Written by Chris Polashenski
Yesterday we arrived a rather momentous site, in a somewhat anticlimactic manner. After running fast and smooth for a hundred miles or so, and catching glimpses of the coastal mountain range being ducted to us by atmospheric inversions that bent light from beyond straight-line visible range, we expected to arrive at our final site west, closest to the edge of the ice sheet whooping, hollering, blaring fast, and with mountains all around. As we got closer we began to see hills and valleys in the ice, and got ever more excited. Gradually at first, however, the surface began to get slightly rougher. Within several miles we were in HUGE sastrugi – a surface with waves of rock hard snow as much as 4 feet high. Our blaring 40mph run quickly dropped to a 10-15 mph weaving-dodging maneuver as we punished our kidneys and our loads over some truly uncomfortable terrain and delicately tried to find a better path forward. The weather was warming too, in the 20’s F and I was worried about melt as we burned a considerable amount of our precious fuel driving around hummocks in low gear. No mountains either. As we arrived at the site, we realized that the increasing ice topography had us essentially driving in a trough with no view of anything but ice. The weather was a balmy -1C on the weather station’s first test, and with the dual threats of melt turning the place into a quagmire, and the possibility that whatever sort of storm could possibly have made the surface topography we were driving in might come back, we were not eager to spend a great deal of time at the site. Reading Carl Benson’s report of a June 12, 1954 storm very near the site which brought sustained 70mph winds only re-enforced our eagerness to depart.
The rough ride punished more than our kidneys. We’re told that our bread crumb tracker – which shows our current position on the web is no longer transmitting – I’ll look into this tomorrow. A number of station components also ended up worse for wear and were higher priority in the current triage. This site was the place of our last station deployment and we were all excited to get this last “space trash”, as Mike calls our whirligigs and do-hickeys, unloaded. Carrying these 5 stations has added to our loads considerably – 850lb of batteries, 300 lb of tripods, two large boxes of sensors, a bale of solar panels and more, each component adding a few ratchet straps to our daily un-strapping and re-strapping routines. Fortunately, all of the damage (which included a shattered solar panel face, 2 broken connectors, a few abraded cables, and some sheared bolts) was field-repairable with our toolkit, some epoxy, duct tape, and solder in the rather sublime 20’s F temperatures and dead calm winds we had at this odd, and apparently usually stormy, place. We’re pleased to report that “Frankenstation” lives and is now sending data back hourly via Iridium, ready for the next storm or whatever it is that happens at site Benson 1-10.
Among other things, the five weather stations we’ve deployed will continue a measurement I take at each site – the surface albedo – all year long. Albedo is key to this project – how much sunlight the ice sheet reflects exerts enormous influence over how much melt occurs on the ice sheet, and by extension how much sea level rises. Collecting albedo alongside our measurements of grain size and black carbon will help us understand how large an effect each of these is having on light absorption during the snapshot in time when we visited each site, but maintaining these measurements will tell us about changes occurring after we depart. A measurement of albedo can be simply a sum of all the solar energy incoming and outgoing (an “all-wavelength” albedo). Or you can take a spectral albedo – measuring the fraction of incoming sunlight that is reflected wavelength by wavelength across the solar spectrum. These stations will be unique in that we’ll measure spectral albedo with them as well as all-wave albedo. The spectral albedo gives us quite a bit more information about the surface. Human eyes, for example, are spectral sensors and phenomenal ones at that. We can see and identify the range of wavelengths from roughly 400-700 nanometers. We just happened to call them colors – the colors of the rainbow from deep red to green to blue all fall in this range of wavelengths and being able to tell the different light spectra apart is quite useful. Knowing how much of each wavelength a surface reflects allows us to identify things – for example, the red sled (gasoline) from the green sled (food!). Similarly knowing how much of each wavelength the surface of the ice sheet is reflecting tells us about what is changing the overall albedo. Snow grain size, for example, exerts quite a lot of influence on reflection of near-infrared light (light in the range from about 700-2500 nanometers wavelength, which is invisible to the human eye.) A drop in near infrared albedo observed by the stations , which we are already seeing at our current sun-glazed site, will tell us the grain size has changed after our departure.
This evening I got a little jaunty with our ASD spectral radiometer and decided to show off its capabilities a bit. Check out the attached plot of the spectral signature of the red sled, green sled, red fabric, blue cot, and our orange tent. Knowing that blue light is around 400 nm, green about 550, and red 650+ see if you can identify which spectra came from which item without looking at the key. Also note that the instrument can observe light from the ultraviolet (shorter wavelengths than we can see) to the near infrared (longer than we can see), which gives us even more information about a surface than the eye does. While it is difficult to tell the red fabric from the red plastic in the plot zoomed in to only visible wavelengths, they are easy to tell apart in the near infrared.
After finishing the station late last night, we packed up and headed out, to hit one last station that Carl Benson occupied some 60 years ago before we blaze our own (circuitous) path back to Summit. Carl had made a short southerly leg off his main traverse to verify that the accumulation rate on the south side of the peninsula we’ve driven west out was high all the way along, even though it drops off dramatically along the traverse route, which crosses over to the north, rain-shadow, side. We figured we could catch the southern tip of this leg along the return route. Leaving the station deployment site, however someone, who shall remain unnamed, appears to have made a modest navigational ‘error’ to the south. The ‘error’ may have been carefully calculated as a celebratory measure to give us some more climactic and stunning views of coastal mountains and nunataks (mountains that emerge from the ice sheet). Staying well clear of crevasse zones still allowed us to get within good visual range of a number of magnificently remote mountains. Being just half an hour’s ride from some certainly tempted the peak bagger in each of us, but being separated by an unknown labyrinth of enormous crevasses kept us from any further navigational errors. The climb back up onto the ice sheet via an ice flow channel was absolutely stunning – the climb our trip -and back on smooth surfaces to open the snowmachines back up.
Here in camp at Benson 1A-20, the nunataks are fading out of view as the wind whips up to around 30 knots and suspends a nice little ground blizzard all around us to welcome us back to the ice sheet. We’ve finished our pit (160 cm of accumulation last year), sampled for carbon, taken spectral albedos, and snow casts, measured grain size, installed a 10 meter temperature string, and eaten 14,000 calories of food between us. Truly a magnificent couple of days. Tomorrow we head northeast to cross into the lowest accumulation zone of the ice sheet. We wonder what’s going on over there and have some questions we want to answer!