Updated: Mar 3
It is no surprise that sea level is rising. Although it is a result of many different factors, it is an issue that must be solved immediately.
Why does the rising sea level matter?
In the United States, about 30% of the population lives in coastal areas with a high population density, where sea level affects flooding, coastline erosion, and storm threats. According to the United Nations' Atlas of the Oceans, eight of the world's ten largest cities are located near a shore. Rising oceans pose a threat to infrastructure critical to local jobs and regional businesses in metropolitan areas along coasts around the world. Sea level rise threatens roads, bridges, subways, water supplies, oil and gas wells, power facilities, sewage treatment plants, landfills, and a long list of other structures. Rising sea levels put pressure on coastal ecosystems that provide recreation, storm protection, and habitat for fish and wildlife, including commercially vital fisheries. Saltwater is infiltrating freshwater aquifers as sea levels rise, threatening municipal and agricultural water sources as well as natural habitats.
What is causing sea levels to rise?
The global sea level is rising in two ways as a result of global warming. To begin with, glaciers and ice sheets around the planet are melting, releasing water into the ocean. Second, when the water heats, the volume of the ocean expands. A loss in the amount of liquid water on land—aquifers, lakes and reservoirs, rivers, and soil moisture—is a third, much smaller component to sea level rise. Groundwater pumping is largely to blame for this transfer of liquid water from land to ocean.
Measuring Sea Level
Tide gauges and satellite altimeters are the two main methods for measuring sea level. For more than a century, tide gauge stations throughout the world have used a range of manual and automatic sensors to monitor the daily high and low tides. Scientists can generate a worldwide average and modify it for seasonal changes using data from hundreds of locations throughout the world. Since the early 1990s, sea level has been measured from space using radar altimeters, which assess the return speed and strength of a radar pulse directed towards the ocean to calculate the height of the sea surface. The return signal is faster and stronger as the sea level rises.
Scientists analyze sea surface temperature with moored and floating buoys, satellites, and water samples obtained by ships to estimate how much of the observed sea level rise is attributable to thermal expansion. A global fleet of aquatic robots measures temperature in the upper half of the ocean. Instruments lowered from oceanographic research ships measure deeper temperatures.
Future Sea Level Rise
Additional sea level rise is unavoidable as global temperatures continue to climb. How much and when depends primarily on future greenhouse gas emission rates. Another source of uncertainty is whether the world's ice sheets, such as those in Antarctica and Greenland, will melt in a steady, predictable manner as the planet warms, or whether they will hit a tipping point and collapse suddenly.