Abstract
Dye release experiments conducted in the seasonal pycnocline of the Sargasso Sea in June 2011 yield diapycnal and isopycnal diffusivities of order Kz = 2-5 x 10-6 m2 s-1, Kh = 0.5-4 m2 s-1, in strain conditions ranging from 0.1-3 x 10-5 s-1. A shear-strain-diffusion model suggests vertical shear dispersion by low frequency shears and internal waves can only explain a fraction of the observed lateral spreading. A series of shorter (order 6 hrs) experiments surveyed using airborne LIDAR reveal details about the short-term evolution of the dye patches, including multiple instances of sinuous meanders of the patches early in the evolution, and/or evidence of filamentation along their periphery. This suggests weak small-scale (<1 km) differential lateral advection acting on the patches, possibly contributing to enhanced dispersion at later times in the longer experiments. Simple scaling implies an upper bound on the effective lateral diffusivity at the <1 km scale that is nearly an order of magnitude smaller than that at 1-5 km scales.
To further advance the use of lidar for environmental science applications such as these, we have established a new UMass Experimental Center for Environmental Lidar (EXCEL). In brief, EXCEL is a multi-campus center (UMass Lowell, Dartmouth, Boston, and Amherst) that pools expertise among the different UMass campuses in terrestrial, oceanographic, and wind lidar. As part of the Center's oceanographic related activities in particular, we are reaching out to organizations in the region that have interest and/or possible applications related to bathymetric lidar, spatially resolved wave data, water clarity data (e.g. tubidity, phytoplankton concentrations), and/or marsh/wetland/beach/dune/channel topography/bathymetric data. We welcome any opportunities to collaborate with other interested groups on these and related problems.
Presenter Bio
Dr. Sundermeyer is an Associate Professor at the University of Massachusetts Dartmouth. He earned his Ph.D. from the MIT/WHOI Joint Program in Physical Oceanography, and has been studying problems relating to ocean mixing for more than 20 years. His primary research interests include vertical and horizontal mixing processes, dye release and Lagrangian drifter studies, numerical modeling of two- and three-dimensional turbulent flows, numerical modeling of physical and biological interactions.
Publication Date
9-12-2014
Document Type
Presentation
Recommended Citation
Sundermeyer, Miles A., "Observations of Small-Scale Lateral Dispersion in the Ocean and an Introduction to the New UMass Experimental Center for Environmental Lidar (EXCEL)" (2014). Seminars. 151.
https://scholars.unh.edu/ccom_seminars/151