11/24/14, "Antarctic ice thicker than previously thought, study finds," Oliver Milman, Guardian.com "First of its kind robotic survey of underside of sea ice floes reveals denser ice fringing the continent."
"Groundbreaking 3D mapping of previously inaccessible areas of the Antarctic has found that the sea ice fringing the vast continent is thicker than previous thought.
Two expeditions to Antarctica by scientists from the UK, USA and Australia analysed an area of ice spanning 500,000 metres squared, using a robot known as SeaBed.
The survey discovered ice thickness average between 1.4m and 5.5m, with a maximum ice thickness of 16m. Scientists also discovered that 76% of the mapped ice was ‘deformed’ – meaning that huge slabs of ice have crashed into each other to create larger, denser bodies of ice.
The team behind the research, published in Nature Geoscience, have hailed it as an important breakthrough in better understanding the vast icy wilderness. The findings will provide a starting point to further work to discover how ice thickness, as well as extent, is changing.
Previously, measurements of Antarctic ice thickness were hindered by technological constraints. Ice breaking ships could only go so far into ice to measure depth, while no-one had drilled much more than 5.5m down into the ice to extract a core for analysis.
SeaBed, an autonomous underwater vehicle (or AUV), was used by the research team to analyse ice thickness at an underwater depth of 20 to 30 metres. Driven in a “lawnmower” pattern, the two-metre long robot used upward-looking sonar to measure and map the underside of sea ice floes. Oceanography robots are usually focused on the sea floor.
The mapping took place during two expeditions, in 2010 and 2012, that took researchers to the coastal areas of the Weddell, Bellingshausen, and Wilkes Land regions of Antarctica. The teams came from the British Antarctic Survey, the Institute of Marine and Antarctic Studies in Tasmania and the Woods Hole Oceanographic Institution in the US.
Dr Guy Williams, from IMAS, said the research is an important step in gauging changes to Antarctic ice.
“Sea ice is an important indicator of the polar climate but measuring its thickness has been tricky,” said Williams, the report’s co-author. “Along with the satellite data, it was a bit like taking an X-ray of the ice, although we haven’t X-rayed much of it, just a postage stamp.
“The key thing is that this is a game changer because it was previously very challenging to measure ice depth. We were limited to visual observation from the decks of ships or ice cores and take measures.
“It was a lot of hard work and quite crude, which means we were biased towards thinner ice. It was a bit like a doctor diagnosing a condition by prodding the skin.”
Williams said researchers will now make routine surveys of ice thickness to determine changes over a long period of time. As well as tracking alterations due to climate change, the research will be of interest to marine biologists due to the creatures, such as krill, that inhabit the region.
“This is a big step forward in our knowledge but we’ll need to have longer missions in larger areas,” he said. “What we ultimately want is a team of autonomous robots that self deploy all across the Antarctic, like the spokes in a wheel.”
Hanumant Singh, an engineering scientist at the Woods Hole Oceanographic Institution whose lab designed, built and operated the AUV, said: “Putting an AUV together to map the underside of sea ice is challenging from a software, navigation and acoustic communications standpoint.
“SeaBed’s manoeuvrability and stability made it ideal for this application where we were doing detailed floe-scale mapping and deploying, as well as recovering in close-packed ice conditions.
“It would have been tough to do many of the missions we did, especially under the conditions we encountered, with some of the larger vehicles.”" via Climate Depot
"According to climate models, the region's sea ice should be shrinking each year because of warming. Instead, satellite observations show the ice is expanding, and the continent's sea ice has set new records for the past three winters."...
11/24/14, "Robot Sub Finds Surprisingly Thick Antarctic Sea Ice," by Becky Oskin, Senior Writer, Live Science
"Antarctica's ice paradox has yet another puzzling layer. Not only is the amount of sea ice increasing each year, but an underwater robot now shows the ice is also much thicker than was previously thought, a new study reports.
The discovery adds to the ongoing mystery of Antarctica's expanding sea ice. According to climate models, the region's sea ice should be shrinking each year because of warming. Instead, satellite observations show the ice is expanding, and the continent's sea ice has set new records for the past three winters. At the same time, Antarctica's ice sheet (the glacial ice on land) is melting and retreating.
Measuring sea ice thickness is a crucial step in understanding what's the growth of sea ice, said study co-author Ted Maksym, an oceanographer at the Woods Hole Oceanographic Institution in Massachusetts. Climate scientists need to know if the sea ice expansion also includes underwater thickening. [Album: Stunning Photos of Antarctic Ice]
"If we don't know how much ice is there is, we can't validate the models we use to understand the global climate," Maksym told Live Science. "It looks like there are significant areas of thick ice that are probably not accounted for."
The findings were published today (Nov. 24) in the journal Nature Geoscience.
Like icebergs, much of Antarctica's floating sea ice in underwater, hidden from satellites that track seasonal sea ice. And it's difficult to take direct measurements from ships or drilling, because the thickest ice is also the hardest to reach, Maksym said.
The researchers were stuck aboard an icebreaker in 20-foot-thick (6 meters) pack ice for more than a week after taking advantage of a , or open water, that accessed thick ice, he said. "Obviously that carried some risk, and we were stuck until the wind changed direction again," he said.
Pinging the ice
Over the last four years, the group of researchers has mapped the bottom of sea ice with an underwater robot, or autonomous underwater (AUV), during two research cruises offshore Antarctica. The AUV can swim to a depth of about 100 feet (30 m) and has upward-looking sonar to survey the bottom of the sea ice.icebreaker offshore Antarctica.
Almost all of the sea ice that forms during the Antarctic winter melts during the summer, so scientists had assumed most of the ice never grew very thick. Previous studies suggested the ice was usually 3 to 6 feet (1 to 2 m) thick, with a few rare spots reaching up to 16 feet (5 m) in thickness. For comparison, most of the Arctic sea ice is twice as thick (6 to 9 feet, or 2 to 3 m), with some regions covered with 12 to 15 feet (4 to 5 m) of ice.
The robot sub surveys, which were spot-checked by drilling and shipboard tests, suggest Antarctica's average ice thickness is considerably higher than previous estimates. On average, the thickness of the ice was 4.6 to 18 feet (1.4 to 5.5 m). In the three regions it surveyed, the robot sub found that deformed, thickened ice accounted for at least half of and as much as 76 percent of the total ice volume, the researchers report.
"Our study shows that we're probably missing some of this thick ice, and we need to try to account for that when we try to compare what we see in models and satellites to what we see in the field," Maksym said.
The thickest ice measured during the survey was about 65 feet (20 m) thick, in the Bellingshausen Sea, Maksym told Live Science. In the Weddell Sea, the maximum ice thickness hit more than 45 feet (14 m), and offshore of Wilkes Land, the ice was about 53 feet (16 m) thick.
These thick, craggy floes likely wouldn't exist without the fierce winds that circle Antarctica from west to east, the researchers said. Winter storms bash up the ice, freezing and reforming the rubble into new, thicker ice. "It must have been crunched up a tremendous amount and [the floes] piled up on top of each other," Maksym said. "The ice can generate enormous amounts of force if you have these strong winds. [The wind] is like an accordion, stretching it out and squishing it back together again."
The researchers' next step is to measure how much of Antarctica's total sea ice this thick ice represents. Maksym said it could be a "reasonably significant area of the pack."
The sea ice growth around Antarctica has averaged about 1.2 percent to 1.8 percent per decade between 1979 and 2012, according to the 2013 Intergovernmental Panel on Climate Change's Fifth Assessment Report. The increases are concentrated primarily in the Ross Sea in western Antarctica.
Sea ice in the nearby Bellingshausen and Amundsen seas has significantly decreased. Researchers suspect these regional differences could result from stronger winds or increased meltwater from the Antarctic ice sheet, or a combination of both factors."
11/24/14, "Thick and deformed Antarctic sea ice mapped with autonomous underwater vehicles," Nature Geoscience
"Satellites have documented trends in Antarctic sea-ice extent and its variability for decades, but estimating sea-ice thickness in the Antarctic from remote sensing data remains challenging. In situ observations needed for validation of remote sensing data and sea-ice models are limited; most have been restricted to a few point measurements on selected ice floes, or to visual shipboard estimates. Here we present three-dimensional (3D) floe-scale maps of sea-ice draft for ten floes, compiled from two springtime expeditions by an autonomous underwater vehicle to the near-coastal regions of the Weddell, Bellingshausen, and Wilkes Land sectors of Antarctica. Mean drafts range from 1.4 to 5.5 m, with maxima up to 16 m. We also find that, on average, 76% of the ice volume is deformed ice. Our surveys indicate that the floes are much thicker and more deformed than reported by most drilling and ship-based measurements of Antarctic sea ice. We suggest that thick ice in the near-coastal and interior pack may be under-represented in existing in situ assessments of Antarctic sea ice and hence, on average, Antarctic sea ice may be thicker than previously thought."