Monitoring Larsen C Rift propagation, Calving and Iceberg Deformation: through VEDAS developed Automatic Technique
Antarctica, the southernmost continent, is an ice-covered land mass. 90% of world’s fresh water is in Antarctica. It is broadly divided in to East Antarctica and West Antarctica. Antarctic Peninsula is one of the test beds for monitoring climate variation. The broader categories of ice features of Antarctica include ice sheet (ice layer covering landmass over an extensive period), ice shelf (Floating sheet of ice permanently attached to land mass), iceberg (the floating land ice), glaciers (slowly moving ice mass), ice rise (grounded ice shelf) and sea ice (frozen ocean water).
Larsen C is the fourth largest ice shelf in Antarctica. A rift is a large through fracture that propagates transverse to ice flow direction and acts as a precursor to ice calving. Initially, small cracks form due to longitudinal stress which results into crevasses and finally forms the rift. The rift propagation and calving (the disintegration) of ice into ice berg are natural phenomena in the Antarctic ice margins. Global warming may be attributed as one of the causative factors for the unusual fast rift propagation in the Larsen C in the recent past. This region has thus been the focus of many scientific studies, and regular research related observations. The Larsen C Ice Shelf covers an area of approximately 50,000 square kilometres between Jason Peninsula in the North and Hearst Island in the South. The large scale disintegration of ice shelf into ice bergs and rift propagation has focussed limelight on Larsen C ice shelves during the last decades.
A huge portion of the Larsen C ice shelf (~50,000 square kilometers) in Antarctic Peninsula calved away to an iceberg of area ~6200 square kilometers between 10th July and 12th July, 2017. The iceberg is named as A 68 by scientific community. This event is closely monitored by Team AMHTDG/EPSA/SAC since February 2017, ever since news of the possible detachment of Larsen C from the landmass started appearing on internet and the results of rift was reported by SAC, through SACNET, VYOM and VEDAS. This has created interest among the scientists working in the field of cryosphere science.
An automatic technique was subsequently developed for detecting and monitoring calving events and rift propagation at Larsen C using available SAR data. C band SAR data from Sentinel-1(repeat cycle of 12 days) is made available at a regular interval through https://scihub.copernicus.eu/dhus Copernicus site by European Space Agency. A software module was developed to download and unzip the data automatically from the Copernicus site. A software module developed will check for the data and update the process. The same module is being modified to accommodate the SCATSAT-1 high resolution product (2 km) data which will be soon available in VEDAS and can be used for future RISAT series of data sets.
India, with its two Indian Antarctic research stations Maitri and Bharati, have also been contributing in routine scientific expeditions and scientific research. A similar Monitoring System will be available at VEDAS pertaining to Bharati and Maitri, during the next Indian Scientific Expedition to Antarctica during December 2017 – April 2018. The module for automatic downloading of Sentinel 1 data every 12 days, and monitoring of the region was developed by SAC.