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Ocean Science An interactive open-access journal of the European Geosciences Union

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Ocean Sci., 12, 1003-1011, 2016
http://www.ocean-sci.net/12/1003/2016/
doi:10.5194/os-12-1003-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
25 Aug 2016
Impact of vertical and horizontal advection on nutrient distribution in the southeast Pacific
Bàrbara Barceló-Llull1, Evan Mason2, Arthur Capet3, and Ananda Pascual2 1Universidad de Las Palmas de Gran Canaria, ULPGC, Las Palmas de Gran Canaria, Spain
2Institut Mediterrani d'Estudis Avançats, IMEDEA (CSIC-UIB), Mallorca, Spain
3CNR, OGS, Trieste, Italy
Abstract. An innovative approach is used to analyze the impact of vertical velocities associated with quasi-geostrophic (QG) dynamics on the redistribution and uptake of nitrate in the southeast Pacific (SEP). A total of 12 years of vertical and horizontal currents are derived from an observation-based estimate of the ocean state. Horizontal velocities are obtained through the application of thermal wind balance to weekly temperature and salinity fields. Vertical velocities are estimated by integration of the QG omega equation. Seasonal variability of the synthetic vertical velocity and kinetic energy associated with the horizontal currents is coincident, with peaks in austral summer (November–December) in accord with published observations. The impact of vertical velocity on SEP nitrate uptake rates is assessed by using two Lagrangian particle tracking experiments that differ according to vertical forcing (ω = ωQG vs. ω = 0). From identical initial distributions of nitrate-tagged particles, the Lagrangian results show that vertical motions induce local increases in nitrate uptake reaching up to 30 %. Such increases occur in low uptake regions with high mesoscale activity. Despite being weaker than horizontal currents by a factor of up to 10−4, vertical velocity associated with mesoscale activity is demonstrated to make an important contribution to nitrate uptake, hence productivity, in low uptake regions.

Citation: Barceló-Llull, B., Mason, E., Capet, A., and Pascual, A.: Impact of vertical and horizontal advection on nutrient distribution in the southeast Pacific, Ocean Sci., 12, 1003-1011, doi:10.5194/os-12-1003-2016, 2016.
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Short summary
Vertical velocity in the ocean makes an important contribution to the modulation of marine ecosystems through its impact on fluxes of nutrients and phytoplankton. Here, we estimate full 3-D current velocity fields from an observation-based data product. The 3-D currents are used to force a set of particle-tracking (Lagrangian) experiments. The Lagrangian results show that vertical motions induce local increases in nitrate uptake reaching up to 30 %.
Vertical velocity in the ocean makes an important contribution to the modulation of marine...
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