Ice Theory Flashcards
What are the areas affected by ice and most frequented by shipping?
- North Atlantic
- East Coast of Canada
- Baltic
Means to detect Icebergs
- Always use radar and sight to aid in detection of icebergs
By Radar:
- Ice is not a good reflector of radar signals, strength of echo dependant on width, height and aspect of berg
- In good conditions icebergs seen between 4 to 15 miles
- Sector behind iceberg is likely to be free of clutter
- Growlers range of 2 miles and not possible to detect in sea clutter
By Eye:
- Growlers or other small pieces is an indication that an iceberg may be in the vicinity
- Moonlight at night can aid in spotting icebergs
Means of detecting Ice
- Radar unlikely to give an early warning sign. Edge of ice detectable at about 6 miles
- Ice Blink; the luminous reflection of ice on the underside of clouds
- Small fragments of ice indication of larger quantities in the area
- Thick band of fog over edge of sea ice
- Wildlife (especially birds) further out to sea then you would expect
Where can I find ice information for planning a voyage?
- Mariners handbook
- Sailing Directions
- Ocean Passages
- Routing Charts
- Ice reports/ forecasts transmitted by coastal stations
- NAV Area Warnings, (dangerous ice)
When is the iceberg season in North Atlantic?
Feb/March to end of June
What preparations should you make before approaching ice?
- Engine and steering gear are in good working order
- Nav equipment is in good working order
- Vessel is ballasted/trimmed so rudder and propellers are fully submerged
- Crew has appropriate PPE
- Salt/grit is available for icy decks
What would be some considerations before entering ice?
- Do not enter if an alternative route is available
- Look at latest ice report
- Weather and temperature for area if operation
- Availability of Ice breakers / airborne support
- Availability of other vessels in area
- Vessels ice class in relation to type of ice
- State of hull, machinery and equipment
- Draught with respect to ice strengthen belt
- Experience onboard
Considerations when making entry?
- Enter ice from leeward
- Enter at slow speed
- Enter at right angle (bow on)
- Propellers and rudder are vulnerable to damage
- If going astern always have rudder midships
- Glacial ice, pressure ridges and pack ice under pressure should be avoided
- Avoid entering at night or in reduced visibility
- If vessel becomes beset call for icebreaker assistance
What are some typical standing orders given by Master for the OOW?
- Familiarise with Ice section in Mariners Handbook and other relevant pubs.
- Obtain and plot information from ice reports
- Keep a good lookout
- Ensure radars are running and optimised for conditions
- Pass to windward and keep well clear of icebergs
- Advise Master on detection of sea ice
- Do not enter sea ice if Master is not present on the Bridge
How could ice affect the position fixing capabilities of vessel?
- Fast ice along the coast may obscure previously conspicuous points on the coast that could have been used for position fixing
- Ice may obscure important aids to navigation e.g. sector lights
- Buoys maybe have been removed or be out of position due to ice
- Frequent course alterations to avoid ice could make it difficult to get an accurate DR
- Cold winds blowing off the ice may induce abnormal refraction and ∴ range at which objects can be detected
How would you reduce ice accretion on the ship?
- Seek shelter
- Reduce speed to reduce spray and relative wind across decks
- steer towards warmer conditions
- Head into sea at slowest possible speed to maintain steerage
- If possible / safe get crew to remove manually
Factors effecting Nav in high lats in Ice
- High HDOP values
- Abnormal refraction
- Obscured horizon due to ice
- Lack of hydrographic data
- Availability for cel nav fixing
- Ability to plot reliable DR
Outline factors to consider when determining the risks involved in encountering icebergs
- Icebergs underwater area may be much greater then the visible portion above the waterline so should be given a wide berth
- Can be difficult to detect by radar (dependant on height, width and aspect)
- Sea state, breaking waves can be found at base of iceberg
- State of visibility
- Moonlight can be used to aid the visual detection of icebergs
- Can the area be avoided all together
- Vessels speed should be reviewed
- What time of day will they be encountered
Outline factors to consider when determining the risks involved in encountering ice
- Masters experience
- Concentration and type of ice present
- Availability of ice pilot
- Qualifications and experience of own crew
- Type of ship, Ice class?
- Alternative route free from ice
- Limitations of nav equipment
- Expected vis, fog at Grand Banks
- Info available to vessel is up to date
