RICE – Roosevelt Island Climate Evolution Project - Deep ice Core

Roosevelt Island Climate Evolution – RICE Project

The potential for rapid deglaciation of West Antarctica remains a primary uncertainty in the Intergovernmental Panel on Climate Change (IPCC) predictions for 21st Century sea level rise. The recent and unpredicted collapse of multiple ice shelves and rapid acceleration of discharge of Antarctic ice suggests that dynamical responses to warming play a more significant role than is currently understood and captured in coupled climate-ice sheet models. Such models can be improved and validated by replicating known past changes. The RICE Project is an international partnership seeking to understand past, present, and future changes of the Ross Ice Shelf, a major drainage pathway of the West Antarctic Ice Sheet. The ANDRILL programme showed, that about 5 to 3 million years ago, the last time when atmospheric carbon dioxide (CO2) concentration and temperatures were similar to those predicted for the end of the 21st Century, the Ross Ice Shelf disintegrated multiple times, initiating the collapse of West Antarctica. However, no high resolution data exist from this time period. To determine the rate of change, RICE aims to provide an annually resolved ice core record for the past 20,000 years and beyond, when global temperatures increased by 6 deg C to preindustrial temperatures, global sea level rose by ~120 m, and the Ross Ice Shelf grounding line retreated over 1,000 km. Most of the Ross Ice Shelf retreat occurred when global sea level had already reached modern levels. For this reason, the precise correlation between increasing air and ocean temperatures, and the velocity and characteristics of the ice shelf retreat, provides a unique opportunity to determine accurately the sensitivity of the Ross Ice Shelf to warming.

In 2011/2012 the deep ice core was drilled using the newly built New Zealand intermediate ice core drilling system. The drilling system is based on the Danish Hans Tausen drill and features a range of technological improvements and new design aspects. Parts of the drilling system were tested twice in Greenland as part of the Danish led NEEM project and fully commissioned for the first time at Roosevelt Island. The drill performed exceptionally well, the average run length averaged between 1.2 and 1.7m and yielded high quality core. Some preliminary core logging included electric conductivity measurements, visual logging, and density measurements. The firn – ice transition was reached at 53m depth below surface, which promises a high resolution gas record. The drill hole was reamed to 65m depth, and the achieved drill depth was 130m below surface.

The firn – ice transition at 53m depth was shallower than expected and promises for an exceptionally high resolution gas record. The core will be processed by the international science community in August 2012 in the NZ Ice Core Research Facility at GNS Science in Lower Hutt, Wellington,NZ.