A-68A Iceberg Thinning at 2.5 cm per Dayhttps://phys.org/news/2020-12-a-68a-iceberg-thinning-cm-day.htmlUsing data from four different satellites, scientists from the Centre for Polar Observation and Modelling at the University of Leeds have produced the first assessment of the iceberg's changing shape.
The team first built a map of the icebergs initial thickness from measurements recorded by ESA's CryoSat satellite radar altimeter in the 12 months before it calved. This detailed map reveals that A-68 was originally, on average, 232 m thick, and 285 m at its thickest point. The berg has 30 m deep channels oriented parallel to its narrow side following the direction Larsen ice shelf was flowing out to sea before it snapped—a common feature related to ocean melting.
Since it has been drifting in the ocean, the iceberg's position and shape have been captured in a sequence of 11 images taken by two different satellites—the Copernicus Sentinel-1 mission, which has an all-weather and year-round imaging radar, and NASA's MODIS, which records images that are visible to the naked eye.
The imagery shows that the iceberg has halved in size from an initial area of 5664 sq km to its present extent of just 2606 sq km. A large proportion of this loss has been through the creation of smaller bergs, some of which are still afloat.
On average, the iceberg has thinned by 32 m, and by over 50 m in places—around a quarter of its initial thickness. When combined, the change in thickness and area amount to a 64% reduction in the iceberg's volume from 1467 to 526 cubic kilometers.
At its thickest section, the A-68A iceberg currently has a 206 m deep keel, and so the main section is unlikely to travel much closer to the island until it thins or breaks apart. However, two relatively large fragments which broke away on 21 December are considerably thinner, with keels that are up to 50 m shallower, and so these pose the greatest immediate threat.
Since it broke free, the average melting rate of A-68 has been 2.5 centimeters per day and the berg is now shedding 767 cubic meters of freshwater per second into the surrounding ocean—equivalent to 12 times the outflow of the River Thames.
http://www.esa.int/Applications/Observing_the_Earth/CryoSat/A-68A_iceberg_thinning_at_2.5_cm_per_day