The Arctic and Antarctic regions have reached their respective 2016 maximum and minimum polar ice extents. See the blue graph lines. The Arctic winter ice maximum extent was the smallest on record. The Antarctic summer ice minimum was slightly less than the recent 30 year average.
Lesson on Arctic Albedo
The situation in the Arctic continues a trend toward decreasing amounts of sea ice as the albedo of the Arctic decreases. Albedo is a measure of how well a surface reflects solar energy. It is a ratio of outgoing to incoming energy. If a surface reflects 100% of the incoming energy, we say the albedo is 1.0 with no units. In this case, the reflecting surface retains none of the solar energy and does not heat up. If a surface reflects 0% of the energy, it has an albedo of 0.0. In this case, the absorbed energy heats up the surface.
Open ocean does not reflect solar energy effectively. It reflects about 6% and absorbs 94% heating the water. The albedo is 0.06 for open ocean surface. A sheet of bare ice over water reflects over 50% of the solar energy for an albedo of over 0.5. Snow covered ice over water is a very reflective surface with an albedo of up to 0.9 which means a small 10% of the solar energy gets absorbed. It doesn’t heat the reflecting surface very much.
In the Arctic and Greenland, melt ponds form on the surface of the snow covered ice as the solar energy increases toward summer months. The melt ponds are darker and have a lower albedo than snow and allow greater absorption of energy. The warming at the ponds causes greater extents of water. As the larger bodies of ice and snow melt away, this exposes more open ocean water to the incoming solar energy. Because of global warming, we seem to have passed a tipping point balance that regulated the extent of sea ice in the past in the Arctic. It is rapidly decreasing.
The result of this increased melting of the Arctic waters correlates strongly with the atmospheric warming of the far northern latitudes. It is greater there than anywhere else on Earth. What long term effects this will have on the future weather patterns and climate of the lower latitudes is not known. But, it will likely have some effects.
Melting of Greenland Ice
Large expanses of melt water accumulate on the deep Greenland ice surface during warmer months. The ponds of water find cracks and crevasses where it flows downward as in this video example. These grow in volume of flow to significant size. Where they go is not well know. It is suspected that they contribute to the forward speed of the glaciers near the coast line. The water decreases the friction of the glacier ice on the bedrock below.
When ice on land melts, it flows to the sea and raises sea level. Ice in the Arctic Ocean is already in the water. When it melts, the sea level does not rise.
The huge expanse of ice and snow covering Antarctica is half the size of Africa. It flows slowly toward the surrounding sea. In some places, thick shelves of ice hundreds of meters thick extend out over the sea water for hundreds of miles. These extensions of the outflowing glaciers act as a sort of brake to slow down the progress of the glaciers. If the ice shelves are gone, the glaciers gain speed and deposit more ice into the ocean. It melts and raises sea level faster. The International Panel on Climate Change predict up to 1 meter (3.3 ft) by 2100.
There have been observations of increased ice shelf break up in recent years. These increases have triggered warnings by climate scientists about the potential for larger sea level than the IPCC predicts in the decades ahead. Such rises would inundate large areas of highly populated cities and countries. Another warning was issued after a March 2016 publication in Nature. It stated that additional factors need to be considered concerning the ice shelf melting scenarios. Their projections state that sea level rise could be double what was originally forecast.