH (2007) Influence of the intertropicalconvergence zone on the East Asian monsoon. Nature 445:74–77
Zhao S, Liu Z, Colin C, Zhao Y, Wang X, Jian Z (2018) Responses of the East Asiansummer monsoon in the low-latitude south china sea to high-latitude millennialscale climatic changes during the last glaciation: evidence from a high-resolution
clay mineralogical record. Paleoceanogr Paleoclimatology 33:745–765

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.

Page 15 of 15