Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface. Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world's sea ice is enclosed within the polar ice packs in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the Arctic ecology, including the ocean's ecosystems. Due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Depending on location, sea ice expanses may also incorporate icebergs.
Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object. Unlike fast ice, which is "fastened" to a fixed object, drift ice is carried along by winds and sea currents, hence its name. When drift ice is driven together into a large single mass, it is called pack ice. Wind and currents can pile up that ice to form ridges up to dozens of metres in thickness. These represent a challenge for icebreakers and offshore structures operating in cold oceans and seas.
Seabed gouging by ice is a process that occurs when floating ice features drift into shallower areas and their keel comes into contact with the seabed. As they keep drifting, they produce long, narrow furrows most often called gouges, or scours. This phenomenon is common in offshore environments where ice is known to exist. Although it also occurs in rivers and lakes, it appears to be better documented from oceans and sea expanses.
An ice shove is a surge of ice from an ocean or large lake onto the shore. Ice shoves are caused by ocean currents, strong winds, or temperature differences pushing ice onto the shore, creating piles up to 12 metres high. Ice shoves can be caused by temperature fluctuations, wind action, or changing water levels and can cause devastation to coastal Arctic communities. Cyclical climate change will also play a role in the formation and frequency of ice shove events; a rise in global temperatures leads to more open water to facilitate ice movement. Low pressure systems will destabilize ice sheets and send them shoreward. Also referred to as "landfast ice", it is an essential component to the coastal sea ice system, including the sediment dynamics. Arctic peoples utilize these ice shoves to travel and hunt. Ringed seals, an important prey for polar bears, are specifically adapted to maintain breathing holes in ice shoves, which lack the same openings usually used by marine mammals in drifting ice packs. The mere fact that the Ringed seal is uniquely adapted to utilizing ice shoves for breathing holes, and that polar bears have adapted to this behaviour for hunting, as well as the fact that the Inupiat have a distinct term for the phenomena, indicates that ice shoves are a regular and continuing phenomena in the Arctic.
Anchor ice is defined by the World Meteorological Organization as "submerged ice attached or anchored to the bottom, irrespective of the nature of its formation". It may also be called bottom-fast ice. Anchor ice is most commonly observed in fast-flowing rivers during periods of extreme cold, at the mouths of rivers flowing into very cold seawater, in the shallow sub or intertidal during or after storms when the air temperature is below the freezing point of the water, and the subtidal in the Antarctic along ice shelves or near floating glacier tongues, and in shallow lakes.
The following outline is provided as an overview of and introduction to Oceanography.
A lead is a large fracture within an expanse of sea ice, defining a linear area of open water that can be used for navigation purposes. Leads vary in width from meters to hundreds of meters. As is the case for polynyas, leads allow the direct interaction between the atmosphere and the ocean, and are important for Arctic sea ice ecology. Additionally it has been lately found that ice leads contribute significantly to the amount of mercury deposited onto surface and leaked into the ocean. If the air is cold enough, the water within a lead quickly refreezes, such that in many cases, leads are partly or entirely covered by a thin layer of new ice.
The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately 14,060,000 km2 (5,430,000 sq mi) and is known as one of the coldest of oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea. It has also been described as an estuary of the Atlantic Ocean. It is also seen as the northernmost part of the all-encompassing World Ocean.
A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.
A stamukha is a grounded accumulation of sea ice rubble that typically develops along the boundary between fast ice and the drifting pack ice, or becomes incorporated into the fast ice. It is a pressure ridge. Wind, currents and tides contribute to this phenomenon. Stamukhi tend to occur in belts that are parallel to the shoreline, along coastal shoals, at water depths of about 20 m (65 ft), but that can reach 50 m (160 ft). They can build up to heights 10 metres (33 ft) or more above the waterline. Although they remain pinned to the seabed, these features can be subject to small displacements, either due to thermal expansion or to the pressure exerted by the drifting pack ice onto the fast ice. Because stamukhi tend to be deeply grounded, they may occur as isolated ice features in the open sea during the summer season, after the surrounding ice has melted away.
The Port Elizabeth Corals Marine Protected Area is an offshore conservation region south of Port Elizabeth in the exclusive economic zone of South Africa
The Agulhas Front Marine Protected Area is an offshore conservation region in the exclusive economic zone of South Africa.
The Orange Shelf Edge Marine Protected Area is an offshore conservation region near the edge of the continental shelf in the exclusive economic zone of South Africa off the north coast of the Northern Cape province.
The Benguela Muds Marine Protected Area is an offshore conservation region on the continental slope of the west coast in the exclusive economic zone of South Africa.
The Childs Bank Marine Protected Area is an offshore conservation region in the exclusive economic zone of South Africa
The Browns Bank Complex Marine Protected Area is an offshore conservation region in the exclusive economic zone of South Africa
The Benguela Bank Marine Protected Area is an offshore conservation region in the exclusive economic zone of South Africa
The Jutten Island Marine Protected Area is an inshore conservation region in the territorial waters of South Africa in Saldanha Bay, in the Western Cape.
The Malgas Island Marine Protected Area is an inshore conservation region encompassing Malgas Island, in the territorial waters of South Africa at the entrance to Saldanha Bay on the west coast of the Western Cape province.
The Stilbaai Marine Protected Area is an inshore conservation region in the territorial waters near Stilbaai on the south coast of the Western Cape province of South Africa.
