Study of Sea Ice Biogeochemistry (snow depth, ice thickness, ice salinity, dissolved inorganic carbon, total alkalinity, biomass, under ice currents) Comparing a Thick First Year Ice Site, and a Thinner Polynya Site Near Cambridge Bay

The selected sites were both on level first year ice: one approximately 5 km to the east of the Finlayson Islands, outside of the polynya where we expected weaker currents and thick first-year ice, and one directly between the islands, in the polynya where we expected strong currents and thin first-year ice. Sampling was conducted over a 6-day period between 4 and 10 May 2019, with both sites visited on three days (4, 7, and 10 May). On the first sampling date, inverted tilt current meters (Lowell Instruments TCM-1 Current Meter) were installed at both sites to measure velocity (units: cm s-1) in 1-minute intervals. Sea ice sampling was conducted at the sites using a Kovacs Mark II 9-cm diameter coring system. Snow depth (units: cm) was measured with a meter stick prior to collection; ice thickness (units: cm) was measured after core collection with a measuring tape. One core was collected at each site on each day for temperature and salinity profiles. Temperature (units: degrees C) was measured using a Thermopen Mk4 temperature probe at 10-cm intervals. The core was cut into 10-cm sections, which were sealed in plastic bags, melted, and analyzed for salinity using a YSI multiparameter probe (units: PSU). For sea ice carbonate sampling, 10-cm sections were cut and sealed in the field. Samples were melted in the lab, and transferred to 160-mL borosilicate bottles using a peristaltic pump and fixed with mercuric chloride. At each site, we obtained one “high-resolution” core for TIC and TA (10 May), where sections were collected every 10 cm from top to bottom. On each date, 5 locations were randomly selected within a 10-m radius of the centre point of each site. At each of these locations a core was extracted to collect the top, bottom, and middle 10 cm for TIC and TA analysis. This yielded a total of 15 samples for each horizon (top, middle, bottom) for each site. Ice samples from the bottom 5 cm of three additional cores were combined in an opaque jug, melted in the lab, and filtered for Chl a analysis. Laboratory analysis was conducted at the University of Calgary and the University of Manitoba. TIC was determined through acid extraction (units: umol kg-1) ,TA was measured by modified Gran Titration (units: umol kg-1). Remaining sample water was then analyzed for salinity (units: PSU) using conductivity meter. Chl a concentration was determined by fluorometry and converted to biomass (units: mg m-2) by multiplying by the length of the core section.