Robot Sub Finds Surprisingly Thick Antarctic Sea Ice

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 global 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 driving 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 is 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 lead, 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 international group of researchers has mapped the bottom of sea ice with an underwater robot, or autonomous underwater vehicle (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.

"With the AUV, you can get under ice that is either difficult to access or difficult to drill, and in each region, we found some really thick ice, thicker than had been measured anywhere else," Maksym said.

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. [50 Amazing Facts About Antarctica]

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.

Next steps 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.

More From LiveScience:

Images of Melt: Earth's Vanishing Ice What Does Record-High Antarctic Sea Ice Say About Climate Change? | Video Images: One-of-a-Kind Places on Earth Originally published on Live Science.

Copyright 2014 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Different thicknesses of sea ice in Antarctica's Bellingshausen Sea. Open water is dark black; older sea ice has a covering of bright white snow, and thick ice is grey.

July 23, 2012 --

This week Google debuted a new set of panoramic images from the South Pole. Taken in partnership with on-site researchers from the University of Minnesota’s Polar Geospatial Center, these interactive views shed light on remote locations such as Ernest Shackleton’s early shelter and the Adélie penguin rookery. The images were captured using off-the-shelf equipment that included a digital SLR camera with a fisheye lens, said Alex Starns, a Google technical program manager for Street View whose work covers operations in Asia Pacific and Antarctica. Brad Harried, a researcher with the Polar Geospatial Center, took the latest photos. “Brad would often carry extra batteries in his pocket and use a chemical hand warmer to keep them from freezing,” Starns said. “It’s a little challenging to operate the camera wearing thick winter clothes and mittens.” Explore the frigid Antarctic landscape in this slide show of high-resolution images.

The South Pole Telescope building shown here contains an enormous scientific instrument that took more than 30 engineers and scientists to construct. “The South Pole Station is actually at a really high altitude,” Starns said. Located 1.7 miles above sea level, the telescope is used by a team of scientists seeking to answer crucial questions such as “How old is the universe?” Since the South Pole has such clear atmosphere, it’s an ideal location for observing the thermal radiation that fills our universe. Starns hopes that Street View users who interact with the new images from Antarctica will be excited to learn more about the continent. He also wants them to have a greater appreciation for the explorers of 100 years ago and modern researchers, he said. Particularly the challenges inherent in a place NASA scientists used to prepare the landers for conditions on Mars. ANALYSIS: 100 Years Ago Today: Scott Reaches South Pole

Anglo-Irish explorer Ernest Shackleton survived what seemed like certain death. His first attempt to reach the South Pole in 1901 nearly killed him. In 1908 he returned, getting even closer to the South Pole. Although Norwegian explorer Roald Amundsen got there first in 1911, Shackleton was still determined. His ship Endurance would get trapped in the ice, forcing the crew on an epic adventure to safety. New images show the entire interior of Shackleton’s 1908 hut at Cape Royds. “Having this immersive imagery of the supply depot they built really reinforces the sense of just how incredible that journey was,” Starns said. Reading materials remain on the beds, tossed aside as if their owners will be back momentarily. And yet the objects inside hut have stayed in place for more than a century. “His

was unique because they had some early photographic equipment on board,” Starns said of Shackleton. “In the hut you can still see some of the photographic chemicals that they used to develop their film.” Photographer Frank Hurley’s images from the Endurance expedition would become famous. HOWSTUFFWORKS: Can You Vacation in Antarctica?

A 50-foot-long wooden cabin was built in 1911 at Cape Evans on Ross Island to house several dozen men. British explorer Robert Falcon Scott used this building as a base for his Terra Nova expedition to the South Pole, but he and his team ultimately reached the pole weeks after Amundsen. Scott and the four other men in his party died in the frozen wilderness while attempting to return. A letter found with his body read, "Had we lived, I should have had a tale to tell of the hardihood, endurance, and courage of my companions which would have stirred the heart of every Englishman." Although the cabin has remained largely unchanged since Shackleton locked it up in 1917, scientists have to regularly keep it from being swallowed by ice and snow. "You look at the food and the equipment that they brought and imagine how isolating and how lonely it must have been down there," Starns said, adding that he couldn’t imagine spending years eating tea biscuits and gravy. "It’s amazing to me that not only did these men do this, but many of them volunteered for it." NEWS: Two Aussies Reach South Pole Unaided

Back in 2010, Google first unveiled Street View images taken from Half Moon Island on the northern edge of the Antarctic Peninsula. Visitors from cruise ships that stopped there helped take the panoramic photos at the time, Starns said. Instead of a human, the Street View icon turned into a little penguin. The Adélie penguins at a remote rookery on Cape Royds aren’t accustomed to humans taking their pictures, but they seem more focused on soaking up the summer sun. From here the waters of McMurdo Sound are visible. Adélie penguins use the sun to navigate from land to the sea, according to scientific data from the Polar Conservation Organization. Unlike the humans in Google’s shots, none of the penguins have blurred faces to protect their identities. “If we get any blurring requests from them, we’ll be sure to tend to them,” Starns joked. ANALYSIS: Paralyzed Athlete Sit-Skis to the South Pole

Flags from the nations that signed the Antarctic Treaty encircle the Ceremonial South Pole. In 1959 the original treaty among 12 nations included provisions stating that Antarctica would only be used for peaceful purposes and ensuring continued scientific research there. Since then, the list of signatories has grown to 50. Besides flags, the Ceremonial South Pole is marked by a pedestal with a reflective globe on top. In the background stands the Amundsen-Scott South Pole Station, an American scientific facility. When the Google panoramic images were shot on the polar plateau, the conditions weren’t just windy -- the temperature was negative 60 degrees F. The ice that the station is built on moves annually so the geographic South Pole location is in a different position every year, Starns said. "The ceremonial pole always stays in the same place." VIDEO: Frozen Planet: Journey to the South Pole