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Mail service for many users is down due to mutiple hardware failures. We are working on the problem.
1500 feet above the ground surface is where our suite of instruments normally operates, but for this flight we are taking them up higher, much higher, in fact over 20 times our normal range to 33,000 feet. Our flight plan is to repeat lines surveyed in a previous years by NASA’s Land, Vegetation Ice Sensor (LVIS) a scanning laser altimeter. LVIS has collected data as part of the IceBridge instrument suite in the past, but it was flown separately at high altitude on its own plane, in order to map large areas of both land and sea ice. This flight will refly some of LVIS’s work but using a subset of the instruments on our plane, narrow swath-scanning lidar, the digital mapping camera system, the gravimeter, and our depth radar.
At our higher elevation we will fly faster and can cover a lot of ground. The landscape of Antarctica can be hard to get ones head around – a glacier catchment is usually too big to fit into one field of view, so we see it bit by bit, and try to build up a physical picture in the same way we build up our understanding of the system – piece by piece. We have flown several missions into the Amundsen Sea region on the west Antarctic coast in the past, but this was the first time where we could really see the context of all of these different glaciers – flowing into the same embayment, forming ice shelves, calving ice bergs, and drifting northwards through the sea ice.
The flight offers views of some of the most noteworthy features in Antarctica. Pine Island Glacier, one of world’s fastest streaming glaciers, developed an 18 mile crack along its face in the fall of 2011 which spread further over the last few months. The crack will inevitably lead to breakage, dropping an iceberg which scientists have estimated will be close to 300 pound in size.
Bordering the glacier is one of two shield volcanoes we passed over during our flight. Pushing up through the Antarctic white mask, Mount Murphy diverts the ice streaming along the glacier. A steeply sloped massive 8 million year old peak, Mount Murphy pulls my thoughts back New York as it was named for an Antarctic bird expert from the American Museum of Natural History.
From Mount Murphy we continue to the second shield volcano, Mount Takahe. Ash from 7900 years ago found in an ice core from the neighboring Siple Dome has been attributed to an eruption from this volcano. This massive potentially active volcano is about 780 cubic kms in size. The volcano was named by a science team participating in the International Geophysical Year (1957-8) after the nickname of the plane providing their air support …an unusual name for a plane as its origin is that of a plump indigenous Māori bird from New Zealand which happens to be flightless! Regardless the rather round Mount Takahe soars high above the glacier as we move overtop.
From there we fly over the tongue of Thwaites Glacier as it calves icebergs into the Amundsen Sea. To read more about Thwaites check out my first blog of the season: http://blogs.ei.columbia.edu/2012/10/18/launching-the-season-with-a-key-mission-icebridge-antarctica-2012/
For more on the IceBridge project visit:
Named after Edith Ronne, the first American woman to set foot on this southern continent, the Ronne Ice Shelf is tucked just to the East of the Antarctic Peninsula on the backside of the Transantarctic Mountains. With an area measured at 422,000 square kms, this is the second largest ice shelf in Antarctica. This vast icy expanse stretches into an indentation in the Antarctic coastline called the Weddell Sea, and gained some attention this past spring when scientists identified a mechanism that will force warming ocean water up against Ronne, which over time will cause it to thin and weaken (Hellmer, H. H. et al., 2012). Ice shelves are important barriers slowing the flux of ice moving off the land into the surrounding ocean. Any weakening in the tight connection of this ice to the land, either at the bottom where the shelf freezes to the ground below or where at the edges where it is tightly fused to the continent, can have major impacts on the speed and volume (flux) of ice moving off the land and into the oceans.
The current mission is being flown to measure the flux of ice currently coming into the Ronne Ice Shelf from the surrounding Antarctic landmass. To determine this we focus on the ‘grounding line’, the area where the ice changes from being frozen solid to the land below to floating as part of the ice shelf. To understand how much ice is moving over the grounding line, we have to understand how much ice is at the grounding line, and to do this we have to fly along the grounding line (or slightly inshore of it).
In many areas of Antarctica, even knowing where the grounding line is takes a lot of work. Much of that work is done using satellite data through a process called “interferometry”. This process compares the returning radar signal from different satellite passes to determine where the ice begins to move under the influence of the ocean tides. In this scale, ice that is responding to the rise and fall of the tides is floating ice, and from this we can mark the grounding line. While technique identifies the grounding line, it does not show how much ice is moving across it; to determine that we need to collect ice thickness measurements. For today’s flight we moved just inland of the grounding line for about half of the Ronne Ice Shelf collecting ice thickness and other supporting data that will begin to fill in this important information.
Reference: Hellmer, H. H. et al. Nature, 2012. DOI:10.1038/nature11064.
For more on the IceBridge project visit: