Fate of Dispersed Oil under Ice

At a Glance

Dispersion of oil using either chemical or mineral additives (dispersants) can be an effective way to enhance the natural biodegradation process to remove spilled oil from the marine environment. Research over several decades has shown that these additives can be as effective in near-freezing waters as they are in temperate waters when properly applied.

The use of dispersants can provide an oil spill response option with high encounter rates, high effectiveness and greater responder safety than mechanical response. A new approach for the use of dispersants – dispersant injection for well control events – provides an additional tool that enhances contingency planning for offshore operations. In many cases, including in the Arctic, dispersants could be the best response option to treat an oil spill before it has spread, broken apart, impacted marine mammals and birds, or stranded in sensitive environments.

One of the requirements for efficient dispersion is adequate mixing in the water column, allowing for a cloud of dispersed oil to dissipate rapidly and decrease in concentration. A key parameter is thus the level of turbulence to keep dispersed oil in the water column. The objective of this project is to develop a numerical model capable of predicting the fate of a dispersed oil plume that develops under ice, particularly the resurfacing potential for various scenarios (ice concentration, release type, environmental conditions, oil type, level of turbulence, etc).

The Joint Industry Programme’s (JIP) dispersants technical workgroup has scoped and contracted two projects designed to further enhance the industry’s understanding of dispersant efficacy in ice.

This fact sheet describes the objectives and scope of work for Project 1, “Fate of Dispersed Oil Under Ice”.

Dispersants at a Glance

Oil dispersed and diluted in the water column in the form of droplets biodegrades much faster than concentrated oil on a water surface or on a shoreline. Recent research has found that:

  • Oil biodegrades in temperatures found in arctic waters.
  • Arctic organisms have a similar sensitivity to dispersants (or dispersed oil) as temperate organisms.

In open drift ice conditions, waves may be strong enough to initiate the chemical dispersion of oil. In denser ice conditions the energy provided by a storm, the spring ice melt, or the wash from the propeller of a ship will be adequate.

Dispersants can minimize the impacts of an oil spill by:

  • Enhancing removal of oil from the environment through biodegradation.
  • Minimizing the impact of surface slicks on marine mammals and birds.
  • Preventing oil from reaching sensitive shorelines.