Changing biogeochemistry of the Southern Ocean and its ecosystem implications

Abstract

The datasets published here apply only to unpublished nutrient data from the wintertime trans-Southern Ocean sections WOCE line IO6 (2017) and A12 (2019) and one summertime surface ocean A12 ammonium dataset. Nutrient concentrations are in units micromole per liter. Variables measured from the CTD (pressure, temperature and salinity) for the two wintertime datasets are provided at 1 m resolution.

Winter nutrient sampling was conducted aboard the R/V SA Agulhas II in 2017 (WC-17; 28 June – 13 July 2017) along WOCE line IO6 (Indian sector) and in 2019 (SCALE; 18 July – 12 August 2019) along WOCE line A12 (the GoodHope repeat hydrographic line; Atlantic sector). Seawater was collected at regular depth intervals in 12-L Niskin bottles attached to a CTD rosette. Samples for the analysis of nitrate, nitrite, dissolved silicon and phosphate concentrations were decanted into replicate 50 mL HDPE tubes that were copiously rinsed prior to filling. Duplicate tubes were immediately frozen at -20°C for later measurement of nitrate and dissolved silicon, whilst nitrite and phosphate samples that were to be measured shipboard within a few hours were stored in the fridge. Duplicate samples of unfiltered seawater (~40 mL) were also collected at each depth between the surface and 500 m for the analysis of ammonium concentrations in 50 mL HDPE Nalgene bottles that had been stored (“aged”) with orthophthaldialdehyde working reagent (OPA-WR) prior to sample collection. The OPA-WR was decanted just prior to sample collection and bottles were rinsed three times with sample seawater prior to filling.

The datasets published here apply only to unpublished nutrient data from the wintertime trans-Southern Ocean sections WOCE line IO6 (2017) and A12 (2019) and one summertime surface ocean A12 ammonium dataset. Nutrient concentrations are in units micromole per liter. Variables measured from the CTD (pressure, temperature and salinity) for the two wintertime datasets are provided at 1 m resolution. Winter nutrient sampling was conducted aboard the R/V SA Agulhas II in 2017 (WC-17; 28 June – 13 July 2017) along WOCE line IO6 (Indian sector) and in 2019 (SCALE; 18 July – 12 August 2019) along WOCE line A12 (the GoodHope repeat hydrographic line; Atlantic sector). Seawater was collected at regular depth intervals in 12-L Niskin bottles attached to a CTD rosette. Samples for the analysis of nitrate, nitrite, dissolved silicon and phosphate concentrations were decanted into replicate 50 mL HDPE tubes that were copiously rinsed prior to filling. Duplicate tubes were immediately frozen at -20°C for later measurement of nitrate and dissolved silicon, whilst nitrite and phosphate samples that were to be measured shipboard within a few hours were stored in the fridge. Duplicate samples of unfiltered seawater (~40 mL) were also collected at each depth between the surface and 500 m for the analysis of ammonium concentrations in 50 mL HDPE Nalgene bottles that had been stored (“aged”) with orthophthaldialdehyde working reagent (OPA-WR) prior to sample collection. The OPA-WR was decanted just prior to sample collection and bottles were rinsed three times with sample seawater prior to filling.