Title

3D Dynamics of Freshwater Lenses in the Near-Surface Layer of the Tropical Ocean

Event Name/Location

European Geosciences Union General Assembly 2015 / Vienna Austria

Document Type

Lecture

Publication Date

4-2015

Abstract

Convective rains in the Intertropical Convergence Zone (ITCZ) produce lenses of freshened water on the ocean surface. These lenses are localized in space and typically involve both salinity and temperature anomalies. Due to significant density anomalies, strong pressure gradients develop, which result in lateral spreading of freshwater lenses in a form resembling gravity currents. Gravity currents inherently involve three-dimensional dynamics. As a type of organized structure, gravity currents in the upper layer of the ocean may also interact with, and be shaped by, the ambient oceanic environment and atmospheric conditions. Among the important factors are the background stratification, wind stress, wind/wave mixing and spatially coherent organized motions in the nearsurface layer of the ocean. Under certain conditions, a resonant interaction between a propagating freshwater lens and internal waves in the underlying pycnocline (e.g., barrier layer) may develop, whereas interaction with wind stress may produce an asymmetry in the freshwater lens and associated mixing. These two types of interactions working in concert may explain the series of sharp frontal interfaces, which have been observed in association with freshwater lenses during TOGA COARE. In this work, we have conducted a series of numerical experiments using computational fluid dynamics tools. These numerical simulations were designed to elucidate the relationship between vertical mixing and horizontal advection of salinity under various environmental conditions and potential impact on the Aquarius and SMOS satellite image formation. Available near-surface data from field experiments served as a guidance for numerical simulations. The results of this study indicate that 3D dynamics of freshwater lenses are essential within a certain range of wind/wave conditions and the freshwater influx in the surface layer of the ocean.

Comments

© Author(s) 2015. CC Attribution 3.0 License

Oral Presentation from Session: Sea Surface Salinity Variability: In Situ and Satellite Observations

Session Abstract:

The relation of sea surface salinity to the atmospheric hydrological cycle and ocean circulation is at the core of major ongoing in situ and satellite programs. It is climate relevant, both in the context of recent climate variability and on-going climate change.
We encourage the presentation of investigations on processes maintaining a maximum salinity in the subtropical gyres (in particular the SPURS project), tropical near-surface salinity budgets and studies of the near surface stratification induced by turbulent air-sea fluxes and rain. Results pertaining to the 'modern' ocean and using in situ or new satellite data (for example, SMOS and Aquarius missions) and 'realistic' numeral modelling, will be particularly welcome.

Additional Comments

Geophysical Research Abstracts Vol. 17, EGU2015-8718, 2015

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