Week 8

• Anoxic regions in the ocean coincide with the build up of carbon and nutrients from falling organic material being respired by microbes and re-dissolved into the water.
• Ventilation tracers for the Atlantic along 20°W include observed meridional sections of CFC-11, dissolved oxygen, and radiocarbon.
• CFC-11 is zero in the deep ocean because water from the deep has not come into contact with the atmosphere since CFCs were released.
• The north Atlantic has very quick deep-water formation, demonstrated by the deeper depths at which CFC-11 is found.
• Since we know when CFCs were first released, and we know how deep they have gone in the ocean, we are able to calculate how long different water masses in the deep ocean take to circulate.
• Heat, chemicals and momentum are exchanged between the atmosphere and ocean.
• The North Atlantic Oscillation (NAO) is a phenomenon that affects the jet stream and weather patterns further afield.
• A Subpolar Low near Iceland generally has lower air pressure than the Azores Subtropical High.
• The pressure difference between Azores and Iceland changes over time, this phenomenon is termed the North Atlantic Oscillation.
• A positive NAO gives warm and wet weather to the UK, with strong westerly winds.
• A negative NAO brings warm and wet weather to the Mediterranean.
• The Earth’s fluid environment is influenced by the North Atlantic Oscillation.
• Global and Local Sea Level is influenced by the amount of ice stored on land, the average temperature of the ocean, and the geological shape of the ocean basins.
• Local (relative) sea level is affected by the vertical motion of the local land, spatial differences in the geoid, and spatial variations in ocean heating and ocean circulation.
• Sea levels are rising in the current anthropogenic era (since the mid-1800s) and this sea level rise has been measured.
• Global mean sea level is currently rising 3.3 mm/yr and the rate of sea level rise is increasing.
• The first United Nations sea level rise predictions were made in 1990 and since then, sea level rise has been at the maximum of those predictions.
• Measuring sea level involves defining terms such as relative mean sea level, bench mark, and geoid.
• The line of cloud shows the Intertropical Convergence Zone (ITCZ).
• The Walker Circulation is the most atmospheric convective circulation cells are aligned North - South (meridional: Hadley Cells, Polar Cells) because temperature contrasts are generally North - South.
• Wind-driven Ekman upwelling off the West coast of South America and Africa brings cold deep water to the surface.
• Getting an East - West temperature contrast along the equatorial Pacific and Atlantic basins drives an East - to - West overturning cell: Walker Circulation.
• This sets up and East - to - West temperature contrast, and drives atmospheric convection in the East - West direction:El Nino Southern Oscillation.
• Reduction in wind-driven coastal upwelling brings a warm anomaly to the Easter equatorial Pacific.
• Upwelling of Walker Circulation moves East.
• El Nino conditions are characterized by warmer than normal waters and cooler than normal waters.
• Increase in wind-driven coastal upwelling brings a cool anomaly to the Easter equatorial Pacific.
• La Nina conditions are characterized by East Pacific sea surface temperatures 3 to 5 ° C below average and above average rainfall West Pacific (e.g. Indonesia/Australia), and below average rainfall East Pacific (e.g.).
• The concept of 'storm tracks' is a coupled ocean - atmosphere phenomena.
• Large scale atmosphere - ocean weather phenomena include the El Nino Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO).
• Surface atmospheric winds are much faster than ocean currents.
• Friction across the air-sea interface exchanges momentum between the atmosphere and ocean.
• The 'wind stress vector' shows the direction of this momentum transfer to the ocean.
• Many chemicals are both gasses in the atmosphere and aqueous dissolved solutes in the ocean, including CO2, O2, CFCs.
• The 'wind stress curl' tells us whether this momentum transfer makes ocean water cyclonic (positive values) or anticyclonic (negative values).
• In the Northern Hemisphere, cyclonic (positive) wind stress curl drives upward Ekman pumping and upwelling.
• Anticyclonic (negative) wind stress curl drives Ekman suction and downwelling.
• This is reversed in the Southern Hemisphere, where cyclonic (positive) wind stress curl drives downwelling and anticyclonic (negative) wind stress curl drives upwelling.
• Positive wind stress curl to the North of the Southern Ocean links to formation of Antarctic Intermediate Water (AAIW).
• The geoid is the shape of mean sea level in absence of winds, currents, tides variations in water density and atmospheric pressure.