Dive Atlas of the World. Jack Jackson
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Название: Dive Atlas of the World
Автор: Jack Jackson
Издательство: Ingram
Жанр: Спорт, фитнес
isbn: 9781607653622
isbn:
■ O-rings, including a few for cylinder/regulator fitting
■ Any necessary tools for small repairs, and batteries
Regulators travel best when disassembled, and you may need special tools to re-assemble them. Diving computers and depth gauges should travel as hand baggage on aircraft or in a pressure-proof container.
TRAVELLING DIVER’S MEDICATIONS
A minor ear or sinus infection can ruin a diving holiday, especially in a remote area or on a live-aboard boat. Being prepared can save your vacation. Many divers travelling to a live-aboard boat assume that they do not require antimalarial prophylactics because they will spend most of their time at sea where mosquitoes do not exist. However, it only needs one mosquito bite in an airport and there is always the chance of aircraft or boats being delayed, forcing extra time at risk on land.
The correct malaria prophylactic should be taken where necessary and most divers carry decongestants, drops that dry out the ears, antihistamine cream, sunburn lotion, lip-salve, anti-diarrhoea medicine, rehydration salts, antibiotics, seasickness remedies and insect repellents.
Masks that keep ears dry are now available.
Remember that most decongestants and seasickness remedies can make you drowsy and should not be taken before diving.
Squirrelfish (Sargocentron Spp) of different species form loose aggregations in protective crevices during the day and feed at night.
Whale watching has become a popular pastime in the Atlantic, often bringing in a considerable income from tourism. Whales are identified by markings and scars on their tails.
THE ATLANTIC OCEAN
by Jack Jackson
THE ATLANTIC IS THE SECOND LARGEST of the world’s oceans. The boundaries defining its northern limits are not universally accepted, but the two most common latitudinal boundaries are 65° North and the Arctic Circle – 66° 32’ North. The western boundary is the Americas and the eastern boundary is Europe and Africa. To the south the most widely accepted limit between the Atlantic and the Pacific oceans is the Drake Passage. Between the Atlantic and Indian oceans it is the 20° meridian East through Cape Agulhas at the southern end of Africa.
With an area of about 82,000,000 sq km (31,660,000 sq miles) without its attendant seas and 106,460,000 sq km (41,100,000 sq miles) with them, the Atlantic covers one-fifth of the earth’s surface and has the largest river drainage of the world’s oceans.
CONDITIONS AND COASTAL HABITATS
In the north there are temperate waters and some unusual conditions caused by the warm Gulf Stream. There is temperate water diving off eastern North America, while Bermuda, Florida, the Bahamas and the countries at the northern end of South America are Caribbean-like. Brazil’s coastline has conditions from Caribbean-like to temperate. Argentina has a long temperate coastline and large mammals including some unique Orcas that hunt at the edge of the beach.
Europe has lots of temperate water diving. Islands off the west coast of Africa have Mediterranean conditions when the weather is fine. Central west Africa has the wettest climate in Africa and large river outlets give murky waters. Near the coast divers have died of dysentery carried in river run-off, but diving is safer at islands well offshore such as Principe. Namibia’s coast is cold and murky, so most diving is done in inland sinkholes. There is diving off the Atlantic coast of South Africa. The remote islands of Ascension, Saint Helena, Tristan da Cunha, and the Falklands have good temperate water diving.
Most islands are in the Caribbean. The British Isles, Falkland Islands and Newfoundland are continental. Iceland, the Azores, Ascension, Saint Helena, Tristan da Cunha, the South Sandwich Islands, the West Indies and Bermuda are exposed tops of submarine ridges. The Canaries, Cape Verde and Madeira rise from the continental margins of Africa while the Bahamas are coral islands lying on the Blake Plateau.
Off South Africa, Great White Sharks are observed from the safety of a steel cage. They are drawn closer with chunks of fish or meat.
Shipwrecks are a major draw off the East Coast of North America. This is the torpedo room of the German submarine U–352.
Cuckoo Wrasse (Labrus bimaculatus) are among the more colourful fish of the Eastern Atlantic. They live up to 17 years.
The large air masses and the resulting winds from North America determine most of the weather over the North Atlantic. In winter westerly winds at altitude push cold air from Canada and Alaska to the Atlantic seaboard. Where cold polar air meets mild air from the Gulf of Mexico or the Gulf Stream, low-pressure areas form and develop into strong vortices as they move towards Newfoundland and Iceland. These cyclonic storms carry tropical heat and moisture north and help to maintain the prevailing westerlies of the mid-latitudes, which are half as strong and about 10° further north in summer than in winter.
Iceland is normally dominated by low pressure, but in some winters high pressure systems prevail and storms leaving the North American coast are blocked and diverted to the Azores. Warm maritime air that normally gives Europe relatively mild winters is replaced by cold air from the European Arctic and Siberia.
HURRICANES
Between 15° and 30° North, high pressure prevails so the weather is usually fine. South of this, the northeast trade winds blow steadily. However, during late summer and early autumn, large amounts of heat are released when vapour rises from the warm ocean and then condenses as heavy showers. This can develop into tropical-storm vortices called hurricanes, which often move clockwise around the North Atlantic high-pressure belt and into the prevailing westerlies, ending up around Iceland. Occasionally they reach the British Isles and even the Azores.
Fog banks off the Grand Bank in summer are due to moisture in warm air from the continent and the Gulf Stream condensing as it flows over the cold Labrador Current.
WINDS AND TIDES
In the South Atlantic a belt of westerlies extends from roughly 40° South almost to Antarctica. The South Atlantic high-pressure region is centred around 30°S. Wind rotation around the high-pressure region is opposite to that in the northern hemisphere because of the effect of the earth’s rotation (Coriolis Effect). This circulation gives the southeast trade winds on the northern side of the high-pressure region, which meet the northeast СКАЧАТЬ