Quantifying the effects of background concentrations of crude oil pollution on polar sea ice and assessing how sea ice and snow affect PAR transmittance at the ice-ocean interface

Research output: ThesisDoctoral Thesis

Abstract

Sea ice is a highly scattering medium that plays an important role in modulating the radiative budget of the planet through its high value of albedo. Sea ice albedo is sensitive to the presence of light-absorbing impurities such as black carbon; however, the effects of background concentrations of crude oil pollution (≤ 1 ppm) on sea ice albedo have not previously been considered. Therefore, the first component of this thesis is a joint radiative-transfer and modelling study utilising the Tropospheric Ultraviolet and Visible (TUV)-snow radiative-transfer model and the Royal Holloway sea ice simulator (SIS). Modelling shows the presence of different crude oils in sea ice can cause a significant decrease in the value of albedo. Different types of sea ice are sensitive to oil pollution; however, first-year and particularly melting sea ice are most sensitive to oil pollution. To verify the modelling study, weathered Alaska North Slope crude oil is added to lab-grown sea ice and the optical properties of the sea ice are measured with a spectrometer. The TUV-snow model is used to quantify the absorption and scattering cross-section values of the weathered oil in the ice. Fundamentally, the study confirms the optical properties of the weathered crude oil can be measured in a sea ice simulator and the TUV-snow model can be used to quantify the effects of weathered crude oil in lab-grown sea ice. The second component of the thesis examines how sea ice and snow affect photosynthetically active radiation (PAR) transmittance to the ice-ocean interface with the TUV-snow model. The availability of under-ice PAR is critical in driving primary production in the Arctic Ocean, so typical sea ice (0.2–3.5 m) and snow (0.01–1 m) thicknesses are considered for a Winter, Spring, and Summer scenario. Modelled values show a good agreement within one standard deviation with field measurements and a new mathematical technique to predict the value of PAR transmittance at the ice-ocean interface is established. The effect that different sea ice algae chl-a concentrations (0–500 mg chl-a m-2) present in the base of the ice have on PAR transmittance is also parameterised.
Original languageEnglish
QualificationPh.D.
Supervisors/Advisors
  • King, Martin, Supervisor
Award date30 Oct 2024
Publication statusUnpublished - 2024

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