SANAP Project News: SOCCO Gliders Home

SOCCO, SANAP, Southern Ocean

Our Wave Gliders have arrived back from the Southern Ocean.  Last Friday 5th April we picked up our second carbon Waveglider WG027 a few tens of metres from the breakwater in Granger Bay at the end of an exciting but problem free transit of 1500km from the Sub-Antarctic Zone (43oS 8oE)(Video).  Its twin WG052 had completed its even longer transit of 2800km from the Polar Upwelling Zone (54oS OoE) 9 days earlier.  Both units arrived in excellent shape in what was a first for us, bringing our gliders home with a ship pick-up.  Both gliders completed 4-month long missions of which 10 weeks were sampling at their respective locations and 6 weeks transiting back to Cape Town.

VIDEO: WG052 waiting to be picked up off Granger Bay in a cold misty morning in Cape Town a couple of weeks ago after its 2800km epic from 54oS.

Bringing the gliders home under their own means opens the door towards the direction of reducing the dependency on ships and reduces the long-term costs of long-term observations.  It is a significant technical challenge for the robots and the engineers.  The biggest problems we encountered, apart from the vicious storms, were the very strong mesoscale jets west of the Agulhas retroflection area.  Jets with flow speeds of over 2kn posed navigation challenges for the pilots but we also learned much from the experience and despite a few necessary deviations (Figure 1a,b) that probably added a week to the transit we got them home in really good shape (Figure 2).

The decision to bring them home was shaped by two main considerations: firstly, we wanted to avoid the expensive physical damage to the gliders that often happens with ship recovery, especially under the typically rough conditions in the Southern Ocean.  As it turned out we made the right call especially for WG052 which would have been all but impossible to retrieve such were the conditions.  Secondly, we wanted to evaluate if wave gliders can be combined to address mesoscale differences in the response of the ocean to synoptic scale atmospheric forcing.

As mentioned in earlier posts each of these gliders was paired with a buoyancy glider over the entire period of deployment at their respective long-term observational sites in the SAZ and the PUZ as part of two NRF-funded SOCCO SOSCEX-Storm projects.  This pairing enabled us to simultaneously observe the air-sea fluxes of CO and the ocean physics dynamics that influence them in the upper 1000m of the ocean.  This is necessary because it is not clear how important these ocean dynamics are in predicting the climate sensitivity of the carbon cycle in the Southern Ocean.   This learning will be used to improve the Earth System Models used to predict regional and global climate change, particularly the South African CSIR-VrESM model being developed as a collaboration between SOCCO, Global Change Institute-Wits University and the MaRe Institute at UCT.

All the instruments were fully operational over the entire time and the initial look at the data suggests that we have excellent accuracy and precision.  This was the first operational test for our newly developed VeGAS pCO2 units on both gliders and we will do a deep dive into the data later this week.

This science work would not have been possible without the expertise and dedication of our engineering partners at Sea Technology Services who run SA-RobOTIC and their student engineers.

 

– Dr. Pedro M. Scheel Monteiro & SOCCO & SA-RobOTIC team, 08 April 2019 (posted 16 April 2019)

Current Cruise: Glider deployment, data collection and retrieval

SOCCO, Gliders, CSIR, UCT

The S.A. Agulhas II is now on its homeward journey having finished all logistical and scientific work at SANAE and in the Weddell Sea (track the ship here). The work is not yet over for all aboard, however. Scientists from the University of Cape Town (UCT), the Council of Scientific and Industrial Research (CSIR) and the South African Weather Service (SAWS) continue to collect oceanographic and meteorological data. UCT and CSIR are both sampling seawater as the ship sails, measuring chlorophyll, nutrients, ammonium and phytoplankton community composition, to name a few.

Over and above this, CSIR—more particularly, CSIR SOCCO—and Martin Mohrmann of the University of Gothenburg and ROAM-MIZ deployed oceanographic instruments on the voyage south to Antarctica (see photos below). CSIR SOCCO, or the Southern Ocean Carbon & Climate Observatory, is a South African research programme focused on the Southern Ocean. ROAM-MIZ, according to their website, “is a multi-institutional initiative to observe the full seasonal cycle of the upper ocean in the marginal ice zone near the Greenwich Meridian”. CSIR SOCCO deployed two wave gliders, a Seaglider and a Slocum glider. ROAM-MIZ deployed two Seagliders and a Sailbuoy, christened SB Kringla. These instruments continuously record oceanographic data while they move through the water. The wave gliders and the Sailbuoy remain at the surface, harnessing wave and wind power, respectively, to propel them through the water. The Seagliders and Slocum glider alter their buoyancy to dive and sample sea water during their journeys to the deeps (deep parts of the ocean) and back to the surface. All these vehicles transmit their data to satellites at regular intervals or when they surface after a dive.

Deployment of Gliders

With the S.A. Agulhas II now making for home, the time has come to recover these instruments in order that they can be serviced and used again in future deployments. The wave gliders, in a true feat of engineering, are being piloted home to Cape Town. This is due to reducing sunlight available for the solar panels of the southernmost glider as the receding summer light wanes at these high latitudes. This will entail a journey of 1200 km and 2500 km for the respective wave gliders (click here for the update on the position of the gliders). Two Seagliders, the Slocum glider and the Sailbuoy will be recovered on the voyage home. The third Seaglider is to be recovered by another vessel, the Norwegian RV Kronprins Haakon, sailing from Punta Arenas in Chile.

On the 1st of March, the Sailbuoy and a ROAM-MIZ Seaglider were both safely recovered in fair weather at 60°S 0°E. The speed and success of the recovery were entirely down to the skill of the S.A. Agulhas II’s crew and the prevailing calm weather. Next, the Slocum glider will be recovered at 54°S 0°E and then CSIR SOCCO’s remaining buoyancy glider at 43°S 8°E. The S.A. Agulhas II is now making for 54°S 0°E after having sailed to South Thule and South Georgia for SAWS deployments and commitments.

Retrieval of Gliders

For more information on CSIR’s SOCCO programme, click here and for further information on ROAM-MIZ, click here.

Cover Photo: ROAM-MIZ’s two buoyancy gliders making satellite contact in preparation for deployment.

 

Written by: Hermann Luyt, Oceanography, University of Cape Town

Edited by: Anché Louw, Antarctic Legacy of South Africa, 07 March 2019

Photo Credit (all): Hermann Luyt

SANAP Project News: SOCCO (follow-up)

SOCCO, SANAP, Southern Ocean

SOSCEX-Storm II Experiment Wave Gliders heading to Cape Town from the Antarctic waters

Following up on the story of the our Liquid Robotics Wavegliders returning home to Cape Town from the Southern Ocean (click here) we have now completed the first half of the journey. Waveglider WG052 will arrive at its intermediate waypoint 43°S 9°E on Saturday 2nd March.  It has completed the first 1200km of its journey in 17 days at an average of 70km per day during which it sailed through 3 storms and crossed both the Polar and Sub-Antarctic fronts (see photo below).

SOCCO, Gliders, Wavegliders

On Sunday 3rd March WG052 will meet up with its twin WG027 that has been making its own CO2 and physics measurements at our long term observation station SAZ-1 since early December 2018. They will return together in the second 1200km stretch of sub-polar and sub-tropical waters but separated by about 50 – 100km to test some ideas about the correlations length scales for pCO2.  Both units continue to provide almost real time observations of ocean physics and CO2.  You will see from the attached pic (earth.nullschool.net), which is derived from almost real time satellite observations-based surface ocean circulation product OSCAR of the mesoscale features around the south of Africa, that we are aiming to use one of these “jets” to propel both gliders towards Cape Town across the turbulent cauldron west of the Agulhas current retroflection.  It shows very nicely how the ocean is not made up of large homogeneous currents but a series of high speed jets and eddies.  We are exploring how the interaction of storms with these features influence the seasonal variability and ultimately the climate sensitivity of the air – sea fluxes of CO2 in the Southern Ocean.

 

– Dr. Pedro M. Scheel Monteiro & SOCCO & SA-RobOTIC team, 01 March 2019 (posted 06 March 2019)

SANAP Project News: SOCCO

SOCCO, SANAP, Southern Ocean

SOCCO: Southern Ocean Carbon & Climate Observatory

SOCCO, SANAP, Southern OceanSOCCO. Glider, Southern Ocean

SANAP Project name: How storm characteristics in the Southern Ocean influence inter annual variability of CO2 fluxes

This summer SOCCO conducted the second SOSCEX-Storm glider-based experiment in the Southern Ocean as part of its 3 year science plan. We deployed two carbon wave gliders equipped with our SA-RobOTIC designed and built and pCO2 sensors, which have behaved flawlessly under the most dire conditions that the Southern Ocean could throw at them, which included weekly storms of 80-140km/h winds, waves of 10+m, snow storms and sea temperatures of -1 to 2°C.  During this 2 month period they have taken over 3000 pCO2, pH, temperature and salinity observations. It was a rigorous test for the pCO2 sensors, which have a design feature that is specifically made to cope with Southern Ocean storms. It can be submerged by a wave which will mean that it taken a bit of water through the air intake but when the detectors pick this up it uses it pressurized gas to expel the moisture and continues to provide high quality data.  This deployment was a significant achievement for our SA-RobOTIC engineering and an indication of how our expertise to operate in these conditions has matured and become globally recognized.  This deployment was important for two reasons, it allowed us to start to examine the role of storms in driving the carbon – climate feedback in the Southern Ocean and it is a preparation phase for the SCALE experiment that starts in July 2019.  The hypothesis, which is core to our NRF-SANAP and DST funding, that we are exploring is that climate-linked changes in storm characteristics will play an important role in the century scale carbon – climate feedbacks. Ocean robots and high precision sensors make this science possible.

We have however encountered a problem with the glider deployed at 54°S which is, that while it generated enough power during the peak of summer with nearly 24 hours of daylight, this is no longer the case in February with the sun setting for increasingly long periods – night is arriving in Antarctica.  Wave gliders use solar panels to power the sensors.  The second glider was deployed at 43°S where there is still plenty of sunlight.  In a normal year the gliders would have been picked up by the S.A. Agulhas II coming back from SANAE at about this time but this year the ship is coming back nearly 5 weeks later because it is chartered by a British team to find the Endurance, Shackleton’s ship.  As a matter of interest we are collaborating with some of our aeronautical engineering colleagues at CHPC (Centre for High Performance Computing) to develop an underwater power generator to enable us to make winter (no sunlight) deployments in July 2019.

For this reason we have made the decision to pilot both wave gliders home to Cape Town without the ship.  This will be a journey of 2500km for WG-052 and 1200km for WG-027.  We think this has the added advantage of reducing the risk of damage during retrieval by the ship, which has happened a few times due to the normally difficult conditions on retrieval.  So, wave glider 052 has now left its long term observation position at 54°S on the prime meridian and is heading home towards wave glider 027 which is at 43°S.  It is travelling at a speed of about 100km per day.  The sensors are all working and we will take advantage of this opportunity to conduct an experiment that needs 2 gliders while they are on the way home.  We expect them home in a month, mid-March and we will pick them up in Granger Bay in front of our SA-RobOTIC centre.

SOCCO, Southern Ocean, Gliders

Route of the WG052 and 027 gliders (2019)

The wave gliders were paired with a buoyancy glider each that are making observations down the water column to 1000m 4 – 5 times a day.  This pairing of wave gliders and buoyancy gliders is a SOCCO innovation under the SOSCEX series of experiments since 2013/14.  The two buoyancy gliders will remain on station waiting for ship retrieval in mid-March.

 

– Dr. Pedro M. Scheel Monteiro & SOCCO & SA-RobOTIC team, 18 February 2019

 

SOCCO on Social Media

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