Name of scholarship/program
2013 BAS PhD Studentship - The impact of nitrogen chemistry in snow on atmospheric oxidising capacity
Eligibility and other criteria
Substantial emissions of nitrogen oxides (NOx) and other oxidised nitrogen species from snow have been observed in the polar and midlatitudes. They were found to significantly influence the ""self-cleansing"" or oxidising capacity of the lower atmosphere (troposphere), by altering concentrations of ozone, a pollutant and greenhouse gas, and of the hydroxyl radical (OH), which is responsible for the removal of many atmospheric pollutants. Changes in tropospheric ozone in turn can influence the regional energy balance and climate, whereas OH controls the build up of the greenhouse gas methane. A seasonal maximum of 40% of the Earths land surface is covered by snow or ice, while 7% of the worlds oceans are covered by sea ice. Therefore, the influence of NOx snow emissions on atmospheric composition and climate occurs on large scales and will be most important at remote locations away from anthropogenic emissions. For example, in the Arctic, there is strong interest in near-term mitigation of the current warming by controlling short-lived climate forcers such as tropospheric ozone. The success of reductions in anthropogenic emissions of ozone precursors can only be assessed if the chemical snow source is taken into account. Furthermore, nitrate ice core records hold information on atmospheric NOx, ozone and OH and their climate impacts in the past. However the same processes driving NOx out of the snow alter the nitrate concentrations in snow and firn and complicate at present a quantitative interpretation of the polar ice core record.
Key questions: 1) How can the main drivers of NOx snow emissions be parameterized in numerical models? 2) What is the response of atmospheric oxidising capacity to changes in nitrogen snow chemistry due to modern climate change? 3) What are the trends of polar atmospheric NOx levels and oxidising capacity over the last century?
The student will be located at BAS in Cambridge (M. Frey), but working as an integrated member of two research groups, i.e. spend each year time at the Dept. of Earth Sciences at Royal Holloway University of London (M. King). At BAS the project is embedded in the Chemistry & Past Climate programme which investigates couplings between cryosphere, atmospheric chemistry and climate based on ice cores & polar field campaigns ( http://www.antarctica.ac.uk/bas_research/our_research/current/programmes/chemistry/index.php
The student will develop and validate a 1-D air-snow exchange model of oxidised nitrogen species using available datasets on snow and air chemistry and snow physical properties from Antarctica. The student will interface the new model with a 3-D Chemical Transport Model to quantify the impact of global changes in snow pack chemistry and physics on tropospheric ozone and OH. The student will then match forward-model runs of nitrate profiles in snow, firn and ice for the past 100 yr to existing ice core records in order to constrain recent trends of NOx and oxidant (ozone and OH) concentrations in the polar troposphere. The project doesn't involve any travel to Antarctica but the possibility of carrying out snow chamber experiments to obtain complimentary data for the model parameterizations.
Funded PhD Project (European/UK Students Only): This research project has funding attached. Funding for this project is available to citizens of a number of European countries (including the UK). In most cases this will include all EU nationals. However full funding may not be available to all applicants and you should read the full department and project details for further information.
* 31 January 2013
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