ICE NAVIGATION

HISTORY

Sea ice has posed a problem to the navigator since

antiquity. During a voyage from the Mediterranean to

England and Norway sometime between 350 B.C. and 300

B.C., Pytheas of Massalia sighted a strange substance

which he described as “neither land nor air nor water”

floating upon and covering the northern sea over which the

summer Sun barely set. Pytheas named this lonely region

Thule, hence Ultima Thule (farthest north or land’s end).

Thus began over 20 centuries of polar exploration.

FORMATION &TYPES OF SEA ICE

OPEN

WATER ICE

PANCAKE ICE

GREASE ICE

NILAS

Frazil ice

In rough water, fresh sea ice is formed by the cooling

of the ocean as heat is lost into the atmosphere.

The uppermost layer of the ocean is super cooled to

slightly below the freezing point, at which time tiny

ice platelets, known as frazil ice,

form. As more frazil ice forms, the ice forms a mushy

surface layer, known as grease ice

Frazil ice formation may also be started by snowfall,

rather than supercooling.

slush is a floating mass formed initially from snow

and water.

Shuga is formed in agitated conditions by

accumulation of slush or grease ice into spongy

pieces several inches in size.

Waves and wind then act to compress these ice

particles into larger plates, of several meters in

diameter, called pancake ice.

ICEBERGS

An iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice

shelf and is floating in open water. It may subsequently become frozen into pack ice. Alternatively, it may

come to rest on the seabed in shallower water, causing ice scour (also known as ice gouging) or

becoming an ice island

Although icebergs float on ocean waters, they are composed of freshwater.

An iceberg is simply an extraordinarily large mass of ice that has broken off from an ice cap

or glacier where it met the sea. The first stage of iceberg formation occurs

when part of a glacier or ice cap that has been pushed into the sea,

begins to float on the water. Tides and wave action subsequently cause stress fractures,

causing a piece of the glacier to break off and a new iceberg is born! This process is calving.

An iceberg’s extraordinary blue and white coloration is a reminder of its glacial origins.

Glacial ice appears blue because pure ice absorbs other colors more rapidly than blue.

This colour appears in the deepest layers of the ice that are under such high pressure that

all of the air bubbles have been forced out of the ice.

By contrast the surface layers of the iceberg are white

because the air bubbles trapped in the snow layers reflect much of the incident light.

These air bubbles also result in iceberg fizz.

As an iceberg melts, fizzing results from the release of gases that have been held

under pressure, trapped in bubbles for thousands of years!

FORMATION Although icebergs float on ocean waters, they are composed of

freshwater.

An iceberg is simply an extraordinarily large mass of ice that has

broken off from an ice cap or glacier where it met the sea. The

first stage of iceberg formation occurs when part of a glacier or

ice cap that has been pushed into the sea, begins to float on the

water. Tides and wave action subsequently cause stress

fractures, causing a piece of the glacier to break off and a new

iceberg is born! This process is calving.

An iceberg’s extraordinary blue and

white coloration is a reminder of its glacial origins. Glacial ice

appears blue because pure ice absorbs other colors more rapidly

than blue.This colour appears in the deepest layers of the ice that

are under such high pressure that all of the air bubbles have

been forced out of the ice.

By contrast the surface layers of the iceberg are white

because the air bubbles trapped in the snow layers reflect much

of the incident light. These air bubbles also result in iceberg fizz.

As an iceberg melts, fizzing results from the release of gases that

have been held under pressure, trapped in bubbles for

thousands of years!

DRIFTING OF ICEBERGS

Iceberg movement is influenced by direct wind push on its exposed area to an extent far

greater than commonly assumed. Although the bulk of the iceberg is below water, in many

situations wind has a dominant influence on the movement.

In addition to windage on the iceberg and the ocean gradient current, the wind-induced

surface current has the effect of increasing drift speed by about 10 percent for small

icebergs and increasing the angle of drift direction.

The wind force on an iceberg does not result in movement directly downwind, but, because

of the rotation of the Earth (Coriolis effect), windage on an iceberg is 30 to 50 to the right in

the Northern Hemisphere and to the left in the Southern Hemisphere.

They move at speeds of 1 knot, or 24 nautical miles per day.

This iceberg moved 140 kilometres at as much as 3 knots across the Labrador Current and

resulted in an emergency move of the North Atlantic shipping lanes to the south

ICE BREAKERS An ice breaker is a special-purpose ship or boat designed to

move and navigate through ice-covered waters.

For a ship to be considered an icebreaker, it requires three traits most normal ships lack:

a strengthened hull,

an ice-clearing shape,

the power to push through ice-covered waters.

PRINCIPLE:

it uses its momentum to break the ice

High strength hull

Powerful engine

Azimuth thrusters

Icebreakers are constructed with a double hull and watertight compartments in case of a breach.

The ship's hull is thicker than normal, especially at the bow, stern, and waterline, using special steel that

has optimum performance at low temperatures. The thicker steel at the waterline typically extends about 1 m above

and below the waterline and is reinforced with extra internal ribbing, sometimes twice the ribbing of a normal ship.

The bow is rounded rather than pointed, allowing the vessel to ride up over the ice, breaking it with the weight of

the vessel. The hull has no appendages likely to be damaged by the ice,and the rudder and propeller are protected

by the shape of the hull. The propeller blades are strengthened, and the vessel has the ability to inspect and

replace blades while at sea.

DESIGN AND CONSTRUCTION

The optimal shape for moving through ice makes icebreakers uncomfortable in open water

and gives them poor fuel efficiency.

In open-water travel, icebreakers tend to roll side to side to the discomfort of the crew. Some new icebreakers,

such as the USCGC Healy, make use of anti-roll tanks, incompletely filled ballast tanks which span the beam of

the vessel. Ballast water in these tanks is allowed to move side to side, or slosh, as a free surface

A greater concern is how well a ship cuts through waves.The ability of a ship to cut through waves can

greatly affect its fuel efficiency and even its safety in a storm. Most ships use a sharp or bulbous bow

to cut through waves and help prevent waves from slamming the bow of the ship.

DOUBLE ACTING SHIPS

Double acting ship (DAS) is a type of icebreaking merchant ship designed to run ahead in open water

and astern in ice.

Such ships can operate independently in severe ice conditions without icebreaker assistance

but retain better open water performance than traditional icebreaking vessels.

How Double Acting Tankers Work?

A double acting tanker sails in normal sea in the ahead direction, just like any other vessel.

However, when it comes to ice breaking,the astern movement of the ship is utilised.

The aft or stern part of the ship hull structure is therefore made up of special reinforced double skin with a fatigue

life of around 40 years.Moreover, the conventional rudder and propeller is replaced by Azipod system

with fixed pitch propeller and an electric motor of Mega Wattrating.

The azipod system is capable of rotating 360 and the normal ahead speed is above 15 knots.

Additional bow thrusters are also fitted to provide excellent manoeuvrability in narrow channels and ports.

ICE PATROL The International Ice Patrol is an organization with the purpose of monitoring the

presence of icebergs in the Atlantic and Arctic Oceans and reporting their movements for safety purposes. It is operated by United States Coast Guard but is funded by the 13 nations interested in trans-Atlantic navigation.

It was established in 1914 in response to the sinking of the RMS Titanic. "The primary mission of the Ice Patrol is to alert any seacraft traveling the great circle shipping lanes between Europe and the major ports of the United States and Canada of the presence of any icebergs there."

Size Category Height Length

Growler Less than 1 metre (3.3 ft) Less than 5 metres (16 ft)

Bergy Bit 1–5 metres (3.3–16 ft) 5–15 metres (16–49 ft)

Small 5–15 metres (16–49 ft) 15–60 metres (49–200 ft)

Medium 15–45 metres (49–148 ft) 60–120 metres (200–390 ft)

Large 45–75 metres (148–246 ft) 120–200 metres (390–660 ft)

Very Large Over 75 metres (246 ft) Over 200 metres (660 ft)

ICE ACCREATION

Rudder

Inner Bot.

Bulkhead

Fore&Aft

Deck

Bottom

Hull

Unspec/

Ship Side

ICE CLASSES SIGNIFICANCE

Not all ships are built to an ice class. Building a ship to an ice class means that the hull must be thicker,

and more scantlings (aggregate of girders, beams, and bulkheads resulting in stronger structure) must be in place.

Sea chests (openings in the hull for seawater intake) may need to be arranged differently depending on the class.

Sea bays may also be required to ensure that the sea chest does not become blocked with ice.

Most of the stronger classes require several forms of rudder and propeller protection.

Two rudder pintles are usually required, and strengthened propeller tips are often required in the stronger ice classes.

More watertight bulkheads, in addition to those required by a ship's normal class, are usually required.

In addition, heating arrangements for fuel tanks, ballast tanks, and other tanks vital to the ship's operation

may also be required depending on the class.

ARCTIC CLASSES

FINNISH SWEDISH CLASSES

POLAR CLASSES

The following areas are subject to requirements depending on the ice

class selected.

BALTIC ICE CLASSES

- Hull – ice belt

- Machinery output

- Shaft – system

- Propeller

- Mooring

- Heating ballast tanks

- Sea chest

- Air capacity for starting compressor (1A*)

- Rudder and steering gear

- Corrosion protection

ARCTIC ICE NOTATION (ADDITIONAL SCOPE)

- Hull girder transverse strength, line loads due to vessel being trapped

between

moving ice flows.

ARCTIC POLAR AND ICEBREAKER NOTATION (ADDITIONAL

SCOPE)

- Hull materials exposed to low temperatures (DAT-notation)

- Subdivision, intact and damage stability (additional requirements)

- Hull girder longitudinal strength due to beaching and ramming

- General

Items covered by Ice-Class Notation (Baltic, Arctic and

Polar)

ICE CLASS RULES AND OTHER

REQUIREMENTS CLASS

NOTIFICATIONS

EQUIVALENT

BALTICS ICE

CLASSES

VESSEL TYPE ICE CONDITIONS ICE LIMITS

ICE C

ICE 1C

ICE 1B

ICE 1A

ICE 1A*

ICE 1A F*

1C

1B

1A

1A SUPER

ALL SHIP

TYPES

VERY LIGHT ICE

CONDITIONS

- First year ice and

broken channel

0.4 m ice thickness

0.6 m ice thickness

0.8 m ice thickness

1.0 m ice thickness

1.0 m ice thickness

NO RAMMING

ICE O5

ICE 10

ICE 15

POLAR 10

POLAR 20

POLAR 30

ICE BREAKER

Vessels intended

for ice

breaking

-Built for another

main purpose

-ICE BREAKING IS

MAIN PURPOSE

First year ice with

pressure ridges

Multi year ice with

glacial inclusions

ACCIDENTAL

RAMMING

REPEATED

RAMMING

North Atlantic • No ice

• -20 deg c

Baltic sea •1 m ice

• -15 deg c

Barents sea •1.2 m ice • -30 deg c

Kara sea • 2 m ice • -40 deg c

•Multi year ice

THICKNESS OF ICE IN VARIOUS AREAS

CASPIAN 70

WHITE 80

Typical hazards when operating

in cold climate Overstress of hull

• Lack of good ice reports/routing

• Ice restriction vs. commercial pressure on

master

Propulsion failure

• Stuck in ice, crushing of hull or drifting

Aground

• Remote from rescue and spare parts

Icing (stability, safety functions, cargo

operations)

•Black-out ( freezing of ship, crew, difficult restart).

Evacuation problems in ice

Malfunction of fire fighting

Experience/competence

Crew fatigue (additional work load, low

temperature, noise/vibrations, 24 hrs

ICING

A SERIOUS CHALLNGE High Wind Speed

Usually above 18 kts or 9 m/s but

sometimes lower

Low Air Temperature

Below freezing (-1.7 deg c)

Low Water Temperature

Usually below + 7 deg c

Ice accretion on the various

equipment/areas has unequal importance

on the vessel safety.

- Category I : to be kept completely ice

free

- Category II : shall have de-icing

arrangements removing ice within a

reasonable period of time (4-6 hours)

ICE ACCREATION =

WIND+

WAVES+

LOW AIR TEMPERATURE+

OPEN WATER =

ICING

REPORTED ICE DAMAGES

Rudder

Inner Bot.

Bulkhead

Fore&Aft

Deck

Bottom

Hull

Unspec/

Ship Side

Ships side

65%

Rudder

7%

Bottom

10%

Fore&aft

8%

Inner bottom 1%

Bulk head 4%

Deck 2%

TOTAL NO. OF DAMAGES REPORTED

486

FORCES FROM

DRIFT ICE

FORCES FROM

DRIFT ICE

FORCES FROM

DRIFT ICE

FORCES FROM

DRIFT ICE

MANAGING OF COLD CLIMATE RISKS CROSS SECTIONS OF FRAM’ BUILT 1892

Ice forces would lift the vessels out of

the ice, and save her.

A brilliant example of practical risk

management

Protected location. Also with heating (i.e.

adjacent to heated spaces or hot air

ventilation).

Protective covers

Electric tracing (Note ex-requirements)

Heating coils (steam/hot water)

Ice-repellant coating

Self-draining piping/operating procedures

Circulation of liquids (e.g. hydr.oil)

AVOIDING ICING PROBLEMS - METHODS

MEMBRANE LNGC

PROTECTION AGAINST

ICE PRESSURE DAMAGE

Collision with Growlers and

Bergy Bits in open waters Uncouple the containment system

and the

ship side leaving space for indentation

of

the side without damage/deformation

of the

containment system

Increase double hull width

Design for increased energy

absorption

capability of the double hull

Traversing through ice

channel or the ship

completely frozen in Design hull to lift the ship rather than

pushing it down due to the ice pressure

Increase double hull width

Design a stronger protective outer

hull,

stiffer – less deformation

• DA (double acting) - where the ship operates with the stern first when operating in ice. This saves on installed power, and fuel, and makes it possible to optimize the bow of the ship for open water performance. The DAS was made possible through the development of azimuthing electric propulsion--another system which was developed by AARC, together with ABB (Azipod).

• A very new develpoment is the Oblique Icebreaker. By using azimuthing electric propulsion, it breaks ice by moving sideways, utilizing its entire length for breaking a wide channel. This makes it possible to use a relatively small and narrow icebreaker to assist large and wide cargo ships.

Challenges – human factors

Competence and performance of crew is essential for safe

operations

• Availability of experienced personnel?

• Training/experience!

• Increased manning?

• Extreme low temperatures

• 24 hours darkness

• Noise and vibrations in ice

HUMAN FATIGUE

UNDERSTANDING THE

CHALLENGES

CAPTAIN

CHIEF ENG

CADET

Summary…..

Ship operations in cold climate is

much more

than ice strengthening of the ship

alone.

Compliance with basic ice class

rules and

regulations may be insufficient for safe

and

effective ship operations in cold

climate

Risk evaluation for specific trades

and adequate

“winterization” for safe and reliable

operations

must be carried out.

ANY QUESTIONS

THANK YOU