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Wavy Jets and Arctic Climate Change

Prof Alan Haywood (SEE), Dr Dan Hill (SEE), Dr Jochen Voss (SoM), Dr Aisling Dolan (SEE)

Project partner(s): Participants of the Pliocene Model Intercomparison Project Phase 2

Contact email: earamh@leeds.ac.uk

Rising temperatures due to the emission of greenhouse gases may be changing atmospheric circulation (Petrie et al. 2015). This is being observed through changes in regional weather patterns, and in the frequency and intensity of extreme weather events (Dong et al. 2013). One of the most critical components of atmospheric circulation influencing European climate is the jet stream, which consists of ribbons of strong winds that move weather systems across the continent.

Over the last several years patterns of unusually persistent dry/warm or wet weather across Europe have been attributed to the behaviour of the jet stream (Dong et al., 2013). The unusual jet stream behaviour is potentially linked to changing conditions in the Arctic with reduced sea-ice extent and increased temperatures (Francis & Vavrus, 2015; Petrie et al., 2015). Therefore, understanding the changing nature of the Arctic, its relationship to jet stream behaviour, and European weather/climate is very important.

Warm intervals in Earths past provide a natural laboratory in which to investigate long-term environmental change, and climate models have been used to enhance our understanding of atmospheric, oceanic and ice sheet behaviour (Haywood et al., 2016a). The most recent interval of Earths past known to have had a comparable atmospheric carbon dioxide (CO2) level to today (~400 ppmv) is the Pliocene (~3 million years ago). It was an interval known to be warmer than the pre-industrial era, with reduced Arctic sea-ice extent (Figure 1 & 2), and shares a number of parallels to model predictions of climate at the end of the century (Haywood et al., 2016a).

In the context of a broader international climate modelling effort (see international partners section below), this project will use climate model simulations to investigate the nature of the jet stream and connections to the Arctic in the Pliocene to greatly enhance our knowledge and understanding of past warm climates, and critically, their significance in the context of future climate change.

Figure 1: Mean Arctic sea ice concentrations (%) during summer in the pre-industrial simulated by 8 different climate models (Howell et al., 2016).

 

Figure 2: Mean sea ice concentrations (%) during summer in the Pliocene simulated by 8 different climate models (Howell et al., 2016).

Objectives

  • Investigate and develop appropriate methods to diagnose the behaviour and variability of jet stream flow.
  • Examine the relationship between the large-scale features of Northern Hemisphere climate and jet stream behaviour.
  • Assess model differences in the representation of the jet stream for the Pliocene through multi-model comparison.
  • Examine the effect that different scenarios of Arctic warming have on model predictions of jet stream behaviour.
  • Compare and contrast climate simulations for the European region during the Pliocene, which display different characteristics of jet stream flow, to available geological climate data.
  • Compare and contrast Pliocene results with predicted jet stream behaviour using model experiments designed to simulate the climate of this century.

Potential for high impact outcomes

Understanding the relationships between Arctic sea-ice cover and jet stream behaviour for a climate of the past that has elevated concentrations of CO2 will provide valuable insights into weather and climate variability of the near future. The student will be guided by a brand new science plan recently formulated for the 2nd Phase of the Pliocene Model Intercomparison Project (Haywood et al., 2016b). Phase 1 led to the publication of numerous high impact papers in Nature journals. Phase 2 experiments are underpinned by the very latest syntheses of geological information available. The proposed research has the potential to contribute to the next Intergovernmental Panel on Climate Change Assessment Report.

Training

The PhD student will be embedded within a vibrant and dynamic research group in the School of Earth and Environment (Palaeo@Leeds).  Palaeo@Leeds has experts in past climate and ice sheet modelling, as well as specialists in marine and terrestrial palaeoenvironments. The student will be supported and fully trained in coupled ocean-atmosphere modelling, gaining programming skills. The student will analyse existing climate model simulations, learn to perform new experiments, learn how to compare results from different models, and learn appropriate methods for diagnosing the behaviour of the jet stream. As such the student will become an expert in assessing atmospheric circulation relating to jet streams. Our link to Jochen Voss in the School of Mathematics will provide valuable expertise in numerical analysis of model results and statistics. The student will attend the Urbino Summer School in Palaeoclimatology (Italy) and have the opportunity to attend various conferences during the project (e.g. American Geophysical Union and European Geoscience Union). Through our established collaborations the student will also have an opportunity to visit and work with scientists from the Unites States Geological Survey as well other international modelling groups involved in the Pliocene Model Intercomparison Project Phase 2 (led by the University of Leeds and the U.S. Geological Survey) in the U.S., France, Germany, Norway and China. The research has the potential to make a highly valuable contribution to the next Intergovernmental Panel on Climate Change Assessment Report.

Student Profile

It is necessary for the candidate has an undergraduate degree (2.1 or higher) in Atmospheric Science, Environmental Science, Earth Sciences, Mathematics or Physics. A strong interest in climate modelling with previous programming experience is desirable, although previous experience is not required as our training will equip the student with the skills necessary to use climate models. 

International Partners

Through our established collaborations the student will have an opportunity to interact and work with scientists from the Unites States Geological Survey as well other international modelling groups involved in the Pliocene Model Intercomparison Project Phase 2 in the U.S., France, Germany, Norway and China.

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.

Related undergraduate subjects:

  • Atmospheric science
  • Earth science
  • Environmental science
  • Mathematics
  • Physics