Geo Jocks: Oceans Rising

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If Teen Vogue covers something, it must be big. So it is no surprise that the newest study on fast-rising sea levels made it between the glossy covers of the teeny-bopper magazine. The study, led by Rutgers University scientist Robert Kopp and published in the Proceedings of the National Academy of Sciences, found with 95 percent confidence that sea levels rose faster in the 20th century than in any of the previous 27 centuries. Geologically speaking, this is a relatively short timescale, which is why the study also hypothesized — using oceanographic modeling — what the modern sea level would look like without anthropogenic greenhouse warming.

According to the authors, seas rose globally about 14 centimeters since 1900, and recently at the rate of 3.4 millimeters per year. The authors suggest the sea level rise of the past century can be attributed to humans and that seas could have actually fallen by three centimeters had humans not continued to introduce greenhouse gases into the atmosphere. Additionally, it predicts that sea level rise in the 21st century will, not surprisingly, outpace 20th century rise, falling in line with the global average mean temperature “hockey stick” curve, so named for its sharp 20th century upturn.

The first of its kind published in a high-impact journal, the Kopp paper synthesized regional datasets from around the world to develop a highly-localized model for rising seas, therefore improving accuracy. By including datasets from numerous authors in many locations, Kopp and the other researchers were able to build on the work of others and extrapolate globally.

Geologists and earth scientists study the geology of coastal areas, a field referred to as “coastal geomorphology,” to determine past and future sea level change. Measurements of changing ocean levels have improved with the advent of new technologies used to measure sea height relative to the coasts. In the early 19th century, Thomas Jefferson established the U.S. Coast and Geodetic Survey to map and monitor the young country’s coastlines. The data from these surveys, in combination with repeat aerial photography initiated in the 20th century as well as modern satellite imagery, provide a near-complete glimpse at the coastline changes of the past 200 years.

Using these databases and other geologic field studies, scientists map the rising oceans and correlate it to increased temperatures. By understanding the past relationship between temperature and ocean levels, they can better predict future changes as ice melt and thermal expansion of the ocean lead to higher seas across the globe.