Cape Evans sea ice physical and biological properties

Fast ice was sampled roughly every second day over a 4-week period (November 2019) at a coastal site just off Cape Evans (McMurdo Sound). Ice cores were collected to determine vertical profiles of temperature, salinity, as well as the chlorophyll-a concentration in the lowermost 10 cm (two times 5-cm sections) of the ice cores. Measurements also included snow thickness, ice thickness and sea-ice freeboard levels. The data were collected as part of AAS 4546 and contribute to a larger NZ-led project, Antarctica New Zealand Event KS043, led by Dr Andrew Martin (Victoria University Wellington).
Ice cores were sampled from the same 2m2 area using a Kovacs Mark II ice corer (9 cm internal diameter) powered with an electric drill. Snow thickness was measured with a ruler before sampling, and sea ice thickness and freeboard measurements were taken from the resulting ice core holes. Sea ice temperatures were measured with a Testotherm720 thermometer (accuracy 0.2 °C immediately after ice core retrieval from small holes drilled in the core at 5 – 10 cm intervals. Thereafter we sectioned the core in 0.05 to 0.15 m sections using a stainless steel saw. Ice core sections were placed in Milli-Q water washed polyethylene (PE) containers and melted at 4 °C in the dark within 24 to 36 hours after sampling. Ice bulk salinity was determined on the melted samples with a calibrated conductivity meter. Sub-samples of known volume were subsequently filtered onto Whatman GF/F filters and stored frozen (liquid nitrogen) until extraction with acetone for 24 hours at 4 °C in the dark and determination of the chlorophyll a (Chl a) concentration with a Turner Designs 10AU fluorometer according to Arar and Collins (1997, EPA Method 445.0). Chl a is reported in µg l-1 melted sea ice.