Aircraft remote sensing of phytoplankton spatial patterns during the 1989 Joint Global Ocean Flux Study (JGOFS) North Atlantic bloom experiment

Mesoscale phytoplankton chlorophyll variability near the Joint Global Ocean Flux study sites along the 20 W meridian at 34 N, 47 N, and 59 N is discussed. The NASA P-3 aircraft and the Airborne Oceanographic Lidar (AOL) system provides remote sensing support for the North Atlantic Bloom Experiment. The principal instrument of the AOL system is the blue-green laser that stimulates fluorescence from photoplankton chlorophyll, the principal photosynthetic pigment. Other instruments on the NASA P-3 aircraft include up- and down-looking spectrometers, PRT-5 for infrared measurements to determine sea surface temperature, and a system to deploy and record AXBTs to measure subsurface temperature structure

Seasonal and ENSO variability in global ocean phytoplankton chlorophyll derived from 4 years of SeaWiFS measurements

The 4‐year, calibrated SeaWiFS data set provides a means to determine seasonal and other sources of phytoplankton variability on global scales, which is an important component of the total variability associated with ocean biological and biogeochemical processes. We used empirical orthogonal function (EOF) analysis on a 4‐year time series of global SeaWiFS chlorophyll a measurements to quantify the major seasonal (as well as the late El Niño and La Niña phase of the 1997–1998 ENSO) signals in phytoplankton biomass between 50°S and 50°N, and then a second analysis to quantify summer patterns at higher latitudes. Our results help place regional satellite chlorophyll variability within a global perspective. Among the effects we resolved are a 6‐month phase shift in maximum chlorophyll a concentrations between subtropical (winter peaks) and subpolar (spring‐summer peaks) waters, greater seasonal range at high latitudes in the Atlantic compared to the Pacific, an interesting phasing between spring and fall biomass peaks at high latitudes in both hemispheres, and the effects of the 1998 portion of the 1997–1998 ENSO cycle in the tropics. Our EOF results show that dominant seasonal and ENSO effects are captured in the first six of a possible 184 modes, which explain 67% of the total temporal variability associated with the global mean phytoplankton chlorophyll pattern in our smoothed data set. The results also show that the time (seasonal)/space (zonal) patterns between the ocean basins and between the hemispheres are similar, albeit with some key differences. Finally, the dominant global patterns are consistent with the results of ocean models of seasonal dynamics based on seasonal changes to the heating and cooling (stratification/destratification) cycles of the upper ocean

The Cost of Dispersal: Predation as a Function of Movement and Site Familiarity in Ruffed Grouse

Ecologists often assume that dispersing individuals experience increased predation risk owing to increased exposure to predators while moving. To test the hypothesis that predation risk is a function of movement distance or rate of movement, we used radio-telemetry data collected from 193 ruffed grouse (Bonasa umbellus) during 1996–1999 in southeastern Ohio. Cox’s proportional hazards model was used to examine whether the risk of predation was affected by the rate of movement and site familiarity. We found evidence indicating that increased movement rates may increase the risk of predation for adult birds but not juveniles. We also found juvenile and adult birds inhabiting unfamiliar space were consistently at a much higher risk of predation (three to 7.5 times greater) than those in familiar space. Our results indicate that although movement itself may have some effect on the risk of being preyed upon, moving through unfamiliar space has a much greater effect on risk for ruffed grouse. This supports the hypothesis that increased predation risk may be an important cost of dispersal for birds.This work was funded by the Ohio Department of Natural Resources, Division of Wildlife and supported by the Department of Evolution, Ecology, and Organismal Biology and the Aquatic Ecology Laboratory at the Ohio State University

Gulf Stream Frontal Eddy Influence on Productivity of the Southeast United States Continental Shelf

Weekly period meanders and eddies are persistent features of Gulf Stream frontal dynamics from Miami, Florida, to Cape Hatteras, North Carolina. Satellite imagery and moored current and temperature records reveal a spatial pattern of preferred regions for growth and decay of frontal disturbances. Growth regions occur off Miami, Cape Canaveral, and Cape Fear due to baroclinic instability, and decay occurs in the confines of the Straits of Florida between Miami and Palm Beach, between 30° and 32°N where the stream approaches the topographic feature known as the Charleston bump and between 33°N and Cape Hatteras. Eddy decay regions are associated with elongation of frontal features, offshore transport of momentum and heat, and onshore transport of nutrients. Onshore transport of new nitrogen from the nutrient-bearing strata beneath the Gulf Stream indicates that frontal eddies serve as a nutrient pump for the shelf. New nitrogen flux to the shelf due to Gulf Stream input could support new production of 7.4 x 1012 g C yr-1 or about 8 million tons carbon per year if all nitrate were utilized. Calculations indicate that approximately 70% of this potential new production is realized, yielding an annual new production for the outer shelf of 4.3 x 1012gC

A Satellite Assessment of Environmental Controls of Phytoplankton Community Size Structure

Phytoplankton play a key role as the base of the marine food web and a crucial component in the Earth\u27s carbon cycle. There have been a few regional studies that have utilized satellite‐estimated phytoplankton functional type products in conjunction with other environmental metrics. Here we expand to a global perspective and ask, what are the physical drivers of phytoplankton composition variability? Using a variety of satellite‐observed ocean color products and physical properties spanning 1997–2015, we characterize spatial and temporal variability in phytoplankton community size structure in relation to satellite‐based physical drivers. We consider the relationships globally and by major thermal regimes (cold and warm), dominant size distribution, and chlorophyll concentration variability. Globally, euphotic depth is the most important parameter driving phytoplankton size variability and also over the majority of the high‐latitude ocean and the central gyres. In all other regions, size variability is driven by a balance of light and mode of nutrient delivery. We investigated the relationship between size composition and chlorophyll concentration and the physical drivers through correlation analysis. Changes in size composition over time are regionally varying and explained by temporal shifts in the varying physical conditions. These changes in phytoplankton size composition and the varying underlying physical drivers will ultimately impact carbon export and food web processes in our changing ocean

Modeling of Turbulent Free Shear Flows

The modeling of turbulent free shear flows is crucial to the simulation of many aerospace applications, yet often receives less attention than the modeling of wall boundary layers. Thus, while turbulence model development in general has proceeded very slowly in the past twenty years, progress for free shear flows has been even more so. This paper highlights some of the fundamental issues in modeling free shear flows for propulsion applications, presents a review of past modeling efforts, and identifies areas where further research is needed. Among the topics discussed are differences between planar and axisymmetric flows, development versus self-similar regions, the effect of compressibility and the evolution of compressibility corrections, the effect of temperature on jets, and the significance of turbulent Prandtl and Schmidt numbers for reacting shear flows. Large eddy simulation greatly reduces the amount of empiricism in the physical modeling, but is sensitive to a number of numerical issues. This paper includes an overview of the importance of numerical scheme, mesh resolution, boundary treatment, sub-grid modeling, and filtering in conducting a successful simulation

A Comparison of Three Navier-Stokes Solvers for Exhaust Nozzle Flowfields

A comparison of the NPARC, PAB, and WIND (previously known as NASTD) Navier-Stokes solvers is made for two flow cases with turbulent mixing as the dominant flow characteristic, a two-dimensional ejector nozzle and a Mach 1.5 elliptic jet. The objective of the work is to determine if comparable predictions of nozzle flows can be obtained from different Navier-Stokes codes employed in a multiple site research program. A single computational grid was constructed for each of the two flows and used for all of the Navier-Stokes solvers. In addition, similar k-e based turbulence models were employed in each code, and boundary conditions were specified as similarly as possible across the codes. Comparisons of mass flow rates, velocity profiles, and turbulence model quantities are made between the computations and experimental data. The computational cost of obtaining converged solutions with each of the codes is also documented. Results indicate that all of the codes provided similar predictions for the two nozzle flows. Agreement of the Navier-Stokes calculations with experimental data was good for the ejector nozzle. However, for the Mach 1.5 elliptic jet, the calculations were unable to accurately capture the development of the three dimensional elliptic mixing layer

Multi-Antenna Vision-and-Inertial-Aided CDGNSS for Micro Aerial Vehicle Pose Estimation

A system is presented for multi-antenna carrier phase differential GNSS (CDGNSS)-based pose (position and orientation) estimation aided by monocular visual measurements and a smartphone-grade inertial sensor. The system is designed for micro aerial vehicles, but can be applied generally for low-cost, lightweight, high-accuracy, geo-referenced pose estimation. Visual and inertial measurements enable robust operation despite GNSS degradation by constraining uncertainty in the dynamics propagation, which improves fixed-integer CDGNSS availability and reliability in areas with limited sky visibility. No prior work has demonstrated an increased CDGNSS integer fixing rate when incorporating visual measurements with smartphone-grade inertial sensing. A central pose estimation filter receives measurements from separate CDGNSS position and attitude estimators, visual feature measurements based on the ROVIO measurement model, and inertial measurements. The filter's pose estimates are fed back as a prior for CDGNSS integer fixing. A performance analysis under both simulated and real-world GNSS degradation shows that visual measurements greatly increase the availability and accuracy of low-cost inertial-aided CDGNSS pose estimation.Aerospace Engineering and Engineering Mechanic

The effect of summertime shelf break upwelling on nutrient flux in southeastern United States continental shelf waters

Gulf Stream-induced upwelling at the shelf break of the South Atlantic Bight (SAB) presents water which, in summer, can intrude onto the continental shelf. In July 1979, an XBT survey of the continental shelf revealed such an intrusion of cold water off St. Augustine, Florida. From weekly mappings, it was determined that Gulf Stream water \u3c22.5°C covered 3280 km2 and occupied 38 km3 shoreward of the 42 m isobath. Using temperature and nitrate distributions and the T°C:NO3 relationship, we determined that 3200 metric tons of nitrate-nitrogen were advected into the study area. Net nitrate-nitrogen fluxes were 32 μmoles · m−2 · sec−1 across the 42 m isobath and 30 μmoles · m−2 · sec−1 across the 30 m isobath.The advection of nitrate-enriched water into the photic zone caused a dramatic increase in phytoplankton biomass. The decreasing nitrate concentrations correlated with chlorophyll increases indicating phytoplankton production was mainly at the expense of nitrate advected into the area. Prior to the intrusion, production was likely supported by regenerated nutrients.Summertime intrusions supply an estimated 2.9 × 104 mtons NO3-N · yr−1 to the middle shelf area of the southern SAB and are thus a major source of nitrogen to that area

POTENTIAL BIRD REPELLENTS TO REDUCE BIRD DAMAGE TO LETTUCE SEED AND SEEDLINGS

The authors evaluated the effectiveness of ReJeX-iT® AG-145, Mesurol®, activated charcoal, lime, and fipronil to reduce homed lark damage to lettuce seeds and seedlings. In Experiment 1, homed larks consumed significantly more feed mixture (50:50 grains and lettuce seed) than untreated clay-coated lettuce seed in a three-day choice-test. In Experiment 2, where clay-coated lettuce seed was treated with ReJeX-iT® AG- 145, Mesurol®, activated charcoal, or lime, there was no significant difference in consumption of untreated clay-coated lettuce seed and treated clay-coated lettuce seed. Homed larks consumed insignificant amounts of all seed treatments including untreated coated lettuce seed. In this experiment homed larks lost an average of 28 % of their body weight over the three-day test period. It was concluded that the clay seed coating alone reduced damage significantly. In the aviary test, flats of sprouting lettuce seedlings were sprayed with Mesurol® (4 kg/ha), ReJeX-iT® AG-145 (64 kg/ha), lime (32 kg/ha), activated charcoal (32 kg/ha), and fipronil(4 kg/ha). Mesurol®, ReJeX-iT® AG-145, and lime significantly reduced consumption of lettuce seedlings over a four-day test period. Even though lime significantly reduced consumption, homed larks still consumed over 50% of the available lettuce seedlings. Field evaluations are warranted with Mesurol® and ReJeX-iT® AG-145