The deep water in the North Atlantic enters the Caribbean Sea from below the windward channel, with an oxygen content of 6 ml/L and a salinity of 35‰. The depth of Venezuela basin1800 ~ 3,000 meters (5,900 ~ 9,800 feet) forms a hyperoxic water layer. Due to the barrier of the submarine ridge, the bottom water from the South Pole cannot enter. The seabed temperature in the Caribbean Sea is close to 4℃(39℉), while that in the Atlantic Ocean is less than 2℃(36℉). Surface currents enter the Caribbean Sea mainly through waterways and straits between the South Antilles, and then cross the narrow Yucatan Strait into the Gulf of Mexico under the impetus of trade winds. These wind-driven surface waters gather in the Yucatan Basin and the Gulf of Mexico, resulting in the sea level being higher than that of the Atlantic Ocean, forming a hydrostatic head, which is generally considered to be the main power source of the Gulf Stream.
The winding coastline of Central and South America divides this sea area into several main waters: Honduran Bay along Guatemala and Honduras, Mosquito Bay along Panama, Panama Canal near Cologne, Darien Bay on the border between Panama and Colombia, Venezuela Bay outside the mouth of Lake Maracaibo in northern Venezuela and Parria Bay between Venezuela and Trinidad.
The hydrological characteristics of the Caribbean Sea are very similar. Take the monthly average sea surface temperature as an example, and the annual change does not exceed 3℃(25-28℃). In the past 50 years, the Caribbean Sea has gone through three different stages, and it continued to cool before 1974. The coldest time occurs in 1974 ~ 1976, and the annual temperature keeps rising by 0.6℃. The change of temperature is related to El Nino-Southern Oscillation phenomenon and anti-El Nino phenomenon. The salinity of the Caribbean Sea is 3.6%, the density is1.0235-1.0240103kg/m3, and the surface color of seawater varies from blue-green to green.
The climate of the Caribbean Sea is influenced by ocean currents, such as the Gulf Warm Current and the Peruvian Cold Current. Because it is located in the tropics, the seawater temperature is maintained at a relatively warm temperature, and the lowest temperature in each season is between 2 1-29℃.
The Caribbean Sea is a region where tropical cyclones often occur in the Western Hemisphere. A series of low-pressure systems emerged from the western waters of Africa and crossed the Atlantic Ocean to the Caribbean Sea. Most low-pressure systems will not develop into tropical cyclones, and only a few will, that is, tropical cyclones in the North Atlantic, mostly in the low-pressure area of the Eastern Caribbean. Tropical cyclones appear in June-165438+ 10 every year, mainly in August and September. On average, there are nine tropical cyclones every year, five of which reach hurricane level. According to the National Hurricane Center, there were 385 hurricanes between 1494 and 1900.
Hurricanes are so destructive that they are a potential threat to Caribbean islands every year. Powerful waves will break coral reefs. If a hurricane carries sand or mud, it will suffocate corals. Finally, coral reefs will collapse.
The Caribbean Sea is home to 9% of the world's coral reefs, covering an area of about 20,000 square miles (52,000 "? ), mainly distributed in the Caribbean Islands and the Gulf of Central America. The largest of these is Belize Barrier Reef, with an area of 96,300 hectares, which is listed as a World Heritage Site with 1996. It is also a part of the Great Barrier Reef System in Central America (MBRS). The Great Barrier Reef system in Central America is about 1000 km long, and it is the second longest coral reef in the world, distributed along the coasts of Mexico, Belize, Guatemala and Honduras near the Caribbean.
In recent years, the unusually warm Caribbean waters have increasingly threatened coral reefs. Coral reef is one of the most diverse marine environments in the world, but its ecosystem is very fragile. When the tropical sea water is unusually warm for a long time, the zooxanthellae living with corals will die, which provides food for corals and is also the reason why coral reefs are colored. The result of the death and disappearance of this small plant is coral bleaching, which will cause the destruction of large coral reefs. More than 42% of coral reefs have been completely bleached, and 95% of coral reefs have been partially bleached [2]. The crust in the sea area is very unstable, surrounded by deep-sea trenches and volcanic earthquake zones. The broad Jamaica Ridge divides the seabed into two parts. There are Yucatan Basin and Cayman Trench in the west, separated by submarine mountains extending westward from Maestra Mountain on Cuba Island. The peaks exposed from the undersea mountains form little cayman Island and Great Britain Island. The depth of Yucatan Basin is about 4000m, the average depth of Cayman Trench is 5000m ~ 6000m, and the deepest point is 7680m. The east is divided into Columbia Basin and Venezuela Basin by Bita Ridge which runs northeast and southwest. The average depth of the Columbia Basin is about 3,000 meters, and the deepest point is 4,535 meters. The average depth of Venezuela basin is about 4500 meters, and the deepest part is 5630 meters. Jamaica Ridge extends from Haiti and Jamaica to the southwest to the east of Honduras and Nicaragua in Central America, with a depth of about 500 meters, of which more than half is less than 200 meters. The seabed of the Caribbean Sea is Cenozoic sediments. Compared with deep-sea basins and trenches, most of them are red clay, and the platform is globigerina ooze, while the underwater mountains and continental slopes are pteropods ooze.
The Caribbean basin is separated by several ridges, which makes the basin and trench crisscross. The northernmost Yucatan Basin is about 5000 meters deep, bounded by the 220-kilometer-wide Yucatan Strait in the north and separated from the Cayman Trench by the Cayman Ridge in the south. The ridge extends from Cuba to the coast of Central America, and the Cayman Islands is exposed to the sea in the east. The Cayman Trench is quite narrow, and the maximum depth of the Caribbean Sea (7 100 m) is here. Further south, there is a wide wedge-shaped Nicaraguan seamount that separates the trench from the Columbia Basin, and Jamaica Island is on this seamount. Colombia basin is 3666 meters deep, connected with Venezuela basin, and further east is the North Venezuela Trench. However, from the island of Hispaniola to the west, there is a Bita Ridge that separates the Colombian basin from the Venezuelan basin. Venezuela basin is 5058 meters deep, adjacent to the narrow and curved Abbes seamount. Most of the sea areas are located between north latitude 10 ~ 20, and belong to tropical climate. The northeast wind prevails all the year round, with high temperature and humidity, and the atmosphere is in an unstable state. Tropical storms occur in north-central China in June 6- 10/October every year165438+September with the highest frequency, and the wind speed can exceed 33.5m/s, with an average of 8 times a year, which has adverse effects on shipping.
The sea current in the sea area is a powerful warm current formed by the confluence of the North Equatorial Current and the South Equatorial Current of the Atlantic Ocean after passing through the Lesser Antilles. It flows through the Caribbean Sea from east to west at a speed of 28 ~ 83 cm/s, and finally flows into the Gulf of Mexico from the Yucatan Strait. Due to the low latitude of the sea area and the influence of warm current, the surface water temperature of the sea water is high, often reaching 27 ~ 28℃, with a small change in winter and summer, ranging from 25.6 ~ 28.9℃. High temperature is beneficial to the reproduction of corals in shoals and volcanic island bases, so there are many coral reefs and coral islands in this sea area. The Caribbean Sea, especially the northwest coast of the South American continent, is affected by offshore winds to form an upwelling, bringing nutrients from seawater to the surface. It is suitable for plankton and fish breeding and has become an important fishing ground in Latin America, rich in tuna, turtles, sardines and lobsters. The southern part of the sea area is an oil-producing area. Caribbean Sea is a necessary sea area for transportation and trade routes between China and the United States, South America and North America. Since the opening of 1920, the Panama Canal has become an important sea passage connecting the Atlantic Ocean and the Pacific Ocean, which has greatly promoted the economic development of more than 30 countries and regions along the Caribbean coast. The main ports are Caracas (Venezuela), Cologne (Panama), Kingston (Jamaica) and Williamstad (Netherlands Antilles). Most rivers in Central America flow into the Caribbean Sea, but most rivers in South America meet at the Orinoco River and flow into the Atlantic Ocean just south of Port of Spain.