Ice conditions forecasts
Canatec has been providing ice forecasting services to companies working in the Arctic for over a decade. Services have been provided for the NE coast of Sakhalin Island, near the North Pole, and in the shear zone and fast ice regions of the Beaufort Sea. In some cases, Canatec staff has gone into the field, and in others forecasts have been provided from the office.
Canatec’s ice forecasting program is an empirical model, which runs in Excel. The data are entered into the spreadsheet every hour or as required, and the model plots graphs in the spreadsheet and provides data which can be displayed in other mapping programs.
Knowledge of the local conditions is also very important for ice forecasting. Episodic events can occur which cause significant changes in the ice conditions, and often the rapid occurrence of hazardous ice at the location of interest. Daily observations for one or two seasons are generally required to identify these situations.
Forecasting in landfast ice is different than forecasting for mobile pack ice, requiring an approach based on past observations and logic.
NE Coast of Sakhalin Island
In this area, tidal currents are the dominant factor moving the ice, with currents often reaching over 2 kts during the peak of the tidal cycle. Non-tidal currents are also present and sometimes can reach over a knot for many days. This is one area where an understanding of the environment is extremely important. Canatec’s ice forecast model includes the tidal currents, and non tidal currents can be estimated from observations and hindcasting. Arrival of possibly hazardous ice at a location down the NE coast of the Island can be estimated based on previous observations of these events for several years. Ice forecasts are provided for up to 3 days and also for a few hours to determine if ice that is near will pass over the site of interest. Situations that require special treatment include breaking of an ice-dam in late May, thick ice arriving from distance shores, and very rapid ice drift due to NE winds driving ice against the island’s north-south shoreline. An understanding of these events is very important.
North Pole
In 2005, Canatec staff provided ice managing and ice forecasting support for the Arctic Coring Expedition (ACEX) at a location 120 nm from the North Pole, within the multiyear polar pack ice. The purpose of the project was to obtain a core from the Lomonosov Ridge in 1,200 m of water. Measurements at the beginning of the project indicated that tidal and non-tidal water currents were essentially zero. Canatec used an empirical wind model, which gave excellent forecasts of ice drift.
Figure below shows an ice forecast presented on a Radarsat image. The yellow line indicates which ice will pass over the wellsite over the next 3 days.
Figure below shows a comparison of forecast and actual ice drift. New forecasts were provided every 12 hours. These diagrams were provided to the captains of the ice management vessels, so that they could anticipate changes in ice drift directions. As a result of ice forecasting, diligent observation of the ice, and ice management, no mechanical losses resulted due to ice.
Beaufort Sea – Seasonal Pack Ice
Canatec staff was involved with ice forecasting and ice management during the “Dome and Gulf Days” back in the 1970 and 80’s – Dome had 4 ice strengthened drillships and Gulf had the Kulluk. Recently, Canatec provided ice management and ice forecasting support for two 3D seismic operations in the southern Beaufort Sea. Ice forecasting commenced during the entry to the Beaufort around Pt Barrow and ended when the vessels exited the Beaufort in the fall. In the area of interest in the Beaufort, there are no tidal currents, but significant non-tidal currents as a result of the Mackenzie River outflow, winds, and atmospheric pressure differences. Canatec’s empirical model worked well in this region as the non-tidal currents appeared to be persistent over many hours or days. Forecasts using Canatec’s model were far better than forecasts using wind alone. The Canatec model forecast several large excursions of the ice, which resulted in changes to the planned seismic program. Both seismic programs were successful and no mechanical problems occurred due to ice encounters.
Small ice pieces (ice cake) are a major problem in 3D seismic surveys. Such pieces occur within the regions of open water indicated on ice charts – regions where seismic surveys should be possible – but are not specifically identified as they are below the resolution of the radar satellite imagery. Such ice pieces are difficult or impossible to see in heavy seas, fog, rain, or darkness. A ship’s radar cannot normally identify the small ice pieces, particularly in heavy seas. However, advanced ice radar with signal averaging improves the situation.
Beaufort Sea – Fast Ice
Canatec has provided ice forecasts for a platform just north of Prudhoe Bay in landfast ice. A different approach was used here. Measurements and analyses made in the past (Vaudrey and Spedding) indicate certain criteria when ice movement occurred, and sometimes ice movements occurred for no obvious reason. Water level is a critical parameter and this was not measured earlier; high water levels can destabilize the ice. A regression analysis of relevant environmental parameters that one would expect associated with water level indicated only minor correlation; the parameters during high water levels were clearly outliers. Observations indicated that high water levels were not associated with local environmental phenomena, but were waves that came north up the Bering Strait and then east along the coast. As a result of observations over the past year, it has been possible to put together a number of criteria to monitor daily or more frequently (including water level at the site and neighboring site where the wave is evident 24 hours before Prudhoe Bay), so that a risk assessment of ice movement can be provided.
Purchasing
Contact Svetlana Machurina at +1 403 228 0962.
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