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Dryad

Mini mooring and Wirewalker data collected over the Southern California Bight during winter 2020

Zheng, Bofu1; Lucas, Andrew1; Send, Uwe1; Davis, Kristen2; Franks, Peter1

Published Mar 22, 2026 on Dryad. https://doi.org/10.5061/dryad.34tmpg4zn

Data files

Mar 22, 2026 version files 42.04 MB

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Abstract

Wind-driven coastal upwelling delivers nutrient to the surface waters and enhances primary productivity. In contrast, downwelling transports nutrient-depleted water away from the surface and is usually presumed to decrease primary production. Here, we show that processes during downwelling can actually pump nutrients into previously nutrient-depleted subsurface layers to fuel primary production. Our in-situ data collected from the Southern California Bight showed that downwelling-favorable winds deepened near-surface isopycnals to the bottom boundary layer, followed by a rapid nitrate increase (4 uM within days) on those isopycnals. This increase in nitrate and changes in temperature and salinity were consistent with elevated diapycnal mixing. Excess nitrate was subsequently advected from the boundary into the ocean interior, replenishing offshore concentrations. Together, these findings reveal a mechanism of nutrient redistribution by wind forcing, marginal mixing, and along-isopycnal transport, highlighting the importance of bottom boundary layer mixing and lateral exchange to nutrient dynamics in wind-forced regions.