On a North Atlantic passage in February you observe growlers in the water and an ice report positions an iceberg 20nm to the N. Describe the ice hazard types you might encounter and your watchkeeping response.

A. Ice types and hazards: (1) ICEBERG — calved from glaciers (Greenland), extends 7/8ths below waterline; only 1/8th visible above; may have submerged "spur" extending well beyond visible mass; detected by radar but small growlers are difficult to distinguish from sea return; hardness equivalent to concrete — contact at speed is catastrophic; (2) GROWLER — fragment of iceberg, awash or nearly awash; very difficult to see in swell; poor radar return; the most dangerous ice encounter hazard; (3) BERGY BIT — piece larger than growler but smaller than iceberg; still largely submerged; (4) SEA ICE (pack ice/floe) — formed from frozen seawater; less dense than icebergs; navigable in some conditions but beset-risk. Watchkeeping response: (1) Reduce speed — ice in vicinity requires a safe speed that allows stopping before an undetected growler; (2) Increase radar range scan — regularly check 6nm, 12nm, 24nm scales; (3) Post additional lookout forward; (4) Do not rely solely on radar — many growlers are not detected; (5) Report iceberg position to MAIB and broadcast to other vessels (SOLAS V/31); (6) Consider route alteration to increase distance from reported positions.

B. Icebergs are detectable by radar at long range. Maintain normal speed and rely on the radar to identify all ice in the vicinity — modern radar can distinguish ice from sea clutter reliably.

C. A 20nm separation from reported icebergs is sufficient safety margin. Continue on course and reduce speed only if ice is sighted visually within 5nm.

D. Only growlers and bergy bits are a hazard to shipping. Full icebergs are detected easily and vessels can manoeuvre around them without difficulty.

A. Buys Ballot's Law (Northern Hemisphere): stand with your back to the wind — the centre of lowest pressure (the depression) lies approximately 90° to 120° to your LEFT (and slightly forward). Wind from SW, standing with back to SW means facing NE — the depression centre lies to the NW or NNW of your position. Backing wind (SW to S) means the depression is approaching from the west or northwest — you are in the WARM SECTOR of an approaching depression (between the warm front and cold front). Expected sequence: (1) Barometer continues to fall; (2) Wind continues to back and freshen; (3) Warm front will pass with steady rain; (4) Wind veers to W-NW as cold front arrives; (5) Violent squalls, heavy rain, and rapid pressure rise as the cold front passes; (6) Barometer rises rapidly; (7) Wind veers to NW-N; clearing showers with good visibility.

B. Stand facing the wind — the depression lies 90° to your right. Wind from the SW means the depression is to the NW. Veering wind means the depression is passing to the south.

C. Buys Ballot's Law only applies in the Southern Hemisphere. In the Northern Hemisphere, the depression lies to the right of the wind direction.

D. A falling barometer at 2 hPa/hour indicates a stationary anticyclone nearby. The backing wind confirms high pressure to the east.

A. ADVECTION FOG — the dominant fog type on the Grand Banks. Mechanism: warm, moist air from the Gulf Stream (sea surface temperature 15-20°C) flows northward and encounters the cold Labrador Current (SST 2-8°C). The warm air is cooled below its dew point by contact with the cold sea surface, causing condensation — fog forms. Characteristics: persists regardless of time of day (unlike radiation fog which disperses with daytime heating); very dense, may last days; geographically fixed to the temperature boundary zone. Other fog types: Radiation Fog — over land, forms on calm clear nights as the land surface cools; disperses with morning sun; does not persist at sea. Sea Smoke (Arctic Sea Smoke) — cold dry air over relatively warm water; water vapour condenses immediately above the surface into low wisps — opposite mechanism to advection fog. Avoidance: route planning to avoid the Grand Banks fog zone (approximately 43°-47°N, 45°-55°W) in spring/summer; alternative routes further north or south.

B. Radiation fog forms on the Grand Banks because the sun cannot penetrate the ocean and heats the sea surface at night. This is the most common fog type at sea.

C. Grand Banks fog is frontal fog forming ahead of Atlantic depressions. It is associated with the warm front and disperses when the front passes.

D. Steam fog forms when the cold Labrador Current water evaporates into the warm overlying air. This is only 1-2 metres deep and does not significantly affect navigation.