This animation shows the daily concentration of ocean surface chlorophyll as simulated by the Parallel Ocean Program (POP) with an embedded marine ecosystem model. While POP calculates the ocean currents, temperature and salinity, the ecosystem model simulates the complex interaction of microscopic marine plants (chlorophyll-containing phytoplankton), animals (zooplankton) and nutrients (such as nitrogen, phosphorus and iron). In addition to constituting a major part of the global food web, phytoplankton remove carbon dioxide from the atmosphere via photosynthesis much like their counterparts on land. As conditions in the ocean and atmosphere change due to increased carbon emissions, it is important to be able to use these kinds of models to understand the possible effects on life in the ocean and the global carbon cycle.
In the animation, the seasonal cycle of the phytoplankton bloom is clearly seen (greens and yellows) as the sun stimulates photosynthesis. The vast subtropical areas that never experience a strong bloom (blue hues) demonstrate that it is necessary for more than just sunlight to produce a bloom. In these regions, the ocean and atmospheric conditions combine to deprive the water of crucial nutrients necessary for photosynthesis. In contrast, the equatorial regions experience year-round blooms due to the steady supply of nutrients from below the sea surface provided by the ocean circulation. Near the poles, photosynthesis is almost completely shut down when there is sea ice present (magenta).