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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.
FNMOC's MLD Values
The original paper used FNMOC's MLD output from their TOPS model. These monthly fields are shown below. If you look over the images, you will see a change in character starting in October 2004. Before October, 2004, the TOPS model used the upper 400 meters of the OTIS global circulation model, but starting in October of 2004 the OTIS model was replaced with a data assimilation model (NCODA).
FNMOC is primarily tasked to provide atmospheric products. TOPS stands for "Thermal Ocean Prediction Model", and it provides data for the base of their atmospheric models (mainly temperature, moisture, and momentum flux). The MLD values provided from this model reflects this interest, as it is a thermal mixed layer depth, ie, it is what is normally called an isothermal layer depth (a layer of constant temperature) rather than a mixed layer depth (a layer of constant density). The definition of the TOPS "MLD" is the depth at which there is a 0.5 degree decrease in temperature from the value at the surface ... it really is an isothermal layer depth (ILD).
In general, ILD can be used to approximate MLD in mid latitudes, but it tends to fall apart in the high latitudes, in particular in the Southern Ocean and in the North Pacific. A comparison between the two fields done by the Naval Research Lab (NRL) illustrates this in general.
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| depths range from 0 to 400 m
shallow values are in the blues, deep values go to reds
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1998
January
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TOPS mld
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1998
February
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TOPS mld
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1998
March
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TOPS mld
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1998
April
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1998
May
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1998
June
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1998
July
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1998
August
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1998
September
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1998
October
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1998
November
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1998
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1999
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1999
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1999
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1999
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1999
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1999
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1999
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1999
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1999
September
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1999
October
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1999
November
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1999
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2000
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2000
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2000
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2000
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2000
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2000
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November
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2001
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2001
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2001
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2001
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2001
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2001
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2001
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2001
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2001
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2001
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2002
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2002
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2002
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2002
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2002
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2002
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2002
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2003
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2003
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2003
November
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2005
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2005
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2005
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2005
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2005
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2005
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2005
October
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2005
November
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2006
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2006
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2006
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2006
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