Under-ice measurements of suspended particulate matters using ADCP and LISST-Holo

Using a mooring package comprising an acoustic Doppler current profiler (ADCP) and holographic imaging system, a 1-day ice camp study was performed under the Arctic sea ice in the northern Chukchi Plateau to estimate vertical and temporal variations in total suspended particulate matter (SPM). In early August, the SPM in the upper mixed layer (~15 m and above) under sea ice reached up to about 100 mg l^-1 even under the offshore regime. Results of both holographic and microscopic analyses showed that dominant constituents of this increased SPM were biogenic rather than lithogenic materials. Due to the highest melt and break-up rates of sea ice during the summertime, the export of particulate materials and ice algal communities embedded in the sea ice might significantly contribute to the increase in SPM. This study suggests that the combined effects of the increase in ice algal production and the decrease in ice and snow cover and multi-year sea ice extent could create favorable conditions for enhancing the concentration and flux of SPM during the summertime.