what was cold war oceanography like?
- global ocean circulation studies to track submarine pathways
- internal waves & turbulence to understand acoustic variabillity
- satellites first developed for military surveilance & later adapted to measure sea surface height (TOPEX/Poseidon)
what is an Ekman current meter?
1903
mechanical propeller, vane for direction & stop clock for timing
what is chlorinity titration?
Knudsen method
later used salinometers & conductivity sensors
what is wind driven ocean circulation?
caused by winds blowing across sea surface
trade winds & westerlies
what are mechanisms of wind driven ocean circulation?
Ekman transport: surface currents deflected by the Coriolis effect → net transport 90° to the wind.
Sverdrup transport: curl of the wind stress determines broad patterns of flow.
Western boundary currents: (Gulf Stream, Kuroshio) form as fast, narrow jets that close the subtropical gyres.
what is the relevance of wind driven ocean circulation?
dominates upper ~1000m
controls heat transport for equator to poles
creates upwelling systems -> high biological productivity
how do trade wind & westerlies create gyres?
Easterly and westerly trade winds combine to “pile up” water in the middle of the subtropical oceans.
how does Ekman transport produce gyres?
Surface waters are deflected 90° to the right in the Northern Hemisphere due to the Coriolis effect which drives water toward the center of the basin
how does a pressure gradient & Geostrophic balance produce gyres?
The mound of water in the center of the gyre creates a pressure gradient forming a circular current.
how does Western boundary Intensification produce gyres?
Due to Earth’s rotation and geometry, the western boundary current (e.g., Gulf Stream, Kuroshio) is fast and narrow while the eastern boundary current (e.g., Canary Current, California Current) is slow and broad.
Result: large, stable subtropical gyre in each major ocean basin.
what is a gyre?
any large system of ocean surface currents moving in a circular fashion driven by wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction determine the circulatory patterns from the wind stress curl.
what is thermohaline ocean circulation?
Driven by density differences in seawater (temperature “thermo” + salinity “haline”).
what are the mechanisms of thermohaline ocean circulation?
cold, salty water sinks in high latitude
dense water spreads at depth
-> replaced by surface inflow
= Global Conveyor Belt
what is the Global Conveyor Belt?
dense water spreading at depth takes heat, O2 & nutrients around the globe
what is the timescale of the Grand Conveyor Belt?
very slow overturning
-> over centuries
what is the importance of the Global Conveyor Belt?
regulates Earth’s climate
controls deep water ventilation -> supplies O2 to abyss
key to carbon storage in deep ocean
sensitive to climate change
-> melting ice = freshwater input = AMOC weakening
what is the El Nino Southern Oscillation?
Strongest natural year-to-year climate signal.
Links ocean circulation, heat transport, and atmosphere into a coupled system.
Essential for understanding seasonal forecasting and long-term climate change interactions.
what are the current priorities for physical oceanographers?
- Quantify heat storage in the ocean (oceans absorb >90% of Earth’s excess heat).
- Track sea level rise (thermal expansion + ice melt).
- Monitor changes in circulation (e.g., weakening of the Atlantic Meridional Overturning Circulation, AMOC).
- Understand stratification & mixing (affecting oxygen supply, nutrient cycling, and ecosystems).
- Improve Earth System Models by integrating ocean physics w/ atmosphere, cryosphere, and biosphere.
what is ocean heat uptake & redistribution?
Most global warming heat goes into the ocean & oceanographers need to know where it is stored (surface vs deep).
Heat flow by currents, eddies & mixing controls whether heat is sequestered in the deep ocean or drives surface warming.
what is thermohaline circulation?
cold & salty water is denser = sinks
warm freshwater lighter = stays near surface
part of Deep Global Conveyor Belt
freshwater input from ice sheets lower salinity in the North Atlantic
fresher water = less dense - resists sinking & circulation slows down / stops
w/out overturning, less heat is carried northward
what are modern day tools of oceanography?
Big Data and Ocean Observation – Satellites, autonomous vehicles, sensor network
what is the Argo Float Programme?
By late C20th physical oceanographers were needing more data
Ship-based sampling (bottles, CTDs, expendable bathythermographs) gave only snapshots of ocean.
Satellites could observe surface (sea surface temperature, height, colour) but not deep ocean
To understand climate variability and change esp ocean heat content and circulation, scientists needed a global, continuous, subsurface observing system
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Hydro Circle26
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Ocean meets lava6
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the physical ocean13
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demystifying photosynthesis39
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microalgae & ecology35
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cyanobacteria28
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algae in biological associations58
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microalgae tropic ecology61
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algae in extreme environments40
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eutrophication & algal blooms27
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geoengineering - ocean fertilisation19
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data visualisation5
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physical oceanography22
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intro chem46
