Skip to Main content Skip to Navigation
Journal articles

Optical effect on the nitracline in a coastal upwelling area

Abstract : The transport of nitrate into the euphotic zone is an important regulator of primary production. This transport is facilitated by physical processes that involve the depth and the steepness of the nitracline, but transport is complicated by the dynamical nature of the euphotic zone. Here we derive an analytical model that predicts two optical effects of the euphotic zone on the nitracline: the nitracline depth should vary inversely with light attenuation for downwelling irradiance, and the nitracline steepness should be directly proportional to light attenuation. We show that observations of nitrate and Secchi depth, which have been obtained over 21 yr in the coastal upwelling region off Southern California (CalCOFI area), are consistent with these predictions. Chlorophyll a measurements also indicate an optical signature in the nitracline: while the amount of chlorophyll correlated poorly with the nitracline depth, the nitracline depth correlated strongly with the optical effect of chlorophyll, and the nonlinear nature of this relationship was consistent with the model prediction. These optical effects on the nitracline may involve positive feedback mechanisms with phytoplankton production that have implications for interpretation and modeling of primary production.
Document type :
Journal articles
Complete list of metadatas

https://hal.univ-brest.fr/hal-00635501
Contributor : Adminhal Univbrestbu <>
Submitted on : Tuesday, October 25, 2011 - 2:23:33 PM
Last modification on : Tuesday, June 30, 2020 - 3:16:01 PM

Links full text

Identifiers

Collections

Citation

Dag Aksnes, Mark Ohman, Pascal Rivière. Optical effect on the nitracline in a coastal upwelling area. Limnology and Oceanography, Association for the Sciences of Limnology and Oceanography, 2007, 52 (3), pp.1179-1187. ⟨10.4319/lo.2007.52.3.1179⟩. ⟨hal-00635501⟩

Share

Metrics

Record views

907