Southern Ocean water quality dynamics associated with sea ice formation and melt

The Southern Ocean spans from the coast of Antarctica to latitude line 60° S. This ocean consists of many unique features, such as the strong Antarctic Circumpolar Current, large deposits of freshwater contained in icebergs, as well as suspected oil and gas fields on the continental margin. Our objectives were to 1) to determine potential relationships among water quality parameters; 2) to compare magnitude of change in parameter responses to season at surface and depth; and 3) to map potential locations with disproportional freshwater inflow. Data from a subset of the SOCCOM floats was downloaded, combined and re-subsetted based on surface and depth values.

Physical, chemical and biological parameters were correlated to determine potential mechanistic relationships. Mean response to seasonal change at the surface and at depth were compared using t-tests. A variety of interpolation methods were used to explore spatial patterns in each parameter relative to summer melt based freshwater influence. RGui software was used for data manipulation and statistical and graphical analysis. QGIS 3.12 was used to map the floats and subsequent spatial analysis via IDW interpolation.

Parameter relationships with depth were high variable near the surface level, however, predictive relationships at depths greater than 500 m were clearer and more consistent. Differing responses to seasonal changes at surface and depth were also observed. Interpolation of surface water quality demonstrated salinity and chlorophyll patterns which appeared to be linked to potential freshwater melt sources. Areas of lower temperature and higher salinity were found to consistently have low dissolved oxygen and chlorophyll values, which makes sense considering the dynamics of melting and formation of sea ice. This analysis could allow for inferences on localized water quality to be made based on satellite images tracking sea ice.