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Mixed Layer Depth Comparisons

The carbon model requires mixed layer depth (MLD) as an input variable. It is essential that the best estimation of MLD be used as input. These pages describe the rationale for selection of a final input set for processing.

SODA Comparison: Part II

We now have the following:

• our highest quality mld data set uses the FNMOC high res global ocean model; it starts in June, 2005
• our second highest quality set comes from the NCODA/TOPS ild data; these start in October, 2004, and give mld structure in the Southern Ocean similar to the high res set, but it overestimates the values south of Africa
• the SODA mld set appears to be of similar quality to the NCODA/TOPS ild data; the SODA data extends back to the launch of SeaWiFS in 1997, and gives mld structure in the Southern Ocean similar to the high res set, but with a shift the mld high west of South America

The comparison below illustrates what the mld timeline will look like if

• the SODA data just replaces the OTIS/TOPS ild (left column), or
• the SODA data replaces the OTIS mld as well, and is used as long as it is available (right column).

What can be seen is that

• the SODA mld is similar to the OTIS mld up to April 2000 (when OTIS mld becomes unavailable) -- it is not the same in the Southern Ocean, west of South America, but it is similar;
• when OTIS mld returns in September 2002, it shows a much stronger mld signal in the Southern Ocean than does SODA, including the "deep" south of Africa (not shown in high res model)
• the SODA model compares favorably at the end of 2004 with the startup of the NCODA/TOPS ild depths (which also have diminished mld signal west of South America)

Given the above, it would seem that use of SODA monthly mld values through the end of 2004 would be reasonable, giving mld based on a single model up to that point. NCODA/TOPS ild data can fill in for the first half of 2005, at which point the FNMOC high res mld values become available. NCODA/TOPS and FNMOC high res model are both available on a daily basis.