Ocean influence on recent climate extremes

Rationale: 

The last decade has seen an increasing number of extreme weather events (e.g. Fischer et al. 2021) which had significant societal impacts. Unprecedented heat waves and drought conditions in some regions have led to heat related deaths, widespread wildfires as well as reductions in agricultural yield while elsewhere floods have caused significant infrastructural damage and in some case loss of life. 

 

It is on land that these events are felt but in some instances they can be accompanied and sometimes preceded by temperature and salinity anomalies in the ocean. Recent examples include an anomalously cold region in the North Atlantic, a warm anomaly in the North Pacific as well as persistent La Niña conditions in the equatorial Pacific. There is increasing evidence that these ocean anomalies feed back onto the atmospheric circulation and contributed to the development of some recent extreme events  (e.g. Mecking et al. 2019; Duchez et al. 2016).  To what extent these ocean anomalies are the result of changes in the ocean circulation or a response to local atmospheric forcing is far from fully understood. However, this is key to understanding mechanisms of seasonal to interannual predictability in the climate system and to improve preparedness for extreme weather events.  

 

Methodology: 

In this project the student will use a state-of-the-art eddy-resolving global ocean simulation which covers the period from 1958 to present to study the genesis of ocean temperature and salinity anomalies. This simulation is regularly updated and will allow us to investigate any ocean anomaly that may develop during the course of the project.  

 

The goal will be to understand whether these ocean anomalies result from advection, the meandering of major ocean currents such as the Gulf Stream or the Kuroshio, local forcing from the atmosphere or from the re-emergence of subsurface anomalies. Techniques that will be used include lagrangian tracking as well as establishing the force balances (e.g. geostrophy, wind forcing)  that govern the ocean circulation anomalies which precede/coincide with the development of ocean temperature/salinity anomalies.  Additionally, the student will perform idealised  attribution experiments, where atmospheric conditions are either variable or kept constant (respectively climatological). In combination these three approaches will allow us to determine the respective contributions of ocean and atmospheric circulations to ocean temperature and salinity anomalies.

 

Depending on progress the student will also have to opportunity to introduce the simulated ocean anomalies into a coupled ocean-atmosphere model following the approach of Mecking et al. 2019 to assess ocean influence on the  “re-forecasting” of recent extreme weather events.    

 

Location: 
NOC/UoS
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at National Oceanography Centre (NOC).  Specific training will include:

  • Learning to use a range of tools from simple numerical and mathematical models to advanced climate models.
  • Receive training in the use of coding languages such as Python, MATLAB, Ferret and Fortran.
  • Encouraged to join summer schools relevant to their research topic.

The student will join the multi-disciplinary modelling team at NOC, and receive training in analysis of large model/observational datasets. They will acquire a solid background in ocean circulation and climate change theories. They will join an active team of postdoctoral researchers and postgraduate students focusing on the role of the ocean in climate.  They will be encouraged to present results at national and international conferences and have the potential to join a research expedition if interested.

 

Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

 

Background Reading: 

Fischer, E.M., Sippel, S. and Knutti, R., 2021. Increasing probability of record-shattering climate extremes. Nature Climate Change11(8), pp.689-695.

 

Mecking, J.V., Drijfhout, S.S., Hirschi, J.J. and Blaker, A.T., 2019. Ocean and atmosphere influence on the 2015 European heatwave. Environmental Research Letters14(11), p.114035.

 

Kelly, S.J., Proshutinsky, A., Popova, E.K., Aksenov, Y.K. and Yool, A., 2019. On the origin of water masses in the Beaufort Gyre. Journal of Geophysical Research: Oceans, 124(7), pp.4696-4709.