Hydrological and associated biogeochemical consequences of rapid global warming during the Paleocene-Eocene Thermal Maximum

Journal article

The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal, ~56 million years ago (Ma), is the most dramatic example of abrupt Cenozoic global warming. Characterised by surface temperature increases of between 5 – 9 °C and a rapid onset of less than 20 kyr, the PETM has been widely studied as a natural analogue for future anthropogenic-induced warming. The PETM provides a case study of the impacts of global warming on the Earth system, including both hydrological and associated biogeochemical feedbacks, and proxy data from the PETM can provide constraints on changes in warm climate hydrology simulated by general circulation models (GCMs). In this paper, we provide a critical review of biological and geochemical signatures interpreted as direct or indirect indicators of hydrological change at the PETM, explore the importance of adopting multi-proxy approaches, and present a preliminary model-data comparison. Hydrological records complement those of temperature and indicate that the climatic response at the PETM was complex, with significant regional and temporal variability. This is further illustrated by the biogeochemical consequences of inferred changes in hydrology and, in fact, changes in precipitation and the biogeochemical consequences are often conflated in geochemical signatures. There is also strong evidence in many regions for changes in the episodic and/or intra-annual distribution of precipitation which has not widely been considered when comparing proxy data to GCM output. Crucially, GCM simulations indicate that an intensification of the hydrological cycle at the PETM is associated with regions of both increased and decreased precipitation – evaporation (P – E), although existing proxy data are largely from the regions where GCMs predict an increase in PETM precipitation. We propose that comparison of hydrological proxies to GCM output can be an important test of model skill, but this will be enhanced by further data from regions of model-simulated aridity and simulation of extreme precipitation events.

Authors: Carmichael, M; Inglis, G; Badger, M; Naafs, B; Behrooz, L

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Global and Planetary Change
• Volume: 157
• Pages: 114-138
• Publication date: 2017-08-12
• Acceptance date: 2017-07-31
• DOI: 10.1016/j.gloplacha.2017.07.014
• ISSN: 0921-8181
• Keywords: Data-Model comparisons; Paleogene; Proxies; Climate Models; Paleohydrology; Hyperthermals