Larsen C - TerraSAR-X observes calving of A-68 iceberg
In recent days, the gigantic iceberg that has broken free of the Larsen C ice shelf on the Antarctic Peninsula has been in the headlines. Although the dislodging of icebergs from ice shelves is a natural occurrence and does indeed take place regularly in the Antarctic, as the media aptly reported, this event made a far larger impression than many others. Why is that? Probably because scientists have been using satellite data for months now to observe this region of the Antarctic in greater detail and have effectively been waiting for the event to occur. Moreover, the section of ice that dislodged this time is comparatively large, approximately seven times the size of Berlin.##markend##
It can by no means be concluded that this event is wholly attributable to global climate changes as a result of human activities. What is more, the actual calving of the iceberg will not lead to a rise in sea level, as it was already floating on the ocean before dislodging from the ice shelf, thus already displacing an amount of water relative to its mass. Preliminary studies on the calving also indicate that the detached section of ice is unlikely to lead to an accelerated flow and hence greater loss of mass of the glaciers located behind, contrary to what has been observed in previous collapses of the Antarctic ice shelf. And it would be conjecture at the moment to postulate whether this event will indeed precipitate a complete collapse of the entire Larsen C ice shelf, as was previously observed for Larsen A and Larsen B.
But there is no doubt that the detachment of this iceberg is a stunning natural spectacle that we have been able to observe from space thanks to our TerraSAR-X radar mission. The before/after images impressively depict the gargantuan forces that must have acted on the ice. In some places, the fissure grew by over five kilometres in a matter of days. In the deepest polar night and despite cloud cover, when optical satellites are virtually blind, their radar counterparts have an unobstructed view of the Earth, mapping its surface and observing how events of this kind unfold throughout the year. The TerraSAR-X data is received directly at the GARS O'Higgins Antarctic station, which is staffed throughout the year by alternating teams from the German Remote Sensing Data Center (DFD). The GARS O'Higgins Antarctic station is situated not far from Larsen C, at the north-western tip of the Antarctic Peninsula.
The GARS O'Higgins station has enabled the evaluation of extremely valuable data – unique in its spatial resolution – since the earliest days of the TerraSAR-X mission in 2007. Among other things, the DFD uses this data to infer parameters such as the flow speed of glaciers and mass balances of the ice shelf and glaciers. For instance, on the western side of the Antarctic Peninsula, directly opposite Larsen C, was another ice shelf – the Wordie ice shelf – which started to disintegrate in the 1960s and disappeared completely in 2009. We are particularly interested in determining the ongoing repercussions for the inland glaciers, whose flow speeds and mass balances continue to change to this day. Our research seeks to identify the underlying processes. Questions that drive us include: are the pivotal processes oceanic or atmospheric in nature? Are there differences between the events unfolding on the western and eastern sides of the Antarctic Peninsula? Will other icebergs dislodge from the Larsen C ice shelf, and if so, will it have similar knock-on effects to the collapse of the Wordie ice shelf?
It is unlikely that the detachment of the Larsen C iceberg will have significant effects on the evolution of the inland ice. Nevertheless, it clearly demonstrates how vulnerable the Earth system actually is, confirming our belief that we are researching a highly topical issue and that it is unequivocally worthwhile to continue our endeavours.