Saturday, February 11, 2012

Facts about the Mild Winter and Change in Earth Axis

I was curious how our sort-of-winter is doing compared to previous years. The current winter stands in stark contrast to the winter of two years ago. As of the beginning of this week, only 14.3% of the continental U.S. was covered in snow. As you can see in the list below, this is the lowest total over the last eight years. Two years ago, 56.0% of the lower 48 states were snow covered. This unusual lack of snow cover has allowed temperatures in areas that usually have snow, but do not this year (e.g. the Great Plains) to soar to record levels. Snow reflects much of the incoming solar radiation and a snow free darker surface absorbs much more of the solar radiation allowing surface temperatures to be much warmer. A friend of mine talked to a contractor in the eastern U.P. The contractor told him that the ground has not frozen yet this year so they are able to continue ground-breaking construction rather than having to wait until spring.

Snow Cover January 6 (lower 48 states)
2012 14.3%
2011 44.9%
2010 56.0%
2009 41.8%
2008 34.6%
2007 27.7%
2006 26.6%
2005 54.6%
2004 40.3%

Here is a picture of snow cover this year:

Here is a picture of snow cover last year:

One of the main reasons why these unusual winter patterns are occurring is that the jet stream has not moved south. The jet stream acts as a boundary between the cold air to the north and warm air to the south. Rather than dipping south as it usually does, the jet stream has been stagnant across the United States and Canadian border. When the jet stream “dips”, it becomes a trough and typically brings colder and stormier weather. However, these dips in the jet stream have not been substantial or long term to provide a sustaining cold pattern like it does in most winters.

Take a look at the record highs that were broken on February 1, 2012. 124 places broke their record high, with 27 areas tying their record high:

January 2012 is listed as the third least-snowy January for the contiguous United States since snow records began in 1966. December 2011 was ranked as the 11th least snowy on record. According to experts, if February comes in four to five degrees warmer, then the winter of 2012 will have a great shot of becoming the warmest winter recorded across the United States. It has also been reported that the top five warmest United States winters occurred after 1992, with the 1999-2000 winter season coming in as the warmest ever recorded.

As I was researching the winter weather statistics, I saw the heading for a web page that discusses the impact of earthquakes on the tilt of the earths axis.   That is a fact that I had not heard before.  Apparently the 8.9-magnitude earthquake in Japan that hit on March 11, 2011 shifted the earth’s axis. At first they thought the shift was around six inches (10 cm). Now experts think the tilt changed 15 inches (25 cm)!

As shown in the diagram above, the earth’s axis of rotation is tilted at an angle of 23.5 degrees relative to the orbital plane at which Earth travels around the sun. This tilt causes our four seasons.  The tilt in Earth’s axis is strongly influenced by the way mass is distributed over the planet. Large amounts of land mass and ice sheets in the northern hemisphere make the earth top-heavy. Powerful forces such as those from thrust-earthquakes or asteroid impacts can change the distribution of land mass and alter the earth’s axis.  When the earth’s axis changes, the daily rotation of earth can speed up or slow down much in the same way that a figure skater can change the speed of their spin by moving their arms up or down.

Other earthquakes that have changed the tilt of the axis include:

•The 8.8 magnitude earthquake in Chile in February 2010 shifted Earth’s axis by 7.6 centimeters and shortened the length of the day by 1.26 millionths of a second.
•The 9.1 magnitude earthquake in Sumatra on December 2004 shifted Earth’s axis by 7.0 centimeters and shortened the length of the day by 6.8 millionths of a second.

While small changes in the tilt of the earth’s axis caused by the 8.9-magnitude earthquake in Japan  – and other powerful earthquakes – will not have any noticeable effect on our day-to-day lives, these changes do serve to illustrate the power that can be unleashed by natural disasters.

In addition to the 30 foot tsunamis (see image above) that were triggered by the Japanese earthquake, it appears there were other impacts. One is that the quake moved the main island of Japan by eight feet (2.4 meters). Scientists know this because the location of the GPS station moved. Satellite images also show the shift:

The quake was the most powerful to hit the island nation in recorded history and the tsunami it unleashed traveled across the Pacific Ocean, triggering tsunami warnings and alerts for 50 countries and territories as far away as the western coasts of Canada, the U.S. and Chile. The quake triggered more than 160 aftershocks in the first 24 hours -- 141 measuring 5.0-magnitude or more.

The quake occurred as the earth's crust ruptured along an area about 250 miles (400 kilometers) long by 100 miles (160 kilometers) wide, as tectonic plates slipped more than 18 meters.

The Japanese quake was of similar strength to the 2004 earthquake in Indonesia that triggered a tsunami that killed over 200,000 people in more than a dozen countries around the Indian Ocean.

1 comment:

  1. Can you post some of your sources?