Lecture 9/10 - Ocean Circulation & Storm Surges Flashcards
How are wind driven currents formed?
Wind transfers energy onto the surface waters, resulting in a mass movement of water. Maintains its current after initial force has gone. Current is pushed down at 30 degrees.
How are gyres formed?
A gyre in oceanography is any large system of rotating ocean currents, particularly those involved with large wind movements. Results from a mass movement of water, and influenced by major meteorological systems.
What is the importance of gyres?
Gyres are semi-permanent features. With both convergent and divergent gyres existing. These are mass movements of heat energy and greatly impact on life in the oceans.
What is a Western Boundary current?
Western boundary currents are warm, deep, narrow, and fast flowing currents that form on the west side of ocean basins.
Why do western boundary currents form?
Due to western intensification. As well as the impact of Coriolis (deflection toward Pole) and the impact of conservation of vorticity.
They carry warm water from the tropics poleward.
What are oceanic fronts?
Oceanic fronts are boundaries of water masses of different densities, much like atmospheric fronts.
What are Eddies?
Eddies are small, temporary loops of swirling water that can travel long distances before dissipating
What are the characteristics of eddies? (6)
5-7C change in SST Warm Less common 1:2 ratio with cold Typically 80km diameter Cf Depression 1000s km Angular velocity 150cm/s at sfc / 32cm/s at 700m Inverted cone shaped
What are meddies?
Outflow from Mediterranean Sea into Atlantic, warm, saline waters. Introducing high density, warm water resulting in meddies.
What are some features of meddies?
No pattern of movement, but tend to drop to the South, then back north.
Angular velocity – 30cm/s, Rotation period 5 days and are long-lived features.
What are tidal eddies?
Eddies caused by tide that are topography related.
Relatively small scale compared to other eddies
Common around Portland Bill and Nell’s Point in Barry Island.
Roles of Eddies
➢ Heat, salt and nutrient transfers
➢ Water volume transfer – exchange between hemispheres
➢ Impact on ocean models – rethink our ideas on the way the ocean works of the steady state ocean models, which had been relooked at.
➢ It changes the way circular systems are considered
What is the WOCE and what did they do in relation to circulation experiments?
World Ocean Circulation Experiment, with a combination of observation, modelling, remote sensing (satellite, buoys etc.)
It was the most comprehensive programme ever undertaken that greatly focused on ocean circulation and variability.
What are storm surges?
A surge is the elevation of water levels above those predicted for tide.
Storm surges are from a combination of low pressure and high winds.
What intensifies a storm surge? (4)
Nature of tide can e.g. Spring/Neap
Reduction on atmospheric pressure
Wind stress
Local topography
