The Arctic: Canary in the Cage for Global Warming

http://www.motherearthnews.com/nature-and-environment/the-arctic-canary-in-the-cage-for-global-warming.aspx

arctic meltThe Arctic is warming up faster than the rest of the planet! Atmospheric surface temperature of the Arctic has increased about 2.5 times faster than the overall global surface air temperature. This rapid increase in temperature is why the Arctic is considered the “canary in the cage” for global warming. 

Why is the Arctic warming up faster than other parts of the planet? Three major components contribute to the rapid warming of the Arctic: warm water from the Gulf Stream entering the Arctic Ocean, Arctic positive feedback factor (see The Arctic Feedback Factor and Climate Change) and continuous sunlight the Arctic receives for about half the year.

The Arctic Ocean is a circular ocean with the North Pole at its center.  The diameter of the Arctic Ocean is about 2,800 miles with North America and Greenland on one side and Europe and Asia on the other side.  Since the Arctic Ocean lies within the Arctic Circle it experiences extreme solar illumination, total darkness in the winter and unending days in the summer.  Historically much of the Arctic Ocean remains frozen year around.  However, during the unending summer sunlight the ice breaks and melts and refreezes during the next winter. 

The northward flow of Atlantic Water is the major means of heat advection (transfer of heat from the ocean water to the atmosphere) in the Arctic. The warm water of the Gulf Stream crosses the Atlantic Ocean as the North Atlantic Current which splits into two currents. The warm Atlantic Water flows northward into the Arctic Ocean.  The remainder of the water from the North Atlantic Current gives England its maritime climate before flowing southward as the Canary Current (see Global Heat Distribution and Climate Change).  

As the Arctic is transformed from the darkness of winter to summer the solar radiation from the unending daylight increases the atmospheric surface temperature. The atmospheric temperature continues to rise as heat is transferred from warm Atlantic Water to the atmosphere. This increasing temperature initiates the melting of the Arctic Ocean sea ice. Once the sea ice melts it exposes dark ocean water. Ice reflects incoming solar radiation which keeps the Arctic cool. On the other hand, the dark ocean water absorbs the incoming solar radiation which warms the ocean and triggers more melting. As more and more of the ocean loses its ice it absorbs more and more solar radiation, which accelerates melting exponentially.

Due to the rising temperature in the Arctic, the latter part of the 20th Century saw the Arctic Ocean summer melt consume more ice than the winter refreezing restored. By the end of the 20th Century the Arctic Ocean had 25 percent less summer ice than its historical average. In 2007 the Arctic summer sea ice loss was 40 percent less than its historical average. If the Arctic continues to warm at its current rate, it is estimated that the entire Arctic will be free of summer ice within a few decades.

Clearly, the Arctic is warming at a fast rate. The consequences of this rapid warming will be felt not only in the Arctic but also in other parts of the planet. The consequences of the Arctic warming will be discussed in my next posting.