Humpback the Seaglider is an old friend of us at UEA. She has been to the Gulf of Oman, the North Atlantic and helped study melting glaciers around the Antarctic – and now she has become the first glider to be successfully deployed in the Bay of Bengal.
Deployed shortly after dawn, Humpback was sent diving to 50 m at first to test the initial settings, then progressively deeper until it reached its maximum depth of 1000 m.
The temperature difference between the surface and 1 km beneath the waves is extreme. At the surface, the waters are like a heated swimming pool at around 29°C, while at 1000 m the water is more like the North Sea in winter, at a distinctly frigid 7°C.
The temperature difference between the surface and 1000 m, combined with the very fresh surface water, make for an enormous density difference, which the Seagliders have to overcome to sink to the depths and return to the surface. All of this, combined with monsoon winds and stormy conditions makes for a challenging deployment. However, our trusty Seagliders are perfectly designed for this kind of challenge. More to come…
It was a truly extraordinary rendezvous, combining a very ambitious flight and some great observations from the ship. A BAe 146-301 four-engine jet, the UK Facility for Airborne Atmospheric Measurements (FAAM), flew past the ORV Sindhu Sadhana yesterday, just 100 ft above the waves, with other fly-bys at 300 ft, 1000 ft and 5,500 ft to get a profile through the lower atmosphere. Unfortunately, we have no photos yet, but I’m sure you can imagine how exciting this was for scientists on both the ship and the plane!
The aircraft is being operated as part of the INCOMPASS project, which is studying the interaction between monsoon rainfall and convective organisation depending on surface conditions over land and sea. The INCOMPASS project is a sister project of BoBBLE, as both are funded by the NERC-MoES collaboration to study Drivers of Variability in the South Asian Monsoon, along with the SWAAMI project which is investigating the impact of aerosols on monsoon precipitation.
The scientific aims of this were to get profiles of atmospheric conditions and heat fluxes around the ship location, where simultaneous measurements were made of surface heat fluxes, wind, temperature and ocean conditions, including the sub-surface radiation and temperature. The opportunity to compare atmospheric and ocean conditions in such detail is rare, and unprecedented during the Indian Monsoon.
Mission scientist Doug Parker aboard the FAAM said
“In summary, the flight was conducted almost exactly as planned, and the weather conditions smiled on us, to give us the opportunity to get exactly the datasets we had been aiming for. A great deal of effort by a lot of people went into the planning of this flight: I think it’s been an important milestone in the MONSOON programme, and I am very grateful for having had the chance to fly on it.”
We look forward to collaborating with scientists from the INCOMPASS project on analysing the results!
The BoBBLE cruise has departed today, following a departure ceremony led by Dr M Rajeevan, secretary for the Indian Ministry of Earth Sciences. The cruise sets sail for the southern Bay of Bengal, where scientists on board will monitor the ocean and atmospheric conditions for a month to better understand how changes in the ocean influence the monsoon rainfall.
The expedition takes place aboard the Indian ship, ORV Sindhu Sadhana, from which we will launch seven Seagliders (ocean robots that “fly” underwater) to take high-resolution measurements of the conditions in the Bay of Bengal, along a 400 km section in the southern part of the Bay, at 8°N, between 85 and 90°E. Observations will also be made from the ship itself, and by releasing nine customised Argo floats (simpler ocean robot, that drift passively with the currents) to take measurements over an even wider region. This research project is the first time that such detailed ocean measurements will be taken during the difficult weather conditions that prevail during the monsoon.
We are interested in measuring the interaction between the ocean conditions and the atmosphere, in particular how ocean processes change the surface temperature and thus the amount of heat available to drive the storm systems that bring rainfall over India. It has been suggested that changes in the surface conditions over the Bay of Bengal influence the Indian monsoon rainfall, but it is not clear what drives the changes in the ocean. One theory is the interaction between warm salty water from the Arabian Sea and colder, fresher water from the northern part of the Bay, where rainfall and river input reduce the saltiness of the water to around half the normal amount for seawater. It is not known how and where these different currents of water mix, especially during the monsoon when observations have not previously been possible. Some of the Seagliders are equipped with “microstructure probes” that can take direct measurements of how these water masses are mixing vertically, while the combination of all the measurements across the region will help us understand how the ocean currents transport heat and salt around this part of the Bay of Bengal.
Scientists from the UK and India will use the understanding we gain from the ocean and atmospheric observations made during the field campaign to help improve the models that are used to predict Indian monsoon rainfall. We will test the forecasts made during the monsoon and seek to improve how the models represent the ocean processes we observe. Forecasting the monsoon will always be difficult due to the complexities of the system, but hugely important to the Indian people and economy. We hope to be able to make a substantial contribution to improving these forecasts over the 5-year lifetime of the project.
Yesterday the Seaglider experts in the field team ran a training course for the BoBBLE scientists on how to operate Seagliders. This included everything from how to take them apart and rebuild them (pictured), to how to ensure they are ballasted to float perfectly in the water, and how to pilot them once they have been launched. It was a very successful day, and everyone learned a lot. This training will be crucial to ensure that the Seagliders can be safely launched and recovered in the challenging conditions the research cruise will encounter in the Bay of Bengal during the BoBBLE cruise.
Dr Venkatesan from National Institute of Ocean Technology (NIOT) welcomes the UK contingent, at NIOT Chennai. The UK scientists received a warm welcome and were able to check all the equipment that had been shipped from the UK arrived safe and sound. Preparations are now being made to load the equipment onto ORV Sindhu Sadhana, the research vessel managed by CSIR-National Institute of Oceanography, Goa, India.
A lot of the press coverage (such as the Daily Mail, Washington Post and the Japan Times) for the project in recent days has focussed on the ocean robots, or Seagliders, we will be deploying in the Bay of Bengal. So what are they, and how do they work?
Seagliders are about the size and weight of a small person, and look like a little yellow (or pink!) submarine. They are brightly coloured so that the field teams can spot them in rough seas and bad weather. They change their buoyancy much like a real submarine does, except that rather than filling tanks with air or water, they have a small bladder that they fill with oil (oil is lighter than water). They use their wings to turn vertical motion into horizontal motion, and can roll to turn, just like an aeroplane.
Our ocean robots will dive from the surface to 1000m below the waves, every 3 hours for a month during the BoBBLE cruise. They will take measurements of how warm, salty and biologically active the water is every 50 cm, as well as how much mixing is occurring on scales of a few mm. These measurements enable us to understand how the ocean currents bring warm salty water from the Arabian Sea into the Bay of Bengal, where they mix with the much less salty water that comes from the outflow from the Ganges and other big rivers to the north. These different “water masses”, or bodies of water with different properties, form layers beneath the surface, and understanding how and when they mix will enable us to better understand how the ocean provides heat to the atmosphere, thus driving the Indian Monsoon.
Scientists from the University of East Anglia, and the National Oceanography Centre are travelling to Chennai today to embark on a month-long research cruise in the Bay of Bengal to improve understanding and forecasts of the Indian Monsoon. The team will launch seven Seagliders: robotic submarines the size and weight of a small person that are perfectly suited to taking high resolution measurements of the ocean in rough weather. This is important because to date very few ocean measurements have been obtained during the Indian Monsoon due to the strong wind and large waves.
The scientists working on the BoBBLE project will use the information collected by these Seagliders, along with a wealth of data from the ship and nine Argo floats, to better understand what drives changes in the surface conditions over the Bay of Bengal. These surface conditions have a major influence on the monsoon rainfall in India, because the warm sea surface provides the energy and moisture that powers developing rainfall systems as they move northwards over the Bay. However, the details of the ocean processes are poorly understood due to a lack of observations. By combining the process-based understanding from the Seaglider observations with state-of-the-art computer simulations (in collaboration with scientists at the University of Reading), we will be able to test hypotheses and work towards improving forecasts of the Indian Monsoon.
UK scientists are making the last-minute preparations before departing for India next week for the NERC–MoES funded research cruise aboard the RV Sindhu Sadhana. The seven Seagliders, nine Argo floats and all the other equipment to measure temperature, salinity, dissolved oxygen and chlorophyll fluorescence. All of these observations will allow us to understand how the dynamics of the Bay of Bengal evolve during the monsoon, and how oceanographic processes influence the rain that then falls on India. It is going to be one of the most ambitious research projects ever conducted in this part of the world, and certainly the most observations ever gained at sea during monsoon conditions, when the wind and waves will be at force 6 (30 knot winds, 4 m waves) for the majority of the time. It’s going to be a challenging cruise, but the data will enable huge advances in our understanding of what controls the Indian Monsoon rainfall, and lead to improvements in our ability to predict this rain.
The preparations for this cruise have involved over two years of planning, multiple international meetings and dozens of teleconferences, two separate shipping containers of equipment, six separate clearance documents for each participant, 10 days in Chennai before sailing, and more changes of plan than we should really admit to! It has been a lot of work, and it is truly exciting to see it finally coming together.
Here is our current research plan:
In preparation for the BoBBLE research cruise in the Bay of Bengal in June this year, we are now packing up Seagliders, Argo floats, waterproofs and sunscreen, to be shipped to India.
The first cruise of the IIOE-2 project is now complete. The Sagar Nidhi sailed from Goa, India to Port Louis, Mauritius at the end of 2015 (and immediately after the launch of IIOE-2 in Goa). Prof. P N Vinayachandran co-led the expedition with Dr Satya Prakash of ESSO-Indian National Centre for Ocean Information Services (ESSO_INCOIS). The scientific team was international, including 12 Indian scientists, and participatnts from Mauritius, Israel, Singapore, Australia and the UK.
The cruise was an inter-disciplinary expedition to study the structure of water masses in the western Indian Ocean along 67°E. Measurements were taken of temperature and salinity, currents, oxygen concentration, light availability and chlorophyll fluorescence, along with water and zooplankton samples for future analysis and calibration.