Australia: The Land Where Time Began

A biography of the Australian continent 

Bølling Transition – Global climate Changes Near-Synchronous in Ice Core Record

The penultimate warming in a series of climate variations, the Dansgaard-Oeschger events, was an abrupt warming event that initiated Bølling-Allerød Interstadial. The relative timing in shifts of climate in different world regions and their causes are subject to debate, in spite of the clear expression in many palaeoclimate records of this transition. In this study Rosen et al. used the air bubbles trapped in the North Greenland Eemian ice core to explore the phasing of global climate change that took place at the onset of the Bølling-Allerød Interstadial, specifically measuring the concentrations of methane which act as a proxy for the climate of low latitudes and the ¹⁵N/¹⁴N ratio, which is a reflection of the Greenland surface temperature over the same time interval. To account for potential uncertainties in the data they used an atmospheric box model and firn air model. They found that Changes in Greenland temperature and emissions of atmospheric methane had occurred essentially synchronously at the onset of the Bølling-Allerød Interstadial, with temperature leading by 4.5^+2.1/_-2.4 years. Rosen et al. concede they cannot exclude the possibility that if methane concentrations came only from boreal sources tropical climate could lag methane concentrations by as much as several decades. Rosen et al. concluded that as even boreal regions that produce methane are located far from Greenland, the mechanism driving abrupt change at this time must have been capable of transmitting climate changes rapidly around the world.

Sources & Further reading

1. Rosen, J. L., et al. (2014). "An ice core record of near-synchronous global climate changes at the Bolling transition." Nature Geosci 7(6): 459-463.