“The remaining 90 percent of the ice shelf continues to be held in place by two pinning points: the Bawden Ice Rise to the north of the rift and the Gipps Ice Rise to the south,” said Chris Shuman, a glaciologist with Goddard and the University of Maryland at Baltimore County. Ultimately, the rift stopped short of separating from the protrusion. In a shallow part of the sea floor underneath the ice shelf, a bedrock protrusion, named the Bawden Ice Rise, has served as an anchor point for the floating shelf for many decades. In the case of this rift, scientists were worried about the possible loss of a pinning point that helped keep Larsen C stable. Dark blue and purple areas are in the mid-range. Light blues and whites are the coldest areas, spanning most of the ice shelf and some areas of sea ice. Orange depicts where the surface is the warmest, most notably the areas of open ocean and of water topped by thin sea ice. It shows the relative warmth or coolness of the landscape. On June 17, 2017, the Thermal Infrared Sensor (TIRS) on Landsat 8 captured a false-color image of the crack and the surrounding ice shelf. Throughout the sunlit months of late 2016 and early 2017, scientists watched closely as a crack grew across the Larsen C ice shelf on the Antarctic Peninsula. Over the next months and years, researchers will monitor the response of Larsen C, and the glaciers that flow into it, through the use of satellite imagery, airborne surveys, automated geophysical instruments, and associated field work. Scientists have monitored the progression of the rift throughout the last year was using data from the European Space Agency Sentinel-1 satellites and thermal imagery from NASA's Landsat 8 spacecraft. When floating ice shelves disintegrate, they reduce the resistance to glacial flow and thus allow the grounded glaciers they were buttressing to significantly dump more ice into the ocean, raising sea levels. But sometimes ice sheets destabilize, either through the loss of a particularly big iceberg or through disintegration of an ice shelf, such as that of the Larsen A Ice Shelf in 1995 and the Larsen B Ice Shelf in 2002. Even relatively large calving events, where tabular ice chunks the size of Manhattan or bigger calve from the seaward front of the shelf, can be considered normal if the ice sheet is in overall balance. One way to assess the health of ice sheets is to look at their balance: when an ice sheet is in balance, the ice gained through snowfall equals the ice lost through melting and iceberg calving. Ice shelves fringe 75 percent of the Antarctic ice sheet. Download additional imagery from NASA Goddard's Scientific Visualization Studio. Image from July 12, 2017, from the MODIS instrument on NASA's Aqua satellite. Darker colors are colder, and brighter colors are warmer, so the rift between the iceberg and the ice shelf appears as a thin line of slightly warmer area. Thermal wavelength image of a large iceberg, which has calved off the Larsen C ice shelf. “Will the ice shelf weaken? Or possibly collapse, like its neighbors Larsen A and B? Will the glaciers behind the ice shelf accelerate and have a direct contribution to sea level rise? Or is this just a normal calving event?” “The interesting thing is what happens next, how the remaining ice shelf responds,” said Kelly Brunt, a glaciologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland and the University of Maryland in College Park. Now that the close to 2240 square-mile (5800 square kilometers) chunk of ice has broken away, the Larsen C shelf area has shrunk by approximately 10 percent. In 2014, a crack that had been slowly growing into the ice shelf for decades suddenly started to spread northwards, creating the nascent iceberg. Larsen C, a floating platform of glacial ice on the east side of the Antarctic Peninsula, is the fourth largest ice shelf ringing Earth’s southernmost continent. The final breakage was first reported by Project Midas, an Antarctic research project based in the United Kingdom. The calving of the massive new iceberg was captured by the Moderate Resolution Imaging Spectroradiometer on NASA’s Aqua satellite, and confirmed by the Visible Infrared Imaging Radiometer Suite instrument on the joint NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite. An iceberg about the size of the state of Delaware split off from Antarctica’s Larsen C ice shelf sometime between July 10 and July 12.
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