About the Project
Rising temperatures due to the emission of greenhouse gases may be changing atmospheric circulation. This is expressed most clearly by changes in regional weather patterns, and in the frequency and intensity of extreme weather events. One of the most critical components of atmospheric circulation affecting European climate is the jet stream, which consists of ribbons of strong winds that move weather systems across the continent.
Over the last few years patterns of unusually persistent dry/warm or wet weather across Europe have been attributed to the position of the jet stream. The unusual jet stream behavior is potentially linked to changing conditions in the Arctic with reduced summer sea-ice extents and increased temperatures.
However, the relationship between a warming world, the Arctic, and jet stream behavior is difficult to discern with confidence at the present time due to the inherent interannual variability in these systems and the short period in which changes have been observed.
Therefore, examining the nature of the Arctic and its relationship to the jet stream and European weather/climate in the past may be beneficial. During past warm climate states, with elevated concentrations of CO2 in the atmosphere that persisted for thousands of years, the climate system will have reached an equilibrium state where the relationship between atmospheric CO2, mean Arctic sea ice extent and jet stream behavior can be evaluated statistically. Thus warm intervals in the past can provide us with a natural laboratory in which to investigate long-term environmental change, and where climate models can be used to enhance our understanding of atmospheric, oceanic and ice sheet behavior.
The most recent interval of the past that had comparable atmospheric carbon dioxide level to today (~400 ppmv) is the Pliocene epoch (~3 million years ago). It was an interval known to be warmer than the pre-industrial era, with reduced summer Arctic sea-ice extent, and shares a number of parallels to model predictions of climate by 2100AD.
In this project will use climate model simulations to investigate the nature of the jet stream and connections to the Arctic in the Pliocene to enhance our knowledge and understanding of past warm climates and jet stream behavior in a warmer then present world.
A key source of uncertainty in this examination will be the degree of dependency in climate model predictions. This will be evaluated in the context of a broader international climate modelling project (PlioMIP) led by the University of Leeds, where results from multiple climate models will be examined and understood.
Secondly new climate simulations will be produced in which the extent of Arctic sea-ice extent is prescribed in the model and the relationship with jet stream behavior examined.
All model results will be compared with abundant sources of geological proxy climate data for the European sector that provides a means to assess the degree to which different jet stream behaviors in different models contribute to simulated mean climate states that are more or less compatible with available geological climate archives.
References
Dong, B., Sutton, R. and Shaffrey, L. (2014). The 2013 hot, dry summer in Western Europe. Bulletin of the American Meteorological Society, 95 (9). S61-S66. ISSN 1520-0477.
Francis J.A. and Vavrus, S.J. (2015). Evidence for a wavier jet stream in response to rapid Arctic warming. Environmental Research Letters, 10, 014005.
Haywood, A,M., Dowsett, H.J., Dolan, A.M. (2016a). Integrating geological archives and climate models for the mid-Pliocene warm period, Nature Communications, 7, doi: 10.1038/ncomms10646
Haywood, A,M., Dowsett, H.J., Dolan, A.M., Rowley, D., Abe-Ouchi, A., Otto-Bliesner, B., Chandler, M.A., Hunter, S.J., Lunt, D.J., Pound, M., Salzmann, U. (2016b). The Pliocene Model Intercomparison Project (PlioMIP) Phase 2: Scientific objectives and experimental design, Climate of the Past, 12, pp.663-675. doi: 10.5194/cp-12-663-2016.
Howell, F,W., Haywood, A.M., Otto-Bliesner, B.L., Bragg, F., Chan, W.L., Chandler, M.A., Contoux, C., Kamae, Y., Abe-Ouchi, A., Rosenbloom, N.A., Stepanek, C., Zhang, Z. (2016). Arctic sea ice simulation in the PlioMIP ensemble, Climate of the Past, 12, pp.749-767. doi: 10.5194/cp-12-749-2016.
Petrie, R. E., Shaffrey, L. C. and Sutton, R. T. (2015). Atmospheric impact of Arctic Sea ice loss in a coupled ocean–atmosphere simulation. Journal of Climate, 28 (24). pp. 9606-9622. ISSN 1520-0442.
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