On the hydrology and productivity of the northern Arafura Sea

Abstract In the context of the Snellius-II Expedition data, on temperature, salinity, dissolved oxygen, various nutrients and some biological variables were collected in the northern part of the Arafura Sea during two cruises of R.V. ‘Samudera’, carried out in August 1984 (southeast monsoon) and February 1985 (northwest monsoon). Evidence was found for upwelling during the August survey, in particular along the south coast of Irian Jaya, the upwelled water being probably derived from the western slope of the Arafura Sea. The area was clearly stratified in August, as evidenced by differences in several variables in surface and near-bottom water. Stratification was weaker or absent in February, probably due to a higher vertical mixing. Such a higher mixing could also explain the relatively high nutrient concentration found in surface waters in February. Mean nutrient concentrations over the water column were higher in August than in February, which was attributed to different circulation patterns in the two seasons, leading to nutrient enrichment by slope upwelling in August, whereas nutrient supply in February is mainly dependent on riverine input.