“Environmental Protection Month” Meeting
“Ocean and Global Environment”
May 18, 2011
Mr. Masaji Matsuyama
President, Tokyo University of Marine
Science and Technology
Our training ship “Umitaka-maru” undertakes oceanographic observation each year, with the Japanese Antarctic Research Expedition team. Its research on global warming in the Antarctic Ocean, where there is minimal influence by mankind, has been highly evaluated.
Meiji-maru was a lighthouse tender constructed at Glasgow, Scotland, in 1874. In November 1876, Meiji-maru left the Port of Yokohama to make survey in the Ogasawara Islands. A British warship was also anchoring at Yokohama, scheduled to leave for Ogasawara. Meiji-maru reached Ogasawara 2 days earlier than the British warship, and completed its survey smoothly. This survey turned out to carry historical significance, as it served as the evidence that Ogasawara belonged to the Japanese territory.
Japanese territorial waters and Exclusive Economic Zone (EEZ) area rank 6th in the world, covering an extensive area of 4,470,000km2, equivalent to over 10 times of its land area of 380,000km2. The vastness of its sea area surely makes Japan a maritime nation.
1. Characteristics of the ocean
Images sent from the weather satellite “Himawari (Sunflower)” show that the ocean covers majority of the earth’s surface, making our planet the “water planet.”
The submarine topography shows a huge ridge running north to south of the Atlantic Ocean. Another huge ridge runs in the center of the Pacific Ocean. Japan is surrounded by very deep ridges. These oceanic ridges and trenches border the plates, the very birthplace of earthquakes about which I will talk later.
71% of the earth’s surface is the ocean, while 29% is the land. The highest summit on the land is Mt. Everest (8,840m), while the maximum water depth is known to be the Mindanao Deep (11,524m).
Surface temperature of the ocean gives direct impact on the weather and climate. The average seawater temperature distribution over the past 30 years naturally shows higher temperature around the equator and lower temperature around the polar region. However, temperatures differ between the eastern and western parts of the same latitude. In the Pacific Ocean, there is a relatively lower temperature area around the equator along South America.
2. Abnormal weather and the El Nino
El Nino phenomenon begins when easterly winds (trade winds) weaken, which cause the sea temperature to rise 4℃ higher than the average around the equator off Peru. This is because a pool of warm water stored in the western area around Indonesia moves eastward, along with the cloud formed by updraft caused by the high temperature waters. Today, various studies prove that El Nino is closely related to abnormal weather observed around the world.
El Nino occurred several times between 1970 and 2005. The strongest El Nino effect from 1997 to 1998 caused serious drought and consequent catastrophic fires at several locations in South-East Asia.
Sea-surface temperature rises of 2-4℃ give an enormous impact on the climate. El Nino brings to Japan a warm winter or heavy rains in the summer. We have come to witness abnormal weathers around the world in recent years.
3. Global warming and change in temperature
According to the report by IPCC (Intergovernmental Panel on Climate Change), the annual average surface air temperature around the world, in the long run, has risen at the rate of 0.76℃ per 100 years. Yet, its rate has accelerated since 1965.
Likewise, the annual average surface ocean temperature has risen at the rate of 0.5℃ per 100 years. Yet, we started to have many more years with high temperatures since the mid-1990s. Both the surface air and ocean temperatures are rising. As the sea temperature around Japan is rising 2-3 times more than the world average, there are growing concerns about its impact on marine life.
CO2 concentration observed in the atmosphere is also rising every year, from 315ppm in 1960 to 370ppm in 2005. Today, it is possibly around 380ppm. The increasing CO2 emissions are believed to trigger global warming.
Now, is the ocean absorbing CO2? The answer is yes, but its absorption volume is gradually decreasing. The ocean eases global warming through the following 3 mechanisms: 1) it absorbs 80% of the heat emitted in the atmosphere, 2) it absorbs 30% of the CO2 emitted in the atmosphere, and 3) it is a treasure house of diversified biology and sinks carbon to the bottom by biological pump. Again, its function to ease global warming is waning little by little.
I believe we can ease global warming by the following measures:
・Try to reduce greenhouse gas emissions through technological development.
・Establish a long-term monitoring system on global warming promptly.
・Make highly accurate future forecasts.
・Make international cooperation against global warming.
4. The East Japan Great Earthquake and tsunami
The 9.0-magnitude earthquake hit East Japan at 14:46 on March 11. Many magnitude-7-level aftershocks followed. Was this earthquake really beyond expectation? The hypocentral distribution of recent years shows that magnitude-9-level earthquakes have occurred around oceanic ridges and trenches, including off Sumatra and Chile. Therefore, we must be well prepared for earthquakes of such scale in the future.
It is said that the East Japan Great Earthquake triggered tsunami with the speed of 5m/second, which has an enormous power equivalent to a wind power over 140m/second. The initial wave reached Ofunato Port, Iwate Prefecture, at 15:10, followed by the maximum wave of 11.8m high reaching at 15:18. My heart goes out to the tsunami victims who failed to escape or did not try to escape.
Let me close my speech by sharing with you the tips for escaping tsunami damages:
・Forecasts on earthquake location and tsunami arrival time are pretty accurate.
・Current forecasts on the scale of tsunami are not sufficient.
・Large submarine earthquakes will trigger large tsunamis.
・Tsunami is likely to come repeatedly after the arrival of the initial wave.
・Tsunami-affected areas in the past are always tsunami-prone areas in the future.