In order to fully understand the chemistry data we get from blowing snow, we need to assess the sea ice itself and snow lying on its surface. This includes the dense salty layer closest to the ice surface, and the typically wind packed layer on top of that. So lately, the days we don’t fly we have been out collecting surface snow samples and ice cores on a transect between McMurdo Station and the ice edge. We load up two snowmobiles and a sled with our Kovacs ice corer, an ice auger, a gas powered drillhead, and two survival bags. The survival bags are required each time you go to the field, and each supports two people for about three days. They contain a tent, a shovel, two sleeping bags, a camping stove, dehydrated food, cooking and eating utensils, and a paperback book chosen, evidently, for the amusement of those packing the bag (think Harlequin romance novels). Each survival bag weighs about 50 pounds. Since we’ve been taking a third person on these expeditions, we need to take two survival bags. Fortunately, we’ve not had to use them.
When we first arrived, there was open water in the middle of the Ross Sea, as you can see in this satellite image that Ross has annotated with place names. McMurdo and Scott Base are on the point of a penninsula off the southwest side of Ross Island, which looks like a three leaf clover in the lower right of the image. Note the lack of sea ice out at Cape Bird on the north side of Ross Island. Our two blowing snow collection tower sites are to the northwest of Ross Island and are indicated with red stars. The snow and ice core transect begins at the W in Wohlslang Bay and continues South toward McMurdo.
Over the following week this froze over with a thin skim of ice on it, something which was not completely apparent until it snowed and the new ice was covered with a dusting of snow. It remains easy to tell the newer ice from that which formed during the winter. The latter has patches of pancake ice, patches where sections have rafted up on top of other sections, and pressure ridges. The new ice is very flat. In the picture below, the ice on the right is over a meter thick (closer to two meters everywhere we have drilled). The dark ribbon in the center is the open water separating the old ice from the new ice. This band of open water formed a few days ago when we had very strong winds from the South, which pushed the new ice away from the old. Here you can see that ice is reforming on this open water. The ice to the left of the image is all new ice and its hard to say how thick it is, but perhaps a few inches. You can see, even from a helicopter that the surface is covered with frost flowers (they sparkle)
The ice edge looking South from a point between our sites
The southernmost end of the open water, with Mt. Erebus in the background
On Thursday, we drove north from McMurdo, first out an established ice road (the Cape Evans Road), and then off of that and into the interior of the frozen Ross Sea. Using satellite imagery of the ice extent, we had selected a series of sites between the ice edge (top center in the photo above) and McMurdo Station, and are collecting sea ice cores and snow samples at 2 km intervals. Ross programmed the GPS coordinates of these sites, which together form our transect, into the handheld GPS unit. He sat on the back of the lead snowmobile and directed me with hand signals while I drove. The second snowmobile followed to pick up anything that fell off the back of the sled. The sea ice was pretty smooth and even bare in some spots, and covered with drifts or chucks of rafted ice in others, which made for interesting driving (but nowhere near as challenging as the Hudson Bay in February was).
We started our transect at the furthest site, which was at about the top center of the ice shown in the image above. While we were 2 km from the ice edge by our satellite imagery and GPS calculations, we were close enough to walk to new ice with frost flowers. Frost flowers were the subject of my postdoctoral research, as they are very salty and provide lots of additional surface area for gas phase reactions. For reasons I won’t go into here, they are probably not the primary source of gaseous bromine in the boundary layer, but are interesting to behold, nonetheless.
Field of frost flowers on new ice, Transantarctic Mountains in the background
Frost flowers
Ross tasting the frost flowers
Eight hours spent leading an expedition on uncharted sea ice with two snowmobiles, three people and $20K worth of equipment is pretty draining, and that’s before the -35C windchill (standing still), hauling 50 lb bags on and off the sled, and wrestling with the Kovacs corer, a $7K instrument whose fondest wish is to spend the rest of its days stuck in the sea ice… until the ice melts and it sinks to the bottom of the Ross Sea. I just keep repeating this mantra to myself, “I will not be the PI who (fill in the blank)!” e.g. falls through the sea ice, loses a $7K piece of USAP capital equipment, litters the Antarctic with stuffed bears,… etc.
So far so good.
Rachel on Ice 2012 