Tuesday December 9 was Positive Day at Lake Hoare. Positive Day is the day when the temperature first reaches above 0° C. Tuesday was also Renee’s birthday, and I don’t know anyone who is as positive as Renee. It all made sense.
Positive Day is important because when temperatures are consistently above freezing, and days are sunny, streams start to flow, and they can flow heavily. (The relationship between temperature, solar radiation and melting is complicated by physical and, possibly, biological factors. I’ll try to learn and write more on this in the future.)
By one measure, Positive Day at F6 was on Monday. We have two thermometers at F6, one on the north side and one on the south side. The one on the south side is a gauge built into the wall, and looks official and accurate. The one on the north side is just a department-store indoor/outdoor thermometer and looks decidedly unofficial.
On Monday, at one point, we saw 40° F (c. 4° C) on the sunny (north) side. At that time the (shady) south side read 35° F so we were averaging about 3° C. Distinctly positive. Up to that time we had one stream running, the Canada Stream, hard up against the east flank of the Canada Glacier. We now expected more.
One of my projects is to get a good GPS shot at each of our gauges, and I had continued to forget to do that at the F3 Gauge on Lost Seal Stream. So, Monday afternoon Mikey and I drove/walked to Lost Seal so I could get my shot. The gauge itself is hidden behind a little hill until you are just on it, but as we walked up I could see the stream some distance to the left and I swore it was wet. When we crossed the ridge we could see a nice flow coming through our gauge control! This surprised me because just 24 hours earlier I had visited the gauge in cold, cloudy weather with Li Ling, an NSF fellow, and Lost Seal Stream had been dry as far up as we could see. But, this is the nature of the Dry Valley streams–when the conditions are right, they can start flowing in short order.
When we looked at the Commonwealth Glacier, the source of water for Lost Seal Stream, we could see water in stream channels on the glacier surface. They look like blue veins across the surface, and they poured water off the edge of the glacier into our streams. Our work load was about to increase. Once flow starts we need to take water samples and measurements of flow, temperature and specific conductivity (a surrogate measure for the amount of mineral solids dissolved in the water), and we have to relate these to the measurements made by the electronic sensors deployed in the streams.
I estimated the flow at F3 to be about 1/3 liter/second (l/s). Because we hadn’t expected flow, we didn’t have sample bottles so we returned to F6 and got some. When we got back to F3, I made a flow measurement with the Baski, which yielded a flow of about 0.25 l/s. That was not a bad estimate. We are trying to develop our ability to estimate flows because we will be sampling streams where we won’t have a Baski and where flows will be too low to use a Pygmy meter (more on the Pygmy later) so we will have to rely on our estimates.
Tuesday we returned to Lost Seal to find the flow at about the same level. We then moved on to the F5 Gauge on Aiken Creek where we had to fix a leak in the nitrogen bubbler system (more on this later) and replace the nitrogen tank. When that work was done we returned to F6 for some lunch and hopped on the ATV for the first leg of the trip to Lake Hoare to celebrate Renee’s birthday.
To get to Lake Hoare by land (technically, by land and ice) we first drive the ATV on the Lake Fryxell ice west to near the mouth of Mariah Creek, hard up against the east flank of the Canada Glacier on the south shore of Lake Fryxell. From there we walk a couple of miles around the toe of the glacier to Lake Hoare and across the lake to the camp. Today, we checked all of our gauged creeks on the south side of Fryxell as we made our way west. None were flowing at their mouths, but Mariah Creek, which is not gauged, was flowing nicely. Water was cascading off the Canada Glacier into the creek, which is quite short.
As we moved around the Canada Glacier we could see water starting to flow in the upper reaches of Bowles Creek (ungauged) and Green Creek (gauged at F9). We knew that it was very likely that when we returned from Lake Hoare the following day that water in those streams would be reaching Lake Fryxell and we would need to sample them.
We needed to run levels at the H1 Gauge on Andersen Creek (located within steps of my tent at Lake Hoare) so we carried the level, tripod and rod with us. This made the walk a bit of slog for me, but Mikey just ambled along. When we reached Lake Hoare we found Andersen Creek running strongly at the H1 Gauge. We took samples and made measurements and then ran our levels. We finished at 7 pm, just in time for Renee’s birthday dinner.
Rae prepared a wonderful chicken curry, served with three chutneys, and a flourless chocolate cake that brought tears to the eyes of this chocoholic. After a round of presents, the group moved to the beach for a Frisbee party. (The beach is a sand dune deposited against the west flank of the Canada Glacier, between the glacier and Lake Hoare.) I left the party a little after 11 p.m. because I felt like I was getting sunburned.