Day 4

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Paper title Observing river plume dynamics from space
Authors
  1. Avelon Gerritsma TU Delft / Deltares Speaker
  2. Martin Verlaan TU Delft / Deltares
  3. Lennart Keyzer Tu Delft
  4. Julie Pietrzak TU Delft
Form of presentation Poster
Topics
  • A7. Hydrology and Water Cycle
    • A7.01 Inland Water Storage and Runoff: Modeling, In Situ Data and Remote Sensing
Abstract text River plumes are well-visible on satellite imagery as sharp fronts (optical and thermal IR), resulting from the different properties of river vs ocean water bodies (e.g. temperature, salinity, sediment concentration). They serve as the link between river and ocean, transporting freshwater, (fine) sediments, nutrients and human waste (Halpern et al., 2008, Dagg et al., 2004; Joordens et al., 2001). Understanding the river plume dynamics will help to understand the transport of these substances. Moreover, it can provide valuable information on the river system. River plumes are formed by river freshwater entering the ocean, creating buoyant bodies of brackish water overlaying saltier sea water. The local buoyancy input of river freshwater interacts with tides, wind and waves. When the freshwater buoyancy is dominant, the system is stratified. This can be detected on sea surface temperature (SST) images during summer as a sharp front, as the top layer of freshwater heathens faster than the surrounding sea water (Pietrzak et al., 2011). Oppositely, when the mixing processes (tides, wind, waves) are dominant, the system will be well-mixed. This results in more gradual changes in temperature and salinity. For tide-dominated systems, freshwater pulses enter the ocean during ebb, resulting in multiple strong fronts on optical images. Wind and tides govern the propagation speed of these fronts, their thickness and direction in which they move (Rijnsburger et al., 2018). Consequently, fronts and their propagation can give information about the dynamics of the system and which processes are dominant. As water properties like salinity, temperature and sediment concentration determine the water colour, we can detect fronts on optical images. In this research, we study the potential relationship between fronts and river plume characteristics. First, we are developing the algorithms to detect fronts on satellite images. We hypothesize that the scale of the river plume can be related to the river discharge. We investigate this relationship using discharge data and the detected fronts as measure for the scale of the river plume. Next, we will investigate methods for coupling fronts detected on satellite images to fronts in a 3D numerical model of a river plume. We hypothesize that model performance can be improved by using the information retrieved from satellite images. Information-sparse river systems can profit in particular, where the satellite images can provide a valuable source of information to improve the modelling and understanding of the river plume dynamics. In this research we make a first step towards this goal, by investigating possibilities to retrieve (quantitative) information from satellite images and methods to couple the information to model output.

References
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Joordens, J.C.A., A. J. Souza, and A. Visser (2001), The influence of tidal straining and
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Pietrzak, J. D., de Boer, G. J., & Eleveld, M. A. (2011). Mechanisms controlling the intra-annual mesoscale variability of SST and SPM in the southern North Sea. Continental Shelf Research, 31(6), 594–610. https://doi.org/10.1016/j.csr.2010.12.014

Rijnsburger, S., Flores, R. P., Pietrzak, J. D., Horner-Devine, A. R., & Souza, A. J. (2018). The Influence of Tide and Wind on the Propagation of Fronts in a Shallow River Plume. Journal of Geophysical Research: Oceans, 123(8), 5426–5442. https://doi.org/10.1029/2017JC013422

Rijnsburger, S. (2021). On the dynamics of tidal plume fronts in the Rhine Region of Freshwater Influence. https://doi.org/10.4233/uuid:279260a6-b79e-4334-9040-e130e54b9360