An Acceleration in the Rising Sea Level

Photo credit: Doug Garland ‘10

On Monday, February 12th, 2018, a new study titled “Climate-change–driven accelerated sea-level rise detected in the altimeter era” was published in the journal Proceedings of the National Academy of Sciences. It stated that, according to 25 years of satellite data, the rise of the global sea level is accelerating dramatically. Lead author of the study, Steve Nerem, suggests that due to increased glacial melting, the rise in sea level may be two times higher than what was originally projected for year 2100. This means that the sea level would rise another 26 inches within the next 80 years, causing severe problems for the majority of coastal cities.

As the Earth’s atmosphere collects more and more greenhouse gases, the temperature of air and water molecules increase. Due to this gradual increase, warmer water expands, causing “thermal expansion” of the oceans. Author Steve Nerem said that about half of the 2.8 inches of the global mean sea level rise observed in the last 25 years was contributed by thermal expansion. Then, because of the warming of the atmosphere, glaciers on land melt into the oceans, which also raises the sea level.

Since 1992, organizations such as NASA, Centre national d’etudes spatiales (CNES), European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and the National Oceanic and Atmospheric Administration (NOAA) managed satellite missions Topex/Poseidon, Jason-1, Jason-2 and Jason-3 to capture satellite altimeter measurements of the global sea level. Brian Beckley, principal scientist of NASA Goddard and second author of the study, explained how the altimeter measurements were conducted. He said, “The Topex/Poseidon/Jason altimetry missions have been essentially providing the equivalent of a global network of nearly half a million accurate tide gauges, providing sea surface height information every 10 days for over 25 years.” He then said that with almost 30 years of climate data, ice loss from Greenland and Antarctica can now be observed in the mean global and regional sea level estimates.

Collecting a climate data record over the course of 25 years has a high chance of possessing variability. The main causes for variability in the altimeter data are El Niños, La Niñas, and volcanic activity. In order to account for potential errors, Nerem and his team used tide gauge measurements, which assess the satellite measurements from the ground. Despite the aid these measurements provide, not much else can be determined from them, such as whether or not the melting of ice sheets have truly caused significant changes in the average sea level.

Although the sea level rising is an imminent issue, there are ways in which it can be minimized and possibly controlled. There are natural buffers against the sea, such as mangroves, marshes, coral reefs, and barrier islands that aid in protecting the coasts from the ocean. Many of these buffer zones are being destroyed due to human interaction, but if they could be maintained, they can act as protection for cities around the world. However, that is only a temporary fix. If humanity were to lower the release of carbon-based emissions into Earth’s atmosphere, it would slow the heating of Earth’s particles, allowing the the glacial melting to reduce and the oceans to slow their expansion. By massively lowering the carbon footprint, perhaps the sea level would adjust to a manageable state.


Lexi Hengeveld

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