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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead supervisor: Xin YangBritish Antarctic Survey

Co-supervisor: Rachael Rhodes, Earth Sciences; Ken Carslaw, University of Leeds; Leighton Regayre, University of Leeds; Markus FreyBritish Antarctic Survey

Brief summary: 
Current climate models are missing an important source of sea salt aerosol that could have a significant impact on the polar climate in the future.
Importance of the area of research concerned: 
Atmospheric aerosol particles directly impact the polar energy balance by absorbing and scattering solar radiation. In addition, aerosol particles act as cloud condensation nuclei (CCN) or ice nucleating particles (INPs), which impact the radiative balance indirectly. The magnitude of the influence of aerosol particles on the polar radiative balance is highly uncertain. One critical issue is that current climate models are missing a major source of polar sea salt aerosol (SSA) in the winter months. Field data demonstrate that SSA is produced via sublimating saline windblown snow particles over sea ice. Recent work, using a comprehensive aerosol scheme in a model, shows that this blowing snow may account for up to 40% of the Arctic wintertime aerosol, which warms the Arctic basin surface. However, this new SSA has not been included in most climate models, including the UK Earth System Model (UKESM). Therefore the climate impact of this newly identified SSA remains uncertain. Our warming climate and projected sea ice loss indicates that this sea-ice sourced SSA could face a dramatic change in the near future, with implications for polar and global atmosphere and environment.
Project summary : 
UKESM is the UK’s state-of-the-art coupled climate model used for future climate projections. However, the current version exhibits large biases in both sea salt mass concentration and cloud coverage in the polar regions, with the largest biases occurring in winter when sea ice extent reaches its annual maximum. This shortcoming currently prevents us from making robust future predictions for polar climate. The missing SSA source produced over sea ice is likely to be one reason for the poor model behaviour. This project aims to improve the UKESM’s ability by implementing the new SSA scheme and evaluating the model’s current SSA parameterisations. The optimised version of UKESM will then be used to comprehensively assess the climate impact of SSA for the recent past, present-day and near future. Particular focus will be given to the high latitude energy budget and surface mass balance.
What will the student do?: 
The student will modify UKESM’s aerosol scheme, perform model evaluation, and use the revised model to explore the polar climate impact of SSA. The first task is to improve the model’s SSA simulation ability. This student will employ Perturbed Parameter Ensemble (PPE) technology coupled to UKESM to constrain key parameters and evaluate the model against existing field observation. The updated model should be able to reproduce (i) the observed large gradient of surface sodium concentration between coastal and inland polar ice sheets, and (ii) the sodium maximum observed in polar winter. The second task is to use the new model to estimate the climate impact of the sea-ice sourced SSA source for the recent past, present-day and near future. This project will be closely related to the BAS National Capability International research programme – SURFEIT and the EU-H2020 project CRiceS. The student will work closely with the relevant scientists, particularly modellers, to develop the model, exchange scientific ideas, and present findings. The updated model version should be used in the next CMIP7 (Coupled Model Intercomparison Project phase 7) and will contribute to the next IPCC report.
References - references should provide further reading about the project: 
Gong, Xianda, Zhang, Jiaoshi, Croft, Betty, Yang, Xin, Frey, Markus M., Chang, Rachel, Creamean, Jessie, Kuang, Chongai, Martin Randall, Sedlacek, Arthur J., Uin, Janek, Willmes, Sascha, Zawadowics, Maria A., Pierce, Jeffrey R., Shupe, Matthew D., Schmale, Julia, Wang, Jian, Arctic warming by abundant fine sea salt aerosols from blowing snow, Nature Geoscience, doi:10.1038/s41561-023-01254-8, 2023.
Yang, Xin , Frey, Markus M. , Rhodes, Rachael H., Norris, Sarah J., Brooks, Ian M., Anderson, Philip S., Nishimura, Kouichi, Jones, Anna E. , Wolff, Eric W.. (2019) Sea salt aerosol production via sublimating wind-blown saline snow particles over sea ice: parameterizations and relevant microphysical mechanisms. Atmospheric Chemistry and Physics, 19. 8407-8424. 10.5194/acp-19-8407-2019.
Frey, Markus M. , Norris, Sarah J., Brooks, Ian M., Anderson, Philip S., Nishimura, Kouichi, Yang, Xin , Jones, Anna E. , Nerentorp Mastromonaco, Michelle G., Jones, David H., Wolff, Eric W.. (2020) First direct observation of sea salt aerosol production from blowing snow above sea ice. Atmospheric Chemistry and Physics, 20. 2549-2578. 10.5194/acp-20-2549-2020.
You can find out about applying for this project on the British Antarctic Survey (BAS) page.