OBSERVATION FOR FLOATING PLASTICS IN THE SEAS ADJACENT TO JAPAN
AND THE WESTERN NORTH PACIFIC BY JAPAN METEOROLOGICAL AGENCY

by Mitsuhiko Ida

Deputy Director, Ocean Office, Policy Bureau, Ministry of Land, Infrastructure and Transport
2-1-3, Kasumigaseki, Chiyoda-ku, Tokyo 100-8918, Japan
ida-m2ih@mlit.go.jp

INTRODUCTION

Japan Meteorological Agency (JMA) is an affiliate agency of the Ministry of Land, Infrastructure and Transport. The goals of JMA are mitigation and prevention of natural disasters, safety of transportation, development and prosperity of industry, and Improvement of the public welfare. To meet these goals, JMA has been focusing its efforts on monitoring earth environment and on forecasting natural phenomena in the atmosphere, the ocean and the earth, as well as on conducting researches and technical developments in the relevant fields. JMA observes marine pollution in the seas adjacent to Japan. Marine pollution monitored by JMA consists of oil pollution and heavy metal. Floating plastics is observed as one form of the oil pollution.

OBSERVATION OF FLOATING PLASTICS

JMA observes floating plastics in the seas adjacent to Japan and the western North Pacific. The basic method of monitoring floating plastics is the following:

Monitoring Method

• Several observational lines are determined (Figure 1).
• Research ships go along with the lines.
• Observers watch the sea surface from the bridge during the daytime.
• When observers find floating pollutants they record locations and types of the pollutants.

The observation line on 137 east longitude line was established in 1977, and since then JMA has observed floating pollutants on this line.

DISTRIBUTION OF FLOATING PLASTICS IN 2005

Because the monitoring is conducted in such a way as indicated above, the observation results are described as the number of pieces of floating plastics per 100km. The Figure 2(a), Figure 2(b), Figure. 2(c) and Figure 2(d) show the observation results in winter, spring, summer and autumn, respectively. The size of circles in the figures indicates the number of floating plastics per 100km. The mark “+” means that no plastics are found all the daytime.

Figure 2. Distribution of floating plastics in 2005

As the Figures show that from spring to autumn, more than 20 pieces of floating plastics per 100km are found in the seas adjacent to Japan. Relatively many floating plastics are found around 30 north latitude line, south of the Kuroshio and the Kuroshio Extention. The seasonal tendency has not changed for the past several years.

NUMBER AND COMPOSITION OF FLOATING PLASTICS

According to the types of floating plastics, they are categorized into the four types: polystyrene form, fishing gear, plastic film, and other plastics. Figure 3 is the overview of the observation results in 2005, which indicates what types of floating plastics were found in which sea areas. In general, large proportion of floating plastics was occupied by Polystyrene form. This is not the tendency in 2005 but the overall tendency in the recent years. In East China Sea and NOWPAP Sea, the average number of floating plastics is large twice than in other seas. In particular, plastics in the form of fishing gear account for as much as 50 percents.

* In this monitoring by JMA, plastics are categorized by the following criteria.

• Polystyrene form
• ishing gear, including signs attached to nets
• Plastic film, including plastic bags and sheets
• Other plastics, including containers of detergent and plastic bottles

Figure 3. Number and composition of floating plastics by sea areas

AVERAGE DISTRIBUTION OF FLOATING PLASTICS BETWEEN 1981 AND 2000

The Figure 4 shows the average distribution of floating plastics between 1981 and 2000. The average distribution indicates that how many pieces of floating plastics were found annually from 1981 to 2000 in the areas divided by 5 degree longitude and latitude. In general, the number of floating plastics becomes smaller as the distance from the Asia Continent becomes larger. Also, the number of floating plastics in the sea adjacent to Japan is larger than that in the south of 20 north longitude and the sub-arctic region. Relatively many floating plastics are found around 30 north longitude, south of the Kuroshio and the Kuroshio Extention.

Figure 4. Average distribution of floating plastics between 1981 and 2000

TIME SERIES OF NUMBER OF FLOATING PLASTICS

The Figure 5 shows the time series of the number of floating plastics. As the figure indicates, the number of floating plastics in the seas adjacent to Japan has been decreasing from its peak around 1989.

Figure 5. Number of floating plastics by tim

JMA provides information on the marine pollution in the western North pacific on its website.
http:// www.data.kishou.go.jp/kaiyou/shindan/