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Remote Sensing Technology Center of Japan

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Ocean

Surveying Wider Areas of Global Oceans and Smaller Localized Areas of Ocean

Tsutomu Yamanokuchi

About 70% of the earth’s surface is covered with water. It is becoming increasingly important for Japan, an island nation surrounded by oceans, to monitor the conditions out at sea, in the interests of safeguarding its fishing industry, physical distribution routes, and isolated islands as well as monitoring environmental problems. Earth observation satellites are useful tools that enable extensive, detailed and regular surveying of wide areas of ocean.

Tsutomu Yamanokuchi, Ocean Team Leader

Northern Sea Route: Monitoring Sea Ice to Contribute to Safe and Cost-efficient Navigation for Shipping

In recent years, the sea ice in the Arctic Ocean has been declining, with its area reaching the smallest in observed history in September 2012. The shrinking of sea ice is a concern because of its implications for climate change. On the other hand, it is opening up the possibility of putting Northern Sea Routes into practical use. Compared to traditional shipping routes further south, the Northern Sea Route cuts time and fuel costs. There is also possibility that the route can be used to transport resources from Siberia, a treasure trove of natural resources. As such, many people across the globe are looking to the Arctic Ocean with great expectations.

However, to navigate in the Arctic Ocean the sea ice must be constantly monitored. This is where earth observing satellites come into play. Using satellite data allows sea ice to be finely ascertained over an extensive area. Using this satellite information in combination with meteorological data, initiatives are underway to predict the short, mid and long term state of sea ice across the entire shipping route.

There are two types of ice, with one type melting in a year, and the other type remaining for over a year, known as “multiyear ice.” Earth observing satellites are able to differentiate between the different types, and can plan shipping schedules in response to ever-changing conditions. There is also a possibility that these satellites can be used to monitor the environment, such as environmental pollution caused by oil leaking from ships.

The Northern Sea Route: The southern shipping route (indicated in red in the diagram) that passes through the Panama Canal is the shipping route normally used to connect Japan with Europe. If the Arctic Ocean shipping route (indicated in blue) that passes to the north of the Eurasian continent could be used, it would cut travel time to around two-thirds of its current total, significantly saving time and fuel. It would also avoid passing near Somalia, reducing the risk of being attacked by pirates. This has resulted in a rising tendency all around the world to take advantage of this shipping route in the summer when there is little ice.

Ocean Monitoring Using a Variety of Satellite Data

There are all types of satellites that frequently survey extensive areas, or survey limited areas in great detail. What they are able to see also differs, depending on whether they are equipped with an optical or microwave sensor. We used to sell data on a per satellite basis, but we now provide a combination of data gathered from multiple sensors on the basis of individual phenomena that the customer wants to focus on. For example, the diagram below shows the experimental model of an ocean monitoring system developed by RESTEC, commissioned by JAXA.

Arctic Ocean survey images taken by the (experimental) ocean monitoring system
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Arctic Ocean survey images taken by the (experimental) ocean monitoring system

(Left) Distribution of sea ice across the entire Arctic Ocean. White areas indicate sea ice. Hokkaido can be seen at the top right of the image. (Center) Magnified image of the region enclosed in red in the image on the left. (Right) A color image of the sea ice density distribution showing the ratio of sea covered in ice. The closer this ratio is to 100%, the more this color tends toward red. Blue indicates the ratio is close to 0%. Green areas indicate a ratio of around 50%. Monitoring the distribution of sea ice is not only important in the monitoring of the environment, but it can also be put to industrial use such as in the usage planning of North Sea Shipping Route.

Above is one example of sea ice data gathered from the Arctic Ocean, but it is possible to expand monitoring to cover the Pacific Ocean, Atlantic Ocean, or even the entire planet, and display a variety of data according to the purpose of use, such as the temperature or wind speed on the surface of the ocean, the level of the ocean surface, and other information.

Halting the Decline of Seaweed and Seagrass Beds

Halting the Decline of Seaweed and Seagrass Beds
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Seaweed and seagrass beds: Surveys carried out using satellites enable quantitative ascertainment of seaweed and seagrass bed distribution. Moreover, research is being carried out into sustained surveying to monitor changes in their distribution.
Materials taken from “Japan Coastal Kelp Forest Regeneration Monitoring Project” of the Fisheries Agency

Areas where seaweeds and seagrasses grow in great density are known as underwater forests, and they play an important role as feeding, spawning and nursery grounds for many marine organisms. However, it has been reported that seaweed and seagrass beds are in decline throughout the world, including Japan, due to various factors including reclamation work, eutrophication and global warming. From the perspective of maintaining biodiversity and managing aquatic resources, it is necessary to monitor and preserve seaweed and seagrass beds, and implement initiatives to assist in their recovery.

Until now, surveys of the distribution range of seaweed and seagrass beds centered mainly on diving, or interviewing people with a good grasp of local conditions. This required a major investment of time and effort. In recent years however, analyses of high spatial resolution satellite images have enabled efficient and quantitative ascertainment of the distribution of seaweed and seagrass beds over wide areas, contributing greatly to the advancement of technology for monitoring them.