Fritt-Rasmussen, J., Petrich, C., Renvald, L., Wegeberg, S. & Gustavson, K., 2022. Small-scale laboratory experiments on burning crude oil in ice melt pools. Aarhus University, DCE – Danish Centre for Environment and Energy, 33 pp. Scientific Report No. 514. http://dce2.au.dk/pub/SR514.pdf
Responding to an oil spill in high-Arctic marine ice-infested waters is extremely challenging. In situ burning (ISB) of oil spills is recognised as an effective oil removal method for oil spills in both open and ice-infested waters. The presence of ice can contribute to reducing oil weathering and under the right circumstances contain the oil slick as a thick ignitable layer on the surface. Therefore, ISB is often mentioned as a promising method for oil spill response in the Arctic.
The aim of this project was to increase the knowledge base for combatting oil spills in ice-infested waters by ISB. The project included small-scale laboratory burns of oil released from ice. During freezing, ice grows downwards and can encapsulate oil lying beneath it (NORCOR 1975; Faksness 2008; Nelson 1982). Such oil accumulated under the ice tends to move upwards within the ice during winter due to density-mediated migration and appear un-weathered at the surface when the ice starts to melt. The migration is occurring through the brine channels in the ice.
The study was designed to imitate a spring melt pool situation, where oil captured in the ice is released during the spring melt and contained in melt pools and subsequently burned. The set-up consisted of an ice block with an indentation/cavity in the top (the melt pool), a connecting channel (the brine channel) and an oil reservoir in the ice.
The purpose was to study the driving mechanisms for burning oil in an ice melt pool still connected to oil remaining in the ice. It was hypothesised that the heat from the burn would result in an increased release rate/migration of oil from the reservoir, thereby increasing the oil amount removed from the ice.
The results from the burns suggested that the diameter of the brine channels as well as the hydrostatic pressure of the oil are the driving mechanisms for oil migrating from the reservoir to the oil pool. In addition, the results indicated that the heat from the burn was used to melt ice rather than burn oil, which is expected to lead to increased oil release rates from oil-permeated sea ice in a field setting. However, we expect this effect to decline with increasing pool diameter.
It is recommended to undertake larger-scale experiments with more replicates to be able to conclude on the different results from the experiment.
