Sea ice, snow depth, freeboard, and total thickness (ice + snow) measurements from 2" drillholes or ice core holes during the N-ICE2015 expedition. EM31 conductivity value for EM31 calibration are included where available.

All available snow depth measurements with Magnaprobe.

On the four N-ICE2015 floes we installed in total seven hot-wire fields and seven snow-stake fields following the routine outlined in Perovich [2003]. A rectangular hot-wire field with a side length of approximately 10 m was designed in a way that in each corner a wire was installed close to an ablation stake, and in the middle of the hot-wire field nine snow-stakes with even spacing were set up. Snow depth and ice thickness changes were recorded on a regular basis, and the readings were averaged in space to cover small scale spatial variability. For the hot wire readings see https://data.npolar.no/dataset/263a317f-5a65-4776-8f53-ef2c2857fc33

Total ice and snow thickness was measured with portable electromagnetic instruments (EM31 and EM31SH, Geonics Ltd., Mississauga, Ontario, Canada) mounted on a sledge. The EM31s measure the received secondary electromagnetic field, induced by highly conductive seawater (Kovacs et al., 1991). Conductivity values are calibrated with drill hole measurements and post processed according to Haas et al., 1997. [Figure 1](https://api.npolar.no/dataset/70352512-fed8-4f1d-8b9c-30e6a764f5c2/_file/f5fa353f31a63b4d4167379acc785e73) shows the calibration curves for the two EM instruments used throughout the experiment. In total 101 and 145 calibration drillings were made for EM31SH and EM31, respectively, covering a thickness range from 0.15 m to 4.50 m ice. Analysis of the calibration measurements did not reveal any drift in the fitting curve parameters on the temporal or spatial scales. The footprint size of the EM31 ranges from 3 m to 5 m, depending on the ice and snow thickness. Accuracy of EM31 measurements is in the range of +-0.1 m for level ice, becoming higher for rough and deformed ice. On all four Floes, independent (i) and repeated transects (t, tF, tM) with combined EM31 and snow depth measurements were performed. Repeated transects are considered as repetitions of marked tracks on a weekly basis to observe temporal change, while independent transects are long surveys in different directions from the main ice camp are to cover the spatial variability of the surrounding area.

This dataset includes all snowpit observations from N-ICE2015.