The work is based on ice cores from the Antarctic. The layers of eternal ice form an archive of the atmosphere, in which not only dust particles and solids but also air and other gases are trapped. In these bubbles one can determine the concentration of different gases. For once, it is not the usual suspects such as the greenhouse gases methane and carbon dioxide that play a role, but the noble gases krypton, xenon and argon, as Bereiter points out. The principle can be explained as follows: cooling water absorbs noble gases from the atmosphere, while warming water releases noble gases into the atmosphere. The concentration of noble gases in the atmosphere thus allows conclusions to be drawn about the average global temperature of the sea – and not only the warmer ocean surface, but the mean temperature averaged over the entire mass of water to the very bottom of the sea.
A look into the past
The drill cores from the Antarctic ice cover the period of the past 24'000 years. During this time, the transition from the last ice age to the current warm age took place. This is also reflected in the results from drilling cores: the researchers found a significant rise in mean ocean temperatures; overall, the ocean warmed up by 2.6 degrees Celsius over a period of 10'000 years. In the analysis of the data, Bereiter found that the increase in average global sea temperature is strongly correlated to the air temperature in Antarctica, which underscores the influence of the southern hemisphere on the global climate.
Up to now, this type of temperature measurement can only be applied to very large changes such as the investigated transition from an ice age to a warm age. In theory, however, the method should also work to monitor current changes. These are (still) relatively small compared to the temperature changes investigated in the current study, which is why much more precise methods than are currently available are urgently needed, according to Bereiter.
