Most studies on buoyant microplastics in the marine environment rely on sea surface sampling. Consequently, microplastic amounts can be underestimated, as turbulence leads to vertical mixing. Models that correct for vertical mixing are based on limited data. In this study we report measurements of the depth profile of buoyant microplastics in the North Atlantic subtropical gyre, from 0 to 5 m d...

We independently manipulated mixing intensity (strong artificial mixing vs. background turbulence) and water-column depth (2 m, 4 m, 8 m, and 12 m) in order to explore their separate and combined effects in a field enclosure experiment. To accentuate the vertical light gradient, enclosures had black walls, resulting in a euphotic depth of only 3.7 m. All enclosures were placed in a well-mixed w...

We study mixing and spreading in a very simple heterogeneous system: a numerical flow cell comprised of two homogeneous porous media separated by a sharp angled interface. The two media have identical porosity, but differing permeability and dispersivity characteristics representing a fine and a coarse medium. We focus on transport in advection-dominated systems as the primary role of the angle...

We present measurements of mixing efficiency in a run-down gravity current created by lock exchange in a channel. Experiments were designed to extend to particularly high Reynolds number (of order 10, based on the current depth), at which mixing is no longer affected significantly by viscosity. Under these conditions, we observe that the run-down density profiles in the channel achieve full sel...

River ecosystems are influenced by contaminants in the water column, in the pore water and adsorbed to sediment particles. When exchange across the sediment-water interface (hyporheic exchange) is included in modeling, the mixing coefficient is often assumed to be constant with depth below the interface. Novel fiber-optic fluorometers have been developed and combined with a modified EROSIMESS s...

This research (1) integrated a fluorescent dye injection and monitoring system for measuring the mixing of a fluorescent dye tracer (fluorescein) in permeable (sandy) sediments with a cabled ocean observatory, Kilo Nalu, Oahu, Hawaii, and (2) used this system to conduct remotely controlled in situ measurements of wave-enhanced porewater mixing in a physically well-characterized wave-dominated s...

Over the 20th century, surface water temperatures have increased in many lake ecosystems around the world, but long-term trends in the vertical thermal structure of lakes remain unclear, despite the strong control that thermal stratification exerts on the biological response of lakes to climate change. Here we used both neo- and paleoecological approaches to develop a fossil-based inference mod...

Mixing has long been recognized as having an important role in influencing underwater light and nutrient budgets and thus regulating phytoplankton bloom. Mixing related to stratification and destratification is a key parameter of the physical environment that can control the timing and magnitude of blooms. Here we use a high-resolution three-dimensional biogeochemical model in the Mid-Atlantic ...

Major deep-convection activity in the northwestern Mediterranean during winter 2005 triggered formation of a complex anomalous deep-water structure that substantially modified properties Western deep layers. Since then, evolution this thermohaline structure, so-called Transition (WMT), has been traced through regularly sampled hydrographic station located on outer continental slope Minorca Isla...