A Field Study of Surface Nutrient Enrichment in the California Current
Final technical rept. 1 Jan 95-30 Sep 99
SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE LIFE RESEARCH GROUP
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The research detailed the vertical, horizontal, and temporal structure of surface nutrient enrichment in the southern California Current. High-resolution data shows what was once thought to be a single unique characteristic of some nutrient profiles is two separate features, one in the mixed layer, the other in the pycnocline. A In a mixed layer, nutrients can increase from at or above the pycnocline to the surface, so that a physically isotropic mixed layer displays surface nutrient enrichment SNE. B Beneath a mixed layer with isotropic nutrients, nutrients often decrease with depth above the nutricline, thus forming a subsurface nutrient reduction SNR. Both SNE and SNR can be present in the same profile. In the base of the mixed layer, there is often an isonutrient layer between the two features. With no mixed layer, SNR can be present. Occurrences of SNE and SNR are independent, indicating they have different causes. We propose a new mechanism for the formation of SNE--wind mixing after stable physical conditions redistributes nutrients regenerated in thin layers of intense biological activity in the mixed layer. The data also suggest SNR is often caused by subduction of nutrient-poor waters, as well as by nutrient consumption exceeding supply.
- Physical and Dynamic Oceanography