This image shows elevation differences in Antarctica as measured by CryoSat in November 2013. There's a distinct pattern of alternating high and low elevations (shown in red and blue), which inverts closer to the South Pole. After careful analysis, it was discovered this is an artifact caused by the interaction of the polarization of CryoSat's antenna with the structure of the ice.
Near Antarctica's center, CryoSat measurements show an unusual pattern in the ice sheet's elevation. The discovery is leading to even more accurate measurements from the European Space Agency (ESA) ice mission.
CryoSat carries a radar altimeter that can see through clouds and in the dark, providing continuous measurements over areas like central Antarctica that are prone to bad weather and long periods of darkness. The radar measures the surface height variation of ice by timing the interval between the transmission and reception of short radar pulses as the satellite orbits Earth. The satellite collects data over Antarctica while passing on northbound and southbound orbits. However, the data show an unusual pattern of height differences where these orbits cross, radiating from the South Pole.
When this static pattern in the CryoSat measurements emerged, alarm bells started to ring, said Tom Armitage, University College London, who led the study. At first, we thought there could be an issue with the satellite itself, such as a miscalculation of the altitude, a timing error or a problem with one of the corrections we apply to the measurements.
After eliminating the possibility of these errors through careful experimentation, scientists discovered the pattern was caused by the way the satellite signal is scattered from the ice sheet surface. Antarctica has some of the strongest and most persistent winds on Earth, which leave permanent erosional and depositional features on the surface and in the snow pack. The scientists found that that these wind-driven features modify CryoSat's radar measurements to produce the pattern that has been detected.
Image courtesy of ESA/MSSL.
