Warming Oceans May Release CO2 Faster than Previously Believed

30.04.2011 - Water & Oceans, Ice & Snow, Bi-polar

According to a new study presented at the Greenhouse 2011 Conference in Cairns, Australia in April, warming oceans could release carbon dioxide (CO₂) dissolved in the water into the atmosphere, further adding to the greenhouse effect.

Normally the world’s oceans are a carbon sink, absorbing part of the CO₂ in the atmosphere, including 30% of man-made emissions; however as the oceans become warmer, the CO₂ dissolved in the oceans could be released, just as warming a bottle of soda causes it to release its carbon dioxide. In addition to warming releasing CO2 dissolved in the ocean, rising temperatures also increase the mixing rate of the ocean, which brings deep, CO₂-rich ocean waters to the surface.

Tas van Ommen from the Australian Antarctic Division (AAD) in Hobart, Australia led a team of researchers in dating CO₂ bubbles trapped in two different ice cores taken from the West Antarctic Ice Sheet (Siple Dome and Byrd Station ice cores) and comparing this to other paleo-temperature records from the same time period. They found that as temperatures increased, CO₂ release followed with a time lag of only 200 years – much shorter than previous studies had found, which put estimates at between 400 and 1300 years. According to van Ommen, the study is more accurate than previous studies because it doesn’t rely on ice cores from regions with little snowfall – which leads to a more gradual trapping of CO₂ in the ice sheet and increases uncertainly in timing – and because it used more than one ice core.

Yet the study comes with an uncertainly of +/-200 years in the time lag between warming and CO₂ release into the atmosphere, which means it is possible that there could be virtually no lag time between rising temperatures and CO₂ being released from the atmosphere. Van Ommen says more climate modelling will be needed before it will be possible to speculate on how the results of this study relate current climate warming.