Greenland Glaciers: How Their Ebb and Flow will Impact Sea Level Rise

It's no secret that Greenland's glaciers are melting in the face of warming temperatures, but a new analysis aims to show just how their ebb and flow will impact sea level rise in the future.

In northwestern Greenland, glaciers flow from the main ice sheet to the ocean in seasonal patterns, somewhat resembling a seesaw. The ice generally flows faster in the summer than in winter, and the ends of glaciers, jutting out into the ocean, also advance and retreat with the seasons.

The link between ice melt and rising sea levels is clear, but a team of scientists from the University of Washington takes this idea one step further, revealing some important connections between these seasonal patterns, sea ice cover and longer-term trends.

"Rising sea level can be hard on coastal communities, with higher storm surges, greater flooding and saltwater encroachment on freshwater," lead author Twila Moon said in a statement. "We know that sea level will go up in the future. The challenge is to understand how quickly it will rise, and one element of that is better understanding how Greenland glaciers behave."

From 2009-2014, Moon and her colleagues focused on 16 glaciers in northwest Greenland to gather data on glacier speed, terminus position (the "end" of the glacier in the ocean) and sea ice conditions.

While these factors independently don't seem to have much influence on one another, the team found in the long run, there was a strong relationship between the speed of glaciers and terminus location. When sea ice levels were especially low and glaciers' ends retreated more than normal and then didn't re-advance, the glaciers sped up, moving ice toward the sea more quickly. While low sea ice likely isn't fully responsible for these changes, researchers say, it may be a visible indication of other processes, such as subsurface ice melt, that also affect terminus retreat.

According to the study, the underlying mechanisms that drive seasonal glacier changes in Greenland, and around the world for that matter, are not necessarily the same ones causing longer-term trends. However, this study may help scientists spot the differences and thus better predict the impact of sea ice loss in the coming decades.

"We do know we're going to see sea ice reduction in this area, and it's possible we can begin to estimate how that may affect glacier velocities," Moon said. "It may be that we need to instead pay more attention to these out-of-bounds events, these anomalous years of very low sea ice or very high melt that likely have the greatest influence on longer-term trends."

The study results are described in more detail in the Journal of Geophysical Research-Earth Surface.

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