Gull’s-eye View: Evolution of the Surface Expression of a River Plume Front

James Herbert Leidhold1, Daniel G MacDonald2, Nikiforos Delatolas3, Ágata Piffer Braga4, Louis Goodman5, Michael M Whitney6, Kimberly Huguenard7, Kelly L Cole8 and Preston Spicer7, (1)UMASS Dartmouth, Civil and Environmental Engineering, N. Dartmouth, MA, United States, (2)U Mass/Dartmouth-Est&Ocean Sci, Fairhaven, MA, United States, (3)Earth Resources Technology Inc., Silver Spring, MD, United States, (4)University of Massachusetts Dartmouth, New Bedford, MA, United States, (5)University of Massachusetts Da, New Bedford, MA, United States, (6)University of Connecticut, Marine Sciences, Groton, CT, United States, (7)University of Maine, Orono, ME, United States, (8)University of Maine, School of Marine Sciences, Walpole, ME, United States
Abstract:
Fronts are common features in the ocean at the boundaries between distinct water masses, and typically propagate as one water mass overtakes another, generally due to buoyancy driven pressure gradients. Fronts are typically characterized by an irregular structure at distinct spatial and temporal scales, often referred to as clefts and lobes in the gravity current literature. This study focuses on the Connecticut River plume front, which discharges into the highly tidal flow of Long Island Sound. Not only are river plume fronts important in affecting the distribution of terrestrially derived constitutents in the coastal ocean, they can also be scaled up in order to shed light on the dynamics of larger-scale ocean fronts. In many cases, a front can be tracked by bands of foam and detritus which form due to a frontal convergence zone. Accurately tracking long sections of a front is possible by harnessing an Unmanned Aircraft System (UAS). This study utilizes a UAS equipped with a stabilized 4k resolution video camera, as well as a multitude of on-board sensors which supply metadata, including pitch, roll, yaw, latitude and longitude, allowing for video and pictures to be accurately georectified. This study tracks the propagation of the nose of the front and evolution of frontal instabilities over approximately 4 to 5 hours after discharge from the river mouth. The surface expression of these instabilities is related to the dynamics, including downwelling, upwelling and mixing processes, occurring at the front, and the broad scale of data accessible from the UAS can provide a dynamical context for more focused in-situ observations of frontal dynamics. Further, the study will include spatial, temporal, and hydrographic data taken from multiple bucket drifters and a drifting buoy placed into the front which will allow for further analysis. The goal of this study is to characterize frontal propagation and the horizontal length scales (both cross front and along front) and timescales of instabilities along the front.
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