Adding iron to the diet of marine plant life has been shown in shipboard experiments to boost the amount of carbon-absorbing phytoplankton in certain parts of the world’s oceans. A new study promises to give scientists their first global picture of the extent of these unique “iron-limited” ocean regions, an important step in understanding how the ocean’s biology controls the flow of carbon between the atmosphere and the ocean.
The new study by researchers at NASA’s Goddard Space Flight Center and the Department of Energy’s Oak Ridge National Laboratory was presented at the American Geophysical Union’s annual meeting in San Francisco on Friday, Dec. 15, 2000.
Oceanic phytoplankton remove nearly as much carbon from the atmosphere each year as all land-based plants. Identifying the location and size of nutrient-limited areas in the open ocean has challenged oceanographers for nearly a century.
The study pinpointed iron-limited regions by seeing which phytoplankton-rich areas of the world’s oceans were also areas that received iron from wind-blown dust. In this map, areas with high levels of chlorophyll from phytoplankton and high levels of dust deposition (high correlation coefficients) are indicated in dark brown. Dust deposition was calculated by a 3-year modelled climatology for the years 1996–1998. The chlorophyll measurements are from 1998 observations from the SeaWiFS (Sea-viewing Wide Field-of-view Sensor) instrument on the OrbView-2 satellite.
“Global, satellite-based analyses such as this gives us insight into where iron deposition may be limiting ocean biological activity,” says lead author David Erickson of Oak Ridge National Laboratory’s Computer Science and Mathematics Division. “With this information we will be able to infer how the ocean productivity/iron deposition relationship might shift in response to climate change.”
Map Source: David Erickson, Oak Ridge National Laboratory’s Computer Science and Mathematics Division
