ALBERT

Description: Sea ice buoy lightharp was deployed at the MOSAiC LM-site from mid January to August 2022. It measured autonomously and non-destructively the up- and downwelling light field in the ice. This dataset contains the raw data of buoy lightharp as it was received onshore via satellite link. Further information on the data format and the measurement record are collected in the attached protocol documents.

Description: During the MOSAIC expedition, we deployed in-ice light measuring buoys, lightharp, and lightchains into the ice to investigate light partitioning and irradiance at different layers and depths in sea ice. The dataset presented here contains processed data from both instrument systems, containing derived optical properties, PAR data, and auxiliary data for each deployment site. Auxiliary data gives information on the position, snow, and ice thickness statistics, and surface melt that changes the relative vertical position of the measurements. Auxiliary data was retrieved from SIMBA buoys deployed in the vicinity of the optical instruments. All data are provided in NetCDF format. The dataset includes processed data from the lightharp and three light chains (one redeployed on Leg5) from MOSAiC. The instruments were deployed at four different sites during MOSAiC: LM site (SYI dark coring site), L3 site, Pond site on Leg5 and within the Central Observatory (CO). The first part of the filenames reflects the deployment site. The second part gives the buoy name to which the optical sensors were connected and the last part the measurement period in YYMMDD. The NetCDF files were compiled using the profile_trajectory standard from CF conventions. Multiple directly measured and derived data layers are included with data coordinates depth and nominal_date. Nominal_date is the time of the uppermost valid measurement of a profile. Furthermore, files contain a set of already published auxiliary data describing the snow- and ice thickness statistics at the measurement sites (mean, max, min, and std) and a proxy for surface melt, that changes the vertical position of the frozen-in sensors. The lightharp data furthermore contains snow thickness from SIMBA buoy T62 and an individual surface melt approximation derived with temperature measurements at the optical sensors and surface melt rates. Data PIs and further helpful information is included in the attributes.

Description: Sea ice buoy saltharp was deployed at the MOSAiC LM-site from mid January to August 2022. It measured autonomously and non-destructively the temperature and conductivity between horizontal wire pairs, from which we retrieve solid fraction and sea ice bulk salinity profiles. This dataset contains the raw data of saltharp as it was received onshore via satellite link. The saltharp had severe technical problems, making most of the data unusable. A processed data set will exclude these values. Definitely wrong ones have already been replaced here with -999. as NaN indicator. Further information on the data format and the measurement record are collected in the attached protocol documents.

Description: Sea ice is difficult, expensive, and potentially dangerous to observe in nature. The remoteness of the Arctic Ocean and Southern Ocean complicates sampling logistics, while the heterogeneous nature of sea ice and rapidly changing environmental conditions present challenges for conducting process studies. Here, we describe the Roland von Glasow Air-Sea-Ice Chamber (RvG-ASIC), a laboratory facility designed to reproduce polar processes and overcome some of these challenges. The RvG-ASIC is an open-topped 3.5 m3 glass tank housed in a cold room (temperature range: −55 to +30 ∘C). The RvG-ASIC is equipped with a wide suite of instruments for ocean, sea ice, and atmospheric measurements, as well as visible and UV lighting. The infrastructure, available instruments, and typical experimental protocols are described. To characterise some of the technical capabilities of our facility, we have quantified the timescale over which our chamber exchanges gas with the outside, τl=(0.66±0.07) d, and the mixing rate of our experimental ocean, τm=(4.2±0.1) min. Characterising our light field, we show that the light intensity across the tank varies by less than 10 % near the centre of the tank but drops to as low as 60 % of the maximum intensity in one corner. The temperature sensitivity of our light sources over the 400 to 700 nm range (PAR) is (0.028±0.003) W m−2 ∘C−1, with a maximum irradiance of 26.4 W m−2 at 0 ∘C; over the 320 to 380 nm range, it is (0.16±0.1) W m−2 ∘C−1, with a maximum irradiance of 5.6 W m−2 at 0 ∘C. We also present results characterising our experimental sea ice. The extinction coefficient for PAR varies from 3.7 to 6.1 m−1 when calculated from irradiance measurements exterior to the sea ice and from 4.4 to 6.2 m−1 when calculated from irradiance measurements within the sea ice. The bulk salinity of our experimental sea ice is measured using three techniques, modelled using a halo-dynamic one-dimensional (1D) gravity drainage model, and calculated from a salt and mass budget. The growth rate of our sea ice is between 2 and 4 cm d−1 for air temperatures of (-9.2±0.9) ∘C and (-26.6±0.9) ∘C. The PAR extinction coefficients, vertically integrated bulk salinities, and growth rates all lie within the range of previously reported comparable values for first-year sea ice. The vertically integrated bulk salinity and growth rates can be reproduced well by a 1D model. Taken together, the similarities between our laboratory sea ice and observations in nature, as well as our ability to reproduce our results with a model, give us confidence that sea ice grown in the RvG-ASIC is a good representation of natural sea ice.