Remote Sensing of Ice Coverage
on Disko Island, Greenland

by Jeffrey Girton, Alexander Lyon, Stephanie Payne

for ES 771 - Remote Sensing at Emporia State University Fall 2010


Introduction

Increasing global temperatures have the potential to expedite melting of glacial covered areas. Remote sensing of glacial covered areas on a temporal scale can provide visual evidence of an increase in glacial melting. The change in glacial coverage over time can be utilized to gain a more complete understanding of how anthropogenic actions can affect the environment. This project reports the amount of ice coverage from Disko Island of Greenland over a ten year time span.

Greenland, translated as “Land of the people”, is the world’s largest island that is not a continent. For this project we examined the second largest island of Greenland called Disko Island. Disko Island is located off the west coast of Greenland at coordinates 69°45’0” and 53°40’0”. The population of Greenland and Disko Island are 57,637 and 1,100; respectively. The languages spoken in Greenland are Greenlandic and Danish. The ethnic groups in Greenland are divided into 88% Inuit and 12% Europeans. Disko Island has an area of 8,578 km2, a length of 160 km and highest elevation of 1,919 meters. The two main villages on Disko Island are Qequertaruaq, located in southern portion, and Kangerluk, located in western portion. Disko Island is located southwest of the Nuussuaq Peninsula and Sullorsuaq Strait; north of Disko Bay the inlet bay of Baffin Island; and to the west of the main island of Greenland. The economy of Disko Island is supported by fishing, shrimp sales and mining various mineral deposits. Transportation used includes; airplanes, boats, dog sledding, and snowmobiles. The inhabitants of Greenland actually do not look at ice melting as something negative. It allows their harbor to be thawed out year round and if the ice caps completely melt they will be able to mine for the minerals below those ice caps.

(click images to enlarge)

Image taken from Google Earth 2010

Methods

Images were downloaded from the United States Geological Survey (USGS) Global Visualization Viewer from 1999, 2001, 2003, 2005, 2007 and 2009. Images requirments; must have been taken during the months of August or September, must have minimal cloud cover and must fully contain Disko Island. Images were captured using Landsat 7. Images from 1999 and 2001 were captured when the scan line corrector (SLC) was on. Images from 2003, 2005, 2007 and 2009 were captured when the SLC was accidently and irreversibility shut off. Additional manipulation of SLC-off data information was required to remove line banding in the images. A filter pass was used to calculate new values for the blank line bands. Anomalous values obtained from the filter were removed from the scene. While these adjustments should have corrected the data it is important to note this change from SLC on; 1999 and 2001, and SLC off; 2003, 2005, 2007, 2009, images.The overlay feature was used on bands 2 and 5 to differentiate ice from the rest of the scene. The values were reclassified as Ice equal to 1 and everything equal to 0. The amount of ice was then determined for each year.The frist image, left, is a composite image taken in 2009 of Disko Island. This composite was made using band 2 (blue band), band 4 (green band), and band 5 (red band). The 245 composite allows for the selection of ice, however, it does not differentiate between snow and ice which could influence the results. This false-color composite shows snow and ice as light blue in color. The second image, right, shows the size of the window that was created for this project. Disko Island and a small portion of mainland Greenland are visible in the window. Ice coverage was selected from this window size and shown below.


Results

Using the images and the OVERLAY, HISTO and RECLASS programs within IDRISI Taiga a ratio was created to help identify ice coverage and eliminate non-useful land coverage. The resulting images show the area in blue as being the ice coverage.

Year
Ice Coverage
Percent Change in Ice
Coverage from Previous Image
Image
(click image to enlarge)
1999
4,312 km2
----
2001
1,464 km2
-66%
2003
2,684 km2
+46%
2005
1,881 km2
-30%
2007
1,793 km2
-5%
2009
1,768 km2
-1%

Graphical respresentation of the amount of ice coverage in km2

The mean global temperature for September has been calculated from 1961 to 1990 and is referred to as the Average Global Temperature Variance from mean. The variation from this long-term mean temperture was used to observe a warming or cooling of the global temperature, for a more information why click here. The mean value of global meterological elements over thirty-years is defined as a climatological normal. The climatological normal is then used as a base for current conditions to be compared. Every ten-years the National Climate Data Center calculates new thirty-year climatological normals. Positive values indicate a temperature higher than the long-term global average. A negative value indicates a temperature lower than the long-term global average. All values were positive which indicated that each year in the study was warmer than the long-term mean for Septemeber.

Year
Average Global Temperature Variance from Mean
1999
+0.67
2001
+0.84
2003
+0.67
2005
+0.68
2007
+0.49
2009
+0.57

Discussion

The effects of global warming on the climate can dramatically impact the environment. Anthropogenic processes that contribute to global warming must be reduced and eliminated to prevent further change to climate and the environment. This study focused only on a small window into the changes that can occur. For each of the years used in this study were warmer than the long-term mean temperature. This warming in global temperature can increase the melting of ice as was evident in this study. Overall, there was a decrease of 59% in ice coverage from 1999 to 2009. Note that images from 1999 and 2001 were obtained when the SLC was turned on; while images from 2003, 2005, 2007 and 2009 were obtained when the SLC was turned off. The large difference in values from 1999 and 2001 could possibly be a result of snow cover, instead of ice cover, as our results are unable to differentiate between snow and ice. Even if both SLC-on images, 1999 and 2001, are removed there is a decrease of 34% in ice coverage from 2003 to 2009.


Conclusion

This project, and similar projects, are now possible due to the use of remotely sensed data. The increase in popularity and usefulness of remotely sensed data can allow researchers to examine past, present, and project future conditions of our planet. This study showed an increase in mean global temperature from 1999 to 2009 against the long-term average mean from 1961 to 1990. This warming in global temperature can be related to the declines in ice coverage that were observed for Disko Island. Any anthropogenic processes that increase global warming need to addressed to prevent further melting of ice coverage. Ice melting could increase sea levels and displace people who live near coastlines worldwide.

Sources

USGU Global Visualization Viewer. Earth Resources Observation and Science Center

NOAA Satellite and Information Service. State of the Climate Global Analysis

NOAA Satellite and Information Service. Global Surface Temperature Anomalies

Kalaallit Nunaat low arctic tundra (NA1113). (2001). http://www.worldwildlife.org/wildworld/profiles/terrestrial/na/na1113_full.html

YDE, J. C., & KNUDSEN, N. T. (2007). 20th-century glacier fluctuations on disko Island (Qeqertarsuaq), Greenland. http://www.igsoc.org/annals/46/a46a036.pdf