November 25, 2014Underwater robot provides first detailed, high-resolution 3D maps of Antarctic sea ice

The SeaBED AUV mapping a previously-inaccessible area under the Antarctic sea ice (Photo: Klaus Meiners/Woods Hole Oceanographic Institution)

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Antarctic scientists have combined measurements provided by an underwater robot with existing satellite data to show that Antarctic sea ice may be thicker than previously thought. Their first-of-a-kind high-resolution 3D maps cover over 500,000 square meters (5.4 million sq ft) in the Weddell, Bellingshausen, and Wilkes Land sectors of Antarctica, and they reveal heavy deformation in all three near-coastal regions that produces mean sea-ice draft (thickness of the submerged part of the ice) far in excess of ice drilling and ship-based measurements. This is a big leap forward in our ability to understand why and how the ice is changing on both small and large scales.

The 2-m (6 ft) long, 200 kg (440 lb) SeaBED autonomous underwater vehicle (AUV) swam 20-30 m (65-100 ft) below the ice to previously-inaccessible areas on two separate expeditions, first in 2010 and then again in 2012. It moved in a "lawnmower" grid pattern at a rate of around 30 cm/s (12 in/s) as it mapped the complex topography of the underside of the ice in 400 by 400 meter (1,312 by 1,312 ft) chunks, with multi-beam (and upward-pointing) sonar that was compiled and converted into 3D maps of the surface beneath the ice floes.

These maps reveal large variability in ice thickness, more akin to inverted mountain ranges than the undulating plains you might expect. The mean thickness ranged from 1.4 to 5.5 m (4.6-18 ft), with the thickest point measuring 16 meters (52.5 ft) and an average of 76 percent of the ice volume displaying deformity.

SeaBED was able to map the ice thickness at a resolution of better than 25 cm (10 in), which co-lead author Dr Guy Williams said enabled the research team "to discriminate individual ridge keels and rafted ice blocks." It wasn't easy to create the robot, though.

"Putting an AUV together to map the underside of sea ice is challenging from a software, navigation and acoustic communications standpoint," explained Hanumant Singh, an engineering scientist at the Woods Hole Oceanographic Institution whose lab designed, built, and operated the AUV. "SeaBED's maneuverability 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 [autonomous underwater] vehicles."

Sea ice thickness is normally measured using a "point-based" method of drilling hundreds of holes, which is a labor-intensive and season-dependent endeavor, or through estimates via satellite and nearby ships – both of which are complicated by snow cover on the ice. But Williams likens these old methods to diagnosing a patient by prodding their skin.

None provide anything like the detail or reliability of the SeaBED maps, which could now make it possible to look deeply at the differences between Arctic and Antarctic sea ice and to vastly improve our understanding of the mechanisms that drive climate patterns and marine life in the region.

The scientists will now do surveys on a larger scale. "The AUV missions have given us a real insight into the nature of Antarctic sea ice – like looking through a microscope," said co-author Jeremy Wilkinson. "We can now measure ice in far greater detail and we're excited to measure ice up to 17 meters thick."

You can watch a video below of Williams explaining how and why Antarctic sea ice is being mapped.

A paper describing the research was published in the journal Nature Geoscience.

水下机器人首次提供详细的3D高分辨率南极海冰地图

Underwater机器人提供的南极海ice一次详细的，高分辨率的3D地图

海底水下机器人测绘南极海冰在先前不能访问的区域（图文：克劳斯·迈纳斯

伍兹霍尔海洋学研究所）

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南极的科学家通过一个水下机器人与现有的卫星提供的数据相结合的测量表明，南极海冰可以更厚比以前认为的。 - 第一的一类高清晰度的3D地图覆盖超过50万平方米（540万平方英尺）在南极威德尔海，林斯高晋和威尔克斯地部门，他们揭示了所有三个近岸地区重变形的生产平均海冰草案（冰的水下部分的厚度）远远超过冰钻和舰载测量。这是一个大的飞跃在我们理解为什么以及如何冰变化对小型和大尺度的能力。

的2米（6英尺）长，200千克（440磅）的海底自治水下车辆（AUV）游20-30米（65-100英尺）的冰层下面以前无法进入的地区在两个独立的远征，首先在2010年，然后又在2012年它移动在“割草机”格子图案的速率约30厘米

秒，因为它映射到的复杂地形400的冰的下侧的由400米（1312通过1312英尺）的块，具有多波束（和向上指向）声纳（在

秒12），其被编译并转换成浮冰下表面的三维地图。

这些地图显示很大的变化在冰厚，更像是比你想象的起伏的平原倒山脉。从1.4的平均厚度范围为5.5米（4.6-18英尺），最厚点测量16米（52.5英尺），平均的冰量显示畸形的76％。

海底是能够映射冰厚，分辨率为更好的超过25厘米（10英寸），其共同第一作者盖伊·威廉姆斯博士说，使研究小组“来区分各个脊形龙骨及筏冰块。”这是不容易创造机器人，虽然。

“将一个水下机器人一起绘制海冰的底部是由一个软件，导航和声通讯的角度看挑战，解释说：”Hanumant辛格，一个工程科学家伍兹霍尔海洋研究所的实验室设计，建造和操作的水下机器人。 “海底的操纵性和稳定性使得它适合这种应用，我们正在做详细的浮冰比例尺制图和部署，以及回收的紧密堆积冰情。这本来是很难做到很多我们做的任务，特别是在的情况下，我们遇到了一些较大的[自治水下autonomous underwater，或经由卫星和附近的船只估计 - 这两者都对冰并发积雪。但威廉姆斯比喻这些老方法来通过督促他们的皮肤诊断病人。

没有提供像海底地图的细节或可靠性，现在可以使人们有可能深入看看北极和南极海洋之间的差异什么冰，极大地提高我们驱动的气候模式和海洋生物在该区域机制的理解。

科学家们现在将做较大规模的调查。 “水下机器人的任务给了我们真正体会到南极海冰的性质 - 喜欢看通过显微镜，说：”合着者杰里米·威尔金森。 “我们现在可以在更多的细节测量冰和我们很高兴能测量冰达17米厚。”

你可以看威廉姆斯解释如何和为什么南极海冰被映射下面的视频。

A纸描述研究结果发表在自然杂志地球科学