The PETM occurred at the boundary between the Palaeocene and Eocene time periods (55.8 million years ago) where a rapid change in climate took place. It lasted around two million years and it is thought that there was a massive release of carbon to the ocean and atmosphere causing a significant global warming.
The PETM represents a 'tipping point' and a potential analogue for future climate change. Little is currently known about the source, quantity or rate of carbon release, nor of the impact of major reorganisation in ocean circulations that took place at this time.
During the PETM, the North Sea area underwent tectonic changes due to the Atlantic rift. The North Sea was semi-enclosed with restricted contact with the Atlantic through the Shetland–Faroe Channel and the English Channel.
During the late Palaeocene, sea level was low and the North Sea was probably isolated and inhabited by an impoverished fauna and flora. In the early Eocene, following the opening of the north-eastern Atlantic, sea level rose leading and a more diverse fauna and flora.
Sediments were deposited in water depths as great as 1000 m and deltas, supplying sand and mud derived from northern Britain, dominated the western part of the North Sea. The eastern part was more mud-prone. Turbidites affected the basin and deposited massive sandstones with little mud.
Most published work studying the PETM has been carried out on core from deep-sea environments. These have a slow sedimentation rate and have been chosen because they are unlikely to contain hiatuses (periods of no sedimentation). The problem with this is that when a core is drilled, the sediment deposited over the PETM time period is very thin (only a few centimetres).
BGS Climate Change scientists have been studying a section of rock core from the North Sea, which has a much more expanded PETM section. Sedimentation rates in the North Sea are much faster than those studied previously so more sediment accumulated during the PETM here.
315 samples were taken and analysed through a range of techniques including:
The study shows that the climate was unstable during this time.
Analysis of the core showed that there are rapid alternations of marine- and land-derived organic matter. These alternations probably represent environmental instability following the c. 5°C rise in temperature at this time.
Our study also shows that there may have been a period of big storms. Palynomorphs in the core seem to have been reworked which suggests erosion and redistribution of sediment by storms. The storms also seem to have lasted for long periods of time (1100 to 1400 years).
If the PETM is taken as an analogue for climate change today, we can expect to see prolonged periods of environmental instability accompanying the 1.1 to 6.4°C temperature rise predicted for the end of this century.
There will be a paper published on these findings soon.