An aerial view of the icebergs near Kulusuk Island, off the southeastern coastline of Greenland

The Greenland event could have short-term and long-term implications for sea-level rise

Ice melting in the Freeland and sea-level rise

A warming climate holds important implications for other aspects of the global environment. Because of the slow process of heat diffusion in water, the world’s oceans are likely to continue to warm for several centuries in response to increases in greenhouse concentrations that have taken place so far. The combination of seawater’s thermal expansion associated with this warming and the melting of mountain glaciers is predicted to lead to an increase in global sea level of 0.45–0.82 meters (1.4–2.7 feet) by 2100 under the RCP 8.5 emissions scenario.

However, the actual rise in sea level could be considerably greater than this. It is probable that the continued warming of Greenland will cause its ice sheet to melt at accelerated rates. In addition, this level of surface warming may also melt the ice sheet of West Antarctica. Paleoclimatic evidence suggests that an additional 2 °C (3.6 °F) of warming could lead to the ultimate destruction of the Greenland Ice Sheet, an event that would add another 5 to 6 meters (16 to 20 feet) to predicted sea-level rise. Such an increase would submerge a substantial number of islands and lowland regions.

Coastal lowland regions vulnerable to sea-level rise include substantial parts of the U.S. Gulf Coast and Eastern Seaboard (including roughly the lower third of Florida), much of the Netherlands and Belgium (two of the European Low Countries), and heavily populated tropical areas such as Bangladesh. In addition, many of the world’s major cities—such as Tokyo, New York, Mumbai, Shanghai, and Dhaka—are located in lowland regions vulnerable to rising sea levels. With the loss of the West Antarctic ice sheet, additional sea-level rise would approach 10.5 meters (34 feet).

“When you have a melt event over areas that don’t normally see intense melt events, you can trigger those add-on effects,” said Lauren Andrews, a glaciologist with NASA’s Global Modeling and Assimilation Office, who noted that extensive melting as far north in Greenland as seen last week is not common. “[You] can really modify the surface in ways that the surface hasn’t been modified before.”

Large melting events can also create ice lenses or slabs of ice that can help increase meltwater runoff and mass loss on Greenland.

During large melt events, meltwater on the surface can seep through the snow and into firn, or a layer of compacted snow that is not yet compressed into glacial ice. Depending on the temperature of the water, snow, and firn, the meltwater can refreeze and can create ice lenses. If those lenses are extensive and thick, new meltwater cannot penetrate farther down. Water will then run off the snow and ice and empty into the ocean. Andrews said melt events can create thicker ice lenses — and potentially across a more widespread area.

Martin Stendel, a climate researcher at the Danish Meteorological Institute noted “When ice from the ice sheet melts, the remaining ice is at lower altitudes and can therefore melt easier. Even if we stopped all emission of greenhouse gases today, the sea level would continue to rise for the next several hundreds of years.” “In other words, what happens now has a relevance for the future,” Stendel wrote.

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