Climate: One more thing to worry about?

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Ongoing studies are detailing how melting ice sheets will affect sea level.

Eastern Greenland changes could threaten critical ocean current

By Bob Berwyn

The global climate agreement reached late last year in Paris isn’t going to stop the Greenland Ice Sheet from melting anytime soon. Even with an immediate halt to greenhouse gas emissions. there may be centuries more melting ahead, according to climate scientists.

And the meltdown could be more widespread than previously thought, according to National Snow and Ice Data Center scientist Lora Koenig, who gave an update on the latest research during this week’s Glen Gerberg Weather and Climate Summit in Breckenridge.Recently, a team of scientists made their way to the remote eastern edge of Greenland. When they started to drill into the ice to get data, they found that parts of the ice sheet are trapping water beneath the surface. More research is needed to know exactly how much water is stored there, but the findings may require scientists to revise their models of sea level rise.

That water is warming the ice sheet from within, and Koenig said there are a couple of ways to understand the new findings. On the one hand, the fact that water is being trapped under the ice could slow sea level rise. On the other hand, there’s a chance that, at some point, there could be a huge release of cold, fresh water — right into a sensitive part of the ocean where it could affect a critical current.

“If the water were to build up and release catastrophically … you’re releasing this water into the thermohaline pump, a lot of cold fresh water where you don’t really want it,” Koenig said, referring to an ocean circulation that helps balance ocean temperatures.

Along with describing the new research from eastern Greenland, Koenig gave a general update on Greenland research, explaining how satellite data, airplane-based research and field expeditions all help scientists understand what is going on with the ice sheet.

The bottom line is that the research has documented accelerated sea level rise and mass loss from the ice sheets, and that Greenland in the next few decades will outpace the contribution of glaciers in sea level rise. Based on the latest information, it seems safe to say that global sea level will rise at least one meter in the next hundred years, Koenig said, describing that figure as a middle-of-the-road estimate.

The facts are pretty clear going back to 2002, when early satellite missions detected areas of thinning, with some parts of the ice sheet already beyond a point of no return. The melting will cause significant changes over the long term, she said.

“That’s not an extreme amount when you look back over time,” she said. Looking back at the Earth’s history on a geologic time scale, sea level was six to nine meters higher when temperatures where just one degree warmer than today. Going back about 400,000 years, when the global average temperature was two degrees higher than today, sea level was six to 13 meters higher than now.

Other recent research on the Greenland ice sheet shows that extreme melting events can also change the runoff regime by forming a dense ice cap that could also increase the rate of sea level rise.

Some studies even suggest that the ice sheet may be near a tipping point that could trigger melting at a much faster rate than most current climate models project.

 

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