Chemical Oceanography

Study of the chemicals found in the ocean

• Make life in the ocean possible
• Affect the way the ocean circulates
• Tell us how the ocean was in past times

Chemical terms

• Elements - basic building block of chemistry, e.g. Na
• Compounds - combinations of elements, e.g. NaCl
• Ions - any element or compound with a charge, e.g. Na⁺
• Moles - atomic or molecular weight in grams, e.g. 1 mole H₂O = (2 x 1) + (1 x 16) = 18 grams

• Typical amount of salt in seawater is ~ 35 g/litre
• Major ions (6) make up 99.4 % of all dissolved chemicals
• Marcet's Principle - major ions uniformly mixed
• Minor and trace species lower concentrations -- non-uniform distribution, useful for tracing oceanic processes
• Why are some elements high concentration and well mixed and others low concentration and not?

• Water flows indicate rivers most likely source
• Composition of river water very different from the ocean

• Average amount of time an element spends in the ocean before removal
• Range from < 50 yrs (Fe) to > 50 million yrs (Na)
• All major ions have residence time > 1 million years
• Mixing time of the ocean