The Roland von Glasow Air-Sea-Ice Chamber (RvG-ASIC): an experimental facility for studying ocean–sea-ice–atmosphere interactions

摘要

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?m 3 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, τ l = ( 0.66 ± 0.07 ) ?d, and the mixing rate of our experimental ocean, τ m = ( 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.