The presented daily mean sea ice draft time series are derived from bottom track mode measurements from multiple upward-looking Workhorse 300 kHz Sentinel Acoustic Doppler Current Profilers (ADCPs, manufactured by Teledyne RDI). ADCP moorings were deployed and recovered during multiple TRANSDRIFT expeditions to the Laptev Sea (2003 to 2016). A total of 13 data files, named to indicate the location of the deployment (station name) and the sampling period, provide values of daily mean sea ice draft (in m) and time. Sea ice draft is derived from ADCP bottom track data following Belter et al. (in review). An additional info file provides the coordinates of the stations, expedition specifics and serial numbers of the instruments.

Short processing summary:In ice covered regions like the Laptev Sea upward-looking Acoustic Doppler Current Profilers (ADCPs) that are operating in bottom track (BT) mode use acoustic pulses to measure range (the distance between the instrument and the ice surface above). Multiple studies have shown that ADCP-internal pressure measurements provide instrument depth and therefore the means to derive sea ice draft. Due to the lack of internal pressure sensors the presented sea ice draft data from Laptev Sea ADCPs is based on a different approach to determine instrument depth. We provide a short summary of the individual processing steps presented in detail by Belter et al., (currently in review at The Journal of Atmospheric and Oceanic Technology):1. Determination of open water periods:ADCP measurements of surface and error velocity provide information about surface inconsistencies in vertical velocity between the four measuring beams. Differences in the vertical velocity are small during ice-covered periods and large when open water occurs. Based on this assumption open water can be distinguished from ADCP error velocity data.2. Determination of instrument depth:Tilt-corrected range values measured during open water periods therefore provide instrument depth. In order to calculate sea ice draft the most frequently occurring open water range value was selected as constant instrument depth value for the respective sampling period and mooring.3. Derivation of sea ice draft:Laptev Sea ADCP sea ice draft, d, was calculated for each mooring data set using the following equation:d = z - r • cos(t),with z being the most frequently occurring tilt-corrected open water range value per sampling period and mooring, the range value r (distance between instrument and ice surface) and the instrument tilt angle t.