The Recent Nansen’s Ice-Shelf Calving Event : Comparison with Meteo-Climatic and Marine Conditions.

Abstract:

Ice shelves are important elements of the Cryosphere representing the interface between ice, atmosphere and ocean. They are also the mean to discharge ice from the interior ice sheets contributing to the continental ice mass balance. A sudden change in volume and extension of both ice shelves and floating glacier tongues can rapidly increase the ice streams speed and the ice sheets flow variability.The Nansen ice shelf represent a particular sensible interface between the floating ice and the Terra Nova Bay polynya, a sea area that remains ice-free for almost all the winter time , thus being one of the major responsible of the production of the Antarctic bottom water. Remote sensing technologies gave us the opportunity to observe and investigate on the formation and evolution of an incipient crevasse on the Nansen Ice Shelf, starting from 1999. The crack showed a steady and slow increase in length and rotation up to 2011 and then underwent an abrupt evolution. During the 2014 winter season, the crack reached its maximum elongation and the detachment of large tabular bergs seems to be very close. This should be the first observation of a detachment of large tabular bergs from the Nansen Ice Shelf since the beginning of satellite observations and is an opportunity to investigate complex processes. We analyzed the last ten years record of climate data over the Southern ocean to evaluate the relationships between the intense cyclonic activity, synoptic and mesoscale systems, ocean swells and calving events. We used ECMWF ERA-interim global atmospheric reanalysis model, Landsat images and in situ weather observations from AWS of the Italian Antarctic Program deployed over the Terra Nova Bay cost. Our preliminary results show a strong correlation between the occurrence of some anomalous meteorological configurations over the Southern Ocean and the sudden grow of the monitored crack in the ice shelf. If confirmed, together with this new arrangement of the cryosphere, some important consequences are expected in the ice shelf and polynya area.