In this monthly feature, we span the globe to examine Our Changing Landscape with time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 5 billion square kilometers of data. This month, we look at changes in one of Alaska’s many glaciers, Carroll Glacier.
The RapidEye Constellation
RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers daily revisits to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a starting cost of $1.28 per square kilometer for all five spectral bands – academics do receive discounts. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.
Carroll Glacier, Alaska
As our regular readers might know, I have focused on climate change in more than a few of my Geospatial Times articles. And as I have stated in the past, whatever you believe the cause of it is – be it anthropogenic, natural cycles or a combination of both – few people refute that climate change is happening. In this Our Changing Landscape, we will look at the impacts of climate change on one of our most fragile landscapes, glaciers. But before we look at the impacts on glaciers specifically, let’s take a few moments to look at some of the shifts we have already seen as a result of climate change:
- The average global temperature increased by about 1 degree Celsius (or about 2 degrees Fahrenheit) in the 20th Century.
- Climate change has been linked to stronger storms such as hurricanes and tornadoes, longer droughts and even bleaching deaths of coral reefs.
- Increased temperatures caused by climate change have expanded the habitats of disease-carrying insects, bringing new infectious diseases to areas where they never existed.
- Since 1997, the mean sea level has risen by an average of 4 centimeters.
- Since 1980, the extent of September arctic ice coverage has declined from about 7 million square miles (sq mi) to less than 5 million sq mi.
- During the 2000s, new record highs were more than twice as common as new record low temperatures.
- Since the 1950s, there has been a 20% increase in extreme precipitation events across the USA.
- In the past 25 years, the average annual amount of damage caused by US wildfires has nearly doubled.
A glacier is a persistent mass of snow and ice that moves across the landscape. They are formed when local snow accumulation exceeds melting and sublimation. During the cold winter months, snow falls on glaciers, and over time, it is compressed into ice, joining the rest of the mass of the glacier. And during the warm summer months, snow and ice both melt and sublimate off the surface of the glacier and thus its surface area shrinks. As climate change has resulted in longer summers, shorter winters and warmer temperatures throughout the year, glaciers across our globe have been in a steady decline for decades.
Alaska is home to thousands of glaciers, many of them unnamed. Starting in the 1990’s, scientist have flown regular missions over Alaska’s glaciers, measuring their height with laser measuring devices (also called LiDAR). When these measurements are compared to ground surveys of the glaciers completed in the 1950s, 85% of them are lower, indicating a thinning of glacial mass (or put another way, indicating they are retreating). And since the 1950s, the rate of thinning has doubled as the climate warms.
Carroll Glacier is located in Alaska’s iconic Glacier Bay National Park and Preserve which is about 1,000 miles northwest of Seattle, Washington along the shores of the Gulf of Alaska. Carroll Glacier is 15-miles long with its terminus about one mile north of Queens Inlet. Pictures from 1906 to 2004 shows that Carroll Glacier has retreated significantly during this time period; now the question is how much retreat (or even possibly an advance) will medium resolution RapidEye images show?
If you would like to find out more about using RapidEye for your academic studies, engineering projects or any landscape analysis, let us know at [email protected] or (303) 993-3863.