NOAA Teacher at Sea
Onboard NOAA Ship Ronald H. Brown
September 5 – October 6, 2001
Mission: Eastern Pacific Investigation of Climate Processes
Geographical Area: Eastern Pacific
Date: September 7, 2001
Latitude: 24° 3.063 N
Longitude: 112° 11.4 W
Seas: Sea wave height: 3-4 feet
Swell wave height: 4-6 feet
Visibility: 10 miles
Cloud cover: 3/8
Water Temp: 27.7°C
Science Log: Research has not yet started. The scientific crew was notified in a ship briefing that they are not allowed to gather and record data until the ship leaves Mexican waters.
Each day during this trip I will highlight one of the research groups on the ship and introduce you to the science they are doing. Today I met with the group from the University of California at Santa Barbara- Dr. Carter Ohlmann and Dave Menzies. These guys are studying the variations in ocean radiant heating, or in simpler terms, the amount of light in the ocean at different depths.
Imagine a nice clear swimming pool. The sun’s heat energy can penetrate all the way to the bottom of the pool because the water is so clear. Whatever heat energy hits the pool will be dispersed throughout the water somewhat evenly. Makes sense, right?
Now imagine that the pool has a layer of scum and algae at the top. Face it, you just haven’t done a very good job at cleaning the pool, and your allowance just isn’t big enough to make the job worthwhile. Now, the sun’s heat energy can’t pass all the way to the bottom of the pool because the scum is blocking the light. The very top of the pool water is going to capture almost all of the sun’s heat energy, and the bottom layers of water will be darker and colder.
The ocean has lots of “stuff” in it, right? Fish, whales, coral, seaweed… All plants, whether in the ocean or on land, contain a substance called “chlorophyll.” Chlorophyll is the substance that makes plants green. If you can detect chlorophyll in the ocean, you are detecting plant material- mostly in the form of algae. If the water appears green, it has a lot of algae, if it appears mostly blue with a little green, it has a little algae. Dr. Ohlmann and Mr. Menzies have special piece of equipment, called an SPMR, that can measure the exact “color” of the ocean. The water and chlorophyll in the ocean absorb and reflect solar energy, or light, and these scientists want to know how much of the sun’s heat energy is being absorbed and reflected at various depths in the ocean. In other words, how does the sun heat the ocean?
Aren’t there satellites that can accomplish the same task as what is being done on the ship? Well, there is a NASA satellite in space called “SeaWiFS” (Sea viewing Wide Field-of-view Sensor) that measures different wavelengths of light being reflected from the surface of the ocean, and it can determine how much blue and green is there. Remember, the more green that is present, the more algae that is present. But satellites are viewing the ocean from so far away, and they have to make lots of adjustments for the amount of light in the atmosphere. If it’s cloudy or foggy, it can be impossible for the satellite to see the ocean. Since Dr. Ohlmann and Mr. Menzies are right here at sea level, they can measure the amount of green and blue in the water at the surface, and at various depths in the ocean. For comparison, they also measure the light near sea level, by installing sensors on a large tower on the bow of the ship.
Why does anyone care about all this? There are lots of scientists around the world who try to model different aspects of climate. The computer models make certain assumptions about how heat circulates between the ocean and the atmosphere. Since any large body of water can have a profound affect on the land nearby, it is important that the climate models be accurate. The data being collected and analyzed by Dr. Ohlmann and Mr. Menzies will improve the accuracy of air-sea heat exchange in climate computer models.
Travel Log: You may have noticed from the sea data above that the wave height is larger today than it was yesterday. A satellite image on the bridge shows hurricane Henrietta in the area, which accounts for the swell we feel. The ship is rocking quite a bit, making it difficult to walk around too much, but I seem to have acquired my “sea legs” and the rocking isn’t making me sick. Hmmm, in a cartoon drawing, what would sea legs look like? Let me know if you have any ideas.
There’s not a lot of entertainment on the ship. If the weather is nice you can go out on deck and watch the flying fish. A lot of people have books and computers to play with when their shift ends. The only form of organized entertainment are the movies shown each night in the lounge. Just make sure you bundle up, because the lounge, and most indoor areas of the ship, are freezing! The air conditioning inside the ship keeps the temperature very low so that the millions of dollars of electronics equipment on board is safe from heat damage.
Question of the day: What is the difference between sea wave height and swell wave height?
Photo Descriptions: Today’s photos show Dr. Ohlmann and Mr. Menzies at work in the ship’s lab. The rocket-looking device they are holding is the SPMR mentioned in the Science Log above. The tower at the bow of the ship contains sensors that will measure the wavelength of light in the atmosphere at sea level. The large apparatus with the long cylinders is a CTD, which measures the conductivity (salinity), temperature, and depth of water samples.
Keep in touch,