Dissolved Gasses

• oxygen is gained in ocean through photosynthesis
• oxygen is lost in the ocean through respiration
• oxygen solubility at surface varies with temperature and salinity
• oxygen concentration at surface can also differ day and night due to levels of photosynthesis and respiration
• water mass advection and thermohaline circulation leads to lateral variations of oxygen in oceans
• oxygen in freshwater is more soluble at a colder temperature
• oxygen solubility in freshwater

  
• surface water at poles have higher oxygen then at tropics
• dissolved oxygen at poles is 350-400 uM
• saturation value is the equilibrium amount of gas dissolved at an existing temp, salinity, and pressure
• at 30C there is about 100 uM dissolved oxygen
• a lot of air is incorporated in shallow water due to waves
• physical processes can increase the oxygen concentration
• photosynthesis can lead to supersaturation in shallow waters
• rate of primary production is greatest at the surface
• saturation of oxygen in ocean

  
• photosynthesising phytoplankton cell

  
• daylight allows photosynthesis in euphotic zone
• oxygen is removed from the ocean at night from respiration
• deep ocean has respiring bacteria
• respiring bacteria can be uniformly distributed through the water column
• dead organic matter is colonised by the bacteria
• organic material can have 10^9 bacteria per cm 3
• oxygen depth profile

  
• changes in oxygen at depth of 1000m is dominated by bacterial respiration
• north Atlantic water is young and deep
• young water means that is was recently in contact with the atmosphere
• north Atlantic water is salty and cold and rapidly sinks
• north pacific water is aged deep water
• MOC distribution of oxygen

  A) aged deep water

  B) young deep water

  
• north Atlantic deep water brings down the well oxygenated water and moves laterally
• north Atlantic water starts to age as it sinks
• movement of north Atlantic deep water

  A) NADW

  
• deep pacific has lower oxygen as the water has been aged
• aged water has oxygen used up by respiration
• oxygen concentration from north Atlantic decreases southwards
• oxygen depth profile comparison

  A) north Atlantic

  B) north pacific

  C) oxygen

  
• changes in distribution of dissolved nutrients depends on primary production
• low concentrations of phosphate, nitrate, and carbon in shallow waters when there is increased photosynthesis
• phosphate in deep water are at a minimum in north Atlantic but increase southward