Arctic sea ice declineSea ice in the Arctic 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 (it has declined over 50% since the first satellite records). It is also thought that summertime sea ice will cease to exist sometime during the 21st century.
Sea iceSea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). 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.
ArcticThe Arctic (ˈɑrtɪk or ˈɑrktɪk) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), northern Finland (Northern Ostrobothnia, Kainuu and Lappi), Iceland, northern Norway (Nordland, Troms, Finnmark, Svalbard and Jan Mayen), Russia (Murmansk, Siberia, Nenets Okrug, Novaya Zemlya), northernmost Sweden (Västerbotten, Norrbotten and Lappland) and the United States (Alaska).
Arctic ice packThe Arctic ice pack is the sea ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a regular seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall and winter. Summer ice cover in the Arctic is about 50% of winter cover. Some of the ice survives from one year to the next. Currently, 28% of Arctic basin sea ice is multi-year ice, thicker than seasonal ice: up to thick over large areas, with ridges up to thick.
Arctic sea ice ecology and historyThe Arctic sea ice covers less area in the summer than in the winter. The multi-year (i.e. perennial) sea ice covers nearly all of the central deep basins. The Arctic sea ice and its related biota are unique, and the year-round persistence of the ice has allowed the development of ice endemic species, meaning species not found anywhere else. There are differing scientific opinions about how long perennial sea ice has existed in the Arctic. Estimates range from 700,000 to 4 million years. The specialized, sympagic (i.
Interquartile rangeIn descriptive statistics, the interquartile range (IQR) is a measure of statistical dispersion, which is the spread of the data. The IQR may also be called the midspread, middle 50%, fourth spread, or H‐spread. It is defined as the difference between the 75th and 25th percentiles of the data. To calculate the IQR, the data set is divided into quartiles, or four rank-ordered even parts via linear interpolation. These quartiles are denoted by Q1 (also called the lower quartile), Q2 (the median), and Q3 (also called the upper quartile).
Interquartile meanThe interquartile mean (IQM) (or midmean) is a statistical measure of central tendency based on the truncated mean of the interquartile range. The IQM is very similar to the scoring method used in sports that are evaluated by a panel of judges: discard the lowest and the highest scores; calculate the mean value of the remaining scores. In calculation of the IQM, only the data between the first and third quartiles is used, and the lowest 25% and the highest 25% of the data are discarded. assuming the values have been ordered.
Arctic oscillationThe Arctic oscillation (AO) or Northern Annular Mode/Northern Hemisphere Annular Mode (NAM) is a weather phenomenon at the Arctic pole north of 20 degrees latitude. It is an important mode of climate variability for the Northern Hemisphere. The southern hemisphere analogue is called the Antarctic oscillation or Southern Annular Mode (SAM). The index varies over time with no particular periodicity, and is characterized by non-seasonal sea-level pressure anomalies of one sign in the Arctic, balanced by anomalies of opposite sign centered at about 37–45° N.
Atmospheric electricityAtmospheric electricity describes the electrical charges in the Earth's atmosphere (or that of another planet). The movement of charge between the Earth's surface, the atmosphere, and the ionosphere is known as the global atmospheric electrical circuit. Atmospheric electricity is an interdisciplinary topic with a long history, involving concepts from electrostatics, atmospheric physics, meteorology and Earth science. Thunderstorms act as a giant battery in the atmosphere, charging up the electrosphere to about 400,000 volts with respect to the surface.
Atmospheric modelIn atmospheric science, an atmospheric model is a mathematical model constructed around the full set of primitive, dynamical equations which govern atmospheric motions. It can supplement these equations with parameterizations for turbulent diffusion, radiation, moist processes (clouds and precipitation), heat exchange, soil, vegetation, surface water, the kinematic effects of terrain, and convection. Most atmospheric models are numerical, i.e. they discretize equations of motion.
