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Dec. 11, 2014

Picture of the Week: Underwater Robot

by Julie Leibach

Click to enlarge images
That square suspended in an azure abyss is a pioneering robot. Over the course of two Antarctic expeditions in three seas, the autonomous underwater vehicle used sonar to gather data on ice floes. From that data, a team of scientists generated the first detailed, 3-D maps of sea ice thickness in Antarctica, reporting their results last month in Nature Geoscience.
 
The robot is one of a “family” of robots called SeaBED, originally built to study the sea floor. But for two missions—one in 2010 and another in 2012—researchers turned its sensors upwards to scan 10 different ice floes drifting in the Bellingshausen and Weddell Seas in West Antarctica, and off Wilkes Land in East Antarctica.
 
Climate models suggest that as sea ice shrinks or grows in breadth, its thickness should change, too. “If we get a picture of both the extent and the thickness, then we are really looking at how the ice interacts with climate—responds to climate change—in two different ways,” says Ted Maksym, a sea ice scientist at Woods Hole Oceanographic Institution and one of the study’s co-authors. “It gives us a much deeper understanding of what's going on and helps us understand whether our climate models are working properly or not.”
 
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Scientists have a fairly good gauge on the extent of sea ice in Antarctica, thanks to 30 years of data from satellites. “But these satellites—they really only see the surface,” says Maksym. “You don't get any idea of what's going on in three dimensions.” Drilling, on the other hand, provides measurements on ice thickness, but it results in only a few hundred datapoints at a time. Meanwhile, SeaBED “will map an area the size of a couple of football fields, and you get tens of thousands of points, actually, of ice thickness,” says Maksym. “It's a much, much richer data set.” 
 
The data that SeaBED collected enabled a good look at what lies beneath—and it wasn’t what the scientists expected: The sea ice in the regions the robot explored was thicker than what measurements from drilling and ship-based estimates have indicated. Indeed, historical data suggest an average thickness of about a meter, but SeaBED revealed averages ranging from 1.4-5.5 meters. “When we first saw the data, it was pretty puzzling,” says Hanumant Singh, a scientist at Woods Hole Oceanographic Institution, who developed the robot. 
 
The disparity might be because of sampling bias. Maneuvering ships—even icebreakers—into areas of thick ice in order to take measurements is difficult. Further, “for the very thickest floes, it’s very challenging to drill through them, so we’ve probably been avoiding those,” says Maksym. "It’s not that [thick sea ice] wasn't there before, it’s just we couldn’t access it very easily,” he says.

SeaBED can only take scientists so far, however. The robot, which is about the size of a motorcycle, can travel 10 kilometers before coming up for air (so to speak). At its maximum, however, Antarctic sea ice covers an area the size of North America.

The researchers envision using underwater robots built for longer hauls that will survey larger areas of sea ice thickness. Eventually, they can use those surveys to calibrate readings taken from above by satellites. Indeed, newer satellites can measure the height of sea ice above the surface, but snow interferes with making accurate estimates about ice thickness. “By looking at the top and the bottom [of sea ice] at the same time, you can get a much better picture of what the satellite is actually seeing from space, and you can convert those space-borne measurements into a thickness more accurately,” says Maksym.

The team is already working on the next generation of SeaBED, which will be able to travel 100 kilometers on one trip. It's slated for a maiden voyage to the Arctic in October 2015.

 

About Julie Leibach

Julie is the managing editor of ScienceFriday.com. She is a huge fan of sleep and chocolate. Follow her @julieleibach.

The views expressed are those of the author and are not necessarily those of Science Friday.
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line 2: sub doEval { 
line 3: 	my($parent);
line 4: 	
line 5: 	if($LayoutManager::url_resolved_values{'SEGMENT.nickname'}) {
line 6: 		$parent = $LayoutManager::url_resolved_values{'SEGMENT.nickname'};
line 7: 	}
line 8: 	elsif($LayoutManager::url_resolved_values{'VIDEO.nickname'}) {
line 9: 		$parent = $LayoutManager::url_resolved_values{'VIDEO.nickname'};
line 10: 	}
line 11: 	elsif($LayoutManager::url_resolved_values{'DOCUMENT.nickname'}) {
line 12: 		$parent = $LayoutManager::url_resolved_values{'DOCUMENT.nickname'}
line 13: 	}
line 14: 	
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line 16: 		my(@books) = &Database::SelectClause('BOOK',"parent = $parent");
line 17: 		if(!@books) {
line 18: 			$parent = '';
line 19: 		}
line 20: 	}
line 21: 	
line 22: 	if(!$parent) {
line 23: 		my(@sel) = &Database::SelectClause('GLOBAL','record all ""');
line 24: 		if(@sel) {
line 25: 			$parent = 'GLOBAL.' . $sel[0];
line 26: 		}
line 27: 			$main::ENV{'reading_header'} = "FEATURED READING";
line 28: 	}
line 29: 	
line 30: 	 = '';
line 31: 	
line 32: 	if($parent) {
line 33: 		my(@books) = &Database::SelectClause('BOOK',"parent = $parent");
line 34: 		0 = 0;
line 35: 		my $dots;
line 36: 		foreach(@books) {
line 37: 			my(%data);
line 38: 			&Database::GetRow($_,'BOOK',\%data);
line 39: 			my($status,$title,$author,$url,$image,$width,$height) = &SciFri::Schema::getAmazonItem($data{'isbn'});
line 40: 			if($data{'title'}) {
line 41: 				$title = $data{'title'};
line 42: 			}
line 43: 			if($data{'author'}) {
line 44: 				$author = $data{'author'};
line 45: 			}
line 46: 			if($status eq 'ok') {
line 47: 				 .= "<div class=\"box-2x1-item box-slide\" data-href=\"$url\">";
line 48: 				 .= "	<div class=\"box-2x1-item-photo\">";
line 49: 				 .= "		<div class=\"image-wrapper\" data-jsclass=\"imageWrapper\" data-align=\"right\">";
line 50: 				 .= "			<img src=\"$image\" data-width=\"$width\" data-height=\"$height\">";
line 51: 				 .= "		</div>";
line 52: 				 .= "	</div>";
line 53: 				 .= "	<h4>$title</h4>";
line 54: 				if($author) {
line 55: 					 .= "	<p>by $author</p>";
line 56: 				}
line 57: 				 .= "	<div class=\"box-2x1-more-button\"><a href=\"$url\"><img src=\"/images/v1/icon_text_more_white.png\" width=47 height=15 border=0></a></div>";
line 58: 				 .= "</div>";
line 59: 				++0;
line 60: 			}
line 61: 		}
line 62: 	}
line 63: 	if($parent eq "GLOBAL.1") { $main::ENV{'reading_header'} = "FEATURED READING"; }
line 64: 	else { $main::ENV{'reading_header'} = "RELATED READING"; }
line 65:  };
line 66: &doEval();
line 67: 1;

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