By John J. Hidore
The Arctic: Rapid Changes in Temperature
November 1, 2013—Earth’s two polar regions of the Antarctic and Arctic differ a great deal. The Antarctic is a land mass surrounded by sea. In contrast to the Antarctic, the Arctic region is essentially a sea surrounded by land. This difference results in substantially different climatic conditions. Today the most rapid changes in temperature and climate are taking place in the sub-arctic regions of the northern hemisphere.
Extending over the North Pole and for varying distances southward is the Arctic Sea. In the winter months the sea is covered with a broken sheet of floating ice, up to perhaps 13 feet (4 meters) thick. Sea ice is defined as sea surface on which at least 15% of the surface is covered with ice. This ice is generally thickest in the middle of the sea and thins toward the surrounding land. Winter sea ice reaches the Arctic shoreline or very near it. However, even in winter there is always some open water. There are open cracks in the ice as the rotation of the earth causes stress in the ice. These cracks continually open and refreeze. When the sea is covered with snow and ice the bright surface absorbs only about 20% of the solar radiation. The rest is reflected back to space. This reflected sunlight does not alter the frozen surface.
Long Days And Intense Sunlight
In summer, the ice melts away from the shores of the continents and islands. The ice is thinner on the edges and so it thaws more readily. Around the summer solstice, in late June, the sun is highest in the sky and the days are the longest in the northern hemisphere. The long days and intense sunlight are a primary factor in the melting. The effect of the sun on open water is very different from that of sun on snow and ice. When the surface is open water, the water absorbs up to 90% of the radiation. This absorbed solar radiation warms the water. Away from shore there is sea ice which does not melt in the summer. This is thicker than ice near land masses.
The Receding Arctic Ice Pack
Satellite images of the Arctic ice have been available since the 1970s. The satellite data confirms that sea ice has declined throughout the Arctic Basin, but it has receded more in some places than others. At times, in recent years, the air temperatures over the arctic have been more than 10ºF (5.5 ºC) warmer than the average for the last 30 years. As a result of the warmer temperatures, the ice has been thawing further from shore and the remaining perennial ice pack has been getting thinner. In some areas it is only half as thick as it was a few decades ago. The present area of sea ice is about 50,000 mi2. (125,000km2). The ice pack has been melting faster in summer since the beginning of the twentieth century. The summer melting of sea ice has been taking place at an ever increasing rate. It is now taking place much faster than predictions made a decade ago. The additional heat absorbed by the Arctic Ocean contributes to global warming. The heat absorbed by the water in summer eventually escapes to the atmosphere in the fall and winter, as the water cools and freezes. The heat transferred from open water is 100 times greater than from ice.
Forecasting Arctic Warming
Early forecasting of Arctic warming had suggested a possible ice free path through the North West Passage in the summer months, perhaps between 2050 and 2100. However, to the astonishment of nearly everyone, at the end of the summer melt period in 2007, there was an open passage of water circling the Arctic Sea. It was hailed as the opening of the Northwest Passage from Atlantic to the Pacific.
Every summer for the past decade the area of sea ice has been below the average of the previous 20 years. In the summer of 2011 sixteen ships made the trip through the Northwest Passage. None of these required the use of an ice breaker ship. On September 16, 2012, Arctic sea ice reached the lowest since data has been available. In September 2013, a coal carrying freighter sailed through the Northwest Passage, also without the aid of an ice breaker. Whether the passage remains open in future years remains to be seen. On September 13, 2013, the area of sea ice reached its minimum for the summer. However, the area of sea ice actually expanded some 40% from the previous year. The additional ice had formed around the outside of the ice pack and was quite thin
The evidence of change in sea ice parallels other evidence that global warming is taking place much faster than past climate models have forecasted. At its current rate of melting, the Arctic Ocean could be totally ice free during the summers within the next decade. An ice free arctic will substantially alter the climate of the northern hemisphere sub-polar regions.
Sources of sea ice data
http://www.earthobservatory.nasa.gov/Features/World Of Change/sea ice
- Melting Arctic sea ice could increase summer rainfall in northwest Europe suggests new study (sciencedaily.com)
- Melting Arctic sea ice means it’s only going to get wetter for northern Europe. (independent.co.uk)
- Did melting Arctic sea ice cause wet summers? (environmentalresearchweb.org)
- Melting Arctic sea ice could increase summer rainfall in northwest Europe suggests new study (eurekalert.org)
- Melting Arctic sea ice could increase summer rainfall in northwest Europe suggests new study (esciencenews.com)
- Arctic melt ‘to blame for UK’s soggy summers’ (itv.com)
- Climate: Study links rainy European summers with dwindling Arctic sea ice (summitcountyvoice.com)
- Arctic Ice Loss a Factor in Weather Extremes – New Study (climatecrocks.com)