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Smith, S. R., Green, P. M., Leonardi, A. P., & O'Brien, J. J. (1998). Role of Multiple-Level Tropospheric Circulations in Forcing ENSO Winter Precipitation Anomalies. Mon. Wea. Rev., 126(12), 3102–3116.
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Smith, S. R., & O'Brien, J. J. (2001). Regional Snowfall Distributions Associated with ENSO: Implications for Seasonal Forecasting. Bull. Amer. Meteor. Soc., 82(6), 1179–1191.
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Stallard, A. (2017). Comparing SAMOS Document Search Performance Between Apache Solr and Neo4j. Master's thesis, Florida State University, Tallahassee, FL.
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Stauffer, C. L. (2018). Air-sea coupling dependency on sea surface temperature fronts as observed by research vessel data. Bachelor's thesis, Florida State University, Tallahassee, FL.
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Steffen, J., & Bourassa, M. (2018). Barrier Layer Development Local to Tropical Cyclones based on Argo Float Observations. J. Phys. Oceanogr., 48(9), 1951–1968.
Abstract: The objective of this study is to quantify barrier layer development due to tropical cyclone (TC) passage using Argo float observations of temperature and salinity. To accomplish this objective, a climatology of Argo float measurements is developed from 2001 to 2014 for the Atlantic, eastern Pacific, and central Pacific basins. Each Argo float sample consists of a prestorm and poststorm temperature and salinity profile pair. In addition, a no-TC Argo pair dataset is derived for comparison to account for natural ocean state variability and instrument sensitivity. The Atlantic basin shows a statistically significant increase in barrier layer thickness (BLT) and barrier layer potential energy (BLPE) that is largely attributable to an increase of 2.6 m in the post-TC isothermal layer depth (ITLD). The eastern Pacific basin shows no significant changes to any barrier layer characteristic, likely due to a shallow and highly stratified pycnocline. However, the near-surface layer freshens in the upper 30 m after TC passage, which increases static stability. Finally, the central Pacific has a statistically significant freshening in the upper 20-30 m that increases upper-ocean stratification by similar to 35%. The mechanisms responsible for increases in BLPE vary between the Atlantic and both Pacific basins; the Atlantic is sensitive to ITLD deepening, while the Pacific basins show near-surface freshening to be more important in barrier layer development. In addition, Argo data subsets are used to investigate the physical relationships between the barrier layer and TC intensity, TC translation speed, radial distance from TC center, and time after TC passage.
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Stewart, M. L. (2007). Cyclogenesis and Tropical Transition in Frontal Zones. Master's thesis, Florida State University, Tallahassee, FL.
Abstract: Tropical cyclones can form from many different precursors, including baroclinic systems. The process of an extratropical system evolving into a warm core tropical cyclone is defined by Davis and Bosart (2004) as a Tropical Transition (TT) with further classification of systems into Weak Extratropical Cylclones (WEC) and Strong Extratropical Cyclones (SEC). It is difficult to predict which systems will make the transition and which will not, but the description of a common type of TT occurring along a front will aid forecasters in identifying systems that might undergo TT. A wind speed and SST relationship thought to be necessary for this type of transition is discussed. QuikSCAT and other satellite data are used to locate TT cases forming along fronts and track their transformation into tropical systems. Frontal TT is identified as a subset of SEC TT and the evolution from a frontal wave to a tropical system is described in five stages. A frontal wave with stronger northerly wind and weaker southerly wind is the first stage in the frontal cyclogenesis. As the extratropical cyclogenesis continues in the next two stages, bent back warm front stage and instant occlusion stage, the warmer air of the bent back front becomes surrounded by cooler air . Next, in the subtropical stage the latent heat release energy from the ocean surface begins ascent and forms a shallow warm core. As the energy from surface heat fluxes translates to convection within the system, the warm core extends further into the upper levels of the atmosphere in the final, tropical stage of TT. Model data from MM5 simulations of three storms, Noel (2001), Peter (2003) and Gaston (2004) are analyzed to illustrate the five stages of frontal TT. Noel is found to have the most baroclinic origin of the three and Gaston the least.
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Stukel, M. R., & Barbeau, K. A. (2020). Investigating the Nutrient Landscape in a Coastal Upwelling Region and Its Relationship to the Biological Carbon Pump. Geophys. Res. Lett., 47(6), e2020GL087351.
Abstract: We investigated nutrient patterns and their relationship to vertical carbon export using results from 38 Lagrangian experiments in the California Current Ecosystem. The dominant mode of variability reflected onshore-offshore nutrient gradients. A secondary mode of variability was correlated with silica excess and dissolved iron and likely reflects regional patterns of iron-limitation. The biological carbon pump was enhanced in high nutrient and Fe-stressed regions. Patterns in the nutrient landscape proved to be better predictors of the vertical flux of sinking particles than contemporaneous measurements of net primary production. Our results suggest an important role for Fe-stressed diatoms in vertical carbon flux. They also suggest that either preferential recycling of N or non-Redfieldian nutrient uptake by diatoms may lead to high PO:NO and Si(OH):NO ratios, following export of P- and Si-enriched organic matter. Increased export following Fe-stress may partially explain inverse relationships between net primary productivity and export efficiency.
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Stukel, M. R., Biard, T., Krause, J. W., & Ohman, M. D. (2018). Large Phaeodaria in the twilight zone: Their role in the carbon cycle. Association for the Sciences of Limnology and Oceanography, .
Abstract: Advances in in situ imaging allow enumeration of abundant populations of large Rhizarians that compose a substantial proportion of total mesozooplankton biovolume. Using a quasi-Lagrangian sampling scheme, we quantified the abundance, vertical distributions, and sinking‐related mortality of Aulosphaeridae, an abundant family of Phaeodaria in the California Current Ecosystem. Inter‐cruise variability was high, with average concentrations at the depth of maximum abundance ranging from < 10 to > 300 cells m−3, with seasonal and interannual variability associated with temperature‐preferences and regional shoaling of the 10°C isotherm. Vertical profiles showed that these organisms were consistently most abundant at 100�150 m depth. Average turnover times with respect to sinking were 4.7�10.9 d, equating to minimum in situ population growth rates of ~ 0.1�0.2 d−1. Using simultaneous measurements of sinking organic carbon, we find that these organisms could only meet their carbon demand if their carbon : volume ratio were ~ 1 μg C mm−3. This value is substantially lower than previously used in global estimates of rhizarian biomass, but is reasonable for organisms that use large siliceous tests to inflate their cross‐sectional area without a concomitant increase in biomass. We found that Aulosphaeridae alone can intercept > 20% of sinking particles produced in the euphotic zone before these particles reach a depth of 300 m. Our results suggest that the local (and likely global) carbon biomass of Aulosphaeridae, and probably the large Rhizaria overall, needs to be revised downwards, but that these organisms nevertheless play a major role in carbon flux attenuation in the twilight zone.
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Stukel, M. R., Decima, M., & Kelly, T. B. (2018). A new approach for incorporating 15N isotopic data into linear inverse ecosystem models with Markov Chain Monte Carlo sampling. PLoS One, 13(6), e0199123.
Abstract: Oceanographic field programs often use delta15N biogeochemical measurements and in situ rate measurements to investigate nitrogen cycling and planktonic ecosystem structure. However, integrative modeling approaches capable of synthesizing these distinct measurement types are lacking. We develop a novel approach for incorporating delta15N isotopic data into existing Markov Chain Monte Carlo (MCMC) random walk methods for solving linear inverse ecosystem models. We test the ability of this approach to recover food web indices (nitrate uptake, nitrogen fixation, zooplankton trophic level, and secondary production) derived from forward models simulating the planktonic ecosystems of the California Current and Amazon River Plume. We show that the MCMC with delta15N approach typically does a better job of recovering ecosystem structure than the standard MCMC or L2 minimum norm (L2MN) approaches, and also outperforms an L2MN with delta15N approach. Furthermore, we find that the MCMC with delta15N approach is robust to the removal of input equations and hence is well suited to typical pelagic ecosystem studies for which the system is usually vastly under-constrained. Our approach is easily extendable for use with delta13C isotopic measurements or variable carbon:nitrogen stoichiometry.
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Stukel, M. R., Décima, M., Landry, M. R., & Selph, K. E. (2018). Nitrogen and isotope flows through the Costa Rica Dome upwelling ecosystem: The crucial mesozooplankton role in export flux. Global Biogeochemical Cycles, 32(12), 1815–1832.
Abstract: The Costa Rica Dome (CRD) is an open-ocean upwelling ecosystem, with high biomasses of picophytoplankton (especially Synechococcus), mesozooplankton, and higher trophic levels. To elucidate the food web pathways supporting the trophic structure and carbon export in this unique ecosystem, we used Markov Chain Monte Carlo techniques to assimilate data from four independent realizations of δ15N and planktonic rate measurements from the CRD into steady state, multicompartment ecosystem box models (linear inverse models). Model results present well-constrained snapshots of ecosystem nitrogen and stable isotope fluxes. New production is supported by upwelled nitrate, not nitrogen fixation. Protistivory (rather than herbivory) was the most important feeding mode for mesozooplankton, which rely heavily on microzooplankton prey. Mesozooplankton play a central role in vertical nitrogen export, primarily through active transport of nitrogen consumed in the surface layer and excreted at depth, which comprised an average 36-46% of total export. Detritus or aggregate feeding is also an important mode of resource acquisition by mesozooplankton and regeneration of nutrients within the euphotic zone. As a consequence, the ratio of passively sinking particle export to phytoplankton production is very low in the CRD. Comparisons to similar models constrained with data from the nearby equatorial Pacific demonstrate that the dominant role of vertical migrators to the biological pump is a unique feature of the CRD. However, both regions show efficient nitrogen transfer from mesozooplankton to higher trophic levels (as expected for regions with large fish, cetacean, and seabird populations) despite the dominance of protists as major grazers of phytoplankton.
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