The polar ice has been thinning steadily over the years. Where there used to be thick ice, composed of layers formed over multiple years, nowadays the polar region is largely covered with single-year ice, a much thinner and more temporary layer that's replaced every year. This less durable stuff is significantly more prone to melting away -- which is exactly what it's doing. In 2007, the melt came within 700 miles of the pole. According to polar scientists, the ocean will open up even further this year -- probably, depending on weather, all the way to the pole. One of the useful features of a big patch of white ice is that it reflects sunlight and reduces the ambient temperature. Without that icy albedo, the Earth is likely to absorb more heat, creating a positive feedback loop and speeding up the global warming process.