At the beginning of the experiment we laid out five survey lines. Surveys of snow depth were routinely conducted along these lines throughout the SHEBA year. Measurements were made every 1-2 weeks from October through May and every other day from June through August. The surveys consisted of walking along a line and measuring snow depth every one to five meters. Snow depth was measured either manually using a graduated ski pole or automatically using a magnaprobe (as pictured). Manual measurements were rounded off to the nearest centimeter and magnaprobe values were accurate to better than 0.5 cm. Care was taken to repeat the surveys along the same lines, but no attempt was made to measure at exactly the same points. During summer, pond depths, as well as snow depths, were measured along these lines.
Mainline: This was our longest line at 500 m. It originated at Pittsburgh, extended over the ridge, and continued past Quebec and Seattle. In January 1998 the line was lengthened when leads opened and froze between the 100 and 400 m marks. The portion of the line beyond the 150 m mark was lost during the 2 August 1998 breakup event.
Atlanta: A 200-m-long line at a site collocated with the Atlanta Pam station. Aside from a small ridge at the beginning of the line, the terrain here was fairly flat.
Tuk: This 200-m-long line traversed our Tuk mass balance site going directly over an old ridge at the 50 m mark of the line. The line was intact for most of the year. There were a few areas that melted through in summer, necessitating a couple of detours.
Baltimore: This was a first year ice site collocated with a PAM station. The ice began growing in late-August 1997 and was only about 35 cm thick at the start of the experiment. A substantial ridge formed at the edge of this line in January 1998.
Cleveland: The line went through an old eroded rubble field adjacent to the Cleveland PAM station. Cleveland was a short-lived site. The ice broke up in January 1998 and the site was abandoned.
Snow results from the surveys show a gradual increase in snow depth during the winter following by a rapid 2-3 week snow melt period in early June.
