Shelf Seas and Shelf Edge Dynamics

Learning Outcomes

Transferable and Generic Skills

Having successfully completed this module you will be able to:

• Use and interpret numerical models for scientific problems; use/manipulate Matlab scripts to predict tides and analyse field data (computer literacy).
• Write a scientific report.
• Work as a team in the field.
• Retrieve information from the literature

Learning Outcomes

Having successfully completed this module you will be able to:

• Collect and analyse field data to quantify and explain local phenomena controlling the strength of stratification in a Region of Freshwater Influence (ROFI).
• Understand the physical constraints on transport between the shelf and the deep ocean, the physical mechanisms that drive such transport, the biogeochemical consequences, and how such processes are ideally observed in the field.
• Recognize and describe various aspects of turbulence (Reynolds stresses, eddy viscosity, length scales) in relation to mixing in shelf seas
• Use a 1-D coupled model to investigate physical and biological processes in shelf-seas, in relation to seasonal stratification and tidal mixing fronts in two contrasting locations worldwide.
• Provide a general explanation of the competing effects of heat and fresh water input and vertical mixing by tides and winds in determining the level of stratification in shelf seas.
• Describe and explain the physical controls on the biogeochemistry of shelf seas.

Subject Specific Intellectual and Research Skills

Having successfully completed this module you will be able to:

• Identify key physical processes and their implications for primary production through evaluation of oceanographic data.
• Run, visualise and interpret output from a coupled physics/biology 1-D numerical model, explain the results when a key parameter is varied, and use the model to simulate observed physical/biological structures in UK shelf seas.
• Quantify the effects of freshwater and tidal mixing on the strength of stratification in a partially mixed estuary (Southampton Water).
• Summarise the understanding of physical and biological processes described in the shelf-seas literature and contemporary research challenges.

The shelf seas and shelf edge are dynamically very different from the open ocean in terms of typical levels of turbulence and of the control exerted by coastal and seabed boundaries. This module provides you with core knowledge of the processes that govern the relatively shallow shelf seas, from coastal waters to the shelf break. By the end of the course, you will understand a range of physical and biological processes that explain observed structures, distributions and phenomena, both physical and biological, on time scales ranging from seconds to years.

First of all, physical forcing and dynamical responses in shelf seas are outlined with emphasis on turbulence and mixing in homogeneous and stratified fluids. Tides are then outlined, from first principles (the equilibrium tide, tidal constituents) to applied situations (propagation of the tide around semi-enclosed seas, resonance and local variations in tidal amplitude).

The following section of the course develops a quantification of stratification, the potential energy anomaly (PEA), particularly useful for understanding the seasonal cycle of stratification in shelf seas. In a 1D (vertical) context, the tendency (time variation) of PEA is related to the competing influences of turbulence (due to tides and wind) and stratification (due to heating and freshwater input) in determining the physical environment. Considering a near-balance of mixing and stratifying influences, the location of tidal mixing fronts (TMFs) are predicted, along with the dynamical consequences of these structures (along-front jets). The biological consequences of both seasonal stratification and TMFs are further considered in detail, along with regions of freshwater influence (ROFIs).

Finally, dynamical processes at the shelf edge are considered, with emphasis on how the shallow shelf region is connected to the open ocean in spite of strong bathymetric control on shelf edge dynamics. Emphasis is on the physics of upwelling and downwelling events, and how these events can control nutrient and carbon fluxes across the shelf edge.

During the course you will use and interpret output from a numerical model to explore the seasonal cycles of stratification and productivity in shelf seas around the UK. The model will be introduced in a computing practical and it then forms the basis of a course project, in which you will use model output to demonstrate fundamental physical and biological processes discussed during the course.

Formal Lectures (11 x 2-hour lecture sessions): These provide the theory underlying the physics and dynamics of the shelf seas and shelf edge, and associated controls on many biogeochemical processes. Copies of the PowerPoint slides and selected pre-recordings are available on the SOES3009 blackboard website (module is dual-coded) prior to each lecture and the Panopto recordings of the lecture sessions will be available there afterwards. Relevant references appear on the slides where appropriate. The lectures are interactive, including time to work through example questions and problems.

Practicals: There will be 11 (weekly) practical sessions, aligned with lectures: Practical 1 – Bathymetry of shelf seas and the shelf edge; Practical 2 – Physics & Dynamics; Practical 3 – Turbulence & Mixing; Practical 4 – Tidal Prediction and Analysis; Practical 5 – Stratification; Practical 6 – Tidal Mixing Fronts; Practical 7 – Modelling Shelf Seas; Practical 8 – Modelling primary production; Practical 9 – Shelf Edge Flows; Practical 10 – Upwelling & Downwelling; Practical 11 – Regions of Freshwater Influence. Most sessions involve a mix of problem solving and data analysis, or prediction, with prepared Matlab scripts. Through Practicals 3 and 5-8, we will introduce you to the 1-D coupled biological-physical water column model and how to visualise the results in relevant software (Excel, Matlab or Surfer). You will learn how to apply the model to predict and investigate seasonal stratification and tidal mixing fronts around the UK. In addition to those set in practicals, a number of problems will be set and discussed during the formal lectures.

Guest lectures: We aim to include at least one relevant research seminar or guest lectures during the course.

A wide range of support can be provided for those students who have further or specific learning and teaching needs.

Summative

This is how we’ll formally assess what you have learned in this module.