The dataset contains a subset of physical oceanography data collected by the Norwegian Institute between 1981 and 2015. The data come from moored instruments (current meters, ADCPs, temperature and salinity sensors), and from CTD casts (standard casts from ships, and casts with portable equipment on helicopter transects). It also contains bottle data (such as oxygen isotope ratios and nutrients), sea ice thicknesses observed by upward looking sonars, and sea ice drift observed by ADCPs. This dataset is available as a JSON API only.

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.

Helicopter-borne electromagnetic induction sounding (HEM) sea ice thickness measurements made in the Barents Sea region in March 2014. A total of 8 separate flights were conducted during this campaign. The thickness produced by this sensor is ‘total thickness’, that is ice + snow, but is normally referred to as ‘sea-ice thickness’. This work was supported by the European Space Agency SMOSice project (ESA contract 4000110477/14/NL/FF/lf). We would like to thank the crews of Airlift helicopter and RV Lance for their assistance with the collection of this dataset.

The EMbird was flown from RV Lance on legs 3 & 4 of the NICE expedition; that is in transit to, and on station at, Floe 3. We would like to thank the crews of Airlift helicopter and RV Lance for their assistance with the collection of this dataset. # Basic flight information |Flight|Date|Start Time(UTC)|Purpose/ notes| |---|---|---|---| |F1|15-04-15|18:09|-| |F2|18-04-15|16:42|NO DATA! Aborted 5 mins in due weather conditions.| |F3|19-04-15|09:05|Survey line also flown by BAS twin Otter / Partly coincident with ALOS image. NB GPS drops| |F4|24-04-15|08:52|Local area survey. Later same line was flown by BAS twin Otter.| |F5|24-04-15|14:29|Cryosat-2 underflight. Partly coincident with previous evenings ALOS image. NB GPS drops| |F6|28-04-15|07:34|- NB GPS drops| |F7|29-04-15|09:07|Partly coincident with ALOS image (long track north east).| |F8|30-04-15|09:17|-| |F9|03-05-15|11:40|NO DATA! Aborted 10 mins in due weather conditions.| |F10|05-05-15|11:14|-| |F11|05-05-15|12:54|Cryosat-2 underflight. NB GPS drops| |F12|05-05-15|16:49|-| |F13|06-05-15|09:07|-| |F14|06-05-15|14:36|Overflew line of long walk with EM31 and magnaprobe (ice and snow thickness data).| |F15|08-05-15|08:00|Partly coincident with TSX image.| |F16|11-05-15|14:45|Short flight -visibility poor. Attempted to overfly inner buoy ring.| |F17|12-05-15|11:27|-| |F18|18-05-15|11:42|-| # Data format Filenames: Each file name follows the convention: date flight number V2 Data is presented as tab delimited text with the following columns: Date, Latitude, Longitude, Sea Ice Thickness (m) # Production Method Flight data was processed in IGOR using routines originally developed at AWI (Alfred Wegener Institute for Polar and Marine Research). The processing has two stages, first detrending the data to correct for instrument drift, and then recalibrating the sea ice thickness based on flight notes and Go-Pro pictures showing ice conditions. The routine used to generate sea ice thickness from the detrended raw data relies on a model file which varies depending on sea water conductivity. Based on information from Amelie Meyer about the conductivity measured from the ship CTD, 2700ms was chosen for all flights. The thickness produced by these routines is ‘total thickness’ that is ice + snow, but is normally referred to as ‘sea-ice thickness’. Following processing with the IGOR routines bad data (NaN and negative values) has been removed. **IMPORTANT LIMITATIONS RE GPS DROPS** Flights 3,5,6 & 11 suffered with the GPS on the bird dropping out for long sections. When this happens the logger still logs GPS TIME but the POSITION is missing. I have fixed these sections by matching GPS track from a GPS carried in the helicopter to the thickness measurements using GPS time (interpolating thickness onto the GPS track). This was done 'by hand' in Matlab AFTER processing the thickness data with the IGOR routines. Please contact me (Jennifer King) if you find something in the data from these flights that does not make sense.

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 snow stake readings see https://data.npolar.no/dataset/3099ea95-c3cd-4a8b-af5d-73750e46d791.

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.

Temperature, salinity, and density for 148 sea ice cores drilled dring the N-ICE2015 cruise. Ice cores were retrieved from a variety of ice types at different locations on each of four floes.

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