Melting Greenland ice sheets may raise sea levels as much as an eye-popping seven meters (23 feet), endangering coastal cities like New York, Lagos, and Shanghai, according to a new study.
The researchers analyzed ice cores drilled from the high-elevation center of Greenland, where each year's snowfall melts a little bit and refreezes before being covered by a new season's worth of snow. Ice cores contain records of past melt intensity, allowing researchers to extend their records back to the 1650s.
The scientists said their equipment provides more historical proof of how ice melting happened in the last 350 years or since the sample is taken underneath.
The team analysed these results in combination with the imaging data collected by various satellites and the data from sophisticated climate models, which enabled them to determine the rate of ice melting, not only at core site, but also broadly across Greenland.
"We show that although melt started to increase around the pre- to post-industrial transition, it really stayed fairly low and stable until about the 1990s", Das said. In the warmer summer months, melting occurs across much of Greenland's ice sheet surface.
The complexity of ice melting, and the potential affects on the planet of the melting Greenland ice sheet mean that we need to seriously consider what impacts our actions today will have on the future, according to Dr Trusel. The study warns that if the ice sheet melting "continues at unprecedented rates", this could accelerate the already fast rate of sea level rise. This frozen meltwater creates distinct ice bands that pile up over years to form layers of densely packed ice.
Traffic-pole-sized ice cores were sent to labs in the United States where their physical and chemical properties were assessed. A new study shows this massive melt-out wasn't just an anomaly compared with the last 40 years, but the last 350. Thicker melt layers represented years of higher melting, while thinner sections indicated years with less melting. Mwltwater from the ice sheet runs off into the ocean, contributing to sea level rise. The researchers claim that the thickness of the annual melt layers can also track how much melting was occurring at different sites, at the lower-elevations edges of the ice sheet.
Their report was published in the journal Nature. The rate at which it is taking place jumped dramatically during the 20th to early 21st century.
"We have had a sense that there's been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time", he said. The satellites used to study ice sheet melting around the world haven't been around long enough to capture a complete picture of the melting process.