Title
Low sea surface salinity in the Japan Sea during the last glacial maximum

Members’ names and affiliations
EmploymentNameInstitution and Department
Emploposition

Kailun Du

Ocean University of China

Huiwang
Gao

Ocean University of China

Masterstudent
Professor

Jie Shi

Ocean University of China

Associate Professor

Xinyu Guo

Faculty member of LaMer

Professor

courseAim
This project aims to clarify the sea surface salinity in the Japan Sea during the last glacialmaximum (LGM) and to estimate the impacts of the volume transport through the Tsushima Strait aswell as evaporation and precipitation on the reduction of sea surface salinity in the Japan Sea.

Procedure
The principal investigator (PI) carried out many sensitive experiment using a freshwater budget
model for the Japan Sea and obtained following conclusions.
1

The minimum value during the LGM (around 20 ka) is 14-27 and is very sensitive to thechange of the volume transport.

2

The change of the volume transport through the Tsushima Strait is linear with thereduction of sea level.

3

The variation trend of salinity is consistent with that of the oxygen isotope of planktonic
foraminifera in the paleoclimatic results.

During the stay of PI in Matsuyama, I reported above results by giving an oral presentation“Low sea surface salinity in the Japan Sea during the last glacial maximum”

Results
1. The volume transport through Tsushima Strait
We use POM (Princeton Ocean Model) to simulate the Japan Sea and designed 11 cases, where1 / 4

we change the topography conditions that every 10 meters drop in sea level, from 0 m to -100 m.
Then we select the cross-section of the Tsushima Strait to calculate the volume transport in each caseand obtain the relationship between the sea level and the volume transport (Fig.1), they are the linearrelationship. And we collect the details of sea level and time from other studies (Yokayama et al.,2019, Saito et al., 1998, Arz et al., 2007). Finally, we get the curve of volume transport and time(Fig.2). The changing trend of volume transport is very consistent with that of the sea level. These
apply to the calculation of the salinity in the Salt budget model.

ELUV(b)(a)Fig. 1 (a) The section in Tsushima Strait that we chose (black line 34.25°N, 127.375 -130.625°E).
The triangular and circular signs indicate the location of the water level, the velocity in the U
direction, and the velocity in the V direction. And the volume transport through Tsushima Strait tothe Japan Sea (b) is calculated from the cross-section and velocity of the Tsushima Strait, where thevelocity and the cross-section variation are obtained from the details of the POM model. The blackbox is the calculation result of the POM model, the red line is the curve of the linear fitting, and theblue line is the assumed volume transport.

Fig. 2 The red lines represent the sea level data sources that we used are from (a) Yokayama et al.
(2019), (b) Saito et al. (1998) and (c) Arz et al. (2007), respectively. The blue lines are the volumetransport through the Tsushima Strait, whose relationship to time corresponds to the relationshipbetween sea level and time.

2. The salinity simulation
Due to the different sources of sea level data, the variation of salinity varies to some extent. The
salinity begins to gradually decline from 30 ka, until the minimum, and then slowly recovers inabout 13ka and returns to the normal level. However, the minimum occurs at different times and theminimum values are different, which is related to the change of the minimum value of the volume
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transport. The minimum values occur at 20ka, 17ka or 16ka. The values are 14.0, 25.5 or 27.0.
And the variation trend of salinity is consistent with that of oxygen isotope of planktonic
foraminifera in the paleoclimatic results. The reduction of salinity is not enough to lead to the degreeof isotope reduction, there are other factors to cause isotope reduction.

Fig. 3 The evolution of salinity for the basic case and the values means the salinity of the upper 200
m layer of the Japan Sea. The gray area represents the range of value fluctuations, while the red, blue,and green lines represent the sea level sources that we used from Yokoyama et al. (2019), Saito et al.
(1998) and Arz et al.(2007), respectively.

Fig. 4 Comparison of salinity and oxygen isotopes of planktonic foraminifera in the paleoclimatic
results, which are obtained from Sagawa et al. (2018). The circle dot for orange, dark yellow andolive represent oxygen isotopes values of three different planktonic foraminifera in figures. And thesalinity for red, blue, and green lines in figure (b) represents the sea level sources that we used fromYokoyama et al. (2019), Saito et al. (1998) and Arz et al.(2007), respectively.

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References:Arz, H. W., Lamy, F., Ganopolski, A., et al. Dominant Northern Hemisphere climate control overmillennial-scale glacial sea-level variability. Quaternary Science Reviews, 26(3-4):0-321, 2007.
Sagawa, T., Nagahashi, Y., Satoguchi, Y., et al. Integrated tephra stratigraphy and stable isotopestratigraphy in the Japan Sea and East China Sea using IODP Sites U1426, U1427, and U1429,
Expedition 346 Asian Monsoon. Progress in Earth & Planetary Science, 5(1):18, 2018.
Saito, Y., et al. Transgressive and highstand systems tracts and post-glacial transgression, the EastChina Sea. Sedimentary Geology, 122(1-4):217-232, 1998.
Yokoyama, Y., Purcell, A., and Ishiwa, T. Gauging quaternary sea level changes through scientific,
ocean drilling. Oceanography,

32(1):64-71, 2019.

Publication/conference presentation
Oral presentation (LaMer):
Title: Low sea surface salinity in the Japan Sea during the last glacial maximum
Lecturer: Kailun Du.
Time: November 19, 2019.
Location: Ehime University.

Perspectives in future
We will clarify the impacts on the reduction of oxygen isotopes of planktonic foraminifera
during the LGM, which can provide reference and basis for paleoceanography research. To further
study the effects of the sea level drop on the Japan Sea.

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