The international team, led by NASA's emeritus glaciologist Robert Bindschadler and funded by the National Science Foundation and NASA, had to abort their mission in 2007 due to logistical challenges after becoming the first people to ever land on the ice shelf.
Drilling station and remote field camp on the Pine Island Glacier in 2012. Image Credit: Salvatore Consalvi
On their next try, in 2011, bad weather prevented the scientists from reaching the ice shelf until it was too late in the field season to carry out their science. It wasn't until December 2012 that the team was finally able to install scientific instruments.
Those measurements taken on and below the Pine Island Glacier ice shelf have yielded their first scientific results, determining the rate at which warm sea water is eating away the ice from underneath the floating portion of the glacier.
In a paper published in the journal Science on Sept. 13, the team describes how at one of their study sites, halfway down the ice shelf, the melt rate was as high as 2.36 inches (6 centimeters) per day.
"This is the first observation of the actual melt rate underneath the ice shelf," said Timothy Stanton, an oceanographer at the Naval Postgraduate School in Monterey, Calif., and lead author of the paper. "We have observations using remote sensing of various kinds, but these are actual in situ measurements."
The measurements also detected differences in melt rates across the channel system that runs underneath the ice shelf, Stanton said. Such features are important for adjusting models so they can accurately predict ice melt and its contribution to sea level rise.
“Our direct measurements are consistent with the larger scale averages that remote sensing data have provided, but our data capture an enormous fine scale variability of the basal melting rate that remote sensing can't resolve,” Bindschadler said. “Using only the average melt rates would not lead to a correct understanding of the actual ocean-ice interaction processes taking place in the boundary layer.”
Ice shelves buttress seaward glaciers, slowing the speed at which these rivers of ice dump their contents into the sea. If an ice shelf is weakened at its grounding line, the point where the glacier loses its grip on the land and starts floating, it allows the ice to flow faster, which impacts sea level. Pine Island Glacier and its neighbor, Thwaites Glacier, drain a large fraction of the West Antarctic ice shelf and are of great importance to its stability.
Research shows that melting of the underside of Antarctic ice shelves is ultimately driven by changes in the southernmost atmospheric circulation. Strong westerly winds push the frigid top water layer of the Southern Ocean away from land, which allows deeper, warmer water to raise and spill over the border of the Antarctic continental shelf. Since the weight of land ice tilts the continental shelf inland, streams of warm water can travel all the way to the ice shelf's grounding line, where they melt the ice. The resulting warm, fresh melt water rises against the underside of the ice shelf along the length of the ice shelf and carves melt channels that look like inverted river valleys.
To study the melt rates within these channels and observe the ocean cavity beneath the ice shelf, the team set up three study sites on the ice shelf during December 2012 and January 2013. All three camps, named Drill A, B and C, were in the middle of the ice shelf, to avoid the sides and the grounding line -- all of them heavily crevassed areas.
At the three campsites, the researchers used a hot-water drill to penetrate the 1,460-foot (450-meter) thick ice shelf. They then lowered through the holes a suite of oceanographic instruments, developed by Stanton, to measure the physical properties of the seawater beneath. At each drill site, a rigid pole allowed to refreeze in the lower ice shelf suspended a set of instruments about 6 feet (2 meters) below the ice-shelf base. The team also deployed at each site profiling instruments and a deep temperature and salinity instrument designed to repeatedly scan the deeper waters, although mechanical and hydraulic problems greatly limited data yield from the profilers.
Researchers use the data from these two instrument packages under the ice shelf to measure the basal melt in two different ways. First, an upward-facing altimeter records the retreat of the ice from the instrument. Second, an ocean turbulence instrument measures very small fluctuations in temperature, salinity and vertical current right below the ice. Researchers then use these three parameters to study changes in the vertical transport in the water column due to melt, which in turn lets them calculate the local ice melt rate.
On the ice shelf, scientists left high-resolution radars at different sites for 24 hours, and measured how the sea-ice interface, or the point where water touches the ice shelf's underbelly, moved as the ice melted.
The radar and oceanographic measurements translated into very similar melt rates: 2.36 inches (6 centimeters) per day, or about 72 feet (22 meters) per year in the middle of the channels, and almost non-existent at their flanks. The authors calculate that melting at the grounding line possibly doubles that higher rate. This would agree with previous estimates of basal melt made by a team led by Eric Rignot, jointly of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the University of California, Irvine. In 2002, Rignot's group used satellite radar data and calculated that the warm marine waters were melting Pine Island Glacier's ice shelf at around 144 feet (44 meters) per year at its grounding line.
For decades, Pine Island Glacier was considered too dangerous and remote to explore, despite its scientific interest. But a careful study of satellite imagery by Bindschadler identified an area where planes could land safely.
"The success of this project shows the strength of marrying satellite data with field data," Bindschadler said. "The satellite data told us where to go, helped guide us and it told us in broad brush strokes that this part of West Antarctica was changing a lot. But field work was the only way to get these measurements underneath the ice shelf; satellites couldn't do that for us."
"In my 35 years doing fairly large oceanographic projects, the Pine Island Glacier one tops it in terms of its complexity and challenge," Stanton said. "But it's clear that it's very important to understand how these massive ice shelves are influenced by changes in the ocean. These observations will provide the basis for improving global climate models."Maria-José Viñas
Maria-José Viñas | EurekAlert!
Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy