Temperature, Salinity and Acidification

TEMPERATURE Sunlight heats the surface of ocean water (H2O) 3 temperature zones of ocean water: Surface zone: warmest; sea level to 300m; sunlight only penetrates a few meters, but wind and waves mix heat evenly throughout the surface zone. Thermocline zone: marked by a rapid temperature change with depth; marks the boundary change between the surface zone and the deep zone; 300-800m below sea level. Deep zone: temperatures continue to decrease slowly; 800m-ocean floor.

What is in ocean water? 96.5% of ocean water is H2O The other 3.5% is dissolved gases and solids such as salt (NaCl) Sodium Chloride is the main salt in the ocean

 Salinity Salinity - the amount of dissolved solids (mainly salts) present in ocean water. Average salinity of ocean water is 35%o %o = parts per thousand (ppt) 50 million billion tons of salt in our seas 1,000g of seawater consists of 35g of dissolved salts

Large amounts of evaporation will increase salinity. Large amounts of precipitation, melting ice, and runoff from land will decrease salinity.

How the oceans became salty… Each year, Earth's rivers carry more and more salt into the ocean. The water evaporates, but the salt is left behind in the ocean. The principle source of dissolved salts in the ocean is the weathering and erosion of rocks on land. Since the oceans were first formed, the oceans have gotten saltier. Now more salt is being deposited on the ocean floor as is coming from rivers reaching a general equilibrium

Ocean Resources Desalination – taking the salt out of salt water.

Ocean acidification 26%

Ocean Acidification Excess carbon dioxide from the atmosphere makes its way to the oceans. The oceans are a sink for atmospheric CO2 CO2 increases acidity of ocean water Ocean organisms suffer: especially CaCO3 organisms (calcium carbonate) The oceans are a sink for atmospheric CO2 CO2 dissolves into seawater and causes the pH to decrease (making it more acidic) Marine organisms remove CO2 from the water to make calcium carbonate shells Decreasing pH makes those organisms unable to take in as much CO2, leaving more in the water, leading to the oceans taking in less from the atmosphere Ocean acidification is threatening organisms with calcium carbonate shells!

Ocean Acidification Atmos CO2 seawater CO2 pH * (Feely et al., 2008) The oceans are acidifying as a result of the dissolution of atmospheric CO2. This is measurable: time series from the North Pacific. Data: Atmospheric CO2 Pieter Tans, Seawater data: David Karl Chemistry is well known, predicted over 20 years ago Consequences for climate, C cycle and fisheries, etc. Not fully anticipated Only way to halt ocean acidification is to decrease CO2 in atmosphere – decrease emissions pH (Feely et al., 2008) * 10

pH disrupts shell formation Ambient pH pH Coccolithophores largest producer of calcite on Earth E. huxleyi G. oceanica C. braarudii C. quadriperforatus Coccolithophores largest producer of calcite on Earth, responsible for x% of primary (plant) production in ocean. Considerable number of laboratory experiments and some large enclosures in ocean have been conducted – show that as pH decreases the shells of these organisms are deformed, less CaCO3 Implication is that as pH ocean decreases, they will draw down less calcium carbonate to deep ocean Therefore, less CO2 would be removed from atmosphere by ocean. More CO2 in atmosphere – warmer climate. NASA image

Negative impact on fisheries economic losses global shellfish prod. 10.5 billion US$ disruption livelihoods Net calcification rate (wt% per 60 d) Decreasing pH