Following are NASA images and commentary that highlight the changes occurring and illustrate the vastness, relatedness, and beauty of the planet Earth….as a "very large" storm approaches the Tahoe Region.

Shrinking Ice Cap
NASA satellites keep a close watch on changes in the Arctic Ocean. Below is an image taken November 14, 2007 showing the historic (normal) size of the polar ice cap floating at the North Pole. In the past, the outer edge of the ice and snow in the cap has fluctuated within predictable boundaries throughout the year.

For orientation, the actual, geographic North Pole is at the small, gray circle in the middle of the image. Greenland is in the center toward the bottom. Canada and Alaska sweep upward on the left. Alaska is on the edge of the (blue) Bering Strait, which is the Pacific end of the elusive Northwest Passage across the top of the world that eluded explorers for centuries.



The second image (below) was taken September 16, 2007. The white ice cap shrunk about 400,000 square miles in the last year. Over the last ten years, there has been a reduction in ice cover of about 40,000 square miles per year. So the rate at which ice and snow turned into water accelerated in 2007.


The red arrow is the primary, long-sought, Northwest Passage between the Atlantic and the Pacific. There are scientists who predict the entire Arctic will be ice-free as soon as 2040. Then the North Pole would be just a geographic point in the Arctic Ocean. There would be no ice to stand on.

Antarctica
The continent at the bottom of the world is a white jewel in an often dark and stormy sea. Unlike the North Pole, the South Pole is in the middle of a large landmass 5.4 million square miles in size, the fifth largest of the seven continents on the planet.

About 98% of Antarctica is covered by ice, which averages about a mile thick. But the ice which covers Antarctica is shrinking measurably in numerous places. The South Pole itself is located on a high, windy, very cold and desolate, desert. There is hardly any precipitation in Antarctica except along the coasts.

Early human exploration of the continent (by Shackleton, Amundsen, Scott, Byrd, Cook, Wilkes, etc.) is the source of many dramatic stories. Antarctica is a harsh place.



Greenland
This is the largest island in the world--836,109 square miles, about one quarter the size of the U.S. Greenland is experiencing a melt down similar to the Arctic ice cap.The image shows, in the reddish colors, the parts of Greenland where melting has been the most prominent in 2007.

Ozone
Ozone (O3) is a gas composed of three oxygen atoms. Ozone occurs mostly in the earth's upper atmosphere. (There is some at ground level.) The ozone "layer" that is naturally 10 to 30 miles above earth shields the planet from the sun's harmful ultraviolet (UV) rays. Excessive UV radiation is harmful to agriculture, the marine food chain, human skin, and human eyes.


In recent times there has been a depletion in the thickness of the ozone layer (a "hole") over Antarctica. The seasonal hole is the result of cold weather in Antarctica and the impact of ozone-depleting chemicals in the lower atmosphere, many of which come from human-produced compounds. In the image (above), taken from outer space, the Antarctic shows faintly through the (bluish) ozone hole. The ozone layer, or lack thereof, also plays a part in what happens to ocean-surface temperatures.

Pacific Ocean
Warm water expands and cool water contracts. Therefore, the temperature of the sea affects the actual height of the sea's surface. The temperature of the sea in various locations is a key factor in creating weather patterns across continents, e.g., the USA.

The October 16, 2007 image below, which looks like a Christmas tree ornament, shows where the temperature (height) in the Pacific was higher or lower than the long-term (1993-2005) average temperature. Areas warmer than average appear in yellow and red; areas cooler than the average temperature appear in purple and blue.


The bright blue band along the equator indicates a continuation of La Nina conditions that have been building since February 2007. La Nina often means drought in the American Southwest and Southeast.

Rainfall Patterns--USA
During the first eight months of 2007, drought dominated both coasts of the USA and the Great Plains states saw far more rain than average. In the NASA image below, red and yellow colors indicate below average rainfall; the green and blue colors indicate more rainfall than average (1992-2006). The trends in rainfall have an impact on drinking water availability, snowfall levels in winter, wildfire frequency, crop heath, animal migration, etc.



Lake Tahoe
The High Sierra is and will be affected by the factors outlined--warming, melting, ozone, sea water temperatures, rainfall--touched on above. To a significant extent, the High Sierra depends on the weather, economically. The first week in January 2008 should be interesting.