Form 3

Annual Report
LaMer, Ehime University
Date (29, November, 2016)
To Director of LaMer
Principle Investigator:
Affiliation

Ocean University of China

Position

Graduate student

Name in print＿＿ Haiyan Yang ＿ ＿ ＿Include the report on the result of the project/meeting in a separate sheet.
1. Project / Meeting title
The variation of nutrients concentration along the main stream of the Kuroshio andits controlling factors
2. Members of project / meeting
Name

Affiliation

PositionContribution partPI
Haiyan Yang

Ocean University of China

Graduatestudent(M3)Dataprocessing
analyzingMembers
Xinyan Mao

Ocean University of China

Lecturer

Beneficial discussion

Xinyu Guo

Ehime University

Professor

Beneficial discussion

and3. Contents (please write in separate sheet, A4-size, within 5 pages including figures andtables. Itemize “Title, members’ names and affiliations, aim, procedure, result,publication/conference presentation, perspectives in future”).
This report will be opened to the public through LaMer website and printed matter. Please
send additional products, i.e., abstract book, reprint, if available toLaMer Office of Research Support Division,
Ehime University, Bunkyo 2-5, Matsuyama, 790-8577 Japan
E-mail: lamer@stu.ehime-u.ac.jp
Tel and Fax: +81-89-927-8187

TitleThe variation of nutrients concentration along the main stream of the Kuroshio and its
controlling factors

Members’ names and affiliations
NameInstitutionand Employment
Department position

E-mailCollege of Oceanic
Xinyan MaoandAtmospheric Lecturer

Sciences,

maoxinyan@ouc.edu.cn

Ocean

University of China
Faculty member of Professor
Xinyu Guoguoxinyu@sci.ehime-u.ac.jp

LaMerAim
With the help of Prof. Guo Xinyu in Ehime University, this project aims to explore
the seasonal variation of average nutrients concentration in the mixed layer, and to study
the contribution of physical processes influencing the variation of nutrients in the mixedlayer.

Procedure
1. Our joint research concentrated on processing the observed data from WOD13(World Ocean Database 2013) in this year (2016). WOD13 contained standard depth
level profile data with quality control, so we can remove the inadequate data and obtain
the average value for one-degree analysis. The first-guess field was built up by applying
IDW (Inverse Distance Weighted) to the statistical field. Then a correction (Barnes,1964) to the first-guess value was computed. The climatological annual, seasonal andmonthly mean fields were created after “three-pass correction” and median filter.

2. The climatological monthly mixed layer depths using Argo profiles was used tocomputed the winter mixed layer depths. In this way, the distribution of nutrientsaverage concentration in winter mixed layer can be showed.
3. Based on some assumptions and backgrounds, the nutrient average concentrationconservation equation was derived.
After the discussion with Prof. Guo Xinyu, we will set out further research asfollows:
1. Processing the OFES model nutrients data and comparing the difference of seasonalvariation between the model and observed nutrients data.
2. Quantifying each term in the nutrient average concentration conservation equation,and to study the influencing factors of nutrient seasonal variation.

Results
Wintertime ML has been generally believed to deepens due to wind stirring and sea
surface cooling. In Fig.1, we can find that the deepest mixed layer depth (MLD) appearsin Kuroshio Extension and the region along the latitude of 40°N. Around latitude of20°N, there are regions where wintertime oceanic mixed layer shoals (Takeuchi andYasuda, 2003; Oka et al., 2007).
In the region to the north of 30°N，the nutrient average concentration in the wintermixed layer shows zonal distribution along latitude (Fig.2). The low values of nutrient
average concentration in the subtropical regions result from downwelling.
The most apparent increase of average concentration in winter ML locates in theeast of Japan and the Japan Sea (Fig.3). Phosphate and nitrate have similar distributions
because they are governed by almost the same biological cycle, but the silicate

distribution is not as closely similar (Talley et al., 2011). In winter, nitrate andphosphate average concentration basically increase along the Kuroshio path, and theyremains largely unchanged in the subtropical regions.
We set out analyzing the seasonal details of the nutrient concentration in the 137°E
section (Fig.4). It is obvious that contours of nutrient concentration are upraised in thetop layer of winter ML around region of 0 ~ 10°N and north of 30°N. In summer, nearlatitude of 10°N or 30°N, nutricline is below the winter mixed layer, but in winter, it’s
no longer clear because of vertical convection.
In addition, to better understand the processes that affect the seasonal variation ofnutrient, the upper-ocean nutrient budget is expected to study. We define an interface
marking the maximum extent of the convection process, the thickness of the mixed
layer in the winter, h=f(x,y,t). The equation for the variation of nitrate concentration in
the winter ML is as follow:.
In the future, we will use OFES model results to estimate each term in this equation.
References:Barnes, S. L. (1964). A technique for maximizing details in numerical weather mapanalysis. Journal of Applied Meteorology, 3(4), 396-409.
Holte, J., J. Gilson, L. Talley and D. Roemmich (2016): Argo Mixed Layers, Scripps
Institution of Oceanography/UCSD http://mixedlayer.ucsd.edu.
Oka, E., Talley, L. D., & Suga, T. (2007). Temporal variability of winter mixed layer inthe mid-to high-latitude North Pacific. Journal of oceanography, 63(2), 293-307.
Takakura, K., Xiaohong, W., Takeuchi, K., Yasuda, Y., & Fukuda, S. (2003).
Deactivation of norepinephrine by peroxynitrite as a new pathogenesis in thehypotension of septic shock. The Journal of the American Society ofAnesthesiologists, 98(4), 928-934.
Talley, L. D. (2011). Descriptive physical oceanography: an introduction. Academicpress.

Fig. 1 Distribution of winter MLD calculated from the Argo data (Holte et al., 2016)

Fig. 2 Distribution of nutrient average concentration in winter MLD

(winter and summer)

Fig. 3 Average concentration difference between winter and summer in winter MLD

Fig. 4 Distribution of temperature along 137°E in winter/summer

Publication/conference presentation
Oral presentation:
Title: The variation of average nutrients concentration in the mixed layer fromsummer to winterSpeaker: Haiyan Yang.
Time: November 15, 2016.
Location: Ehime University.

Perspectives in future
The reason for the seasonal variation of nutrient concentration in mixed layer is
expected to further analyzing. We wish to explore the main influencing processes throughobserved data and model data, and to publish the research on a satisfied journal.