Arctic climate in the Arctic
The closer to the pole, the more obvious the meteorological and climatic characteristics of the polar region. There is only one day and one night a year. Even in midsummer, the sun just hangs on the distant southern horizon, with a bleak white light. The sun never rises above 23.5 degrees. It moves slowly around this endless white world. A few months later, the sun's trajectory gradually approached the horizon, so the evening season in the Arctic began.
The Arctic has endless ice and snow and a long winter. The North Pole, like the South Pole, has extreme days and nights, and the closer you get to the North Pole, the more obvious it is. Winter in the Arctic is long, cold and dark. Every year from165438+1October 23rd, the sun is completely invisible for nearly half a year. The temperature will drop to MINUS 50 degrees Celsius. At this time, all the waves and tides disappeared, because the coast was frozen and only the wind wrapped in snow swept around.
In April, the weather gradually warmed up, the ice and snow gradually melted, and large pieces of ice began to melt, break and collide with each other, making a loud noise. There is gurgling water in the stream; The sky becomes bright and the sun shines on the earth. In May and June, plants are covered with the green of life, and animals become active and busy reproducing. In this season, animals can get enough food and accumulate enough nutrition and fat to spend the long winter.
Autumn in the Arctic is very short, and the first snowstorm will come in early September. The arctic soon returned to the cold and dark winter. The annual precipitation in the Arctic is generally 100-250 mm, and it can reach 500 mm in Greenland. The main form of precipitation is summer rain. The Arctic is a world of ice and snow, but due to the movement of ocean currents, the sea ice on the surface of the Arctic Ocean is always drifting, cracking and melting, so it is impossible to accumulate thousands of meters of ice and snow like the Antarctic continent over millions of years. Therefore, the total amount of ice and snow in the Arctic is only close to110 in the Antarctic, and most of it is concentrated in the continental ice sheet of Greenland, while the permanent ice and snow in the Arctic Ocean, other islands and surrounding land only accounts for a small part.
Most of the surface of the Arctic Ocean is covered with sea ice all year round, and it is the only white ocean on the earth. The average thickness of sea ice in the Arctic Ocean is 3m, covering 73% of the total ocean area in winter, about 1 000- 1 0 1 000 million square kilometers, and 53% in summer, about 7.49-8 million square kilometers. The sea ice in the central Arctic Ocean has existed for 3 million years and belongs to permanent sea ice. Although most of the ocean surface of the Arctic Ocean is covered with ice and snow, the seawater under the ice, like the seawater of other oceans in the world, keeps flowing according to certain rules. If the tide is the pulse of the ocean, then the circulation of the ocean is the life of the ocean. Two currents play a major role in the surface circulation of the Arctic Ocean: one is the Isspitsbergen current, a tributary of the Atlantic Ocean, which enters the Arctic Ocean from the east of Greenland and moves counterclockwise along the edge of the shelf; The other is the trans-polar ocean current (cold water flow at the bottom of East Greenland), which flows in from Chukchi Sea, flows through the Arctic and then flows out from Greenland Sea to the Atlantic Ocean. They control the basic marine hydrological characteristics of the Arctic Ocean, such as water mass distribution and water exchange between the Arctic Ocean and the high seas.
In addition, the role of Norwegian warm current and North Point warm current can not be ignored. The latest statistical observation data show that the Atlantic Ocean current injects 72,000 cubic kilometers of seawater into the Arctic Ocean, the North Pacific Ocean current injects 30,000 cubic kilometers of seawater, and the rivers around the land inject 4,400 cubic kilometers of fresh water every year. In this way, the cold ocean bottom current of the Arctic Ocean must flow into the North Atlantic at an annual scale of 65,438+005,000 cubic kilometers through the Fromm Strait with a depth of 2,700 meters and a width of 450 kilometers. These arctic ocean currents have a great influence on the climate characteristics and ecological environment of the arctic and its surrounding areas. The coastline of the Arctic Ocean is tortuous and varied, including steep rocky coast and fjord coast, abrasive coast, low-level coast, delta and lagoon coast and composite coast. There are many shallow marginal seas and bays in the vast continental shelf area. There are many islands in the Arctic Ocean, with a total area of about 3.8 million square kilometers, which basically belong to mainland islands in the shelf area. The largest island is Greenland, with an area of 2 1.8 thousand square kilometers, which is larger than the total area of western and central Europe, so some people call it Greenland subcontinent. There are about 60,000 residents in Greenland, 90% of whom are Greenlanders and the rest are mainly Danes. The largest archipelago is Canada's Arctic archipelago, which consists of hundreds of islands with a total area of about 6,543,800 square kilometers. Ellesmere island, the largest island, lies in the northeast. The town of Arel in the north of the island has exceeded 82 N, so it is the starting point of many Arctic explorations.
Greenland is not only the largest island on earth, but also an island with most of its area (84%) covered by ice and snow. Greenland's continental glaciers (or ice sheets) cover an area of 6.5438+0.8 million square kilometers, and their average ice thickness reaches 2300 meters, which is close to the average thickness of Antarctic continental ice sheets. The total amount of ice and snow in Greenland is 3 million cubic kilometers, accounting for 5.4% of the total fresh water in the world. If all the ice and snow in Greenland melt, the global sea level will rise by 7.5 meters. If all the ice and snow in Antarctica melt, the global sea level will rise by 66 meters.
In Greenland's vast white cold world, snowfall can't melt, so it accumulates year after year. The fresh snow is soft, weighing 100 kg per cubic meter. In fact, there are not many opportunities for new snow to fall directly on the ice. Due to the strong wind all the year round, hexagonal snowflakes fly and collide in the wind, gradually grinding away the edges and corners, turning into snow like cement powder, and falling on the ice with the wind, forming a snowstorm. The density of snow and wind is greater than that of fresh snow, weighing 400 kilograms per cubic meter. Snowfall is covered by layers. With the increase of depth and pressure, new snow gradually becomes granular snow composed of fine snow particles. At the depth of 70- 100 m, the snow crystals merge with each other, and the air between the snow crystals is compressed into independent small bubbles, which become white bubble ice, or new ice, and the density of new ice reaches 820 kg per cubic meter. When the burial depth exceeds 1200m, the huge pressure makes the bubbles in the new ice disappear, gas molecules enter the crystal lattice of ice crystals, and tiny ice crystals quickly fuse and expand into huge single crystals (the maximum diameter can reach 10c m), and finally blue hard old ice is formed, also known as Lan Bing. Lan Bing, covered with white snow, granular snow and new ice, constitutes the main body of the continental ice sheet. Moreover, the deeper the ice, the longer it takes to form. It is estimated that the age of the deepest ice layer in Greenland ice sheet can reach hundreds of thousands of years or even 1 10,000 years.
Like the Antarctic, the vast ice fields on the land and islands in the Arctic region look distant and quiet, and seem to represent some kind of eternal stillness. But in fact, due to the weight of ice and snow, the land ice sheet keeps moving to the coast, and it is deep, slow and unstoppable. The average annual moving speed of the inland ice sheet in Greenland is several meters, while the coastal area can reach 100-200 meters. As for those huge glaciers, they move much faster. The so-called glacier is actually a river of ice and snow. Billions to tens of billions of tons of ice and snow are quietly pushed, rubbed and moved in valleys or lowlands where glaciers flow. They slowly but indomitable to the sea, and finally earth-shattering collapse into the sea. The ice sheet moved and finally collapsed, forming huge icebergs in the sea. Only in this way, Greenland's land ice sheet loses 150 cubic kilometers of ice every year. On the other hand, the total annual snowfall and ice accumulation in Greenland is about 170 square kilometers. But as in Antarctica, so far, scientists are not sure whether the continental ice sheet in Greenland is slowly growing or dying.