Publications

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2017
Stukel, MR, Aluwihare LI, Barbeau KA, Chekalyuk AM, Goericke R, Miller AJ, Ohman MD, Ruacho A, Song H, Stephens BM, Landry MR.  2017.  Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction. Proceedings of the National Academy of Sciences of the United States of America. 114:1252-1257.   10.1073/pnas.1609435114   AbstractWebsite

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from U-238:Th-234 disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg C.m(-2).d(-1)) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front wasmechanistically linked to Fe-stressed diatoms and high-mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional similar to 225 mg C.m(-2).d(-1) was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems.

2013
Ohman, MD, Barbeau K, Franks PJS, Goericke R, Landry MR, Miller AJ.  2013.  Ecological transitions in a coastal upwelling ecosystem. Oceanography. 26:210-219. AbstractWebsite

The southern California Current Ecosystem (CCE) is a dynamic eastern boundary current ecosystem that is forced by ocean-atmosphere variability on interannual, multidecadal, and long-term secular time scales. Recent evidence suggests that apparent abrupt transitions in ecosystem conditions reflect linear tracking of the physical environment rather than oscillations between alternative preferred states. A space-for-time exchange is one approach that permits use of natural spatial variability in the CCE to develop a mechanistic understanding needed to project future temporal changes. The role of (sub)mesoscale frontal systems in altering rates of nutrient transport, primary and secondary production, export fluxes, and the rates of encounters between predators and prey is an issue central to this pelagic ecosystem and its future trajectory because the occurrence of such frontal features is increasing.