Ice Cold Katy
After almost a week of prep, fitting the aircraft and test flying her around Rothera, I finally got a chance to go flying in the MASIN (Meteorological Airborne Science INstrumentation) aircraft, aka Ice Cold Katy, on Sunday.
The weather was almost perfect: a ‘dingle day’ on the eastern side of the Peninsula over Larsen. Even on the west it was pretty good, and we departed Rothera in glorious sunshine, only a few shreds of cirrus above.
After take off, Rothera disappeared rapidly into the distance: a reminder of how unexplored and unconquered this continent really is. We set a course for the Weddell Sea, about 300 km to the east.
Climbing steadily, we flew east over the Peninsula mountains. The views were simply spectacular. Looking down, you see a sea of white, broken by dark ridges and hard igneous facies forming the crests of waves. Black outcrops of rock thrust themselves out of the snow, throwing blue shadows where the steep terrain causes crevassing on the slopes. The views from 10,000 ft totally blew my mind.
What we really came for – the science
It wouldn’t be a science flight if all the instruments worked the whole way through, so naturally the Picarro, which measures greenhouse gas concentrations, had a hissy fit about an hour in and crashed, probably because it didn’t like the change in pressure caused by our ascent over the mountains.
We managed to get it working again once out on the ice shelf, and got around half a flight’s worth of sensible readings for atmospheric gases – water vapour, methane and carbon dioxide.
However, the stuff I am interested in is mainly the turbulent and radiative fluxes over Larsen C. So I was pretty pleased when we nipped down to low level to sample the atmosphere 500 ft above the ice surface. In new money that’s something like 150 m – it’s just that pilots like to work in feet (and presumably shillings and fathoms, too…). We were close enough to see the sastrugi (bizarre little turrets of snow blown into formation by the wind) whizzing by – aside from those, it was pretty much a blank, featureless plain flat and empty enough for mirages to appear in the distance.
As we approached the ice shelf edge, we started to see icebergs (real ones this time), and as we soared out over the edge, the ice dropped away into a sheer cliff. The gap between the edge and the newly calved iceberg A68, one of the largest in recorded history, is a lot bigger than I had imagined. I had been picturing some Star Wars valley flying between two narrow ice walls, but it was a lot more like driving down an open highway. Goes to show that looking at satellite imagery doesn’t really give you much of an idea of the scale: it’s only once you see it that you appreciate the vastness of an iceberg the size of a small island nation.
We soared out over the new sea ice, dropping our altitude to get better measurements of the turbulent fluxes of heat and momentum critical for understanding the exchange of energy between the atmosphere and ocean.
The sea ice zone here is interesting because it’s an area that has previously been covered with ice shelf – therefore the changes in energy are all new and exciting. In fact, these are the first observations of fluxes made in this newly uncovered area of water!
From there, we dipped and turned north to run a couple of legs along almost the entire length of the iceberg, including some over the calm, glassy open water of the Weddell (it really was great weather). It will be interesting to compare the fluxes over sea ice vs. over open water and examine the effect that the calving of A68 has had on atmosphere/ocean exchange.
Turning back from the Weddell, we ran one even lower leg straight back over the Larsen the way we had come – down as low as 100 ft at one point. Having a look at the surface energy budget on this flight will be super interesting and I can’t wait to get my hands on the data.
On our descent back to Rothera, I sat upfront in the co-pilot seat. The clouds had started to close in and the mountains were shrouded in a low stratiform veil, making the islands surrounding home loom like gorillas in the mist.
Tiny little Rothera twinkled in the distance, the runway, previously indistinguishable from its rocky environs, emerging suddenly from its surroundings. Trundling in to land, icy ol’ Katy rocked and swayed, buffeted by the wind that had picked up while we were gone.
As the propellors wound down, we got a tow back into the hangar with one of the air unit’s tractors. I leapt straight out once we’d stopped to wrestle myself out of the immersion suits we wear when flying over open water. Putting one on is like being born again, and getting it off is almost as bad, apart from the promise of freedom from your rubbery prison. After flying at high altitude, the increase in pressure as you descend makes you resemble a vacuum packed raisin, and it makes you feel like a total space cadet.
Eventually, wearing our civvies again, we trekked it back to base. Turns out five hours of flying in a Twin Otter is pretty knackering, so the Sunday roast that welcomed us back was very much appreciated.
Our next flight will hopefully be over the JCR, BAS’s research vessel. She was hoping to moor today, but the sea ice has proven too thick, and she’s had to try another route. With any luck, that’ll happen this week, and we’ll have even more exciting data to look at.