Why is Arctic ice melting so fast?


Right now, it's cold in the Arctic. Days are dark, and ice grows to cover the dark sea. Come summer, lengthening days and warming temperatures will reverse that process. This is the ebb and flow of the Arctic, a natural cycle.

However, over the past several decades we have seen summers melt more and more of the ice that forms during the cold winter months. As a result, more and more dark seawater is exposed to the light of day.

NASA researchers, using several instruments on three separate satellites, has been collecting data for 15 years to find out why the ice is melting, and to be able to predict trends in future ice formation and melting. They reported on this data at the 2014 American Geophysical Union annual meeting, saying that 15 years worth is the absolute minimum amount of information needed for them to begin making long-term predictions. Climate trends, as opposed to weather trends, are averaged over 30 years, so they are about halfway there at this point in time.

The project to observe the Arctic is part of NASA's Clouds and the Earths Radiant Energy Systems (CERES) mission. They measure the Earth's reflected solar radiation, emitted thermal infrared radiation, and all emitted and reflected radiation.

The results so far indicate that the Arctic is absorbing energy from the sun five percent faster now during the summer months than it was when they first began monitoring in 2000. This is important because the rest of the Earth is still absorbing energy at pretty much the same rate.

Put into energetic terms, this means each square meter of the Arctic Ocean is absorbing approximately 10 more watts of solar energy than everywhere else. Interestingly, this is not uniform, and is regionally specific. For instance, the Beaufort Sea has been measured at 50 watts per square meter.

All this extra energy has an impact on sea ice melt. The Beaufort Sea is one of the more dramatic ice melt examples. And, the rate of ice loss in September in the Arctic overall is 13 percent per decade. Let me spell that out… the Arctic is absorbing more energy, the air temperature is warming, and the rate of ice melting is being multiplied over ten times each decade.

So, why is this happening? It partially has to do with albedo, or reflectivity. Ice and snow reflect the sun's light and energy, while dark oceans absorb it. Less summer ice means that things are going to warm up faster, creating a feed-forward cycle that will potentially lead to even further warming and melting.

Walt Meier discussed differences in the ice itself that contribute to this process. He said that young ice melts more easily than old ice due to surface features and salinity. This results in much more rapid melting each year, which exposes more old, thicker ice to the suns rays. Each year more old ice is lost only to be replaced during the winter with easily melting young ice. The Arctic has lost 1.4 million square kilometers of ice over the past 15 years.

Young, thin ice makes the Arctic more vulnerable to further summer melting. Further Jennifer Kay, said that cloud cover is not related to the observed absorbed radiation.