Study predicts ocean ‘dead zones’

Global warming may create “dead zones” in the ocean that would be devoid of fish and seafood and endure for up to two millennia, according to a study published on Sunday.

Its authors say deep cuts in the world’s carbon emissions are needed to brake a trend capable of wrecking the marine ecosystem and depriving future generations of the harvest of the seas.
In a study published online by the journal Nature Geoscience, scientists in Denmark built a computer model to simulate climate change over the next 100,000 years.

At the heart of their model are two well-used scenarios which use atmospheric levels of carbon dioxide (CO2), the main greenhouse gas, as an indicator of temperature rise.

Under the worst scenario, CO2 concentrations would rise to 1,168 parts per million (ppm) by 2100, or about triple today’s level.

Under the more optimistic model, CO2 would reach 549 ppm by 2100, or roughly 50 percent more than today.

The temperature rise that either would yield depends on several factors: when the peak in carbon emissions is reached and how quickly it falls, and whether the warming unleashes natural triggers, or tipping points, that enhance or prolong the warming in turn.

Taking such factors into account, the scientists predict a possible rise of around five to seven degrees Celsius over pre-industrial times under the worst scenario. Under the other scenario, there would be warming of roughly between two to four degrees Celsius.

Either scenario spells bad news for the ocean, said Jens Olaf Pepke Pedersen, a physicist at the Technical University of Denmark.

Sydney Morning Herald