On Feb. 10 at 7 p.m., the Capital Chapter of New Hampshire Audubon will present a program titled “Observing Microscopic Ocean Life from Space.” Alison Chase, a research associate at Atmospheric & Environmental Research Inc., explains the ways we can study changing global phytoplankton populations using satellite ocean color. This program is free and open to the public.
Phytoplankton are microscopic algae that not only represent the start of the world's all-important food chain but are also responsible for producing about half of the world's oxygen. Optical oceanography uses the color of ocean water to measure the amount of chlorophyll in the ocean, an indicator of phytoplankton populations.
Although they are too small to be seen inpidually with the naked eye, when they are present in high concentrations the color of ocean water appears both greener and more opaque. This greenish color, which is often seen in coastal areas, is a result of the presence of chlorophyll in phytoplankton. Measuring the amount of green light relative to blue light in the water can be done from space using satellites.
Several different satellites have been used to measure chlorophyll from space over the last three decades. These satellites measure the amount of light coming out of the ocean at several different wavelengths on the visible light spectrum. If there is more green light reaching the satellite, this indicates the presence of phytoplankton, since they are green-colored. Using satellites to measure chlorophyll makes it possible to study phytoplankton populations on a global scale, which is important for understanding how the world's oceans may be changing over time, and possibly in connection with a changing global climate. In order to be confident in the measurements made by satellites, hands-on measurements of chlorophyll are made in the field. This validation of satellite data is an ongoing effort, as oceanographers work to get the most accurate information possible out of the information coming from space. As satellite data, field measurements, and the comparison between the two are improved, optical oceanography will continue to provide insight on the conditions of coastal and global oceans.
