Effects of global warming on the world’s oceans Ashley A. Emerson

Anthropogenic CO 2 in the Ocean

CO 2 solubility  Temperature: more soluble at lower temperatures.  Salinity: more soluble in greater salinity.  Pressure: more soluble under higher pressure.

Carbon dioxide buffering in the Ocean  CO 2 enters ocean via diffusion and rapidly converts to HCO 3 -  Reaction: CO 2 + CO 3 +H 2 O  2HCO 3 -  As CO 2 in atmosphere rises the strength of ocean carbon uptake will weaken  Adding more carbon and keeping it as CO 2 makes the ocean more acidic.

Dissolved Inorganic Carbon (DIC)  CO 2 reacts to form other compounds of DIC.  If in acidic solution: carbon in CO2 form  If in basic solution: carbon mostly in carbonate form  Ocean pH ~8 = Carbonate form

Ocean acidification  By end of century, it is predicted that oceans surface-water DIC could decrease over 12%  Carbonate ion concentration decrease almost 60%  This would result in a pH drop in surface waters of 0.4 pH units

Calcium carbonate budget Feely et al. 2004

Impacts of anthropogenic CO 2 on Calcium Carbonate  Aragonite and calcite undersaturation will occur at high latitudes when CO 2 values reach 1200 and 1900 µatm  And at tropical/subtropical regions when CO 2 values reach 1700 and 2800 µatm  Profound impacts on calcium carbonate shell-forming organisms

Alkalinity  Determines pH and balances among forms of DIC  The sum of cation charges minus the sum of anion charges  Seawater is always positive, excess pos. charge  This is balanced by carbonate system  electrical neutrality CO 3  HCO 3 -  CO 2

Carbonate Pump  Organic productivity is also associated with calcium carbonate production.  CaCO 3 precipitation decreases alkalinity by 2 units (via removal of double-charged Ca++) but the total CO 2 by only one unit (removal of CO 3 -)  Due to dominance of alkalinity change, there is a net shift of carbon towards CO2 CO 3 --  HCO 3 -  CO 2  Formation of CaCO 3 therefore increases surface water CO 2

Ocean and atmosphere in the North Atlantic  Contribution of biological pump to anthropogenic carbon fluxes is very small everywhere except in high latitudes  High latitudes biological pump’s contribution is ~20% of the solubility pump.  The rate limiting step of anthropogenic CO2 uptake is ocean circulation and mixing.

Other Factors to consider  Model shows as anthropogenic CO 2 increases there will be reduced uptake of CO 2 by oceans.  Primarily as a result of weakening of collapse of thermohaline circulation  El Niño events may be occurring more often as a result of increase anthropogenic CO 2