Science of the Ross Ice Shelf
Antarctica’s Ross Ice Shelf is enormous in size, covering 487,000 sq. km – the size of France – and has a thickness ranging from a few hundred metres near the sea to over 1,200 metres away from the floating edge. The edge of the ice shelf along the Ross Sea is a wall of ice towering over the water by as much as 50 metres, the majority of the ice below the waterline.
The Ross Ice Shelf is being fed a constant flow of ice from glaciers draining from both the East and West Antarctic Ice Sheets. As new ice is added existing ice is being removed through melting at the base and ice calving at the front. The Ross Ice Shelf plays an important role in stabilising the Antarctic ice sheet, buttressing the ice that is constantly moving over the land surface.
Science of the Ross Ice Shelf
One of the main studies being conducted on learning more about the Ross Ice Shelf is the (the Ross Ocean and ice Shelf Environment and Tectonic setting Through Aerogeophysical surveys and modelling), which is a large multidisciplinary and multi-institutional project that aims to advance our understanding of the dynamics of the ice shelf system. To accomplish this ROSETTA researchers will collect new high-resolution data that will determine the thickness and structure of the Ross Ice Shelf and characterise the bedrock and seabed bathymetry under the ice shelf. The ROSETTA surveys will also acquire magnetics and gravity data for geological interpretations and radar, LiDAR and imagery for the mapping of the Ross Ice Shelf including crevasses and channels, debris and the distribution of marine ice and accumulation.
ROSETTA’s overall aims
Overall, ROSETTA will focus on three areas:
- Understanding the ice (ice moves into and across the shelf at a range of speeds from 200-1000 metres/year, taking between 500 and 1,000 years to travel from where it first goes afloat to where it ends at the calving edge);
- Understanding the underlying bed (the bed structure beneath the ice shelf influences the ocean circulation below);
- Understanding more the ocean (general ocean circulation, tidal currents and the overall mixing in the Ross Sea embayment including beneath the ice shelf are sensitive to the geology below as well as changes in the ice shelf extent and thickness below the ice surface).
Modelling the ice below
In a recent study, scientists from Lamont-Doherty Earth Observatory, Scripps Institution of Oceanography and the United States Geological Survey flew over the Ross Ice Shelf, using the IcePod, which is an array of radars and other instruments attached to the fuselage of a C-130, to study how the ice, ocean and underlying land interact. The ROSETTA project has to data completed 18 survey lines and 4 tie lines from a total of nine flights, producing over 16,000 line kilometre of data.
In November of last year, they provided a range of LiDAR (Light Detection and Ranging) images provided by the IcePod. During the flight the IcePod is lowered to collect data with the LiDAR instrument sending out light pulses to illuminate the area below. The time is then measured for the reflected light to return enabling computer software to create three dimensional images of the land surface.
New maps of the sea floor
As part of the ROSETTA project, scientists from New Zealand’s GNS Science in November of this year will spend up to six hours per day in a C-130 flying above the Ross Ice Shelf. With a GNS Science-owned and operated gravity meter, the data gathered will help GNS Science created a new map of the sea floor bathymetry under the ice shelf. In fact, the new map will have 25-times better resolution than the 30-year old map it will be replacing.
GNS Science is participating in this project due to its vast experience in airborne geophysical surveying, having completed an updated airborne gravity survey for New Zealand. The GNS Science gravity meter being used as part of the study is about the size of a washing machine and can accurately measure small changes in gravity caused by undulations in the sea floor.
Reconstructing the ice shelf’s history
Meanwhile, University of Otago-led scientists embarked on an expedition to conduct acoustic-based imaging of the seafloor and its sediment layers in the Ross Ice Shelf. Over the next three years, the researchers will also use a hot water drill built at Victoria University of Wellington to bore through the ice to observe the ice/ocean interface directly, measure ocean properties and sample sediments on the sea floor. With the data the scientists will be able to reconstruct the Ross Ice Shelf’s history since the last ice age.
ANDRILL discovering strange creatures
In a recent study, National Science Foundation (NSF)-funded researchers from the University of Nebraska-Lincoln discovered a new species of small sea anemones burrowed into the underside of the Ross Ice Shelf, with their tentacles stretching out into the cold freezing water from a ceiling. In fact the team found thousands of these small creatures living upside down, hanging from the ice, in contrast to anemones that usually live on the sea floor.
These little white anemones have been named Edwardsiella andrillae in honour of the ANDRILL Program (ANtartic geological DRILLing, which is a multinational collaboration of more than 200 scientists, students and educators from German, Italy, New Zealand, the United Kingdom and the United States that aims to recover stratigraphic records from the Antarctic margin. The objective is to drill back in time to recover a history of paleoenvironmental changes).
The anemones found are less than an inch long in their contracted state but can stretch out three to four times longer in their relaxed state and have between 20 and 24 tentacles, an inner ring of eight longer tentacles and an outer ring of 12 to 16 tentacles. Scott Borg, head of the Antarctic Science Section of NSF’s Division of Polar Programs noted that the discovery reveals just how much remains both unknown and unexplored by scientists even after more than 50 years of active research on the continent.
Upside down fish
This discovery was made after scientists had lowered a 4.5-foot cylinder equipped with two cameras, side-mounted lateral camera and a forward-looking camera, into a drilling hole bored through the 270-metre-thick Ross Ice Shelf for the purpose of learning more about the ocean currents beneath the ice shelf. In addition to the anemones, the scientists saw fish that routinely swam upside down, the ice shelf serving as the floor of their world as well as polychaete worms, amphipods as well as an odd-looking creature dubbed the ‘egg roll’, a four-inch-long, one-inch-diameter, neutrally buoyant cylinder seen bumping along the field of sea anemones and at times hanging onto them.
Analysing the creatures
To learn more about the anemones, the team stunned the creatures with hot water and used an improvised suction device to retrieve the animals from their burrows for transportation to McMurdo Station for preservation and further study. From their scientists will attempt to answer a variety of questions including how do they survive without freezing, how do they reproduce and what exactly do they eat. To understand more about the anemones the scientists are proposing to use a robot capable of exploring deep in the ocean and further from the access hole drilled into the ice.
