Jay Zwally: Greenland ice loss is canary in coal mine

Jay Zally: The most important thing to know about the Earth’s ice sheets is that they are changing, that they are responding to climate change.

Dr. Jay Zwally is project scientist on NASA’s ICESat mission. Since 2003, ICESat has used lasers to precisely measure the thickness of ice near Earth’s poles. Zwally said that over the past decade Greenland’s ice sheet is losing more ice than it gains. It’s losing in excess of about 150 gigatons of ice every year.

Jay Zwally: One way to think about how much 150 gigatons is that if you had earth movers that carried 150 tons each, it would take 2,000 of them each minute to dump the excess ice into the ocean.

Dr. Zwally said average temperatures are rising faster at Greenland’s latitude than at middle latitudes on Earth. He also spoke of sea level rise.

Jay Zwally: The amount of sea level rise currently is about 3-4 millimeters per year. This adds up to about 16 inches at the present rate over the next hundred years. Even if there is no additional climate warming, sea level will continue at the same rate and rise about 16 inches over the next hundred years. But because of the changes that we’re seeing in Greenland, we know that this loss will increase, and that the sea level rise could be much larger than that.

The lasers that monitored ice thickness on ICESat stopped working in 2009. An airborne campaign called Operation ICE Bridge is currently bridging the gap in observations until the launch of the ICESat-II satellite in 2015.

Jay Zwally: The idea of the canary in the coal mine is that it’s a warning sign to get out of the coal mines when the gases build up. The things that are taking place on the Earth – the melting of the ice sheet in Greenland, the increase and the loss of sea ice in the Arctic ocean – these are warning signs of the same type.

Dr. Zwally described the ICESat mission in more detail.

Jay Zwally: ICESat is a satellite that was launched in 2003, and the primary purpose of this satellite was to study the ice sheet of Greenland and Antarctica, to find out whether they’re getting bigger or whether they’re getting smaller, and why. We needed to understand the impact of the ice sheets and the changes of these ice sheets in response to climate.

Dr. Zwally spoke more on why Greenland is losing more ice than it gains.

Jay Zwally: Temperatures have been getting warmer in Greenland. The warming in the Arctic, in Greenland and the Arctic Ocean and the sea ice areas is about two to three times the global average. The climate affects the ice sheet in several different ways. One is that the warmer air brings more snowfall over the ice sheet. Around the edges, the ice sheet is melting more. There are some places where the ice flows directly into the ocean and forms ice bergs. These ice bergs are accelerating. In addition, the warmer climate brings more snowfall to Greenland. And the warmer temperatures, the warmer water in the air both affect the melting at the edges. So it’s a race between growth in the center and loss at the edges. What’s happening in Greenland is that the loss processes are dominating the growth processes.

Our thanks today to NASA’s ICESat Mission, improving our understanding of the effects of Earth’s changing climate.

February 22, 2010

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