Antarctic Scientific Drilling Program (ANDRILL) Highlight

Scientific rationale and main questions

Drilling at Coulman High will investigate:

• The evolution of the West Antarctic Ice Sheet in a period of high greenhouse gas levels;
• The Antarctic environment in warm greenhouse periods;
• Controls on Oligocene and Miocene climate and cryosphere; and
• Tectonic processes within the West Antarctic Rift System.

Operational challenges

Logistic and operational challenges exist at the Coulman High sites, and work is underway to modify existing technology and develop new approaches to accommodate these challenges. Access to the seafloor requires melting through 250 metres of ice shelf using the ANDRILL hot water drill, which has previously been used to maintain an open hole through 80 metres of ice. The amount of lateral deflection that ANDRILL’s sea riser can accommodate is limited by water column thickness and amount of ice-shelf movement. These parameters constrain drilling depth to a maximum of ~500 m at the Coulman High sites if existing technology were utilised.

Site survey data during the 2010-2011 field season

An extensive field program in Antarctica during the austral summer of 2010-2011 paved the way for future drilling. This included finding a safe route to the site from McMurdo Station, assessing the ocean currents beneath the ice shelf and the tides at the site, determining seafloor composition and conditions and improving the seismic velocity control at the drill sites. Prior activities included airborne radar profiling to measure ice-shelf thickness and to search for nascent cracking and crevassing.

The survey team also measured lateral and vertical movements of the ice shelf in the vicinity of Coulman High with GPS and evaluated site meteorology. The seismic experiment acquired reflection and refraction data to improve the velocity-depth model used to interpret drilling targets from existing marine seismic reflection data. The oceanographic data were used to model the behaviour of the drilling riser in response to the observed tides and currents. All of these data collection efforts and modelling results will be used to finalise the drill site selection and determine the most robust drilling strategy for the project.

The data collected this season will be utilised to develop a full drilling proposal through the ANDRILL SMO. A new international partnership for drilling in 2012-14 is currently being developed.

Find out more information on the Coulman High Project from a dedicated page on the ANDRILL Website.