SINGSAAS I., BRANDVIK P.J., S0RSTR0M S.E. SINTEF Materials and Chemistry, Norway

Generally, oil spills in ice are far more complicated to combat compared to oil spills in open waters. Spill response will probably never reach the same level of effectiveness as for open waters due to physical interference by the presence of ice, low temperatures, darkness in the winter months, remoteness and generally poor infrastructure. The oil is less accessible in ice-covered waters and can be spilled on ice/snow, in open pools between ice floes, in open channels behind vessels or even under the ice.

Traditional use of booms and skimmers can be difficult in these conditions.

However, there are also some advantages with oil spills in ice compared to open waters. The weathering rate is normally much slower for an oil spill in ice. This means that emulsification rate and hence viscosity increase may be slowed down resulting in an increased "window of opportunity" for use of most response techniques. The spreading of oil will normally also be much slower resulting in increased oil film thickness that may be favourable for oil spill response.

The ice concentration can become a governing factor in making decisions about equipment selection. One advantage of an oil spill in ice is that the ice can act as a natural containment in a variety of ice features such as floes, snow and ridges. If the oil is located on the ice, among ice floes or under the ice, different approaches to the problem may be required.

Testing and development of oil spill response technology related to Arctic and ice-infested waters have been important activities in many circumpolar countries. These activities have been motivated by vessel traffic through ice, oil exploration in Arctic areas and oil spill incidents. A recent state-of-the-art study indicates that large R&D activities were performed in the late 1980s and early 1990s. Focus has been on the following main subjects:

• Weathering processes of oil in ice,

• Mechanical recovery,

• In-situ burning, and

• Modelling of oil in ice processes.

The leading countries in this R&D work have been Canada, Norway, USA and Finland, but also with activities in Russia and Japan. From approximately 1995 until recently the activity level has been relatively low, however, with some oil skimmer developments in Finland and Norway. Recently some projects have been initiated with focus on dispersant effectiveness, use of chemical herders to enhance in-situ burning and study of fundamental weathering processes for oil in ice.

During the late eighties and early nineties SINTEF performed major laboratory and field studies on fate, behaviour, and weathering of oil under arctic conditions. During a large experimental oil release in the Barents Sea Marginal Ice Zone (MIZ) in 1993, weathering processes were studied over a period of one week and compared to similar data for open waters. This study and other laboratory studies indicate that weathering processes such as water uptake, emulsion stability and viscosity, that are operationally important for oil spill operations, vary with oil type and ice conditions. These processes tend to progress relatively rapidly in open water, but are significantly retarded in the presence of ice. The extreme reductions in these process rates are probably attributable to temperature, ice type, ice coverage and energy conditions in the ice.

However, there is not enough data available today to elucidate the functional relationships underlying these observations, with data being available for only a limited number of oil types and ice regimes through laboratory, meso-scale and field experiments performed in the US and Norway.

Oil-related activities such as shipment of oil and oil products, oil exploration and production are expected to increase in the years to come. Therefore there is a need for further development of tools and technologies to identify environmentally beneficial oil spill response strategies in ice-infested waters. Activities should be planned and executed under international collaboration to avoid redundancy, and should include a combination of laboratory studies, meso-scale testing and field experiments to achieve research goals in an efficient manner.

OIL AND GAS OF ARCTIC SHELF 2006 (PROCEEDINGS OF INTERNATIONAL CONFERENCE)