Antarctic weathering and hydrologic cycling through the Paleogene greenhouse to icehouse transition (IODP Expedition 318, Wilkes Land)

Over the past 65 million years of geologic time, Earth's climate has changed dramatically--transitioning from a world with warm oceans and limited polar glaciation to a world with cold polar regions and large continental ice sheets. This long-term change in global climate is known as the 'Greenhouse' to 'Icehouse' transition and primarily occurred during the Eocene and Oligocene geological epochs (between 55 and 23 million years ago). Study of this remarkable episode of ancient climate change can provide valuable information for understanding the mechanisms that precipitated this shift, as well as insight into the operation of different Earth system processes in the past. Further knowledge of these processes, involving the global carbon cycle and different climate feedback mechanisms, can be used to inform future predictions of climate change resulting from anthropogenic greenhouse gas emissions to the atmosphere.

In an effort to gain further information on high-latitude climate conditions during the 'Greenhouse' to 'Icehouse' transition, the Integrated Ocean Drilling Program (IODP) recently cored marine sediments on the Antarctic margin off the Wilkes Land coast (directly south of Australia). The drillcores were recovered using a ship-based drilling platform and provide a window into Eocene and Oligocene climate history of the Antarctic coast and marginal seas. The proposed study is focused on clay mineral assemblages preserved in cores obtained from the Wilkes Land coast. Since clay minerals are a primary sedimentary weathering product shed from the terrestrial environment, variation in the types of clay mineral present throughout cores will provide important information on changes in the prevailing weathering regime. Specifically, clay minerals can be used to determine the timing of the switch from a chemical weathering regime (under warm, humid conditions) to physical weathering regime (influenced by glacial activity) during the Eocene-Oligocene time interval. Through collaborative work, the clay mineral records will be integrated with other climate proxy records currently being developed using a variety of approaches. The new Antarctic climate reconstructions that result from this research will provide critical high-latitude climate information that can be used to: (1) determine the nature of Antarctic climate conditions during peak Eocene warmth and during the onset of Oligocene glaciation, and (2) assess links between global climate change and atmospheric pCO2 variability through the 'Greenhouse' to 'Icehouse' transition.

Who will benefit from this research?

The results of this study will be of direct benefit to a wide user community, including:

(1) the UK earth science community, and specifically the UK academic community engaged in IODP-related research,
(2) the wider palaeoclimate and climate science communities,
(3) national government environmental and climate change departments, such as the Committee on Climate Change (CCC) in the UK,
(4) international bodies tasked with compiling climate data and assessing the impacts of climate change, such as the Intergovernmental Panel on Climate Change (IPCC), and
(5) the general public.

How will they benefit from this research?

The IPCC currently predicts that global temperatures will rise between 1.1 and 6.4 degrees C in the coming century. This divergence of possible temperature responses corresponds to a similar range in the severity of the societal and ecological impacts of climate change. In order to better predict and manage greenhouse warming, past intervals of Earth history that were subject to large swings in climate and high-amplitude variability in atmospheric carbon dioxide concentrations (pCO2) can be used as an important source of baseline information. Specifically, geological datasets, such as the Antarctic palaeoclimate records in the proposed project, can be used in conjunction with palaeo-pCO2 proxy records to determine the sensitivity of global climate to pCO2 change under a range of boundary conditions. In turn, this information can be used to test climate models with respect to operation of key Earth system processes, carbon cycle feedbacks, etc. These models, after testing and refinement to accurately simulate climate response under a range of boundary conditions, will then be able to better predict the rate and magnitude of future climate change.

Through examination of high-latitude climate dynamics during the 'Greenhouse' to 'Icehouse' transition, the results of this study will provide critical insight on the drivers, amplifiers and feedbacks in the natural climate system, and these findings will be of interest to all of the above-mentioned end users. Use of these new datasets to inform, test, and refine computer models will be of great importance for improving model predictions of human-induced climate change. The insight and knowledge obtained from past intervals of global climate change will also merit consideration within future IPCC reports and, therefore, will be important for policy decisions regarding future climate change.

What will be done to ensure that designated end users benefit from this research?

In order to realize the full potential impact of the results of the proposed study, efforts will be made to:

(1) collaborate and share information will researchers engaged in post-cruise analysis of Exp. 318 drillcores,

(2) publish all results from the study in a timely and efficient manner, in both widely read (i.e., high impact factor) and specialist journals,

(3) use results to initiate new studies with other researchers using computer models to investigate past climate change,

(4) directly communicate important and novel science results to the media with the assistance of institutional press officers at the University of Southampton,

(5) increase engagement with the general public by delivering general interest talks on Antarctic field research and scientific drilling, Earth's climate evolution, and the geological perspective on future climate change.