Image of the Day
Successful Sediment Sampling!
WISSARD science progress continues! Dr. Reed Scherer examines a core from the multicorer. A variety of sediment samplers are for recovering different types of sediment mainly based on their stiffness. Soft sediments are usually collected using short cores with wide barrels that do not disturb the sediment-water interface. Corers with deeper penetration usually encounter sediment with increasing stiffness and therefore need greater weight or other features, such as vibration or rotation to enable deeper penetration.
The percussion corer is designed to be lowered to the lake or sea floor on the smart cable of the multipurpose winch, and then to hammer a core barrel up to 5m-long into stiff over-consolidated sediment such as subglacial till.
The multicorer is a lightly modified off-the-shelf system designed by the Austrian Uwitech Company that is well-tried in many lakes around the world. It is designed to take three replicate cores at the one time after self-triggering on striking the bottom sediment during descent.
See the Scientific American article, Scientists Drill through 2,400 Feet of Antarctic Ice for Climate Clues.
WISSARD Update
January 19th, 2015
Last day of WISSARD science operations in the borehole. The last science instruments were deployed today, and operations end at midnight. There were 3 deployments of the gravity corer with 3 cores resulting. The string of geophysical sensors for long-term observations in the ice and ocean is being monitored as it freezes in. Over 1000 lbs of samples have been prepared to retro back to McMurdo on the next flight on Jan 21. WOW! If conditions allow, 20 of the 40 personnel in the field will return to McMurdo tomorrow afternoon.
January 16th, 2015
Successful science collection on all fronts continues! All of camp is in good spirits and moving through the last science days that focus on longer-term deployments in the boreholes, lab work and packing-up. Our support team continues to work diligently to ensure smooth operations around camp, helping to prepared for samples and some equipment for shipping back to McMurdo.Science groups continue to prepare their retrograde cargo and samples. A visit from videographer Ralph Maestas insures much of the sampling and science was caught on film, and WISSARD is grateful for his involvement! The drill team completed the reaming of a 3rd borehole and a string of geophysical sensors for long-term observations in the ice and ocean cavity was successfully deployed. Excellent work by the drill team from the University of Nebraska-Lincoln, extended the number of days the scientists could collect data from a planned seven or eight days to more than ten, which has increased the amount of science completed exponentially. More time is always an invaluable resource in Antarctic Science! On the 15th, ice coring continued in a second borehole and the drill reached about 750m depth recovering what looked like the transition between meteoric and accreted ice. To date, the multi-corer was deployed to sample sediment, and it has collected at least 8 good cores. In addition, two good cores, each about 65cm long, were recovered using the gravity corer. Water sampling has been successful and comprehensive, with the deployment of the Niskin sampling system as well as an in-situ filtration system deployed by Louisiana State University. The POP (Physical Oceanographic Package) an additional muti-faceted water sampling tool, was also successfully deployed overnight and through the day through most of a tidal cycle. It was stationed at different levels in the water column and did some profiles through the seawater column. Data collected included measurements of water salinity,temperature, velocity, suspended sediment concentration and particle size, and CO2 and CH4 concentrations. Additionally 5 1-liter, samples of the seawater were collected to calibrate and verify the instrumental measurements. This is a very exciting sampling success! The smart winch was repaired in the field, which also allowed for the deployment of the ROV Deep-SCINI. Deep-SCINI (Submersible Capable of under-Ice Navigation and Imaging) is a remotely operated vehicle (ROV), which was designed and built at the University of Nebraska-Lincoln as part of a related NASA project, and based on previous SCINI models funded by NSF. This ROV provided some spectacular images of the borehole during its descent in the afternoon. They showed the internal ice structure and significant sedimentary debris within. SCINI then provided the first extensive imagery of this type of environment during its roving through the seawater cavity. The imagery also provided important information on ice, marine and sedimentary processes that confirm what we have inferred from our as yet cursory descriptions of the sediment cores.Video from Deep-SCINI is forthcoming and apparently amazing! Today the geothermal probe will be deployed again following a successful deployment previously, and another water collection with the Niskin and sediment sample with the multicorer are planned. The scientists are tired but fired up about the successes in the field. GO WISSARD!
WISSARD Project Overview
Subglacial Aquatic Environments
Over the last several decades, by using ground penetrating radar and other remote sensing tools, scientists have discovered that under the massive Antarctic ice sheets there lies a vast hydrological system of liquid water. This water exists because geothermal heat flow from below, coupled with pressure, movement, and the insulating nature of the ice sheet above, is great enough to maintain some areas at the base of the ice sheet above the freezing point, even in the extreme cold of Antarctica. In topographic depressions there are hundreds of lakes, both large and small; some are isolated, but many are interconnected by water channels and large areas of saturated sediments, the water eventually running out into the Southern Ocean as the ice sheet becomes a floating ice shelf.
WISSARD
In order to explore one of these hydrological systems at the margin of the West Antarctic Ice Sheet, we have organized an interdisciplinary project to access the subglacial environment. The Whillans Ice Stream Subglacial Access Research Drilling project (WISSARD) is using a variety of tools and techniques to explore Subglacial Lake Whillans and the nearby grounding zone, on the southeastern edge of the Ross Sea. Radar and seismic equipment is used to profile the overlying ice sheet and the underlying water, sediments, and rock, while GPS stations accurately track ice movement.
This season our target is the grounding zone, where the massive West Antarctic Ice Sheet atop land meets the Ross Sea. This area is considered an important piece of the puzzle for our scientists interested in ice sheet dynamics. The work will help scientists assess the stability of the West Antarctic Ice Sheet, most of which sits below sea level. It is the last ice sheet on Earth resting in a deep marine basin and is the most likely player in any future, rapid sea-level rise. If the grounding zone is retreating or primed to retreat, rapid changes in ice behavior could follow over the next century. Work focused on microbial life, biogeochemical cycling, and surrounding geophysical surveys will also continue during the 2014-2015 season.
Our intentions are to have 8 days of science in the primary borehole at the Grounding Zone location mid-January. We will deploy all of the WISSARD tools during this period and recover sediment and water samples from the water cavity some 750 meters below the surface of the ice. We also hope to recover about 5 meters of basal ice cores at another borehole very near the primary hole. Image: Rachel Xidis/NIU.
