![]() The other important piece is satellite-based measurements of tiny shifts in Earth’s gravitational field at specific locations. Scientists measure the melt rate and elevation of glaciers during field studies to get one piece of the puzzle. Determining the contribution of land-based ice melting takes many steps. Moored and drifting buoys, satellites and water samples collected by ships show increases in sea surface temperature that cause ocean expansion. Scientists determined their relative contributions by taking many measurements. Over the past decade, the amount of sea level rise due to land-based ice melting has almost doubled that of ocean expansion. How fast depends mostly on the rate of glacier and ice sheet melting.įrom the 1970s through the early 2000s, melting ice and the ocean’s expansion contributed equally to the observed sea level rise. How much depends mostly on the amount of heat-trapping greenhouse gases, including carbon dioxide, emitted into the atmosphere and the subsequent warming. ![]() In Alaska and some parts of the Pacific Northwest, local sea level is falling as local factors, such as the land rebounding from the last glaciation, overshadow the overall global trend.Īs the ocean and the atmosphere continue to warm, water levels will continue to rise. In the Gulf of Mexico and Mid-Atlantic, local factors, such as land subsistence, are adding to the global rate and speeding up local sea level rise. Locally, changes in these currents can cause more water to build up next to the land, raising sea level. Changes in ocean circulation, such as when ocean currents are driven by the force of the wind and the different densities of water masses, based on their temperature and salinity.Sea level in close proximity drops and rises further away as water flows from where it was once held. As these areas lose their mass, their gravitational pull on the ocean weakens. They transfer the mass of their water to the ocean. Changes in gravitational forces, such as when mountain glaciers, ice caps and ice sheets in Greenland and Antarctica melt.Changes in land elevation, such as subsidence resulting from sediment compaction or extraction of ground water and fossil fuels, and glacial isostatic adjustment where the land continues to rebound after the last ice age.Local factors affect the rate of sea level change, and they can be grouped into three categories: ![]() The ocean is not like a bathtub where the water level rises and falls the same everywhere. Local sea level changes may be more or less than the global average, based on local conditions. With 40 percent of Americans living in densly populated coastal areas, having a clear understanding of sea level trends is critical to our societal and economic well being. Together with storm surge information, it also informs floodplain maps and safe evacuation routes. Sea level information also informs how we develop safe building codes, restore coastal habitats and site infrastructure. NOAA uses sea level data to produce nautical charts and promote safe navigation. Sea level data and tidal information establish marine boundaries, from private property lines to the borders of our nation’s territorial sea. Understanding sea level and its terminology is important. Mean sea level, also known as a tidal datum, is the average of the hourly water level heights observed at a local tide station over 19 years.Local sea level is the height of the water measured along the coast relative to a specific point on land.Global sea level is the average height of the ocean around the world.The real difference of this RTS is being able to control your hero character at the front of the battle lines, instead of as a general protected in the rear or the center of your group.There are several terms used to describe sea level: You can then use that Glory resource to improve your hero or other units, obtain helpers that give you bonuses such as improving morale, etc. Glory is only obtainable by doing specific things - crafting certain buildings, or accomplishing difficult tasks. The game uses the standard resource collection found in RTS games, except for Glory points. Greece, Egypt, Rome and Persia are all portrayed - and multiplayer has 24 maps supporting up to 8 players at a time. Rise & Fall: Civilizations at War is a historically-based real time strategy game where the player assumes the role of a wide variety of notable commanders - Alexander the Great, Achilles, Cleopatra, Ramses, Julius Caesar, and others - eight heroes in all.
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