Ocean acidification saturation and pH

NOAA – Science on a Sphere, Web site and data.

Ocean acidification is a consequence of humankind’s release of carbon dioxide emissions to the atmosphere. Excess carbon dioxide enters the ocean, reacts with water, decreases ocean pH (i.e., makes seawater less basic), and lowers carbonate ion concentration. Organisms such as corals, clams, and some plankton use carbonate ions to create their shells and skeletons. Decreases in carbonate ion concentration will make it difficult for these creatures to form hard structures. Ocean acidification may cause some organisms to die, reproduce less successfully, or leave an area. Other organisms such as seagrass and some plankton species may do better in oceans affected by ocean acidification. Ocean ecosystem diversity and ecosystem services may therefore change dramatically from ocean acidification.

These datasets shows computer model simulations of surface ocean pH and aragonite saturation state from 1895-2094, with continents and coral reefs marked. (aragonite saturation state, sometimes called Ωar, is commonly used to track ocean acidification because it is a function of carbonate ion concentration.) These datasets show surface ocean pH and aragonite saturation state changes over time. Aragonite is one of the more soluble forms of calcium carbonate but it is widely used by marine calcifiers. Each successive frame shows, in 6-month increments beginning with January 1885 and ending with July 2094, the low-pass filtered monthly mean Ωar or pH of the surface ocean as modeled by the Community Climate System Mode 3.1 (CCSM3.1 Doney SC et al. 2009. Skill metrics for confronting global upper ocean ecosystem-biogeochemistry models against field and remote sensing data. JOURNAL OF MARINE SYSTEMS 76(1-2): 95-112). The model simulation is driven with atmospheric emissions based on records of atmospheric carbon dioxide levels, for past dates, and the A2 IPCC SRES scenario for future dates (approx. 850 ppm atmospheric CO2 by 2100). Low-pass filtration removes seasonality and interannual variability with a period of less than 10 years. White indicates no data. A plain-language script for docents is included to help them introduce visitors to ocean acidification and to these particular data.

Notable Features:

  • Dark gray dots show cold-water coral reefs, medium gray dots show warm-water coral reefs
  • The Saturation legend shows how decreasing saturation will affect sea life

NOAA – Science on a SphereWeb site and data.