a, Austral summer (DJF) 2019–2020 averaged chlorophyll-a relative anomaly map with cyan contour lines indicating where the anomaly is equal to 100%. b, Austral summer (DJF) 2019–2020 cumulative deposition of dust and black-carbon with black contour line indicating where deposition is equal to 150 mg m−2. c, Pixels where both [Chla] relative anomaly exceeds 100% and cumulative deposition exceeds 150 mg m−2 are marked in green. Black boxes indicate the South of Australia and Pacific Southern Ocean regions defined in this study. All: Subtropical, Subantarctic and Polar Fronts are indicated with a dotted, a dashed and a solid black line, respectively.