Arctic Marine Geography

(from AMSA Report 2009)

Our Earth has two polar regions, each with a large marine environment, that are vital to the well-being of the planet: Antarctica and the Arctic. Unlike Antarctica, though, which is a continent surrounded by an ocean, the Arctic is an ocean surrounded by continents. The Arctic Ocean, at 14.056 million km2, is the smallest of the world’s five oceans (Table 2.1). It is mostly an enclosed sea that has limited exchange of deep water with other oceans.

Table 2.1 Arctic Ocean compared to other oceans

Source: AMSA

Compared to the Mediterranean Sea, the Arctic has a much greater exchange of water, and it is more than 5.6 times larger. Consequently, the International Hydrographic Organization along with the International Maritime Organization recognizes the Arctic Ocean as one of the five major components of the world ocean that covers almost 71 percent of the Earth’s surface.

More importantly, the Arctic Ocean is the least sampled of the world’s oceans and many areas remain where few, if any, soundings have been recorded. The implications of this lack of basic marine information are profound for charting hydrography and for basic Arctic navigation. The Arctic is bordered by numerous coastal seas, all of which are seasonally covered with sea ice. Working from Greenland eastwards, the waters adjacent to the Arctic basin itself are Greenland Sea, Norwegian Sea, Barents Sea, White Sea, Kara Sea, Laptev Sea, East Siberian Sea and Chukchi Sea - all fronting on the Eurasia continental land mass. The Bering Sea, the Beaufort Sea, the waters within the Canadian Archipelago including those of the Northwest Passage, Hudson Bay and Hudson Strait, Lincoln Sea, Baffin Bay, Davis Strait and Labrador Sea are all bordering on the North American continent.

Most Arctic marine activity, such as fishing, offshore hydrocarbon development and ship transits, takes place in these coastal seas. Bathymetrically, the Arctic marine area is relatively shallow (Map 2.1) with broad continental shelves. The shelf extends 100 to 200 kilometers from the United States and Canada, and more than 1,000 kilometers in places extending north from the Russian Federation. Depths over the shelves average between 100 and 200 meters but are variable, especially as the continental landmasses and islands are approached. At the continental slopes, the break between the shelf and the deep ocean basin, depths are between 300 and 500 meters.

Map 2.1 The Arctic Marine area

Source: AMSA

There are two major deep basins - the Eurasia and Amerasia – separated by the Lomonosov Ridge stretching from the East Siberian Sea to the Lincoln Sea. The ridge is an underwater mountain chain rising, on average, 3,000 meters above the abyssal plain. On the Eurasian side of the Lomonosov Ridge, the basin is again split into two by the Nansen-Gakkel Arctic Mid-Ocean Ridge. Between the Lomonosov and Nansen-Gakkel Ridges lies the Pole Abyssal Plain in which is found the geographical North Pole at 90 degrees north. The depth of water at the pole is well over 4,000 meters.

On the Amerasia side of the Lomonosov Ridge there are also two basins - the Makarov and Canada - separated by the Alpha and Mendeleev ridges. Of the two basins, the Canada Basin is the largest. Major islands and island archipelagos fringe the Arctic marine area and they help frame the marine routes, legal regimes and navigational options in the Arctic Ocean. The largest island is Greenland at 2,166,086 km². The largest archipelago is the Canadian Archipelago with more than 36,000 islands including Baffin (507,451 km²), Victoria (217,291 km²) and Ellesmere (196,236 km²), which are among the world’s largest 10 islands. The next largest single island fringing on the Arctic marine area is Iceland (103,000 km²).

On the west, the Arctic Ocean is bounded by Svalbard (Norway) of which Spitsbergen is the largest island; Franz Josef Land (Russian Federation) with 191 islands; Novaya Zemlya (Russian Federation) with two major islands (Severny at 47,079 km² and Yuzhny at 33,246 km²); Severnaya Zemlya (Russian Federation) consisting of four major islands and 70 smaller ones; and New Siberian Islands (Russian Federation) with the Anzhu Islands and the Lyakhovskiye Islands. Between the New Siberian Islands group and the Bering Strait lies Wrangel Island (7,300 km²). Given these fringing islands, the distance from the nearest land to the North Pole is as little as 707 kilometers (382 nautical miles) (Table 2.2), but this distance is different for each Arctic nation.

Of interest to the marine world is the approximate 2,100 nautical mile (1134 kilometer) distance (direct) from the Bering Strait to the North Pole to Fram Strait (between Greenland and Svalbard). All other distances along the coastal routes within the Arctic basin are longer. Although technically not on the edge of the Arctic Ocean, the Aleutian Islands in the Pacific Ocean provide the southern limit of the Bering Sea, which links through the Bering Strait into the Chukchi Sea and the Arctic Ocean.

A global maritime trade route - the North Pacific’s Great Circle Route - intersects with the Aleutian Islands and thousands of large ships pass north and south of these islands on voyages between the west coast of North America and Asian ports each year. The water connections linking the Arctic and the Pacific and Atlantic oceans are limited. The narrow and shallow Bering Strait (85 kilometer width; 30-50 meter depth) is the only link between the Arctic and the Pacific.

There are more and wider passages between the Arctic and the Atlantic. Davis Strait between Canada and Greenland links Baffin Bay with the Labrador Sea and the North Atlantic. At its narrowest point Davis Strait is about 300 kilometers wide; at its widest it is over 950 kilometers. Between Greenland and Iceland lies Denmark Strait (290 kilometers wide at its narrowest). The widest passage is the Norwegian Sea at about 1,100 kilometers separating Iceland from Norway.

These water passages between the Arctic Ocean and its northern coastal seas allow exchanges of water vital to the Arctic’s climate and marine ecosystems. By far the greatest exchange of water takes place between the Arctic and the Atlantic. Relatively warm dense salty water, as part of the North Atlantic Current originating in the Gulf of Mexico and Caribbean Sea, enters the Norwegian Sea continuing into the Barents Sea. This warmer water means that the Southern Barents Sea is not generally ice-covered, a significant factor in the regulation and control of marine traffic in this northwest corner of Europe that is by latitude located in the Arctic region. After much mixing and cyclonic (counter-clockwise) circulation, cold, less salty water exits between Svalbard and Greenland and Greenland and Iceland. This exiting water consists not only of the modified North Atlantic waters but, more importantly, continental river water from Eurasia, especially from the Ob’, Yenisei and Lena rivers of the Russian Federation; freshwater from the Mackenzie River in Canada; and Pacific water which entered through the Bering Strait.

The driving engine conveying the Pacific water and the river waters eastward is the Beaufort Gyre north of Alaska and western Canada. This gyre - a clockwise circulation of relatively fresh, less dense water - is driven by prevailing winds. When winds shift and the current lessens some water escapes and is caught up in the Trans Polar current, eventually linking with the outflow water into the Atlantic Ocean. Cold waters also exit from the Arctic to the Atlantic through Baffin Bay, Davis Strait and Hudson Strait.

An important geographical limit and a defining line is the Arctic Circle (66 degrees 33 minutes north). At this latitude places receive continuous light for 24 hours per day once a year and as one moves poleward the number of days of continuous light increases until at the North Pole continuous light is experienced for six months between the Vernal (March 21) and Autumnal equinoxes (September 21). Conversely, continuous dark is experienced at the pole for the other six months and decreasingly in time as one moves south. Significant for marine operations is that much of the central Arctic Ocean is shrouded in winter darkness with very low temperatures for half the year. This seasonal or diurnal cycle in the polar environment, while highly influential in the rhythmic behavior and adaptation of Arctic communities and animal populations, has broad implications for maritime use throughout the Arctic Ocean and its coastal seas.

Arctic Council, 2009, Arctic Marine Shipping Assessment (AMSA), Arctic Council.©