Close Window
North Slope Summer: Earth Image of the WeekJuly 27, 2012
North Slope-Beoufort Sea satellite image
Sea ice has returned to parts of Alaska's Arctic coast again since this image was taken on July 12.
The record melt of the Arctic sea ice pack in June and early July lead to a navigable corridor for shipping just off Alaska's northern coast by July 12, 2012.

A rare, sunny day across Alaska’s North Slope on that date provided a clear view from outer space of North America’s largest oil field.

When NASA’s Aqua satellite passed over Prudhoe Bay at midday, the midsummer sun had managed to warm the air at the Deadhorse airport, near the shores of the Arctic Ocean, to a balmy 64 degrees.

In the image to the right captured by the MODIS sensor on Aqua, thousands of small lakes can be seen dotting the tundra. This is a region normally frozen over except for a brief period of time between June and September.

Because of a layer of permafrost less than 3 feet beneath the surface, the melted snow has no place to soak into the soil.

That results in an abundance of small lakes and ponds, which turn into breeding grounds for voracious swarms of mosquitoes each summer.

Oil was discovered beneath Prudhoe Bay on March 12, 1968, by engineers from what is now called ARCO, and Exxon. It was soon estimated that there were about 25 billion barrels of oil lying beneath the tundra and adjacent coastal waters of the Arctic Ocean.

The 1973 oil crisis quickly made it economically feasible to not only drill more than 1,000 wells in America’s most remote region, but also to construct a pipeline across the state to deliver the crude to tanker ships in the Gulf of Alaska.

The Tran-Alaska Pipeline was completed in 1977, and extends 800 miles south from Prudhoe Bay to the Valdez Marine Terminal. Between 1977 and 2005, 13 billion barrels of oil were transported through the pipeline.

Production peaked in 1998 at 2 million barrels per day, but had fallen to only 943,000 per day by 2005. The once vast oil reserve was contained in porous rock formations between 5,000 and 20,000 feet beneath the surface.

But it has been able to rise to the wellheads under its own geologic pressure, eliminating the need for pumping. Thirty years of extraction from wells around Prudhoe Bay, and a vast network of satellite oil fields to the east and west, have considerably depleted the amount of oil beneath the region.

British Petroleum estimated in 2006 that only 2 billion barrels of oil remain that can be acquired with current technology.

Image: NASA MODIS Rapid Response System