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Dispatch 4: Into the Ice

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Joey Wenig

September 24, 2014


Because it is an icebreaking ship, the Louis is designed to have a rounded hull. This feature enables it to ride up on ice floes in its path and crush down through them using gravity. All well and good when you’re breaking ice, but the flip side of the rounded hull is that it increases the rolling response of the boat to even small amounts of swell when in open water, as we have been the past three days. I can’t say for sure, but I think I woke up almost instantly when we first hit ice around 5 AM this morning. Not only did the motion of the ship change completely (going from the familiar mellow side-to-side roll, to a jerky stop and start, with lengthwise vertical motion thrown in, like a teeter totter) but also the sound was unmistakable, not to mention — particularly for those with cabins closer to the bow of the boat, like Sam Thomas — deafening.

While reaching ice-bound seas may have severely disturbed Sam’s sleep, he was still ecstatic to see the change of scenery. Hailing from London, UK, where he’s a PhD candidate at University College London, Sam is here with Alek Petty of NOAA/University of Maryland to observe the ice. Sam and Alek have both studied Arctic sea ice using remotely sensed data, but this is their first time seeing the object of their research firsthand. In comparison with the advanced technology of the satellites they are familiar with, the technique for collecting data they’ll be using on board ship is downright primitive (but nonetheless effective). They’ve mounted a camera on the bridge (upper deck where the steerage is located) facing down along the side of the ship. As the Louis breaks through the ice, large chunks are crumpled and pushed alongside the boat such that a cross section of the floe frequently comes into view. The camera, constantly recording video footage, captures these cross sections. Sam and Alek have also mounted a stick with colored gradations (see photo) in the foreground of the camera’s view. By extracting still images from the recorded video, they are able to measure the thickness of the ice through which the Louis is passing by using the stick for scale against the cross sections of the churned-up ice chunks. Like I say, not exactly a satellite measuring ice thickness from outer space, but the technique has its benefits: it requires no specifically allotted ship time, since it is operating whenever the ship is in transit—so it’s cheap; and it’s a good way of validating satellite measurements, which are recognized to be imperfect.

Measurements made with the camera-stick apparatus will complement Sam and Alek’s main project on board—making hourly qualitative observations of ice conditions within a one-kilometer radius of the Louis. As ice floes spend more and more time floating about the ocean, they tend to crash into one another. Analogously to tectonic plates forming mountain ranges, compression ridges, sometimes many meters thick, will form as the ice floes raft together. Thus, ice floes that have formed within the past year have a visibly different surface topography than do older, multi-year floes. This characteristic allows rough estimates of ice age to be made on sight, which is exactly what Sam and Alek will be attempting to do in order to further our understanding of an important aspect of change in the Arctic ice pack.

Satellite technology capable of measuring ice extent (which can be thought of as total surface area of sea ice) has been around for a while. In the past five years, however, techniques have begun to be developed for calculating the volume of the ice pack from satellite measurements. Over that period of time, scientists have noticed a shift in the age distribution of sea ice. There is a greater proportion of ice that’s only been around for a single winter than there is of multi-year ice. It’s apparently becoming increasingly difficult for ice floes to ‘survive’ the Arctic summer. Many questions have been asked about the causes of this shift—one hypothesis involves changing circulation patterns in the Beaufort Sea, where we are now—and it is in pursuit of answers to those questions that Sam and Alek have joined this year’s cruise. Their observations will also contribute to improving accuracy of remote-sensing techniques for measuring ice volume, a goal considered hugely important among the polar research community.



Last updated: September 15, 2017
 


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