Internal tides in the Middle Atlantic Bight region are noticeably influenced by the presence of the shelfbreak front and the Gulf Stream. To identify the dominant interactions of these waves with subtidal flows, vertical-mode momentum and energy partial differential equations are derived for small-amplitude waves in a horizontally and vertically sheared mean flow and in a horizontally and vertically variable density field. First, the energy balances are examined in idealized simulations with mode-1 internal tides propagating across and along the Gulf Stream. Next, the fully-nonlinear dynamics of regional tide-mean flow interactions are simulated with a primitive equation model, which incorporates realistic summer mesoscale features and atmospheric forcing. The summer shelfbreak front, which has horizontally variable stratification, decreases topographic internal-tide generation by about 10% and alters the wavelengths and arrival times of locally generated mode-1 internal tides on the shelf and in the abyss. The (sub)-mesoscale variability at the front and on the shelf, as well as the summer stratification itself, also alter the internal tide propagation. The Gulf Stream produces anomalous regions of O(20 mW m^-2) mode-1 internal-tide energy-flux divergence, which are explained by mean-flow terms in the mode-1 energy balance. Advection explains most tide-mean flow interaction, suggesting that geometric wave theory predicts mode-1 reflection and refraction at the Gulf Stream. Geometric theory predicts that offshore-propagating mode-1 internal tides that strike the Gulf Stream at oblique angles (more than thirty degrees from normal) are reflected back to the coastal ocean, preventing their radiation into the central North Atlantic.

Congratulations to Morgan Kane for successfully completing her RSI 2016 summer research with our MSEAS group at MIT. She completed a report and presentation on “Go with the flow: The Effect of Geophysical Flows on Transports”. She is from Mt. Hope High School, Bristol, RI.

Abstract

The purpose of this work is to develop a numerical model that calculates the efficient and safe routes for a vessel to take across the Atlantic Ocean. Existing software exists to perform this task, but it could be significantly improved by building on the experience gained with the open-source model VISIR-I (www.visir-model.net) and the oceanographic datasets of the Copernicus Marine Environment Monitoring Service (http://marine.copernicus.eu/). In particular, the VISIR model has been evolved into a new code in Python and the path optimization is now solved on a non-uniform unstructured grid. The new code will start employing the CMCC CGLORS reanalysis of ocean circulation at ¼ deg, while other relevant environmental fields will be added later on. The new code will be used for achieving the goals of H-2020 project AtlantOS Task 8.3, which includes the capacity to compute safe routes optimizing the economic cost of navigation through use of dynamic environmental information.

Biography

Gianandrea’s research activity aims to improve Maritime Transportation by means of Decision Support Systems. Together with colleagues of the TESSA and IONIO projects, he designed and implemented VISIR, a ship routing model for safer and more efficient navigation, and presently leads its scientific and operational development. As a model, VISIR’s source code is made publicly available following the guidelines of the Free and Open Source Software. As an operational system, VISIR already has an operational implementation in the Mediterranean Sea.

Abstract

VISIR (discoVerIng Safe and effIcient Routes) is a fully open ship routing model. This is achieved through a GPL licensing of the source code and a detailed model documentation on open-access journals. This way, numerical optimization methods, hydrodynamic effects considered, approximations used, and their ranges of application are documented and made available to the scientific community. At the same time, VISIR model is employed in an operational system linked to the operational provision of oceanographic and weather forecasts. The system also includes customized PC and mobile interfaces for end-users. VISIR’s main architectural choices, the input oceanographic and weather forecasts, and an outline of possible goals for a future community of VISIR developers and users are presented here.

Biography

Gianandrea’s research activity aims to improve Maritime Transportation by means of Decision Support Systems. Together with colleagues of the TESSA and IONIO projects, he designed and implemented VISIR, a ship routing model for safer and more efficient navigation, and presently leads its scientific and operational development. As a model, VISIR’s source code is made publicly available following the guidelines of the Free and Open Source Software. As an operational system, VISIR already has an operational implementation in the Mediterranean Sea.