diff --git a/_pages/research.md b/_pages/research.md index b770111..b80f4d7 100644 --- a/_pages/research.md +++ b/_pages/research.md @@ -10,7 +10,7 @@ toc_icon: "book-open" My area of research is physical oceanography and to date I have been working on ocean mixing. Ocean mixing is a key part of the climate system as it influences the rate and amount of heat and carbon that are taken in by the ocean. -Once such tracers have made it into the ocean, their transport is then strongly influenced by (you guessed it) ocean mixing! +Once such tracers have made it into the ocean, their transport is strongly influenced by (you guessed it) mixing! Broadly speaking ocean mixing can be categorised into *lateral* (isopyncal) and *vertical* (across isopycnals) mixing. Turbulent mixing occurs down to sub-millimetre length scales which can be simulated but the computational cost of doing so, as well as the amount of data that is produced, makes this currently impossible. @@ -19,14 +19,24 @@ Continued research on mixing in the ocean is needed for improvements to how mixi For more information about any of the projects below see the relevant [publications][pubs-page] or feel free to email me. +## Numerical mixing in finite volume ocean models + +The discretisation of advection schemes to transport tracers and thickness in finite volume ocean models leads to spurios *numerical* mixing. +Currently we are looking at methods to diagnose numerical mixing --- more to come soon! + ## Non-linear controls on ocean circulation and mixing in the high-latitude oceans The non-linear equation of state for the density of seawater leads to interesting phenomena, such as a gain in density when two water masses of equal density, but differing temperature and salinity, are mixed. Understanding the effect this gain in density upon mixing and ocean circulation in the high-latitudes was the focus of my PhD. -![image-right](/assets/images/unsw-crest.png){: .align-right style="width: 20%;"} I am based at the [school of mathematics and statistics](https://www.unsw.edu.au/science/our-schools/maths) under the supervision of [Associate Professor Jan Zika](https://sites.google.com/view/janzika/home), [University of New South Wales](https://www.unsw.edu.au/) Sydney, Australia. +For a real riot you can find my [thesis here](https://unsworks.unsw.edu.au/entities/publication/31923b90-a5fa-4c58-8202-d59c7434ef72) or just view the . + +Broadly speaking, when turbulent mixing is the dominant background mixing process in the high-latitude oceans, cabbeling will influence the thermohaline structure of the upper ocean by setting a limiting stability criteria. +When the dominant background mixing process is *diffusive convection*, cabbeling's effect is subtle untile there is a temperature difference of 0.5$\circ$C between layers meaning cabbeling is more prominent in the thermohaline staircases in the Southern Ocean. + +![image-right](/assets/images/unsw-crest.png){: .align-right style="width: 20%;"} I was based in the [school of mathematics and statistics](https://www.unsw.edu.au/science/our-schools/maths) under the supervision of [Associate Professor Jan Zika](https://sites.google.com/view/janzika/home), [University of New South Wales](https://www.unsw.edu.au/) Sydney, Australia. -![image-left](/assets/images/ACEAS_logo_1.png){: .align-left style="width: 50%;"} I am also part of the the [Antarctic Centre for Excellence in Antarctic Science](https://antarctic.org.au/). +![image-left](/assets/images/ACEAS_logo_1.png){: .align-left style="width: 50%;"} I was also part of the the [Antarctic Centre for Excellence in Antarctic Science](https://antarctic.org.au/) for the duration of my PhD. ### Does cabbeling shape the thermohaline structure of the high-latitude oceans? @@ -47,6 +57,16 @@ To our knowledge this was the first turbulence resolving simulation to simulate ![image](/assets/images/dns_schematic_ts_horizontal.png) +### Interplay between cabbeling and double diffusion + +Another small scale process that is prominent in the high-latitude oceans, and drives enhanced mixing, is *doubele diffusion*. +Double diffusion arises because of the differing molecular diffusivities of salinity and temperature; molecular temperature diffusivity is two orders of magnitude larger than molecular salinity diffusivity. +When conditions are favourable, i.e. when there is an *unstable vertical temperature gradient and a *stable* vertical salinity gradient, the differing diffusivities of salinity drive a type of enhanced mixing known as *diffusive convection.* +We investigated how the non-linear nature of the equation of state and double diffusion interact in the high-latitude oceans. +Using Direct Numerical Simulations we found that the non-linearities in the equation of state drive an upward migration of *diffusive interfaces* agreeing with previous laboratory work. + +![image](/assets/images/interface_height.png) + ## Estimating isopycnal mixing Isopycnal (i.e. lateral) mixing in the Southern Ocean is important for the global climate as it influences the uptake and transport of heat and carbon. diff --git a/assets/images/interface_height.png b/assets/images/interface_height.png new file mode 100644 index 0000000..f8d7a63 Binary files /dev/null and b/assets/images/interface_height.png differ