First week at sea

Johan’s sampling mission began the day after leaving Cape Town harbour. He samples the surface ocean for a number of biogeochemical properties at high resolution across the fronts. These fronts separate very distinctive water masses in the Southern Ocean; each of these waters masses as well as each of the fronts have a “fingerprint” combination of properties, such as temperature, salinity, oxygen and nutrient contents. For example, as you can imagine, the sub-tropical waters are warmer that the sub-antarctic waters further south. These two water masses are separated by the Subtropical Front, roughly at ~40°S, whereas another front further south, the Subantarctic Front, roughly located between ~44 and 45°S, separates the sub-antarctic water from the polar water. South of the Subantarctic Front, we find the Antarctic Circumpolar Current (ACC), forming a belt around Antarctica. This is the most important current in the Southern Ocean and you might have heard of this area as the Roaring Forties, since the prevailing westerly winds driving the ACC are extremely strong. A third front even further south, the Polar Front, roughly located at ~50-51°S, separates the polar water from the Antarctic  water. These fronts can be around 80 km in width! They usually show enhanced primary productivity, due, for instance, to the upwelling of nutrients from deeper, nutrient-rich waters. Consequently, they also provide suitable foraging conditions and are often visited by marine predators.

Johan in and his major sampling set-up for high-resolution surface water sampling using the ship's continous seawater intake from the bow.

Johan in and his major sampling set-up for high-resolution surface water sampling using the ship’s continuous seawater intake from the bow. (photo credit: Johan Viljoen)

and the set-up for specific samples, here for particulate organic carbon (POC) and Genomics that allow us to study the microbial community composition.

and the set-up for specific samples, here for particulate organic carbon (POC) and Genomics that allow us to study the microbial community composition (photo credit: Johan Viljoen).

a typical filter from a very productive area. The brownish-green colour results from the pigments of the phytoplanton (algae), Johan's research focus. The tin foil protects the material and filter from dirt on the benches in the wet lab.

A typical filter from a very productive area. The brownish-green colour results from the pigments of the phytoplankton (algae), Johan’s research focus. The tin foil protects the material and filter from dirt on the benches in the wet lab (photo credit: Johan Viljoen).

Johan processing a sample for nutrient analysis. The samples will be stored frozen until analysis upon return from the voyage in February 2017.

Johan processing a sample for nutrient analysis. The samples will be stored frozen until analysis upon return from the voyage in February 2017(photo credit: Johan Viljoen).

The Roaring Forties. Waves constantly batter the ship at these latitudes.

The Roaring Forties. Waves constantly batter the ship at these latitudes (photo credit: Johan Viljoen).

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One thought on “First week at sea

  1. Pingback: Colours in the sea and in the sky | 2016, new year, new Southern Ocean adventures: off the benches, in the waves and in the sky ..

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