GC10-Pliocene-30
https://doi.org/10.5194/egusphere-gc10-pliocene-30
The warm Pliocene: Bridging the geological data and modelling communities
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Mid-Pliocene not a good analog for future warm climate when regarding atmospheric dynamics in Northern Hemisphere winter 

Arthur Oldeman1, Michiel Baatsen1, Anna von der Heydt1,2, Aarnout van Delden1, and Henk Dijkstra1,2
Arthur Oldeman et al.
  • 1Institute for Marine and Atmospheric Research (IMAU), Utrecht University, Utrecht, the Netherlands
  • 2Centre for Complex Systems Studies (CCSS), Utrecht University, Utrecht, the Netherlands

The Pliocene is often considered the ‘best analog’ for near future climate (e.g. Burke et al, 2018). This notion is mainly based on similar atmospheric CO2 concentration and surface temperatures. However, a ‘best’ analog does not necessarily imply a good analog. We therefore pose the question; to what extent can we treat the mid-Pliocene climate as an analog for a warm future?

We focus on atmospheric dynamics and variability in the Northern Hemisphere winter, for two main reasons: 1. Climate projections are not agreeing on the changes in atmospheric variability we can expect in the future, and 2. The mid-Pliocene exhibits the largest geographical differences to the present-day in the Northern Hemisphere, compared to the Southern Hemisphere. We use the results of simulations from a global coupled climate model, CCSM4-Utrecht, that is a part of PlioMIP2. From a pre-industrial reference simulation (E280), we consider a CO2 doubling experiment at 560ppm (E560), and a mid-Pliocene boundary conditions experiment at 280ppm (Eoi280).

We consider the mean sea-level pressure using 200 years of January-mean data. In response to the mid-Pliocene boundary conditions, we find a large increase in the mean along with a decrease standard deviation over the North Pacific Ocean. This is accompanied with a weakened subtropical jet over the western North Pacific, as well as increased occurrence of a split jet condition over the eastern North Pacific. We connect all these findings to a reduction in the potential vorticity gradient over the western North Pacific. This causes the jet to weaken over the western North Pacific and allows a regime shift towards more anticyclonic wave breaking in the eastern North Pacific. We do not see tendencies towards similar behavior in the CO2 doubling experiment. This suggests that the mid-Pliocene is not a good analog for a warm future climate when considering Northern hemisphere winter atmospheric dynamics.

How to cite: Oldeman, A., Baatsen, M., von der Heydt, A., van Delden, A., and Dijkstra, H.: Mid-Pliocene not a good analog for future warm climate when regarding atmospheric dynamics in Northern Hemisphere winter , The warm Pliocene: Bridging the geological data and modelling communities, Leeds, United Kingdom, 23–26 Aug 2022, GC10-Pliocene-30, https://doi.org/10.5194/egusphere-gc10-pliocene-30, 2022.