An attempt to measure the release of hydrocarbon gases around the Arabian Peninsula has turned up an anomaly, with exceptional amounts of ethane and propane emitted from the northern Red Sea. On its own, the hotspot isn't large enough to be making a major difference to global levels of the pollutants, but people downwind are affected, and the surprise discovery raises the possibility of other unknown sources.
Oil and gas drilling releases some stored hydrocarbons that don't get captured, representing a substantial contributor to greenhouse gas emissions even before the fuels are burned. Most of the escaping hydrocarbon gas is methane, but some ethane and propane get out too. So, when Dr Efstratios Bourtsoukidis of the Max Planck Institute for Chemistry took part in an expedition to track the concentrations of these gases in waters off the Arabian Peninsula, it was no surprise to find a lot in the oil-rich Arabian Gulf.
What Bourtsoukidis and colleagues had not expected was to find a second site in the northern Red Sea where concentrations were almost as high.
There's no danger of lighting a match and having the place explode – background levels of the two gases combined are about 0.2 parts per billion (ppb), and reaching about 50 ppb in the Gulf, and up to 12.1 ppb over the Red Sea. Nevertheless, Bourtsoukidis notes in Nature Communications, this is 40 times expectations for propane, 20 for ethane, while methane was also surprisingly abundant.
Unless you want to attribute this to the legacy of biblical stirring of the sea floor during Moses' passage with the Israelites, humanity seems to be off the hook for these gases' release. However, ships passing through the area, on the way to and from the Suez Canal, release nitrogen oxides. The reaction of the shipping gases and hydrocarbons produces pollution much more unhealthy than either, posing a threat to cities downwind. As shipping rises in one of the world's busiest seaways the problem will get worse unless cleaner fuels are used.
Bourtsoukidis concluded the sources lie in the Sea's depths. As the paper notes: “The Red Sea... has some unique geological features,” forming part of a continental rift. “The water occupying depths from 300 to 2000 m in the Red Sea is recognized as the warmest and saltiest deep water in the world,” the paper adds. The gases appear to be coming from a combination of seepage from hydrocarbon reservoirs and brine pools on the sea bed. The Sea's exceptionally efficient saline transportation systems allow them to reach the surface.
The total emissions Bourtsoukidis measured are small compared to those released by neighboring Saudia Arabia, Iran, and Iraq in their quest for fossil fuels, but larger than those of major producers such as Kuwait and the United Arab Emirates.