The figure above is a [very] simple model displaying isostatic rebound of Greenland if its ice sheet were not present. The Greenland ice sheet (GISh) is 2,500 km north-south, 1,000 km east-west, 3 km thick, and covers almost 2 million square kilometers (or 80% of the island). Because of the weight of GISh, the continental lithosphere is depressed in an elastic motion. If the GISh were to be removed, the lithosphere would rise in reaction. This rebounding process is known as isostasy and in case of ice sheets, glacial rebound.

Underneath any vast ice sheet is a land surface not unlike any other ice-free surface on earth. It has valleys, hills, plains, etc. Therefore, we see that in Greenland the underlying topography, the Bedrock (or simply the Bed), is shaped as a concave, and with the removal of the ice sheet it rises and assumes a less curved form.

PS: Please note that this is purely for visualization purposes and not to be used in scientific analysis.

After having been to northern Greenland (Thule Air Base) for the first time back in May (see Part I & Part II), there might be a chance that I’ll travel down to the southern tip of South America in November. The Antarctic part of NASA Operation IceBridge (OIB) is based at Punta Arenas, Chile, and involves science flights on the NASA DC-8 over Antarctica to take airborne remote sensing measurements similar to those taken in the Arctic.

The image above displays a segment of the flight plan over Antarctica that covers Recovery (including Recovery Ice Stream), Slessor Glaciers and the Bailey Ice Stream. There will also be flights that go further inland to the Recovery Subglacial Lakes, part of which was covered by the AGAP project during the International Polar Year 2007/2008.

This month marks my one year anniversary working at the Lamont-Doherty Earth Observatory of Columbia University. One of the earliest projects I’ve been working on was the Antarctica’s Gamburtsev Province (AGAP).

The figures above display the bedrock topography of central Antarctica under the East Antarctic Ice Sheet. The “Before” figure is a subset of the digital elevation model of Antarctic bedrock created by the British Antarctic Survey (BAS) using data from surveys from the past 50 years. BAS is currently working on a second version of BEDMAP. The “After” figure displays a grid of study area using data collected during AGAP. As you can see, AGAP provided the scientific community with previously unknown topographic detail of the Antarctic bedrock. Both “Before” and “After” figures have outline vectors of the AGAP survey flights overlain.

Here is a quick primer on the AGAP project:

During the International Polar Year 2007 – 2009, scientists from six nations collaborated on a multi-disciplinary investigation of the Gamburtsevs, the least explored mountain range on Earth buried beneath the East Antarctic Ice Sheet, as part of the Antarctic Gamburtsev Province (AGAP) project.

The AGAP project collected more than 120,000 line km of new aerogeophysical data using two Twin Otter aircraft.  Data included ice penetrating radar, magnetometer, gravimeter and laser altimeter measurements. The main AGAP survey grid included north-south lines spaced 5 km apart, with crossing lines every 33 km and transects over the Vostok Subglacial Highlands, South Pole and southern Recovery lakes region. 150-MHz ice penetrating radars with bandwidths of 15 to 20 MHz measured ice thickness, bedrock topography, sub-ice hydrology, and produced high-resolution images of the internal structure of the East Antarctic Ice Sheet. Magnetic data map geologic structures across the mountain range, while gravity data provide new insights into the tectonic evolution and crustal thickness of the region. A swath-scanning laser altimeter with a spatial resolution of 2 meters measured elevation and details of the ice surface.