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Global mean nutrient profile, thoughts.



Dear ocmip ... anybody interested in discussing this?

I have been pondering the Levitus global nitrate climatology
and my BGC model, and considering the well-known and generally
fairly well modelled nutrient peak at around 1000m depth.

Most modellers reproduce this by setting a quite shallow remineralisation
depth for their POM. I might be bold enough to think
that trap data don't always agree with such 'shallow profiles', and that
the 1000m peak could be largely a product of water mass formation. After all,
the most obvious 1000m peak in the Levitus data is in the equatorial Atlantic,
arguably a product of South Atlantic Intermediate water formation combined
with some remineralistaion, perhaps or perhaps not at ~1000m, and (I
speculate) general upward trends of both bottom and deep water at low
latitudes. After all, z-coordinate models used by most of us are rather
poor at forming intermediate water (well, the MetOffice model is, even with
all the tracer diffusion gimicks of the 90's).

What about the N.Pacific? The nutrient peak is shallower than
the 14C peak, I suppose, but how much of the peak is due to water mass age
and how much to a shallow remin. depth?

Any comments on these idle thoughts? 

JonathanP.


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			JONATHAN PALMER
Room H013,			Internet:  JRPalmer@meto.gov.uk
Hadley Centre,			
Met. Office, London Road,	Tel:       +44 (0)1344 854478
Bracknell, RG12 2SZ, UK		Fax:	   +44 (0)1344 854898
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