Day 4 First core

Coring tube is lowered onto frame

Frame is rotated into the water

Corer is lowered into the water

First segment of core is cut off

Success! The first core of the cruise

Sediment samples are taken for analysis

All the gazillions of tiny planktonic creatures that live in the ocean will eventually die and get eaten, dissolve or sink down to the sea floor. While the food chain and who eats what is important to a marine biologist, the paleooceanographer is after those critters that die and settle on the bottom. Gradually over geological time scales of thousands of years, layer upon layer builds up of these dead creatures and other particles like wind-blown dust or silt from nearby rivers. Each layer that settles on the sea bed contains a signature of the environmental conditions at the time when the creatures buried within were still alive. If left undisturbed in the depths of the ocean the sediment buildup acts like growth rings on a tree - the chemical and biological signals in the deposited sediments encode the climatic history of our planet, and this what the paleo team has come to the Southern Ocean to study.

A corer is used to retrieve the sediment layering. It is essentially a long metal tube that is lined with plastic lining on the inside and a a massive weight (about 1 metric ton) attached to the top end. When the bottom end, which is open, hits the seafloor the coring tube will punch through the sediments driven by the weight from above. Inside the plastic liner it traps layer upon layer of past climatic records. The photos show some of the deployment procedure. First the empty core is laid out horizontally on deck and then winched onto a frame. Then the top end of the tube is connected to the weight and all segments are securely fastened together. Then the frame cradling the entire corer is rotated into the vertical on the side of the ship. From there the winch takes over and grabs the corer (now weighing well over a ton) and lowers it into the water. At the first site it's 600m deep, so at a rate of  1m/s the corer reaches the seafloor in about 10 minutes. Then the coring tube sinks into the sea floor mud driven by the huge weight. The corer settles and the winch cable goes slack - a tense moment. Will the shutter at the bottom of the coring tube shut properly or will all the mud spill out of the bottom? Has the corer entered the sea bed vertically, or could it have hit a rock and bent out of shape?

When the corer is winched up again, all looks fine. The shutter closed proberly, the whole tube is straight and undamaged and its side are smeared with sediments - this is a good sign. The core now contains hundreds of kilos of layered sediments, or to the rest of us: "mud"! Back on the ship the core is laid out on the deck and the plastic lining is pushed out of the metal outer tube. In regular intervals the plastic core is cut off and brought to the lab. Now it's time to take first swabs of the glorious smelly mud. The team can't wait to put the samples under the microscope and look which species of microscopic critters died at the time that particular layer of sediment was deposited on the sea bed. What looks like ordinary mud will be full of clues about the past history of the oceans.

The various species of micro-organisms change with environmental factors such as water temperature, and amongst the layers of mud the team hopes to find clues of when colder or warmer ocean currents were prevalent at this site. From a first estimate we think that the core taken today can reveal that sort of information up to 50,000 years into the past, maybe even further back in time. Only by knowing how the oceans changed in the past we can hope to understand how they will change in the furture. At a time when these changes, accelerated by human activity, happen so rapidly these clues from the past are priceless. Even if they come from smelly mud and dead bits of plankton.

This was a truly exciting day of science on the James Clark Ross. The crew was fantastic in deploying the equipment safely and the science team gained lots and lots of data which will keep us busy analysing for a long time.

Did I mention there was a bar on board?? Well, Cheers!