Dead SeaThe Dead Sea (اَلْبَحْرُ الْمَيْتُ, Āl-Baḥrū l-Maytū; יַם הַמֶּלַח, Yam hamMelaḥ), also known by other names, is a salt lake bordered by Jordan to the east and the West Bank and Israel to the west. It lies in the Jordan Rift Valley, and its main tributary is the Jordan River. As of 2019, the lake's surface is below sea level, making its shores the lowest land-based elevation on Earth. It is deep, the deepest hypersaline lake in the world. With a salinity of 342 g/kg, or 34.
Polar desertPolar deserts are the regions of Earth that fall under an ice cap climate (EF under the Köppen classification). Despite rainfall totals low enough to normally classify as a desert, polar deserts are distinguished from true deserts ( () or () under the Köppen classification) by low annual temperatures and evapotranspiration. Most polar deserts are covered in ice sheets, ice fields, or ice caps, and they are also called white deserts. Polar deserts are one of two polar biomes, the other being Arctic tundra.
Western HemisphereThe Western Hemisphere is the half of the planet Earth that lies west of the Prime Meridian (which crosses Greenwich, London, England) and east of the 180th meridian. The other half is called the Eastern Hemisphere. Politically, the term Western Hemisphere is often used as a metonym for the Americas, even though geographically the hemisphere also includes parts of other continents.
Trace gasTrace gases are gases that are present in small amounts within an environment such as a planet's atmosphere. Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up 99.934% of its atmosphere (not including water vapor). The abundance of a trace gas can range from a few parts per trillion (ppt) by volume to several hundred parts per million by volume (ppmv). When a trace gas is added into the atmosphere, that process is called a source.
Oxygen isotope ratio cycleOxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples, measured with the isotope fractionation. The ratio is linked to ancient ocean temperature which in turn reflects ancient climate. Cycles in the ratio mirror climate changes in the geological history of Earth.
Milankovitch cyclesMilankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. The term was coined and named after Serbian geophysicist and astronomer Milutin Milanković. In the 1920s, he hypothesized that variations in eccentricity, axial tilt, and precession combined to result in cyclical variations in the intra-annual and latitudinal distribution of solar radiation at the Earth's surface, and that this orbital forcing strongly influenced the Earth's climatic patterns.
Woolly mammothThe woolly mammoth (Mammuthus primigenius) is an extinct species of mammoth that lived during the Pleistocene until its extinction in the Holocene epoch. It was one of the last in a line of mammoth species, beginning with the African Mammuthus subplanifrons in the early Pliocene. The woolly mammoth began to diverge from the steppe mammoth about 800,000 years ago in East Asia. Its closest extant relative is the Asian elephant. The Columbian mammoth (Mammuthus columbi) lived alongside the woolly mammoth in North America, and DNA studies show that the two hybridised with each other.
Polar lowA polar low is a mesoscale, short-lived atmospheric low pressure system (depression) that is found over the ocean areas poleward of the main polar front in both the Northern and Southern Hemispheres, as well as the Sea of Japan. The systems usually have a horizontal length scale of less than and exist for no more than a couple of days. They are part of the larger class of mesoscale weather systems. Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas and oil platforms.
Land and water hemispheresThe land hemisphere and water hemisphere are the hemispheres of Earth containing the largest possible total areas of land and ocean, respectively. By definition (assuming that the entire surface can be classed as either "land" or "ocean"), the two hemispheres do not overlap. Determinations of the hemispheres vary slightly. One determination places the centre of the land hemisphere at (in the city of Nantes, France). The centre of the water hemisphere is the antipode of the centre of the land hemisphere, and is therefore located at (near New Zealand's Bounty Islands in the Pacific Ocean).
