Final thoughts

Fossil fuel combustion and land-use changes have released great amount of carbon to the atmosphere. In the 1990s, burning of fossil fuels added 6.2 gigatons of carbon (GtC) per year to the atmosphere. As a consequence, the greenhouse effect causes global warming temperatures. However, only a portion of CO2, i.e. 2.8 GtC increase per year, is being found in the atmosphere (Sabine et al. 2004). We partly owe this to oceans.

 

 

Fossil fuel combustion and land-use changes have released great amount of carbon to the atmosphere. As a consequence, the greenhouse effect causes global warming temperatures. However, only a portion of CO2 is being found in the atmosphere.

Ocean carbon uptake, both through physical (solubility pump) and biological (primary production) processes is acting as a net CO2 sink. Oceans release back to the atmosphere some of the carbon they absorbed through the natural carbon cycle. Some of the carbon nonetheless remains in the ocean. It gets trapped into sediments. Ultimately, it is this sequestrated carbon that is responsible for lowered atmospheric CO2 levels.

How much carbon the ocean pumps is under debate because measuring carbon balance in the sea is problematic. It is especially difficult to quantify sequestrated carbon.

Although uncertainty is associated with the extent of the ocean carbon uptake, we know it has been mitigating global warming.

However, the effects of carbon absorption are being felt and will be felt in the future. Feedback loops are alarming for climate change. Oceans are likely to loose some of their ability to pump CO2 because of the changes they have been mitigating. CO2 is less soluble in warmer water, so warming temperature negatively affect the solubility pump. And chemical changes are decreasing primary production. Under IS92a, dissolved inorganic carbon per unit change in atmospheric carbon will decreased by about 60 % in 2100 because of lowered levels in surface carbonate ions (Orr et al. 2005). Marine biology is also paying the price of carbon uptake.

The problem is that we know little about how much carbon is stored and transported in the oceans. So far, we know they are responding to climate change in unpredicted ways. We cannot count on oceans to absorb our emissions like they have done in the past. The scientific community is alarmed by the changes we are observing, both for carbon uptake and marine life.

Increased knowledge would help to a great extent. Precisely, projects are being funded. The ACE CRC is planning a large-scale research project in the Southern ocean. Uptake geochemical processes as well as transport to the deep oceans will be studied, through the use of moored observatories, profiling floats and opportunity ships. NASA and NOAA are preparing similar large-scale programs.

Hopefully these will help our understanding of the unknown ocean. It may continue to surprise us in unpredicted ways.

 

The vastness of the Ocean. Source: The National Geographic