This post is second in the three part Polar Ice series. The first part described the continent of Antarctica. This part describes the Arctic region at the north pole. Part three will describe the impacts that climate change seems to have on each region.
What region is defined as the Arctic? That depends on who you ask. As noted in this map, there are three generally accepted definitions. The most common definition from scientists is the region north of the Arctic Circle above 66.5˚ latitude. North of that latitude, the sun does not set on the summer solstice or rise on the winter solstice. A second common definition is the area where the average temperature for July is less than 10˚C or 50˚F. The third is the area north of the tree line. All three are indicated with arrows on the map.
Starting at the North Pole, follow the vertical line on the map toward the bottom. It is the 0˚ Prime Meridian and passes through Greenwich, England. Go to the left on 90˚W to pass through Canada, St. Louis, Central America, and the Galapagos Islands off the west coast of South America. The line toward the top of the map goes through the central Pacific. Go to the right on 90˚E to pass through Russia, eastern India, and the Indian Ocean.
The north coast of Russia, islands to the north of Canada, northern Scandinavia, and Iceland are designated as an arctic maritime climate. They have very cold and stormy weather in the winter with snowfall totals from 60-120 cm (2-4 ft). Regions closer to the pole and the interior of Greenland have yearlong ice cover. Unlike the Antarctic which has most of its ice grounded on solid land, the Arctic has most of its ice floating on the sea. This map is a generalized view and does not represent any particular date of the year. Click to embiggen.
The extent of sea ice in the Arctic as of December 17, 2014 is shown in the map below. Notice the map is rotated about 90˚ counterclockwise from the one above. The orange line is the median extent of ice for this date averaged from 1981-2010. Sea ice thickness in the 1980s was averaging about 2.3 meters (7.5 ft). It has decreased steadily since then to a current average value of about 1.5 meters (5 ft). More about the changes in the polar ice amounts in part three of this series.
The maximum area covered by the sea ice is in late winter. At the end of the summer months, the sea ice has melted to cover a much smaller area. This image shows the minimum extent this year in September 2014. Notice the median extent line for this date. Because of the extent of the sea ice, passage through from the Atlantic to the Pacific has been very difficult and treacherous, if not impossible. It was first navigated by Roald Amundsen in 1903–1906. Because of climate change, this Northwest Passage is becoming a greater reality.
The sea floor of the Arctic Ocean at its deepest is 5,502 meters (18,050 ft). The average depth is 987 meters (3,240 ft). A map of the floor shows the shallower continental shelf in light blue and the much deeper rugged regions in dark blue. The deep rift valley running horizontally and off the right edge of the image is the northernmost extent of the Mid-Atlantic Ridge. It is the result of the separation of tectonic plates.
Territorial claims in the Arctic are complicated. The Arctic includes land, territorial waters, and international waters. Land and territorial waters belong to five countries Russia, the United States, Canada, Norway, and Denmark. International law regulates these lands and waters. International water at the North Pole and surrounding it, is not owned by any country. The five countries have rights limited to an exclusive economic zone (EEZ) of 200 nautical miles (370 km) adjacent to their coasts. The sea floor beyond the exclusive economic zones are understood to be the “heritage of all mankind” and administered by the UN International Seabed Authority.
Certain parts of the Arctic sea region are in dispute for various reasons. All five countries regard parts of the Arctic seas as “national waters”, that is waters out to 12 nautical miles (22 km) from their coasts. These disputes affect what passages constitute “international seaways” and the future rights along them as in a future Northwest Passage.
Explore the Arctic Sea Ice News and Analysis web site for more information.
NOAA Arctic Theme Page