On January 24th, the same cold front that fell through the Eastern United States and Europe, also brought unusually low temperatures and snow throughout the Japanese archipelago.  Until now, snow had only been observed in Okinawa Prefecture here on Kumejima, however, this time, measurable snow was also recorded on Okinawa for the first time, although it was only a little.

Between the afternoon of the 23rd and the evening of the 24th, the temperature on Kumejima fell 10°C. The temperature when the snow fell was less than 6°C (higher elevations on the island had lower temperatures than at the OTEC facility) with the lowest temperature recorded at the OTEC Facility of 5°C, the lowest temperature in 29 years.

With this unusual weather, we of course are interested in its affect on the sea temperature.

At the Okinawa OTEC Facility we record the incoming seawater temperature for both surface (15m) and deep seawater (612m).  We include that data in the graph above. The red line indicates the surface seawater temperature, the blue line is the deep seawater, and the green line is the air temperature for a week.

As you can see, even from the peak air temperature of 17°C, the seawater maintained its temperature of about 23°C, not even changing 1°C through the 10°C temperature drop.

The specific heat of seawater is about 4 times greater than air, and the specific gravity is about 800 times greater. When comparing the same volume, you will need 3200 times more energy to warm seawater 1°C than air. In other words, seawater stores vast amounts of heat energy. This resource is the source of the stable power produced by Ocean Thermal Energy Conversion.

This is also why the Okinawa OTEC facility can still produce power, even when it snows.

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