Albedo is the fraction of sunlight that is diffusely reflected by a body. It is measured on a scale from 0 to 1. Surface albedo is defined as the ratio of radiosity Je to the irradiance Ee received by a surface. The proportion reflected is not only determined by properties of the surface itself, but also by the spectral and angular distribution of solar radiation reaching the Earth's surface. These factors vary with atmospheric composition, geographic location, and time.
The cryosphere is an all-encompassing term for the portions of Earth's surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps, ice sheets, and frozen ground. Thus, there is a wide overlap with the hydrosphere. The cryosphere is an integral part of the global climate system. It also has important feedbacks on the climate system. These feedbacks come from the cryosphere's influence on surface energy and moisture fluxes, clouds, the water cycle, atmospheric and oceanic circulation.
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.
The National Snow and Ice Data Center (NSIDC) is a United States information and referral center in support of polar and cryospheric research. NSIDC archives and distributes digital and analog snow and ice data and also maintains information about snow cover, avalanches, glaciers, ice sheets, freshwater ice, sea ice, ground ice, permafrost, atmospheric ice, paleoglaciology, and ice cores.
The Byrd Polar and Climate Research Center (BPCRC) is a polar, alpine, and climate research center at Ohio State University founded in 1960.
A polar ice cap or polar cap is a high-latitude region of a planet, dwarf planet, or natural satellite that is covered in ice.
The Greenland Sea is a body of water that borders Greenland to the west, the Svalbard archipelago to the east, Fram Strait and the Arctic Ocean to the north, and the Norwegian Sea and Iceland to the south. The Greenland Sea is often defined as part of the Arctic Ocean, sometimes as part of the Atlantic Ocean. However, definitions of the Arctic Ocean and its seas tend to be imprecise or arbitrary. In general usage the term "Arctic Ocean" would exclude the Greenland Sea. In oceanographic studies the Greenland Sea is considered part of the Nordic Seas, along with the Norwegian Sea. The Nordic Seas are the main connection between the Arctic and Atlantic oceans and, as such, could be of great significance in a possible shutdown of thermohaline circulation. In oceanography the Arctic Ocean and Nordic Seas are often referred to collectively as the "Arctic Mediterranean Sea", a marginal sea of the Atlantic.
Polar amplification is the phenomenon that any change in the net radiation balance tends to produce a larger change in temperature near the poles than in the planetary average. This is commonly referred to as the ratio of polar warming to tropical warming. On a planet with an atmosphere that can restrict emission of longwave radiation to space, surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict. Where the atmosphere or an extensive ocean is able to transport heat polewards, the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict. The poles will experience the most cooling when the global-mean temperature is lower relative to a reference climate; alternatively, the poles will experience the greatest warming when the global-mean temperature is higher.
The climate of the Arctic is characterized by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter. Some parts of the Arctic are covered by ice year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface.
The Global Energy and Water Exchanges Project is an international research project and a core project of the World Climate Research Programme (WCRP).
The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. 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.
Polar seas is a collective term for the Arctic Ocean and the southern part of the Southern Ocean. In the coldest years, sea ice can cover around 13 percent of the Earth's total surface at its maximum, but out of phase in the two hemispheres. The polar seas contain a huge biome with many organisms.
Ice–albedo feedback is a climate change feedback, where a change in the area of ice caps, glaciers, and sea ice alters the albedo and surface temperature of a planet. Because ice is very reflective, it reflects far more solar energy back to space than open water or any other land cover. It occurs on Earth, and can also occur on exoplanets.
Measurement of sea ice is important for safety of navigation and for monitoring the environment, particularly the climate. Sea ice extent interacts with large climate patterns such as the North Atlantic oscillation and Atlantic Multidecadal Oscillation, to name just two, and influences climate in the rest of the globe.
Sea ice concentration is a useful variable for climate scientists and nautical navigators. It is defined as the area of sea ice relative to the total at a given point in the ocean. This article will deal primarily with its determination from remote sensing measurements.
Sea ice thickness spatial extent, and open water within sea ice packs can vary rapidly in response to weather and climate. Sea ice concentration are measured by satellites, with the Special Sensor Microwave Imager / Sounder (SSMIS), and the European Space Agency's Cryosat-2 satellite to map the thickness and shape of the Earth's polar ice cover. The sea ice volume is calculated with the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS), which blends satellite-observed data, such as sea ice concentrations into model calculations to estimate sea ice thickness and volume. Sea ice thickness determines a number of important fluxes such as heat flux between the air and ocean surface—see below—as well as salt and fresh water fluxes between the ocean since saline water ejects much of its salt content when frozen—see sea ice growth processes. It is also important for navigators on icebreakers since there is an upper limit to the thickness of ice any ship can sail through.
Sea ice in the Arctic region has declined in recent decades in area and volume due to climate change. It has been melting more in summer than it refreezes in winter. Global warming, caused by greenhouse gas forcing is responsible for the decline in Arctic sea ice. The decline of sea ice in the Arctic has been accelerating during the early twenty‐first century, with a decline rate of 4.7% per decade. Summertime sea ice will likely cease to exist sometime during the 21st century.
Antarctic sea ice is the sea ice of the Southern Ocean. It extends from the far north in the winter and retreats to almost the coastline every summer. Sea ice is frozen seawater that is usually less than a few meters thick. This is the opposite of ice shelves, which are formed by glaciers; they float in the sea, and are up to a kilometre thick. There are two subdivisions of sea ice: fast ice, which are attached to land; and ice floes, which are not.
Professor Julienne Christine Stroeve is a polar climate scientist known for her research on remote sensing of ice and snow. She is Professor of Polar Observation & Modelling at the Centre for Polar Observation and Modelling, University College London, Senior Canada-150 Research Chair in Climate Forcing of Sea Ice at the University of Manitoba, and a senior research scientist at the National Snow and Ice Data Center within the Cooperative Institute for Research in Environmental Sciences (CIRES). She is also a member of the American Geophysical Union and an ISI highly cited researcher.
