4 September 2008 MAR 110 Section #3 Glossary 1MAR 110 Natural Hazards and the Oceans Section #3 Glossary Abrupt Climate Change. Significant climate regime changes that occur very rapidly compared to the period of the change. For example the 3OF temperature decrease between the Medieval Warm Period to the Little Ice Age occurred in about 10years, while the LIA lasted about 500years before temperatures increased 3OF. Albedo. The degree to which short wave solar radiation is reflected from any surface or object. Climatic Feedback. The situation where one process reinforces (positive) or cancels (negative) the effect of another. An example of positive feedback is operating with “run-away cooling; that is when cooling leads to increased snow cover which increases the reflection of solar radiation leading to even more cooling. El Nino. An oceanographic event occurring on a repetitive basis in the equatorial Pacific Ocean, marked by abnormally warm surface waters and reduced upwelling in the eastern Pacific at Christmas time (from Spanish, meaning 'The Child'). ENSO. Acronym for the words 'El Nino-Southern Oscillation', in reference to the process whereby easterly trade winds blowing in the tropics across the Pacific Ocean weaken or reverse allowing abnormally warm waters in the western Paciifc to move to the coast of Peru. Greenhouse Gas. One of the gasses in the atmosphere that absorb longwave radiation at selected wavelengths. Princpal gases are water vapor, carbon dioxide, and methane. Greenhouse Warming. Greenhouse gasses in the atmosphere restrict longwave radiation to outer space thereby inducing temperatures that are warmer than without the gases . Kelvin Wave. A water wave trapped along the boundary of a coast, channel, embayment, or two bodies of water differing in some physical characteristic. The wave moves slowly parallel to the boundary and has a height that decreases rapidly away from the boundary. The movement of water across the Pacific Ocean during an ENSO event occurs as a 500-1000 km long, 10-50 cm high Kelvin wave, trapped within 5° of the equator and moving eastward at a speed of 1-3 m s-l. La Nina. The opposite of an ENSO event, during which waters in the west Pacific are warmer than normal; trade winds or Walker circulation is stronger; and consequently rainfalls heavier in South-East Asia. Little Ice Age. A 500 year long period of reduced temperatures following the Medieval Warm Period which ended in 1300. Maunder Minimum. Refers to the lack of sunspots between 1650 and 1700 AD at the height of the Little Ice Age. Meandering. The process whereby a flow of air or water tends to become unstable and travel in a winding path. Medieval Warm Period. A 500 year long period of increased temperatures preceding the Little Ice Age before 1300. Monsoon. Defines any region characterized by a distinct 180° change in wind direction between summer and winter, resulting in seasonal alternation of copious rain and aridity. North Atlantic Oscillation. The tendency for air pressure to oscillate in intensity between the Icelandic Low and the Azores High. The oscillation reflects inter-annual variability in the strength of Rossby waves in the northern hemisphere. See also Southern Oscillation.4 September 2008 MAR 110 Section #3 Glossary 2North Pacific Oscillation. A statistical measure of the strength and position of the Aleutian low-pressure system, mainly in winter. The oscillation is linked to short-term climate change in North America. See also Southern Oscillation. Southern Oscillation. The usual movement of air in the tropical Pacific is strong easterly trades reinforced by low pressure over Indonesia-Australia and high pressure over the south-east Pacific. Every two to seven years, this low and high pattern weakens or even reverses, causing the trades to fail or become westerlies. It is this switching from one pattern to another that is the Southern Oscillation. See also North Atlantic Oscillation and North Pacific Oscillation. Sunspot. An area 20,000 km in diameter on the sun's surface featuring strong magnetic disturbance so strong that convective movement of heat to the surface is curtailed. Hence, the spot is darker because it is cooler. TAO Array. The Tropical Atmospheric Ocean array, seventy buoys moored in the central Pacific Ocean, used by NOAA to monitor surface water temperature, current speed and direction, and wind speed and direction. Teleconnection. The linkage of a measured climatic time series to another one at some distance across the globe. For instance, rainfall in Florida can be related, through the Southern Oscillation, to sea-surface temperature in northern Australia. Walker Circulation. The normal movement of air across the tropical Pacific is from the east, between a stationary high-pressure cell off the coast of South America, and a low-pressure zone over Indonesia-India. In the 1920s, Gilbert Walker discovered that the strength of this air movement determined the intensity of the Indian