Sea level rise (SLR) is an important threat to coastal areas around the world. It can affect human communities, wildlife habitats, infrastructure, agriculture, and gross domestic product. Many people live in low-lying coastal areas, and as SLR increases, they may need to relocate. Wetlands that provide vital protection from storms and shelter for crops may be destroyed, and life farther inland can be threatened as salt water contaminates soil and groundwater.
SLR is caused by two primary factors: thermal expansion of ocean waters due to warming, and melting of glaciers and ice sheets. The warming of the oceans is caused by human-caused climate change, mainly from burning fossil fuels. The ocean absorbs about 90% of the excess heat that is causing global warming, and as the water warms it expands. The melting of the polar ice sheets, which hold billions of tons of freshwater, is also contributing to sea-level rise.
Scientists have long tried to get a handle on sea level changes by studying sediment and ice cores from the Earth’s surface, as well as using tide gauges to measure global sea levels. However, satellites offer a much more comprehensive view of global sea levels. The TOPEX/Poseidon and Jason satellites, for example, measure global sea levels by bouncing radar signals off the ocean surface.
The satellite data show that the Earth’s crust has been rebounding after the massive glacier melt in the past interglacial period. This is known as the Glacier Isostatic Adjustment (GIA) land movement, and it must be corrected for when assessing SLR from tide gauge measurements.
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