Geology and geophysical facilities

A major theme of geological and geophysical research in Antarctica is determining how the ice sheet responded to natural climate changes in the past, in order to reduce uncertainty in predictions of future climate and sea level change. This information is important for informing Government strategy for mitigating against these risks.

Using its dynamic positioning system, RRS Sir David Attenborough is able to hold its position accurately – even during rough seas – allowing effective sampling to take place. She will be capable of supporting and deploying a range of geological and geophysical equipment.

Sediment coring

Undisturbed sea-floor sediments can reveal the history of the Antarctic continent. Sampled from the ocean floor or from beneath ice shelves, these sediments can be taken back to the lab to analyse and aid investigations into ice-shelf thinning and retreat, sedimentary processes and oceanic circulation.

Collecting and analysing sediments cores gathered from ships and through the ice helps to provide a more complete picture of past ice sheet behaviour. The RRS Sir David Attenborough has a variety of instruments that allow researchers to do this.

For example, the ship can handle a 40.6m OSIL giant piston corer, which fits in standard shipping containers. This corer can recover sediment cores from the seafloor containing detailed records going back hundreds of thousands, or even a few million, years.

OSIL Giant Piston Corer aboard R/V Kaimei. Image courtesy of JAMSTEC.

Cores can also be collected in locations underneath floating ice shelves using hot-water drilling technology, giving researchers access to the seafloor even in places where the ocean is permanently covered by ice.

The RRS Sir David Attenborough also features a 12-core Oktopus MC12/100 multi-corer. The multi-corer collects 60 cm of sediment, with an undisturbed surface, which can be sampled in detail. Using this technology, researchers can study parameters such as particle size, organic carbon content, microfossil assemblages, stable isotopes, trace metal contents, biomarkers and accumulation rate.

A multi-sensor core logging scientific container can be placed on board to open directly into the ship’s wet lab. This means that non-destructive analyses of the cores can be conducted onboard the ship before they are sampled.

Oktopus Mega Multi Corer
Oktopus Mega Multi Corer packed away

Magnetometer

Towed magnetometers are frequently deployed in the ocean during geoscience research cruises and are central to many geophysical studies. They are used to produce a map of magnetic lineations, which contain a record of the rates and directions of sea-floor spreading.

Magnetometer data is the most important type of data for reconstructing the motions of tectonic plates – they played an important role in the widespread acceptance of plate tectonic theory in the 1960s.

The RRS Sir David Attenborough is equipped with a state-of-the-art towed Overhauser magnetometer for use on geoscience cruises.

BAS geophysicist Tom Jordan prepares a magnetometer for deployment on the RRS James Clark Ross
BAS geophysicist Tom Jordan prepares a magnetometer for deployment on the RRS James Clark Ross

Gravity meter

The gravity meter is installed close to the centre of motion of the vessel and operates continuously, detecting small differences in the Earth’s gravity field that indicate variations in the geology beneath the sea floor. Gravity data are typically combined with seismic and magnetic observations to determine the locations and extent of igneous intrusions or the thickness of sediment accumulations.

Seismic facilities

Seismic profiling systems are an effective way of studying the structure and composition of the sediments and rocks below the sea floor. Acoustic signals from an air gun can penetrate layers of sediment and bedrock. These signals are reflected to varying degrees by layers of different materials and are picked up by an array of sensitive hydrophones towed behind the ship. This data is used to produce a profile of the seabed rocks rather than just the surface.

RRS Sir David Attenborough is equipped with advanced generator-injected airguns as well as air compressors to facilitate research into the geology of the seafloor.

Air gun array being deployed on the RRS James Clark Ross
Air gun array being deployed on the RRS James Clark Ross

 

Seafloor sediments and the landforms on the Antarctic continental shelf contain records of past climate, ecosystems and physical processes. These records are essential for understanding the dynamics of ice flow and how this interacts with the ocean surrounding Antarctica. Polar research ships allow researchers to collect samples and data from remote locations using state-of-the-art sonar tools and specialised drills and corers. The resulting data include detailed maps of the seafloor that can shed light on past glacial processes and climatic changes.

The giant piston corer that can be deployed from RRS Sir David Attenborough will be able to recover sediment cores over 40m deep. This allows for high-resolution data going back roughly half a million years, or more coarse-resolution information going back as long as 2.7 million years.

Sediment cores collected from the seafloor can yield accurate records of past ecosystems and the way in which large-scale oceanic currents have changed over decades to millions of years. They also contain invaluable data about past climates. Reconstructing how the Antarctic ice sheet and ecosystems have changed in the past, particularly during periods of warming, is important for predicting future responses to climate change and its contribution to future sea-level rise. This data can also be used to test current models of future changes, by showing whether models can accurately reproduce what the sediment core records show.

Autonomous underwater vehicles and remotely operated vehicles  (ROVs) allow researchers access to study sites that are too dangerous or difficult to reach for people, such as glacier calving faces and the undersides of ice shelves. These regions are key to understanding the changes taking place in the Antarctic ice sheet, which could have global climatic repercussions. These vehicles can carry high-resolution sonar system and some ROVs can also collect push cores and vibrocores.