Ocean Regions: Littoral Zone - The Navy & the Littoral Zone

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TERRAIN-FORCED THUNDERSTORMS

These storms usually occur in the afternoon and can cause wind shear, heavy rain, hail and high winds. They are a danger to airborne operations and can hurt communications and the ability to move around the land.

OFFSHORE WIND

Winds blowing off the shore can travel at speeds of 4 to 6 knots and extend 5 to 10 nautical miles. These winds, which can carry smoke, fog and dust offshore, can reduce visibility and hurt coastal operations.

ONSHORE WIND

Winds can blow from the ocean onto the shore at speeds of 8 to 14 knots and extend as much as 5 to 10 nautical miles. They can make the waves taller and, if coastal hills are present, create clouds as the moist sea air is lifted over the hill. These winds make periscope and mine detection harder and can block inland targets as the waves become higher.

TERRAIN-FORCED WIND

Features on land can disrupt the wind's flow. For example, the wind patterns above a mountain can differ from the wind patterns around the mountain. This creates wind shear. Wind shear happens when wind flows in different directions or at different speeds over a short amount of space. How does this affect the Navy? Think about aircraft flying in low to drop parachutes or gliders or helicopters flying in to drop off or pick up soldiers. The wind shear could cause turbulence, which would make these missions dangerous.

RIVER DISCHARGE

Where a river meets the ocean, fresh water flows into salty water. The colder river waters are often less dense than the warmer ocean waters. The density differences can create distinct layers in the relatively shallow waters. A submarine or diver operating in this environment would have to alter its buoyancy to adjust to the density changes. Also, a river flowing into the ocean often brings a load of sediment into the ocean. This can alter in the shape of the ocean bottom, which would create problems for submarines and divers.

REEFS, BARS & CHANNELS

Reefs are usually found in shallow tropical waters, but bars and channels can form almost anywhere. Bars and channels are known to change slowly with the turn of the seasons or daily with tides and currents. Boats, submarines, swimmers and torpedoes must all take care when approaching any of these. These features may also get in the way of sonar systems.

SHIPWRECKS

Most shipwrecks occur near shore. They can be a problem to avoid, or they can help submarines, which can linger close to them and avoid being spotted.

BIOLUMINESCENCE

Some organisms that float on the surface can produce their own light. This ability is called bioluminescence. Swimmers, periscopes, boats and submarines must all be careful when traveling along the water's surface. Disturbances cause the bioluminescent organisms to glow. Because of these glowing organisms, a ship's wake may be visible for 6 nautical miles!

INTERNAL WAVES

Tides or currents may disturb water, which is separated into distinct layers because of density. These disturbances can change the depth of the thermocline. Submarines and other submerged vehicles may have to alter their buoyancy to maintain depth.

LITTORAL MARINE LIFE

Dangerous marine life (e.g., jellyfish, scorpion fish, saltwater crocodiles) may be present, and typically there is more marine life present than in near-surface open ocean. These creatures may harm divers.

BEACH PROFILE

Sand profiles change seasonally and often after a storm. Beaches with sandbars often have rip currents. Equipment-laden troops can drown in the deep trough in between a sandbar and the shore. Waves can damage amphibious watercraft.

COASTAL CURRENTS

Coastal currents are caused by the wind, tides and sea surface slope and can travel at speeds greater than 4 knots. These currents can change rapidly, making charts of the currents useless. These currents affect all operations near the coast.

LAND-FAST ICE

Sea ice attached to the coast can extend on top of waters with 2 to 25 meters (6.5 to 82 feet) depth, sometimes up to 100 to 200 kilometers (62.1 to 124.2 miles) depth around offshore islands. The ice, which can be 2 to 3 meters (6.6 to 9.8 feet) thick, can completely block or severely restrict channels and bays. The ice also changes the salinity of the water. Ice causes problems to ships and submarines, which have to steer around or dive beneath it. It can block swimmers and torpedoes.