Oceans absorb some of the carbon dioxide and heat released by human activities, such as fossil fuel combustion for energy production and derivation of petrochemical products useful in many aspects of daily life. Specifically, carbon dioxide dissolves in water to form carbonic acid, a weak acid that increases the acidity of ocean water. Increase in acidity has been associated with loss of corals as the calcium carbonate integral to the structure of coral reefs disintegrates with lower pH (and increased acidity) of water.
Hence, while helping to ameliorate the effect of climate change by retarding the increase of carbon dioxide in the atmosphere, ocean water absorption of the greenhouse gas also brought forth negative impacts to the ecology of ocean water, both along the coast where coral reefs thrives as well as the deep ocean, the life blood of fish stocks.
But, given the vastness and volumes of the world’s oceans, do oceans offer an infinite capacity for removing all of the extraneously released carbon dioxide? If not, what is the impact of exhaustion of climate amelioration effect of oceans on the rate of increase of global warming around the world?
The Southern Ocean, which surrounds the continent of Antarctica, is a vast underwater storage bank for significant amount of carbon dioxide and heat in the world, and thus, plays an important role in modulating the world’s climate through a network of global ocean currents that originates from the continent to the Pacific, Indian and Atlantic oceans. However, measurements through arrays of floats that chronicle data on salinity and acidity of water reveals that the Southern Ocean is increasingly acidic and saline, which meant that the southern polar vortex that upwells deep ancient water to the surface is playing a significant role in reducing the capacity of the ocean to absorb excess carbon dioxide and heat released into the atmosphere in our technological societies.
Specifically, ancient high acidity and carbon dioxide rich upwell waters at the sea surface has reduced capacity to absorb carbon dioxide and heat. Thus, a significant source of absorption capacity for greenhouse gases is reduced, with potential far reaching implications for the modulation of climate around the world in the decades to come (Nature’s News Feature, Link).
More importantly, as more rain falls around the Antarctica coastline and glaciers on the permanent ice sheets melts, more freshwater are introduced to the surface waters around the continent, which reduced the removal of heat and carbon dioxide by the ocean. The absorbed heat and carbon dioxide recirculates to other parts of the world through ocean currents that carry and redistribute the absorbed heat and carbon dioxide away into the world’s oceans. In some places, measurements of the temperature of the deep ocean currents revealed that they are 3 oC warmer than before, due probably to a lack of surface water infusion that helps cool the water.
This, together with the increased acidity of surface water in the Southern Ocean, reduced the capacity of the ocean in absorbing carbon dioxide and heat from the atmosphere. Given the important role of this vast ocean in modulating surface climate through a combination of redistribution of heat and carbon dioxide as well as air-surface water exchange, it meant that reduced climate modulation effect of the Southern Ocean must be quantified in more detail and factored into global circulation models for climate simulation with a representative concentration profile (RCP) of predicted greenhouse gas concentrations. One area requiring more research is the role of plankton in affecting the carbon balance of the oceans as they, on a seasonal timescale, increase the absorption of carbon dioxide in summer but the effect progressively reduce as winter and dark skies set in at the Southern Oceans.
Overall, oceans’ capacity at absorbing carbon dioxide is finite, and with changes in upwelling patterns and increase in fresh water influx to the Southern Ocean, an important sink for atmospheric carbon dioxide is showing increasing signs of saturation. Coupled with the modulated flows from the Southern Ocean to the adjoining Pacific, Indian and Atlantic oceans, redistribution of absorbed carbon dioxide and heat could be significantly retarded, leaving maldistribution of heat in the global climate system with consequences hitherto under-appreciated in global climate model simulations. Leaving the amelioration effect of oceans aside, continued reliance on fossil fuel combustion for energy and mobility meant that the desire of controlling climate change at 2 oC above preindustrial levels could be a pipe dream without significant investment in carbon capture and storage and renewable energy solutions.
Category: climate change, science policy,
Tags: ocean air interchange, global warming, absorption of carbon dioxide, ocean currents, heat absorption,