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High Productivity on a Coastal Bank: Physical and Biological Interactions

P.F.J. Lermusiaux,
P.J. Haley, Jr., W.G. Leslie
M.P. Ueckermann, C. Mirabito

Massachusetts Institute of Technology
Center for Ocean Engineering
Mechanical Engineering
Cambridge, Massachusetts

James J. McCarthy

Harvard University
Agassiz Professor of Biological Oceanography
Harvard Museum of Comparative Zoology
Cambridge, Massachusetts

 

Ongoing MIT-MSEAS Research
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Background information
This research is sponsored by the MIT Sea Grant program

Ongoing MIT-MSEAS Research

Objectives: Our overall objective is to determine the interplay among physical and biological processes that enhance the nutrient delivery in the vicinity of Stellwagen Bank and the production and retention of plankton biomass over the Bank, in the regions of greatest cetacean densities.

Specific objectives are to:

Methodology: This research is utilizing and further developing a multiscale modeling system for Stellwagen Bank so as to investigate hypotheses relating to the roles of physical features and processes (e.g., topography, internal tides/waves, recirculation eddies, coastal current) in the supply and retention of nutrients and biomass that drive primary production and support a food web that spans from plankton to whales. The modeling research involves idealized and realistic simulations so as to isolate and characterize processes, and is being validated using historical and synoptic ocean data.

The Multidisciplinary Simulation, Estimation, and Assimilation System (MSEAS) is being combined with historical and community data. For physics, MSEAS contains both hydrostatic and non-hydrostatic codes; for biology, a general biogeochemical modeling system coupled to the physics, with varied options for the biological parameterizations and components (state variables). At the numerics level, we employ time-dependent finite volumes, second order in both time and space, which preserve mass, tracers, and energy. Our code uses new implicit two-way nested schemes for multi-resolution domains. Another major upgrade utilized in this project is our high-order finite element scheme (Hybrid Discontinuous Galerkin) on unstructured grids, for both non-hydrostatic Boussinesq physics and biogeochemical dynamics. Our new machine learning schemes that can learn model structures and functions using full Bayesian estimation are also being used for the biological structures.

Overall, our approach consists of: i) idealized dynamics simulations to characterize features and processes; ii) realistic multi-resolution ocean estimation with data assimilation to determine multiscale interactions; and iii) sensitivity studies in both idealized and realistic conditions to explain the foundations of observed features.

 

MSEAS Sea Grant-supported Publications

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Additional links

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Background information

Throughout the world's oceans, coastal banks are regions with diverse ecosystems that often have conspicuously high productivity when two or three conditions are met: the topography and flow characteristics are favorable to sustained inflows of nutrients, the light and stratification conditions are conducive to plankton production and retention, and there is a pronounced positive feedback from higher trophic levels back to plankton production. In this resesarch we focus on Stellwagen Bank, which lies between Massachusetts Bay and the greater Gulf of Maine. This bank is widely known for its highly productive pelagic ecosystem, which supports large, actively feeding populations of cetaceans throughout the summer.

This work is a collaborative effort between the groups of P. Lermusiaux (MIT) and J. McCarthy (Harvard), who have previously cooperated in the MB region. It involves undergraduate students (via UROP projects at MIT), sponsored graduate students, post-doctoral fellows and research scientists. This research seeks also to involve the local fishing fleet and maritime organizations and industries.

This research is useful for several users including local maritime industries, such as fisheries and tourism, but is also relevant to security and conservation, and ultimately to the ocean's health and climate. Specifically, our results would be relevant to ecosystem-based support of fisheries but also to the management of endangered species, as well as the Marine Sanctuary. The proposed research is a very appealing subject for outreach and public engagement activities at MIT and in Massachusetts, at all ages.

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