detail from: KRK Art dizajn

OCEANS and SEAS OF PLANET EARTH

SIMO JELAČA, Dr sci.

The waters of the planet Earth cover 71% of its surface, and the oceans occupy 96.5% of it. The five oceans in order of size, from largest to smallest, are: Pacific, Atlantic, Indian, Southern Ocean and Arctic. And the seven continents, from largest to smallest, are: Asia, Africa, North America, South America, Antarctica, Europe and Australia.

Water temperatures in oceans and seas vary seasonally between summer and winter, in proportion to the absorption of solar energy on water surfaces, and range from 300 C to -200 C, from the equator to the poles of the planet. Ocean and sea temperatures decreased from 1880 to 1910 and then increased from 1910 to 1940. Seasonal changes in sea and ocean temperatures are greatest during late summer and early fall. Going from the equator to the earth's poles, the ocean waters receive less and less solar energy, which decreases up to 40%.

Atlantic waters are slightly warmer than Pacific waters, the warmest is the Indian Ocean, and the coldest is the Arctic Ocean. Even in 1903, an ocean temperature of -25.60 C was recorded near New Zealand, and in the Gulf of Kuwait, the highest sea temperature was recorded in 2020, in which an egg could be boiled. The lowest recorded ocean water temperature is -42.50 C. And the coldest water temperature was recorded in Watson Lake in Canada -480 C. When the earth cools down at night, the ocean waters do not change significantly in temperature, because the surface waters mix with the deep waters. The temperature of ocean waters at depths of about 1000 m is on average 5o C, and at depths of 2000 m it is around 2-30 C. At the time of the sinking of the Titanic, the water temperature was -20 C. Sea and ocean waters contain more heat than the earth's atmosphere. As the planet Earth is now warming, more ice is melting, oceans and seas are warming, water levels are rising and corals are becoming increasingly white.

The salinity of sea and ocean waters is not the same everywhere. The Atlantic is the saltiest of the oceans. Approaching from the earth's poles to the equator, the salinity of ocean water decreases. Some seas are saltier than others, for example the Mediterranean is slightly saltier than the ocean. One of the saltiest seas is the Caspian, although it is like a lake, it has no contact with other seas, and the saltiest sea is the Dead Sea. The salinity of the ocean is on average 35 parts per thousand, and the salinity of the Dead Sea is 240 parts per thousand (ratio of salt to the amount of water).

The colors of seas and oceans are predominantly blue, although in some seas the water is green or blue-green. There are also shades of yellow to yellow-brown. Water mostly absorbs red sunlight and reflects blue. The colors of the waters of the Atlantic and the Pacific differ in shades due to different contents of sediments. Waters containing more plankton reflect a green color. Their shades depend on the type and density of plankton. The color of the Mediterranean is mainly due to the reduced content of plankton. Greek sea waters are rich in plankton and are therefore very clean.

The pollution of the seas and oceans has become too great and, unfortunately, it is increasing. Official data indicate ocean pollution, which already amounts to 5.15 trillion tons of various waste in the waters and is increasing every year, by about 1.7 million tons. Of the total plastic in the oceans and seas, about 270,000 tons are blue on the surface, so, unfortunately, a lot of plastic is swallowed by fish, birds and turtles. Data indicate that marine animals swallow about 13 million tons annually, most of which die.

In addition to plastic and other waste, a lot of oil from tankers spills into the seas and oceans every year, which also kills fish and birds.

As for sea currents and bad weather, the Black Sea is considered one of the harshest, dangerous for navigation. And the North Sea is one of the unpleasant ones due to thick fog and storms, while the Pacific belongs to calmer oceans.

Plants that grow in seawater grow quickly and are very branched. One of these is Kelp, which they call "seaweed". Kelp grows the fastest of all plants, up to 50 cm per day and, can grow up to 50 m, is usually spread over the seabed in which case it is called a "sea forest". Kelp commonly grows in the waters around Chile, Australia and Southern California and is estimated to cover up to a quarter of the seabed in a given area.

The largest sources of food on planet Earth are the oceans, both for humans and animals. Man first began to engage in underwater research in 1943, when Jacques Cousteau tested his underwater lung device. The main sources of food from the sea and ocean are fish. China is the country that has the best fish processing industry and is the most processed in the world. Chinese fishing boats catch fish as far as Argentina. Canada's fishing areas for good catches are Newfoundland and Labrador, where warm and cold water currents mix, which favors fish life. Newfoundland and Labrador fishermen earn an average annual income of $69,824, plus cash compensation of about $7,340. Fish in the seas and oceans mainly live at depths of up to about 700 m, and can survive up to depths of 8,200 m. According to some studies, they say that fish from the Pacific are tastier than fish from other oceans.

The local population living in the regions of frozen oceans and seas mainly hunt seals for their own food. Occasionally they also hunt walruses and whales, and there are cases where they also hunt polar bears. Indigenous peoples living in the Arctic zone are predominantly Sammi peoples. They live in Finland, Sweden, Norway and the north-western part of Russia, and the Yupi, Aleut and Inuit peoples live in Canada, Alaska, and Greenland. Inuit in Canada live in the Northwest Territories (NWT) and Yukon. More than 40 indigenous groups of people live in the Arctic regions, mainly in the Arctic Ocean belt from Canada and Greenland to Russia. They certainly don't care about the melting of the ice, it threatens their existence. Indigenous people use whale oil for cooking, and in most cases they eat fresh meat, which they cut into large pieces, place them on a plate in the middle of the Iglo, and everyone cuts off as much as they can eat. They also keep the fire in the middle of the needle, and the smoke comes out at the top of the Iglo through the hole left for it. They mostly use kayaks for driving on the water, and more recently motorboats.

Tourism on the seas is the most lucrative and brings the best income. All the world's seas have sandy beaches, which are maintained by local towns and, where inland tourists come, spend their days swimming, swimming and diving, some use boats and/or boats for excursions, and some tourists enjoy watching whales and dolphins. Everyone finds their own kind of fun, and swimming in the seas is known to be healthy and very useful. And as all the seas and oceans are rich in fish, local fishermen sell their catch to restaurants, which prepare specialties characteristic of certain regions and nationalities, which all tourists enjoy and many cities and entire areas make sufficient income from tourism for their own survival. Therefore, tourism is an economic branch that occupies an imposing importance in many countries.

The Adriatic Sea is one of the most beautiful in the world, with a predominantly blue color, comfortable temperatures and beautiful coastal surroundings. The coast is very indented, with many islands and bays. There are extremely beautiful islands around the town of Hvar, and Mljet is one of the outstanding islands suitable for health tourism. On the island of Mljet, there are two lakes, a large one and a small one, connected to each other, where the water flows from one to the other every six hours (Tide and Ebb). There is also healing mud. The water is very clean and therefore transparent for 18 m. The only bad fact is that there are many snakes on the island. Dubrovnik is the pearl of the Adriatic Sea. The bad side of tourism is that many tourists leave waste behind in the seas and oceans, which unfortunately pollutes our only planet.

Polar bears live in cold regions, where there are a lot of icebergs floating on sea surfaces. And although both the North and South Poles of the Earth are almost identical in terms of ice and temperatures, polar bears live only at the North Pole, and penguins live at the South Pole. Therefore, polar bears are the property of Canada, Alaska, Greenland, Norway and Russia. Polar bears are classified as "marine mammals". They spend most of their time in cold water and can swim for hours. They mainly feed on seals. Indigenous peoples who hunt polar bears, in addition to meat for food, use their fur to make clothing, which is very warm and comfortable.

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