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Out to the ice

January 2, 2019

Now fully trained and eager to go, we waited and waited. Weather at our first site alternated between foggy and misty and snowy. But the British Antarctic Survey (BAS) base at Rothera is a bustling place, lots of work and play as well. The team took hikes around the small peninsula, skiing trips, and participated in Quiz Night at the Rothera lounge, part pub and part living room for the entire Rothera staff.

After a week of waiting for suitable weather on the Wilkins Ice Shelf, we made an attempt to fly out on November 30, but to no avail. Conditions remained cloudy at the site and our lead-off team (Tom, our BAS mountaineer, and Clément) camped for the next three nights at Fossil Bluff, a small base that BAS uses as a fueling station and staging area. Finally, on December 3, conditions warranted another try, and we arrived mid-afternoon at the selected spot. Camp setup is always a very full day, but by late evening we had the main tents up and the many cases of gear and tools ordered and aligned with the wind to reduce snow drifting. The next eight days were all about assembling, surveying, and drilling.

Our camp was comfortable, even spacious by deep Antarctic field standards, with a kitchen/work Endurance tent (nicknamed a ‘clam’ tent by BAS), a small outhouse tent, and our reliable Scott tents, the pyramid-shaped tent that was designed by the early British expeditions and is still used by many of the Antarctic programs across the continent. The Scott tent design is all about surviving intense storms and cold – strong side poles and a pyramid shape stand up to even 100 mph winds, and a double wall design and dark coloring make it surprisingly warm, even short sleeve comfortable on a sunny day. The Clam is the hub of the camp, where we cook, meet, and plan. One end is devoted to the kitchen and food storage, and the other end is for sitting, and gear such as backpacks, computers, and radios. The Scott tents were used as sleeping quarters, although one of them had a back-up kitchen in case of severe storms. The BAS “P-bag” (Personal bag) is a sleep kit that includes some real luxury items – foam pad, air mattress, and even a sheepskin to lay beneath a down sleeping bag, and plenty of additional options (sleeping bag liner, bivvy sack, camp down booties) for staying warm and comfy.

The science work in the two camps (December 3 to 11, Wilkins Ice Shelf, and December 12 to 17, the George VI Ice Shelf) centered on drilling and logging ice cores of snow and firn layers, assembling and raising the AMIGOS towers, and traversing the area to gather radio echo-sounding profiles of the snow and firn layering. Each of these goals contributes to assessing the presence of firn aquifers at the sites and the climate conditions that lead to them. We will discuss the drilling in the next blog entry.

Building the AMIGOS required assembling a lot of hardware and the tower, a 25-foot aluminum truss that will hold all the instruments high above the snow surface for several years. The AMIGOS is an automated observing station designed for the snow and ice, with an all-in-one weather station, a snow brightness sensor (sensitive to when the surface of the snow is melted), snow height indicator for measuring snowfall that will eventually bury the station, GPS for precisely measuring the ice movement, a camera for imaging the snow and sky conditions, and a long thermistor string running from the top of the tower to over 100 feet below the snow surface. As the tower is buried, the thermistors will provide a record of how the snow temperature changes. Since a firn aquifer indicates a lot of melting, and large changes in the temperature profile of the deeper snow, the thermistor string is one of the most important tools for understanding the evolution of the water-logged snow layer as time progresses. The AMIGOS stations record collected data internally, and can send most of the data using a satellite phone system (Iridium).

Assembling the tower, including the solar panels and instruments, and tacking down the cabling, required nearly six days at our first site, but having solved many little glitches, and with the experience of going through the process, we finished the second tower in just three days. Raising the AMIGOS towers was a challenge: the upper part of the weather station, weighing 150 pounds, had to be lifted carefully to stand the tower upright. We came up with a plan to use a long ladder as a crane, and Tom designed a rope and pulley system to lift the tower into place. We then secured the tower with three guy wires attached to boards buried deep within the snow.

With the towers up and secure, our attention turned towards mapping the layering in the region with the radio-echo-sounder system, called a ground-penetrating radar (GPR). Our grids around the two sites covered rectangular regions a few kilometers across, to provide an idea of how water and ice layers varied in the regions. Layers in the upper twenty meters indicate ice and denser snow within the pack.

The towers will stay above the surface, running on solar power and batteries, until they are completely buried in about three years. A follow-up trip will visit them just before they disappear to get the data chip and make further measurements, and recover any parts still accessible above the snow.

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This photograph shows part of the tent camp and science gear at Wilkins Ice Shelf. Credit: Clément Miège

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Here is a collage of the camp tents, inside and out. Upper left, the Clam tent; upper right, the latrine tent; middle left, the kitchen area inside the Clam tent; middle right, sitting area of the Clam tent; lower left, the two-person Scott tent; lower right, inside the Scott tent. Credit: Ted Scambos

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This collage shows the AMIGOS tower (right) and some of the sensors mounted on the system (left). From top left, GPS and Iridium antenna; snow height sensor and snow brightness sensor; weather unit; camera and the base of the control box. Credit: Ted Scambos

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Clem and Tom finish the set-up for raising the AMIGOS tower (left) using a ladder (right) and rope and pulley system (not shown). The tripod supporting the drill is in the center, above the borehole that will hold the thermistor string once the AMIGOS is erected. Credit: Ted Scambos

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The Ground Penetrating Radar (GPR) profiling system is attached to a sled behind the snowmobile. Credit: Ted Scambos

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This Ground Penetrating Radar (GPR) profile was collected at 250 MHz near the George VI Ice Shelf site. The echogram data represent about 600 meters across the snow surface. Units left to right on the plot are seconds of time. The sled was stationary for about 75 seconds before traveling 600 meters, and then stationary at the end of the profile for about 50 seconds. A thick ice layer is shown at about 10.4 meters depth, which was also noted in the George VI ice core. Credit: Ted Scambos

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Bruce is sealing the battery box to prevent meltwater leaking into it, prior to burying the batteries and other components. Credit: Ted Scambos

 

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