PlioVAR - Pliocene climate variability over glacial-interglacial timescales
Figure 1: Annual mean surface air temperature change in Celsius (Pliocene minus pre-industrial) from the PlioMIP ensemble (redrawn from Haywood et al. 2013).
The Pliocene epoch (~2.6-5.3 million years ago) is one of the best resolved examples of a climate state in long-term equilibrium with current or predicted near-future atmospheric CO2 concentrations, characterised by a globally warmer climate, reduced continental ice volume, and reduced ocean/atmosphere circulation intensity. The available data for this period can be constrained in time by multiple stratigraphic frameworks. The orbital forcing of solar radiation is known precisely, and many of the species existing today were also present. As a result, detailed understanding of climate forcings and feedbacks is possible through both data analysis and data-model integration.
Paleoclimate studies of the Pleistocene period (~11.7k-2.6 million years ago) have demonstrated the value of understanding climate variability on orbital timescales, whereby the unique spatial and temporal signatures of individual interglacials or glacial-interglacial cycles highlight sensitive regions or climate systems.
Recent modeling work confirms that such variability (and regional non-synchroneity) should also be expected in the Pliocene. However, Pliocene data density is lower than for the Pleistocene, and stratigraphical correlation may be more challenging (e.g. benthic d18O oscillations are more muted).
PlioVAR aims to co-ordinate a synthesis of terrestrial and marine data to characterise spatial and temporal variability of Pliocene climate. In order to create such a globally distributed, orbitally-resolved synthesis a community effort is required, ensuring high quality data sets can be integrated using a robust stratigraphy, which is essential to underpin future data/model comparisons.
Building on key priorities identified by the community at the PAGES-sponsored workshop, Multi-proxy approach to the reconstruction of the Pliocene climate, held in Barcelona in September 2014, PlioVAR has identified three over-arching goals:
1. Synthesize late Pliocene climate data with orbital and sub-orbital scale resolution. Specifically, we will tackle two key climate transitions which have known forcings and known chronostratigraphic uncertainty, and which are best constrained with respect to data density: marine isotope stages M2-KM3 (glacial to interglacial transition) and the onset of northern hemisphere glaciation.
2. Examine the tools and experimental design of new climate modeling studies to characterise Pliocene climate variability, including transient model simulations.
3. Identify early Pliocene intervals to which the approaches of (1) and (2) can be applied in PlioVAR Phase 2, to compare and contrast the long-term evolution of Pliocene climate and consider the role of ocean gateways and CO2 forcing in the evolution of the Earth system.
The specific Phase 1 objectives, workplan, and envisaged products are outilned in further detail on the Scientific goals page.
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This group is open to anyone who is interested, to participate contact a member of the Steering Group.
Haywood AM, Hill DJ, Dolan AM, Otto-Bliesner BL, Bragg F, Chan WL, Chandler MA, Contoux C, Contoux C, Dowsett HJ, Jost A, Kamae Y, Lohmann G, Lunt DJ, Abe-Ouchi A, Pickering SJ, Ramstein G, Rosenbloom NA, Salzmann U, Sohl L, Stepanek C, Ueda H, Yan Q & Zhang Z (2013) Large-scale features of Pliocene climate: Results from the Pliocene Model Intercomparison Project, Climate of the Past 9:191-209, doi: 10.5194/cp-9-191-2013