A Line in the Sea

During the Joint Global Ocean Flux Study (JGOFS) research program in the equatorial Pacific in 1992, we used photographs and measurements from satellites, aircraft, ships and the Space Shuttle Atlantis to show dramatic biological responses to circulation and mixing processes associated with an open-ocean front. Breaking waves (whitecaps) caused by water turbulence and mixing just north of the Equator at the boundary (front) between two very powerful currents (North Equatorial Counter current and the South Equatorial Current), and very dark green water caused by extremely high concentrations of buoyant diatoms, made a distinct line in the sea visible for hundreds of kilometers. High phytoplankton biomass and primary production associated with the extensive diatom patches may explain anecdotal observations of high animal abundance along this frontal boundary.

Figures 2-6. Photographs of the line in the sea taken from viewing perspectives covering a range of ~109 in scale.

(2) A 57-km-long portion of the line shown on Figure 1 as photographed by astronauts on Atlantis using a telephoto lens (NASA photograph STS46-77-017). The center of this photograph is the same as that of Figure 1. The frontal boundary is displayed in much higher detail, giving the illusion of a rapid change in sea surface slope.

(3) Diatom (Rhizosolenia sp) patch(es) photographed by Dr. Petra Stegmann from the cockpit of the NASA P-3 research aircraft flying at 150 m altitude on 25 August, 1992, near 2o N Latitude, 140o W. Longitude.
(4) and (5) Rhizosolenia patch photographed by Dr. Ed Peltzer from the deck of the oceanographic research vessel, R.V. Thompson, on 25 August, 1995 near 2o N Latitude, 132o W. Longitude.

(6) Photomicrograph taken by Dr. William Balch of two Rhizosolenia cells collected from the patches illustrated above. The diameter of the cylindrically-shaped cells is ~200 microns.