Smith, S. R., Brolley, J., O'Brien, J. J., & Tartaglione, C. A. (2007). ENSO's Impact on Regional U.S. Hurricane Activity. J. Climate , 20 (7), 1404–1414.
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.
Stallard, A. (2017). Comparing SAMOS Document Search Performance Between Apache Solr and Neo4j . Master's thesis, Florida State University, Tallahassee, FL.
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.
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.
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.
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.
Stukel, M. R., & Kelly, T. B. The carbon: 234Thorium ratios of sinking particles in the California current ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model. Marine Chemistry , .
Stukel, M. R., & Kelly, T. B. (2019). The carbon: (234) Thorium ratios of sinking particles in the California current ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model. Marine Chemistry , 212 , 1–15.
Abstract: Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon: thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.
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.
