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Eddy with a why – SEAmester presents a vortex of science

By Safiyya Sedick, Jordan Van Stavel & Zonke Gumede, SAEON Egagasini Node
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Forty-eight science students from institutions across the country participated in a ten-day at-sea practical training course aboard the Southern Ocean research vessel SA Agulhas II.

The programme was led by Prof. Isabelle Ansorge, head of the Department for Oceanography at the University of Cape Town, and the initiator of the programme.

The science conducted on board the ship focused on the South Atlantic MOC Basin-wide Array (SAMBA) and the influence of the Agulhas leakage on the Meridional Overturning Circulation (MOC). Students attended lectures, assisted with the deployment of scientific instruments and presented research projects which they conducted throughout the cruise.

The SA Agulhas II voyaged from East Pier, Cape Town on 17 July to the Greenwich Meridian (0° E) and docked in Cape Town on 28 July this year.

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Students preparing to board the research vessel SA Agulhas II

The anticipation of what the next ten days would bring seemed to be very clearly written on the optimistic faces of the students who were about to embark on this adventure; one that would take them across the South Atlantic Ocean and into a different time zone. An adventure that would transport them into a different world, so tranquil and almost untouched by humans it seemed unreal.

It would be a little while before the realities of a swiftly moving ship would sink in and the dreaded seasickness would claim its first victims. But not for long - the narrow corridors would soon be filled with boisterous laughter and lively conversation as the science got underway.

We were divided into two lecturing streams: Tools of the Trade and Oceans in a Changing Climate. As the name suggests, Tools of the Trade focused on various methods of measuring the physical properties of the ocean, using an assortment of instruments each comprising very expensive sensors. Oceans in a Changing Climate focused on the biological aspect of the ocean, the role of the ocean as a carbon source and carbon sink, the interconnectivity of the ocean with the atmosphere and how it affects life in the sea.

The scientific objectives of SAMOC along the SAMBA line involved the retrieval, refurbishing and redeployment of Eulerian instruments such as Acoustic Doppler Current Profilers (ADCPs) and Current and Pressure Inverted Echo Sounders (CPIES) as well as the deployment of Lagrangian instruments such as Expendable Bathythermographs (XBTs), Argo floats and surface drifters. Along the transect line, biological equipment was also used for the collection of in situ biological samples from plankton pumps, neuston and bongo nets as well as dredges.

Mini research projects

Early in the cruise we were asked to select a mini research project that saw us working in conjunction with a scientist throughout the voyage. Isabelle also tasked each stream with making a video that represented our experiences on the cruise.

This, along with the mini research projects, was presented on the last day. The making of the video was a wonderful opportunity to connect with our fellow classmates and allowed our inner filmmakers free rein.

Lectures

A reasonable amount of our time was dedicated to a diversity of lectures. The lecturers presented an exciting mix of research applications that varied from marine spatial planning and wave and atmospheric modelling to weather forecasting and bioacoustics.

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The Tools of the Trade students on the heli-deck

Eddy with a ’y’

The implementation of the work taught during the lectures was interestingly applied to some unexpected science, which added the ‘y’ factor to this cruise and highlighted the fact that we failed to spell ‘eddie’ correctly. This took place towards the end of the cruise and saw a group of the scientists on board collaborate on a multidisciplinary project - studying a mesoscale oceanographic feature known as an eddy!

This feature is strongest at western boundary currents, and begins as a result of mean flow instabilities that are pinched off by the meandering of the current. An eddy can be identified as closed circulatory systems that have different physical properties to their surrounding waters (Pilo et al., 2015).

In the southern hemisphere, a cold core eddy will have a cyclonic rotation, whereas a warm core eddy will have an anticyclonic rotation. These eddies play an important role in the mixing of the ocean by carrying considerable amounts of heat, nutrients and organic matter between water masses.

In collaboration, the scientists looked at the nutrient content and the physical properties (temperature, depth, salinity) of the eddy surveyed during this cruise. We anticipate the publication of their findings!

Joint seminar sessions

We often looked forward to our evenings on board, which included intriguing joint seminar sessions during which lecturers and students presented either their research or previous research cruise experiences. Here, we realised that SEAmester was not the first of its kind globally, but is South Africa’s own little class afloat and is an amazing programme nonetheless, and one that we were very fortunate to be a part of.

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SAEON students Safiyya Sedick (left), Jordan Van Stavel (centre) and Zonke Gumede on board the SA Agulhas II leaving sunny Cape Town for the unpredictable weather of the open ocean

Recovery of an Acoustic Doppler Current Profiler (ADCP) from the seafloor                                                                                                  

Life on a ship

Adjusting to life on a ship proved to be scary for most of us, but adhering to house rules turned out to be a blessing in disguise. For example, at the beginning of the cruise, meal times onboard posed a challenge as it forced us out of our comfort zones. The seating arrangements of the dining area required us to fill up empty seats before choosing to sit with friends. This allowed us to engage with almost everyone at least once for the duration of the cruise and eventually became something we looked forward to.

This became a trend with many of the happenings on the ship. For instance, getting up at 2 am and sleepwalking your way to the 7th floor to witness the deployment of a weather balloon, or down to the 3rd floor to see the retrieval of a scientific instrument. It was soon discovered that bribery with chocolate was always a catalyst to get students out of bed at this hour!

Lastly, we had to get used to being rocked to sleep by the constant movement of the ship, hoping you don’t fall out of your bed in the middle of the night during choppy waters. These effects were felt for days after the trip had ended.

An added bonus provided almost every day of the cruise were bridge and engine tours of the vessel, which added extra insight into exactly how the vessel operated and what its capabilities were. Everyone also took every opportunity to do some whale watching, which at times took a great deal of patience, but was worth the time hanging around when an animal was spotted.

As the cruise drew to an end, we found ourselves in leopard and leaves, geared up for a jungle-themed party. Dancing the night away in our goofy costumes made for a perfect end to a very successful cruise.

SEAmester provided a relaxed platform in which students and lecturers could interact both informally and intellectually, allowing for a wholesome and thorough learning environment. We highly recommend this programme for anyone who has an interest in marine science.

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Satellite-derived image illustrating sea surface current velocities surrounding Southern Africa - SAMBA transect line indicated at 34.5 S 0 E and the mesoscale eddy t (002). (Compiled by Charine Collins)

If you would like more information on SEAmester or would like to apply, the website can be accessed here. Alternatively, the authors or Prof. Isabelle Ansorge may be contacted for more information.

Reference

Pilo, G. S. Mata, M. M, and Azevedo, J. L. L. (2015) Eddy surface properties and propagation at Southern Hemisphere western boundary current systems. Ocean Science 11: 629-641.

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