Our results provide the first evidence that the North Sea became stratified from 103 yrs before the CIE onset (above 2618 m, Fig. 9). This is significant as Nisbet et al. (2009) hypothesised that the proximal Kilda Basin became stratified and anoxic before the CIE, allowing significant build-up of methane and CO2 at depth. They proposed that overturning of this basin could have released greenhouse gases and triggered the CIE, although there is currently no direct evidence as marine records from the Kilda Basin remain rare (Nisbet et al., 2009). Our North Sea records likely indicate enhanced stratification also of the proximal and linked Kilda Basin before the CIE (Fig. 1). Evidence for the linkage of the North Sea, Kilda and Arctic Basins comes from the coincident onset of A. augustum and laminated sediments at the CIE onset in sections from the North Sea (this study), Spitsbergen (Harding et al., 2011), and Lomonosov Ridge (Sluijs et al., 2006). Although our results evidence a probable stratified Kilda Basin before the CIE, proxies for overturning are now needed to further test the Kilda basin hypothesis.
CIE onset
before
from 103 yrs
yrs
CIE onset
before
above 2618 m
m