Table of Contents

• Dataset Description
  • Methods & Sampling
• Data Files
• Parameters
• Deployments
• Project Information
• Program Information

0.1 Percent Light Depths
nominal longitude is 140W

   PI:              Chuck Trees
   of:              San Diego State University
   dataset:         0.1 Percent Light Depths
   dates:           February 4, 1992 to March 8, 1992
   location:        N: 12  S: -12  W: -140.0  E: -140.0
   project/cruise:  EQPAC/TT007 - Spring Survey
   ship:            Thomas Thompson
 
   PI Notes:
 
   Enclosed are the depths of the 0.1% light levels as calculated from
   scalar PAR (broadband detector, 400-700 nm, Biospherical
   Instruments).  As some of you remember from the Spring Survey Cruise,
   I was trying to get the PI's to use percent light level depths based
   on downwelling vector irradiance at 488 nm, instead of the PAR
   values.  All near-surface downwelling optical measure- ments are noisy
   and it is difficult to extrapolate to the surface.  One method which
   helps in fitting this data near the surface is to plot it in log space
   and for many wavelengths the irradiance is linear.  Downwelling
   irradiance at 488nm has this near-surface attribute.  Unfortunately, a
   PAR profile is curved near the surface (enhanced attenuation in the
   red).  making extrapolation difficult and introducing errors in
   estimating light depths.  Quoting Gordon and McCluney (1975, Appl.
   Opt. 14,2) "Furthermore, for broadband sensing systems, z90 can be
   determined only from spectral irradiance measurements..".  z90 is the
   depth at which 90% of the diffusely reflected irradiance originates
   that a satellite can observe, which is also the 37% light level.  With
   this disclaimer I hope you have fun with the data.
 
 
 

The U.S. EqPac process study consisted of repeat meridional sections (12°N -12°S) across the equator in the central and eastern equatorial Pacific from 95°W to 170°W during 1992. The major scientific program was focused at 140° W consisting of two meridional surveys, two equatorial surveys, and a benthic survey aboard the R/V Thomas Thompson. Long-term deployments of current meter and sediment trap arrays augmented the survey cruises. NOAA conducted boreal spring and fall sections east and west of 140°W from the R/V Baldridge and R/V Discoverer. Meteorological and sea surface observations were obtained from NOAA's in place TOGA-TAO buoy network.

The scientific objectives of this study were to determine the fluxes of carbon and related elements, and the processes controlling these fluxes between the Equatorial Pacific euphotic zone and the atmosphere and deep ocean. A broad overview of the program at the 140°W site is given by Murray et al. (Oceanography, 5: 134-142, 1992). A full description of the Equatorial Pacific Process Study, including the international context and the scientific results, appears in a series of Deep-Sea Research Part II special volumes:

Topical Studies in Oceanography, A U.S. JGOFS Process Study in the Equatorial Pacific (1995), Deep-Sea Research Part II, Volume 42, No. 2/3.

Topical Studies in Oceanography, A U.S. JGOFS Process Study in the Equatorial Pacific. Part 2 (1996), Deep-Sea Research Part II, Volume 43, No. 4/6.

Topical Studies in Oceanography, A U.S. JGOFS Process Study in the Equatorial Pacific (1997), Deep-Sea Research Part II, Volume 44, No. 9/10.

Topical Studies in Oceanography, The Equatorial Pacific JGOFS Synthesis (2002), Deep-Sea Research Part II, Volume 49, Nos. 13/14.

The United States Joint Global Ocean Flux Study was a national component of international JGOFS and an integral part of global climate change research.

The U.S. launched the Joint Global Ocean Flux Study (JGOFS) in the late 1980s to study the ocean carbon cycle. An ambitious goal was set to understand the controls on the concentrations and fluxes of carbon and associated nutrients in the ocean. A new field of ocean biogeochemistry emerged with an emphasis on quality measurements of carbon system parameters and interdisciplinary field studies of the biological, chemical and physical process which control the ocean carbon cycle. As we studied ocean biogeochemistry, we learned that our simple views of carbon uptake and transport were severely limited, and a new "wave" of ocean science was born. U.S. JGOFS has been supported primarily by the U.S. National Science Foundation in collaboration with the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the Department of Energy and the Office of Naval Research. U.S. JGOFS, ended in 2005 with the conclusion of the Synthesis and Modeling Project (SMP).