Sea level change – signs in the sediments

How does sea level change affect marine life? This is one intriguing question Expedition 381 is exploring. We know sea level rises and falls around 120 meters (~400 feet) every time the planet alternates between glacial and interglacial periods. Scientists use the term glacial to describe intervals when the Northern Hemisphere had large ice sheets extending well into Canada, United States, and much of Europe. As ice built up it took water from the ocean lowering the average sea level of the planet. The Gulf of Corinth is an ideal location to study the rise and fall of sea level because the entrance (Rion sill) is only 61 meters below sea level. Therefore, the Gulf of Corinth was sometimes connected to the Mediterranean and at other times it was an isolated lake!

Of course, seawater and lakes have very different animals and plants. Also, oceans have distinctive chemistry compared to freshwater. These differences will cause changes in the geology which we can observe in the drilled cores. Many of the records we are collecting show these variations clearly! As we drill in different locations and measure different aspects of the sediment and pore water, we learn the fine details of these processes.

As all fun science however, the more we learn the more questions we create!

Clint Miller

Main image: Simone Sauer and Patrizia Geprägs collecting methane samples. Courtesy of DSmith@ECORD/IODP

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Cores, Coffee and Food!!

From the first few weeks of the expedition offshore, three priorities have emerged within the team. In no particular order; Cores, Coffee and Food! We’ve focussed on the cores previously so this one is about the coffee and food!

We started off well with a gift of ‘Γιαννιώτικα βανίλιας’ (vanilla butter biscuits) and ‘Πιπερόπιτα’ (pepper pie), from the family of our Greek ESO team member, Apos, when we left Corinth. These were gratefully received and kept the team going for a few days!

We also have a number of coffee making options and paraphernalia in the containers, with the kettle on a near constant boil. The first few hours of each shift see many coffees consumed, while productivity ramps up!

Meals are provided on the ship every 6 hours. This means at breakfast time for one shift, the other shift are eating their evening meal. The 5am breakfast meal is eagerly awaited on the night shift (we try not to think so much about how many eggs we are consuming!) whilst the day shift looks forward to a 5pm feast. We are well fed and treated to Fajita Friday and Steak Saturday.

In between times there are biscuits, chocolate and snacks which emerge periodically, often from the snack drawer in the Science container!

Sophie Green

Images courtesy of ATsilligiannis@ECORD/IODP and SGreen@ECORD/IODP

Core Flow

After the cores arrive on deck (as described in Dave’s drilling blog), they are greeted by a squad of expectant Scientists. Offshore, we measure ephemeral properties from whole cores and samples taken from the core catchers, and store the cores in refrigerated containers called “reefers”. These data will help inform the sampling plan when the cores are split at the Bremen Core Repository early next year.

The first samples are taken on the curation table, located on the drilling deck. After the cores have been cut into sections, the Geochemists take samples from the cleanly cut ends for later measurement of methane concentration. We also have a handheld penetrometer device which is used to give an idea of the stiffness of the material.

The core then starts its journey down the street of containerised laboratories on the back deck. First stop is the curation container. Here, core measurements are taken and recorded – what was the drilled length, what was the length of recovered core, date, time and unique core section number. Samples from the core catchers are also taken to be analysed for microfossils and sedimentology. Further samples are taken on some cores to extract pore water When extracted the water is taken to the Geochemistry container for preliminary measurements (of pH, alkalinity, salinity and ammonium) and preservation for future use.

The next stop is the Multi Sensor Core Logger (MSCL) container. Here physical properties of the whole round cores are measured through the plastic liners. The cores are placed on a track and run through sensors to measure density, p-wave velocity, electrical resistivity, magnetic susceptibility and natural gamma radiation. We can use these data, alongside the other preliminary measurements, to understand how environments change as we move down and hole, and back in time.

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Finally the cores make it to the Science Office! In here the Sedimentologist on shift will examine both the core catcher samples and what they can see through the liners. Although the liners are clear, the view can be obscured by mud, and many features will not be visible until we get to Bremen next year and split the cores. The Micropaleontologists also sit in this space and use microscopes to identify microfossils which can give us an idea on the age of the sediments and the environment in which they formed. Also in this container are the Co-Chief Scientists, Lisa and Donna, who work on integrating existing data with our new cores and trying to understand the changes we see, using the various streams of evidence from all these measurements.

The cores finally come to rest in the reefers. At the end of the offshore phase of Expedition 381 they’ll travel on to the IODP Bremen Core Repository, MARUM Germany, to be met by the whole Science Party at the end of January, where the cores will be split and the detailed analyses undertaken.

Sophie Green

Images courtesy of CMiller@ECORD_IODP; SSauer@ECORD_IODP; DSmith@ECORD_IODP and ELeBer@ECORD_IODP

Shifts and Crossovers

Time at sea is precious, so data collection and analysis on research ships happens continuously, 24 hours a day, 7 days a week. The science party and ESO staff work 12-hour shifts, from midnight to noon (the night shift) and noon to midnight (the day shift).  Both shifts have some daylight and a sunrise or sunset, and both have been spectacular here in the Gulf of Corinth [see Wildlife blog]!.

With this schedule, it can be challenging for people on each shift stay informed on what the other shift has seen and learned and thus ensure that onboard efforts continue seamlessly from one shift to another.  To help with this, we hold ~15- to 20-minute-long crossover meetings at each shift change so that the departing shift can pass on updates to the arriving shift.  Meeting space for our team of scientists is limited; we either squeeze into the Science container (quiet, but a little stuffy) or meet outside (scenic and breezy, but a little loud!).  To compare and synthesize preliminary results in more detail, we also plan to have weekly science meetings in the ship’s conference room. We held our first science meeting on Halloween, and it was fun and informative to catch up on what everyone was finding and how it all fit together!

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Donna Shillington

How do we drill?

Thanks to Dave Smith, the ESO Operations Superintendent on-board for this look at drilling……..

Drilling and coring on a floating platform riding up and down on the swell of the sea and tides is a complex process involving winches, cables, hydraulics, compressed air and a lot of control systems.  A full explanation would be too long for a blog, so I won’t cover heave compensation, suffice to say the drill string stays stationary and the drilling derrick and ship ride up and down around it!

Our hardworking drilling team from Fugro are split into two 12 hour shifts, each shift comprises of a Driller, 2 Assistant Drillers, 2 Coring Specialists, and 2 Roughnecks. These teams are supported by a Back Deck Supervisor, Technical Drilling expert and Party Chief.

 

 

Our Fugro team, from top left: Ronnie; Piet; Max (driller); Geoff (driller); Jay, Tom and Zander; Marvin, Tom and Jesse; Matt R and Marlon; Gilbert, Roland and Matt C.

The drill string has reached the seabed a core barrel is lowered inside the drill string and lands in a special pipe at the base called a BHA (Bottom Hole Assembly). The type of coring tool used depends on the type of geology we expect to encounter underneath the seabed.

The subsurface geology comes in many forms, soft muds, sands, to hard rock and everything in between.  At the location of our first hole, there are soft clays at the seabed. To core this type of material, a hollow tube with a clear plastic liner inside is pushed into the ground ahead of the main drill bit using water pressure pumped from the surface. When the core barrel has been extended as far as it will go, up to 3m, it is then pulled out of the ground and back up the drill string with a wire to where the scientists are eager to get their hands on it. This method is called Piston Coring. The Driller then drills the main drill string to the depth that the core barrel had been pushed into the ground and the whole process starts again, that’s a lot of 3m core runs to get to 750m below the seabed!

 

 

From top left: The push corer tool; sending the push corer down the hole; Main drill bit; two images of work on the drill floor, and extracting a core liner from the core barrel.

However, as we progress down the hole the sediments can get much harder, either due to a change in rock type or due to compression by the weight of the 860m of sea and several hundred metres of clay above it. If it gets too hard to piston core, we use a different coring method. Rotary coring is where a complete triple wall coring assembly is lowered and locked into the BHA at the bottom of the drill string. The main drill string is then rotated and the ground beneath is cut with a diamond drill bit. The core travels up the core barrel as the bit cuts downwards.

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On the left we have Martin “Bat” Barnett (Back Deck Supervisor) and Tony Halliday (Technical Lead) – yes they do go to sea!!

The drill teams have to be experts in many different operations to make what sounds like a simple operation work safely, smoothly and efficiently. These skills include operating the drilling derrick, semi-automated pipe crane and handler that feeds the drill pipe to the and from the drill derrick, the Iron roughneck that tightens and loosens the drill pipe at each 9m connection, maintaining hydraulic and mechanical and control systems, welding, working at height in the rooster box, (the platform that sits on top of the drill pipe). Consuming copious amounts of coffee and biscuits are also a pre-requisite!

BriningTheCoringToolToTheRoosterBox

This image shows bringing the coring tool up to the rooster box on the drilling derrick. The main image at the top of the page shows a rotary coring bit with core catcher.

All images courtesy of DSmith@ECORD_IODP

What happens on Halloween……

October 31st and a spooky night shift on the Fugro Synergy. The cold wind howling past our containers got us in the mood for some Halloween fun on the back deck.

With limited resources we came up with a variety of container decorations, fancy dress, balloon art and ‘trick or treating’! We are using a geotechnical sampling tool called the FUGRO SEADEVIL on this project and it turns out that Seadevils’ are Angler fish……which inspired some of our fancy dress and decorations!

We also had our first science meeting on board to discuss what we’ve been recovering so far. …..mainly mud!

Images courtesy of DShillington@ECORD_IODP and MPhillips@ECORD_IODP

The wonderful world of pore water!

Why would anyone care about the water inside sediment at the bottom of the ocean? Well, I am glad you asked! Ocean sediment records the Earth’s climate history. Like reading a book backwards, the deeper you drill into ocean sediment the farther back in time you go. This is because small matter (scientists call them particulates) falls inside ocean water, and over time, accumulates on the seafloor. These particles can be many different things, such as stuff coming off land inside rivers, the bodies of tiny sea creatures, etc. As more new particulates bury old, some change and some do not.

 

Many of these changes are caused by bacteria eating buried dead organic matter. Pore water records this by keeping the products of these reactions. By studying this water, we know what type of reactions occurred and what type of material used to be in the sediment before it was changed.

Clint Miller

Images: Main image shows porewater being extracted by squeezer (Courtesy of ELeBer@ECORD_IODP). Inset images show Clint hard at work and Luzie Schnieders (ESO Geochemist) working at the squeezer (Courtesy of ELeBer@ECORD_IODP). The final image was supplied by Clint Miller and show how rhizones can collect pore water in softer sediments – this image is not from this expedition and is shown as an example of methodology only.