PhD Student

Last application date
Aug 15, 2020 16:09
Department
TW06 - Department of Electronics and information systems
Employment category
Doctoral fellow
Contract
Limited duration
Degree
Master in physics, photonics, electronic or biomedical engineering, or master in physics
Occupancy rate
100%
Vacancy Type
Research staff

Job description

Vacancy for a PhD candidate at Ghent University

“Optical characterization and robotic monitoring of biogenic carbon particles in the upper ocean “

Promotor: Griet Neukermans, Marine Optics and Remote Sensing Group, Faculty of Sciences

Co-promotor: Kristiaan Neyts, Liquid Crystals and Photonics Group, Faculty of Engineering

The downward flux of biogenic particles is essential to help reduce the atmospheric CO2 level and control global climate. Biogenic carbon particles are generated in the sunlit ocean surface and comprise Particulate Organic and Inorganic Carbon (POC and PIC). The differentiation is crucial because the downward flux of POC helps to remove CO2 from the atmosphere while the downward flux of PIC has the opposite effect. Autonomous ocean robots with bio-optical sensors now study biogenic carbon particles in the upper ocean (0-1000 m depth) and provide observations at unprecedented rates. However, an optical sensor to estimate PIC independently is currently lacking, and hence the effect of POC and PIC cannot be differentiated.

The first objective of this PhD thesis is the optical analysis and calibration of delicate calcium carbonate PIC structures. This material is anisotropic and the strong optical birefringence changes the polarization of transmitted light. In the lab of the LCP group they can be observed with a polarization microscope, and they can be studied with a novel cross-polarized beam transmissometer that has been developed by the MarSens group. The aim is to achieve an accurate quantification of PIC (and CaCO3) concentration in seawater samples.

The second objective is the quantification of the downward fluxes of PIC and POC using observations from an array of robotic ocean profilers in the Atlantic Ocean, equipped with bio-optical sensors, including the new PIC sensor. This will allow to quantify the net capacity of the ocean to remove atmospheric CO2. The third objective is to examine the PIC ballast hypothesis, which posits that the downward transfer of POC when associated with high-density PIC is faster and more efficient. Using simultaneous depth-resolved PIC and POC observations at large spatiotemporal scales provided by the robotic profilers, it should finally become possible to address this hypothesis that has been heavily debated due to lack of appropriate observations.

To achieve these objectives the following tasks have to be completed: 1) experimental study of the birefringence properties of various types of CaCO3 particles commonly found in the ocean (LCP lab); 2) mimicking the response of the PIC sensor and testing for various types of CaCO3 particles (LCP lab); 3) validation of the PIC sensor and calibration using various types of CaCO3 particles (MarSens lab); 4) estimation of the mean particle size based on statistical analyses of high-resolution signal time series; 5) deployment of robotic floats to characterize particles and measure optical properties in natural waters (in the field); 6) development of algorithms to characterize the composition and size of biogenic carbon particle populations using a suite of optical measurements (bulk particle backscattering, unpolarized transmission, cross-polarized transmission, chlorophyll fluorescence,…); 7) application of the developed algorithms to quantify PIC and POC to robotic optical observations; 8) examination of the PIC ballast hypothesis.

Starting date: Preferably September 1, 2020

Profile of the candidate

Early state researcher/ PhD student

The candidate will build an optical setup in the lab, analyze the optical properties of particles, make microscopy observations and analyze experimental data obtained at sea.

We are looking for a candidate with at the same time a good understanding of optical measurement systems and a strong interest in marine sciences. The candidate should be willing to conduct experiments in the lab and do work in the field, should have a talent for statistical signal analysis, and a good working knowledge of spoken and written English. This topic is a clear example of multidisciplinary work (involving two faculties) in a flexible and dynamic environment, under the supervision of two research oriented promotors. The candidate should have an open mind and good programming skills (mathematica and/or matlab).

How to apply

Submit your CV and a short letter of interest to .