Shelf Sea Biogeochemistry blog

Showing posts with label gliders. Show all posts
Showing posts with label gliders. Show all posts

Tuesday 18 August 2015

36 years of working on Discovery

By Peter Statham
Ocean and Earth Science, University of Southampton

When I first set foot on the old Royal Research Ship Discovery in 1979 in Cape Town I had little idea that in 2015 I would be on the Discovery once again but now on the most recent version of the vessel to carry this famous name. 

I am interested in the chemistry of the ocean and how chemical processes affect the biology and other parts of the marine system. This aspect of oceanography is important in terms of understanding how the sea works and can be impacted by climate change. 

On this trip we are studying where the essential nutrient iron comes from on the shelf and how it may move away into the open ocean.  In some areas the element is at such low concentrations that it limits plant growth and thus impacts ecosystems, so it is important to know where it comes from, and one potentially important source are the edges of shelf seas. 

Launching a glider from Discovery. Gliders move up and down through the water by altering their density and “glide” on their wings from one location to another in the upper ocean, whilst collecting data that is sent by satellite to shore when it is at the surface. This new model has a small propeller to help it occasionally overcome strong currents.
Whilst frequently demanding with long working hours I always enjoy the times at sea with the wide range of people on board, the constant challenges to be dealt with and the buzz when a long planned experiment finally works out.  Whilst new techniques such as satellites and gliders are developing rapidly, ships are still essential tools in the study of the oceans. Discovery is a world-class research platform for UK marine science that will support our new generation of oceanographers into the future.

Friday 17 July 2015

Meanwhile, science continues

By Mark Moore

Around the drama of Wednesday afternoon (see Lucie’s recent blogpost), the science on board continues apace. Over the 5 intensive days of science to date we have already completed 72 ‘Events’ each of which effectively corresponds to a deployment of one of the many pieces of equipment which you may have read about during previous log entries, including deployments of moorings and gliders, CTDs, net sampling (see picture below) alongside snow catchers, in situ pumping systems, etc, etc ....  

Picture: The ongoing event log in the main laboratory
Others: A CTD coming on deck
Net sampling
Mooring deployments
A glider being ballasted on board before being deployed

With all this activity occurring on board it is important that we keep detailed, accurate and up to date records. The first stage in making sure everyone knows where we are with planned activities is a running event log which we keep in the main lab of the ship (see picture). Here we provide a rough record of what has happened to date, allowing the person leading the next activity to confirm the event number and providing a record for checking against more detailed logs. Simultaneously the officers on watch also keep a separate ongoing record of all activities from up on the bridge. One of my jobs as principal scientist then involves keeping a check to make sure that all these logs are aligned. It pays to have multiple redundancy as although a research ship is a reasonably small space, with everyone working in different areas of the ship and at different times of the day and night effective communications can sometimes still be a challenge!

Work wise we are currently around half way through another of our CTD (Picture) sampling transects down the shelf edge aimed at understanding the processes by which iron (Fe) may be transported off the shelf. Working where the water depth shoals so steeply has its own challenges. We have to be extra careful lowering sampling equipment near to the bottom as there are regions of the shelf break where the water depth can change by 1000m in under a km, i.e. a >45% slope!

Thursday 16 April 2015

OMG - Glider glee!

Dr Charlotte Williams, Marine Physics and Ocean Climate, National Oceanography Centre

Today at our main sampling site (CANDYFLOSS) we are deploying our sixth and final ocean glider! Ocean gliders are robots which ‘glide’ up and down in the water whilst taking measurements of temperature, salinity, chlorophyll and oxygen (plus a few more things), and these are what I work with. They send their data back to us when they surface via satellite. The amazing thing about gliders is that we can see the data they are collecting from anywhere with an internet connection as soon as they surface (every 30 mins or so in 100m of water). In fact as I am writing this blog I am checking the data that is coming in from the 4 gliders we have out at the moment! This has been useful for our research cruise as we are trying to catch and sample the ‘spring bloom’. This is where light and nutrient requirements for phytoplankton in the surface become just right in spring, and so we see a bloom in phytoplankton growth. This can be observed by an increase in chlorophyll, which the gliders measure.  

The ‘OMG’ glider being ballasted in the tank. Photo: Jose Lozano.

Sam Ward, the glider engineer from National Marine Facilities, has been working very hard to ensure that the gliders are ready for the water. This includes ‘ballasting’ them in a big tank on the back deck. The gliders don’t have a propeller, they move up and down in the water by changing their buoyancy, which is much less power hungry. Sam has to check how buoyant the gliders are in the seawater that they are being deployed in, as the density of seawater changes according to its temperature and salinity. There will be more to come on how the gliders work in Sam’s future blog! The last glider being deployed today is particularly exciting as this is an Ocean Microstructure Glider (OMG). This glider measures all of the things listed above, but also measures the turbulent kinetic energy dissipation, which is a kind of fancy term for turbulence and mixing. Being able to estimate the mixing in the shelf seas is important because we can then estimate how nutrients and carbon move around.  We will have to see if the dolphins return to see the OMG glider!  

Another glider about to dive under the waves. Photo: Jose Lozano

Wednesday 19 November 2014

Looking for particles (again….)

Ocean research cruise blog of Jonathan Sharples


We deployed the last of our gliders yesterday afternoon. This one is being piloted to patrol between the shelf edge and our mooring site, 100 km further onto the continental shelf; it will do this continuously from now until earl March when it will be picked up during another cruise. We then had a very successful night looking for particles. Starting just before sunset we deployed our two “Stand-Alone-Pumps” (SAPS). These pumps are lowered on a wire to a fixed depth, and programmed to pump water through large, dinner-plate sized filters typically for 1 or 2 hours.

Clare and SAPS
 Clare Davis, from the University of Liverpool, will analyse the filters to measure the ratios of carbon, nitrogen and phosphorus in the tiny organic particles caught on the filters – a vital part of the story of how carbon and nutrients are cycled through the sea, ultimately supporting the marine food chain and also absorbing carbon from the atmosphere. We also tried the large Marine Snowcatcher again, this time after some modifications carried out by the Ben and Tom the National Marine Facilities Engineers. It worked at last! Both the SAPS and the Marine Snowcatcher were deployed, first close to the sea surface and then at a depth of about 100 metres. This is quite a relief for us – knowing the make-up of the particles in the ocean is a vital part of what we are trying to measure.

Original Post 
SAPS over the side