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.