Table of Contents

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

  PI:             Wilford Gardner (Texas A&M University),
                  Jan Gundersen (Texas A&M University)
                  John Morrison (North Carolina University)
  dataset:        Mixed layer depths
  dates:          January 08, 1995 to December 26, 1995
  location:       N: 22.5  S: 10  W: 57.3  E: 68.75
  project/cruise: Arabian Sea - All Process Cruises
  ship:           Thomas Thompson

  Wilford Gardner - based on temperature changes
  John Morrison - based on density changes						
  Arabian Sea Mixed Layer Depths - all process cruises

  PI Notes
  PI Notes on density vs. temperature calculation

 

Mixed layer depths are based on a temperature increase of 0.1 and 0.5
degrees C from the second temperature value listed in the CTD files, which
corresponds roughly to a density increase of 0.03 and 0.125 density units.

The second TEMPERATURE value was used because there occasionally appeared to
be questionable numbers as the first value.  The temperature change of 0.1
degree C was recommended by Dr. Craig Lee (WHOI) after looking at the data
and the 0.5 degree C value is the Levitus standard used in his NOAA global
atlases.  These are also the values used in the US JGOFS EqPac program.

Please note variable initial (starting) depths.

Calculations were made by Jan Gundersen. (TAMU).

Wilford D. Gardner
Dept. of Oceanography
Texas A&M University
College Station, TX 77843-3146

From Wilf Gardner, Texas A & M University, August 8, 1997

Since the New Hampshire meeting [July, 1997], we have compared the MLD
based on the temperature criteria of 0.1 and 0.5 degrees C compared with
the density differences of 0.03 and 0.125 density units.  About 75% of
the time the values are identical.  There are other occasions, however,
where there are significant differences, especially for the 0.1 degrees
C/0.03 comparison. When there is a difference, the temperature
calculations generally give deeper MLDs than density calculations.
Differences most often occur when there is a salinity increase below
the surface.  Temperature criteria are often used for MLDs on moored
data as salinity sensors are sometimes subject to greater drift than
temperature sensors.

None of the above criteria identify the "mixed-layer depth" perfectly in
all cases, but examination of depth plots where there are differences
suggest that the density criteria more reliably identify the depth of most
recent mixing.  For consistency, we recommend that the MLDs based on
density be used when you are trying to calculate mass budgets.  In some
situations, such as sometimes during the TN045 intermonsoon period, there
is no true mixed layer - just a depth at which the MLD criteria are finally
exceeded.  We suggest that you look at an expanded plot of the density
profile if your calculations are critical.

See Platform deployments for cruise specific documentation

The U.S. Arabian Sea Expedition which began in September 1994 and ended in January 1996, had three major components: a U.S. JGOFS Process Study, supported by the National Science Foundation (NSF); Forced Upper Ocean Dynamics, an Office of Naval Research (ONR) initiative; and shipboard and aircraft measurements supported by the National Aeronautics and Space Administration (NASA). The Expedition consisted of 17 cruises aboard the R/V Thomas Thompson, year-long moored deployments of five instrumented surface buoys and five sediment-trap arrays, aircraft overflights and satellite observations. Of the seventeen ship cruises, six were allocated to repeat process survey cruises, four to SeaSoar mapping cruises, six to mooring and benthic work, and a single calibration cruise which was essentially conducted in transit to the Arabian Sea.

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).